ALBERT

Description: There is a strong policy move in Britain to improve forest resilience to climate change by increasing stand structural and species diversity. Although currently little used in Britain, the technique of underplanting allows regeneration and diversification of stands while avoiding some of the disadvantages of clearfelling. Two experiments were examined: (1) the growth and survival of five underplanted conifer species of differing shade tolerance in a shelterwood and (2) compared performance of underplanted and open-grown Douglas-fir seedlings on restocking sites. Underplanted Sitka spruce, Norway spruce, noble fir, European silver fir and Douglas-fir were all able to survive and grow. However increased exposure following overstorey removal resulted in some damage and ‘socketing’, especially to taller seedlings, particularly Douglas-fir. This may be linked to poor root development when growing under an overstorey. Microclimate conditions on some underplanted sites were more sheltered from extreme climatic conditions, and in some cases this improved survival of Douglas-fir seedlings. However, seedling growth rates were reduced compared with those on open sites probably due to lower light levels. Underplanting may help to improve establishment success of some species, particularly in exposed areas. However, the shelter benefits of underplanting must be carefully balanced against the trade-off with lower light, and underplanting is likely to be more successful where low canopy density is maintained.

Description: The recent emergence of Olive Quick Decline Syndrome in Italy, caused by Xylella fastidiosa, has drawn attention to the risks posed by this vector-borne bacterium to important crops in Europe (especially fruit trees and grapevine). Comparatively very little is known on actual and potential impacts of this pathogen in forests, in the native (North American) and introduced (European) regions, respectively. The present review aims to address important questions related to the threat posed by X. fastidiosa to European forests, such as the following: What are the symptoms, hosts and impact of bacterial leaf scorch caused by X. fastidiosa on trees in North America? Which forest tree species have been found infected in the introduction area in Europe? How does X. fastidiosa cause disease in susceptible hosts? Are there any X. fastidiosa genotypes (subspecies and sequence types) specifically associated with forest trees? How is X. fastidiosa transmitted? What are the known and potential vectors for forest trees? How does vector ecology affect disease? Is the distribution of X. fastidiosa, especially the strains associated with trees, restricted by climatic factors? Is disease risk for trees different in forest ecosystems as compared with urban settings? We conclude by pointing to important knowledge gaps related to all these questions and strongly advocate for more research about the Xylella-forest pathosystems, in both North America and Europe.

Description: This paper uses a dataset from Tanzania with information on consumption, income, and income shocks within and across family networks. Crucially and uniquely, it also contains data on the degree of information existing between each pair of households within family networks. We use these data to construct a novel measure of the quality of information both at the level of household pairs and at the level of the network. We also note that the individual level measures can be interpreted as measures of network centrality. We study risk sharing within these networks and explore whether the rejection of perfect risk sharing that we observe can be related to our measures of information quality. We show that households within family networks with better information are less vulnerable to idiosyncratic shocks. Furthermore, we show that more central households within networks are less vulnerable to idiosyncratic shocks. These results have important implications for the characterisation of the empirical failure of the perfect risk-sharing hypothesis and point to the importance of information frictions.

Description: The tropical montane cloud forest is one of the most biodiverse ecosystems on Earth and is one of the areas most threatened by anthropogenic disturbance. This study assessed the temporal impact on soil properties (organic carbon, total nitrogen, cation exchange capacity, bulk density) following establishment of native tree species in two degraded tropical montane cloud forest areas with different soil types and land-use intensities in south-east Mexico. In Pueblo Nuevo, Chiapas, Pinus chiapensis and Alnus spp. were established at two sites with humic Nitisols with low and moderate disturbance levels, respectively. In Xalapa, Veracruz, plum pine (Podocarpus matudae), American hornbeam (Carpinus caroliniana), Oaxaca walnut (Juglans pyriformis Liebm.), and sweetgum (Liquidambar styraciflua) were established on a grassland-covered humic Andosol with a high level of disturbance. After 16 years, soil properties had generally improved, although in the initial years after planting, the values declined, indicating a possible negative impact because of disturbance during tree establishment. Land-use intensity prior to tree establishment influenced the level of recovery in soil properties. The Pueblo Nuevo sites, with low to moderate disturbance levels, regained soil quality faster than the highly disturbed Xalapa site, despite better initial soil quality in the latter.

Description: Wood removed in Southwestern US forest restoration treatments currently has limited markets and thus low value. One important property of wood in structural products is its stiffness (measured as modulus of elasticity), which is known to vary systematically within trees. Directly measuring wood stiffness is expensive, time consuming and destructive. Therefore, we tested samples of ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) from northern Arizona destructively in bending and also non-destructively using acoustic velocity (AV) methods. In total, we tested multiple pith-to-bark small clear (2.54 × 2.54 × 40.64 cm) samples from up to four heights in 103 trees. We first measured the standing-tree AV of sample trees, then the AV of small clear samples, and finally measured wood stiffness using three point static bending tests. We found that a Michaelis–Menten curve was a good fit to the radial profile of wood stiffness, with a steep increase outward from the pith that approached an asymptote. The AV of small clear samples, coupled with measured volumetric density values, approximated the static modulus of elasticity values with high accuracy (r2 = 0.86). At the stand level, a model predicting standing tree AV from tree morphology fit the data well (r2 = 0.77). Results indicate that southwestern ponderosa pine contains outerwood with relatively high stiffness that could be suitable for structural products. However, when assessed using wood stiffness, the trees take a long time to reach maturity (~50 years) and thus the corewood proportion is large. AV measurements are a good way to assess variability within and among stands and thus could be employed to segregate the resource by expected stiffness values. Segregation could help identify stands not suitable for structural uses and direct them toward more appropriate products.

Description: We study whether crony governance can extend beyond economic policy to the targeting of state violence against citizens. Specifically, we examine the logic driving the choice of firm-level union representatives who were subjected to state repression by the 1976–1983 Argentine military junta. Using an original dataset, we find a positive, nonspurious, and robust correlation between labor repression and cronyism, measured by political, business, and social connections to the regime. Our results indicate that the number of firm-level union representatives victimized by the regime is three times higher for connected firms relative to nonconnected ones. The effect is pronounced in privately owned (as opposed to state-owned) firms, suggesting that the correlation is driven by cronyism for financial gain rather than ideology or information transmission. We show that connected firms benefited from violence against union representatives by subsequently having less strikes and a higher market valuation. Our findings highlight the pervasiveness of governmental cronyism, even in cases where one of the regime's main stated goals was to curb such behavior.

Description: The 17th Symposium on Systems Analysis in Forest Resources was held in Suquamish, Washington, United States on August 27–30, 2017. The goal of this international meeting was to bring together operations researchers, remote sensing scientists, and the government to facilitate the exchange and implementation of systems science in forestry and conservation. The essay that follows is a summary of the outcome of the Symposium, as well as an introduction to the eight research articles that were selected for publication in this Special Issue. Each of the papers was presented at the Symposium and has undergone rigorous peer review. The papers represent a broad disciplinary scope within system analysis ranging from forest economics and management science to remote sensing. The problems addressed within these disciplines also vary, from wildfire mitigation, supply-chain optimization, bioenergy logistics, and participatory forest planning to fuel assessment. The technical tools the authors applied to these problems are equally diverse: game theory, dynamic programming, stochastic optimization, multiobjective decision theory, structure-from-motion, and airborne laser scanning.

Description: In UK forestry, the synthetic pyrethroid insecticides alpha-cypermethrin and cypermethrin have been used for many years to provide protection for young trees planted on restock sites from damage by the large pine weevil, Hylobius abietis L. However, concerns over the toxicity of these insecticides to aquatic life if misused have led to a search for alternative forms of protection. This paper describes a detailed programme of efficacy experiments undertaken between 2009 and 2015 to find replacements for these products. Over 50 combinations of chemical and non-chemical approaches were tested on 16 different sites. Of the alternative synthetic insecticides tested, applications of 0.037 g a.i. stem−1 acetamiprid provided high levels of protection from Hylobius browsing damage on young Sitka spruce (Picea sitchensis (Bong.) Carrière) trees, without causing any phytotoxic symptoms, and gave comparable levels of protection to those achievable using alpha-cypermethrin or cypermethrin. Acetamiprid is less toxic to aquatic life than alpha-cypermethrin or cypermethrin and has not been linked to bee decline. Applications of 0.0129 g a.i. stem−1 chlorantraniliprole also showed promise, and this relatively low toxicity non-neonicotinoid insecticide merits further study. Although imidacloprid and thiacloprid also provided good levels of protection, their use in forests is not now permitted due to concerns over their potential impacts on bees and drinking water, respectively. Whilst the natural product insecticide spinosad, and the entomopathogenic fungal control agent Metarhizium anisopliae (Metschn.) Sorokin, gave only limited protection in our work, they may have some future potential if methods of deployment can be improved. Other chemical and non-chemical approaches tested, but found to be largely ineffective in UK conditions, included the natural product insecticides azadirachtin, maltodextrin and pyrethrins, the synthetic insecticides lambda-cyhalothrin and spirotetramat and a wide range of repellents, flexible stem coatings and physical barrier products. However, we conclude that physical barrier sleeves such as MultiPro® and BioSleeve® may have a limited role as a partial substitute for the use of insecticides in the UK in some circumstances, but only if on-site populations of Hylobius are predicted to be low.

Description: This paper studies how market signals—such as stock prices—can help alleviate the severity of the asymmetric information problem in credit and liquidity management. Asymmetric information hinders the ability of borrowers (firms, investment banks, etc.) to undertake profitable investment opportunities and to insure themselves against liquidity shocks. I show that on the equilibrium path creditors do not learn anything from market signals because they can use a menu of contracts to screen the different types of borrowers. However, by conditioning liquidity insurance on ex post price signals, creditors are able to provide the borrowers with better incentives for truth telling. At the same time, prices depend on the liquidity that creditors offer to the borrowers. This two-way feedback impacts the design of the optimal contract and potentially generates multiple equilibria in financial markets.

Description: To increase forest resilience to global change, forest managers are often directing forest stands towards a broader diversity of tree species. The small-leaved lime (Tilia cordata Mill.), a rare and scattered species in northwestern Europe, is a promising candidate for this purpose. Its life traits suggest a high resilience to climate change and a favourable impact on forest ecosystem services. This study used a dendroecological approach to assess how lime tree radial growth had responded to the past climatic change. First, 120 lime trees from nine sites were selected in southern Belgium based on criteria adapted to the rareness of the species. Chronology quality was assessed and resulting tree-ring series were validated at site and region levels. Second, a range of dendrochronological methods was used to analyze the changes over time in the variability and long-term trends of lime tree growth and their relation to climate during the period 1955–2016. Last, behaviour of lime trees was compared with that of beech from the same region and time period. For this purpose, the same methodology was applied to an additional beech tree-ring dataset (149 trees from 13 sites). Beech is the climax tree species of the region, but is known to be drought-sensitive and has shown weaknesses in the current climate. The quality of our tree-ring series attests that dendroecological investigation using rare and scattered species is possible, opening the way to further analysis on other such lesser-known forest tree species. The analysis showed that the small-leaved lime had been resilient to the past climatic change in multiple ways. Lime growth increased during the preceding decades despite an increased frequency and intensity of stressful climatic events. Lime growth quickly recovered in the years following the stresses. The growth–climate relationships were either stable over time or had a positive evolution. The behaviour of lime contrasted strongly with that of beech. Lime performed better than beech in every analysis. Small-leaved lime is thus a serious candidate for addressing climate change challenges in the region. It should be considered by forest managers planning to improve the sustainability and resilience of their forests, in particular in vulnerable beech stands.

