ALBERT

Description: In January 2016, a Priorities and Solutions Project was initiated to identify the most pressing issues facing society with input from a broad spectrum of the agricultural and applied economics profession. This consensus-building endeavor was facilitated by the Council on Food, Agriculture and Resource Economics (C-FARE), working in partnership with the Agricultural and Applied Economics Association (AAEA). The Economic Research Service (ERS) of the USDA provided expertise and logistical support.1 1 The Priorities and Solutions Project is intended to provide the profession with the opportunity to shape its own future by identifying and communicating research opportunities to our profession, our stakeholders, policymakers, and the public. Agricultural and applied economists can work to provide solutions to some of society’s most difficult problems or challenges. This special issue is based on the findings of the project.

Description: Research priorities for the U.S. farm economy include increasing the productivity and cost efficiency on current land resources while understanding production agriculture across the globe. Providing unbiased objective analysis to policymakers with regard to commodity programs, insurance markets, agricultural credit, and the production of bioenergy are important issues that directly affect not only the U.S. farm economy but other agricultural regions. The ability to manage risk, the increasing complexity of farm operations, the ability of the U.S. farm sector to be nimble to changes in individual and societal preferences, and the efficient discovery of information through efficient markets offer a wealth of research opportunities.

Description: Climate change is not just a topic for the future—it is already producing real consequences. Economically, the issue has three principal dimensions: impacts, that is, how vulnerable are we; adaptation, that is, what can we do to reduce the impacts by altering operations; and mitigation, that is, what can we do to reduce the drivers causing climate change and thus the long-term extent of climate change? All of these issues have economic dimensions, including appraising damages and the value of effects reducing actions, as well as the formulation of efficient policies. Thus, it is not surprising that this is both an active agricultural economic research area and one with many more research possibilities. We review the impacts, adaptation, and mitigation literature, identifying issues, summarizing main findings, commenting on methods, and pointing out research needs, with a special focus on what agricultural/applied economists have to offer.

Description: We compare the food values in the USA and Norway using the best–worst scaling approach. The food values examined are aimed at capturing the main issues related to food consumption such as naturalness, taste, price, safety, convenience, nutrition, novelty, origin, fairness, appearance, environmental impact and animal welfare. Results show that respondents in both countries have mostly similar food values, with safety being the most important value; while convenience and novelty are the least important values. Specifically, US respondents consider price more important and naturalness less important than Norwegian respondents.

Description: Agritourism attractions are a commonly chosen alternative in farm diversification. Some attractions are based on active farms, while others are based on rural ambience. We model and estimate the agritourism attraction market as a differentiated-goods market based on Israeli market data and simulate different scenarios. We show that total welfare increases when attractions are based on rural ambience rather than on active farms. We also show that an indirect support scheme has a stronger impact on total welfare than a direct scheme.

Description: This paper presents the EU-wide individual farm-level model (IFM-CAP) applied to assess the economic effects of CAP greening. IFM-CAP is a static positive programming model developed to capture the full heterogeneity of EU farms in terms of policy representation and impacts. Simulation results show that, although the proportions of farms and utilised agricultural area (UAA) subject to CAP greening are sizeable (55 per cent of all farms and 86 per cent of UAA) at EU-27 level, the reallocated area caused by CAP greening represents only 4.5 per cent of UAA. Farm income and total production both decrease by 1 and 0.9 per cent, respectively. In total, around 29 per cent of the farm population is affected by CAP greening in the EU-27.

Description: 1910–12

Description: 1957

Description: The objective of this case study is to examine the farm management decision of whether to adopt a new, genetically engineered potato variety. We describe the potato supply chain from seed production to final consumer products and explore how price and production risk interact to influence decision making at each link in that chain. We provide extensive supplemental material as well, including a teaching note with assignment and/or discussion questions, an introduction to and application of stakeholder theory, and a tool that assists students in calculating expected and simulated actual returns from their choice of potato variety.

Description: Sixty years ago, T.W. Schultz introduced the idea of the productivity “residual” to agricultural economics (1956). Schultz’s main message was that growth in conventional inputs accounted for little of the observed growth in agricultural output, and that there was work to be done by agricultural economists to understand and ultimately eliminate this unexplained residual called “productivity.” Thus was launched the economics of agricultural productivity as a sub-field within agricultural economics, along with the economics of agricultural R&D and innovation and related government policy. Much progress has been made in the decades since. Still, critical issues remain unresolved. This matters because agricultural innovation and productivity matter, and so do the related policies that rest to some extent on our established understanding of the economic relationships. In this paper I review some unsettled issues related to economic models and measures applied to agricultural R&D and productivity, and some unfinished business in terms of economic and policy questions that are not yet well answered. Before doing that, I present some evidence on agricultural productivity and why it matters. Next, with a nod to “factology,” I present available productivity measures from the U.S. Department of Agriculture (USDA) and International Science and Technology Practice and Policy (InSTePP) Center, and compare them in the context of translog cost function models. In subsequent sections I use these and other data to develop new evidence related to two contentious questions: ( a ) Do farmers benefit from public agricultural R&D? ( b ) Has U.S. agricultural productivity growth slowed in recent decades? The answers are revealed within.

Description: We conduct meta-analyses of the estimated impacts of corn ethanol on food and fuel prices, as well as greenhouse gases, and analyze the implications for the balance of trade. The meta-analyses suggest that corn ethanol has minor effects on greenhouse gas emissions and significant yet moderate effects on food and fuel prices. However, corn ethanol has a relatively significant impact on fuel security in terms of reductions in the import of oil to the U.S. and its overall effect on the U.S. balance of trade.

Description: We provide a financial model to evaluate an orange grove investment in Florida, the producing region supplying around 90% of U.S. domestic production of orange juice. A representative orange grower planting early-mid varieties for the processed market is featured in the case. The study assumes that an existing grove has become disease-infested to a degree that there is little, if any economic value in maintaining it. The grower is left with the choice to replant the grove or to convert the land to other uses. The replanting baseline model yields a 9.7% Modified Internal Rate of Return (MIRR) and the Monte Carlo simulation shows that MIRR is equal or higher than the 7.5% hurdle rate around 81% times the model is simulated. The risk of managing an orange grove is higher than a decade ago mainly due to the presence of citrus greening, a disease that reduces yields and degrades fruit quality, causing variability in productivity and operating costs. Opportunities for growers include planting incentive programs implemented by both the government and major citrus processors and from policy changes such as the possibility of changes in depreciation of new investment for income tax purposes. Readers of this case study are expected to challenge the assumptions of the financial model and consider additional elements of risk and opportunities on their assessment of the potential orange grove investment.

Description: University Distinguished Professor, 2005–present; professor, 1997–2005; associate professor, 1992–1997; assistant professor, 1986–1992. Department of Agricultural, Food, and Resource Economics, Michigan State University.

Description: Professor, 1998–present; assistant/associate professor, 1988–1998. Department of Agricultural, Environmental & Development Economics, The Ohio State University.

Description: Gellert Family Professor, 2008–present; Associate Dean for Academic Affairs, 2016–present; professor, 1998–2008; associate professor, 1991–1998; assistant professor, 1985–1991. Charles H. Dyson School of Applied Economics and Management, Cornell University.

Description: The son of a foreign correspondent, Scott Swinton was born in Rome, Italy, and grew up in New York City. The family apartment was frequented by journalists from around the world. New York in the 1960s and 1970s was part intercultural melting pot and part cauldron of social ferment. Several summers in the Hudson Valley acquainted Swinton with farming and gardening. Urban summer jobs in high school at a plant store and running a community park cemented his fondness for growing things, as well as for the people who care for them.

Description: Rainbolt Chair of Agricultural Finance, 2014–present; Acting Department Head, 2012–2014; Sarkeys Distinguished Professor, 2010–2014; Regents Professor, 2004–present; professor, 1995–2004; associate professor, 1990–1995; assistant professor, 1986–1990; economics advisor, Polish/American Extension Project, 1992. Oklahoma State University.

Description: Thomas A. Hieronymus Distinguished Chair in Futures Markets, and Director of the Office of Futures and Options Research, 2003–present. University of Illinois at Urbana-Champaign (UIUC).

Description: In an era of rising skepticism about science, this article explores what agricultural and applied economists can do to advance knowledge. If knowledge is what is believed by the preponderance of a community, then the key to advancing knowledge is to build substantive arguments—ones that are persuasive. To evaluate the substantiveness of an argument, this article develops a framework based on validity, topic, and audience. Applying that framework to two highly-cited articles, this article concludes that validity is a necessary condition for a substantive argument, but relevance (of topic to audience) is the sufficient condition. Applied economists are well-positioned to build compelling, objective arguments by fitting appropriate theory and methods to relevant, important topics.

Description: The food consumer plays an increasingly prominent role in shaping the food and farming system. A better understanding of how public policies affect consumer choice and how those choices impact health, environment, and food security outcomes is needed. This paper addresses several key challenges we see for the future, including issues related to dietary-related diseases and the efficacy of policies designed to improve dietary choices, trust in the food system, acceptance of new food and farm technologies, environmental impacts of food consumption, preferences for increased food quality, and issues related to food safety. We also identify some research challenges and barriers that exist when studying these issues, including data quality and availability, uncertainty in the underlying biological and physical sciences, and the challenges to welfare economics that are presented by behavioral economics. We also identify the unique role that economists can play in helping address these key societal challenges.

