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

Abstract. Soil respiration (R_s) and its biophysical controls were measured over a fixed sand dune in a desert–shrub 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.