Microtopographic variation in soil respiration and its controlling factors vary with plant phenophases in a desert-shrub ecosystem

Soil respiration (R-s) and its biophysical controls were measured over a fixed sand dune in a desertshrub ecosystem in northwest China in 2012 to explore the mechanisms controlling the spatial heterogeneity in R-s and to understand the plant effects on the spatial variation in R-s in different phenophases. The measurements were carried out on four slope orientations (i. e., windward, leeward, north-and south-facing) and three height positions on each slope (i. e., lower, upper, and top) across the phenophases of the dominant shrub species (Artemisia ordosica). Coefficient of variation (i. e., standard deviation/mean) of R-s across the 11 microsites over our measurement period was 23.5 %. Soil respiration was highest on the leeward slope, and lowest on the windward slope. Over the measurement period, plant-related factors, rather than microhydrometeorological factors, affected the microtopographic variation in R-s. During the flower-bearing phase, root biomass affected R-s most, explaining 72% of the total variation. During the leaf coloration-defoliation phase, soil nitrogen content affected R-s the most, explaining 56% of the total variation. Our findings highlight that spatial pattern in R-s was dependent on plant distribution over a desert sand dune, and plant-related factors largely regulated topographic variation in R-s, and such regulations varied with plant phenology.