Description: U.S. agriculture is vital to meeting a growing global population’s demand for food, fiber, feed, and fuel. Smart technologies, big data, and improvements in crop genetics present producers with promising new opportunities for meeting these needs. However, a changing climate and an expanding global population impose challenges to increasing crop and livestock production while sustaining the natural resource base and protecting environmental quality. Sustainable agricultural development will call for systems approaches to allocate land among competing uses, coupled with the adoption of conservation technologies incentivized by cost-effective policies that have been based on evidence from sound economic, behavioral, biological, and technological research. This paper suggests directions for future research in nine key dimensions that can fill important gaps in the existing literature and build on new research methods and policy needs, as well as inform strategies for sustainable growth of agriculture.

Description: Food insecurity is now recognized as a major health crisis in the United States. This is due to the size of the problem—more than 42 million persons were food insecure in 2015—as well as the multiple negative health outcomes and higher health care costs attributable to food insecurity. An extensive body of literature from multiple fields has examined the causes and consequences of food insecurity and the efficacy of food assistance programs—especially the Supplemental Nutrition Assistance Program. We review this literature and provide suggestions for future research directions. We suggest examining the distribution of food insecurity within households, the impact of the food distribution system on food insecurity, the coping mechanisms of low-income food secure families, food insecurity among American Indians, the effects of charitable food assistance, the causal relationship between food insecurity and health outcomes, the declining age gradient in food insecurity among Seniors, the effects of labor force participation and the Great Recession on food insecurity, and the long-term consequences of food insecurity. In addition, the impact of two recent policy recommendations on food insecurity – the minimum wage and the Affordable Care – Act should be considered.

Description: This article examines the challenge and opportunities of Big Data, and concludes that these technologies will lead to relevant analysis at every stage of the agricultural value chain. Big Data is defined by several characteristics beyond size, particularly, the volume, velocity, variety, and veracity of the data. We discuss a set of analytical techniques that are increasingly relevant to our profession as one addresses these issues. Ultimately, we resolve that agricultural and applied economists are uniquely positioned to contribute to the research and outreach agenda on Big Data. We believe there are relevant policy, farm management, supply chain, consumer demand, and sustainability issues where our profession can make major contributions. The authors are thankful to the anonymous reviewers and editor Craig Gundersen for helpful comments. Support was provided by the Mississippi Agricultural and Forestry Experiment Station Special Research Initiative.

Description: Cellular processes, such as signal transduction and cell wall deposition, are organized by macromolecule interactions. Experimentally determined protein–protein interactions (PPIs) and protein–DNA interactions (PDIs) relevant to woody plant development are sparse. To begin to develop a Populus trichocarpa Torr. & A. Gray wood interactome, we applied the yeast-two-hybrid (Y2H) assay in different ways to enable the discovery of novel PPIs and connected networks. We first cloned open reading frames (ORFs) for 361 genes markedly upregulated in secondary xylem compared with secondary phloem and performed a binary Y2H screen with these proteins. By screening a xylem cDNA library for interactors of a subset of these proteins and then recapitulating the process by using a subset of the interactors as baits, we ultimately identified 165 PPIs involving 162 different ORFs. Thirty-eight transcription factors (TFs) included in our collection of P. trichocarpa wood ORFs were used in a Y1H screen for binding to promoter regions of three genes involved in lignin biosynthesis resulting in 40 PDIs involving 20 different TFs. The network incorporating both the PPIs and PDIs included 14 connected subnetworks, with the largest having 132 members. Protein–protein interactions and PDIs validated previous reports and also identified new candidate wood formation proteins and modules through their interactions with proteins and promoters known to be involved in secondary cell wall synthesis. Selected examples are discussed including a PPI between Mps one binder (MOB1) and a mitogen-activated protein kinase kinase kinase kinase (M4K) that was further characterized by assays confirming the PPI as well as its effect on subcellular localization. Mapping of published transcriptomic data showing developmentally detailed expression patterns across a secondary stem onto the network supported that the PPIs and PDIs are relevant to wood formation, and also illustrated that wood-associated interactions involve gene products that are not upregulated in secondary xylem.

Description: The advances in ‘high-throughput’ biology have significantly expanded our fundamental understanding of complex biological processes inherent to tree growth and development. Relative to the significant achievements attained with whole genome re-sequencing and transcriptomics efforts, the development and power of post-transcriptional tools such as proteomics and metabolomics continue to lag behind in tree biology. However, the inclusion of these powerful functional genomics platforms should substantially enable systems biology assessments of tree development, physiology and response(s) to biotic and abiotic stresses. Herein, we employ a non-targeted metabolomics platform to elucidate the metabolic plasticity of xylem lignification in distinct hybrid poplar genetic backgrounds, as well as in transgenic trees in these backgrounds expressing two common constructs: the first construct (C4H::F5H) augments monolignol content (syringyl:guaiacyl (S:G) ratio), while the second construct (C3′H-RNAi) reduces cell wall lignification. The results clearly show that genotype-specific metabolism exists, and provide an appropriate foundation for properly comparing the influence of background on the relationships between metabolic and specific phenotypic traits. Moreover, it was apparent that transgene-induced phenotypic gradients in cell wall chemical wood can be associated with global metabolism of secondary xylem biosynthesis, however in a genotype-specific manner. This result implies that the same may be true for phenotypic gradients arising through natural genetic variation, intensive breeding or environmental factors. It is also apparent that while distinct, at a global level the wood-forming metabolisms of different poplar hybrids can, to some extent, respond similarly to the influences of genetic manipulation of lignin-related genes. This further implies that with the correct approach, it may be possible to associate the emergence of specific wood traits from different genetic backgrounds—be they transgene-induced or otherwise—with stable metabolic signatures.

Description: Although eucalypts are the most planted hardwood trees worldwide, the majority of them are frost sensitive. The recent creation of frost-tolerant hybrids such as Eucalyptus gundal plants ( E. gunnii × E. dalrympleana hybrids), now enables the development of industrial plantations in northern countries. Our objective was to evaluate the impact of cold on the wood structure and composition of these hybrids, and on the biosynthetic and regulatory processes controlling their secondary cell-wall (SCW) formation. We used an integrated approach combining histology, biochemical characterization and transcriptomic profiling as well as gene co-expression analyses to investigate xylem tissues from Eucalyptus hybrids exposed to cold conditions. Chilling temperatures triggered the deposition of thicker and more lignified xylem cell walls as well as regulation at the transcriptional level of SCW genes. Most genes involved in lignin biosynthesis, except those specifically dedicated to syringyl unit biosynthesis, were up-regulated. The construction of a co-expression network enabled the identification of both known and potential new SCW transcription factors, induced by cold stress. These regulators at the crossroads between cold signalling and SCW formation are promising candidates for functional studies since they may contribute to the tolerance of E. gunnii × E. dalrympleana hybrids to cold.

Description: Wood is a renewable resource that can be employed for the production of second generation biofuels by enzymatic saccharification and subsequent fermentation. Knowledge on how the saccharification potential is affected by genotype-related variation of wood traits and drought is scarce. Here, we used three Populus nigra L. genotypes from habitats differing in water availability to (i) investigate the relationships between wood anatomy, lignin content and saccharification and (ii) identify genes and co-expressed gene clusters related to genotype and drought-induced variation in wood traits and saccharification potential. The three poplar genotypes differed in wood anatomy, lignin content and saccharification potential. Drought resulted in reduced cambial activity, decreased vessel and fiber lumina, and increased the saccharification potential. The saccharification potential was unrelated to lignin content as well as to most wood anatomical traits. RNA sequencing of the developing xylem revealed that 1.5% of the analyzed genes were differentially expressed in response to drought, while 67% differed among the genotypes. Weighted gene correlation network analysis identified modules of co-expressed genes correlated with saccharification potential. These modules were enriched in gene ontology terms related to cell wall polysaccharide biosynthesis and modification and vesicle transport, but not to lignin biosynthesis. Among the most strongly saccharification-correlated genes, those with regulatory functions, especially kinases, were prominent. We further identified transcription factors whose transcript abundances differed among genotypes, and which were co-regulated with genes for biosynthesis and modifications of hemicelluloses and pectin. Overall, our study suggests that the regulation of pectin and hemicellulose metabolism is a promising target for improving wood quality of second generation bioenergy crops. The causal relationship of the identified genes and pathways with saccharification potential needs to be validated in further experiments.

Description: Vegetative propagation through somatic embryogenesis is critical in conifer biotechnology towards multivarietal forestry that uses elite varieties to cope with environmental and socio-economic issues. An important and still sub-optimal process during in vitro maturation of somatic embryos (SE) is the biosynthesis and deposition of storage proteins, which are rich in amino acids with high nitrogen (N) content, such as arginine. Mobilization of these N-rich proteins is essential for the germination and production of vigorous somatic seedlings. Somatic embryos accumulate lower levels of N reserves than zygotic embryos (ZE) at a similar stage of development. To understand the molecular basis for this difference, the arginine metabolic pathway has been characterized in maritime pine ( Pinus pinaster Ait.). The genes involved in arginine metabolism have been identified and GFP-fusion constructs were used to locate the enzymes in different cellular compartments and clarify their metabolic roles during embryogenesis and germination. Analysis of gene expression during somatic embryo maturation revealed high levels of transcripts for genes involved in the biosynthesis and metabolic utilization of arginine. By contrast, enhanced expression levels were only observed during the last stages of maturation and germination of ZE, consistent with the adequate accumulation and mobilization of protein reserves. These results suggest that arginine metabolism is unbalanced in SE (simultaneous biosynthesis and degradation of arginine) and could explain the lower accumulation of storage proteins observed during the late stages of somatic embryogenesis.

