ALBERT

Notizen: The reintroduction of Sphagnum fragments has been found to be a promising method for restoring mire vegetation in a cutaway peatland. Although it is known that moisture controls Sphagnum photosynthesis, information concerning the sensitivity of carbon dynamics on water-level variation is still scarce. In a 4-year field experiment, we studied the carbon dynamics of reintroduced Sphagnum angustifolium material in a restored (rewetted) cutaway peatland. Cutaway peatland restored by Sphagnum reintroduction showed high sensitivity to variation in water level. Water level controlled both photosynthesis and respiration. Gross photosynthesis (PG) had a unimodal response to water-level variation with optimum level at −12 cm. The range of water level for high PG (above 60% of the maximum light-saturated PG) was between 22 and 1 cm below soil surface. Water level had a dual effect on total respiration. When the water level was below soil surface, peat respiration increased rapidly along the lowering water level until the respiration rate started to slow down at approximately −30 cm. Contrary to peat respiration, the response of Sphagnum respiration to water-level variation resembled that of photosynthesis with an optimum at −12 cm. In optimal conditions, Sphagnum reintroduction turned the cutaway site from carbon source to a sink of 23 g C/m2 per season (mid-May to the end of September). In dry conditions, lowered photosynthesis together with the higher peat respiration led to a net loss of 56 g C/m2. Although the water level above the optimum amplitude restricted CO2 fixation, a decrease in peat respiration led to a positive CO2 balance of 9 g C/m2.

Notizen: Restoration status of forest rehabilitation areas can be assessed by comparing their ecosystem characteristics with those of a reference system, most often what is considered the natural climax vegetation. However, comprehensive measurements needed for a traditional vegetation description are often hard or impractical in complex (sub)tropical ecosystems. Therefore, an alternative approach is the identification of simple indicators of ecosystem integrity. The use of such indicators can speed up the availability of resource inventories and thus contribute to the accelerated implementation of successful rehabilitation practices. Thermal buffer capacity (TBC) of ecosystems has been previously proposed as an overall indicator of ecosystem integrity. In this article, sequential surface-temperature measurements are proposed as a method for TBC assessment of different land-use types. Surface temperatures of seven land units in central Tigray (northern Ethiopia), each with a uniform land-use type (degraded and bushy grazing land, enriched and non-enriched rehabilitation area, and forest), were measured with a hand-held infrared thermometer in the rainy and the dry season. Surface-temperature models were derived by means of quadratic regression. Cross-correlation functions were calculated for all possible pairs of land-unit time-series data. Instantaneous heat-up rates, average TBC, and accumulated heat load were calculated. Repeated-measures analysis of variance was used to test the effect of aspect and protection status on TBC. Kruskal–Wallis one-way analysis of variance by ranks for small samples was used to test the significance of differences in heat-up rates and heat load among land-use groups. Time lags between land-unit surface temperatures are caused by differences in aspect rather than land-use type. Protection status and aspect have a significant effect on the average TBC. Results clearly demonstrate a differentiation between protected (low heat-up rate) and non-protected areas (high heat-up rate). Overall ranking suggests that the remnant forest has the highest TBC of all surveyed land-use types, followed by the enriched protected area. Results of this study show that TBC quickly responds to area closure and can therefore be used to monitor the development of protected areas. It is strongly recommended that a detailed monitoring strategy for protected areas on the basis of this technology be devised, validated, and finally transferred to the local communities.

Notizen: An ecological functional assessment (EFA) was used on 10 southwest Costa Rica sites representing a chronosequence of formerly pastured lands to undisturbed tropical wet forest. Ecological functional assessment is a tool designed to assess wetland functions in the United States that was adapted to upland forests. Models to indicate characteristic soil hydrologic features and soil structure and aboveground spatial structure of habitat were used to examine the degree to which selected sites within the chronosequence approach the undisturbed condition of the natural forest. An index of the functional model for the maintenance of characteristic soil hydrologic features (such as infiltration, bulk density, etc.) showed that the 20-year-old secondary forest was at approximately 60% of the condition of the undisturbed sites, whereas active pasture was evaluated at approximately 20% of the reference undisturbed forest; 4- and 10-year-old sites were intermediate. The spatial structure of habitat model showed that 20-year-old secondary forest was approximately 50% of reference forest, whereas active pasture was approximately 10% of the condition of undisturbed forest; 4-year-old sites were evaluated at approximately 20% and 10-year-old sites at approximately 60% of the reference state. Overall the functional assessment process indicated that degraded tropical wet forest sites have recovered almost 60% of their functional qualities 10 years following pasture abandonment. These results indicate that EFA can be a useful technique for monitoring restoration programs in the tropics.

Notizen: We evaluated changes in ecosystem function in semiarid Stipa tenacissima L. steppes along a degradation gradient in southeast Spain. We used soil surface indicators to obtain surrogates of ecosystem function (resistance to erosion, infiltration, and nutrient cycling) and related these values to the main abiotic and biotic characteristics of the experimental sites. When ranked in an ordered sequence, the trajectory of these indicators showed abrupt changes, providing empirical evidence of discontinuities in ecosystem function along the degradation gradient evaluated. Surrogates of resistance to erosion showed nonlinear relationships with variables defining the spatial structure of patches, the area covered by sprouting shrubs, and species richness. The latter two variables were significantly related to surrogates of nutrient cycling and infiltration. Our results suggest that sprouting shrubs are playing a key role in improving ecosystem function and composition in degraded S. tenacissima steppes. The implications of our results for the optimization of restoration procedures in semiarid degraded steppes are discussed.

Notizen: Restoration of salt marsh ecosystems is an important concern in the eastern United States to mitigate damage caused by industrial development. Little attention has been directed to the mycorrhizal influence on plantings of salt marsh species to stabilize estuarine sediments and establish cover. In our study, seedlings of two salt marsh grasses, Spartina alterniflora and Spartina cynosuroides, were grown in soil with a commercial, mixed species inoculum of arbuscular mycorrhizal fungi. Plants were grown in experimental “ebb and flow” boxes, simulating three levels of tidal inundation, to which two levels of applied phosphorus (P) and two levels of salinity were imposed. After 2.5 months, S. alterniflora was poorly colonized by arbuscular mycorrhizae, developing only fungal hyphae and no arbuscules, but S. cynosuroides became moderately colonized. Mycorrhizal inoculation marginally improved growth and P and nitrogen (N) content of both plant species at low levels of P supply but significantly increased tillering in both plant species. This factor could be beneficial in enhancing ground cover during restoration procedures. Greater P availability increased the mycorrhizal status of S. cynosuroides and improved P nutrition of both plant species, despite a reduction in the root-to-shoot ratio. Increasing salinity reduced mycorrhizal colonization of S. alterniflora but not of S. cynosuroides. Growth and nutrient content of S. alterniflora was improved at higher levels of salinity, but only increased nutrient content in S. cynosuroides. Increased duration of tidal inundation decreased plant growth in both species, but tissue P and N concentrations were highest with the longest time of inundation in both species.

Notizen: As monitoring plans for the restoration of Pinus ponderosa forests in the southwestern United States evolve toward examining multifactor ecosystem responses to ecological restoration, designing efficient sampling procedures for understory vegetation will become increasingly important. The objective of this study was to compare understory composition and diversity among thin/burn and control treatments in a P. ponderosa restoration, while simultaneously examining the effects of sampling design and multivariate analyses on which conclusions were based. Using multi-response permutation procedures (MRPP), we tested the null hypothesis of no difference in understory species composition among treatments using different data matrices (e.g., frequency and cover) for two different sampling methods. Treatment differences were subtle and were detected by an intensive 50, 1-m2 subplot sampling method for all data matrices but were not detected by a less intensive point-intercept sampling method for any matrix. Sampling methods examined in this study controlled results of multivariate analyses more than the data matrices used to summarize data generated by a sampling method. We partitioned data into plant life form and native/exotic species categories for MRPP, and this partitioning isolated plant groups most responsible for treatment differences. We also examined the effects of number of 1-m2 subplots sampled on mean-species-richness/m2 estimates and found that estimates based on 10 subplots and based on 50 subplots were highly correlated (r = 0.99). Species–area curves indicated that the 50, 1-m2 subplot sampling method detected the common species of sites but failed to detect the majority of rare species. Additional sampling-design studies are needed to develop single sampling designs that produce multifactor data on plant composition, diversity, and spatial patterns amenable to multivariate analyses as part of monitoring plans of vegetation responses to ecological restoration.

Notizen: The relative abundances of Chenopodiaceae shrubs are different from the seed composition in the original seed mix when sown on mine waste material in semiarid regions of Western Australia. Experiments were therefore undertaken to determine what species interactions are responsible for shifts in relative abundance after seeding. The growth parameters of five members of the Chenopodiaceae were used to determine intra- and interspecific density-dependent interactions. Dominant and subordinant species were paired and grown in pots at differing densities. The growth parameters measured were height, root, and shoot biomass. Of the five species chosen for this study, Maireana georgei (golden bluebush) and Enchylaena tomentosa (ruby saltbush) do not establish well on mine site areas. These were sensitive to density in monoculture, as well as in the presence of both Atriplex bunburyana (silver saltbush) and Atriplex codonocarpa (flat-topped saltbush). Although Maireana brevifolia (small leaf bluebush) does establish successfully on mine sites when sown, it showed the same negative reaction when grown in monoculture and in a two-species mixture. Atriplex bunburyana and A. codonocarpa, in contrast, are dominant species and reacted differently when grown with increasing numbers of the target species (M. georgei, M. brevifolia, and E. tomentosa). Atriplex bunburyana did not exhibit any decreases in growth when grown in competition with up to four plants of the target species. However, A. codonocarpa did react adversely to the presence of the target species. It is thought that the resulting plant community organization reflects the original seed mixture, which is usually sown at a high density. Yet, this study has shown that the differing intra- and interspecific density responses of these chenopod species provide an indication of the resulting community organization. To maximize diversity and to prevent dominance by highly competitive species, such as A. bunburyana, it is important to take density-dependent effects into account during the restoration planning stage.

Notizen: Plant species richness in rural landscapes of northern Europe has been positively influenced by traditional management for millennia. Owing to abandonment of these practices, the number of species-rich semi-natural grasslands has decreased, and remaining habitats suffer from deterioration, fragmentation, and plant species decline. To prevent further extinctions, restoration efforts have increased during the last decades, by reintroducing grazing in former semi-natural grasslands. To assess the ecological factors that might influence the outcome of such restorations, we made a survey of semi-natural grasslands in Sweden that have been restored during the last decade. We investigated how plant species richness, species density, species composition, and abundance of 10 species that are indicators of grazing are affected by (1) the size of the restored site, (2) the time between abandonment of grazing and restoration, (3) the time elapsed since restoration, and (4) the abundance of trees and shrubs at the restored site. Only two factors, abundance of trees and shrubs and time since restoration, were positively associated with total species richness and species density per meter square at restored sites. Variation in species composition among restored sites was not related to any of the investigated factors. Species composition was relatively similar among sites, except in mesic/wet grasslands. The investigated factors had small effects on the abundance of the grazing-indicator species. Only Campanula rotundifolia responded to restoration with increasing abundance and may thus be a suitable indicator of improved habitat quality. In conclusion, positive effects on species richness may appear relatively soon after restoration, but rare, short-lived species are still absent. Therefore, remnant populations in surrounding areas may be important in fully recreating former species richness and composition.

Notizen: Ground and pelletized Wollastonite (Wo; CaSiO3) was added to a 50-m reach of an anthropogenically acidified stream within the Hubbard Brook Experimental Forest, New Hampshire, to evaluate its buffering and restoration potential. The Wo was highly effective in raising the pH, acid-neutralizing capacity (ANC), dissolved inorganic carbon (DIC), and Ca2+ concentrations of the stream water, but during the short duration of the experiment had no discernable effect on the stream biota. After initial, spike-like fluctuations in pH and concentrations of ANC, DIC, and Ca2+, the relatively slow dissolution rates of the Wo dampened extreme concentrations and contributed to relatively long-lasting (4 months) amelioration of streamwater acidity. Changes in concentrations of Ca2+, dissolved Si, ANC, and DIC were inversely related to streamflow. After several high, stream-discharge events, concentrations quickly and consistently returned to pre-event conditions.

