Grazing Management Effect on Micro- and Macro- Scale Fate of Carbon and Nitrogen in Rangelands.

Fundamental information of how grazing of rangeland ecosystems can modify nutrient cycling, carbon (C) sequestration and mitigation of greenhouse gases (GHG) at the pasture (macro-scale) level is still scarce given the complexity of the controlling processes at macro- and micro-scales (plant/dung pat level). This project proposes a multidisciplinary research approach to evaluate physical and biological processes affecting the transport, transformation, losses and storage of nitrogen (N) and C pulses induced by grazing. We propose to: a) quantify the size of nutrient pulses across grazing strategies; b) determine the patterns of nutrient return in pastures in relation to grazing strategies; c) assess the decomposition rate and nutrient fate from dung through the transport and transformations of N and C into soil and atmosphere with and without dung beetle colonization and across water availability scenarios, d) develop relationships of stocking density, spatial/temporal nutrient return, dung beetle abundance, and micro-scale nutrient fate to improve pasture level estimations of existing process-based biogeochemical models on nutrient cycling, C sequestration and GHG mitigation in rangelands. Non-traditional research approaches – integrating landscape temporal and spatial patterns of nutrient return as imposed by grazing strategies, micro-scale nutrient decomposition/utilization processes, and biological and climate interactions, are needed to take a full-accounting approach to improve understanding of resource conservation and improved nutrient use efficiency in rangelands. How the collaboration works and the results so far obtained for this project will be presented at the meeting.