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  • 1
    Electronic Resource
    Electronic Resource
    Altitudinal patterns in host suitability for forest insects (1998)
    Springer
    Oecologia 117 (1998), S. 133-142 
    Details
    ISSN: 1432-1939
    Keywords: Key words Temperature  ;  Atmospheric nitrogen deposition  ;  Altitude  ;  Lymantria dispar  ;  Orgyia leucostigma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Conspecific trees growing at high and low-elevations encounter different growing conditions and may vary in their suitability as hosts for herbivorous insects. Mountain tree populations may be more resistant to herbivory if low temperatures constrain growth more than they constrain photosynthesis, resulting in increased secondary metabolism (temperature hypothesis). Alternatively, mountain trees may be fertilized by atmospheric nitrogen deposition and become more palatable to insects (atmospheric deposition hypothesis). We evaluated these two hypotheses by comparing high- and low-elevation trees with insect bioassays and analyses of foliar nitrogen and condensed tannin. Contrary to the temperature hypothesis, high-elevation foliage had higher leaf nitrogen (six of six tree species) and allowed higher growth rates of Lymantria dispar larvae (five of six tree species). The nitrogen deposition hypothesis was broadly supported by measurements from two mountains showing that high-elevation trees tended to have higher leaf nitrogen, lower leaf tannins, and support higher insect growth performance than conspecific trees from lower elevations. The deposition hypothesis was further supported by fertilization studies showing that simulated atmospheric nitrogen deposition changed the foliar chemistry of valley trees to resemble that of high-elevation trees. Predictions that the altitudinal gradient in foliar chemistry and host suitability should be steepest on mountains receiving more deposition were largely not supported, but interpretations are complicated by lack of replication among mountains. In the northeastern United States, increased host suitability of high-elevation trees seems sufficient to influence the population dynamics and community composition of herbivores. Atmospheric nitrogen deposition offers a promising hypothesis to explain and predict some important spatial patterns in herbivory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050641
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Climatic effects on caterpillar fluctuations in northern hardwood forests (2007)
    Canadian Science Publishing
    Details
    Publication Date: 2007-02-01
    Description: Fluctuations in the abundance of Lepidoptera are common but inadequately understood. Here we show that caterpillar abundance in the White Mountains of New Hampshire has fluctuated by 〉20-fold from 1986 to 2005. We report tests of three possible causes: (i) extreme winter cold; (ii) long, warm summers; and (iii) interannual variation in tree growth, which tends to correlate with phytochemistry. Caterpillar fluctuations from summers t to t + 1 were uncorrelated or negatively correlated with minimum air temperature during the intervening winter (does not support the first cause), but were positively correlated with thermal sum during summer t (r = 0.49–0.56) (supports the second cause). There was limited interannual variation in the radial growth of two dominant tree species ( Acer saccharum Marsh. and Betula alleghaniensis Britt.) and no correlation with caterpillar fluctuations (refutes the third cause). Thermal sum might influence caterpillar fluctuations through direct effects on insect development, indirect effects on susceptibility to natural enemies, and (or) indirect effects on plant-insect interactions; the mechanisms are of particular interest because thermal sums have been increasing since local records began in 1957 (r = 0.41–0.45). In hardwoods forests of the northeastern United States, there is some broad-scale driver related to summer temperatures that generates fluctuations in caterpillar abundance, which influences herbivory as well as higher level consumers, such as insectivorous birds.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 3
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    Differential impacts of the southern pine beetle, Dendroctonus frontalis, on Pinus palustris and Pinus taeda (2007)
    Canadian Science Publishing
    Details
    Publication Date: 2007-08-01
    Description: Patterns of host use by herbivore pests can have serious consequences for natural and managed ecosystems but are often poorly understood. Here, we provide the first quantification of large differential impacts of the southern pine beetle, Dendroctonus frontalis Zimmermann, on loblolly pine, Pinus taeda L., and longleaf pine, Pinus palustris P. Mill., and evaluate putative mechanisms for the disparity. Spatially extensive survey data from recent epidemics indicate that, per square kilometre, stands of loblolly versus longleaf pine in four forests (380–1273 km2) sustained 3–18 times more local infestations and 3–116 times more tree mortality. Differences were not attributable to size or age structure of pine stands. Using pheromone-baited traps, we found no differences in the abundance of dispersing D. frontalis or its predator Thanasimus dubius Fabricius between loblolly and longleaf stands. Trapping triggered numerous attacks on trees, but the pine species did not differ in the probability of attack initiation or in the surface area of bark attacked by growing aggregations. We found no evidence for postaggregation mechanisms of discrimination or differential success on the two hosts, suggesting that early colonizers discriminate between host species before a pheromone plume is present.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 4
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    Alternate attractors in the population dynamics of a tree-killing bark beetle (2012)
    Springer
    Details
    Publication Date: 2012-12-08
    Print ISSN: 1438-3896
    Electronic ISSN: 1438-390X
    Topics: Biology
    Published by Springer
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  • 5
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    Synchrony's double edge: transient dynamics and the Allee effect in stage structured populations (2007)
    Wiley
    Details
    Publication Date: 2007-07-01
    Print ISSN: 1461-023X
    Electronic ISSN: 1461-0248
    Topics: Biology
    Published by Wiley
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  • 6
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    Jensen’s inequality predicts effects of environmental variation (1999)
    Cell Press
    Details
    Publication Date: 1999-09-01
    Print ISSN: 0169-5347
    Electronic ISSN: 1872-8383
    Topics: Biology
    Published by Cell Press
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  • 7