Notizen: The potential of Cephalophyllum inaequale was investigated for use in initiating ecosystem restoration in degraded landscapes of Namaqualand, South Africa. Cephalophyllum inaequale, a perennial shrub, is a member of the succulent Mesembryanthemaceae family, typical of the Succulent Karoo Biome and in particular of the Namaqualand area. A bioclimatic envelope was modeled to establish the area in which this species might feasibly be used. The regional bioclimatic potential for C. inaequale proved to be extensive, covering approximately 17,500 km2. An examination of the functional role of C. inaequale showed it to facilitate early seedling survival in this community. A nearest-neighbor study found no evidence of interspecific competition between C. inaequale and its dominant co-occurring species, possibly due to vertical stratification of rooting structures. Cephalophyllum inaequale significantly reduced wind speed and soil erosion. Experiments to test the feasibility of propagating, reintroducing, and establishing this species showed that it easily germinates from seed, and transplanted cuttings have a high survival rate. This study demonstrates that C. inaequale has potential for use in initiating the restoration of degraded lands in South Africa.

Notizen: The cloud forests of Mexico have been degraded and severely fragmented, and urgently require restoration. However, progress with restoration has been constrained by a lack of information concerning the seedling ecology of native tree species. An experiment was therefore conducted to assess the influence of different environmental factors on the seedling survival and growth of four native tree species (Fagus grandifolia var. mexicana, Carpinus caroliniana, Symplocos coccinea, and Quercus acutifolia). The seedlings were established on three sites, in two contrasting environments: inside forest fragments and on adjacent agricultural land. Highly significant differences were recorded in seedling survival and growth among sites, environments, species, and interactions between these factors. Highest survival was recorded for Quercus, which uniquely among the four species displayed the same survival percentage inside and outside the forest. Survival of the other species was higher inside the forest. In contrast, growth rates of all four species were higher outside the forest. The most important cause of mortality outside the forest was desiccation, although significant seedling predation was also observed on two sites. Results indicate that all four species can be established successfully both within forest fragments and in neighboring agricultural areas, emphasizing the scope for forest restoration. However, the interactions observed between species, sites, and environments highlight the importance of accurate species–site matching if optimum rates of growth and survival are to be obtained. Quercus spp. have great potential for establishment on agricultural sites.

Notizen: The mature oak (Quercus liaotungensis Koidz) forests in the Dongling mountains of northern China have become degraded in recent years because regeneration has been limited. To determine whether or not seedling establishment of the oak is seed limited, microsite limited, or predator limited and to determine whether seedling establishment is affected by ground cover, we conducted field experiments during a mast year and investigated the fate of seeds and the soil seed bank dynamics of the oak. A large acorn crop (128.8 acorns/m2) was observed in the study period, and the peak density of acorns on the forest floor reached 46.5 acorns/m2, suggesting that tree recruitment was not seed limited. Acorns in the soil seed bank were mainly lost through decay (principally after fungal attack), consumption in situ, and removal by animals. Predation (including consumption in situ and removal) accounted for 86.4% of acorn loss and was therefore likely to have been the most important factor influencing seed dynamics. More than 70% of acorns were found to have germinated, but no established seedling was observed on the forest floor. Using cages to exclude predators, it was estimated that 87% of acorns germinated and 49% became established as seedlings, indicating that the acorns on the forest floor could emerge and grow in the absence of predators. We conclude that the regeneration of the tree population is limited by predators rather than by the availability of microsites. The presence of ground cover increased the germination rate and increased the chance of seed survival in the early stage of the experiment, but at the end of the investigation, no established seedling was found in the quadrats both with and without ground cover, possibly because of high density of animal predators. On the basis of these results, we suggest that selective tree felling will increase the coverage of the herbaceous layer, which can further decrease the population density of the rodents, and thereby improve the regeneration of oak trees.

Notizen: Reach-scale stream restorations are becoming a common approach to repair degraded streams, but the effectiveness of these projects is rarely evaluated or reported. We surveyed governmental, private, and nonprofit organizations in the state of Indiana to determine the frequency and nature of reach-scale stream restorations in this midwestern U.S. state. For 10 attempted restorations in Indiana, questionnaires and on-site assessments were used to better evaluate current designs for restoring stream ecosystems. At each restoration site, habitat and water quality were evaluated in restored and unrestored reaches. Our surveys identified commonalities across all restorations, including the type of restoration, project goals, structures installed, and level of monitoring conducted. In general, most restorations were described as stream-relocation projects that combined riparian and in-stream enhancements. Fewer than half of the restorations conducted pre- or post-restoration monitoring, and most monitoring involved evaluations of riparian vegetation rather than aquatic variables. On-site assessments revealed that restored reaches had significantly lower stream widths and greater depths than did upstream unrestored reaches, but riparian canopy cover often was lower in restored than in unrestored reaches. This study provides basic information on midwestern restoration strategies, which is needed to identify strengths and weaknesses in current practices and to better inform future stream restorations.

Notizen: Abstract We examined the 7-year effects of three restoration treatments on leaf physiology and insect-resistance characteristics of pre-settlement age ponderosa pines (Pinus ponderosa Dougl. ex Laws.) at the Gus Pearson Natural Area (GPNA) in northern Arizona. Restoration treatments were: (1) thinned in 1993 to approximate pre-Euro-American settlement stand structure, (2) thinned plus prescribed burned in 1994 and 1998, and (3) untreated control. Tree physiological and insect-resistance characteristics were measured in year 2000, 7 years after thinning, using the same procedures as an earlier study performed in 1996. Consistent with the 1996 results, pre-dawn water potential in 2000 was consistently lower in the control than both thinned treatments. Both thinned treatments continued to have increased foliar nitrogen concentration in leaves 7 years after treatment. However lower leaf nitrogen concentration in the thinned and burned compared with the thinned treatment suggests lower nitrogen availability to trees in repeatedly burned plots. Analysis of leaf gas exchange characteristics and carbon isotope content (δ13C) suggests continued stimulation of photosynthesis by both thinning treatments. Differences among treatments in resin volume, a measure of bark beetle resistance, depended on season of measurement. Trees in both thinning treatments continued to have increased leaf toughness, a measure of resistance to insect folivores. Our results show that many beneficial effects of restoration treatments on carbon, water, and nitrogen relations and insect-resistance characteristics of pre-settlement ponderosa pines continue to be expressed 7 years after treatment at the GPNA.

Notizen: Establishment of native plant populations on disturbed roadsides was investigated at Bryce Canyon National Park (BCNP) in relation to several revegetation and seedbed preparation techniques. In 1994, the BCNP Rim Road (2,683–2,770 m elevation) was reconstructed resulting in a 23.8-ha roadside disturbance. Revegetation comparisons included the influence of fertilizer on plant establishment and development, the success of indigenous versus commercial seed, seedling response to microsites, methods of erosion control, and shrub transplant growth and survival. Plant density, cover, and biomass were measured 1, 2, and 4 years after revegetation implementation (1995–1998). Seeded native grass cover and density were the highest on plots fertilized with nitrogen and phosphorus, but by the fourth growing season, differences between fertilized and unfertilized plots were minimal. Fertilizers may facilitate more rapid establishment of seeded grasses following disturbance, increasing soil cover and soil stability on steep and unstable slopes. However the benefit of increased soil nutrients favored few of the desired species resulting in lower species richness over time compared to unfertilized sites. Elymus trachycaulus (slender wheatgrass) plants raised from indigenous seed had higher density and cover than those from a commercial seed source 2 and 4 years after sowing. Indigenous materials may exhibit slow establishment immediately following seeding, but they will likely persist during extreme climatic conditions such as cold temperatures and relatively short growing seasons. Seeded grasses established better near stones and logs than on adjacent open microsites, suggesting that a roughened seedbed created before seeding can significantly enhance plant establishment. After two growing seasons, total grass cover between various erosion-control treatments was similar indicating that a variety of erosion reduction techniques can be utilized to reduce erosion. Finally shrub transplants showed minimal differential response to fertilizers, water-absorbing gels, and soil type. Simply planting and watering transplants was sufficient for the greatest plant survival and growth.

Notizen: We compared four types of 30-year-old forest stands growing on spoil of opencast oil shale mines in Estonia. The stand types were: (1) natural stands formed by spontaneous succession, and plantations of (2) Pinus sylvestris (Scots pine), (3) Betula pendula (silver birch), and (4) Alnus glutinosa (European black alder). In all stands we measured properties of the tree layer (species richness, stand density, and volume of growing stock), understory (density and species richness of shrubs and tree saplings), and ground vegetation (aboveground biomass, species richness, and species diversity). The tree layer was most diverse though sparse in the natural stands. Understory species richness per 100-m2 plot was highest in the natural stand, but total stand richness was equal in the natural and alder stands, which were higher than the birch and pine stands. The understory sapling density was lower than 50 saplings/100 m2 in the plantations, while it varied between 50 and 180 saplings/100 m2 in the natural stands. Growing stock volume was the least in natural stands and greatest in birch stands. The aboveground biomass of ground vegetation was highest in alder stands and lowest in the pine stands. We can conclude that spontaneous succession promotes establishment of diverse vegetation. In plantations the establishment of diverse ground vegetation depends on planted tree species.

Notizen: This study examined factors affecting germination, survival, and growth of the grass trees Xanthorrhoea gracilis and X. preissii on newly rehabilitated bauxite mine pits in the jarrah forest of southwestern Australia. Grazing by kangaroos (Macropus fuliginosus) was the major factor in reducing survival and growth of both species during the first 2 years. Provision of artificial grazing protection increased survival and growth (plant mass) of both species by 3-fold. Grazing by native vertebrates has not previously been identified as affecting mine restoration in Western Australia. Initial germination rates from sown seeds of X. preissii at eight replicate sites ranged from 25 to 64% with a mean of 42%. Corresponding figures for X. gracilis were 5–42% with a mean of 17%. Germination of X. gracilis was greater on heavier, moister soils, but X. preissii germinated better on sandier soils. High levels of initial germination did not ensure high survival. Plants of both species grew bigger and survived better on the lighter, sandy soils. Xanthorrhoea seedlings located in the depressions created by the ripping process grew larger than seedlings on the slopes of the riplines. The presence of plants of other species did not have a significant effect on survival. However, these plants facilitated the growth of both species when artificial grazing protection was unavailable. Plants of other species reduced the growth rates of Xanthorrhoea seedlings where artificial grazing protection was provided. Artificial shade by itself had no significant effect on growth of either species. In rehabilitated bauxite mines in the jarrah forest, the provision of grazing protection is recommended to ensure successful establishment and early survival of Xanthorrhoea spp.

Notizen: To assess the potential for enhancing an existing stand of native perennial grasses on a California Coast Range Grassland site, we experimentally manipulated the seasonal timing and presence of grazing for 3 years (1994 through 1996) and of autumn burning for 2 years (1994 and 1995) and measured species cover for 6 years (1993 through 1998). We subjected the species matrix to classification (TWINSPAN) and ordination (CCA) and tested the ordination site scores as well as diversity indices with linear mixed effects models. Four distinct plant community groups emerged from the classification. Two of these were dominated by annual grasses and two by perennial grasses. No treatment effects were observed on diversity. For composition, temporal and spatial random effects were important mixed effects model parameters, as was the fixed effect covariate, pre-treatment CCA site score, indicating the importance of random environmental variation and initial starting conditions. Incorporation of these random effects and initial condition terms made for more powerful tests of the fixed effects, grazing season, and burning. We found no significant burning effects. Grazing removal imparted a shift in plant community from more annual-dominated toward more perennial-dominated vegetation. Individual perennial grass species responded differently according to genus and species. Nassella spp. increased gradually over time regardless of grazing treatment. Nassella pulchra (purple needlegrass) increase was greatest under spring grazing and N. lepida (foothill needlegrass) was greatest with grazing removal. Danthonia californica (California oatgrass) had little response over time under seasonal grazing treatments, but increased with grazing removal. Under relatively mesic weather conditions it appears that grazing removal from Coast Range Grasslands with existing native perennial grass populations can increase their cover. However if N. pulchra is the sole existing population, spring season-restricted grazing should be equally effective at enhancing cover of the native grass species.

