Eddy covariance and biometric measurements show that a savanna ecosystem in Southwest China is a carbon sink

Abstract

Savanna ecosystems play a crucial role in the global carbon cycle. However, there is a gap in our understanding of carbon fluxes in the savanna ecosystems of Southeast Asia. In this study, the eddy covariance technique (EC) and the biometric-based method (BM) were used to determine carbon exchange in a savanna ecosystem in Southwest China. The BM-based net ecosystem production (NEP) was 0.96 tC ha −1 yr −1 . The EC-based estimates of the average annual gross primary productivity (GPP), ecosystem respiration (R eco ), and net ecosystem carbon exchange (NEE) were 6.84, 5.54, and −1.30 tC ha −1 yr −1 , respectively, from May 2013 to December 2015, indicating that this savanna ecosystem acted as an appreciable carbon sink. The ecosystem was more efficient during the wet season than the dry season, so that it represented a small carbon sink of 0.16 tC ha −1 yr −1 in the dry season and a considerable carbon sink of 1.14 tC ha −1 yr −1 in the wet season. However, it is noteworthy that the carbon sink capacity may decline in the future under rising temperatures and decreasing rainfall. Consequently, further studies should assess how environmental factors and climate change will influence carbon-water fluxes.Savanna ecosystems are characterized by distinct wet and dry seasons, the codominance of C3 trees and C4 grasses 1 , and their location mainly in the tropics and subtropics. They cover almost 60%, 50%, and 45% of the areas of Africa, Australia, and South America, respectively, and more than 10% of the area of Southeast Asia 2 . They play an increasing role in the carbon cycle and energy fluxes in the context of climate changes (e.g., decreasing precipitation and increasing temperature), as they cover approximately 20.0% (2.7 billion ha) of the global land surface 1,3-5 and account for ~30% of the net primary production (NPP) of the terrestrial ecosystem 6 . Savannas also have a large and rapidly growing human population: about one-fifth of the global population is supported by savanna ecosystems 3,4,7 . The carbon exchange of savanna ecosystems, therefore, has a significant influence on global carbon cycling. Consequently, research on the spatiotemporal characteristics of carbon exchange and its responses to biotic and abiotic controls on savanna ecosystems is of great importance, not only for improved fundamental ecological understanding of the impact of global change on carbon fluxes but also for the improved protection and management of this vulnerable ecosystem type for sustainable development and provision of better ecosystem services (e.g., the management of resources, water, biodiversity, and climate change).

Spatial Pattern of Carbon Sequestration and Urban Sustainability: Analysis of Land-Use and Carbon Emission in Guang’an, China

“…Forests are primary carbon absorbers, and the carbon sequestration function of plantation forests can help mitigate global climate change [68,69]. Some scholars have also come to a similar conclusion; that is, an important factor in the change of carbon sequestration eco-services is that the government reduces ecological land area to increase construction land area [70][71][72]. Our results also verify the conclusions of these scholars.…”

The influence of drought strength on soil respiration in a woody savanna ecosystem, southwest China

“…However, some other studies showed that drought could increase the soil respiration, and weaken the strength of ecosystems carbon sink and even change them into carbon sources (Cox et al 2000;Jones et al 2003;Ciais et al 2005;Shi et al 2014), but these findings are often uncertain (Sowerby et al 2008;Zhang et al 2015). By both eddy covariance and biometric methods, Fei et al (2017) found that the Yuanjiang savanna ecosystem was a weak carbon sink. Strong seasonal variation of NEE was observed at the study site, and the annual NEE varied with annual precipitation year by year.…”

The role of understory phenology and productivity in the carbon dynamics of longleaf pine savannas

“…, Fei et al. ), thus representing a significant portion of the global carbon cycle (Bombelli et al. ).…”

“…Understanding savanna structure and function is critically important, as savannas cover~15% of the global land surface (Ma et al 2013) and con-tribute~30% to global net primary production (NPP, Field et al 1998, Fei et al 2017, thus representing a significant portion of the global carbon cycle (Bombelli et al 2009). Nevertheless, savanna ecosystems vary across the globe based on their underlying geology and regional climates (Bond et al 2003, Vaughn et al 2015.…”