The effect of soil depth on temperature sensitivity of extracellular enzyme activity decreased with elevation: Evidence from mountain grassland belts.

Temperature sensitivity of soil extracellular enzyme activity (EEA), indicated by the temperature coefficient Q, is used to predict the effect of temperature on soil carbon (C), nitrogen (N), and phosphorus (P) cycling. At present, we lack understanding of elevation and soil depth variations in Q of EEA. Here, we measured the Q of three enzymes participating in C- (β-1,4-glucosidase, BG), N- (leucine aminopeptidase, LAP), and P- (acid phosphatase, AP) cycling along a vertical grassland belt of China. Soils from five depths (0-10, 10-20, 20-40, 40-60, and 60-100 cm) were sampled from three elevations (low, <1000 m; middle, 1000-2000 m; high, 2000-3000 m) and incubated at four temperatures (5, 15, 25, 35 °C). The average Q of soil EEA ranged from 0.97 to 1.11 and the Q of LAP was higher than that of BG and AP. Generally, the Q of BG and LAP both increased from low to middle elevation and then decreased, while the Q of AP was stable. Moreover, the effect of soil depth on Q of EEA was weakened from low elevation to high elevation, and the factors driving Q of soil EEA changed with elevation. This study improved the understanding of the vertical pattern of Q of soil EEA in water-limited ecosystems, and highlighted that elevation could regulate the effect of soil depth on Q of EEA.