Description: Wall-to-wall forest management inventories with the area-based method using airborne laser scanner (ALS) data are operational in many countries. With this method, empirical relationships are established between ALS metrics and ground reference observations of forest attributes, and wall-to-wall predictions can be made over large areas. However, the prediction errors may be influenced by terrain slope and aspect because the properties of the ALS point cloud are dependent on these factors. Two datasets covering wide ranges of terrain slope and aspect, collected in the western part of Norway, were analysed. The first dataset represented sample plots from an ordinary operational forest management inventory and the second dataset were collected as an experimental dataset where clusters of sample plots were distributed on slopes with different inclinations. Six forest attributes were predicted using non-linear regression and the prediction errors were analysed using univariate- and multivariate analysis of variance. The results showed that slope and aspect affected the prediction errors, but that the effects were small in magnitude. Thus, the current study concludes that terrain effects seem to be negligible in operational forest inventories.

Description: We investigated the latitudinal variation in radial growth phenology (onset, cessation, and duration of radial growth) of Cryptomeria japonica D. Don trees in Japan. The radial growth was observed using dendrometers in 16 stands at multiple latitudes throughout Japan. The onset of radial growth showed a clear latitudinal gradient: at high-latitude sites, C. japonica growth started later than at low-latitude sites. However, cessation of radial growth was independent of latitude. Consequently, the duration of radial growth (defined based on the onset and cessation dates) showed a weak but significant latitudinal gradient: at high-latitude sites, C. japonica trees grew for a shorter period than trees at low-latitude sites. The onset and duration of growth were respectively strongly and weakly affected by temperature, although growth cessation was not explained by temperature or precipitation. The latitudinal gradient for duration of radial growth weakly but significantly supports the hypothesis that regional variation in growth phenology is a key factor responsible for the regional variation in long-term growth. Furthermore, we found that growth duration was more variable at low latitudes than at high latitudes.

Description: We developed a life-cycle analysis (LCA) system to quantify the carbon dynamics for Canadian-made harvested wood products (HWP). We considered the carbon stocks of HWP in use and in landfills/dumps, emissions reduced by substituting HWP for non-wood construction materials, HWP production emissions and methane emissions from decomposing wood disposed of in landfills. Carbon dynamics analyses were conducted for five HWP production scenarios. Results indicate structural panels have the highest potential in mitigating greenhouse gases (GHG) emissions, followed by lumber and non-structural panels. Net GHG effects of Canadian-made HWP were evaluated by integrating HWP carbon dynamics with forest carbon analysis using four forest management units (a total of 2.21 million ha of forests managed for timber production) from Ontario, Canada, as a case study. If HWP substitution benefits were estimated using the average displacement factor, and the wood obtained by increasing harvesting (relative to the baseline harvest scenario) in these four management units is used for structural panel, lumber, non-structural panel and business as usual HWP production, 0, 21, 39 and 84 years are needed to achieve net emission reductions, respectively; net emission reductions were, respectively, estimated to be 112, 93, 66 and 21 Mt CO 2 -equivalent in 100 years. Our results suggest harvesting sustainably managed forests in Canada to produce long-lived solid HWP can significantly contribute to GHG mitigation.

Description: Bark stripping behaviour of bears, which may significantly reduce the value of timber, has been reported mostly from North America and Japan, but in recent decades also from Europe. We surveyed forest plots in the Bieszczady Mountains of southeast Poland and recorded bark stripping by brown bears. We distinguished two types of tree damage by brown bears – damage to single (since no other damaged trees were found in their vicinity) and groups of trees (when five or more damaged trees were found in a small area). We found that all wound parameters, but especially the wound area and the proportion of the trunk with missing bark, were greater on single damaged trees. Comparison of damaged and control tree plots (1000 m 2 ) revealed that bears foraged in stands where silver firs ( Abies alba Mill.) with larger circumferences were present. Moreover, in stands where damage occurred, bears tended to strip large trees. The preference ratio index clearly showed that bears mostly preferred to forage on firs with circumferences in the 120–180 cm range, even though a wide spectrum of tree circumferences were available. Our results suggest that the brown bear should not be viewed as a pest species in commercial tree stands in Poland. The trees preferred by bears for foraging are large enough for timber production. To minimize economical losses, forestry personnel should regularly monitor tree stands that consist of trees of dimensions preferred by bears.

Description: Ecosystem services (ES) are the benefits that people receive from ecosystems. Understanding the impact of forest management on their supply can inform policy and practice for meeting societal demand. The objectives of this paper are to identify and review the effect of management intensity on priority ES supply and identify synergies and trade-offs among ES of different management approaches. We review seven priority ES identified from UK land and forestry strategy and policy documents: timber/biomass production, carbon storage, biodiversity, health and recreation, water supply and quality and flood protection. We present a synthesis of the impact of management on relative ES supply. It shows that low intensity management is unsuitable for high biomass production, yet provides high or moderately high levels of other services. Higher intensity management impacts negatively on biodiversity, health and recreation and water supply services. Combined objective forestry provides high or moderately high levels for all services except biomass. We recommend that a diversity of management approaches is needed to maintain multiple ecosystem service provision. The ES framework offers opportunities to forest management by revealing areas of conflict or co-production and potential trade-offs that may arise from adjusting management intensity.

Description: Digital hemispherical photography is a valuable method for monitoring changes in the biosphere’s response to climate change. In forests, cameras have often been fitted to existing towers and masts. However, such towers are logistically difficult and expensive to install. Ground-based automatic camera systems offer an alternative that removes the barriers associated with above-canopy photography, but to date there have been few comparisons between upward- and downward-facing images at the same site. This study addresses this issue, by comparing a pair of cameras, one ground-based, one tower-based, viewing the same trees in a deciduous oak ( Quercus robur L.) plantation forest in south-eastern England. Over 6 years, the upward-facing ground-based camera system was able to detect key spring phenological events to the same extent as the more usual downward-facing camera (mean difference of 2 days for green-up date). However, the upward- and downward-facing systems were less well-matched in detecting specific events at the end of the growing season, although both systems displayed similar temporal trends. Upward-facing cameras can therefore act as a reliable and comparable alternative to tower-based phenocam systems, as well as being more suitable for wider spatial coverage without the need for expensive installation infrastructure. In addition to the increased ease of access with upward-facing camera systems, the images from them also allow canopy structural dynamics such as canopy closure to be estimated.

Description: The growth of Sitka spruce ( Picea sitchensis (Bong.) Carr.) on nutrient-poor sites in the British Isles is often improved during the late establishment phase when grown in intimate (‘nursing’) mixture with pioneer species such as pines and larches. However, there is very little information on the longer term effects of such mixtures on stand development and productivity. Therefore, we analysed results from four experiments established in northern Scotland in the 1960s which included nursing mixtures of Sitka spruce with Scots pine ( Pinus sylvestris L.), lodgepole pine ( Pinus contorta Dougl.) or larches ( Larix spp.), as well as plots of pure Sitka spruce given different establishment regimes, sometimes including nitrogen fertilization. At three nutrient-poor sites, spruce in nursing mixture was significantly taller after 15 years than pure spruce without nitrogen. Analysis of foliar nitrogen status showed that pure spruce without nitrogen became deficient by ~8–10 years with no recovery for at least 20 years. Spruce grown in mixture also showed an initial nitrogen deficiency, but with recovery by 10–15 years to optimal or marginal levels. After more than 40 years growth, on the nutrient-poor sites the basal areas in the nursing mixtures were significantly higher than pure spruce without remedial nitrogen and comparable to those of pure spruce given several applications of nitrogen, However, these differences were not evident at the more fertile site. Nearly all mixed plots self-thinned towards dominance by Sitka spruce. The magnitude of this nursing effect is striking and harnessing the mechanisms underpinning this effect could be very important for sustaining productivity of forests on nutrient-poor soils in upland Britain.

Description: The habitat composition of mature non-native plantations may provide a different set of resources to that of native forests, and these differences may influence species communities. We studied a bird community in the northern Iberian Peninsula to understand whether habitat composition in either mature non-native plantations or native forests generated differences in the habitat associations of each bird species as well as the composition of the bird community. We sampled 140 4-ha plots, measuring habitat composition at both the canopy and the understory level using remote sensing data and field surveys, respectively. Using a fixed census in each plot, we also studied the bird species composition and analysed the species-specific associations for various habitat variables at the canopy and understory level. We found that mature plantations differed in understory level from native forest, but these differences in habitat did not translate into differences in bird species composition between forest types. Species–habitat associations were on average stronger at the understory compared to the canopy level, which suggests that a combination of field and remote sensing data might better represent the species-specific response to forest resources when measuring the assembly of bird communities in mature plantations. This work suggests the fact that the combination of different levels of forest resources, such as that provided by mature non-native plantations and native forests, is able to support a rich bird community.