Description: Diameter at breast height is a standard method for characterizing trees and ultimately forests over large geographical scales. Expressing the cross-section of a tree stem with a diameter measurement has inherent errors, as stems are not perfect conical frustums. Diameter suffices as an approximation, since methods for the exact cross-sectional area of a stem are infeasible in practice. There are other primary sources of error in diameter at breast height measurements: diameter measurement error and breast height measurement error. This paper addresses the latter in the context of an automated measurement system using 3D photography. We consider breast height estimation a fundamental component in such systems, as errors in measurement height can precipitate significant errors in stand-level attribute estimation as diameter changes along the height of the stem because of taper. We evaluate the efficacy of breast height estimation using stereo photogrammetry by fitting a planar surface to the ground and elevating the plane to breast height. Results from a validation test on 560 observations show that breast height can be estimated with a root mean squared error of 10.20 cm within 10 m from the camera and 13.36 cm within 20 m from the camera on flat terrain in varying levels of stem density. Study Implications Increasing the level of automation in forest operations is one approach to address workforce attrition and safety issues in the industry. Automated tree measurement and mapping systems present an opportunity to reduce operational costs by providing machine operators with necessary information to carry out silvicultural prescriptions and eliminate the need for individual tree marking in certain situations. In order to maintain trust between landowners and harvesting contractors, it is imperative that automatic measurement systems are rigorously tested to determine that measurement accuracy is within acceptable limits. Breast height measurement error is often overlooked as a source of error in estimating diameter at breast height. However, accurate breast height estimation is a necessary prerequisite for reliable, consistent, and precise diameter at breast height measurement. The capacity of machine vision systems to automate forest inventory and monitoring tasks is increasing and can help managers achieve sustainable forestry objectives on more acres in less time.

Description: The restoration of forest structure and function is increasingly being used in boreal forests in order to halt the loss of biodiversity. Often ecological restoration is aimed at increasing the volume of dead and dying trees to enhance the biodiversity of deadwood-dependent organisms, but it may also increase population sizes of pest bark beetle species, even several years following restoration. Herein, we used a large-scale restoration experiment in Northern Sweden to assess the 5 years post-restoration effects of restorative gap cutting and prescribed burning on the populations of a set of economically harmful pest bark beetles (Ips typographus, Polygraphus poligraphus, Tomicus piniperda and Pityogenes chalcographus) and the most important predators of bark beetles, Thanasimus spp. In addition, we assessed the effects of forest stand characteristics at stand and landscape scale on the abundance of I. typographus. Five years post-restoration, gap-cut stands supported the highest abundances of P. poligraphus and contained the highest count of spruce trees newly attacked by bark beetles. By contrast, prescribed burning generally sustained the lowest abundances of pest bark beetles, especially I. typographus and P. poligraphus, and the highest abundance of their natural predators Thanasimus spp. The population abundance of I. typographus was also positively affected by the area of clear cuts within a 500 m radius from the stand. In conclusion, prescribed burning appears to be a safer method for ecological restoration than gap cutting in the long-term. According to our results, a risk of a local bark beetle outbreak still remains 5 years following the initiation of ecological restoration treatments on spruce-dominated mature gap-cut stands.

Description: We study financial stability regulation in an environment with pecuniary externalities and where banks face both a liability choice (between private money creation and long-term borrowing) and an asset choice (between liquid and illiquid investments). Return risk on illiquid assets gives rise to liquidity risk, because banks that learn to have low future returns find themselves unable to roll over “money-like” debt. Privately optimal borrowing and investment decisions by banks lead, in general, to socially inefficient outcomes. The nature of inefficiency depends critically on the degree to which liquidity risk is systemic: When risk is highly systemic, banks hold the socially optimal amount of liquid assets, but create an excessive amount of money and overinvest in risky assets; when risk is not highly systemic, banks hold too little liquidity, create insufficient private money, and underinvest in risky assets. Quantity- and price-based regulations to address the identified inefficiencies are discussed.

Description: ‘Analog’ forestry is a novel silvicultural approach for reforestation of degraded land that seeks to establish trees that are analogous in structure and ecological function to the original climax or subclimax vegetation of the region where they are planted. Analog forestry aims to strengthen rural communities, both socially and economically, with tree plantings of high biodiversity, which provide commercial products and resiliency, while avoiding agrochemicals and fossil fuels. The latter links this strategy to climate change mitigation and adaptation strategies, but there has been little analysis comparing the potential for above- and below-ground carbon storage in analog forests, as compared with more typical reforestation efforts via single-species plantations. We present the results of a study to estimate carbon sequestration levels, above- and below-ground, from an experimental analog forest system and a teak (Tectona grandis L.f.) plantation system, in comparison with a degraded pasture system. The study found that the analog and teak plantation forest systems stored higher quantities of total carbon (178 and 141 t C ha−1, respectively), when compared with a degraded pasture system (124 t C ha−1). However, the teak plantation had decreased soil carbon stocks, relative to the degraded pasture. The analog forest had the best balance of both above- and below-ground carbon stored over the 17-year study period and provided a more diverse array of timber and non-timber forest products when compared with the teak plantation. This suggests that analog forestry could be a viable social–ecological approach to carbon storage and reforestation in the study region and other places with large areas of degraded pasture and a good understanding of the structure and function of the original vegetation.

Description: Loblolly pine is a major fibre source for the pulp and paper industry. Here we developed the first nonlinear models to predict the within-tree and regional variation of tracheid length and width for planted loblolly pine. Data were obtained from macerated tracheids and near-infrared spectroscopy calibration models from trees sampled in 109 stands across the southeastern United States. The fixed effects for the final tracheid length model, which included cambial age, height of disk within tree, and physiographic region, explained 71 percent of the variation with root mean square error (RMSE) of 0.28 mm, while the fixed effects for the final tracheid width model explained 57 percent of the variation with RMSE of 1.4 μm. There was significant variation in tracheid properties across the growing regions. Tree maps showing within-tree variability in tracheid properties were produced. Five simulated scenarios were compared using the models developed, with mean tracheid dimensions calculated on a whole-tree basis at a first and second thinnings, and at final harvest. Also from the final harvest, the tops of trees, and outerwood chips produced during lumber manufacturing were also simulated. For the whole tree scenarios, both mean tracheid length and width increased with age, increasing from 2.24 mm and 40.5 μm (age 12), to 2.51 mm and 41.3 μm (age 18), and to 2.73 and 41.8 μm at age 25, respectively. The tops of the trees at age 25 had a mean tracheid length of 2.46 mm and a mean width of 41.0 μm, while the chips had a mean tracheid length of 3.13 mm and a mean width of 42.5 μm. Due to the models representing samples collected from across the southeastern United States, and their relatively high precision, they are suitable for incorporation into growth and yield systems allowing for prediction of tracheid properties.

Description: Light detection and ranging (LiDAR) is used to estimate tree, stand and forest characteristics across large geographic areas. In most analyses, several independent LiDAR-based allometric equations are built to predict various forest attributes. When each forest attribute is estimated independently, there is potential for predictions of forest attributes that are not mathematically or biologically consistent. Combined allometric equations can be considered a system of equations describing the stand structure. Mathematically compatible and biologically meaningful estimates can be derived by estimating key structural variables and solving for other components, rather than estimating each forest attribute separately and independently. In this study, we propose the development of a system of allometric equations describing the relationship between volume per unit area, Lorey’s average height, basal area, quadratic mean diameter (QMD) and density. The system of allometric equations is derived from extensive field data. Key structural attributes are predicted using LiDAR metrics, and the remaining structural variables are solved for using the system of allometric equations. Predictions of structural attributes from the system of allometric equations are compared with predictions from independent LiDAR-derived prediction equations. Results showed that applying the systems approach can provide reasonable and compatible estimates with lower required sample sizes, especially when multiple attributes need to be considered simultaneously. Testing the portability of the systems approach in more complex stand structures and across different LiDAR acquisitions will be required in the future.

Description: We study whether employment history provides information about a worker’s “work attitude”, that is, the tendency to act cooperatively and reliably in the workplace. We conjecture that, holding all else equal, frequent job changes can indicate poor work attitude and that this information is transmitted through employment histories. We find support for this hypothesis across three studies that employ complementary laboratory, field, and survey experiments, as well as in labor market panel data. First, a tightly controlled laboratory labor market experiment demonstrates that prior employment information allows employers to screen for reliable and cooperative workers and that these workers obtain better employment outcomes. Secondly, we conduct a field experiment that varies the frequency of job changes in applicants’ resumes and find that those with fewer job changes receive substantially more callbacks from prospective employers. Thirdly, a survey experiment with human resources professionals confirms that the resume manipulations in the field study create different perceptions of work attitude and that these largely account for the callback differences. Finally, we find evidence consistent with our hypothesized relationships in empirical labor market data. Our work highlights the potential importance of job history as a signal of work attitude in labor markets, and points to a potential cost of frequent job changes.

Description: To minimize the cost of making decisions, an agent should use criteria to sort alternatives and each criterion should sort coarsely. To decide on a movie, for example, an agent could use one criterion that orders movies by genre categories, another by director categories, and so on, with a small number of categories in each case. The agent then needs to aggregate the criterion orderings, possibly by a weighted vote, to arrive at choices. As criteria become coarser (each criterion has fewer categories) decision-making costs fall, even though an agent must then use more criteria. The most efficient option is consequently to select the binary criteria with two categories each. This result holds even when the marginal cost of using additional categories diminishes to 0. The extensive use of coarse criteria in practice may therefore be a result of optimization rather than cognitive limitations. Binary criteria also generate choice functions that maximize rational preferences: decision-making efficiency implies rational choice.

Description: Measuring and understanding the evolution of wealth inequality is a key challenge for researchers, policy makers, and the general public. This paper breaks new ground on this topic by presenting a new method to estimate and study wealth inequality. This method combines fiscal data with household surveys and national accounts in order to provide annual wealth distribution series, with detailed breakdowns by percentiles, age, and assets. Using the case of France as an illustration, we show that the resulting series can be used to better analyze the evolution and the determinants of wealth-inequality dynamics over the 1970–2014 period. We show that the decline in wealth inequality ends in the early 1980s, marking the beginning of a rise in the top 1% wealth share, though with significant fluctuations due largely to asset price movements. Rising inequality in savings rates coupled with highly stratified rates of returns has led to rising wealth concentration in spite of the opposing effect of house price increases. We develop a simple simulation model highlighting how changes in the combination of unequal savings rates, rates of return, and labor earnings that occurred in the early 1980s generated large multiplicative effects that led to radically different steady-state levels of wealth inequality. Taking advantage of the joint distribution of income and wealth, we show that top wealth holders are almost exclusively top capital earners, and increasingly fewer are made up of top labor earners; it has become increasingly difficult in recent decades to access top wealth groups with one's labor income only.

Description: Agricultural and other physically demanding sectors are important sources of growth in developing countries, but prevalent diseases such as malaria can adversely impact the productivity and labor supply of workers. We estimate the impact of malaria infection on worker earnings, labor supply, daily productivity, and task selection by using a phased-in design where we randomize the study week in which piece-rate workers at a large sugarcane plantation in Nigeria are offered malaria testing and treatment. Two estimation strategies indicate a significant and substantial intent to treat effect of the intervention. The program increases worker weekly earnings by 11%–13% over the weeks following the offer, depending on the reference period, estimated using a between-worker estimator that exploits the experimental design. A within-worker estimate provides similar but smaller estimates of 8%–10%. We identify different pathways through which this effect occurs. For workers who test positive for malaria, the treatment of illness principally increases labor supply, leading to higher earnings. For workers who test negative, the health information leads to increased earnings via augmented daily productivity. This productivity response arises, in part, from selection into higher return tasks within their job at the plantation. The results underline the importance of medical treatment but also of improved access to information about one's health status, as the absence of either leads workers to work less or choose lower return tasks when working.

