Divergent responses of soil respiration to biocrusts during the nongrowing and growing seasons in a dryland shrubland ecosystem

Biocrusts, which are distinctive elements in arid and semiarid ecosystems, stand out as pivotal regulators of soil respiration. However, the intricate seasonal variability in the response of soil respiration to diverse biocrust types has not been determined. Using three years of continuous field measurements taken at hourly intervals, we explored the seasonal (nongrowing and growing seasons) responses of soil respiration to cyanobacteria-, lichen- and moss-dominated biocrusts in a shrubland on the Loess Plateau in China. Our results revealed that the effects of cyanobacteria-dominated biocrusts on total soil respiration varied between the nongrowing and growing seasons, whereas the effects of moss- and lichen-dominated biocrusts on total soil respiration showed no significant seasonal differences. Notably, the effect of biocrusts on seasonal soil respiration fluctuations was associated with the biocrust type, with biocrust layer respiration increasing mostly in the following order: cyanobacteria < lichen < moss. The magnitude of this effect was influenced not only by the biocrust type but also by the nongrowing and growing seasons. Soil temperature emerged as a primary driver of total soil respiration during the nongrowing season, whereas soil moisture predominated during the growing season. Moreover, annual precipitation dynamics may have shifted the roles of biocrusts and the key determinants of soil respiration. Collectively, our findings emphasize the importance of considering the nongrowing and growing seasons independently, as well as the specific biocrust type, when assessing the responses of soil respiration in arid and semiarid ecosystems.