Description: The genus Eucalyptus contains many timber-producing forest species and is extensively planted around the world. The domestication of Eucalyptus has facilitated the global movement of microorganisms associated with this genus. The objective of this study was to characterize the fungal microbes in soil under the economically important tree, Eucalyptus grandis , from Zimbabwe. Soil samples were collected from a 5-year E . grandis plantation and adjacent Miombo woodland, which was treated as the control. The internal transcribed spacer 1 (ITS1) nuclear encoded ribosomal RNA of the fungal communities in the soil was sequenced using the high-throughput Illumina MiSeq technology. Taxonomic composition assessment of reads recovered from soil under E. grandis revealed the dominance of Ascomycota (41.17%), Basidiomycota (20.73%), with very few sequences belonging to Chytridiomycota, Rozellomycota and Zygomycota. Miombo soil was composed of Ascomycota (74.89%) and Basidiomycota (19.08%), also with very few sequences from Chytridiomycota, Rozellomycota and Zygomycota. Fungi belonging to Davidiellaceae, Mycosphaerellaceae and Teratosphaeriaceae, families that are known to be pathogenic to Eucalyptus , were recovered in soil under E . grandis . Ectomycorrhizal fungi classified in the Agaricomycetes were especially abundant in the Eucalyptus soil and were dominated by the genera Pisolithus and Scleroderma , which have been reported as Eucalyptus associates before.

Description: Decoupled direct payments are a major tool of agricultural policy to support farm income. Since these subsidies are tied to land, the question arises as to who benefits from them when farmers are not the landowners. While theoretical models commonly predict that most of the payments transfer to land prices, empirical findings show that this incidence is low instead. Approaching the issue from the perspective of spatial competition, this paper produces results consistent with empirical evidence. Incidence varies with the competitiveness of the market, ranging from perfect subsidy transfer under specific conditions to low or zero incidence for most of the cases considered.

Description: Rapid biodiversity assessment (RBA) methods are regularly applied to assess plant species richness. One approach is developing sampling designs that integrate expert knowledge. 3P sampling does so by selecting samples with probability proportional to prediction (3P). Higher effort is allocated to areas with high species richness based on predictions made on the ground. 3P sampling for RBA was simulated considering two major factors: knowledge of plant species and types of rapid assessment. Two large census forest plots over 25 ha in size were used. Results showed that sampling error of 3P sampling for RBA was relatively low and could be improved by changing methods of prediction. Sampling was more efficient and accurate when predictions were made with knowledge about abundant species instead of random species. When such prediction was made, knowing only three quarters of the total species richness in a forest performed as well as full knowledge. Randomly walking around in an area and predicting also increased efficiency and accuracy compared to standing stationary at an assessment point. This was counterintuitive to the common practices of establishing ground plots for assessment. Our findings propose that 3P sampling for RBA is workable through engaging local communities in an assessment, which could be cost-effective. Finally, the procedure laid out in this study is the first unequal probability sampling design proposed for RBA.

Description: Previous studies suggest that when using natural regeneration of Korean pine ( Pinus koraiensis Sieb. et Zucc.) many seeds do not germinate until the second Spring after dispersal and hence are subject to significant predation pressures. This could be an important factor affecting the restoration of Mixed-broadleaved Korean pine forests in northeast China. This study examined changes of dormancy status under laboratory and field conditions as well as physiological mechanisms involving abscisic acid (ABA), gibberellin acids (GA 1+3 , GA 4+7 ) and the storage reserves of seeds. Our results suggest that seeds of Korean pine have primary dormancy that can be classified as morphophysiological dormancy, i.e. when dispersed they have an underdeveloped embryo with a physiological component of dormancy. A proportion of seeds germinate in the first year after dispersal as the winter chill has broken the physiological dormancy but only when the embryo has had time to elongate in April–June. The remaining seeds germinate in the second Spring after dispersal when embryos are fully developed and the physiological dormancy imposed in the Summer after dispersal has been broken by winter chilling. Thus the seed strategy of Korean pine attempts to reduce risks by providing opportunities for germination in 2 years following dispersal.

Description: This study examines the potential of airborne laser scanning (ALS) to predict diameter distributions in an even-aged plantation of Eucalyptus urograndis in Brazil. The single-species plantation conditions allow different modelling alternatives to be compared without the presence of minor tree species or an understory layer affecting the results. Three modelling alternatives based on the two-parametric Weibull function form; parameter prediction, parameter recovery and distribution matching were tested with a k-nearest neighbour prediction ( k-nn ) method. We also evaluated a parameter prediction alternative, in which the Weibull distribution was predicted using field attributes. The results showed that ALS information can predict diameter distributions with an error margin of slightly more than 10 per cent of the RMSE of the mean of the third power of diameter, and with error index values between 50 and 60. The degree of accuracy was only slightly improved when the Weibull distribution was predicted using field attributes. According to the accuracy metrics, the differences between modelling alternatives were minor but parameter recovery and k-nn seem to be the most favourable ALS-based prediction methods. To conclude, the results showed a strong relationship between ALS information and diameter distributions in a tropical single-species plantation and we discuss how these results could be applied in other types of forests.

Description: Tree height can be a time-consuming measurement to obtain accurately in the field. Thus, height–diameter equations are frequently used to minimize costs associated with inventories and to reduce problems associated with height measurement errors. In this analysis, we compare three methods for estimating height from diameter data for a variety of species: (1) a nonlinear mixed-effects (NLME) model; (2) k nearest neighbour (KNN) imputation; and (3) a copula model. Predicted height values were compared with field height measurements for 922 trees across 24 species using paired point-wise and distribution-based goodness-of-fit criteria. All approaches performed very well, with the NLME and KNN imputation having better point-wise goodness-of-fit measures. Copula models, although generally poorer in terms of the paired point-wise goodness-of-fit, adequately predicted height values, maintained variances observed in field data, and showed the least loss of functionality when applied to species with sparse data or data with atypical parameters. Overall, the copula approach is flexible and may be more appropriate for estimating heights where paired point estimate accuracy is less important such as for tree lists that are subsequently used as inputs into growth and yield models.

Description: Beech bark disease stunts American beech ( Fagus grandifolia Ehrh.) to unmerchantable size, and promotes heavy sprouting that outcompetes more desirable sugar maple ( Acer saccharum Marsh.) and yellow birch ( Betula alleghaniensis Britt.). We investigated whether selection harvest targeting removal of large beech can promote maple and birch regeneration while limiting beech competition. Forty plots were established in 2003 in north-western New Brunswick, Canada, with 26 plots harvested and 14 control plots. Harvested plots were re-measured the year after harvest and both harvested and control plots were re-measured 10 years later. Residual tree diameter increment doubled from 0.24 to 0.51 cm/year for maple, and 0.29 to 0.69 cm/year for birch. Harvest did not alter species composition of regeneration, with seedlings comprised of 88 per cent sugar maple in both treatments, 6 per cent beech in harvested plots vs 3 per cent in control plots, and other species ranging from 1 to 5 per cent. There were four times more beech seedlings/ha in control than in harvested plots, but beech still comprised ~60 per cent of the over 2000 stems/ha of saplings in harvested plots. Rapid growth from beech sprouts provided a strong competitive advantage. Residual tree mortality was negligible. Downed deadwood was 58 per cent greater and standing deadwood basal area 71 per cent lower in harvested plots. The harvest maintained strong overstory growth and survival, and did not benefit beech; however, beech remained a dominant species among the larger regenerating cohort. Our results suggest that similar treatments applied to stands with diseased beech can secure adequate regeneration of maple and birch, but will not control profuse regeneration of beech.

Description: Spruce budworm (SBW; Choristoneura fumiferana [Clem.]) defoliation begins at the top of the crown, and often results in leader death, loss of annual height growth or gradual top dieback, known as topkill. We used regression tree analysis to examine topkill incidences during a severe SBW outbreak in Nova Scotia, Canada in the 1970s–1980s that resulted in 60–100 per cent mortality of merchantable balsam fir ( Abies balsamea (L.) Mill.) volume, and re-examined surviving trees for defects 25 years later. At the study outset in 1979, 4–6 years into the SBW outbreak, stand level topkill ranged from 40 to 88 per cent of trees and mean individual-tree topkill probability was 7, 52, 79 and 87 per cent on trees with ≤25, 26–75, 76–90 and 91–100 per cent total defoliation (all age classes of foliage). By 1987, the SBW outbreak had ended and mortality probability of trees was 12, 59, 85 and 98 per cent for classes of peak total defoliation of ≤25, 26–75, 76–90 or 91–100 per cent. Most mortality occurred following 6–8 years of defoliation, but topkill peaked after 4–6 years, indicating that topkill required less cumulative defoliation than death. When the plots were remeasured in 2012, 25 years later, 90 per cent of the surviving trees with documented topkill during the SBW outbreak had stem defects, of which 26 per cent were crooks, 53 per cent forks and 21 per cent sweeps. From 32 to 88 per cent of stem length was located above the point of the defect, resulting in the long-term downgrading of topkill-damaged logs.