Description: Labor market outcomes demonstrate considerable variation between and within skill groups. We construct a general equilibrium model with incomplete markets and exogenous differences that matches these facts. We study the role of exogenous heterogeneity in choosing the optimal replacement rate and the maximum benefit for an unemployment insurance (UI) system. The optimal average replacement rate is 27%, compared to 0% in a model without exogenous heterogeneity. The relatively generous choice is due to the redistributive role of UI, which is a manifestation of two elements. First, workers who are unemployed more often receive positive net transfers from the UI system because they draw resources more frequently. Second, the existence of a cap on benefits makes UI progressive. Our main result holds in the presence of a generous progressive taxation system.

Description: Growth response to thinning has long been a research topic of interest in forest science. This study presents the first 3–4 years of response of loblolly pine (Pinus taeda L.) growth to thinning at different intensities. Data were collected from the East Texas Pine Research Project’s region-wide loblolly pine thinning study, which covers a wide variety of stand conditions. Four treatments, light, moderate, and heavy thinning, respectively having 370, 555, and 740 residual trees per hectare after thinning, and an unthinned control, were included. Individual tree diameter at breast height (dbh) and total height were recorded annually for the first 3–4 years after thinning. Results indicate significant differences between treatments in dbh growth in each year after thinning, as well as for all years combined. Each thinning treatment had significantly greater dbh growth than the control in the first growing season with this positive response being more evident in the case of the heavier thinning or at the later years post-thinning. Conversely, the thinning effect on tree height growth was initially negligibly negative, then becoming positive after 2–4 years, with the heavier thinning becoming positive sooner. Tree size class, assigned based on prethinning dbh, had a significant effect on both dbh and height growth responses. Compared to the control, small trees had a greater response both in dbh and in height growth than the medium and large trees over the measurement period. At the stand level, the heavier thinning had significantly less stand basal area per hectare, but the difference in stand basal area per hectare between the thinned and the unthinned plots decreased with years post-thinning. Results from this study can improve our understanding in thinning effects and help forest managers make accurate decisions on silvicultural regimes.

Description: Foreign creditors’ business cycles influence both the process and the outcome of sovereign debt restructurings. We compile two datasets on creditor committees and chairs and on creditor business and financial cycles at the restructurings. We find that when creditors experience high GDP growth, restructurings are delayed and settled with smaller haircuts. To rationalize these stylized facts, we develop a theoretical model of sovereign debt with multiround renegotiations between a risk averse sovereign debtor and a risk averse creditor. The quantitative analysis of the model shows that high creditor income results in both longer delays in renegotiations and smaller haircuts. Our theoretical predictions are supported by data.

Description: Forests of the world constitute one-third of the total land area and are critical for e.g. carbon balance, biodiversity, water supply and as source for bio-based products. Although the terrain within forest land has a great impact on accessibility, there is a lack of knowledge about the distribution of its variation in slope. The aim was to address that knowledge gap and create a globally consistent dataset of the distribution and area of forest land within different slope classes. A Geographic Information System (GIS) analysis was performed using the open-source QGIS, GDAL and R software. The core of the analysis was a digital elevation model and a forest cover mask, both with a final resolution of 90 m. The total forest area according to the forest mask was 4.15 billion hectares whereof 82 per cent was on slope  30°. Out of the major forestry countries, China had the largest proportion of forest steeper than 15° followed by Chile and India. A sensitivity analysis with 20 m resolution resulted in increased steep areas by 1 per cent point in flat Sweden and by 11 per cent points in steep Austria. In addition to country-specific and aggregated results of slope distribution and forest area, a global raster dataset is also made freely available to cover user-specific areas that are not necessarily demarcated by country borders. Apart from predicting the regional possibilities for different harvesting equipment, which was the original idea behind this study, the results can be used to relate geographical forest variables to slope. The results could also be used in strategic forest fire fighting and large-scale planning of forest conservation and management.

Description: Forest harvesting operations with heavy machinery can lead to significant soil rutting. Risks of rutting depend on the soil bearing capacity which has considerable spatial and temporal variability. Trafficability prediction is required in the selection of suitable operation sites for a given time window and conditions, and for on-site route optimization during the operation. Integrative tools are necessary to plan and carry out forest operations with minimal negative ecological and economic impacts. This study demonstrates a trafficability prediction framework that utilizes a spatial hydrological model and a wide range of spatial data. Trafficability was approached by producing a rut depth prediction map at a 16 × 16 m grid resolution, based on the outputs of a general linear mixed model developed using field data from Southern Finland, modelled daily soil moisture, spatial forest inventory and topography data, along with field measured rolling resistance and information on the mass transported through the grid cells. Dynamic rut depth prediction maps were produced by accounting for changing weather conditions through hydrological modelling. We also demonstrated a generalization of the rolling resistance coefficient, measured with harvester CAN-bus channel data. Future steps towards a nationwide prediction framework based on continuous data flow, process-based modelling and machine learning are discussed.

Description: China’s rapid growth has been driven by policy reforms that significantly reduce market frictions. Policy reforms are determined by the government according to its own politico-economic considerations. This paper embeds these politico-economic considerations in a macro model of China to endogenously study government policies, market frictions, and economic growth. In the model, an elite runs the government and maximizes its own incomes, facing a political constraint: getting enough supporters. The government provides high enough incomes to state workers in order to gain their support. It also controls capital allocations in the state and the private sector to balance between keeping enough supporters and extracting more taxes from the private sector. These policies initially generate rapid growth accompanied by declining labor and capital market frictions but in the long run, keep the frictions persistent, which are harmful to growth. The calibrated model can quantitatively account for salient aspects of China’s recent development and provide predictions for future dynamics.

Description: Natural regeneration cannot be effectively evaluated by tree density because of spatial heterogeneity typically observed. A proper interpretation of natural regeneration will consider some evaluation of area stocked. However, stocking estimates for natural regeneration are plot-size-dependent. Stocking at the 1-milacre scale is not generally comparable to that on a 4-milacre scale unless a generalized relation with stand density can be established. A generalized relation was first suggested to hold in a paper by Lynch and Schumacher (1941), but this has not been confirmed in subsequent studies. The Lynch and Schumacher hypothesis of a generalized regeneration density-stocking relation across plot size was tested using observations on 60 stands. Results were consistent with Lynch and Schumacher (1941). With evidence of a well-defined relation for plots ranging from 1 to 10 milacres, it appears possible to approximate, for ponderosa pine and associated species, the natural regeneration stocking percentage for a range of stocking standards based solely on observations of regeneration density. Confidence intervals were derived for a range of stocking standards in English units from 1 to 10 milacre and for metric units from 0.0005 hectares to 0.0040 hectares.

Description: In forest inventory, traditional ground-based resource assessments are often expensive and time-consuming forcing managers to reduce sample sizes to meet budgetary and logistical constraints. Small area estimation (SAE) is a class of statistical estimators that uses a combination of traditional survey data and linearly related auxiliary information to improve estimate precision. These techniques have been shown to improve the precision of stand-level inventory estimates in loblolly pine plantations using lidar height percentiles and thinning status as covariates. In this study, the effects of reduced lidar point-cloud densities and lower digital elevation model (DEM) spatial resolutions were investigated for total planted volume estimates using area-level SAE models. In the managed Piedmont pine plantation conditions evaluated, lower lidar point-cloud densities and DEM spatial resolutions were found to have minimal effects on estimates and precision. The results of this study are promising to those interested in incorporating SAE methods into forest inventory programs.

Description: In many matching markets, bargaining determines who matches with whom and on what terms. We experimentally investigate allocative efficiency and how subjects’ payoffs depend on their matching opportunities in such markets. We consider three simple markets. There are no information asymmetries, subjects are patient, and a perfectly equitable outcome is both feasible and efficient. Efficient perfect equilibria of the corresponding bargaining game exist, but are increasingly complicated to sustain across the three markets. Consistent with the predictions of simple (Markov perfect) equilibria, we find considerable mismatch in two of the markets. Mismatch is reduced but remains substantial when we change the nature of bargaining by moving from a structured experimental protocol to permitting free-form negotiations, and when we allow players to renege on their agreements. Our results suggest that mismatch is driven by players correctly anticipating that they might lose their strong bargaining positions, and by players in weak bargaining positions demanding equitable payoffs.

Description: We explore the implications of managing forests for the dual purpose of sequestering carbon and producing timber, using a model of the forest sector that includes a Hartman-based representation of forest owners’ behaviour as well as heterogeneity in environmental conditions. We focus on France, where recent policies aim at increasing the carbon sink and where the diversity of forests makes an analysis of spatial dynamics relevant, and we use recent estimates of the shadow price of carbon consistent with the country’s climate commitments. Results suggest that forests may sequester up to 550 MtCO2eq by 2100, driven by changes in harvest levels and species choice, whilst rotation lengths increase overall. A spatial analysis reveals a high spatial variability for these trends, highlighting the importance of considering the local context. Changes in investment patterns affect the spatial distribution of forest cover types: by the end of the century, a majority of regions comprise a larger share of older, multiple-species and mixed-structure forests. Whilst such an evolution may present benefits in terms of biodiversity, ecosystem services provision and resilience, it raises questions regarding the adequacy of such developments with current forest policy, which also aims at increasing harvest levels. An overall mitigation strategy for the forest sector would likely include incentives to energy and material substitution in downstream industries, which we did not consider and may interact with sequestration incentives.

Description: One method of controlling dune encroachment is afforestation, which may result in biodiversity loss because of habitat change and adverse effects of trees on ecosystem functioning. We carried out a study on the effects of planting discrete areas with Tamarix aphylla (L.) Karsten trees, over 50 years ago, in a semiarid dunefield in the northern Negev, Israel. We surveyed the vegetation and sampled litter and soil in five microhabitats formed by this afforestation scheme. Afforestation had spatially and functionally hierarchical effects on vegetation and plant diversity. The strongest effect was associated with land-use change, showing reduced species richness (by 30–50 percent) and litter production following afforestation. The second strongest effect was associated with salt accumulation in T. aphylla leaves and litter, which increases soil salinity under T. aphylla canopies by 4–5, forming “salinity islands,” and leading to over 30 percent decrease in plant cover and aboveground biomass. The assumed effect of trees in blocking solar irradiance and wind was observed only outside canopies and had a weak impact on plant cover. Therefore, afforestation can increase plant diversity at the regional scale, but at the local (microhabitat) scale it has an overall adverse effect on measured ecosystem functions.

Description: We propose a novel measure of goodness of fit for stochastic choice models, that is, the maximal fraction of data that can be reconciled with the model. The procedure is to separate the data into two parts: one generated by the best specification of the model and another representing residual behavior. We claim that the three elements involved in a separation are instrumental in understanding the data. We show how to apply our approach to any stochastic choice model and then study the case of four well-known models, each capturing a different notion of randomness. We illustrate our results with an experimental data set.

