Linking Ecosystem Nitrogen Retention with Soil Microbial Community Structure

Understanding the mechanisms behind nitrogen loss in soil through leaching of inorganic nitrogen helps us beWer understand mechanisms for retenMon. Hypothesis: we should see different levels of soil inorganic nitrogen in various agricultural treatments, due to the effects these treatments have on soil microbial communities. Fungi use N less efficiently than bacteria. Fungal-dominated soils should have more inorganic N than bacterial-dominated soils

Natural Climate Solutions must embrace multiple perspectives to ensure synergy with sustainable development

To limit global warming to well below 2°C, immediate emissions reductions must be coupled with active removal of greenhouse gases from the atmosphere. “Natural Climate Solutions” (NCS) achieve atmospheric CO2 reduction through the conservation, restoration, or altered management of natural ecosystems, with enormous potential to deliver “win-win-win” outcomes for climate, nature and society. Yet the supply of high-quality NCS projects does not meet market demand, and projects already underway often fail to deliver their promised benefits, due to a complex set of interacting ecological, social, and financial constraints. How can these cross-sectoral challenges be surmounted? Here we draw from expert elicitation surveys and workshops with professionals across the ecological, sociological, and economic sciences, evaluating differing perspectives on NCS, and suggesting how these might be integrated to address urgent environmental challenges. We demonstrate that funders” perceptions of operational, political, and regulatory risk strongly shape the kinds of NCS projects that are implemented, and the locations where they occur. Because of this, greenhouse gas removal through NCS may fall far short of technical potential. Moreover, socioecological co-benefits of NCS are unlikely to be realized unless the local communities engaged with these projects are granted ownership over implementation and outcomes

White-tailed deer (Odocoileus virginianus) positively affect the growth of mature northern red oak (Quercus rubra) trees

Understanding and predicting the effects of deer (Cervidae) on forest ecosystems present significant challenges in ecosystem ecology. Deer herbivory can cause large changes in the biomass and species composition of forest understory plant communities, including early life-cycle trees (i.e., seedlings and saplings). Such changes can impact juvenile to adult transitions and the future age structure and species composition of mature forests. Changes to understory vegetation also impact flow of energy and nutrients in forest ecosystems. Studies examining the influence of deer on mature trees, however, are rare and rely on extrapolating effects from early life cycle stages of trees. We tested the hypothesis that the absence of deer would result in an increase in the growth rate of mature trees by examining the impact of white-tailed deer (Odocoileus virginianus) on mature canopy trees. We examined incremental growth in individuals of Quercus rubra, an important component of temperate deciduous forests in North America, inside and outside 16-year deer exclosures in eastern U.S. deciduous forests. We found that adult trees inside exclosures grew less than those directly exposed to deer. Our findings highlight the indirect effects of white-tailed deer on the growth of adult individuals of Q. rubra in a way opposite of what would be expected from previous studies based on immature or understory tree populations. We suggest the increased growth of adult trees in the presence of deer may be explained by increased nutrient inputs through deer fecal and urine deposits and the alteration of the competitive environment belowground through the reduction of understory vegetation by browsing. Underscoring the ecological and demographic importance of adult trees in forest ecosystems, results from this study suggest the direct and indirect effects of deer on mature trees should not be overlooked

Nutrient addition effects on tropical dry forests: a mini-review from microbial to ecosystem scales.

Humans have more than doubled inputs of reactive nitrogen globally and greatly accelerated the biogeochemical cycles of phosphorus and metals. However, the impacts of increased element mobility on tropical ecosystems remain poorly quantified, particularly for the vast tropical dry forest biome. Tropical dry forests are characterized by marked seasonality, relatively little precipitation, and high heterogeneity in plant functional diversity and soil chemistry. For these reasons, increased nutrient deposition may affect tropical dry forests differently than wet tropical or temperate forests. Here, we review studies that investigated how nutrient availability affects ecosystem and community processes from the microsite to ecosystem scales in tropical dry forests. The effects of N and P addition on ecosystem carbon cycling and plant and microbial dynamics depend on forest successional stage, soil parent material, and rainfall regime. Responses may depend on whether overall productivity is N- vs. P-limited, although data to test this hypothesis are limited. These results highlight the many important gaps in our understanding of tropical dry forest responses to global change. Large-scale experiments are required to resolve these uncertainties

Will seasonally dry tropical forests be sensitive or resistant to future changes in rainfall regimes?

Seasonally dry tropical forests (SDTF) are located in regions with alternating wet and dry seasons, with dry seasons that last several months or more. By the end of the 21st century, climate models predict substantial changes in rainfall regimes across these regions, but little is known about how individuals, species, and communities in SDTF will cope with the hotter, drier conditions predicted by climate models. In this review, we explore different rainfall scenarios that may result in ecological drought in SDTF through the lens of two alternative hypotheses: 1) these forests will be sensitive to drought because they are already limited by water and close to climatic thresholds, or 2) they will be resistant/resilient to intra- and inter-annual changes in rainfall because they are adapted to predictable, seasonal drought. In our review of literature that spans microbial to ecosystem processes, a majority of the available studies suggests that increasing frequency and intensity of droughts in SDTF will likely alter species distributions and ecosystem processes. Though we conclude that SDTF will be sensitive to altered rainfall regimes, many gaps in the literature remain. Future research should focus on geographically comparative studies and well-replicated drought experiments that can provide empirical evidence to improve simulation models used to forecast SDTF responses to future climate change at coarser spatial and temporal scales