Treesearch

Forest harvesting can lead to mercury (Hg) mobilization from soils to aquatic habitats and promote the transformation of inorganic Hg to highly neurotoxic and bioaccumulative methyl-Hg (MeHg). Multiple past studies reveal broad variation of stream water MeHg and total Hg (THg) concentration responses to forest harvesting, which has confounded messaging to forest and resource managers. To advance beyond divergent and sometimes contradictory findings, we synthesized information for 23 previously studied catchments in North America and Fennoscandia and compiled a uniform set of soil, landscape...

In recent years, much attention has focused on strategies to reverse the decline of social capital in the United States. Increased social capital, which includes both intergroup contact and civic engagement, has many important benefits. For low-income individuals, friendships with high-income individuals (“economic connectedness”, a measure of inter-group contact) are one of the strongest predictors of their ability to escape poverty and gain increased life opportunities. Volunteering, a measure of civic engagement, is hypothesized to be key in building trust among neighbors. Urban parks...

Urban tree cover (UTC) is a commonly used metric in policy and management activities, including urban forest resources assessment, equity and distribution, and ecosystem services modelling. Despite the well-established benefits associated with urban tree canopy, declining tree cover has catalysed many cities into setting UTC targets. In this short communication, we used an assessment of UTC targets set by 57 cities worldwide to discuss the merits and drawbacks of setting UTC targets and to inform recommendations for setting effective UTC targets. We found that UTC targets range in ambition,...

Changing climates are creating more intense and frequent high-temperature events that could disrupt forest communities. In temperate forests, we have a relatively limited understanding of how trees are impacted by heat events, hindering our ability to predict the impacts of future heat waves. We conducted a community-level assessment of thermal safety margins in 11 hardwood tree species native to eastern North America. We used chlorophyll fluorescence to determine the critical heat tolerance of photosystem II (PSII) across 2 years in central Tennessee, USA. We focus on the temperature at...

Social equity, and the related topic of social vulnerability, is an important issue that is impacting many facets of society, including forests. A substantial portion, 39 %, of forests in the United States are owned by families, individuals, trusts, estates, and family partnerships, collectively referred to as family forest owners. There are many programs and services intended to help family forest owners conserve and better manage their land, but participation rates are relatively low, the efficacy of many programs has been called into question, and the social equitability of access is...

Ecological theory predicts that consumers should be co-limited by resource quantity and quality, given widespread consumer-resource nutritional imbalances. We used 25 estimates of annual community secondary production (ACSP) of stream macroinvertebrates to assess the relative roles of basal resource quantity (leaf litter standing stock [LLSS]) and quality (% nitrogen and % phosphorus of leaf litter) in modulating patterns of production in forest streams. We also tested the effects of hypothesized indirect drivers (stream discharge and inorganic nutrient concentrations) on basal resource...

Climate change is reducing snowpack across temperate regions with negative consequences for human and natural systems. Because forest canopies create microclimates that preserve snowpack, managing forests to support snow refugia—defined here as areas that remain relatively buffered from contemporary climate change over time that sustain snow quality, quantity, and/or timing appropriate to the landscape—could reduce climate change impacts on snow cover, sustaining the benefits of snow. We review the current understanding of how forest canopies affect snow, finding that while closed-conifer...

Tree regeneration in northern temperate and southern boreal forests is threatened by multiple factors, including over-browsing by ungulates such as white-tailed deer (Odocoileus virginiana). However, characterizing the effects of deer browse on tree regeneration at regional scales has been challenging due to (a) the lack of reliable indicators of browsing intensity and (b) the fact that browsing impacts are likely to vary by seedling size yet coarse metrics are often used to capture this seedling attribute. To address these challenges, we modeled effects of white-tailed deer browse and...

Forest drought monitoring tools are crucial for managing tree water stress and enhancing ecosystem resilience. The Forest Drought Response Index (ForDRI) was developed to monitor drought conditions in forested areas across the contiguous United States (CONUS), integrating vegetation health, climate data, groundwater, and soil moisture content. This study evaluated ForDRI using Pearson correlations with the Bowen Ratio (BR) at 24 Ameri- Flux sites and Spearman correlations with the Tree-Ring Growth Index (TRSGI) at 135 sites, along with feedback from 58 stakeholders. CONUS was divided into...

Rapid ‘ōhiʻa death (ROD), caused by fungal pathogens Ceratocystis lukuohia and Ceratocystis huliohia, is devastating ʻōhiʻa (Metrosideros polymorpha), the keystone forest tree species of Hawaiʻi. Ceratocystidaceae fungi produce fruity volatile organic compounds (VOCs) and sticky sexual spores, suggesting they are adapted for insect dispersal. In this study, we explored chemical signaling of the causal agents of the ROD disease complex and how those VOCs mediate ambrosia beetle (Coleoptera: Curculiondiae: Scolytidae)-plant interactions. Four species of ambrosia beetles (Xyleborinus saxesenii...