Clinal variations in seedling traits and responses to water availability correspond to seed-source environmental gradients in a foundational dryland tree species.

Background And Aims: In dryland ecosystems, conifer species are threatened by more frequent and severe droughts, which can push species beyond their physiological limits. Adequate seedling establishment will be critical for future resilience to global change. We used a common garden glasshouse experiment to determine how seedling functional trait expression and plasticity varied among seed sources in response to a gradient of water availability, focusing on a foundational dryland tree species of the western USA, Pinus monophylla.

Evidence of widespread topoclimatic limitation for lower treelines of the Intermountain West, United States.

Many forests in dry mountain regions are characterized by a lower elevational treeline. Understanding the controls on the position of lower treeline is important for predicting future forest distributional shifts in response to global environmental change. Lower treelines currently at their climate limit are expected to be more sensitive to changing climate, whereas lower treelines constrained by non-climatic factors are less likely to respond directly to climate change but may be sensitive to other global change agents.

Shrub facilitation of tree establishment varies with ontogenetic stage across environmental gradients.

Plant-plant interactions are important drivers of ecosystem structure and function, yet predicting interaction outcomes across environmental gradients remains challenging. Understanding how interactions are affected by ontogenetic shifts in plant characteristics can provide insight into the drivers of interactions and improve our ability to anticipate ecosystem responses to environmental change. We developed a conceptual framework of nurse shrub facilitation of tree establishment.

Assessment of the Suitability of Tree Rings as Archives of Global and Regional Atmospheric Mercury Pollution.

This study investigated the methodology and utility of dendrochemistry in the assessment of spatial and temporal concentrations of gaseous elemental mercury. Tree cores from the Pinus species in California and Nevada, U.S.

Fine-scale stand structure mediates drought-induced tree mortality in pinyon-juniper woodlands.

Severe drought has resulted in widespread tree die-off events in forests and woodlands globally and is forecast to become more frequent in coming decades. Tree mortality is a complex process influenced by climate, soils, characteristics of individual trees, interactions between trees, and the dynamics of pests and pathogens. The role of stand structure and stand density in mediating the resistance of trees to drought remains poorly understood, especially in semiarid woodlands, which are expected to be highly susceptible to future severe drought.

The Value of Native Plants and Local Production in an Era of Global Agriculture.

For addressing potential food shortages, a fundamental tradeoff exists between investing more resources to increasing productivity of existing crops, as opposed to increasing crop diversity by incorporating more species. We explore ways to use local plants as food resources and the potential to promote food diversity and agricultural resilience. We discuss how use of local plants and the practice of local agriculture can contribute to ongoing adaptability in times of global change.

Evidence for Nonstomatal Uptake of Hg by Aspen and Translocation of Hg from Foliage to Tree Rings in Austrian Pine.

To determine whether trees are reliable biomonitors of air mercury (Hg) pollution concentrations were measured in bark, foliage, and tree rings. Data were developed using 4-year old Pinus and Populus trees grown from common genetic stock in Oregon and subsequently transferred to four air treatments differing in gaseous oxidized mercury (GOM) chemistry and total gaseous Hg (TGM) concentrations. Soil of a subset of trees was spiked with HgBr in solution to test for root uptake.

Spatio-temporal analysis of remotely-sensed forest mortality associated with road de-icing salts.

Forest mortality along highways has long been a concern in areas where de-icing compounds are applied during winter. This study combined the spatial advantage of high-resolution remote sensing imagery and the temporal advantage of long-term archival imagery to quantify forest mortality and to detect the subtle and chronic effects of road de-icing salts for a large mountain watershed in the Sierra Nevada Mountains, USA. IKONOS-derived mortality was used in a fine-scale spatial analysis to assess road proximity and roadside topography effects on forest mortality and to compare two potential mechanisms of de-icing salt damage, i.

Carbon dynamics in the future forest: the importance of long-term successional legacy and climate-fire interactions.

Understanding how climate change may influence forest carbon (C) budgets requires knowledge of forest growth relationships with regional climate, long-term forest succession, and past and future disturbances, such as wildfires and timber harvesting events. We used a landscape-scale model of forest succession, wildfire, and C dynamics (LANDIS-II) to evaluate the effects of a changing climate (A2 and B1 IPCC emissions; Geophysical Fluid Dynamics Laboratory General Circulation Models) on total forest C, tree species composition, and wildfire dynamics in the Lake Tahoe Basin, California, and Nevada. The independent effects of temperature and precipitation were assessed within and among climate models.

Application of a rule-based model to estimate mercury exchange for three background biomes in the continental United States.

Ecosystems that have low mercury (Hg) concentrations (i.e., not enriched or impacted by geologic or anthropogenic processes) cover most of the terrestrial surface area of the earth yet their role as a net source or sink for atmospheric Hg is uncertain.

Tree diseases and landscape processes: the challenge of landscape pathology.

Forest pathology inherently involves a landscape perspective, because tree pathogens propagate according to heterogeneous spatial patterns of flow and isolation. Landscape pathology is a field that is now emerging from the transdisciplinary cooperation of forest pathologists with landscape ecologists. Here, we review recent broad-scale assessments of tree disease risk, investigations of site and host preferences for several root rot pathogens, and regional historical analyses of pathogen outbreak in plantations.

Model-based assessment of aspen responses to elk herbivory in Rocky Mountain National Park, USA.

In Rocky Mountain National Park (RMNP), aspen (Populus tremuloides Michx.) has been observed to be declining on elk (Cervus elaphus nelsoni) winter range for many decades. To support elk management decisions, the SAVANNA ecosystem model was adapted to explore interactions between elk herbivory and aspen dynamics.

An ecosystem approach to population management of ungulates.

Harvest objectives for wild ungulates have traditionally been based on population models that do not consider ecosystem effects of ungulate herbivory, nor interactions between native and domestic ungulate species. There is a need for ecosystem models to allow wildlife managers to evaluate potential ecosystem effects of management scenarios. The utility of the SAVANNA simulation model for estimating elk population objectives within an ecosystem context was demonstrated for North Park, Colorado, USA.