Notizen: A combination of air-photo interpretation, field data, and Geographic Information System (GIS) analysis was used to map riparian areas that are likely to provide wood and shade to small- and medium-sized streams and where, conversely, restoration might be most beneficial. The analysis encompassed all salmonid-bearing waters of the Nooksack River basin, in northwest Washington State, plus small tributaries that were thought to contribute wood or effective shading. The size and composition of each riparian stand was examined to determine whether trees were large enough to contribute logs that would form pools in the adjacent channel, with pool-forming size of wood a function of channel width. Riparian stands were classified according to whether they passed this pool-forming test. Model results were an exact match to actual conditions in 69% of field-verified stands. A large proportion (74%) of the stands failing the test in reaches of anadromous fish use were in agricultural areas. Passing stands typically had high shade levels, because both stream shade and effective large woody debris size are a function of the size of the trees relative to the size of the stream. The GIS layer of passing and failing riparian stands can be combined with layers depicting property ownership, threatened fish distribution, and other information to objectively prioritize riparian restoration locations and strategies.

Notizen: The benefits of wetlands are now widely appreciated. Less widely known is that historically many wetlands were drained to help control malaria and other deadly diseases. This essay's general theme is that there are pros and cons to restoration or creation of wetlands. The specific theme is that mosquitoes pose practical and theoretical problems. In particular, abundant mosquitoes should not be regarded as an after-the-fact surprising side effect but rather, abundant mosquitoes should be viewed as a primary and foreseeable effect of providing habitat suitable for them. Yet our funding mechanisms and educational institutions often fail properly to address the reality that restoring or creating wetlands has a downside.

Notizen: The recruitment of native seedlings is often reduced in areas where the invasive Amur honeysuckle (Lonicera maackii) is abundant. To address this recruitment problem, we evaluated the effectiveness of L. maackii eradication methods and restoration efforts using seedlings of six native tree species planted within eradication and unmanipulated (control) plots. Two eradication methods using glyphosate herbicide were evaluated: cut and paint and stem injection with an EZ-Ject lance. Lonicera maackii density and biomass as well as microenvironmental characteristics were measured to study their effects on seedling growth and survivorship. Mean biomass of Amur honeysuckle was 361 ± 69 kg/ha, and density was 21,380 ± 3,171 plants/ha. Both eradication treatments were effective in killing L. maackii (≥ 94%). The injection treatment was most effective on large L. maackii individuals (〉1.5 cm diameter), was 43% faster to apply than cutting and painting and less fatiguing for the operator, decreased operator exposure to herbicide, and minimized impact to nontarget vegetation. Deer browse tree protectors were used on half of the seedlings, but did not affect survivorship or growth. After 3 years, survival of native seedlings was significantly less where L. maackii was left intact (32 ± 3%) compared with the eradication plots (p 〈 0.002). Seedling survival was significantly different between cut (51 ± 3%) and injected (45 ± 3%) plots. Species had different final percent survival and rates of mortality. Species survival differed greatly by species (in descending order): Fraxinus pennsylvanica 〉 Quercus muehlenbergii ≥ Prunus serotina≥ Juglans nigra 〉 Cercis canadensis 〉 Cornus florida. Survivorship and growth of native seedlings was affected by a severe first-year drought and by site location. One site exhibited greater spring soil moisture, pH, percent open canopy, and had greater survivorship relative to the other site (55 ± 2 vs. 30 ± 2%). Overall, both L. maackii eradication methods were successful, but restorationists should be aware of the potential for differential survivorship of native seedlings depending on species identity and microenvironmental conditions.

Notizen: Several eastern states are considering the restoration of free-ranging elk populations via translocation from western populations. Optimal habitat immediately surrounding release sites has been found to enhance elk reintroduction success in western states. Little information exists, however, to aid eastern managers in identifying release sites with the highest chance of restoration success. We monitored the movements of 415 translocated elk released at three sites in southeastern Kentucky to identify landscape characteristics that enhance release-site fidelity. The distance elk moved after release differed among sites (F2,322 = 4.63, p = 0.01), age classes (F2,322 = 4.37, p = 0.01), and time intervals (F2,322 = 40.74, p 〈 0.001). At 6 and 12 months post-release, adults (15.81 ± 17.32 and 16.38 ± 20.29) and yearlings (13.91 ± 16.44 and 14.61 ± 21.11) moved farther than calves (8.06 ± 14.03 and 9.37 ± 14.40). The release site with the highest fidelity was privately owned, 15% open, and had the highest amount of edge compared with the other release sites. The two remaining sites contained large amounts of expansive openland or forest cover with lower amounts of edge. Additionally, both sites were publicly owned and experienced a higher degree of human-generated disturbance compared with the site to which elk were most faithful. When selecting release sites, managers should avoid areas dominated by a single cover type with little interspersion of other habitats. Rather, areas with high levels of open-forest edge (approximately 5.0 km/km2) and limited-human disturbance will likely enhance release-site fidelity and promote restoration success.

Notizen: Limestone quarries are spread over the Mediterranean Basin and have a strong environmental impact on the landscape, causing vegetation losses and soil losses. A reclamation project was conducted in a limestone quarry, situated in Arrábida Natural Park (southwest Portugal), that is dominated by mediterranean vegetation. Revegetation was conducted using three evergreen sclerophyllous shrub species (Ceratonia siliqua, Olea europaea, and Pistacia lentiscus), and new techniques were assayed to improve plant water status and nutrient status during the first phases after plantation. A water-holding polymer (gel), fertilizer, and mycorrhiza inoculum were applied in a factorial experiment in a randomized complete block design. The success of these techniques was evaluated during 1.5 years, through monitoring of growth and ecophysiology of plants. Plant survival was high, the lowest values (95%) being recorded in C. siliqua. There were species-specific responses to the treatments applied. Ceratonia siliqua showed the highest growth rates and was the only species with growth stimulated by fertilizer application. However, the application of fertilizer induced changes in leaf characteristics of the other two species, increasing chlorophyll and nitrogen contents. Mycorrhiza inoculum had no effect on plant response. The addition of the water-holding polymer induced higher midday plant water potentials in C. siliqua, O. europaea, and P. lentiscus, but in the latter two species the simultaneous addition of gel and fertilizer induced the lowest water potentials. The addition of fertilizer and gel is recommended in future revegetation programs but not the combination of both when revegetating with O. europaea and P. lentiscus. The results of this experiment indicate that the use of these mediterranean species, adapted to nutrient and water stress, can circumvent harsh conditions of the quarry.

Notizen: Structural attributes of the C4, perennial bunchgrass Schizachyrium scoparium in restored prairies may be affected by the time since restoration. One hundred plants each in 8-, 17-, and 23-year-old restored prairies and a native Texas Blackland prairie were assessed for the presence/absence and diameter of a hollow crown (i.e., dead center portion), degree of fragmentation, plant height, and tiller density. Structural attributes of S. scoparium plants were generally (1) different between recent (8 years) and older (17 and 23 years) restored prairies (2) similar between the 17- and 23-year-old restored prairies, and (3) more similar between the 8- and 17-year restored prairies and the native, remnant prairie than between the 23-year restored prairie and the native prairie. Plants were shorter in restored prairies, regardless of time since restoration, than in the native prairie. Mean basal area of plants was 80–163% greater in the 17- and 23-year restored prairies compared with the native and 8-year restored prairies. Percentage of hollow crowns and fragmentation was smallest in the 8-year restored prairie, largest in the 17- and 23-year restored prairies, and intermediate in the native prairie. Tiller density exhibited inverse second-order polynomial decreases with increasing plant basal area for all prairies. In contrast to tiller density, diameter of hollow crowns increased logarithmically with increasing plant basal area. Structural attributes of S. scoparium in restored prairies changed predictably with age, despite growing in different communities.

Notizen: There is growing interest in the addition of carbon (C) as sucrose or sawdust to the soil as a tool to reduce plant-available nitrogen (N) and alter competitive interactions among species. The hypothesis that C addition changes N availability and thereby changes competitive dynamics between natives and exotics was tested in a California grassland that had experienced N enrichment. Sawdust (1.2 kg/m) was added to plots containing various combinations of three native perennial bunchgrasses, exotic perennial grasses, and exotic annual grasses. Sawdust addition resulted in higher microbial biomass N, lower rates of net N mineralization and net nitrification, and higher concentrations of extractable soil ammonium in the soil. In the first year sawdust addition decreased the degree to which exotic annuals competitively suppressed the seedlings of Nassella pulchra and, to a lesser extent, Festuca rubra, both native grasses. However there was no evidence of reduced growth of exotic grasses in sawdust-amended plots. Sawdust addition did not influence interactions between the natives and exotic perennial grasses. In the second year, however, sawdust addition did not affect the interactions between the natives and either group of exotic grasses. In fact, the native perennial grasses that survived the first year of competition with annual grasses significantly reduced the aboveground productivity of annual grasses even without sawdust addition. These results suggest that the addition of sawdust as a tool in the restoration of native species in our system provided no significant benefit to natives over a 2-year period.

Notizen: Concepts and models from complex systems theory are introduced to help expand the approaches to quantify restoration success in ecology. Main points are illustrated using case studies. These include (1) recovery and restoration trajectories may be complex (nonlinear, unpredictable, and leading to multiple attractors), and thus knowledge of well-known model trajectories from complex systems theory may be useful; (2) modeling may be inevitable, as complete and long-term observation of recovery pathways are rarely possible; (3) holistic views (e.g., community level as opposed to population-level) may be necessary to understand governing processes in restoration and recovery.

Notizen: Recent efforts to clear invasive plants from the fynbos of South Africa forces managers to think about how N2-fixing invasives have altered ecosystem processes and the implications of these changes for community development. This study investigated the changes in nitrogen (N) cycling regimes in fynbos with the invasion of Acacia saligna, the effects of clear-cutting acacia stands on soil microclimate and N cycling, and how altered N resources affected the growth of a weedy grass species. Litterfall, litter quality, soil nutrient pools, and ion exchange resin (IER)-available soil N were measured in uninvaded fynbos, intact acacia, and cleared acacia stands. In addition, a bioassay experiment was used to ascertain whether the changes in soil nutrient availability associated with acacia would enhance the success of a weedy grass species. Acacia plots had greater amounts of litterfall, which had higher concentrations of N. This led to larger quantities of organic matter, total N, and IER-available N in the soil. Clearing acacia stands caused changes in soil moisture and temperature, but did not result in differences in IER-available N. The alteration of N availability by acacias was shown to increase growth rates of the weedy grass Ehrharta calycina, suggesting that secondary invasions by nitrophilous weedy species may occur after clearing N2-fixing alien species in the fynbos. It is suggested that managers use controlled burns, the addition of mulch, and the addition of fynbos seed after clearing to lower the levels of available N in the soil and initiate the return of native vegetation.

