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Summary: Stomatal closure during drought inhibits carbon uptake and may reduce a tree's defensive capacity. Limited carbon availability during drought may increase a tree's mortality risk, particularly if drought constrains trees' capacity to rapidly produce defenses during biotic attack.We parameterized a new model of conifer defense using physiological data on carbon reserves and chemical defenses before and after a simulated bark beetle attack in mature Pinus edulis under experimental drought. Attack was simulated using inoculations with a consistent bluestain fungus (Ophiostoma sp.) of Ips confusus, the main bark beetle colonizing this tree, to induce a defensive response.Trees with more carbon reserves produced more defenses but measured phloem carbon reserves only accounted for c. 23% of the induced defensive response. Our model predicted universal mortality if local reserves alone supported defense production, suggesting substantial remobilization and transport of stored resin or carbon reserves to the inoculation site.Our results show that de novo terpene synthesis represents only a fraction of the total measured phloem terpenes in P. edulis following fungal inoculation. Without direct attribution of phloem terpene concentrations to available carbon, many studies may be overestimating the scale and importance of de novo terpene synthesis in a tree's induced defense response. [ABSTRACT FROM AUTHOR]

Summary: Shifts in the age or turnover time of non‐structural carbohydrates (NSC) may underlie changes in tree growth under long‐term increases in drought stress associated with climate change. But NSC responses to drought are challenging to quantify, due in part to large NSC stores in trees and subsequently long response times of NSC to climate variation.We measured NSC age (Δ14C) along with a suite of ecophysiological metrics in Pinus edulis trees experiencing either extreme short‐term drought (−90% ambient precipitation plot, 2020–2021) or a decade of severe drought (−45% plot, 2010–2021). We tested the hypothesis that carbon starvation – consumption exceeding synthesis and storage – increases the age of sapwood NSC.One year of extreme drought had no impact on NSC pool size or age, despite significant reductions in predawn water potential, photosynthetic rates/capacity, and twig and needle growth. By contrast, long‐term drought halved the age of the sapwood NSC pool, coupled with reductions in sapwood starch concentrations (−75%), basal area increment (−39%), and bole respiration rates (−28%).Our results suggest carbon starvation takes time, as tree carbon reserves appear resilient to extreme disturbance in the short term. However, after a decade of drought, trees apparently consumed old stored NSC to support metabolism. [ABSTRACT FROM AUTHOR]

Pinus edulis Engelm. is a short-stature, drought-tolerant tree species that is abundant in piñon-juniper woodlands throughout semiarid ecosystems of the American Southwest. P. edulis is a model species among ecophysiological disciplines, with considerable research focus given to hydraulic functioning and carbon partitioning relating to mechanisms of tree mortality. Many ecological studies require robust estimates of tree structural traits such as biomass, active sapwood area, and leaf area. We harvested twenty trees from Central New Mexico ranging in size from 1.3 to 22.7 cm root crown diameter (RCD) to derive allometric relationships from measurements of RCD, maximum height, canopy area (CA), aboveground biomass (AGB), sapwood area (AS), and leaf area (AL). Total foliar mass was measured from a subset of individuals and scaled to AL from estimates of leaf mass per area. We report a strong nonlinear relationship to AGB as a function of both RCD and height, whereas CA scaled linearly. Total AS expressed a power relationship with RCD. Both AS and CA exhibited strong linear relationships with AL (R2 = 0.99), whereas RCD increased nonlinearly with AL. We improve on current models by expanding the size range of sampled trees and supplement the existing literature for this species. Study Implications: Land managers need to better understand carbon and water dynamics in changing ecosystems to understand how those ecosystems can be sustainably used now and in the future. This study of two-needle pinon (Pinus edulis Engelm.) trees in New Mexico, USA, uses observations from unoccupied aerial vehicles, field measurements, and harvesting followed by laboratory analysis to develop allometric models for this widespread species. These models can be used to understand plant traits such biomass partitioning and sap flow, which in turn will help scientists and land managers better understand the ecosystem services provided by pinon pine across North America. [ABSTRACT FROM AUTHOR]