Description: The economic importance of cork in the Mediterranean region demands an accurate assessment of its production. Cork production is currently estimated by aggregating information provided by Regional Forest Services, but this approach results in a lack of robustness at the national level. The objective of the present study is to analyse the role of the Spanish National Forest Inventory (SNFI) as a potential source of data for quantifying cork weight at national level and the scope of National Forest Inventory data to define national trends in cork yield as well as to characterize the main types of cork producing forest stands in Spain. Data from the Second and Third SNFI are used together with the Spanish Forest Map. The results point to the suitability of SNFI to quantify cork production as long as the two main variables defining cork weight, namely cork thickness and debarking height, were correctly recorded in inventories. Although the Second SNFI complied with these requirements, from the Third SNFI the methodology changed, preventing the accurate estimation of cork weight. Based on this study recommendations are made to improve the estimation of cork weight at national level, e.g. to measure cork thickness in all the cork oaks in the plot and to take a sample of cork from the inventoried trees. This information would also make it possible to assess the cork quality in terms of cork thickness growth and to classify cork production in terms of suitability for producing high quality cork products.

Description: A plethora of forest models were developed by transforming the dependent variable, which introduces bias if appropriate corrections are not applied when back-transformed. Many recognized models are still biased and the original data sets are no longer available, which suggests ad hoc bias corrections. The present research presents a procedure for bias correction in the absence of needed information from summary statistics. Additionally, we developed a realistic correction of the square root transformation based on a truncated normal distribution. The transformations considered in this study are the logarithm, the square root and arcsine square root. Using simulated data we found that uncorrected back-transformation created biases by as much as 100 percent. The generated data revealed that depending on available information, that bias can still be present after correction. In addition to generated data we corrected the site index of Douglas-fir and ponderosa pine in Oregon USA, tree volume of 27 species from Romania, stand merchantable volume for longleaf pine in Louisiana and East Texas USA, and canopy fuel weight in Washington USA. Using only the available information, the unbiased back-transformed estimates can change from ≤1 percent (i.e. the site index and canopy fuel weight) to ≥⅓ (tree and stand volume).

Description: One of many possible climate change effects in temperate areas is the increase of frequency and severity of windstorms; thus, fast and cost efficient new methods are needed to evaluate wind-induced damages in forests. We present a method for assessing windstorm damages in forest landscapes based on a two-stage sampling strategy using single-date, post-event airborne laser scanning (ALS) data. ALS data are used for delineating damaged forest stands and for an initial evaluation of the volume of fallen trees. The total volume of fallen trees is then estimated using a two-stage model-assisted approach, where variables from ALS are used as auxiliary information in the difference estimator. In the first stage, a sample of the delineated forest stands is selected, and in the second stage the within-stand damages are estimated by means of line intercept sampling (LIS). The proposed method produces maps of windthrown areas, estimates of forest damages in terms of the total volume of fallen trees, and the uncertainty of the estimates. A case study is presented for a large windstorm that struck the Tuscany Region of Italy the night of the 4th and the 5th of March 2015 and caused extensive damages to trees in both forest and urban areas. The pure field-based estimates from LIS and the ALS-based estimates of stand-level fallen wood were very similar. Our positive results demonstrate the utility of the single-date approach for a fast assessment of windthrow damages in forest stands which is especially useful when pre-event ALS data are not available.

Description: Climate change may reduce the benefits of tree improvement. We investigated the response to limited water availability of seedlings from nine improved full-sibling families of Sitka spruce ( Picea sitchensis (Bong.) Carr.) plus an unimproved seed lot (‘Washington control’). Seedlings were 1-year old at the start of the imposition of two water availability treatments, which were maintained for 2.5 years: full irrigation, in which all water transpired was replaced, and water limitation, in which irrigation was provided to match only 30% of the transpiration of the Washington control under full irrigation. Both family and water availability affected leader extension rate, height, root collar diameter and total dry mass at the end of the following 2 years. Water limitation reduced leaf area and fresh mass per unit stem length and delayed bud flush. Specific leaf area was affected by water limitation earlier but not later in the experiment; the reverse was true of root to shoot ratio and numbers of primordia. Under full irrigation, five improved families maintained superiority over the Washington control in terms of height, root collar diameter and total biomass at the end of the experiment. Under water limitation, however, by the end of the experiment, seedlings from the improved families had no greater total biomass than those of the Washington control, reflecting the homogenizing impact of water limitation on production of leader biomass. Thus, for Sitka spruce, planting the most vigorous material will maximize gains under optimal conditions, but have little benefit in stress conditions.

Description: Pests and pathogens are an increasing threat to trees and forests, and the associated biodiversity and ecosystem services. Producing trees that are resistant to such threats is frequently emphasized by policymakers across Europe and North America. However, there are several approaches for developing and deploying resistant trees, and the process can be time-consuming and potentially complex and controversial. Here, we provide a framework to inform the selection of the most suitable approaches in different contexts, highlighting important constraints and considerations associated with using resistant trees. We identify six common steps within resistant tree programmes, and for each step discuss a range of options. Our proposed framework emphasizes interdependencies amongst these steps, and can inform decisions and approaches in proposed and ongoing resistance programmes. We also highlight potential pitfalls in the use of resistant trees, including: low durability of resistance, low viability against other threats, lack of acceptability/demand from forest owners and the public, and negative ecological impacts. Lastly, we emphasize the need to evaluate resistant trees alongside complementary strategies for mitigating the impacts of pests and pathogens (e.g. biosecurity, maintenance of adaptive capacity), and in the context of the other anthropogenic pressures faced by trees and forests.

Description: Pine wilt disease (PWD) is caused by the nematode Bursaphelenchus xylophilus , an invasive pest that currently constitutes the greatest threat to pine forests worldwide. Breeding for resistance to the nematode is one of the main strategies for coping with this disease in most severely affected countries. This work evaluates genetic variation in susceptibility to B. xylophilus among 91 half-sib families from a Pinus pinaster breeding population that was selected for growth and stem form in Galicia (NW Spain). We performed artificial inoculations on these families to evaluate mortality, disease development, and their relationships both to physiological variables measured throughout the experiments and morphological traits assessed prior to inoculation. The results showed significant differences among families in almost all estimated variables and reasonably high (varying from 0.45 to 0.87) family heritability for morphological traits, mortality and wilting symptoms. Some of the families presented high tolerance to B. xylophilus , suggesting that a breeding programme for tolerance to pinewood nematode could be an important control strategy for managing PWD in Spain. However, mortality correlated positively with tree height and negatively with the number of branches, which may indicate that current breeding selection criteria could be negatively affecting tolerance to PWD. Chlorophyll fluorescence and oleoresin flow were useful tools for assessing the physiological condition of the trees after pinewood nematode infection.

Description: The estimation model of crop yields is a prerequisite for deriving actuarially sound insurance premiums. A major challenge in estimating crop yield models arises from the non-stationarity of the data generating process due to technological change and climate change. In this paper, we introduce an adaptive local parametric approach to deal with the non-stationarity of crop yields. An empirical application to major crops in the USA indicates that yield risks for corn and cotton are decreasing, but are increasing for winter wheat. A rating analysis suggests that the proposed model shows potential to obtain more accurate rates than commonly used methodology.

Description: Energy economics is a vast topic. Many applied and agricultural economists today work on fuel economy, fossil fuel energy issues, energy sector economic analysis, electricity sector economic and policy issues, techno-economic analyses of energy alternatives as well as agricultural energy issues such as biofuels, and energy use in agriculture. Energy economists also employ a wide variety of modeling and analytical tools. We cover six broad topics: externalities, policy analysis, energy demand and supply analyses, electricity pricing, biofuels, and techno-economic analysis. Applied and agricultural economists have made and will continue to make major contributions to the literature and policy analysis in these areas.

Description: International trade is likely to be a hugely important and interesting area for research by agricultural and applied economists in the next decade. While the questions for research are likely to change—with less emphasis on large-scale international negotiations and more on national reforms and regional agreements—there will be important challenges in understanding the driving forces for world agricultural markets, in trade policy, and in ensuring food security. New analytical techniques built on the gravity model and geospatial production data create many opportunities for innovative applications and expand the range of questions to which researchers in this field can effectively respond.

Description: Sustainable development can be attained by policies that are derived by analyses that integrate biophysical considerations into economic models. We show that policies and incentives that correct market failure can attain sustainable development through enhancing conservation, recycling, the use of renewable resources, and development of the bioeconomy, which relies on biological processes and feedstock to produce renewable products. The design of sustainable development policies and analysis of the bioeconomy pose new challenges to applied economists, who are uniquely qualified to integrate economic analysis with biophysical considerations.

Description: To set the stage for future research aimed at developing public policies that support economic prosperity in rural areas, we review the current economic conditions of rural America and the current literature. Rural America is often characterized as a uniform, distressed place where agriculture dominates. In fact, rural America is diverse, with many regions doing well economically. In some areas, labor-saving technologies have reduced the workforce in manufacturing and resource-dependent industries. However, integration with urban areas has weakened the economic divide between urban and some rural areas, while natural amenities have boosted the fortunes of others. There is also evidence that homegrown enterprises can support growth even in the most remote, distressed regions. To support economic growth, policies should recognize the unique features of each place or region and balance the farm sector with the larger nonfarm rural economy. Economists are well-positioned to provide research-based evidence of what works, as well as rigorous evaluation of new polices.