Notizen: Ponderosa pine forest restoration consists of thinning trees and reintroducing prescribed fire to reduce unnaturally high tree densities and fuel loads to restore ecosystem structure and function. A current issue in ponderosa pine restoration is what to do with the large quantity of slash that is created from thinning dense forest stands. Slash piling burning is currently the preferred method of slash removal because it allows land managers to burn large quantities of slash in a more controlled environment in comparison with broadcast burning slash. However burning slash piles is known to have adverse effects such as soil sterilization and exotic species establishment. This study investigated the effects of slash pile burning on soil biotic and chemical variables and early herbaceous succession on burned slash pile areas. Slash piles were created following tree thinning in two adjacent approximately 20-ha ponderosa pine (Pinus ponderosa) restoration treatments in the Coconino National Forest near Flagstaff, Arizona. We selected 30 burned slash pile areas and sampled across a gradient of the burned piles for arbuscular mycorrhizal (AM) propagule densities, the soil seed bank, and soil chemical properties. In addition, we established five 1-m2 plots in each burned pile to quantify the effect of living soil (AM inoculum) and seeding amendments on early herbaceous succession in burned slash pile areas. The five treatments consisted of a control (no treatment), living soil (AM inoculum) amendment, sterilized soil (no AM inoculum) amendment, seed amendment, and a seed/soil (AM inoculum) amendment. Slash pile burning nearly eliminated populations of viable seeds and AM propagules and altered soil chemical properties. Amending scars with native seeds increased the cover of native forbs and grasses. Furthermore adding both seed and living soil more than doubled total native plant cover and decreased ruderal and exotic plant cover. These results indicate that seed/soil amendments that increase native forbs and grasses may enhance the rate of succession in burned slash pile areas by allowing these species to outcompete exotic and ruderal species also establishing at the site through natural regeneration.

Notizen: We show that the presence of sufficiently significant switching costs, which are increasing in the degree of product differentiation, generates an equilibrium configuration with maximal differentiation within the framework of a Hotelling model with linear transportation costs. The equilibrium with maximal differentiation offers a formalization of the idea that competing firms have noncooperative incentives to establish maximal switching cost barriers. The equilibrium incentives for commitments to high switching costs can be explained with poaching profits, which are increasing in the switching costs. Ex ante competition for market shares in period 1 is unable to eliminate these poaching profits.

Notizen: We analyze competition between two private television channels that derive their profits from advertising receipts. These profits are shown to be proportional to total population advertising attendance. The channels play a sequential game in which they first select their profiles (program mixes) and then their advertising ratios. We show that these ratios play the same role as prices in usual horizontal differentiation models. We prove that whenever ads' interruptions are costly for viewers the program mixes of the channels never converge but that the niche strategies are less effective and that the channel “profiles” are closer as advertising aversion becomes stronger.

Notizen: All-units discounts in retail contracts refer to discounts that lower a retailer's wholesale price on every unit purchased when the retailer's purchases equal or exceed some quantity threshold. These discounts pose a challenge to economic theory because it is difficult to understand why a manufacturer ever would charge less for a larger order if its intentions were benign. In this paper, we show that all-units discounts may profitably arise absent any exclusionary motive. All-units discounts eliminate double marginalization in a complete information setting, and they extract more profit than would a menu of two-part tariffs in the standard incomplete information setting with two types of buyers. All-units discounts may improve or may reduce welfare (relative to menus of two-part tariffs) depending on demand parameters.

Notizen: This paper is concerned with communication within a team of players trying to coordinate in response to information dispersed among them. The problem is nontrivial because they cannot communicate all information instantaneously but have to send longer or shorter sequences of messages, using coarse codes. We focus on the design of these codes and show that members may gain compatibility advantages by using identical codes and that this can support the existence of several, more or less efficient, symmetric equilibria. Asymmetric equilibria may exist only if coordination across different sets of members is of sufficiently different importance. The results are consistent with the stylized fact that firms differ even within industries and that coordination between divisions is harder than coordination inside divisions.

Notizen: We analyze optimal patent design when innovators can rely on secrecy to protect their innovations. Secrecy has no fixed term but does not preclude accidental disclosure nor independent creation by other inventors. We derive the optimal scope of the rights conferred to such second inventors, showing that if the patent life is set optimally, second inventors should be allowed to patent and to exclude first inventors who have relied on secrecy. We then identify conditions under which it is socially desirable to increase patent life as much as is necessary to induce first inventors to patent. The circumstances in which it is preferable that they rely on secrecy seem rather limited.

Notizen: Recent losses and fragmentation of tallgrass prairie habitat to agriculture and urban development have led to corresponding declines in diversity and abundance of plants and birds associated with such habitat. Mowing and burning are alternative management strategies for restoring and rejuvenating prairies in fragmented landscapes, but their specific, comparative effects are the subjects of ongoing evaluation. We compared the responses of plant and bird communities on four sets of mowed, burned, and untreated sites of small (3–10 ha), fragmented tallgrass prairies at the DeSoto National Wildlife Refuge (DNWR), Iowa, U.S.A., during May–July in 1998 and 1999. Species richness and diversity of plants, resident grassland birds, and communities of birds associated with grassland edges (edge species) were independent of treatment. Although not affecting species richness and diversity in plant communities, mowed sites ranked lower in total plant coverage and total forb coverage than burned sites or untreated sites. In contrast, untreated sites had more coverage by shrubs, suggesting that mowing and burning did retard shrub encroachment. Overall, abundance and diversity of plants and birds were generally insensitive to management strategies. Small, fragmented sites of rare habitat may not respond in the short term to management treatments and may not be capable of supporting highly diverse communities, no matter how intensively manipulated. It is more probable that diversity of native prairie communities can be enhanced and restored only through long-term efforts, acquisition of large land units capable of supporting stable populations, and deliberate reintroduction of species of high conservation value.

Notizen: Forest openings, also known as glades, arise through a variety of mechanisms including disturbance (fire and blow downs) and local variation in soil or bedrock geology. They are common in many forest types and are often dominated by locally rare herbaceous species. Prescribed burning is increasingly used as a management approach for maintaining glades although little is known about the effects of fire on these habitats. Of particular concern is the potential for nutrient loss during and after fire because glades are often characterized by nutrient-poor soils. We quantitated nutrient losses through combustion and leaching for glade and adjacent forest habitats subjected to a prescribed burn. Our findings suggest that spring burns do not result in appreciable loss of nutrient capital from glades in comparison with those observed in the surrounding forest. Fire resulted in a substantial loss of litter mass (37%) in the forest but no measurable loss in the glade. Nitrogen losses through combustion were significant in the forest and were equivalent to 4.5 years of atmospheric inputs. Fire significantly increased soil nitrate pools in forest but not in glade plots. No detectable increases in nitrogen, phosphorus, or base cation leaching were observed in either forest or glade habitats within 4 months after the burn. These findings suggest that plant and microbial nutrient uptake rapidly reestablish control over leaching losses when burns are conducted at the start of the growing season. Biotic retention minimizes fire impacts on nutrient loss from the ecosystem.

Notizen: Since the early 1990s, restoration techniques have been developed for milled and cutover peatlands in eastern Canada. These techniques are based on the active reintroduction of peatland plant diaspores, blocking drainage, and the use of straw mulch to improve surface conditions. This study examines the effectiveness of using shallow (20 cm deep) basins of various widths to improve the success of current peatland restoration techniques. It comprises three different experiments, each spanning three or four growing seasons and combining both small-scale manual and large-scale mechanized plant reintroductions. Cover data recorded in two of the experiments were regressed against a series of environmental factors to determine how Sphagnum establishment success was related to abiotic variables such as moisture, water ponding, surface roughness, and mulch cover. Results of these experiments demonstrate that shallow basins were generally effective at promoting Sphagnum establishment and that this effect extends beyond the positive impact that basins have on hydrological conditions. Basins of various widths were equally successful. Soil-moisture content (linear positive effect) and duration and severity of flooding events (quadratic effect) were shown to be determinant of plant recovery. Other factors such as the density of straw cover (positive effect) and surface roughness (negative effect) were also instrumental in explaining local variation in Sphagnum cover. Plant cover after three and four growing seasons averaged 20–25% in mechanical reintroductions and 40–60% in manual reintroductions, demonstrating the overall effectiveness of the restoration techniques used.

Notizen: The moth Cactoblastis cactorum (Berg), the poster child of weed biological control in Australia, has recently invaded the United States and threatens native cacti. Concern is greatest for the endangered semaphore cactus, Opuntia corallicola, of which only two known populations exist in the wild. We made three separate outplantings of O. corallicola, designed to bolster the number of extant cacti and to test the effectiveness of three different treatments to protect the cacti from Cactoblastis. In one outplanting, we tested the associational susceptibility hypothesis and found that cacti planted more than 20 m away from the common prickly pear cactus, Opuntia stricta, which act as a reservoir of Cactoblastis, were just as frequently attacked and killed by Cactoblastis as cacti planted within 5 m. In addition, Cactoblastis attack was greater in the shade than in the sun. In the second outplanting, we minimized the attack from Cactoblastis by using protective cages planted at least 500 m from O. stricta in areas not inhabited by cacti. Cages attracted the attention of local animals, which destroyed the cages and trampled the cacti inside to death. Crown rot caused high mortality in this outplanting. In the third outplanting, again conducted at least 500 m away from O. stricta, fertilization did not reduce crown rot mortality. We suggest that increasing populations of O. corallicola in Florida, by means of outplantings, will remain a challenge because of death from Cactoblastis when planted in areas where cacti normally grow and because of death from crown rot in areas where they do not. Because Cactoblastis is moving rapidly northward and westward and has already reached Charleston, South Carolina, rare cacti in the rest of the U.S. Southeast may be in danger. Eventually, many cactus species in the U.S. South, Southwest, and Mexico will likely be threatened by this moth.

Notizen: Some of the most species-rich areas and highest concentrations of threatened and endangered species in the southeastern United States are found in wet savanna and flatwood longleaf pine (Pinus palustris Mill.) communities. Where intensive forestry practices have eliminated much of the natural understory of the longleaf ecosystem, the potential for reestablishment through a seed bank may present a valuable restoration opportunity. Longleaf pine sites converted to loblolly pine plantations and non-disturbed longleaf sites on the Coastal Plain of North Carolina were examined for seed bank presence and diversity. Conducting vegetation surveys and examining the seed bank using the seedling emergence technique allowed for verification of the seed bank presence, as well as evaluation of the quality of the seed bank on disturbed longleaf pine sites. Forty-three species and over 1,000 individuals germinated, and the seed banks of both the disturbed and non-disturbed stand types contained species not noted in the vegetation survey. Although many of these species were considered weedy and typical of disturbance, numerous taxa were indicative of stable longleaf pine communities. This study confirms both the presence and quality of seed banks in highly disturbed former longleaf pine sites, suggesting that the seed bank may be an important tool in restoration efforts.

Notizen: Ant communities have been widely used as indicators of minesite rehabilitation in Australia and are beginning to play a similar role in other parts of the world. Here we examine ant communities on rehabilitated ash dams associated with a coal-fired power station on the highveld of South Africa, to improve our understanding of ecosystem development on these substrates. Ants were sampled using pitfall traps at 11 ash-dam sites, ranging from unrehabilitated to 9-year-old rehabilitated sites, as well as two adjacent natural grassland sites. Sampling was conducted on 12 occasions from March 1997 to January 1999. Forty-nine ant species from 19 genera were recorded during the study. Site species richness was positively correlated with rehabilitation age, ranging from 10 to 25 at ash-dam sites, compared with 28 and 34 at the two natural grassland sites. There was a humped relationship between total ant abundance and rehabilitation age, with abundance peaking after 5–7 years at levels far higher than those at natural sites. Ordination analysis showed clear separation between ash-dam and natural sites along the first axis. The unrehabilitated ash-dam site was also separated from rehabilitated sites along the first axis. Sites of different rehabilitation age were separated along the second axis. Individual ant species showed clear successional patterns across the rehabilitation gradient. Although there was a clear successional trend for the development of ant communities on rehabilitated ash dams, this trend was not toward natural grassland. The lack of convergence toward ant communities of natural grasslands reflects the markedly different substrate and plant composition on ash dams and supports the widely held view that restoration of natural grassland communities is not a realistic goal of ash-dam rehabilitation. However, the development of species-rich ant communities, containing at least some late-successional species, indicates the potential for rehabilitated ash dams to support diverse and complex ecosystems.

