Drought shrinks terrestrial upland resilience to climate change

Abstract

Aim Drought has been shown to alter terrestrial ecosystem carbon (C) and nitrogen (N) dynamics, and thus feedback to future climate. However, drought‐induced changes in terrestrial upland C and N pools and the drought response of soil carbon dioxide (CO2) and nitrous oxide (N2O) fluxes are yet to be quantified. Location Global upland ecosystems. Time period 2000–2018. Major taxa studied Terrestrial C and N fluxes. Methods A meta‐analysis was conducted that compiled 1,344 measurements from 128 manipulative studies worldwide to obtain a general picture of terrestrial C and N cycling responses to soil drought stress and identify the primary driving factors. Results We showed that drought significantly decreased plant C pools, with stronger negative responses of aboveground than belowground C components. Drought significantly decreased soil respiration (RS) and N2O fluxes by 19% and 29%, respectively. There were non‐significant changes in soil organic C and N pools in response to drought; in contrast to a considerable decrease in soil dissolved organic C (−22%), there was a robust increase in soil nitrate‐N (26%) following short‐term drought impact. By relating net ecosystem productivity (NEP) to the difference between net primary production (NPP) and soil heterotrophic respiration (RH), drought was found to drive a decrease up to −37% in NEP, being equivalent to a reduction in terrestrial net C uptake of 2.91 t C/ha. Main conclusions Our study provides insights into soil release of CO2 and N2O with a linkage to the changes in terrestrial C and N pools in response to drought across upland biomes. Our findings highlight that, despite the lowered soil C release rate, the capacity of upland biomes as a C sink to slow climate change would still be weakened due to a robust decline of plant‐derived C input to soil in a future drier climate.

Moderate precipitation reduction enhances nitrogen cycling and soil nitrous oxide emissions in a semi‐arid grassland

“…Precipitation reduction may reduce soil N 2 O emissions directly through suppressing the growth and activities of N‐cycling microbes (i.e., nitrifiers and denitrifiers) (Borken & Matzner, 2009; Li et al, 2020). A meta‐analysis of 128 field experiments has recently shown that precipitation reduction significantly decreased N 2 O emissions in cropping and forest soils (Zheng et al, 2020), primarily because enhanced soil aeration is unfavorable for denitrification (Homyak et al, 2017; Zheng et al, 2020). Precipitation reduction may also affect soil N 2 O emissions indirectly by altering soil available N and/or C for nitrifiers and denitrifiers via reducing plant N uptakes, and/or photosynthate allocation belowground (Homyak et al, 2017; Shi et al, 2021).…”

Biochar Enhances the Resistance of Legumes and Soil Microbes to Extreme Short-Term Drought

“…The impacts of drought on soil functioning may depend on the duration of drought. In general, drought can depress CO 2 emissions and decrease soil dissolved organic C [ 17 ]. Meanwhile, the microbial community under drought may destabilize soil C [ 46 ].…”

“…Many studies have demonstrated that drought can influence soil microorganisms and underground nutrient cycling. Water deficits can evidently decrease soil respiration [ 17 ]. It is well-known that the soil microbial community is related to soil carbon cycling [ 18 ].…”

“…It is well-known that the soil microbial community is related to soil carbon cycling [ 18 ]. Drought can lead to a decrease in the soil C and N turnover rate in ecosystems [ 6 , 19 ] due to its negative impacts on soil microbial activities [ 17 , 20 ]. A field survey has demonstrated that arid conditions can reduce soil organic matter (SOM), total nitrogen (TN), ammonium, nitrate and available phosphorus (AP), overall resulting in a decrease in soil multifunctionality, which relates to soil microbial richness and diversity [ 21 ].…”

“…A field survey has demonstrated that arid conditions can reduce soil organic matter (SOM), total nitrogen (TN), ammonium, nitrate and available phosphorus (AP), overall resulting in a decrease in soil multifunctionality, which relates to soil microbial richness and diversity [ 21 ]. Drought can vastly decrease CO 2 emissions and soil dissolved organic C [ 17 ]. Short-term drought may depress soil N cycling [ 22 ], similarly to long-term drought.…”