Description: Mangrove species have developed uniquely efficient water-use strategies in order to survive in highly saline and anaerobic environments. Herein, we estimated the stand water use of two diffuse-porous mangrove species of the same age, Sonneratia apetala Buch. Ham and Sonneratia caseolaris (L.) Engl., growing in a similar intertidal environment. Specifically, to investigate the radial patterns of axial sap flow density ( J s ) and understand the anatomical traits associated with them, we measured axial sap flow density in situ together with micromorphological observations. A significant decrease of J s was observed for both species. This result was accompanied by the corresponding observations of wood structure and blockages in xylem sapwood, which appeared to influence and, hence, explained the acute radial reductions of axial sap flow in the stems of both species. However, higher radial resistance in sapwood of S. caseolaris caused a steeper decline of J s radially when compared with S. apetala , thus explaining the latter’s more efficient use of water. Without first considering acute reductions in J s into the sapwood from the outer bark, a total of ~55% and 51% of water use would have been overestimated, corresponding to average discrepancies in stand water use of 5.6 mm day −1 for S. apetala trees and 2.5 mm day −1 for S. caseolaris trees. This suggests that measuring radial pattern of J s is a critical factor in determining whole-tree or stand water use.

Description: We investigated the dynamics of xylem differentiation processes and vessel characteristics in Fagus sylvatica L. to evaluate the plasticity of xylem structures under different environmental conditions. In 2008–10, analyses were performed on microcores collected weekly from two temperate sites: Menina planina (1200 m above sea level (a.s.l.)) and Panska reka (400 m a.s.l.). The duration between the onset and end of major cell differentiation steps and vessel characteristics (i.e., density, VD; mean diameter, MVD; mean area, MVA; and theoretic conductivity area, TCA) were analysed in the first and last quarters of the xylem rings, also in respect of local weather conditions (precipitation, temperature). Although the onset, duration and end of xylem formation phases differed between the two sites, the time spans between the successive wood formation phases were similar. Significant differences in MVD, MVA and TCA values were found between the first and last quarters of xylem increment, regardless of the site and year. Vessel density, on the other hand, depended on xylem-ring width and differed significantly between the sites, being about 30% higher at the high elevation site, in beech trees with 54% narrower xylem rings. Vessel density in the first quarter of the xylem ring showed a positive correlation with the onset of cell expansion, whereas a negative correlation of VD with the cessation of cell production was found in the last quarter of xylem increment. This may be explained by year-to-year differences in the timing of cambial reactivation and leaf development, which effect hormonal regulation of radial growth. No significant linkage between intra-annual weather conditions and conduit characteristics was found. It can thus be presumed that precipitation is not a limiting factor for xylem growth and cell differentiation in beech at the two temperate study sites and sites across Europe with similar weather conditions.

Description: A better understanding and prediction of the impact of changing climate on tree stem growth could greatly benefit from the combination of anatomical and ecophysiological knowledge, yet the majority of studies focus on one research field only. We propose an approach that combines the method of pinning (cambial wounding) to timestamp anatomical X-ray computed microtomography images with continuous measurements of sap flow and stem diameter variations. By pinning the cambium of well-watered and drought-treated young African tropical trees of the species Maesopsis eminii Engl. we could quantify wood formation during a specific period of time and relate it to tree physiology and prevailing microclimate. Integrating continuous plant measurements and high-frequency pinning proved very useful to visualize and quantify the effects on stem growth of drought in M. eminii . Wood formation completely stopped during drought, and was associated with a strong shrinkage in stem diameter. Next, an unexpected increase in stem diameter was observed during drought, probably caused by root pressure, but not accompanied by wood formation. Our proposed approach of combining continuous plant measurements with cambial pinning is very promising to relate ecophysiology to stem anatomy and to understand the mechanisms underlying tree stem growth and bridge the gaps between the two research fields.

Description: The ability of trees to cope with climate change is a pivotal feature of forest ecosystems, especially for rear-edge populations facing warm and dry conditions. To evaluate current and future forests threats, a multi-proxy focus on the growth, anatomical and physiological responses to climate change is needed. We examined the long-term xylem adjustments to climate variability of the temperate Quercus robur L. at its rear edge and the sub-Mediterranean Quercus pyrenaica Willd. Both species coexist at a mesic (ME, humid and warmer) and a xeric (XE, dry and cooler) site in northern Spain, the latter experiencing increasing temperatures in recent decades. We compared xylem traits at each site and assessed their trends, relationships and responses to climate (1960–2008). Traits included basal area increment, earlywood vessel hydraulic diameter, density and theoretical-specific hydraulic conductivity together with latewood oxygen (δ 18 O) stable isotopes and δ 13 C-derived water-use efficiency (iWUE). Quercus robur showed the highest growth at ME, likely through enhanced cambial activity. Quercus pyrenaica had higher iWUE at XE compared with ME, but limited plasticity of anatomical xylem traits was found for the two oak species. Similar physiological performance was found for both species. The iWUE augmented in recent years especially at XE, likely explained by stomatal closure given the increasing δ 18 O signal in response to drier and sunnier growing seasons. Overall, traits were more correlated at XE than at ME. The iWUE improvements were linked to higher growth up to a threshold (~85 μmol mol –1 ) after which reduced growth was found at XE. Our results are consistent with Q. pyrenaica and Q. robur coexisting at the central and dry edge of the climatic species distribution, respectively, showing similar responses to buffer warmer conditions. In fact, the observed adjustments found for Q. robur point towards growth stability of similar rear-edge oak populations under warmer climate conditions.

Description: In alpine regions, tree hydraulics are limited by low temperatures that restrict xylem growth and induce winter frost drought and freezing stress. While several studies have dealt with functional limitations, data on elevational changes in functionally relevant xylem anatomical parameters are still scarce. In wood cores of Pinus cembra L. and Picea abies (L.) Karst. trunks, harvested along five elevational transects, xylem anatomical parameters (tracheid hydraulic diameter d h , wall reinforcement ( t / b ) 2 ), pit dimensions (pit aperture D a , pit membrane D m and torus D t diameters) and respective functional indices (torus overlap O , margo flexibility) were measured. In both species, tracheid diameters decreased and ( t / b ) 2 increased with increasing elevation, while pit dimensions and functional indices remained rather constant ( P. cembra : D t 10.3 ± 0.2 μm, O 0.477 ± 0.005; P. abies : D t 9.30 ± 0.18 μm, O 0.492 ± 0.005). However, d h increased with tree height following a power trajectory with an exponent of 0.21, and also pit dimensions increased with tree height (exponents: D m 0.18; D t 0.14; D a 0.11). Observed elevational trends in xylem structures were predominantly determined by changes in tree size. Tree height-related changes in anatomical traits showed a remarkable robustness, regardless of the distributional ranges of study species. Despite increasing stress intensities towards the timberline, no adjustment in hydraulic safety at the pit level was observed.

Description: Decreasing water availability due to climate change poses the question of whether and to what extent tree species are able to hydraulically acclimate and how hydraulic traits of stems and leaves are coordinated under drought. In a through-fall exclusion experiment, hydraulic acclimation was analyzed in a mixed forest stand of Fagus sylvatica L. and Picea abies (L.) Karst. In drought-stressed (TE, through-fall exclusion over 2 years) and control (CO) trees, hydraulic vulnerability was studied in branches as well as in leaves ( F. sylvatica ) and end-twigs ( P. abies , entirely formed during the drought period) sampled at the same height in sun-exposed portions of the tree crown. In addition, relevant xylem anatomical traits and leaf pressure–volume relations were analyzed. The TE trees reached pre-dawn water potentials down to −1.6 MPa. In both species, water potentials at 50% loss of xylem hydraulic conductivity were ~0.4 MPa more negative in TE than in CO branches. Foliage hydraulic vulnerability (expressed as water potential at 50% loss of leaf/end-twig hydraulic conductance) and water potential at turgor loss point were also, respectively, 0.4 and 0.5 MPa lower in TE trees. Minor differences were observed in conduit mean hydraulic diameter and cell wall reinforcement. Our findings indicate significant and fast hydraulic acclimation under relatively mild drought in both tree species. Acclimation was well coordinated between branches and foliage, which might be essential for survival and productivity of mature trees under future drought periods.

Description: Insertion of thermal dissipation (TD) sap flow sensors in living tree stems causes damage of the wood tissue, as is the case with other invasive methods. The subsequent wound formation is one of the main causes of underestimation of tree water-use measured by TD sensors. However, the specific alterations in wood anatomy in response to inserted sensors have not yet been characterized, and the linked dysfunctions in xylem conductance and sensor accuracy are still unknown. In this study, we investigate the anatomical mechanisms prompting sap flow underestimation and the dynamic process of wound formation. Successive sets of TD sensors were installed in the early, mid and end stage of the growing season in diffuse- and ring-porous trees, Fagus sylvatica (Linnaeus) and Quercus petraea ((Mattuschka) Lieblein), respectively. The trees were cut in autumn and additional sensors were installed in the cut stem segments as controls without wound formation. The wounded area and volume surrounding each sensor was then visually determined by X-ray computed microtomography (X-ray microCT). This technique allowed the characterization of vessel anatomical transformations such as tyloses formation, their spatial distribution and quantification of reduction in conductive area. MicroCT scans showed considerable formation of tyloses that reduced the conductive area of vessels surrounding the inserted TD probes, thus causing an underestimation in sap flux density (SFD) in both beech and oak. Discolored wood tissue was ellipsoidal, larger in the radial plane, more extensive in beech than in oak, and also for sensors installed for longer times. However, the severity of anatomical transformations did not always follow this pattern. Increased wound size with time, for example, did not result in larger SFD underestimation. This information helps us to better understand the mechanisms involved in wound effects with TD sensors and allows the provision of practical recommendations to reduce biases associated with wounding in field sap flow measurements.