Notizen: The restoration of inland salt-affected plant communities, including saltflat mixed prairie and playa lakes wetlands, has received little attention despite the importance of these communities for critical wildlife habitat. The salt-affected communities of Cheyenne Bottoms, located in central Kansas, are a crucial stopover site for migratory waterfowl and shorebirds. In 1998, The Nature Conservancy attempted to restore native plant communities to grazed and former cropland at Cheyenne Bottoms by reestablishing sheet flow across these disturbed areas. We collected vegetation cover data along permanent transects established in rangeland, former cropland, and in a shallow basin 3 years (1996–1998) before the hydrological changes and continued to collect vegetation data for 3 years (1999–2001) after the hydrological changes. Vegetation composition changes in response to the restored hydrology were subtle, but the average wetland index along the transects in the basin and the rangeland significantly declined. Significant decreases occurred in the cover of perennials and graminoids in both spring and fall species assemblages of the rangeland area. Changes in the former cropped areas were mixed, indicating the difficulty of restoring these disturbed plant communities to native plant assemblages within a few years.

Notizen: Little information exists about the establishment of native longleaf pine flatwoods species for use in restoration efforts and as buffers around natural areas in the southeastern United States. Composition of groundcover in these systems is dominated by perennial graminoid species. Vegetation in current buffers is generally non-native turfgrass that can escape into natural areas, often reducing establishment and survival of native species. Where management objectives involve actively restoring native groundcover or reducing the probability of invasion by these non-native turfgrasses, identification of native species and restoration methods is needed. We investigated seed germination and establishment of four species native to longleaf pine flatwoods in central Florida and one species native to the adjacent wetland communities. Paspalum setaceum, Panicum anceps, Eustachys petraea, and Eragrostis refracta were directly seeded, and P. distichum was planted as sprigs into three former P. notatum pastures. Irrigation, fertilization, weed control, and mowing treatments were assessed in terms of cover development of the sown species. Paspalum distichum developed the highest percent cover—over 80% in wet areas after 1 year. Mowing had mixed impacts depending on the species, and fertilization never significantly increased cover. Directly seeded species developed sparse cover (0–40%), probably as a result of drought conditions. However, E. petraea and E. refracta appeared more promising for use on rights-of-way when using high sowing rates. A second experiment conducted on a roadside included these two species and sprigged P. distichum. Both E. petraea and P. distichum developed more than 45% cover on the roadside. Establishment of these natives from seed or sprigs was significantly enhanced when site preparation effectively reduced the seedbank of other species present in the soil.

Notizen: Relatively intense burning has been suggested as a possible alternative to the restoration of pre-European settlement forest conditions and fire regime in mixed conifer forests, in contrast to thinning of trees and light prescribed burning. In 1993 a management-ignited fire in a dense, never-harvested forest in Grand Canyon National Park escaped prescription and burned with greater intensity and severity than anticipated. We sampled the burned site and an adjacent unburned site (270 ha each) 6 years after the fire to assess burn effects on tree structure (species composition, size and age distributions, regeneration, and snags), forest floor fuels, and coarse woody debris. Tree structure before fire-regime disruption (1879 CE) was reconstructed with dendroecological techniques. By 6 years after burn the fire reduced average tree density (331 trees/ha) and basal area (28.5 m2/ha) to levels similar to pre-European reference conditions (approximately 246 trees/ha and 28.5 m2/ha). Mortality was concentrated in fire-susceptible species, especially white fir, restoring dominance by fire-resistant ponderosa pine. Forest floor fuels were reduced, and regeneration by aspen and understory plants was vigorous. Densities of large snags and logs were high. However the fire also killed a high proportion of old-growth trees, especially aspen. Burning created more spatial variability in forest structure than was present before fire-regime disruption by killing many trees in some areas of the site but few in other areas. The intentional use of severe burning would be challenging to managers because of the increased risk of escaped fires, but the ecological outcome of this particular wildfire was not inconsistent with ecological restoration goals for this ecosystem type.

Notizen: The effects of sewage sludge, used to improve fertility of replaced soil, on vegetation were studied in limestone quarry restoration. Plant community growing in the first stages after sludge application was surveyed in six quarries of NE Spain. Areas with a mixture of sewage sludge and residual soil were compared to areas where the application consisted only of residual soil (a mixture of previous top soil and mine spoils). Sewage sludge was hypothesized to increase total biomass and cover, modifying species composition and delaying the early successional recover of the community. The results showed that both biomass and plant cover increased because of sewage sludge addition. The floristic composition was dominated by ruderal species that did not show any dependence on sewage sludge application. Convergence on similarity between sludge and control plots was not detected along a 5-year period. Although species richness was significantly lower in sludge plots, diversity and equitability indexes did not show differences between treatments. The results did not show differences in the proportion of non-native species. The proportion of legumes was lower in sludge plots. These results show that the plant communities resulting from the addition of sewage sludge to the soil used in limestone quarry restoration have more biomass and cover, but less number of species, and they do not show a clear trend to converge to those areas restored only with non-amended soil.

Notizen: The long-term effects (20–45 years) of reclamation treatments on plant succession are examined at two localities in Iceland that were fertilized and seeded from 1954 to 1979 with perennial grasses or annual grasses, or left untreated. The areas that underwent reclamation treatments had significantly higher total plant cover (7–100%) than the untreated control plots (〈5%), and floristic composition was usually significantly different between treated and untreated plots. Dwarf-shrubs (Calluna vulgaris and Empetrum nigrum), bryophytes, biological soil crust, grasses, and shrubs characterized the vegetation in the treated plots, but low-growing herbs that have negligible effects on the environment, such as Cardaminopsis petraea and Minuartia rubella, and grasses characterized the control plots. The seeded grass species had declined (〈10%, the perennials) or disappeared (the annuals) but acted as nurse species that facilitated the colonization of native plants. It seems that by seeding, some factors that limit plant colonization were overcome. Soil nutrients, vegetation cover, litter, and biological soil crust were greater in the treated areas than the control plots. This may have enhanced colonization through an increase in soil stability and fertility, increased availability of safe microsites, increased moisture, and the capture of wind-blown seeds. This study demonstrates the importance of looking at the long-term effects of reclamation treatments to understand their impact on vegetation succession.

Notizen: In semiarid Mediterranean areas, the widespread environmental impact caused by the construction of motorways, railways, and pipelines has created an increasing need for effective restoration. We examined the influence of slope characteristics on vegetation and water erosion on 71 motorway slopes in a semiarid Mediterranean region. Specifically, we studied the effect of slope angle, type (roadfill vs. roadcut) and aspect (north vs. south) on soil properties, vegetation cover, species richness, floristic composition, and water-caused erosion. Temporal dynamics of soil water content was monitored and related to the soil water potential in order to explain possible differences in vegetation cover between slope types. The main factors influencing vegetation on motorway slopes were the angle, type, and aspect of the slope. Vegetation was almost completely lacking on roadcuts with slopes greater than 45°. On gentler slopes, vegetation cover was 44–78% on roadfills but did not reach 10% on roadcuts, regardless of aspect. The main soil properties affected by the slope type and aspect were the organic matter content, soil available P, and water content. Rill erosion, gully erosion, and mass movement were all significantly higher on roadcuts than roadfills. A total of 308 spontaneous colonizers and seeded species were recorded. The type and aspect of the slope also controlled species composition. The short duration of available water in the soil with respect to soil water potential proved to be a limiting factor to plant colonization on roadcuts and south-facing slopes as well as the low soil fertility in the case of roadcuts. Our results underscore the difficulty of revegetating slopes with angles greater than 45°, where the probability of seeds moving downhill is high. Future efforts should focus on increasing the surface roughness or building terraces at regular intervals in order to reduce slope angle to less than 45° and favor seed trapping and germination. On gentler slopes, adjusting of seed mixes according to dominant species associated with each slope type and aspect should improve considerably the success of roadside revegetation.

Notizen: Induced mycorrhization of sweet birch (Betula lenta L.) by Pisolithus tinctorius (Pers.) Coker & Couch, as influenced by substrate fertility, was evaluated for its effects on seedling growth and physiology. Following a brief period in seed flats, seedlings were transplanted to mine spoil where they resided for 30 months, and three nutrition regimes were imposed throughout the study by application of differing nutrient solution concentrations. High fertility suppressed mycorrhizal formation by P. tinctorius but promoted that of other mycobionts. Pisolithus mycorrhization induced substantial aboveground and belowground growth as indicated by dimensions and mass for the former and mass and length for the latter but favoring root over shoot growth overall. Furthermore, these mycorrhizae were frequently able to compensate for the growth stimulation of higher nutrient additions. Measurements of xylem pressure potential and soil water potential indicated that water uptake was enhanced by P. tinctorius during simulated drought episodes of two durations and in subsequent recovery periods. Inoculated seedlings had higher foliar concentrations of critical nutrients, especially N, and lower concentrations of potentially phytotoxic metallic elements, particularly Mn, than uninoculated seedlings, although the latter response was absent in high fertility. Spoil analyses clearly revealed the influence of the nutrition regimes but also the effects of seedling uptake on substrate chemistry, and reinforced the findings of the foliar analysis concerning suppression of metal uptake by P. tinctorius. Collectively, these results suggest that P. tinctorius can provide sweet birch an array of physiological benefits that will permit this tree species to flourish on harsh substrates such as surface mine spoils without heavy application of chemical fertilizers.

Notizen: The surfgrass Phyllospadix torreyi is an abundant seagrass found on rocky exposed shores of the Pacific coast of North America. In southern California surfgrass populations are adversely affected by a range of natural events and anthropogenic activities. Few attempts have been made to develop restoration methods for surfgrass, and none have investigated the efficacy of using different life stages. We evaluated several techniques for restoration in intertidal and subtidal habitats using: (1) laboratory-reared seedlings transplanted to the field (2) sprigs (short lengths of rhizome containing a few shoots) transplanted from undisturbed populations, and (3) plugs (a cohesive clump of shoots and rhizomes) transplanted from undisturbed populations. We calculated the net change in the aerial coverage of surfgrass after 6 months, taking into account the recovery or additional losses from the donor population, and amount of effort involved in transplanting. Transplanted seedlings survived poorly and had minimal rhizome growth at both the intertidal and the subtidal sites, yet the individuals that did survive showed a 275% increase in leaf number. Survivorship of transplanted plugs was high in both habitats; however, physical disturbances to the donor populations exacerbated damage sustained at the time of collecting, yielding a substantial net loss in surfgrass. Sprigs transplanted to the subtidal had higher survivorship (71 versus 48%) and a greater increase in the aerial coverage of rhizome (86 versus 42%) than those transplanted to the intertidal. Of the three techniques, transplanted sprigs had the greatest overall increase in aerial coverage per unit effort, suggesting that this method may be the most effective approach for restoring P. torreyi.

Notizen: Few ecosystem restoration studies evaluate whether arthropods are important components of ecosystem recovery. We tested the hypothesis that ponderosa pine restoration treatments would increase adult butterfly species richness and abundance as a direct result of increased understory diversity and abundance. To examine mechanisms that potentially affect adult butterfly distribution, we quantified host plant frequency, nectar plant abundance, and insolation (light intensity) in restoration treatment and control forests. This study is unique, because this is the first invertebrate monitoring in ponderosa pine forest restoration treatments in the U.S. Southwest and also because these treatments are the first replicated ponderosa pine restoration treatments at a landscape scale. Three patterns emerged: (1) butterfly species richness and abundance were 2 and 3 times greater, respectively, in restoration treatment units than in paired control forests 1 year after treatment, and 1.5 and 3.5 times greater, respectively, 2 years after treatment, ordination of control and treatment sampling units using butterfly assemblages showed significant separation of control and restoration treatment units after restoration treatment; (2) host plant and nectar plant species richness showed little difference between treated and control forests even 2 years after treatment; and (3) insolation (light intensity) was significantly greater in treated forests after restoration. We suggest that changes in the butterfly assemblage may occur due to light intensity effects before plant community changes occur or can be detected. Butterfly assemblage differences will have additional cascading effects on the ecosystem as prey for higher trophic levels and through plant interactions including herbivory and pollination.