Description: Agents need to be motivated to develop ideas and to share information regarding their potential value. When the agents fail to agree on which alternative to implement, the principal needs to decide how to resolve the disagreement. When the agents’ information is soft, favoring one of the agents in the case of disagreement is always optimal in the present setting. In contrast, if the information is hard, a balanced treatment of the agents is preferred to encourage competition. The reason for the difference is the high cost of sustaining both informative communication and effort in a balanced organization.

Description: Invertebrate forest pests and pathogens can cause considerable economic losses and modern patterns of trade have facilitated the international movement of pest species on an unprecedented level. This upsurge in trade has increased the pathways available to high risk species, facilitating entry and potential establishment in nations where they were previously absent. To support policy and pest prioritization, pest risk analyses are conducted to decide ‘if’ and ‘how’ pests should be regulated in order to prevent entry or establishment; however, they cannot be carried out for every potential pest. This paper utilizes a hierarchical clustering (HC) approach to analyse distribution data for pests of Sitka spruce (Picea sitchensis (Bong.) Carr.) in order to identify species of high risk to Ireland, as well as potential source regions of these pests. The presence and absence of almost a 1000 pests across 386 regions globally are clustered based on their similarity of pest assemblages, to provide an objective examination of the highest risk pests to Irish forestry. Regional clusters were produced for each taxon analysed including the Coleoptera, Diptera, Hemiptera, Hymenoptera, Nematoda, Lepidoptera and the Fungi. The results produced by the HC analysis were interpreted with regard to biological realism and climate. Biologically meaningful clusters were produced for each of the groups, except for the Diptera and Nematoda, and each of the species analysed were ranked within their group by a quantitative risk index specific to the island of Ireland. The impact of uncertainty in the distribution data is also examined, in order to assess its influence over the final groupings produced. The outputs from this analysis suggest that the highest risk pests for Ireland’s Sitka spruce plantations will originate from within Europe. Ultimately, Ireland could benefit from seeking regulation for some of the higher ranking pests identified in this analysis. This analysis provides the first of its type for Sitka spruce, as well as its application in Ireland. It also serves to highlight the potential utility of HC as a ‘first approach’ to assessing the risk posed by alien species to hitherto novel regions.

Description: The homeownership rate in Germany is one of the lowest among advanced economies. To better understand this fact, we evaluate the role of specific housing policies that tend to discourage homeownership. In comparison to other countries with higher homeownership such as the United States, Germany has an extensive social housing sector with broad eligibility criteria, high transfer taxes when buying real estate, and no tax deductions for mortgage interest payments by owner-occupiers. We build a life-cycle model with uninsurable income and housing risks and endogenous homeownership in order to quantify the policy impact on homeownership and welfare. Adjusting all three policies has a strong impact on housing tenure choices, closing the gap in homeownership rates between Germany and the United States by about two thirds. At the same time, household welfare would be reduced by moving to a policy regime with low transfer taxes, but it would improve in the absence of social housing, in particular, when coupled with housing subsidies for low-income households.

Description: Regular biomass estimations for natural and plantation forests are important to support sustainable forestry and to calculate carbon-related statistics. The application of remote sensing data to estimate biomass of forests has been amply demonstrated but there is still space for increasing the efficiency of current approaches. Here, we investigated the influence of field plot and sample sizes on the accuracy of random forest models trained with information derived from Pléiades very high resolution (VHR) stereo images applied to plantation forests in an arid environment. We collected field data at 311 locations with three different plot area sizes (100, 300 and 500 m2). In two experiments, we demonstrate how plot and sample sizes influence the accuracy of biomass estimation models. In the first experiment, we compared model accuracies obtained with varying plot sizes but constant number of samples. In the second experiment, we fixed the total area to be sampled to account for the additional effort to collect large field plots. Our results for the first experiment show that model performance metrics Spearman’s r, RMSErel and RMSEnor improve from 0.61, 0.70 and 0.36 at a sample size of 24–0.79, 0.51 and 0.15 at a sample size of 192, respectively. In the second experiment, highest accuracies were obtained with a plot size of 100 m2 (most samples) with Spearman’s r = 0.77, RMSErel = 0.59 and RMSEnor = 0.15. Results from an analysis of variance type-II suggest that the overall most important factors to explain model performance metrics for our biomass models is sample size. Our results suggest no clear advantage for any plot size to reach accurate biomass estimates using VHR stereo imagery in plantations. This is an important finding, which partly contradicts the suggestions of earlier studies but requires validation for other forest types and remote sensing data types (e.g. LiDAR).

Description: Prosopis chilensis (Molina) Stuntz (Leguminosae) is a valuable native species in Argentina included in the Prosopis Management Programme. Natural provenances show important height and shape differentiation throughout their distribution in the Monte Desert. The availability of progeny trials provides an opportunity to quantify genetic differentiation among provenances and test the relative importance of demographic vs adaptive processes on morphological variation. We quantified both genetic and quantitative differentiation of neutral markers and five economically important traits, respectively, among four provenances in a provenance-progeny trial. We aimed to quantify the genetic basis of variations in height, basal diameter, tree shape, spine length and biomass. Two hypotheses were tested: (1) economically important traits have significant heritability, and (2) the phenotypic variation among provenances is the result of local adaptation to particular environmental conditions. Our results indicate that most morphological variation was found among individuals within families (~95 per cent). The h2 estimates were heterogeneous among traits and ranged from low (0 for number of stems) to moderate (0.22 and 0.28 for spine length and biomass, respectively). Variance among families (~5 per cent) was evenly distributed within and among provenances. Morphological differentiation among provenances was low, but significant, and could be attributed mainly to individuals from Villa Unión. Based on molecular markers, genetic differentiation among provenances was low and significant (FST = 0.03; P = 5 × 10−4) but was able to differentiate the groups from Villa Unión, Fiambalá and Mogna-Chilecito. Neutrality tests were conducted using the FST–QST test and DJSOST and δGREGORIUS alternative coefficients of differentiation. Neutrality tests yielded no evidence of local adaptation and were rather consistent in showing a trend toward stabilizing selection, particularly for spine length. The selection strategy for breeding programmes should depend on the trait to be improved and should consider both provenance and familiar information. Considering an intra-familiar ranking is encouraged in order to maximize the genetic gain. Additionally, in order to recover germplasm provenance diversity, based on morphological and microsatellite results, our recommendation would be to include seeds from individuals from at least the Villa Unión, Fiambalá and Mogna-Chilecito areas.

Description: Soil organic matter is major terrestrial pool for soil organic carbon (C) and nitrogen (N), and their decomposition is sensitive to vegetation and climate change. Integrated nutrient management (INM) deals with the combined application of chemical fertilizers and organic manures for nutritional requirement of crops and avoid the adverse effect of long-term application of chemical fertilizer on crop production and their sustainability. The present study was carried out to investigate the influence of different nutrient sources on soil C mineralization and inorganic N pools in a Terminalia chebula Retz, based on a agroforestry system. The results showed that the highest CO2 evolution was recorded in 100 percent INM and minimum in farmyard manure treatment after 120 days of incubation. Inorganic N was higher under the agroforestry system than under the open system. Among the different nutrient sources, the highest inorganic N was recorded in a 100 percent INM nutrient source and minimal in wheat straw treatment. The yield of turmeric was higher under the T. chebula-based agroforestry system (20.87 t ha–1) than under the open system (19.27 t ha–1). Results suggest that agroforestry systems using the INM approach can enhance C mineralization and inorganic N concentration with improved crop productivity in the Himalayan foothills. Study Implications: Fertilizer has been used since ancient times, and if well managed it can be an asset, promoting sustainable agriculture and increasing crop production, particularly for smallholder farmers in the Himalayan region of India. We compared fertilizer application practices under an agroforestry system in a representative Himalayan region of India. The majority of farmers in the region of the Himalayan foothills having marginal land and they are not able to produce optimum food grains for their requirement. However, their demands are increasing day by day, so to fulfill their demand, they have to adopt agroforestry. Agroforestry may be fulfilling their demand in terms of food, fuel, fodder, and other intangible benefits. Moreover, to increase the production under agroforestry, we have to apply organic and inorganic fertilizer in the soil either as the sole application or as a combination of these fertilizers. The application of these fertilizers will improve the productivity and fertility of land, especially carbon mineralization and inorganic nitrogen. These two soil properties are important to study because these are limiting to land productivity. In addition, efforts to improve integrated nutrient management in the Himalayan region of India would strengthen farmers’ incomes by strengthening land fertility and productivity. The rapid increase in human population over the last century is putting a massive pressure on existing resources, namely soil and water, resulting in environmental degradation in some regions around the world. As productive land becomes scarce, marginalized farmers are pushed into fragile croplands and forest lands unsuitable for modern agriculture which, in turn, is vulnerable, to degradation. If the present trend in population growth persists, pasture and forest lands will be further reduced (Satterthwaite et al. 2010). At this stage, the value of growing trees becomes more significant, and participation in tree planting schemes should be encouraged. However, this option is most feasible when combined with agriculture. As a result, agroforestry is an important management strategy that not only helps to meet the world food requirements but also helps to protect soil from degradation (Ram et al. 2017) and can enhance soil organic matter levels by adding the quantity of above- and below-ground organic matter inputs to soils (Nair et al. 2009, Marone et al. 2017).

Description: Longleaf pine (Pinus palustris Mill.) is frequently planted on former agricultural fields throughout the southeastern United States. Limited information is available on the long-term growth and yield as well as stem quality of longleaf pine growing on these sites with and without midrotation fertilization. The objectives of this study were (1) to determine the growth rates, wood yields, and stem quality of old-field longleaf pine and (2) to quantify growth improvements provided by midrotation fertilization. Study sites were established on former agricultural fields in Screven and Tift County, Georgia in unthinned longleaf pine stands planted during December 1986. Three treatments including a control, single full dose, and split dose of nitrogen, phosphorus, and potassium were applied prior to thinning. Assessments of diameter at breast height, height growth, volume, green weight, and basal area at both sites were conducted at ages 21, 23, 27, 30, and 32. After 32 years, results indicated no statistically significant improvements of any growth parameters compared to the control in relation to midrotation fertilization treatments, and stem defects occurred in approximately 29–35 percent of trees. The fast growth rate and low nutrient demand of longleaf pine on these sites obviate the need for midrotation fertilization.

Description: Providing estimable sufficient statistics to give policy prescriptions has become a widespread approach, a well-known limitation of which is the endogeneity of sufficient statistics to the policy. Using optimal tax policy as our field of application, we highlight a new source of endogeneity. It arises under multidimensional heterogeneity, because optimal tax formulas are then expressed as functions of weighted means of sufficient statistics computed at the individual level and the weights are endogenous to the tax policy. We analytically show that ignoring these composition effects leads to underestimate the optimal linear tax and, under a restrictive set of assumptions, the optimal nonlinear tax as well. In the latter case, we use an improved tax perturbation approach to study composition effects without these assumptions. Numerical simulations on US data suggest the optimal tax rate may be underestimated by 6 p.p. for high incomes levels. We also relate our tax perturbation method to the first-order mechanism design method, both methods having hitherto been used separately to derive optimal tax schedules.

Description: We study a bilateral trade setting in which a buyer has private valuations over a multi-product seller’s inventory. We introduce the notion of an incentive-compatible market segmentation (IC-MS)—a market segmentation compatible with the buyer’s incentives to voluntarily reveal their preferences. Our main result is a characterization of the buyer-optimal IC-MS. It is partially revealing, comprised primarily of pooling segments wide enough to keep prices low but narrow enough to ensure trade over relevant products. We use our results to study a novel design problem in which a retail platform seeks to attract consumers by calibrating the coarseness of its search interface. Our analysis speaks directly to consumer privacy and the debate regarding product steering versus price discrimination in online retail.

