Ecological disturbances can significantly affect biogeochemical cycles in terrestrial ecosystems, but the biogeochemical consequences of the extensive mountain pine beetle outbreak in high elevation whitebark pine (WbP) (Pinus albicaulis) ecosystems of western North America have not been previously investigated. Mountain pine beetle attack has driven widespread WbP mortality, which could drive shifts in both the pools and fluxes of nitrogen (N) within these ecosystems. Because N availability can limit forest regrowth, understanding how beetle-induced mortality affects N cycling in WbP stands may be critical to understanding the trajectory of ecosystem recovery. Thus, we measured above- and belowground N pools and fluxes for trees representing three different times since beetle attack, including unattacked trees. Litterfall N inputs were more than ten times higher under recently attacked trees compared to unattacked trees. Soil inorganic N concentrations also increased following beetle attack, potentially driven by a more than two-fold increase in ammonium (NH4 +) concentrations in the surface soil organic horizon. However, there were no significant differences in mineral soil inorganic N or soil microbial biomass N concentrations between attacked and unattacked trees, implying that short-term changes in N cycling in response to the initial stages of WbP attack were restricted to the organic horizon. Our results suggest that while mountain pine beetle attack drives a pulse of N from the canopy to the forest floor, changes in litterfall quality and quantity do not have profound effects on soil biogeochemical cycling, at least in the short-term. However, continuous observation of these important ecosystems will be crucial to determining the long-term biogeochemical effects of mountain pine beetle outbreaks.

Whitebark pine (Pinus albicaulis Engelm.), an ecologically important tree species in high-elevation ecosystems of western North America, is threatened by white pine blister rust (Cronartium ribicola Fischer) and increased pressure from mountain pine beetle (Dendroctonus ponderosae Hopkins) due to climate warming. In addition, there is concern that fire suppression may be leading to successional replacement of whitebark by late-seral trees. Despite widespread knowledge that the tree is in decline, there is limited understanding of its successional dynamics, particularly in forests disturbed by white pine blister rust and mountain pine beetle. Our objective was to examine how disturbances have affected forest composition, structure, and seedling regeneration over a 22-year period (1990-2012) at 19 sites in the Cascade Mountains of Washington State (USA). Over that time, 13 sites (68%) were infected by white pine blister rust, 11 (58%) were disturbed by mountain pine beetle, and 5 (26%) experienced wildfire. Tree community composition changed significantly during the study period, primarily due to significant mortality of mature (≥20-cm diameter at breast height) whitebark pine. Despite loss of mature whitebark trees, we found little evidence of successional replacement by other tree species. Whitebark seedling density was unrelated to basal area of mature whitebark pine, but positively correlated with the presence of herb and shrub cover. Our results demonstrate the value of long-term repeated measurements for elucidating successional dynamics.

Abstract. Although the broad field of ecology and its role in understanding the distribution and diversity of life on earth is a central part of the natural sciences, there is currently no comprehensive ranking of academic institutions for this discipline, which has quadrupled in research volume and visibility over the past three decades. We assessed scholarly productivity in the field of ecology for 316 North American academic institutions between the years 2000 and 2014. We present institutional rankings of productivity in terms of number of publications, number of citations, and Hirsch's h index, a measure that integrates productivity and impact. For the top-ranked institutions, we also calculated h m , an h-based metric used to compare productivity across institutions of different sizes. In addition, we analyzed the effect of institution size on h index, publication rate, and number of citations. We found that scholarship in ecology is not significantly different between public and private universities, and from institutions ranging in size from extremely large to relatively small. Many of the institutions in the "ecology top 20" are widely considered as being among North America's elite schools. However, there are several smaller institutions that have very high research productivity and impact in ecology with an apparently very strong ecology faculty. Administrators, faculty, prospective faculty, and students use institutional rankings, along with other data, to make decisions about programs in which to invest or participate. Relative institutional strength in the field of ecology, however, has not been previously measured, perhaps because faculty with expertise in ecology are often dispersed through multiple academic units of a university. Thus, our findings fill an important gap for ecology as a discipline.