Notizen: Dunes, which account for 13% of the Ille et Vilaine north Brittany coast, France, were degraded by high tourist pressure, and they were restored from 1988 onward. Ten years after commencing work an assessment of the restoration was made on three dunes: Les Chevrets, L'Anse Du Guesclin, and Le Verger. Annual monitoring of the vegetation and dune morphology provided an opportunity to study the restoration process. The dune front, which is similar to a reference pioneer dune, lies in front of the mobile dune. The highest part of the dune is an advanced stage of mobile dune. The restoration of the fixed rear dune was accomplished neither in terms of vegetation composition nor in terms of species richness. The vegetation parameter study allows differentiation between the dune front, the dune summit, and the rear dune. The variation in species richness and floristic composition from one zone to another can be explained by abiotic factors such as salinity and the accretion of sand. The restoration was satisfactory in terms of the geomorphology. Marram grass is a good tool for restoring the topography, but it will take a very long time to restore the conservation value of the dune.

Notizen: In California's Mediterranean type grasslands, native perennial grasses such as Nassella pulchra are surrounded by introduced annual species and these annuals are thought to have displaced natives through much of their range. Amongst other invaders, two grasses Lolium multiflorum and Bromus hordeaceus, commonly dominate portions of the grassland with potential for N. pulchra restoration. We hypothesized that competitor species differences and small-scale gaps (150 cm2) could be important determinants of N. pulchra survival and performance on these sites. Lolium multiflorum and B. hordeaceus were planted in 20 cm diameter circular plots at a constant rate of 1 seed per cm2 surrounding newly transplanted N. pulchra plants. Nassella pulchra showed no significant effect of the species of competitor or from the distribution of the competitors. Both interspersion of patches of bare ground and separation of competitors into patches did not increase N. pulchra pre-dawn water potential, basal area change, number of seeds produced, or average weight of seeds. The presence of L. multiflorum was associated with a decrease in N. pulchra survival compared with plots with only B. hordeaceus. Plants with increases in basal area of less than 0.75 cm2 during the growing season had 74% mortality compared with no mortality in plants with more growth. However, initial N. pulchra plant size was not a good predictor of mortality. Limiting competition from annuals may increase survival of N. pulchra plantings, but 60% of the plants survived for at least 1 year, despite being transplanted into soil containing substantial annual grass seed.

Notizen: Plants that have evolved to survive on metal-rich soils—metallophytes—have key values that must drive research of their unique properties and ultimately their conservation. The ability of metallophytes to tolerate extreme metal concentrations commends them for revegetation of mines and metal-contaminated sites. Metallophytes can also be exploited in environmental technologies, for example, phytostabilization, phytoremediation, and phytomining. Actions towards conserving metallophyte species are imperative, as metallophytes are increasingly under threat of extinction from mining activity. Although many hundreds of papers describe both the biology and applications of metallophytes, few have investigated the urgent need to conserve these unique species. This paper identifies the current state of metallophyte research, and advocates future research needs for the conservation of metallophyte biodiversity and the sustainable uses of metallophyte species in restoration, rehabilitation, contaminated site remediation, and other nascent phytotechnologies. Six fundamental questions are addressed: (1) Is enough known about the global status of metallophytes to ensure their conservation? (2) Are metallophytes threatened by the activities of the minerals industry, and can their potential for the restoration or rehabilitation of mined and disturbed land be realized? (3) What problems exist in gaining prior informed consent to access metallophyte genetic resources and how can the benefits arising from their uses be equitably shared? (4) What potential do metallophytes offer as a resource base for phytotechnologies? (5) Can genetic modification be used to “design” metallophytes to use in the remediation of contaminated land? (6) Does the prospect of using metallophytes in site remediation and restoration raise ethical issues?

Notizen: Historical landscape reconstructions provide baseline information for evaluating current land management regimes and restoration potentials. We assessed the historical landscape composition and structure of the state of Wisconsin (U.S.A.). This knowledge forms a basis for delineation of potential spatial distribution of forest species and landscape structures before major human-induced changes, quantification of the spatial extent and intensity of change in habitats and landscapes, and identification of target areas for ecological restoration (e.g., threatened ecosystems). Methods included two conceptually and methodologically different vegetation classifications. The classifications rely on the original U.S. Public Land Office Surveys conducted during the nineteenth century to sell land to Euro-American settlers. The subjective classification method we examined was R. W. Finley's “Original Vegetation of Wisconsin.” This classification accounts for qualitative information such as early land surveyors' descriptions of ecosystems (e.g., distinctions into wet and dry prairies). However, the classification is hard to reproduce because some criteria are not strictly hierarchical or exclusive. Numerical cluster analysis was used as an objective classification method. This method offers reproducible, quantitative results and full hierarchical distinction between the classes. Qualitative information, however, is not accounted for in the objective numerical approach and may thus be viewed as less complete when representing local landscape details. Both classifications represent major vegetation characteristics consisting of a complex mosaic of forests (coniferous, mixed coniferous–deciduous, deciduous, and swamps), savannas (oak and pine), and prairies. The objective classification indicates that savannas cover two times more (40%) and prairies six times less area (2%) compared with the subjective classification (savanna, 20%; prairie, 12%). We address the applications of these classifications to current and potential restoration projects, including eastern hemlock (Tsuga canadensis), wetland/riparian, savanna, and prairie ecosystems.

Notizen: We provide a novel explanation as to why forming an alliance of buyers (or sellers) across separate markets can be advantageous when input prices are determined by bargaining. Our explanation helps to understand the prevalence of buyer cooperatives among small and medium-sized firms.

Notizen: Recent developments in information technology (IT) have resulted in the collection of a vast amount of customer-specific data. As IT advances, the quality of such information improves. We analyze a unifying spatial price discrimination model that encompasses the two most studied paradigms of two-group and perfect discrimination as special cases. Firms use the available information to classify the consumers into different groups. The number of identifiable consumer segments increases with the information quality. Among our findings (1) when the information quality is low, unilateral commitments not to price discriminate arise in equilibrium; (2) after a unique threshold of information precision such a commitment is a dominated strategy, and the game becomes a prisoners' dilemma; and (3) equilibrium profits exhibit a U-shaped relationship with the information quality.

Notizen: In the context of (one-sided) delegated bargaining, we analyze how a principal (a seller) should design the delegation contract in order to provide proper incentives for her delegate (an intermediary) and gain strategic advantage against a third party (a buyer). We consider situations in which there are both moral hazard and adverse selection problems in the delegation relationship and where the seller tries to gain strategic advantage by imposing a minimum price above which she pays the delegate a commission. It is shown that incentives and commitment are substitutes. A low-type agent is given less discretion in dealing with the buyer and weaker incentives, while a high-type agent is given more discretion and stronger incentives.

Notizen: This paper sutudies the role of debt in committing a seller not to trade at a low price. We consider a discrete-time finite-horizon buyer–seller relationship. The seller makes an upfront relationship-specific investment, which is financed with debt. Debt then is repaid gradually to mitigate the hold-up risk. Even though debt is renegotiable, under the assumption that with a small probability renegotiation may fail and may lead to inefficient liquidation, debt still can be used as a commitment device. We solve for renegotiation proof dynamic debt contracts that are optimal for the seller and show that debt is repaid over the entire course of the relationship with declining repayments.

Notizen: Existing models of the principal–agent relationship assume the agent works only under extrinsic incentives. However, many observed agency contracts take the form of a fixed payment. For such contracts to work, the principal must trust the agent to work in the absence of incentives. I show that agency fosters the advent of intrinsic motivation and trustworthy behavior. Three distinct motivational schemes are analyzed: norms, ethical standards, and altruism. I identify conditions under which these mechanisms arise and show how they promote trust. The analysis alters several important predictions of conventional models: (1) Better outcomes may ensue in highly uncertain environments; (2) the principal is better off the more the agent is risk averse; and (3) larger equilibrium extrinsic incentives need not be associated with larger effort or larger total surplus.

Notizen: This paper shows that a multiproduct firm may find it optimal not to delegate the sales of all products and therefore to employ different distribution channels for different products. It faces the following trade-off: There is a strategic effect associated with delegation, but if both products' sales are delegated, intrafirm competition is not internalized. By delegating the sales of just one of the products while selling the other product directly—partial delegation—the multiproduct manufacturer strikes just the right compromise: The externalities between its owns products are internalized partially while a strategic advantage is achieved against its rival single-product manufacturer. Partial delegation also holds if both products are sold by a common retailer; it dominates full delegation when both manufacturers are multiproduct firms.

Notizen: Recent research finds that firms investing abroad tend to agglomerate with other foreign entrants. Yet firms often invest multiple times within the same host country, which raises the question of whether firms agglomerate with their competitors' or their own prior investments. Collocation's attractiveness also may vary as a firm's entry motives evolve. The activities of prior and present investments often differ—initial investment may be for distribution while later ones might be for manufacturing. For Japanese investment into the United States in the electronics sector from 1980 to 1998, we find that firms tend to collocate only with their own prior investments. The exception is firms with little of their own experience, who tend to collocate with competitors. These results demonstrate the importance of firm heterogeneity in determining agglomeration behavior.

Notizen: This paper seeks to understand why improved information technology (IT) might strengthen the case for decentralization, as recent empirical work suggests. We study a firm with a headquarters and two managers, each of whom gathers information about her changing local environment. The firm earns a gross profit that depends on actions taken as well as the current local environments. More information permits better actions, and information-gathering costs drop as IT improves. When the firm is centralized, information-gathering expenditures are first best, but after the firm decentralizes, each manager becomes a self-interested player of a “sharing game” in which she collects a share of gross profit and bears the cost of her chosen information-gathering activities. The firm's actions are determined by the information gathered at the equilibria of the game. As a result, the firm experiences a decentralization penalty, namely the change in net profit (gross profit minus informational costs) after decentralizing. If the penalty is small, then it is outweighed by the advantages of decentralizing—the vanishing of monitoring costs and perhaps the improved motivation of a decentralized manager's staff. To gather information a manager chooses (once and for all) a partitioning of her possible local environments and then searches to find the set in which her current environment lies. Our main measure of a manager's information cost is a technology parameter, θ, times the number of sets in her chosen partitioning. A second measure is θ times the partitioning's “Shannon content,” which may be interpreted as average search time when search is efficient. We ask whether improved IT, i.e., a drop in θ, indeed lowers the decentralization penalty. We obtain a strongly affirmative answer to this question for both cost measures in a class of examples and a mixed answer when we generalize so as to preserve some of the key properties of those examples. In a parallel manner we explore another conjecture suggested in the empirical literature, namely that better IT raises the coordination benefit, which we define as the increase in net profit when the firm bases its actions on pooled information, rather than letting each action variable depend on the information gathered by just one manager.

Notizen: This paper analyzes the structure of retail markets by highlighting the differential pattern exhibited across local markets by two different types of firm organization: chain stores versus stand-alone stores. Data from retail alcoholic beverage industry in California suggest that the number of chain stores is proportional to city size. Further evidence on the sales of establishments indicates that average size of a stand-alone store virtually is invariant to city size, whereas chain stores appear to get larger as city size increases. Theories consistent with these findings are discussed.

Notizen: In differentiated product markets where consumer preferences are characterized by brand loyalty, an important role for advertising may be to overcome brand loyalty by encouraging consumers to switch to less familiar brands. Using a scanner panel dataset of breakfast-cereal purchases, I find evidence consistent with the hypothesis that advertising counteracts the tendencies of brand loyalty toward repeat purchasing. Equivalently, advertising reduces switching costs in this market. Furthermore, counterfactual experiments demonstrate that in markets with brand loyalty, advertising is an attractive and effective option—relative to alternative promotional activities, such as price discounts—of stimulating demand for a brand.

Notizen: Durable-goods producers frequently choose to monopolize the maintenance markets for their own products. This paper shows that, similar to leasing, one reason a firm may employ this practice is that it reduces or even eliminates problems due to time inconsistency. We first demonstrate this result in a setting closely related to Bulow's (1982) classic analysis of durable-goods monopoly. We then show the result in a setting similar to those considered in Waldman (1996, 1997) and Hendel and Lizzeri (1999), in which new and used units are imperfect substitutes. The paper also discusses alternative explanations for the phenomenon.