Description: We present the first evidence on the role of occupational choices and acquired skills for migrant selection. Combining novel data from a representative Mexican task survey with rich individual-level worker data, we find that Mexican migrants to the United States have higher manual skills and lower cognitive skills than nonmigrants. Results hold within narrowly defined region–industry–occupation cells and for all education levels. Consistent with a Roy/Borjas-type selection model, differential returns to occupational skills between the United States and Mexico explain the selection pattern. Occupational skills are more important to capture the economic motives for migration than previously used worker characteristics.

Description: To investigate enemy pressure across the range of the pine processionary moth (Thaumetopoea pityocampa, Den. & Schiff.) as it spreads northwards in Europe because of climate change, a survey of 206 egg batches from historical and newly colonized areas at both the westernmost and the easternmost ends of the front was carried out in 2016–2018. Out of them, 97 egg batches were collected from nine locations in three regions in France and 109 from four localities in two regions in Bulgaria, both within historical and newly colonized ranges of the pest. The average number of eggs per batch collected in Bulgaria (226.6 ± 43.2) was higher than that in France (194.3 ± 50.1). However, the hatching percentage was higher in French samples, varying from 69.8 to 95.7, vs 49.8 to 85.2 per cent in Bulgarian samples. Four primary parasitoids (Ooencyrtus pityocampae, Baryscapus servadeii, Anastatus bifasciatus, Trichogramma sp.) and a hyperparasitoid (Baryscapus transversalis, found only in two regions of the historical range in Bulgaria) were identified. The oligophagous species B. servadeii was present at all sites within the historical range of the pest. In newly colonized areas, the impact of primary parasitoids on the host was distinctly low, suggesting that they lag behind the range expansion of pine processionary moth. In France, the most abundant species in the T. pityocampa parasitoid complex were B. servadeii in Ré Island and Orléans (97.3 and 87.4 per cent, respectively), and Trichogramma sp. (99.7 per cent) in a newly colonized locality in Fréhel. Ooencyrtus pityocampae prevailed in three of four Bulgarian localities (72.1 per cent in Sandanski, 89.7 per cent in Maglizh and 65.7 per cent in Sladak kladenets), whereas B. servadeii was the most abundant in Gega (75.4 per cent). Mortality of B. servadeii and O. pityocampae caused by the hyperparasitoid B. transversalis amounted to 4.8–6.2 per cent. The impact of predators on the pine processionary moth in the egg stage was negligible at most sites, reaching 12.5 per cent in only one site (Maglizh).

Description: Since 2009, deployment of full-sib families of loblolly pine (Pinus taeda L.) has gained prominence in the southeastern United States. To produce full-sib seed, a pollination bag is used to isolate female strobili from outside pollen contamination, and a known pollen is applied at the time of maximum female strobilus receptivity. The goal of this study was to compare prototype pollination bags made by PBS International to the industry standard kraft paper pollination bag with and without a support wire for female strobili survival and to assess their efficiency for mass production of controlled cross loblolly pine seed. A multiyear study compared 13 pollination bag types at more than nine seed orchard sites across the southeastern United States. There were significant differences among bag types for conelet survival at the time of bag removal that persisted until cone harvest 18 months later. Female strobili bagged in prototype PBS-I2 were over three times more likely to survive to cone harvest than strobili inside the traditional kraft pollination bag. Two of the PBS bag types had the highest estimated filled seed per bag. One PBS bag was faster to install and remove than the kraft paper bag with a support wire.

Description: Forest-restoration efforts are increasing in the western United States in response to realized and expected changes in climate and disturbance regimes. Managers are challenged to find practical and defensible targets to shift forest composition, structure, and spatial pattern to a more resistant and resilient state. The Northeast Washington Forest Vision 2020 project on the Colville National Forest presented an opportunity to map and use previously uncaptured mesic stand-level historical reference conditions to a large restoration project. We reconstructed historical forest conditions in 12 plots across a range of plant-association groups and mapped five restoration treatment units after implementation. We evaluated treatment effectiveness both in terms of meeting the prescriptions’ stated objectives and by similarity to observed reference conditions using metrics of density, species composition, clump-size patterns, and open-space patterns. We found that dry plant associations were historically dominated by distributed clumps of large shade-intolerant trees, whereas cold mesic plant associations were structured as a gap-matrix spatial pattern. Treatments were effective at meeting prescribed density and species-composition targets, but generally resulted in stands that were overly uniform or clumped compared to historical reference conditions.

Description: Widely distributed in Quebec, balsam fir (Abies balsamea (L.) Mill.) is highly vulnerable to wind damage. Recently, there has been a trend in forest management to increase the use of partial cuttings in naturally regenerating stands, leaving the remnant trees at increased risk of wind damage. In order to limit wind damage after partial cuttings, it is therefore important to find silvicultural practices that minimize the risk of wind damage in these fir stands. Our main objective was to find balsam fir-specific values of parameters to integrate into the wind risk model ForestGALES, in order to simulate the impact of different types of commercial thinning on wind damage risk, and to determine which practice potentially minimizes the risk in a naturally regenerated stand. An anemometer placed at canopy height and strain gauges attached to the trunks of balsam firs allowed us to measure the wind-induced bending moments experienced by a sample of balsam fir trees. This enabled the calculation of the turning moment coefficients specific to each of the trees in order to compare them with the ForestGALES model predictions and to adapt the model for balsam fir stands. The model was tested first with only tree diameter and height as input variables to calculate the turning moment coefficient, then with the addition of a competition index, and finally with the addition of crown dimensions. Wind climate parameters for prediction of the probability of damage were calculated using the Wind Atlas Analysis and Application Program airflow model. The model with the highest accuracy was then used to simulate two types of thinning and determine the impact on wind damage risk for each tree in the stand. According to the model’s predictions, thinning from below has a reduced risk of wind damage compared with thinning from above.

Description: Reputation concerns can discipline agents and generate good outcomes. But what if outcomes are not always observed? Infrequent observation can strengthen reputation incentives and encourage effort. By exerting effort when outcomes are more likely observed, an agent can improve her reputation and gain by “coasting” on this reputation by shirking when the audience is less likely to be observing her actions. Opportunities to coast can in fact lead to greater overall effort than constant observation. We consider Markov information structures and characterize the observability structure that maximizes efficient effort.

Description: We construct income-specific price indexes for the period from 2004 to 2016. We find substantial differences across income groups that arise during the Great Recession. The difference in annual inflation between the lowest quartile of the income distribution and the highest quartile was 0.22 percentage points for 2004–2007, 0.85 percentage points for 2008–2013, and 0.02 percentage points for 2014–2016. We find that product quality substitution and changes in the shopping behavior, margins mostly available to richer households, explain around 40% of the gap. Our evidence shows that not accounting for these differences in price indexes could lead to significant biases in the calculation of consumption and income inequality.

Description: Penalized splines have potential to decrease estimates of variance in forest inventories with a design-based population-level inference, and a model-based domain-level inference by decreasing the likelihood of a model misspecification. We provide examples with second-order (B2) B-splines and radial basis (RB) functions as extensions to a linear working model (WM). Bias was not prominent, yet greater with B2 and in particular with RB than with WM, and decreased with sample size. Important reductions in the variance of a population mean were achieved with both B2 and RB, but at the domain-level only with RB. The proposed regression estimator of variance generated estimates of variance being slightly smaller than the observed variance. A consistent and larger underestimation was seen with the popular difference estimator of variance. Study Implications: Forest inventories supported by light detection and range (LiDAR) data require—in the estimation phase—a model for linking LiDAR metrics to attributes of interest. Formulating a parametric model can be a challenge and unsatisfactory if the goodness of fit varies across the range of the attribute of interest. A semiparametric model provides more flexibility and lessens the chance of a model misspecification, albeit with the potential of overfitting. A penalty directed at reducing overfitting is required. A flexible semiparametric model is potentially also better suited for applications to small areas like stands than a parametric model. We demonstrate that important reductions in variance are indeed possible, but also that they depend on the form of the nonparametric part of the chosen model and the level of inference (population versus domains). With regard to practical application, reliable estimates of forest attributes at stand-level are of special interest within the scope of forest-management planning, as silvicultural treatments are always stand-oriented, at least with small-scale forestry under Central European conditions, and stand-related volume (basal area, tree density) belongs to the set of relevant parameters for management decisions regarding harvest and regeneration measures.

Description: We measured forest-floor accumulation in ponderosa pine forests of central Oregon and asked whether selected ecological functions of the organic layer were altered by thinning and repeated burning. Experimental treatments included three thinning methods applied in 1989 (stem only, whole tree, no thin—control) in factorial combination with prescribed burning (spring 1991 and repeated in 2002; no burn—control). Forest-floor depth and mass were measured every 4–6 years from 1991 to 2015. Without fire, there was little temporal change in depth or mass for thinned (270 trees ha−1) and control (560–615 trees ha−1) treatments, indicating balanced litterfall and decay rates across these stand densities. Each burn consumed 50–70 percent of the forest floor, yet unlike thinning, postfire accumulation rates were fairly rapid, with forest-floor depth matching preburn levels within 15–20 years. Few differences in forest-floor function (litter decay, carbon storage, physical barrier restricting plant emergence, erosion protection) resulted from thinning or burning after 25 years. An exception was the loss of approximately 300 kg N ha−1 because of repeated burning, or approximately 13 percent of the total site N. This study documents long-term forest-floor development and suggests that common silvicultural practices pose few risks to organic layer functions in these forests. Study Implications: Mechanical thinning and prescribed fire are among the most widespread management practices used to restore forests in the western US to healthy, firewise conditions. We evaluated their effects on the long-term development of litter and duff layers, which serve dual roles as essential components of soil health and as fuel for potential wildfire. Our study showed that thinning and burning provided effective fuel reduction and resulted in no adverse effects to soil quality in dry ponderosa pine forests of central Oregon. Repeated burning reduced the site carbon and nitrogen pools approximately 9–13 percent, which is small compared to C located in tree biomass and N in mineral soil. Litter accumulation after burning was rapid, and we recommend burning on at least a 15–20-year cycle to limit its build-up.

Description: Recently developed HANK models, which combine Heterogeneous Agents and New Keynesian frictions, have had a considerable impact on macroeconomics. However, due to the complexity of such models, the literature has focused on numerically solved models and therefore little is known about their general properties. This paper presents a tractable HANK model that integrates Search and Matching (SAM) frictions in the labor market. The model features an endogenous idiosyncratic earnings risk, which may be procyclical or countercyclical. When this risk is countercyclical, which we argue is the empirically plausible case, there is a downward pressure on real interest rates in recessions due to a precautionary savings motive. We show that in this setting (a) the economy may get stuck in a high-unemployment steady state, (b) the Taylor principle is insufficient to eliminate the local indeterminacy of the intended steady state, and (c) nominal rigidities and inincomplete markets are complementary in terms of amplifying the impact of shocks on the macroeconomy.

Description: In this paper, we solve the revenue maximization problem of a multi-product monopolist when the products are substitutes. We consider a Hotelling model with two horizontally differentiated goods located at the endpoints of the segment. Consumers are located uniformly on the segment; their valuations for each good are equal to the base consumption value minus distance costs. When the base consumption value is high, the seller maximizes her expected profit by offering a menu of base and opaque goods. In particular, a single half-half lottery over base goods is optimal under concave and linear costs. When base consumption value is low, only base goods are sold. Finally, when base consumption value is intermediate, the optimal mechanism may entail the offering of lotteries with the positive probability of no delivery. Our findings can explain the emergence of opaque goods sales (e.g., hotel bookings without a complete description of the hotel through hotwire.com or priceline.com) as the outcome of the industry’s search for the optimal selling scheme.

