Date of Award

4-14-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Abstract

Boreal forests support a variety of animals distributed across a matrix of habitat patches including forests of different ages and stand densities. These forests occur at high latitudes where cold and moist conditions favor ground layer dominance by mosses and slow decomposition rates, resulting in a thick soil organic layer (SOL) comprised primarily of decomposing mosses and roots. However, limited information is available on how animal use varies across habitat types in northeastern Siberia. Boreal forests of this region are unique because they are comprised of a single deciduous conifer, Cajander larch (Larix cajanderi). These forests also occur on a region of permafrost known as Yedoma, which is both ice and carbon rich. The SOL plays a critical role in plant-soil feedbacks because it insulates and protects underlying permafrost soils and creates a barrier to seed germination. In this thesis I take two approaches to understand how animals use varies between different forest stands, and how animal disturbances influence ecological processes. In the first chapter, I assess animal use along two gradients (successional stage and larch stand density). In the second chapter, I examine the effect of animal disturbances to soil characteristics in an altitudinal boreal treeline region. Data was collected in summers 2013 and 2014 near the Northeast Science Station in Cherskii, Sakha Republic, Russia. Results from the first chapter suggest larch stand density may have strong influences on animal use within larch forests of northeastern Siberia. Understanding specific traits within different stand densities which promote habitat use will be important for predicting animal responses to potential stand shifts. The results from the second chapter suggest that animal disturbances alter soil substrate characteristics by decreasing SOL depth, leading to warmer surface soils and deeper thaw depths. These changes may provide a deeper rooting volume and facilitate colonization and growth of vascular plants, especially shrubs. Because of known differences in the ecological role of mosses compared to shrubs with regard to carbon and energy balance, understanding mechanisms by which animal disturbances alter soil characteristics, and in turn vegetation dominance, is important for predicting future soil-vegetation feedbacks in a warming climate.

Granting Institution

University of Texas Brownsville

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