Notizen: While selling an existing product, a durable-goods monopolist may develop a new, improved product. The firm must consider the interaction between its intertemporal pricing and research and development (R&D) decisions. The interactions show a sharp dichotomy depending on pricing regimes. When it is optimal for the firm to continue to sell the old model along with the new model, the interactions disappear. However, when it is optimal for the firm to discontinue the sale of the old model after introducing the new model, the firm will face a time-inconsistency problem in its R&D decision.

Notizen: We analyze investment by a population of hyperbolic discounting entrepreneurs. In order to avoid inefficient procrastination, agents with good prospects about their chances of success may choose to forego free information and to invest boldly. This explains an excessive level of investment in the economy. Building on this observation, we show that low risk-free interest rates favor bold entrepreneurship and entry mistakes. Furthermore, public intervention can be socially desirable: Forcing agents to acquire information before deciding whether to invest may reduce competitive interest rates and may be beneficial for all individuals in the economy.〈blockFixed type="quotation"〉And thus the native hue of resolution 
Is sicklied o'er with the pale cast of thought, 
And enterprises of great pith and moment 
With this regard their currents turn awry, 
And lose the name of action. 
          Hamlet, Act 3: Scene 1.

Notizen: Observers routinely claim that the Japanese government of the high-growth 1960s and 1970s rationed and ultimately directed credit. It barred domestic competitors to banks, insulated the domestic capital market from international competitive pressure, and capped loan interest rates. In the resulting credit shortage, it promoted industrial policy by rationing credit. As much as the government purported to ration and to direct credit, it apparently accomplished nothing of the sort. It did not block domestic rivals to banks successfully, did not insulate the market from international forces, and did not set maximum interest rates that bound. Using evidence on loans to all 1,000-odd firms listed on Section 1 of the Tokyo Stock Exchange from 1968 to 1982, we find that observed interest rates reflected borrower risk and mortgageable assets and that banks did not use low-interest deposits to circumvent any interest caps. Instead, the loan market seems to have cleared at the nominal rates. We follow our empirical inquiry with a case study of the industry to which the government tried hardest to direct credit: ocean shipping. We find no evidence of credit rationing. Despite the government programs to allocate capital, nonconformist firms funded their projects readily outside authorized avenues. Indeed, they funded them so readily that the nonconformists grew with spectacular speed and earned their investors enormous returns.

Notizen: Restoration often includes control of invasive plants, but little is known about how native plant communities respond to this control. The biennial Alliaria petiolata (M. Bieb.) Cavara and Grande (garlic mustard) is one of the most prevalent invasive plants in forests of eastern North America. We investigated the effects of the herbicide Round-up (glyphosate) on Alliaria and the response of the forest floor plant community to the herbicide and the subsequent decline of Alliaria. In an old-growth Acer–Fagus stand and a second-growth Liriodendron-dominated stand in Hueston Woods State Nature Preserve, Ohio, United States, we spot applied Round-up in November 2000 and 2001 in 25 1 × 1–m plots and maintained 25 control plots. Herbicide decreased Alliaria density in both stands and reduced the density of other species in leaf during treatment (mostly exotic winter annuals) in the old-growth stand. Treatment did not affect the initial density of the Alliaria cohort that germinated in the spring of 2001, but decreased the 2002 cohort. Community differences were found in the old-growth stand after Alliaria reduction, specifically greater cover of spring ephemerals in the herbicide treatment. In the second-growth stand, herbicide treatment increased reproduction of the late-summer perennial, Phryma leptostachya. These results indicate that glyphosate reduces Alliaria without negatively impacting native species and that some native species respond positively to a single-year reduction in this invasive biennial.

Notizen: Bottomland hardwood forests of the southeastern United States have declined in extent since European settlement. Forest restoration activities over the past decade, however, have driven recent changes in land use through an intensified afforestation effort on former agricultural land. This intense afforestation effort, particularly in the Lower Mississippi Alluvial Valley, has generated a demand for alternative afforestation systems that accommodate various landowner objectives through restoration of sustainable forests. We are currently studying an afforestation system that involves initial establishment of the rapidly growing native species eastern cottonwood (Populus deltoides Bartr. ex Marsh.), followed by enrichment of the plantation understory with Nuttall oak (Quercus nuttallii Palm.). In this article, we examine the growth and biomass accumulation by Nuttall oak seedlings to determine whether this species can be established and whether it will develop beneath the cottonwood overstory. After 3 years of growth beneath cottonwood canopies, Nuttall oak seedlings were similar in height (126 cm), but were 20% smaller in root-collar diameter than seedlings established in open fields. Seedlings established in the open accumulated more than twice the biomass of seedlings growing beneath a cottonwood canopy. However, the relative distribution of accumulated biomass in seedlings did not differ in the two environments. Ten percent of total seedling biomass was maintained in leaf tissue, 42% was maintained in stem tissue, and 48% was maintained in root tissue on open-grown seedlings and seedlings established in the understory of cottonwood plantations. Though establishment in the more shaded understory environment reduced Nuttall oak growth, seedling function was not limited enough to induce changes in plant morphology. Our results suggest that an afforestation system involving rapid establishment of forest cover with a quick-growing plantation species, followed by understory enrichment with species of later succession, may provide an alternative method of forest restoration on bottomland hardwood sites and perhaps other sites degraded by agriculture throughout temperate regions.

Notizen: Magnesian limestone grassland is the rarest limestone grassland community in the United Kingdom, with many sites having been lost to quarrying and urban development. Its reestablishment, and that of many other semi-natural grassland habitats, can be enhanced using seed collected from established communities. However, few studies have evaluated the effectiveness of methods of seed harvesting. The objectives of this study were to (1) test the effectiveness of a hand-held vacuum harvester in the collection of an adequate quantity of seed, and range of species, to revegetate former quarries and (2) determine the optimum time for seed collection based on a phenological study of the plants at the donor site. Germination tests of harvested seed were used to identify species, based on the germinating seedlings. Thirty-six species were identified, with Briza media (quaking grass) and Festuca sp. (red and sheep's fescue) being the dominant species and accounting for 74% of germinating seedlings. Species composition of vacuum-harvested seed was compared with species composition of the vegetation found in the principal donor site. The most common species in the collected seed were also common at the donor site, but some characteristic species of the grassland were absent or did not germinate. Most species reached a peak in ripe seed production between mid-August and early September. Although having several advantages, vacuum harvesting will not, by itself, provide either sufficient quantity of seed or the wide range of species often required. Suggestions are given for combining this technique with other methods.

Notizen: The planting of sand-binding vegetation in the Shapotou region at the southeastern edge of the Tengger Desert began in 1956. Over the past 46 years, it has not only insured the smooth operation of the Baotou–Lanzhou railway in the sand dune section but has also played an important role in the restoration of the local eco-environment; therefore, it is viewed as a successful model for desertification control and ecological restoration along the transport line in the arid desert region of China. Long-term monitoring and focused research show that within 4–5 years of establishment of sand-binding vegetation, the physical surface structure of the sand dunes stabilized, and inorganic soil crusts formed by atmospheric dust gradually turned into microbiotic crusts. Among the organisms comprising these crusts are cryptogams such as desert algae and mosses. In the 46 years since establishing sand-binding vegetation, some 24 algal species occurred in the crusts. However, only five moss species were identified, which was fewer than the species number in the crust of naturally fixed sand dunes. Other results of the planting were that near-surface wind velocity in the 46-year-old vegetation area was reduced by 54.2% compared with that in the moving sand area; soil organic matter increased from 0.06% in moving sand dunes to 1.34% in the 46-year-old vegetation area; the main nutrients N, P, K, etc., in the desert ecosystem increased; soil physicochemical properties improved; and soil-forming processes occurred in the dune surface layer. Overall, establishment of sand-binding vegetation significantly impacted soil water cycles, creating favorable conditions for colonization by many herbaceous species. These herbaceous species, in turn, facilitated the colonization and persistence of birds, insects, soil animals, and desert animals. Forty-six years later, some 28 bird species and 50 insect species were identified in the vegetated dune field. Thus, establishment of a relatively simple community of sand-binding species led to the transformation of the relatively barren dune environment into a desert ecosystem with complex structure, composition, and function. This restoration effort shows the potential for short-term manipulation of environmental variables (i.e., plant cover via artificial vegetation establishment) to begin the long-term process of ecological restoration, particularly in arid climates, and demonstrates several techniques that can be used to scientifically monitor progress in large-scale restoration projects.

Notizen: In many markets, firms are able to conduct discriminatory strategies based on whether a customer prefers a competitors' product or their own. This article considers the impact of such discrimination in duopoly models in which firms set prices and conduct precontract-customization efforts for some customers. We identify two effects: (1) The ability to conduct preference-based discrimination increases equilibrium profit as long as long as precontract customization is at least modestly important in competitive dynamics; and (2) The ability to conduct preference-based discrimination enhances social welfare if any precontract customization is done.

Notizen: In this paper, we examine Hong Kong's role in intermediating trade between China and the rest of the world. Hong Kong traders distribute a large fraction of China's exports. Net of customs, insurance, and freight charges, re-exports of Chinese goods are much more expensive when they leave Hong Kong than when they enter. Hong Kong markups on re-exports of Chinese goods are higher for differentiated products, products with higher variance in export prices, and products sent to China for further processing. These results are consistent with the view that traders resolve informational problems in exchange. Additional results suggest that traders price discriminate across destination markets and use transfer pricing to shift income from high-tax countries to Hong Kong.

Notizen: In a model where upstream network insiders conduct relationship-specific investment, downstream firms have an incentive to transact within networks. Evidence from US auto parts exports to 26 auto-producing countries supports key predictions of the model. Greater production scale for assemblers lowers imported parts per car. Vertical networks matter in two ways. First, although Japan's average import levels are not unusually low, non-Japanese suppliers have relatively low market penetration for parts categories where vertical keiretsu are prominent in Japan. Second, US-owned assembly abroad and foreign-owned parts production in the US both stimulate parts exports.

Notizen: Motivated by evidence on the importance of incomplete information and networks in international trade, we investigate the supply of network intermediation. We build a general-equilibrium model in which agents with networks of foreign contacts either can use their networks themselves in support of production or can make their networks available for others to use and thereby can become network intermediaries. We use this model for comparative statics and welfare analysis. One welfare conclusion is that intermediaries may have inadequate incentives to maintain or to expand their networks, suggesting a rationale for the policies followed by some countries to encourage large-scale trading companies.

Notizen: We analyze how product differentiation influences firms' choice between exporting and foreign direct investment. When product specifications are determined endogenously, we show that there is no symmetric solution to the product specification subgame. The cost disadvantage of an exporting firm translates into a disadvantage in product specification. Overseas production is favored if this allows the investing firm to adopt a more aggressive product specification. Our analysis suggests an ambiguous relationship among location, product differentiation, and cost and demand functions, confirmed by the existence of a parameter range for which there is no pure strategy equilibrium in location choice.

Notizen: We examine a heterogenous goods duopoly model, wherein governments simultaneously and noncooperatively choose whether or not to provide subsidies for their firms and then firms noncooperatively choose output levels, either sequentially or simultaneously. We find that government trade policy and market structure are interdependent. First, the trade regime alters traditional firm preferences over sequential versus simultaneous play. Second, different market structures influence governments' preferences about free trade versus subsidies. Further, if one of the firms is a potential leader, allowing for endogenous market structure generates equilibrium outcomes that sometimes reinforce, and sometimes counter, traditional results in the strategic trade literature.