Description: Prescribed fire is commonly used in southeastern US forests and is being more widely applied in fire-prone ecosystems elsewhere. Research on direct effects of burning has focused on aboveground impacts to plants with less attention to belowground effects. We measured soil heating during experimental burns in longleaf pine sandhill and flatwoods ecosystems in the southeastern US. Soil heating was minimal in frequently burned sites. Where fire had been excluded for several decades, however, we detected substantial soil heating sustained for considerable durations. Long-duration heating was most prominent where accumulated forest floor duff (Oe and Oa organic horizons) was deepest, particularly at the base of mature pines in long-unburned sites. Temperatures potentially lethal to plant tissues (≥60°C) were sustained for several hours as deep as 10 cm near pines in flatwoods sites. Sustained temperatures ≥300°C, when impacts to soil nutrients can occur, were observed for up to 35 min at mineral soil surfaces. Patterns of heating were similar in long-unburned sandhill sites; however, temperatures were generally lower and durations more brief. Heat transfer resulting from smoldering in forest floor duff deserves further attention to predict mineral soil heating, forecast fire effects, and inform restoration efforts in fire-prone ecosystems.

Description: Allowing for ambiguity about the behavior of the policymaker in a simple New-Keynesian model gives rise to wedges between long-run inflation expectations, trend inflation, and the inflation target. The degree of ambiguity we measure in Blue Chip survey data helps explain the dynamics of long-run inflation expectations and the inflation trend measured in the US data. Ambiguity also has implications for monetary policy. We show that it is optimal for policymakers to lean against the households’ pessimistic expectations, but also document the limits to the extent the adverse effects of ambiguity can be undone.

Description: We develop a general framework to study source-dependent preferences in economic contexts. We behaviorally identify two key features. First, we drop the assumption of uniform uncertainty attitudes and allow for source-dependent attitudes. Second, we introduce subjective prices to compare outcomes across different sources. Our model evaluates profiles source-wise, by computing the source-dependent certainty equivalents; the latter are converted into the unit of account of a common source and then aggregated into a unique evaluation. By viewing time and location as instances of sources, we show that subjective discount factors and subjective exchange rates are emblematic examples of subjective prices. Finally, we use the model to explore the implications on optimal portfolio allocations and home bias.

Description: An understanding of the relationship between volume increment and stand density (basal area, stand density index, etc.) is of utmost importance for properly managing stand density to achieve specific management objectives. There are two main approaches to analyse growth–density relationships. The first relates volume increment to stand density through a basic relationship, which can vary with site productivity, age, and potentially incorporates treatment effects. The second is to relate the volume increment and density of thinned experimental plots relative to that of an unthinned experimental plot on the same site. Using a dataset of 229 thinned and unthinned experimental plots of Norway spruce, a growth model is developed describing the relationship between gross or net volume increment and basal area. The models indicate that gross volume increases with increasing basal area up to 50 m2 and thereafter becomes constant out to the maximum basal area. Alternatively, net volume increment was maximized at a basal area of 43 m2 and decreased with further increases in basal area. However, the models indicated a wide range where net volume increment was essentially constant, varying by less than 1 m3 ha−1 year−1. An analysis of different thinning scenarios indicated that the relative relationship between volume increment and stand density was dynamic and changed over the course of a rotation.

Description: Models estimating tree volume from stump diameter are important forest-management tools when volume estimation is needed postharvest, and dbh values are unavailable, for example the incidence of timber trespass. However, the use of stump diameter as the only independent variable for predicting tree volume has been limited. Therefore, in this article, stump diameter was used to estimate stem volume of Tectona grandis Linn. f, and this was compared with volume estimated from diameter at breast height. Five functions were considered each for the two stem diameters: simple linear, semilogarithmic, zero-intercept, power, and growth. Model assessment was based on least values of the root mean square error and Akaike information criterion. The results showed that the growth model had the best overall performance for both sets of volume models. A paired-sample t-test was used to compare volume estimated by stump diameter and volume estimated by diameter at breast height at 5 percent significance level. The results showed that there were no significant differences (P = .087) between timber volumes estimated from both stem diameters. Therefore, both diameters can be used interchangeably for modeling tree volume.

Description: This paper studies how material incentives and social norms shape ethnic identity choices in China. Provincial policies give material benefits to minorities, which consequently affect the ethnicity choices for children in ethnically mixed marriages. We formalize the ethnic identity choice in a simple framework, which highlights the interaction of (i) material benefits stemming from ethnic policies, (ii) identity costs associated with breaking the norm of following the father’s ethnicity, and (iii) social reputations altering the importance of identity costs. Consistent with the model, we find that ethnic policies increase the propensity to break the prevailing norm for mixed families with minority mothers. Moreover, the impact of ethnic policies is larger in localities where more such families follow the norm. More broadly, our study shows (1) how government policies can shape identity choices and (2) how one can allow for both complementarity and substitutability between individual and social motives in empirical analyses.

Description: Substantial growth losses in Douglas-fir can be the result of Swiss needle cast, a foliar disease caused by the fungus Nothophaeocryptopus gaeumannii. Although the disease is native to western North America, it is expected to become increasingly problematic in regions where climates become warmer in winter and wetter in spring, such as in coastal British Columbia (BC), Canada. Previous research suggests that tolerance to this disease is under partial genetic control. We therefore aim to screen for tolerance and resistance to the disease in the tree breeding population of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) in BC. We evaluated if early screening for resistance or tolerance to this disease is possible. We worked with 32 families grown for 18-years on two full-sibling genetic field trial sites representing different climates. We assessed 〉900 trees for disease signs and symptoms from 2017 to 2019. Needle retention was assessed in the field. In the laboratory, the proportion of stomata occluded with pseudothecia was measured, deoxyribonucleic acid (DNA) was extracted, and the proportion of fungal DNA in the needles was assessed using quantitative polymerase chain reaction. Strong differences were observed among families for needle retention, stomatal occlusion and fungal load. The milder and wetter site closer to the coast was generally more severely affected. Families showed rank changes between the two sites for all response variables. Higher needle retention was correlated with increased tree volume. No correlation was found between the proportion of stomata occluded with pseudothecia, fungal DNA load and needle retention. These results indicate that a more complex pathology is involved in causing needle loss. We conclude that screening for Swiss needle cast tolerance in the coastal BC Douglas-fir breeding population is possible if needle retention can be assessed and that area-specific deployment strategies may be needed given family rank changes in different environments.

Description: Treatment of individual trees in hardwood stands typically is conducted with herbicides that have no soil activity, such as triclopyr. However, triclopyr is not effective on some tree species. Applying a mixture of triclopyr and imazapyr would broaden the spectrum of species controlled, but nontarget mortality may be problematic as imazapyr may affect other trees through soil activity. We applied herbicide via girdle-and-spray as part of a forest stand improvement treatment in four upland hardwood stands in the Upper Coastal Plain of Alabama. We compared effects of using triclopyr alone with a mixture of triclopyr and imazapyr 18 months posttreatment. Only one untreated sweetgum (Liquidambar styraciflua) out of 440 trees was killed in the stands treated with the herbicide mixture (0.5 percent nontarget mortality rate). Nontarget mortality did not differ between treatments. However, the herbicide mixture controlled hickory (Carya spp.) and sourwood (Oxydendrum arboreum) better than triclopyr alone, with 56 percent of hickory treated with triclopyr still alive 18 months later, compared with 0 percent of hickory treated with the mixture. Our results indicate a mixture of triclopyr and imazapyr provides better control than triclopyr alone, and there is minimal risk to nontarget tree species in hardwood stands when used according to label recommendations. Study Implications Forest stand improvement (FSI) is a noncommercial practice typically conducted by cutting and using herbicide to kill undesirable trees. Consideration must be given to herbicide selection, which is based on efficacy on target species while minimizing nontarget mortality of residual trees. We found that a mixture of triclopyr and imazapyr applied via girdle-and-spray was more effective for FSI than triclopyr alone, which failed to control a significant proportion of treated hickory, and resulted in essentially no nontarget mortality in mixed hardwood stands 18 months after application.

Description: Computer models used to predict forest and fuels dynamics and wildfire behavior inform decisionmaking in contexts such as postdisturbance management. It is imperative to understand possible uncertainty in model predictions. We evaluated sensitivity of the Fire and Fuels Extension to the Forest Vegetation Simulator predictions to parameters that determine dynamics of standing dead trees (snags) and surface woody fuels. Predicted peak coarse and fine woody fuels were not sensitive to the decomposition rate of snags but were sensitive to decomposition rate of surface fuels regardless of initial snag density. Predictions of coarse woody fuel were sensitive to the snag fall rate when there was a higher initial density of snags. Fire behavior predictions were most sensitive to whether stylized fuel models or modeled fuels were used in calculations. When modeled fuels were used, fire behavior predictions were sensitive to the decomposition rate of surface fuels. Although this analysis does not inform the accuracy of model predictions, it does show where there is potential uncertainty in predictions of woody fuels succession and associated fire behavior. It is likely that any model that predicts postdisturbance fuel succession will also be sensitive to parameters that control snag dynamics and fuel decomposition. Study Implications Forest managers use computer models to help decide which actions to take to meet management objectives. Computer models have many settings and rules that affect predicted outcomes, and the values these settings should take are often uncertain. This study evaluates the consequences of such uncertainty on model predictions of future fuels following a high-severity fire. We show that model predictions are sensitive to the decomposition rate of small fuels and the snag fall rate. These results provide guidance for managers for which settings they should focus on when using these models and point to potential model improvements.

Description: Impact evaluations can help to inform policy decisions, but they are rooted in particular contexts and to what extent they generalize is an open question. I exploit a new data set of impact evaluation results and find a large amount of effect heterogeneity. Effect sizes vary systematically with study characteristics, with government-implemented programs having smaller effect sizes than academic or non-governmental organization-implemented programs, even controlling for sample size. I show that treatment effect heterogeneity can be appreciably reduced by taking study characteristics into account.

Description: This paper studies how voters’ selective ignorance interacts with policy design by political candidates. It shows that the selectivity empowers voters with extreme preferences and small groups, that divisive issues attract most attention, and that public goods are underfunded. Finer granularity of information increases these inefficiencies. Rational inattention can also explain why competing opportunistic candidates do not always converge on the same policy issues.

Description: Special tariffs have been increasingly adopted to protect domestic industries from potential injury caused by unfair international trade. In this study, a multinomial logit model is employed to examine the patterns and determinants of antidumping duty investigations in the global forest products industry. From 1995 to 2015, a total of 372 relevant cases are identified. The number of firms and the inclusion of unions as a petitioner generally improve the probability of an affirmative decision. The characteristics of petition countries have shown more impacts on the decisions than those of target countries. Developing countries have initiated a larger number of antidumping duty investigations in the global forest products industry, and furthermore, they are more inclined to adopt antidumping duties than developed countries. Countries with abundant forest resources and more forest products trade are more likely to make an affirmative decision. These findings will provide helpful information to industrial firms and government agencies in dealing with the challenges of global competition. Study Implications The findings reveal that getting more stakeholders involved in an antidumping duty investigation will increase the probability of trade intervention. The economic status in petition countries is the primary determinant of the decisions from antidumping duty investigations in the global forest products industry. Developing countries not only have initiated a large number of antidumping duty investigations in the forest products industry but also have been more inclined to adopt antidumping duties. Antidumping duty investigations offer an opportunity to countries with abundant forest resources and extensive forest products trade in case of unfair international competition.