Increased drought frequency and severity are a pervasive global threat, yet the capacity of mesic temperate forests to maintain resilience in response to drought remains poorly understood. We deployed a throughfall removal experiment to simulate a once in a century drought in New Hampshire, USA, which coupled with the region-wide 2016 drought, intensified moisture stress beyond that experienced in the lifetimes of our study trees. To assess the sensitivity and threshold dynamics of two dominant northeastern tree genera (Quercus and Pinus), we monitored sap flux density (J s), leaf water potential and gas exchange, growth and intrinsic water-use efficiency (iWUE) for one pretreatment year (2015) and two treatment years (2016–17). Results showed that J s in pine (Pinus strobus L.) declined abruptly at a soil moisture threshold of 0.15 m3 m−3, whereas oak's (Quercus rubra L. and Quercus velutina Lam.) threshold was 0.11 m3 m−3—a finding consistent with pine's more isohydric strategy. Nevertheless, once oaks' moisture threshold was surpassed, J s declined abruptly, suggesting that while oaks are well adapted to moderate drought, they are highly susceptible to extreme drought. The radial growth reduction in response to the 2016 drought was more than twice as great for pine as for oaks (50 vs 18%, respectively). Despite relatively high precipitation in 2017, the oaks' growth continued to decline (low recovery), whereas pine showed neutral (treatment) or improved (control) growth. The iWUE increased in 2016 for both treatment and control pines, but only in treatment oaks. Notably, pines exhibited a significant linear relationship between iWUE and precipitation across years, whereas the oaks only showed a response during the driest conditions, further underscoring the different sensitivity thresholds for these species. Our results provide new insights into how interactions between temperate forest tree species' contrasting physiologies and soil moisture thresholds influence their responses and resilience to extreme drought. [ABSTRACT FROM AUTHOR]

Climate‐driven woody vegetation mortality is a defining feature of semiarid biomes that drives fundamental changes in ecosystem structure. However, the observed impacts of woody mortality on ecosystem‐scale energy and water budgets and the responses of surviving vegetation are highly variable among studies in water‐limited environments. A previous girdling manipulation experiment in a piñon‐juniper woodland suggested that although ecosystem‐scale evapotranspiration was not altered by large‐scale piñon mortality, soil water content decreased and the surviving juniper experienced greater water stress than juniper in an undisturbed woodland. Here we experimentally explored to what extent mortality‐induced changes in energy balance components can explain these results. We compared energy fluxes measured above two adjacent piñon‐juniper woodlands where piñon girdling was implemented at one site and the other subsequently experienced large‐scale natural piñon mortality. We found that the mortality‐induced decrease in canopy area was not sufficient to alter surface reflectance, roughness, and partitioning between energy budget components at both sites. A radiative transfer model estimated that because of the sparse premortality canopy, surface reflectance is more sensitive to a large increase in understory leaf area than further loss of crown area. Increased water stress in the remaining juniper following both mortality events can be explained by an increase in radiation on the ground that promoted higher soil temperature and evaporation. We found similar responses of ecosystem and tree‐level functions to both girdling and natural mortality. This suggests that girdling is an appropriate approach to explore the impact of tree mortality on ecosystem structure, function, and energy balance. Key Points: Piñon mortality in piñon‐juniper woodlands did not alter surface reflectance and roughness that can largely impact energy and water budgetsEnhanced incoming radiation on the ground following mortality increased soil evaporation and water stress in surviving juniperResponses of ecosystem function and surviving juniper to piñon mortality were similar between the girdling‐induced and natural mortality [ABSTRACT FROM AUTHOR]

Across the semiarid ecosystems of the southwestern USA, there has been widespread encroachment of woody shrubs and trees including Juniperus species into former grasslands. Quantifying vegetation biomass in such ecosystems is important because semiarid ecosystems are thought to play an important role in the global land carbon (C) sink, and changes in plant biomass also have implications for primary consumers and potential bioenergy feedstock. Oneseed juniper (Juniperus monosperma) is common in desert grasslands and pinyon–juniper rangelands across the intermountain region of southwestern North America; however, there is limited information about the aboveground biomass (AGB) and sapwood area (SWA) for this species, causing uncertainties in estimates of C stock and transpiration fluxes. In this study, we report on canopy area (CA), stem diameter, maximum height, and biomass measurements from J. monosperma trees sampled from central New Mexico. Dry biomass ranged between 0.4 kg and 625 kg, and cross-sectional SWA was measured on n = 200 stems using image analysis. We found a strong linear relationship between CA and AGB (r2 = 0.96), with a similar slope to that observed in other juniper species, suggesting that this readily measured attribute is well suited for upscaling studies. There was a 9% bias between different approaches to measuring CA, indicating care should be taken to account for these differences to avoid systematic biases. We found equivalent stem diameter (ESD) was a strong predictor of biomass, but that existing allometric models underpredicted biomass in larger trees. We found SWA could be predicted from individual stem diameter with a power relationship, and that tree-level SWA should be estimated by summing the SWA predictions from individual stems rather than ESD. Our improved allometric models for J. monosperma support more accurate and robust measurements of C storage and transpiration fluxes in Juniperus -dominated ecosystems. [ABSTRACT FROM AUTHOR]