Notizen: Planting native species into restoration settings where other natives already occur is a common practice. However, the competitive consequences of such plantings are rarely studied. Planting density also affects restoration costs. Here we examined the effects of established individuals of Lemmon's needlegrass (Achnatherum lemmonii) on plugs of bluebunch wheatgrass (Pseudoroegneria spicata) and Idaho fescue (Festuca idahoensis) in a restoration site in Oregon. All three of these grasses are local native perennials. Plugs were planted at 6, 12, and 18 cm from established A. lemmonii bunchgrasses and also in plots without A. lemmonii neighbors. Plug survival was uniformly high, averaging more than 98%. Plugs planted at 6 cm from established grasses showed significantly lower growth and reproduction than plugs planted at 18 cm, which had similar values to plugs not planted in the vicinity of A. lemmonii. These results suggest that interplanting distances of as little as 18 cm were sufficient to greatly reduce competitive effects on newly planted plugs, at least in early establishment at this site.

Notizen: Restoration of tallgrass prairie on former agricultural land is often impeded by failure to establish a diverse native species assemblage and by difficulties with nonprairie, exotic species. High levels of available soil nitrogen (N) on such sites may favor fast-growing exotics at the expense of more slowly growing prairie species characteristic of low-N soils. We tested whether reducing N availability through soil carbon (C) amendments could be a useful tool in facilitating successful tallgrass prairie restoration. We added 6 kg/m2 hardwood sawdust to experimental plots on an abandoned agricultural field in the Sandusky Plains of central Ohio, United States, increasing soil C by 67% in the upper 15 cm. This C amendment caused a 94% reduction in annual net N mineralization and a 27% increase in soil moisture but had no effect on total N or pH. Overall, plant mass after one growing season was reduced by 64% on amended compared with unamended soil, but this effect was less for prairie forbs (−34%) than for prairie grasses (−67%) or exotics (−62%). After the second growing season, only exotics responded significantly to the soil C amendment, with a 40% reduction in mass. The N concentration of green-leaf tissue and of senescent leaf litter was also reduced by the soil C treatment in most cases. We conclude that soil C amendment imparts several immediate benefits for tallgrass prairie restoration––notably reduced N availability, slower plant growth, and lower competition from exotic species.

Notizen: Studying the process of population restoration is helpful for managing and preserving endangered species. A population of Oryza rufipogon (wild rice), an endangered species, was reintroduced in 1993 into Huli Marsh. We conducted a detailed survey over a 5-year period (1997–2001) to evaluate the present status of the population and to further our understanding of its habitat requirements and the population model. The population was surveyed using 2 × 2–m quadrats in mid-September of each year. In total, 2,683 quadrats were surveyed covering the whole O. rufipogon reserve during each survey. The population's spatial distribution was mapped, and the maps were used to examine the relationship between patch replacement and water depth. The individual number of O. rufipogon increased steadily from 1993 to 2001. The patch number, patch area, mean patch size, and largest patch size increased over this time period, and Korcak patchiness exponents decreased. On average, 83% of the patches persisted from one year to the next. There was a significant positive correlation between the initial patch size and the size the following year. The probability of patch disappearance decreased as patch size increased. Fifty-eight percent of the patches were located at water depths between 20 and 30 cm. Water depth had no significant effect on the patch transition from O. rufipogon to other species. The loss and gain of O. rufipogon patches were statistically correlated with the patch areas in different water depths. Our results show that the population of O. rufipogon can successfully be reintroduced to the original habitat after appropriate environmental conditions have been restored. We recommend the following transplantation practices: transplant many smaller patches rather than a few larger patches, use transplant patch sizes of at least 20 m2, and transplant into sites vegetated with species with different regeneration niches from the transplanted species.

Notizen: This work addressed the seasonal and successional factors of root dynamics in natural and restoration Atlantic white cedar (AWC) wetlands. Using minirhizotrons and soil root cores, fine root dynamics were measured in a chronosequence of reference and restoration AWC wetlands to compare trends in ecosystem development after canopy harvest. Seasonal fine root abundance, production, and mortality were sampled during a 439-day period in one restoration and three reference AWC wetlands. Soil cores were collected to measure fine root biomass and to determine allometric relationships between root length and biomass. Significant seasonal variation of root dynamics was observed in the young reference and restoration sites. The mature and intermediate-aged sites exhibited little seasonal variability in root abundance and mortality. Root production was variable but not seasonally consistent. Results suggest that root dynamics become less seasonal as AWC communities shift from herbaceous to woody vegetation dominance. No trend in fine root abundance along the chronosequence was observed, suggesting that roots rapidly reestablish following tree harvest. Measurements of annual root length production suggest increasing annual production with decreasing stand age. However, a reversal of this trend was observed when using production estimates calculated from minirhizotron measurements and root length–mass relationships. These findings underscore the importance of supplementing minirhizotron data with root allometric relationships when analyzing vegetation gradients. Overall, results indicate substantial differences in the form and quantity of root contributions to soil organic matter in the restoration site compared to that in the reference chronosequence. Higher initial planting densities of AWC are recommended to achieve similar contributions of roots to soil organic matter accumulation in the restoration site.

Notizen: Odonate assemblages were compared between replicate sets of shallow lakes that had been created and acidified by open-cast mining across a large area (2,451 ha) of southwest France (Arjuzanx, Landes); one set of lakes (n = 5) was experimentally restored by liming with calcium carbonate, whereas another group (n = 5) was left as untreated reference lakes. Both odonate adults and exuviae were sampled bimonthly during May–August 1998. Elevated turbidity and conductivity in limed lakes were the only physicochemical measures differing between restored and reference lakes, because deacidification occurred naturally, even in reference lakes during the 17 years after the onset of restoration. Restoration by liming can apparently lead to effects on lake turbidity that might be considered adverse. Twenty-four and 19 odonate species occurred among adults and exuviae, respectively, but there were no significant differences in richness between restored and reference sites. However, significantly, more exuviae were collected from the reference sites (588 vs. 180), where exuvial diversity and rank abundance indicated more evenly structured assemblages than those in restored lakes. Ordination showed that adult assemblages differed significantly between restored and reference lakes, and varied highly significantly with lake turbidity. This effect occurred because a small group of generally scarce adults were characteristic of reference sites (Chalcolestes viridis, Lestes virens, Cordulia aenae, Leucorrhinia albifrons, and Sympetrum sanguineum). Exuviae of these same species were less abundant at restored sites, but exuvial assemblages overall did not discriminate between restored and reference lakes. We conclude that lake restoration by liming can reduce diversity and larval numbers among odonates and subtly affects adult assemblages. In this case study, adult assemblages discriminated best between the lake types involved in the experiment, but important additional information arose from exuvial abundance and structure. This study indicates that natural recovery processes after acidification in formerly open-cast areas––rather than chemical intervention through liming––might lead to preferable conservation outcomes.

Notizen: We investigated the assumption that populations of epibenthic macroinvertebrates readily establish in created coastal wetlands by quantifying the spatial and temporal patterns of Cerithidea californica (California horn snail) density in a newly created wetland and an adjacent natural area in Mugu Lagoon, southern California, United States, for 3.5 years. The natural and created sites differed in vascular plant cover and sediment grain size, organic content, salinity, and moisture content. Densities of C. californica in the created site changed little during the study period, and were often lower than those in the natural site. The influences of habitat suitability and dispersal limitation on C. californica colonization of the created site varied among snail age classes. Sediment moisture and organic content explained some of the variability in subadult (47%) and adult (55%) density and relative abundance, but none of the variability in juvenile abundance. Adult snail density was also strongly influenced by distance from the natural/created site transition zone. Juvenile and subadult snail densities were not related to distance from the natural site, possibly due to greater dispersal ability. Between-site differences in C. californica densities and size structure suggested that adult snails were affected by both habitat characteristics and dispersal ability, subadults were influenced to a lesser degree by habitat characteristics, and juveniles were not related to either factor. Accordingly, the influence of habitat characteristics and dispersal ability on created site colonization may change with snail age. Successful restoration of benthic invertebrate communities requires consideration of both habitat characteristics and dispersal ability of the target species, even in created sites in close proximity to natural areas.

Notizen: In degraded ecosystems where the impact on wildlife and the destruction of natural systems is high, restoration becomes a critical component of recovery. Monitoring restoration activities plays a key role in determining end points for restoration and assessing effectiveness. Appropriate monitoring of major systems, particularly in assessing vegetation reestablishment and slope stabilization, requires a long-term commitment to annual assessment of change and improvement over time. However, intrinsic factors built into government or public management systems, such as budgeting and staffing limitations, limit the ability for long-term monitoring of critical restoration projects. In the research reported in this article, we devised and assessed a new remote method for assessing restoration success and tested it on restoration and monitoring requirements in Lyell Island, British Columbia. We developed a system (the oblique data fusion system [ODFS]) to extract spatial information from oblique aerial video imagery. The ODFS enables low-cost change detection and database updates at a range of operational scales. System tests show an absolute spatial accuracy on the order of ±2.1 m. The evaluation, based on digitized historical data, ground surveys, and the ODFS-derived data, indicates that the landslide rate (new area/year) tapered off following treatment; after 5 years it had been reduced by a factor of 3 relative to the background rate. The recovery is deemed sufficient to initiate secondary restoration tasks. The evaluation demonstrates the accuracy and utility of the ODFS for long-term monitoring of landscape restoration efforts, particularly in remote areas. In conclusion, this new innovative method shows considerable promise for park managers.

Notizen: Shrubs are commonly considered competitors of planted seedlings in reforestation programs. However, shrubs can facilitate the establishment of understory seedlings in environments that, like Mediterranean-type ecosystems, are characterized by harsh environmental conditions. In 1997, an experiment was set up in the Sierra Nevada mountains (southeast Spain) to test the use of shrubs as nurse plants for an alternative reforestation technique. Two-year-old seedlings of Pinus sylvestris and Pinus nigra were planted in four microhabitats: (1) open interspaces without vegetation (which is the usual method employed in reforestation programs), (2) under individuals of the shrub Salvia lavandulifolia, (3) under the north side of spiny shrubs, and (4) under the south side of spiny shrubs. Seedlings were also distributed in plots with and without ungulates to test the effect of herbivore damage. We report here the results of survival and growth after four growing seasons, a time span long enough to draw robust conclusions concerning the suitability of this technique. Pine survival was remarkably higher when planted under individuals of S. lavandulifolia as compared with open areas (2.6 times for P. sylvestris and 1.8 for P. nigra). The survival of both pine species was also higher when planted on the north side of spiny shrubs, while mortality on the south side was similar to that found in open areas. The reduction of solar radiation by the canopy of shrubs was likely the main factor determining shrub facilitation. The growth of the pines differed among years. However, growth was not inhibited when planted with shrubs as compared with open areas in any of the years. Herbivore damage was low but was mostly concentrated in the leader shoot, exacerbating the deleterious effect of ungulate herbivores on pine growth. We conclude that the use of shrubs as nurse plants for reforestation is a viable technique to increase establishment success of reforestation in Mediterranean-type ecosystems and that it might be similarly useful in other water-stressed environments. In addition, this technique offers the advantage of following natural succession, thus minimizing the impact in the community.

Notizen: Overstory reduction and slash mulching (ORSM) has been shown to be an effective means for increasing herbaceous cover and diversity in degraded piñon (Pinus edulis) and juniper (Juniperus monosperma) woodlands of north-central New Mexico. Local fire history, tree age-class structure, and grazing records suggest that many areas now occupied by dense piñon-juniper woodlands were formerly more open, with grassy understories that supported well-developed soils and a fire regime. At Bandelier National Monument, studies are evaluating the use of ORSM treatments as a restoration management tool. In 1999 and 2001, we evaluated the effects of an ORSM treatment implemented in 1997 upon butterfly abundance and species richness between a pair of treated and control watersheds. Butterfly abundance and species richness were significantly greater on the treated watershed in both years, and these measures were correlated with significant increases in forb and grass cover in the treated watershed. Five of the 10 most common nectar and larval host plants had significantly greater cover in the treated watershed, including the legume Lotus wrightii. Our results suggest that the increased herbaceous cover resulting from an ORSM treatment of a single watershed induced a positive, initial response by butterflies. Using butterflies as indicators of site productivity and species richness, our results suggest ORSM is a promising technique for restoring biodiversity in degraded piñon-juniper woodlands.