Description: Higher temperatures and drought are key aspects of global change with the potential to alter the distribution and severity of many arthropod pests in forest systems. Scale insects (Hemiptera: Coccoidea) infest many tree species and are among the most important pests of trees in urban and rural forests, plantations and other forest systems. Infestations of native or exotic scale insects can kill or sicken trees with economic and ecosystem-wide consequences. Warming can have direct effects on the life history, fitness and population dynamics of many scale insect species by increasing development rate, survival or fecundity. These direct benefits can increase the geographic distribution of scale insects and their consequences for tree health. Warming and drought can affect scale insects indirectly by altering the quality of their host trees. Additive or interactive effects of warming and drought can change tree quality in such a way that it increases scale insect fitness and population growth. However, the effects are species- and context-dependent with some scale insect species negatively affected by drought-induced changes in tree quality. Warming and drought are often coincident in urban forests and predicted to co-occur in many parts of the world under climate change scenarios. The individual and interactive effects of these factors require further research to inform predictions and management of scale insect pests. Warming also indirectly affects scale insects by altering interactions with natural enemies. This includes changes in natural enemy phenology, community composition and abundance. In addition, warming can alter scale insect phenology or voltinism causing asynchrony with natural enemies or population growth too rapid for natural enemies to suppress. Direct and indirect effects of warming and drought on scale insects can increase the potential for some exotic species to become established and for some native species to become invasive. Unfortunately, much research on scale insects is confined to a few particularly important native or exotic pests which limits our ability to predict the effects of warming on many current or potential pests. More research is required to understand how warming and drought affect scale insects, scale insect management and the forest systems they inhabit.

Description: We reexamine the role of incomplete contracts in a dynamic model of renegotiation that endogenizes the timing of investments and trade. The interaction between bargaining and investment significantly alters the lessons learned from static models. When the opportunity to trade is expected to be long lasting, contracts that exacerbate the parties’ absolute vulnerability to hold-up—especially following under-investment—are desirable. For example, joint ownership of complementary assets can be optimal, an exclusivity agreement can protect the investments of its recipient, and trade contracts can facilitate purely cooperative investment.

Description: When choices are inconsistent due to behavioral biases, there is a theoretical debate about whether the structure of a model is necessary for providing precise welfare guidance based on those choices. To address this question empirically, we use standard data sets from the lab and field to evaluate the predictive power of two “model-free” approaches to behavioral welfare analysis. We find they typically have high predictive power, which means there is little ambiguity about what should be selected from each choice set. We also identify properties of revealed preferences that help to explain the predictive power of these approaches.

Description: Smartphones with their capability to receive Global Navigation Satellite Systems (GNSS) signals can be currently considered the most common devices used for positioning tasks, including forestry applications. This study focuses on possible improvements related to two crucial changes implemented into Android smartphone positioning in the last 3 years – dual-frequency (L1/L5) GNSS receivers and the possibility of recording raw GNSS data. The study comprises three experiments: (1) real-time measurements of individual points, (2) real-time recording of trajectories, and (3) post-processing of raw GNSS data provided by the smartphone receiver. The real-time tests were conducted using final positions provided by the internal receiver, i.e. without further processing or averaging. The test on individual points has proven that the Xiaomi Mi8 smartphone with a multi-constellation, dual-frequency receiver was the only device whose accuracy was not significantly different from single-frequency mapping-grade receiver under any conditions. The horizontal accuracy of most devices was lower during leaf-on season (root mean square errors between 5.41 and 12.55 m) than during leaf-off season (4.10–11.44 m), and the accuracy was significantly better under open-area conditions (1.72–4.51 m) for all tested devices when compared with forest conditions. Results of the second experiment with track recording suggest that smartphone receivers are better suited for dynamic applications – the mean shift between reference and measured trajectories varied from 1.23 to 5.98 m under leaf-on conditions. Post-processing of the raw GNSS data in the third experiment brought very variable results. We achieved centimetre-level accuracy under open-area conditions; however, in forest, the accuracies varied from meters to tens of meters. Observed loss of the signal strength in the forest represented ~20 per cent of the open-area value. Overall, the multi-constellation, dual-frequency receiver provided more robust and accurate positional solutions compared with single-frequency smartphones. Applicability of the raw GNSS data must be further studied especially in forests, as the provided data are highly susceptible to multipath and other GNSS adverse effects.

Description: This paper incorporates quasi-hyperbolic discounting into a Mirrlees taxation model to study the design of retirement policies for present-biased agents. I show that the government can improve the screening of productivity by exploiting time inconsistency. This is done by providing commitment to sophisticated agents and taking advantage of the incorrect beliefs of naïve agents. This can be achieved even if the degrees of present bias and sophistication are private information. I also demonstrate how the government can implement the optimal mechanism using retirement savings accounts and social security benefits.

Description: Recent research has pointed to large gaps in labor productivity between the agricultural and non-agricultural sectors in low-income countries, as well as between workers in rural and urban areas. Most estimates are based on national accounts or repeated cross-sections of micro-survey data, and as a result typically struggle to account for individual selection between sectors. This paper uses long-run individual-level panel data from two low-income countries (Indonesia and Kenya) to explore these gaps. Accounting for individual fixed effects leads to much smaller estimated productivity gains from moving into the non-agricultural sector (or urban areas), reducing estimated gaps by roughly 67 to 92%. Furthermore, gaps do not emerge up to five years after a move between sectors. We evaluate whether these findings imply a re-assessment of the conventional wisdom regarding sectoral gaps, discuss how to reconcile them with existing cross-sectional estimates, and consider implications for the desirability of sectoral reallocation of labor.

Description: The textbook New Keynesian (NK) model implies that the labor share is procyclical conditional on a monetary policy shock. We present evidence that a monetary policy tightening robustly increased the labor share and decreased real wages during the Great Moderation period in the United States, the Euro Area, the United Kingdom, Australia, and Canada. We show that this is inconsistent not only with the basic NK model, but also with medium-scale NK models commonly used for monetary policy analysis and where it is possible to break the direct link between the labor share and the inverse markup. Our results imply that either NK models are unable to separate the dynamics of the labor share from the markup or markups do not respond in the way NK models predict.

Description: This paper studies the contribution of parental influence in accounting for cross-country gaps in human capital achievements. We argue that the cross-country variation in unobserved parental characteristics is at least as important as the one in commonly used observable proxies of parental socioeconomic background. We infer this through an indirect empirical approach, based on the comparison of the school performance of second-generation immigrants. We document that, within the same host country or even the same school, students whose parents come from high-scoring countries in standardized international tests do better than their peers with similar socioeconomic backgrounds. This finding is not driven by differential selection into emigration. We provide several pieces of evidence that support the transmission of cultural values as a leading channel behind the cross-country variation in the parental component. Unobserved parental characteristics account for about 15% of the cross-country variance in test scores, roughly doubling the overall contribution of parental influence.

Description: National forest inventories, in which trees are often mapped within the plots, provide a tool for the quantification of large-scale forest structure since they cover all forest areas. Many National Forest Inventories follow a nested design in order to reduce the sampling effort for smaller trees. We propose and test a methodology that allows the spatial pattern of trees, species mingling and size differentiation to be characterized using the nearest neighbour indices and second-order moment functions from nested plot data. The nearest neighbour indices and second-order moment functions for the actual distribution are compared with simulations of the appropriate null model: spatial randomness for spatial pattern characterization or spatial independence for species mingling and size differentiation. The proposed method consists of constraining the null model to fit the nested plot design. For the purposes of the study, we simulated 120 plots and used 26 real plots located in pure and mixed stands in Central Spain, for which a complete census with detailed information about trees was available. The nested design used in the Spanish National Forest Inventory (SNFI) plots was simulated to test the performance, taking the complete census as reference. Despite of the limited accuracy for some structural measures, the proposed method based on nested design data performed better for most of the nearest neighbour indices and second-order moment functions than the strategy currently used in the SNFI for structure assessment in a subsample of SNFI plots, consisting of mapping the 20 trees closest to the plot centre. Nearest neighbour indices provided greater accuracy for species mingling assessment than second-order moment functions, whereas the opposite occurred when describing spatial pattern and size differentiation. The methodology proposed provides the first insight into the characterization of forest structure in nested designs although more evaluations are required for different forest types.

Description: There is a large body of evidence showing that for many countries the structure of wages and pensions and the labor law legislation are different for public and private employees. Such differences affect the occupational choice of agents and might generate some type of misallocation. We develop a life-cycle model with endogenous occupational choice and heterogeneous agents to study the implications of an overpaid public sector. The model is estimated to be consistent with micro and macro evidence for Brazil, a country with a high public sector earnings premium. Our counterfactual exercises demonstrate that public–private earnings premium can generate important allocation effects and sizeable productivity losses. For instance, a reform that would decrease the public–private wage premium from its benchmark value of $19\%$ to $15\%$ and would align the pension of public sector workers with the one in place for private sector workers could increase aggregate output by nearly $11.2\%$ in the long run without any decrease in the supply of public infrastructure. We provide a decomposition of the aggregate effect into changes in factors accumulation and changes in TFP and implement a welfare distributive analysis.

Description: We provide the first analysis of the risk-sharing implications of altruism networks. Agents are embedded in a fixed network and care about each other. We explore whether altruistic transfers help smooth consumption and how this depends on the shape of the network. We find that altruism networks have a first-order impact on risk. Altruistic transfers generate efficient insurance when the network of perfect altruistic ties is strongly connected. We uncover two specific empirical implications of altruism networks. First, bridges can generate good overall risk sharing, and, more generally, the quality of informal insurance depends on the average path length of the network. Second, large shocks are well-insured by connected altruism networks. By contrast, large shocks tend to be badly insured in models of informal insurance with frictions. We characterize what happens for shocks that leave the structure of giving relationships unchanged. We further explore the relationship between consumption variance and centrality, correlation in consumption streams across agents, and the impact of adding links.

Description: Accurate and frequently updated tree volume estimates are required for poplar plantations, which are characterized by fast growth rate and short rotation. In this study, we tested the potential of terrestrial laser scanning (TLS) as a reliable method for developing nondestructive tree volume allometries in poplar plantations. The trial was conducted in Italy, where 4- to 10-year-old hybrid plantations were sampled to develop tree crown volume allometry in leaf-on conditions, tree stem volume, and height-diameter allometries in leaf-off conditions. We tested one-entry models based on diameter and two-entry models based on both diameter and height. Model performance was assessed by residual analysis. Results indicate that TLS can provide accurate models of tree stem and crown volume, with percentage of root-mean-square error of about 20 percent and 15 percent, respectively. The inclusion of height does not bring relevant improvement in the models, so that only diameter can be used to predict tree stem and crown volume. The TLS-measured stem volume estimates agreed with an available formula derived from harvesting. We concluded that TLS is a reliable method for developing nondestructive volume allometries in poplar plantations and holds great potential to enhance conventional tree inventory and monitoring. Study Implications: Terrestrial laser scanning (TLS) is a technique that allows nondestructive measurement of the three-dimensional structure of a tree with high precision and low cost. The ability of TLS to measure both tree crown volume and tree position can be effective to test optimal spacing requirements and also to test innovative schemes such as mixed or polycyclic poplar plantations. The spatially explicit nature of TLS measurements allows better integration with different remotely sensed sensors, which can be used in combination with TLS, enabling a multiscale assessment of poplar plantation structure with different levels of detail, enhancing conventional tree inventory and supporting effective management strategies.

