Rainfall pulse response of carbon fluxes in a temperate grass ecosystem in the semiarid Loess Plateau

Abstract

Rainfall pulses can significantly influence carbon cycling in water‐limited ecosystems. The magnitude of carbon flux component responses to precipitation may vary depending on precipitation amount and antecedent soil moisture, associated with nonlinear responses of plants and soil microbes. The present study was carried out in a temperate grass ecosystem during 2013–2015 in the semiarid Loess Plateau of China, to examine the response of carbon fluxes to precipitation using the “threshold‐delay” model. The unique contribution of environmental variables such as precipitation amount and antecedent soil moisture before rainfall (SWC_antecedent) to carbon fluxes in response to rainfall was also investigated. The lower threshold of effective rainfall was 6.6 mm for gross ecosystem production (GEP), 8.5 mm for net ecosystem production (NEP), and 4.5 mm for ecosystem respiration (RE); and the upper threshold of effective rainfall was 21.4 mm for GEP and NEP, and 16.8 mm for RE. Rainfall amount was positively affected the relative rainfall responses of GEP, NEP, and RE. However, SWC_antecedent at 20 cm soil depth offset the response of GEP to rainfall pulses, and SWC_antecedent at 5 cm soil depth offset the response of NEP and RE to rainfall pulses, with corresponding partial slopes of linear regressions of −0.50, −0.40, and −0.52. These results indicated that NEP was more sensitive to rainfall pulses and RE was more sensitive to SWC_antecedent. These results demonstrate the importance of rainfall events of <10 mm and that the negative effect of SWC_antecedent should also be considered when estimating ecosystem carbon fluxes in this semiarid region.

Landscape‐Scale Plant Water Content and Carbon Flux Behavior Following Moisture Pulses: From Dryland to Mesic Environments

“…The NEP behavior shows photosynthetic rates consistently increasing above pre-storm levels and eventual decreases given sufficient drying between storms. This behavior is broadly consistent with previously measured NEP behavior at similar dryland sites (Chen et al, 2009;Guo et al, 2016;Hao et al, 2010;Loik, 2007;Scott et al, 2006;Tang et al, 2018). Note that longer durations of NEP and GPP increases have been observed previously (Kurc and Small, 2007;Williams et al, 2009).…”

“…While field studies have not directly assessed such growth and storage mechanisms (Collins et al., 2014), they have instead evaluated leaf gas exchange and plant hydraulic (i.e., via predawn water potential) responses to rain pulses (Huxman, Snyder, et al., 2004; Sala & Lauenroth, 1982; Williams et al., 2009). Overall, these studies generally agree that small rain events induce ecosystem respiration efflux responses (e.g., the “Birch” effect, Jarvis et al., 2007) and larger rain events additionally result in greater water uptake, transpiration, and primary production responses (Chen et al., 2009; Q. Guo et al., 2016; Schwinning et al., 2004; Tang et al., 2018; Xu et al., 2004). Some studies note that antecedent soil moisture conditions explain differences in response magnitude and duration (J. S. Guo and Ogle, 2019; Potts et al., 2006; Tang et al., 2018).…”

“…Overall, these studies generally agree that small rain events induce ecosystem respiration efflux responses (e.g., the “Birch” effect, Jarvis et al., 2007) and larger rain events additionally result in greater water uptake, transpiration, and primary production responses (Chen et al., 2009; Q. Guo et al., 2016; Schwinning et al., 2004; Tang et al., 2018; Xu et al., 2004). Some studies note that antecedent soil moisture conditions explain differences in response magnitude and duration (J. S. Guo and Ogle, 2019; Potts et al., 2006; Tang et al., 2018). However, there have been few efforts to reconcile whole‐plant pulse responses beyond individual sites (Ogle & Reynolds, 2004; Reynolds et al., 2004).…”

“…and Lauenroth, 1982;Williams et al, 2009). Overall, these studies generally agree that small rain events induce ecosystem respiration efflux responses (e.g., the "Birch" effect, Jarvis et al, 2007) and larger rain events additionally result in greater water uptake, transpiration, and primary production responses (Chen et al, 2009;Guo et al, 2016;Tang et al, 2018;. Some studies note that antecedent soil moisture conditions explain differences in response magnitude and duration (Guo and Ogle, 2019;Potts et al, 2006;Tang et al, 2018).…”

“…Threshold behavior has been detected previously in semi-arid environments, though primarily using rain depth (Chen et al, 2009;Hao et al, 2010;Sala. and Lauenroth, 1982;Tang et al, 2018). Use of soil moisture is preferred here because it holds more information about initial moisture conditions (Reynolds et al, 2004).…”