Effects of climate variables on ecosystem carbon exchange and soil respiration
As expected, we found that NEE, ER and GEP were all influenced by precipitation which was highest in July and August (Fig. S1, Fig. S2b). This is likely primarily a result of the influence of aboveground biomass and its influence on productivity and ecosystem carbon exchange, which is strongly influenced by variation in rainfall (Jobbagy et al. 2002). We also showed that soil moisture was positively correlated with ER and SR (Fig. S2d), which likely promoted the growth of plant roots to enhance microbial activity and promote organic matter decomposition, leading to an increase soil respiration (Helfter et al. 2015; Peng et al. 2015). This is consistent with previous studies in desert steppe (Jin et al.2023; Wang et al. 2023).
Likewise, variation in temperature influences ecosystem carbon exchange mainly by affecting GEP and ER (Luo et al. 2001; Ganjurjavet al. 2018; Li et al. 2019). However, consistent with our results showing a minimal influence of temperature on ecosystem carbon exchange in a desert steppe (Fig. S2a), WU et al. (2021) found similar results in a 12-year study. We did, however, find that variation in soil temperature contributed to ER (Fig. S2c), which was consistent with results from a previous analysis.