Stability of Ecosystem CO2 Flux in Response to Changes in Precipitation in a Semiarid Grassland

Abstract

Carbon dioxide (CO2) flux provides feedback between C cycling and the climatic system. There is considerable uncertainty regarding the direction and magnitude of the responses of this process to precipitation changes, hindering accurate prediction of C cycling in a changing world. We examined the responses of ecosystem CO2 flux to ambient precipitation and experimentally decreased (−35%) and increased precipitation (+20%) in a semiarid grassland in China between July 2013 and September 2015. The measured CO2 flux components included the gross ecosystem productivity (GEP), net ecosystem CO2 exchange (NEE), ecosystem respiration (Re), and soil respiration (Rs). The results showed that the seasonal and diurnal patterns of most components of ecosystem CO2 flux were minimally affected by precipitation treatments, with less than 4% changes averaged across the three growing seasons. GEP and NEE had a quadratic relationship, while Re and Rs increased exponentially with soil temperature. GEP, RE, and Rs, however, decreased with soil moisture. Decreased precipitation reduced the dependence of CO2 flux on soil temperature but partly increased the dependence on soil moisture; in contrast, increased precipitation had the opposite influence. Our results suggested a relatively stable CO2 flux in this semiarid grassland across the tested precipitation regimes.

Soil moisture controls the spatio-temporal pattern of soil respiration under different land use systems in a semi-arid ecosystem of Delhi, India

“…The variations in the rainfall pattern, intensity, and frequency have significant impacts on the S M , causing variation in SOM decomposition, S C mineralization, microbial activity, plant growth and species composition, above-and belowground biomass production, and plant phenological traits (Bao et al 2019;Zhang et al 2019). We observed a strong seasonal variation in the S R across all land uses, with higher S R rates during the rainy season, i.e., the hot-humid climate (July-September) when S M was not limiting (Fig.…”

“…Climate change has a strong impact on precipitation patterns across the globe (Arredondo et al 2018;Darrouzet-Nardi et al 2018). Changes in precipitation patterns in any terrestrial ecosystem will ultimately affect the S M , which in turn influence S MA , soil organic matter (SOM) decomposition pattern, and S R (Bao et al 2019). Arid and semi-arid ecosystems cover approximately 41% of the terrestrial land surface of the Earth (Wang et al 2014).…”

Multi-year CO<sub>2</sub> budgets in South African semi-arid Karoo ecosystems under different grazing intensities

“…Assessment of carbon uptake or release has turned into one of the most critical issues in environmental science in the last decade (Araújo et al, 2002;Ardö et al, 2008;K'Otuto et al, 2013;Nakano and Shinoda, 2018). Even though numerous studies on ecosystem carbon budget have been conducted, most of them have concentrated on European, Asian or North American mid-latitude ecosystems (Anthoni et al, 2004;Bao et al, 2019;Béziat et al, 2009;Fei et al, 2017;Nagy et al, 2006;Niu et al, 2020;Rannik et al, 2002;Rogiers, 2005;Schmid, 2002;Wang et al, 2016;Yan et al, 2017), while a lack of attention has been given to the African continent. Even though South Africa has been heavily affected by climate change during the recent decades (Hulme et al, 2001;Ziervogel et al, 2014), many gaps remain in the understanding of the semi-arid ecosystem carbon exchange (Archibald et al, 2009;Kutsch et al, 2008;Räsänen et al, 2017;Talore et al, 2016;Veenendaal et al, 2004).…”

“…Previous studies determined water availability as the main driver controlling gross primary production (GPP) through increasing photosynthesis and extending the length of the growing season (Ago et al, 2016;Bao et al, 2019;Meza et al, 2018;Otieno et al, 2010;Wang et al, 2019). However, the seasonal responses of GPP and ecosystem respiration (Reco) to precipitation pattern and the impacts of precipitation on the annual carbon budget are less well understood in the South African semi-arid ecosystems.…”

“…These ecosystems are highly seasonal with large parts of total annual precipitation occurring in only a few months of the year, and generally reveal pulse-driven evapotranspiration events in the rainy season. Phase and amplitude of photosynthesis and respiration are also highly dependent on the precipitation pattern (Archibald et al, 2009;Bao et al, 2019;Kutsch et al, 2008;Merbold et al, 2009;Räsänen et al, 2017). The strength of the ecosystem response to rainfall is not only determined by the amount of an individual event, but also on the timing of preceding events (Huxman et al, 2004;Ivans et al, 2006;Veenendaal et al, 2004;Williams et al, 2009;Yepez and Williams, 2009).…”