Status and trends in Arctic vegetation: Evidence from experimental warming and long-term monitoring.

Changes in Arctic vegetation can have important implications for trophic interactions and ecosystem functioning leading to climate feedbacks. Plot-based vegetation surveys provide detailed insight into vegetation changes at sites around the Arctic and improve our ability to predict the impacts of environmental change on tundra ecosystems. Here, we review studies of changes in plant community composition and phenology from both long-term monitoring and warming experiments in Arctic environments. We find that Arctic plant communities and species are generally sensitive to warming, but trends over a period of time are heterogeneous and complex and do not always mirror expectations based on responses to experimental manipulations. Our findings highlight the need for more geographically widespread, integrated, and comprehensive monitoring efforts that can better resolve the interacting effects of warming and other local and regional ecological factors.

Arctic terrestrial biodiversity status and trends: A synopsis of science supporting the CBMP State of Arctic Terrestrial Biodiversity Report.

This review provides a synopsis of the main findings of individual papers in the special issue Terrestrial Biodiversity in a Rapidly Changing Arctic. The special issue was developed to inform the State of the Arctic Terrestrial Biodiversity Report developed by the Circumpolar Biodiversity Monitoring Program (CBMP) of the Conservation of Arctic Flora and Fauna (CAFF), Arctic Council working group. Salient points about the status and trends of Arctic biodiversity and biodiversity monitoring are organized by taxonomic groups: (1) vegetation, (2) invertebrates, (3) mammals, and (4) birds. This is followed by a discussion about commonalities across the collection of papers, for example, that heterogeneity was a predominant pattern of change particularly when assessing global trends for Arctic terrestrial biodiversity. Finally, the need for a comprehensive, integrated, ecosystem-based monitoring program, coupled with targeted research projects deciphering causal patterns, is discussed.

Dynamics of body protein and the implications for reproduction in captive muskoxen (Ovibos moschatus) during winter.

Muskoxen are considered to be obligate capital breeders because they rely exclusively on endogenous stores to reproduce. We studied 14 captive female muskoxen (not pregnant, n = 9; pregnant, n = 5) in February-June 2007 to assess changes in body composition and isotopic correlates of protein status (proportions of amino acid [p-AN] and urea N [p-UN] derived from body N). We measured body mass, body composition, and N metabolites in blood and urine between midgestation in February and early lactation (postcalving). All muskoxen lost body mass (-6% to -12%) and fat (-22% to -24%) over the winter, and pregnant muskoxen lost body protein (-6%) in late gestation. Nonpregnant animals maintained stores of body protein (+6%) in late winter. Losses of body protein in pregnant muskoxen (255 +/- 71.5 mg protein kg(-0.75) d(-1)) were similar to the amount of protein deposited in reproductive tissues (319 +/- 33.4). Plasma urea concentration increased (27-59 mg dL(-1)) with p-UN (0.13-0.33), which indicated oxidation of amino N during late winter. High estimates of p-AN (0.72 +/- 0.07) indicated that amino N from body protein was reutilized in late winter. Muskoxen conserve the capital of body protein stores for reproductive investment while using income of dietary protein for maintenance functions. We conclude that variation in protein supplies from body stores and the diet explain a large part of the variation in productivity of Arctic ungulates.