Description: Climate change is expected to increase the frequency and intensity of droughts and heatwaves in Europe, leading to effects on forest growth and major forest dieback events due to hydraulic failure caused by xylem embolism. Inter-specific variability in embolism resistance has been studied in detail, but little is known about intra-specific variability, particularly in marginal populations. We evaluated 15 European beech populations, mostly from geographically marginal sites of the species distribution range, focusing particularly on populations from the dry southern margin. We found small, but significant differences in resistance to embolism between populations, with xylem pressures causing 50% loss of hydraulic conductivity ranging from −2.84 to −3.55 MPa. Significant phenotypic clines of increasing embolism resistance with increasing temperature and aridity were observed: the southernmost beech populations growing in a warmer drier climate and with lower habitat suitability have higher resistance to embolism than those from Northern Europe growing more favourable conditions. Previous studies have shown that there is little or no difference in embolism resistance between core populations, but our findings show that marginal populations have developed ways of protecting their xylem based on either evolution or plasticity.

Description: In stands with a broad range of diameters, a small number of very large trees can disproportionately influence stand basal area and transpiration ( E t ). Sap flow-based E t estimates may be particularly sensitive to large trees due to nonlinear relationships between tree-level water use ( Q ) and tree diameter at breast height (DBH). Because Q is typically predicted on the basis of DBH and sap flow rates measured in a subset of trees and then summed to obtain E t , we assessed the relative importance of DBH and sap flow variables (sap velocity, V s , and sapwood depth, R s ) in determining the magnitude of E t and its dependence on large trees in a tropical montane forest ecosystem. Specifically, we developed a data-driven simulation framework to vary the relationship between DBH and V s and stand DBH distribution and then calculate Q , E t and the proportion of E t contributed by the largest tree in each stand. Our results demonstrate that variation in how R s is determined in the largest trees can alter estimates up to 26% of E t while variation in how V s is determined can vary results by up to 132%. Taken together, these results highlight a great need to expand our understanding of water transport in large trees as this hinders our ability to predict water fluxes accurately from stand to catchment scales.

Description: Dutch elm disease (DED) is a vascular disease that has killed over 1 billion elm trees. The pathogen spreads throughout the xylem network triggering vessel blockage, which results in water stress, tissue dehydration and extensive leaf wilting in susceptible genotypes. We investigated the differences between four Ulmus minor Mill. clones of contrasting susceptibility to Ophiostoma novo-ulmi Brasier regarding morphological, anatomical and physiological traits affecting water transport, in order to gain a better understanding of the mechanisms underlying DED susceptibility. We analyzed the differential response to water shortage and increased air vapor pressure deficit (VPD) to investigate whether resistance to water stress might be related to DED tolerance. Sixteen plants per clone, aged 2 years, were grown inside a greenhouse under differential watering. Stomatal conductance was measured under ambient and increased VPD. Growth, bark water content and stem hydraulic and anatomical parameters were measured 22 days after starting differential watering. Vessel lumen area, lumen fraction and hydraulic conductance were highest in susceptible clones. Stomatal conductance was lowest under low VPD and decreased faster under increased VPD in resistant clones. We found a negative relationship between the decrease in stomatal conductance at increased VPD and specific hydraulic conductance, revealing a narrower hydraulic margin for sustaining transpiration in resistant clones. The effect of water shortage was greater on radial stem growth than on leaf area, which could be explained through an extensive use of capacitance water to buffer xylem water potential. Water shortage reduced stomatal conductance and vessel lumen area. Bark water content under conditions of water shortage only decreased in susceptible clones. Higher hydraulic constraints to sap flow in resistant clones may determine higher stomatal sensitivity to VPD and so contribute to DED resistance by limiting pathogen expansion and reducing water loss and metabolic impairment in cells involved in fighting against infection.

Description: Wood density can be considered as a measure of the internal wood structure, and it is usually used as a proxy measure of other mechanical and functional traits. Eucalyptus is one of the most important commercial forestry genera worldwide, but the relationship between wood density and vulnerability to cavitation in this genus has been little studied. The analysis is hampered by, among other things, its anatomical complexity, so it becomes necessary to address more complex techniques and analyses to elucidate the way in which the different anatomical elements are functionally integrated. In this study, vulnerability to cavitation in two races of Eucalyptus globulus Labill. with different wood density was evaluated through Path analysis, a multivariate method that allows evaluation of descriptive models of causal relationship between variables. A model relating anatomical variables with wood properties and functional parameters was proposed and tested. We found significant differences in wood basic density and vulnerability to cavitation between races. The main exogenous variables predicting vulnerability to cavitation were vessel hydraulic diameter and fibre wall fraction. Fibre wall fraction showed a direct impact on wood basic density and the slope of vulnerability curve, and an indirect and negative effect over the pressure imposing 50% of conductivity loss (P 50 ) through them. Hydraulic diameter showed a direct negative effect on P 50 , but an indirect and positive influence over this variable through wood density on one hand, and through maximum hydraulic conductivity (k s max ) and slope on the other. Our results highlight the complexity of the relationship between xylem efficiency and safety in species with solitary vessels such as Eucalyptus spp., with no evident compromise at the intraspecific level.

Description: Water flow through xylem vessels encounters hydraulic resistance when passing through the vessel lumen and end wall. Comparative studies have reported that lumen and end wall resistivities co-limit water flow through stem xylem in several angiosperm woody species that have vessels of different average diameter and length. This study examined the intra-specific relationship between the lumen and end wall resistivities ( R lumen and R wall ) for vessels within the stem xylem using three deciduous angiosperm woody species found in temperate forest. Morus australis Poir. and Acer rufinerve Siebold et Zucc. are early- and late-successional species, and Vitis coignetiae Pulliat ex Planch is a woody liana. According to the Hagen–Poiseuille equation, R lumen is proportional to the fourth power of vessel diameter ( D ), whereas vessel length ( L ) and inter-vessel pit area ( A pit ) determine R wall . To estimate R lumen and R wall , the scaling relationships between the L and D and between A pit and D were measured. The scaling exponents between L and D were 1.47, 3.19 and 2.86 for A. rufinerve , M. australis and V. coignetiae , respectively, whereas those between A pit and D were 0.242, 2.11 and 2.68, respectively. Unlike the inter-specific relationships, the wall resistivity fraction ( R wall /( R lumen + R wall )) within xylem changed depending on D . In M. australis and V. coignetiae , this fraction decreased with increasing D , while in A. rufinerve , it increased with D . Vessels with a high wall resistivity fraction have high R wall and total resistivity but are expected to have low susceptibility to xylem cavitation due to a small cumulative A pit . In contrast, vessels with a low wall resistivity fraction have low R wall and total resistivity but high susceptibility to xylem cavitation. Because the wall resistivity fraction varies with D , the stem xylem contains vessels with different hydraulic efficiencies and safety to xylem cavitation. These features produce differences in the hydraulic properties of plants with different life forms.

Description: Mountain pine beetle ( Dendroctonus ponderosae Hopkins; MPB) is an economically and ecologically important pest of pine species in western North America. Mountain pine beetles form complex multipartite relationships with microbial partners, including the ophiostomoid fungi Grosmannia clavigera (Robinson-Jeffrey and Davidson) Zipfel, de Beer and Wingfield, Ophiostoma montium (Rumbold) von Arx, Grosmannia aurea (Robinson-Jeffrey and Davidson) Zipfel, de Beer and Wingfield, Leptographium longiclavatum (Lee, Kim, and Breuil) and Leptographium terebrantis (Barras and Perry). These fungi are vectored by MPB to new pine hosts, where the fungi overcome host defenses to grow into the sapwood. A tree’s relative susceptibility to these fungi is conventionally assessed by measuring lesions that develop in response to fungal inoculation. However, these lesions represent a symptom of infection, representing both fungal growth and tree defense capacity. In order to more objectively assess fungal virulence and host tree susceptibility in studies of host–pathogen interactions, a reliable, consistent, sensitive method is required to accurately identify and quantify MPB-associated fungal symbionts in planta. We have adapted RNase H2-dependent PCR, a technique originally designed for rare allele discrimination, to develop a novel RNase H2-dependent quantitative PCR (rh-qPCR) assay that shows greater specificity and sensitivity than previously published PCR-based methods to quantify MPB fungal symbionts in pine xylem and MPB whole beetles. Two sets of assay probes were designed: one that amplifies a broad range of ophiostomoid species, and a second that amplifies G. clavigera but not other MPB-associated ophiostomoid species. Using these primers to quantify G. clavigera in pine stems, we provide evidence that lesion length does not accurately reflect the extent of fungal colonization along the stem nor the quantity of fungal growth within this colonized portion of stem. The sensitivity, specificity, reproducibility, cost effectiveness and high-throughput potential of the rh-qPCR assay makes the technology suitable for identification and quantification of a wide array of pathogenic and beneficial microbes that form associations with plants and other organisms, even when the microbial partner is present in low abundance.