Description: Oak-dominated forests, economically and ecologically valuable ecosystems, are widely distributed in China. These oak-dominated forests are now generally degraded coppice forests, and are of relatively low quality. Climate change has been shown to affect forest growth, tree mortality, and recruitment, but available forest growth models are lacking to study climate effects. In this study, a climate-sensitive, transition-matrix growth model (CM) was developed for uneven-aged, mixed-species oak forests using data collected from 253 sample plots from the 8th (2010) and 9th (2015) Chinese National Forest Inventory in Shanxi Province, China. To investigate robustness of the model, we also produced a variable transition model that did not consider climate change (NCM), and fixed parameter transition matrix model (FM), using the same data. Short-term and long-term predictive performance of CM, NCM, and FM were compared. Results indicated that for short-term prediction (5 years), there was almost no significant difference among the three predictive models, though CM exhibited slightly better performance. In contrast, for long-term prediction (100 years), CM, under the three representative concentration pathways (RCPs), i.e. RCP2.6, RCP4.5 and RCP8.5, indicated rather different dynamics that were more reliable because climate factors were considered which could significantly influence forest dynamics, especially in long-term prediction intervals. The CM model provides a framework for the management of mixed-species oak forests in the context of climate change.

Description: Timberland ownership has drastically changed in the United States since the 1980s, driven by the divestitures of vertically integrated forest products companies. Having sold their timberland, forest products companies have exposed themselves more to the risk of raw material supply. To hedge against this risk, forest products companies usually use long-term timber contracts (LTTC). The objective of this article is to update the valuation framework for LTTCs proposed by Shaffer (1984) by including alternative option price models and refining the estimates of some key economic variables. In particular, conditional volatility from the generalized autoregressive conditional heteroscedasticity model and quasi-conditional volatility from rolling estimation windows, in addition to simple standard deviation, are used for the volatility estimates in the option pricing models. Contrary to the previous result by Shaffer (1984), our analysis suggests that LTTCs that were once profitable for forest products companies in the 1980s are no longer so under current market conditions. This is primarily because both timber price volatility and the risk-free interest rates have declined significantly. Thus, to be better off, forest products companies need to either lower the administration and management costs of those LTTCs or rely more on the open market for timber procurement. Study Implications: Forest products companies have traditionally relied on long-term timber contracts (LTTC) negotiated with forest landowners to mitigate the risk of raw material supply. The value of these LTTCs highly depends on the economic context. This research provides some insights into the valuation of LTTCs in the southeastern United States. Forest products companies can use this updated framework to aid their decisionmaking in timber procurement.

Description: Deciduous seasonal forests (DSFs) have a peculiar floristic composition, with species capable of surviving periods of high water deficit in a year. Our goal was to demonstrate that abiotic filters lead to the assembly of two DSF communities that have high floristic dissimilarity. For this, we characterized the environment of the areas and used the community-weighted mean (CWM), functional richness (FRic) and functional dispersion (FDis) indices for regional recognition of functional patterns. The local assessment of assembly rules was carried out using null models. We found differences in the FRic and FDis between the areas, which was attributed to the different floristic influences exercised on the communities. However, in both, the typical attributes of dry formations were dominant (CWM), indicating that, on the regional scale of study, the dry season acts as a filter in the composition of species in the communities. On a local scale, stochastic dispersion was identified as the most influential mechanism in the assembly of communities. We conclude that deterministic and stochastic processes act in the assembly of the studied communities, and the proportion of each of these depends on the scale, with abiotic filtration predominating on a regional scale and stochastic dispersion events on a local scale. Study Implications With the expansion of agriculture and climate change, tropical dry biomes, such as deciduous seasonal forests, are rapidly changing. In this study, we contribute to the recognition of functional standards and community assembly of this vegetation type to assist in management planning, restoration, and conservation. Understanding the different processes involved in building a community is crucial for anticipating how communities will behave under future environmental scenarios.

Description: Quantification of soil organic carbon (SOC) stocks in different land uses holds vital significance because of its implications regarding carbon sequestration as the largest terrestrial carbon pool. The current study was conducted to quantify and compare SOC stocks in forest land, agricultural land, and barren land-use categories in the subtropical ecosystems of the Himalayan foothills in Kashmir. Results showed the highest SOC value in the forest soil (75 ± 11.1 Mg C ha−1) followed by agricultural soil (58 ± 7.0 Mg C ha−1) and barren land (44 ± 6.5 Mg C ha−1). SOC stocks in different land uses showed broad variations with values as high as 106 ± 11.3 Mg C ha−1 (forest soils) and as low as 14.1 ± 7.1 Mg C ha−1 (barren land). The forest SOC values responded significantly to species composition with the highest values in Pinus roxburghii Sarg. pure stands as compared with broad leaved forests. Multivariate ordination analyses revealed that the variations in SOC stocks were significantly correlated with vegetation type, altitude, and soil bulk density. The study has identified anthropogenic disturbances as a major factor deteriorating local SOC stocks and recommends immediate soil restoration efforts to enhance the ecological significance of soils as vital regional carbon sinks. Study Implications The current study was designed to investigate the soil organic carbon (SOC) levels in different land uses of the Kashmir Himalayas, Pakistan. Results revealed forest soils as the major carbon sinks of the region, attributed to diverse species composition having a significant quantity of organic residues, followed by agricultural soils. Barren land-use class exhibited the lowest SOC values due to minimum vegetation cover, erosion, and degradation. Significant correlations of SOC stocks with geographical and edaphic variables were identified by multivariate ordination analysis in the investigated land-use classes. Results validate the significance of forests in enhancing SOC stocks, demanding forest restoration in the area by controlling the forest losses as well as afforestation. This article provides vital information required for better understanding of SOC stocks in different land-use classes in the subtropical ecosystems of the Kashmir region.

Description: This paper proposes a theory of pricing premised upon the assumptions that customers dislike unfair prices—those marked up steeply over cost—and that firms take these concerns into account when setting prices. Because they do not observe firms’ costs, customers must extract costs from prices. The theory assumes that customers infer less than rationally: When a price rises due to a cost increase, customers partially misattribute the higher price to a higher markup—which they find unfair. Firms anticipate this response and trim their price increases, which drives the passthrough of costs into prices below one: Prices are somewhat rigid. Embedded in a New Keynesian model as a replacement for the usual pricing frictions, our theory produces monetary nonneutrality: When monetary policy loosens and inflation rises, customers misperceive markups as higher and feel unfairly treated; firms mitigate this perceived unfairness by reducing their markups; in general equilibrium, employment rises. The theory also features a hybrid short-run Phillips curve, realistic impulse responses of output and employment to monetary and technology shocks, and an upward-sloping long-run Phillips curve.

Description: Non-governmental organizations (NGOs) have been at the forefront of securing environmental justice for the people of Nigeria’s Niger Delta suffering the effects of pollution arising from petroleum exploitation. Standing constraints have, however, limited NGOs’ abilities to access the courts to prevent or remedy pollution. This article analyses the recent decision of Nigeria’s Supreme Court in Center for Oil Pollution Watch v Nigerian National Petroleum Corporation (NNPC). It finds that environmental NGOs, previously unable to institute action under existing public interest litigation procedures, can now institute action in their own rights to prevent or remedy environmental pollution in Nigeria.

Description: We develop a model of monopolistic competition with a differentiated intermediate good and variable elasticity of technological substitution. The model allows to study the nature and origins of external increasing returns. We single out two sources of scale economies: specialization and competition. The former depends only on how total factor productivity (TFP) varies with input diversity, while the latter is fully captured by the behavior of the elasticity of substitution across inputs. This distinction gives rise to a full characterization of the rich array of competition regimes in our model. The necessary and sufficient conditions for each regime to occur are expressed in terms of the relationships between TFP and the elasticity of substitution as functions of the input diversity. Moreover, we demonstrate that, despite the folk wisdom resting on constant elasticity of substitution models, specialization economies are in general neither necessary nor sufficient for external increasing returns to emerge. This highlights the profound and nontrivial role of market competition in generating agglomeration economies and other phenomena driven by scale economies.

Description: This study examines the effects of China’s industrial clusters on regional economic growth and urban–rural income inequality within a region. A density-based index (DBI) is developed to capture the unique features of cluster development in China. From a county-level DBI panel data constructed based on firm- and county-level datasets, we find that clusters enhance local economic growth substantially. Moreover, the existence of entrepreneurial clusters (clusters mainly consist of nonstate-owned firms) helps to reduce local urban–rural income inequality by increasing the income of local rural residents. We also find that the clustering effects on growth and reduction of inequality are less significant in more urbanized regions or megacities. Identification issues are carefully addressed by deploying two-stage estimations with instrumental variables and Granger test.

Description: This article considers the heterogeneous microfoundations of agglomeration economies. It studies the co-location of industries to look for evidence of labour pooling, input sharing and knowledge spillovers. The novel contribution of the article is that it estimates single-industry models using a common empirical framework that exploits the cross-sectional variation in how one industry co-locates with the other industries in the economy. This unified approach yields evidence on the relative importance of the Marshallian microfoundations at the single-industry level, allowing for like-for-like cross-industry comparisons on the determinants of agglomeration. Using UK data, we estimate such microfoundation models for 97 manufacturing sectors, including the classic agglomeration cases of automobiles, computers, cutlery and textiles. These four cases—as with all of the individual industry models we estimate—clearly show the importance of the Marshallian forces. However, they also highlight how the importance of these forces varies across industries—implying that extrapolation from cases should be viewed with caution. The article concludes with an investigation of the pattern of heterogeneity. The degree of an industry’s clustering (localisation), entrepreneurship, incumbent firm size and worker education are shown to contribute to the pattern of heterogeneous microfoundations.

Description: Recently, economic geographers have sought to account for how regional and national initiatives shape the strategic decisions of actors in global production networks (GPNs). In this article, I intend to discuss the political and institutional dynamics by which GPNs evolve, and the capacity of states to shape emerging organizational and spatial arrangements in dynamic GPNs. Building on assemblage thinking, I conceptualize these political and institutional dynamics as the unbundling of legal, regulatory and institutional components of nation-state authorities that govern GPNs, and the subsequent reassembling of these components through emerging interactions with finance, technology and new forms of private authority. These emerging global assemblages are both partially embedded in global cities and stretch across and within the borders of nation-states. Building on this conceptual framework, this article explains how the exclusive nation-state authorities that traditionally governed liquefied natural gas (LNG) trade and markets are becoming unbundled. The article focuses on the initiatives of public and private actors in Singapore who are attempting to shape evolutionary dynamics in GPNs by establishing a hub for LNG trading and speculative financing in Asia. The article finds that Singapore’s capacity to shape LNG production networks is dependent upon the capacity of public and private actors in Singapore to establish cross-border connectivity to markets in Southeast Asia.

Description: This article investigates the link between multinational enterprises (MNEs) and employment in their host regions by cross-fertilising the literature on MNE externalities with the emerging body of research on industrial relatedness. The link between employment and MNE presence in the same and related industries is tested for European regions. The results suggest that cross-sectoral MNE spillovers are mediated through industrial relatedness and that they are positively and significantly associated with higher employment levels, independently of input–output relations. Our results indicate that regions characterised by lower factor prices are likely to benefit the most from the presence of multinationals in terms of employment, but these benefits are concentrated in high knowledge-intensive sectors, potentially fostering inequalities within less-developed economies.