Publications

Biological nitrogen fixation represents the largest natural flux of new nitrogen (N) into terrestrial ecosystems, providing a critical N source to support net primary productivity of both natural and agricultural systems. When they are common, symbiotic associations between plants and bacteria can add more than 100 kg N ha−1 y−1 to ecosystems. Yet, these associations are uncommon in many terrestri

Adjustments or complete withdrawal of livestock grazing are among the most common conservation actions in semiarid uplands, but outcomes can vary considerably with ecological context. Invasion by exotic annual grasses and the excessive wildfire they promote are increasing threats to semiarid shrub-steppe, and plant-community response to livestock exclusion in these areas may be complicated by the

Plant-population recovery across large disturbance areas is often seed-limited. An understanding of seed dispersal patterns is fundamental for determining natural-regeneration potential. However, forecasting seed dispersal rates across heterogeneous landscapes remains a challenge. Our objectives were to determine (i) the landscape patterning of post-disturbance seed dispersal, and underlying sourc

Background: Model simulations of wildfire spread and assessments of their accuracy are needed for understanding and managing altered fire regimes in semiarid regions. The accuracy of wildfire spread simulations can be evaluated from post hoc comparisons of simulated and actual wildfire perimeters, but this requires information on pre-fire vegetation fuels that is typically not available. We assess

Annual-grass invasions are transforming desert ecosystems in ways that affect ecosystem carbon (C) balance, but previous studies do not agree on the pattern, magnitude and direction of changes. A recent meta-analysis of 41 articles and 386 sites concludes that invasion by annual grasses such as cheatgrass (Bromus tectorum L) reduces C in biomass across the Great Basin (Nagy et al., 2021). Reanalys

Rockland habitat in South Florida, USA, is a threatened ecosystem that has been lost, fragmented, or degraded because of urbanization or other anthropogenic disturbance. Furthermore, low-lying islands and coastal areas are experiencing sea level rise (SLR) and an increased frequency and intensity of tidal flooding, putting rockland habitats there at increasing risk of ecological change. We evaluat

This report summarizes data-collection activities associated with the U.S. Geological Survey Humboldt Bay Water-Quality and Salt Marsh Monitoring Project. This work was undertaken to gain a comprehensive understanding of water-quality conditions, salt marsh accretion processes, marsh-edge erosion, and soil-carbon storage in Humboldt Bay, California. Multiparameter sondes recorded water temperature

Resource managers seek to thin second-growth riparian forests to address multiple stream and riparian management objectives, including enhancing aquatic productivity via light-mediated trophic pathways in watersheds of the Pacific Northwest (USA). However, such increases in aquatic productivity depend on complex food web dynamics that link riparian forests and streams. To evaluate how riparian for

Understanding the effects of extreme weather on animal populations is fundamental to ecological and conservation sciences and species management. Climate change has resulted in both warm and cold temperature extremes, including an increased frequency of severe cold snaps at middle latitudes in North America. These unusually cold air masses cause rapid declines in nearshore ocean temperatures in co

We surveyed for coastal Cactus Wren (Campylorhynchus brunneicapillus) in 378 established plots in southern San Diego County in 2021, encompassing 3 genetic clusters (Otay, Lake Jennings, and Sweetwater/Encanto). Two surveys were completed at each plot between March 1 and July 31. Cactus Wrens were detected in 130 plots (34 percent of plots), remaining virtually the same as the percentage of plots

Coastal wetlands are key features of the Earth’s surface and are characterized by a diverse array of coupled geomorphological and biological processes. However, the links between the distribution of biodiversity (e.g., species and structural diversity) and the formation of coastal geomorphology are not well understood on a landscape scale most useful to coastal zone managers. This study describes

Coastal wetlands provide numerous ecosystem services; yet these ecosystems are increasingly vulnerable to climate change stressors, especially excessive flooding from sea-level rise and storm events. This study highlights the important contribution of vegetation belowground biomass to marsh stability and identifies loss of vegetation as a critical driver of marsh collapse. We investigated the shea