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    High-resolution analysis of stem increment and sap flow for loblolly pine trees attacked by southern pine beetle (2004)
    Canadian Science Publishing
    Details
    Publication Date: 2004-11-01
    Description: Manual and automated dendrometers, and thermal dissipation probes were used to measure stem increment and sap flow for loblolly pine (Pinus taeda L.) trees attacked by southern pine beetle (Dendroctonus frontalis Zimm.) in east Tennessee, USA. Seasonal-long measurements with manual dendrometers indicated linear increases in stem circumference from April through June. Changes in stem circumference slowed after this time, and further increases were either modest or not observed. These effects coincided with a massive midsummer infestation of trees with southern pine beetles. High-resolution measurements with automated dendrometers confirmed that, while early-season increases in radial increment were positive, daily rates of radial increment for slow- and fast-growing trees were largely negative in early to late July. Sap velocity also declined despite favorable weather conditions, but these reductions were not observed until mid-August. Thus, effects on radial increment and stem circumference preceded those on sap velocity by several weeks. The timing of these events, combined with the known developmental rate of southern pine beetles, suggest that disruption of whole-tree water balance is not a prerequisite for the success of attacking beetles or for oviposition by colonizing females and larval development, all of which were completed by early August. Additional field experiments that use high-resolution techniques to measure stem increment and sap flow are needed to more rigorously characterize temporal changes in host physiology during initial invasion and colonization of trees by southern pine beetle.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 8
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    Loblolly pine responds to mechanical wounding with increased resin flow (1998)
    Canadian Science Publishing
    Details
    Publication Date: 1998-04-01
    Description: The oleoresin produced by many conifers has a deleterious effect on numerous associated herbivores, including bark beetles (Coleoptera: Scolytidae), and may have evolved as a plant defense mechanism. Three experiments with juvenile loblolly pine (Pinus taeda L.) used mechanical wounding to drain resin reserves and assess the effects of prior bark wounding on subsequent resin flow up to 7 days post-treatment. Resin flow returned to pre-treatment values within 2 days after wounding began and, in nearly every tree in each experiment, continued to increase on subsequent days. On average, resin flow reached double the pre-treatment values (mean ± SE: 2.10 ± 0.10 vs. 1.13 ± 0.10 g/3 h and 2.28 ± 0.09 vs. 0.90 ± 0.09 g/3 h for wounded vs. pre-treatment in experiments 1 and 2, respectively). Considering its timing and magnitude, this previously undescribed response may be important in modulating interactions between pine trees and bark beetles. In addition, resin flow following treatment was greater in trees in larger crown size classes (thinned 〉 edge of stand = unthinned in experiment 1; edge of stand 〉 thinned 〉 unthinned in experiment 2). This may help explain why trees in thinned stands are less susceptible to southern pine beetle (Dendroctonus frontalis Zimm.) infestation than trees in unthinned stands.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 9
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    Why does longleaf pine have low susceptibility to southern pine beetle? (2007)
    Canadian Science Publishing
    Details
    Publication Date: 2007-10-01
    Description: Pine forests throughout the world are subject to disturbance from tree-killing bark beetles, but pine species differ in their susceptibilities. In the southeastern United States, Pinus palustris Mill. suffers far less mortality from the southern pine beetle, Dendroctonus frontalis Zimmermann, than do its sympatric congeners. We tested the commonly invoked hypothesis that P. palustris has relatively low susceptibility because it has higher oleoresin flow than other pines, especially Pinus taeda L. However, seven studies in three states over 6 years refuted the hypothesis that P. palustris and P. taeda differ in their constitutive resin flow or in their capacity to replace resin depleted by either experimental wounding or natural beetle attacks. Additionally, surveys of natural beetle attacks revealed that P. taeda and P. palustris were equally likely to be attacked and killed when they cooccurred in front of growing infestations. Thus, the relative susceptibility of these two species changes with the spatial scale at which they are mixed, and the strong landscape-scale pattern of low mortality in P. palustris is not because individual trees are physiologically less susceptible. Ultimately, the conspicuous differential impact of D. frontalis on P. taeda and P. palustris may be the product of coevolution between tree defenses and beetle behavior.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 10
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    Forest pests and their management in the Anthropocene (2018)
    Canadian Science Publishing
    Details
    Publication Date: 2018-03-01
    Description: Forest managers are facing unprecedented challenges from rapid changes in forest pests. The core causes are changes in climate, land use, and global distributions of organisms. Due to invasions and range expansions by pests, and propagation of nonnative trees, managers are increasingly confronted with pest problems outside their range of experience. There is a need to adapt pest management practices more quickly and efficiently than is possible when managers work in isolation and mainly learn by trial and error. Here we identify general tactics for adaptation of forest pest management in the Anthropocene: growth and application of practical theory; improved biosecurity against future invasions; improved monitoring, prediction, and mitigation; increased sharing of knowledge among regions, countries, and continents; management plans that anticipate continuing change; improved assessment of costs, benefits, and risks of possible responses to new potential pests; assessment of system responses to pest management decisions so that subsequent decisions are increasingly better informed; and improved understanding of the couplings between forests, forest management, and socioeconomic systems. Examples of success in forest management can aid in other sectors (e.g., agriculture, pastoralism, fisheries, and water resources) that are similarly important to our environmental security and similarly challenged by global change.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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