We review existing challenges and possible solutions for increasing small-scale sustainable beef production in New England. Beef production policies are most effectively implemented when the impacts of regulation, facility accessibility, and seasonality are considered. Limitations surrounding scheduling availability, skill, and services offered create challenges that reduce processing facility accessibility for small-scale producers. Relationship building facilitates trust and communication between all members of the beef value chain. Voluntary certifications offer value translation and financial networks for beef producers. State inspection and slaughter/processing programs provide scale-appropriate policy solutions for sustainable beef in New England. [ABSTRACT FROM AUTHOR]

White Pine Needle Damage (WPND) is a complex of foliar fungal pathogens that have established as a chronic disease impacting eastern white pine ( Pinus strobus L.) stands in the northeastern United States. With long-term ecological and economic impacts in mind, it is critical to quantify the negative effects of this disease on tree and forest health in order to make informed management decisions. We measured litterfall to determine the timing and magnitude of WPND-induced defoliation across four study sites in the northeastern US between 2014–2016. We measured N concentrations of needles cast throughout the 2014 growing season to estimate total litter N flux resulting from WPND. Additionally, to quantify growth declines we measured annual basal area increment (BAI) from six symptomatic study sites in the infected region. We found that WPND-induced defoliation in the months of June and July accounted for 47% of the total annual litterfall across the study sites, often exceeding normal needle senescence in October. Foliar %N in June and July was 0.78 and 0.84% respectively, significantly higher than October concentrations of 0.40%, suggesting incomplete resorption of N during the summer months. Untimely summer defoliations resulted in a mean estimated N loss of 0.92 g N m −2  yr −1 , representing 63% of the total growing season N input from foliage. Growth of symptomatic trees at all sites was reduced following outbreaks of WPND initiating between 2007–2009. Severely infected trees reduced BAI 25–73% compared to pre-outbreak years. Our results show that WPND-induced defoliation significantly alters litterfall and N dynamics of affected stands, and suggest that subsequent N limitation in addition to reduced foliar area greatly reduces annual wood growth within infected stands. [ABSTRACT FROM AUTHOR]

Eastern white pine ( Pinus strobus L.) is one of the most important conifer species across eastern North America. However, emerging health issues of eastern white pine have increased dramatically in recent decades, raising serious concerns over the health and future of this species. These emerging issues are due to native pests and pathogens that were mostly innocuous in the past and hence, have been rarely studied. One fungal pathogen of concern, Caliciopsis pinea Peck, is associated with severe resinosis, crown thinning, dieback, cankers, and bark cracks/fissures. Reports of C. pinea have been on the rise since the mid-1990s, particularly in the northeastern U.S. An insect of concern, eastern white pine bast scale ( Matsucoccus macrocicatrices Richards), is a sap-sucking pest associated with branch flagging, dieback, and canker formation. Although described as early as 1958, this insect was not reported in the southeastern U.S. until 2006, when it was found on eastern white pine with dieback symptoms. A foliar complex of fungal pathogens has also been on the rise since 2006 in the northeastern U.S. and southern Canada, known collectively as White Pine Needle Damage. This complex results in needle discoloration and necrosis, premature needle drop, and branch dieback. In combination, these emerging health issues are occurring at levels not previously reported and across several regions, indicating an imminent range-wide health concern for eastern white pine. Our goal is to synthesize the ecology, evolutionary and post-settlement history, silvicultural practices, and abiotic and biotic stressors of eastern white pine. By unifying the known ecology and stressors of eastern white pine, we aim to provide a forest health framework to assist resource managers in developing a cohesive conservation, management, and restoration plan for this critical conifer species in North America. [ABSTRACT FROM AUTHOR]

The foliar fungal pathogens associated with the disease complex known as White Pine Needle Damage (WPND) are causing widespread defoliation of eastern white pine ( Pinus strobus L.) in the northeastern United States and Canada. Presently, there are no specific management recommendations for addressing declining stand health relating to WPND induced defoliations. This study aims to test the effects of thinning at two different residual stocking densities (14 and 25 m 2  ha −1 ) on mitigating the negative impacts of WPND within infected stands. To quantify the impacts of WPND on individual tree health, we generated a composite health index score using response variables measured in the field and weighted according to their association with observations of WPND severity. Post-thinning changes in disease severity were used to evaluate the effectiveness of stand thinning to reduce pathogen pressure and promote overall tree vigor. Results show that thinning had a rapid positive effect on overall tree health, with no significant difference between thinning treatment levels in the first two years following tree removal. Severity of WPND was reduced by 35% in low-density residual thinnings in the second year of the study. Our findings suggest that thinning as a silvicultural tool to reduce stocking densities within infected stands can effectively promote overall tree health and maintaining proper stocking densities is recommended for stands at risk of infection. [ABSTRACT FROM AUTHOR]