Description: Forest trees use various strategies to cope with drought stress and these strategies involve complex molecular mechanisms. Pinus halepensis Miller (Aleppo pine) is found throughout the Mediterranean basin and is one of the most drought-tolerant pine species. In order to decipher the molecular mechanisms that P. halepensis uses to withstand drought, we performed large-scale physiological and transcriptome analyses. We selected a mature tree from a semi-arid area with suboptimal growth conditions for clonal propagation through cuttings. We then used a high-throughput experimental system to continuously monitor whole-plant transpiration rates, stomatal conductance and the vapor pressure deficit. The transcriptomes of plants were examined at six physiological stages: pre-stomatal response, partial stomatal closure, minimum transpiration, post-irrigation, partial recovery and full recovery. At each stage, data from plants exposed to the drought treatment were compared with data collected from well-irrigated control plants. A drought-stressed P. halepensis transcriptome was created using paired-end RNA-seq. In total, ~6000 differentially expressed, non-redundant transcripts were identified between drought-treated and control trees. Cluster analysis has revealed stress-induced down-regulation of transcripts related to photosynthesis, reactive oxygen species (ROS)-scavenging through the ascorbic acid (AsA)-glutathione cycle, fatty acid and cell wall biosynthesis, stomatal activity, and the biosynthesis of flavonoids and terpenoids. Up-regulated processes included chlorophyll degradation, ROS-scavenging through AsA-independent thiol-mediated pathways, abscisic acid response and accumulation of heat shock proteins, thaumatin and exordium. Recovery from drought induced strong transcription of retrotransposons, especially the retrovirus-related transposon Tnt1 -94. The drought-related transcriptome illustrates this species’ dynamic response to drought and recovery and unravels novel mechanisms.

Description: Temperatures are expected to increase over the next century in all terrestrial biomes and particularly in boreal forests, where drought-induced mortality has been predicted to rise. Genomics research is helping to develop hypotheses regarding the molecular basis of drought tolerance and recent work proposed that the osmo-protecting dehydrin proteins have undergone a clade-specific expansion in the Pinaceae, a major group of conifer trees. The objectives of this study were to identify all of the putative members of the gene family, trace their evolutionary origin, examine their structural diversity and test for drought-responsive expression. We identified 41 complete dehydrin coding sequences in Picea glauca , which is four times more than most angiosperms studied to date, and more than in pines. Phylogenetic reconstructions indicated that the family has undergone an expansion in conifers, with parallel evolution implicating the sporadic resurgence of certain amino acid sequence motifs, and a major duplication giving rise to a clade specific to the Pinaceae. A variety of plant dehydrin structures were identified with variable numbers of the A-, E-, S- and K-segments and an N-terminal (N1) amino acid motif including assemblages specific to conifers. The expression of several of the spruce dehydrins was tissue preferential under non-stressful conditions or responded to water stress after 7–18 days without watering, reflecting changes in osmotic potential. We found that dehydrins with N1 K2 and N1 AESK2 sequences were the most responsive to the lack of water. Together, the family expansion, drought-responsive expression and structural diversification involving loss and gain of amino acid motifs suggests that subfunctionalization has driven the diversification seen among dehydrin gene duplicates. Our findings clearly indicate that dehydrins represent a large family of candidate genes for drought tolerance in spruces and in other Pinaceae that may underpin adaptability in spatially and temporally variable environments.

Description: Plant cell walls exhibit architectural and compositional changes throughout their development and in response to external cues. While tubulins are involved in cell wall biogenesis, much remains unknown about the scope of their involvement during the orchestration of this resource-demanding process. A transgenic approach coupled with cell wall compositional analysis, RNA-seq and mining of publicly available diurnal gene expression data was used to assess the involvement of tubulins in poplar leaf cell wall biogenesis. Leaf cell walls of transgenic poplar lines with constitutive overexpression of α-tubulin (TUA) exhibited an increased abundance of homogalacturonan, along with a reduction in xylose. These changes were traced to altered expression of UDP-glucuronic acid decarboxylase (GADC) in the transgenic leaves. A model is postulated by which altered diurnal control of TUA through its constitutive overexpression led to a metabolic tradeoff affecting cellular utilization of GADC substrate UDP-glucuronic acid. While there were no effects on cellulose, hemicellulose or lignin abundance, subtle effects on hemicellulose composition and associated gene expression were noted. In addition, expression and enzymatic activity of pectin methylesterase (PME) decreased in the transgenic leaves. The change is discussed in a context of increased levels of PME substrate homogalacturonan, slow stomatal kinetics and the fate of PME product methanol. Since stomatal opening and closing depend on fundamentally contrasting microtubule dynamics, the slowing of both processes in the transgenic lines as previously reported appears to be directly related to underlying cell wall compositional changes that were caused by tubulin manipulation.

Description: The development of heartwood (HW) and the associated accumulation of secondary metabolites, which are also known as ‘specialized metabolites’ or ‘extractives’, is an important feature of tree biology. Heartwood development can affect tree health with broader implications for forest health. Heartwood development also defines a variety of wood quality traits that are important in the forest industry such as durability and colour of wood products. In the bioproducts industry, HW provides a source of high-value small molecules such as fragrances and antimicrobials. The HW properties of decay resistance in living trees, durability and colour of wood products, and small molecule bioproducts are largely defined by secondary metabolites, the biosynthesis of which appears to be activated during the onset of HW formation. Traditionally, it is thought that HW formation involves a spike in the activity of secondary metabolism in parenchyma cells in a transition zone between sapwood and HW, followed by programmed cell-death. The resulting HW tissue is thought to consist entirely of dead cells. Here, we discuss a variation of existing models of HW formation, based on the recent discovery of HW-specific transcriptome signatures of terpenoid biosynthesis in sandalwood ( Santalum album L.) that invokes the activity of living cells in HW.

Description: Plants respond to pathogens through an orchestration of signaling events that coordinate modifications to transcriptional profiles and physiological processes. Resistance to necrotrophic pathogens often requires jasmonic acid, which antagonizes the salicylic acid dependent biotrophic defense response. Recently, myo -inositol has been shown to negatively impact salicylic acid (SA) levels and signaling, while galactinol enhances jasmonic acid (JA)-dependent induced systemic resistance to necrotrophic pathogens. To investigate the function of these compounds in biotrophic pathogen defense, we characterized the defense response of Populus alba × grandidentata overexpressing Arabidopsis GALACTINOL SYNTHASE3 (At GolS ) and Cucumber sativus RAFFINOSE SYNTHASE (Cs RFS ) challenged with Melampsora aecidiodes , a causative agent of poplar leaf rust disease. Relative to wild-type leaves, the overexpression of At GolS3 and Cs RFS increased accumulation of galactinol and raffinose and led to increased leaf rust infection. During the resistance response, inoculated wild-type leaves displayed reduced levels of galactinol and repressed transcript abundance of two endogenous GolS genes compared to un-inoculated wild-type leaves prior to the up-regulation of NON-EXPRESSOR OF PR1 and PATHOGENESIS-RELATED1 . Transcriptome analysis and qRT-PCR validation also revealed the repression of genes participating in calcium influx, phosphatidic acid biosynthesis and signaling, and salicylic acid signaling in the transgenic lines. In contrast, enhanced tolerance to H 2 O 2 and up-regulation of antioxidant biosynthesis genes were exhibited in the overexpression lines. Thus, we conclude that overexpression of At GolS and Cs RFS antagonizes the defense response to poplar leaf rust disease through repressing reactive oxygen species and attenuating calcium and phosphatidic acid signaling events that lead to SA defense.

Description: The tree bark periderm confers the first line of protection against pathogen invasion and abiotic stresses. The phellogen (cork cambium) externally produces cork (phellem) cells that are dead at maturity; while metabolically active, these tissues synthesize cell walls, as well as cell wall modifications, namely suberin and waxes. Suberin is a heteropolymer with aliphatic and aromatic domains, composed of acylglycerols, cross-linked polyphenolics and solvent-extractable waxes. Although suberin is essentially ubiquitous in vascular plants, the biochemical functions of many enzymes and the genetic regulation of its synthesis are poorly understood. We have studied suberin and wax composition in four developmental stages of hybrid poplar ( Populus tremula x Populus alba ) stem periderm. The amounts of extracellular ester-linked acyl lipids per unit area increased with tissue age, a trend not observed with waxes. We used RNA-Seq deep-sequencing technology to investigate the cork transcriptome at two developmental stages. The transcript analysis yielded 455 candidates for the biosynthesis and regulation of poplar suberin, including genes with proven functions in suberin metabolism, genes highlighted as candidates in other plant species and novel candidates. Among these, a gene encoding a putative lipase/acyltransferase of the GDSL-motif family emerged as a suberin polyester synthase candidate, and specific isoforms of peroxidase and laccase genes were preferentially expressed in cork, suggesting that their corresponding proteins may be involved in cross-linking aromatics to form lignin-like polyphenolics. Many transcriptional regulators with possible roles in meristem identity, cork differentiation and acyl-lipid metabolism were also identified. Our work provides the first large-scale transcriptomic dataset on the suberin-synthesizing tissue of poplar bark, contributing to our understanding of tree bark development at the molecular level. Based on these data, we have proposed a number of hypotheses that can be used in future research leading to novel biological insights into suberin biosynthesis and its physiological function.

Description: This paper examines contemporaneous and Granger causality among US corn futures and seven cash prices from major producing states for January 2006–March 2011. Causal flows from futures to cash prices are identified with contemporaneous and in-sample Granger causality tests but not with the out-of-sample Granger causality test. While no interstate in-sample or out-of-sample Granger causality is found, contemporaneous causal linkages are revealed. No causality from cash to futures prices is determined.