Increasing soil carbon stocks in eight permanent forest plots in China

Abstract

Forest soils represent a major stock of organic carbon (C) in the terrestrial biosphere, but the dynamics of soil organic C (SOC) stock are poorly quantified, largely due to lack of direct field measurements. In this study, we investigated the 20-year changes in SOC stocks in eight permanent forest plots, which represent boreal (1998-2014), temperate (1992-2012), subtropical (1987-2008), and tropical forest biomes (1992-2012) across China. SOC contents increased significantly from the 1990s to the 2010s, mostly in the upper 0-20 cm soil depth, and soil bulk densities do not change significantly during the same period. As a result, the averaged SOC stocks increased significantly from 125.2 ± 85.2 Mg C ha −1 in the 1990s to 133.6±83.1 Mg C ha −1 in the 2010s across the forest plots, with a mean increase of 127.2-907.5 kg C ha −1 yr −1 . This SOC accumulation resulted primarily from increasing leaf litter and fallen logs, which accounts 3.6 %-16.3 % of above-ground net primary production. Our findings provided direct evidence that China's forest soils have been acting as significant C sinks, although their strength varies in forests with different climates.

Uncertainty and Emergent Constraints on Enhanced Ecosystem Carbon Stock by Land Greening

“…This study shows a positive impact of global land greening on terrestrial ECS during the past three decades. This finding is consistent with recent empirical evidence on the associated increases in vegetation biomass (Fang et al., 2014; C. Zhu & Xia, 2020) and soil C stock (G. Zhou et al., 2006; J. Zhu et al., 2020) in terrestrial ecosystems since the 1980s. The enhanced net primary productivity with land greening can be an important mechanism underlying the increase in terrestrial ECS (Figure S16a in Supporting Information ).…”

Identifying the Full Carbon Sink of Forest Vegetation: A Case Study in the Three Northeast Provinces of China

“…Simple numerical simulation of the carbon cycle process using the model method may ignore the carbon loss process which may lead to overestimation of the carbon sequestration. The rate of soil carbon sequestration in this study was between 0.18-0.20 tC•hm −2 •year −1 , which is a little lower than the results of Zhu et al, for the northern forest areas of China (0.24 tC•hm −2 •year −1 ) [50], and similar to the result of Fang et al (0.2 tC•hm −2 •year −1 ) [16]. At the regional scale, Xu et al [51] found that temperate forest carbon sinks were 0.94 tC•hm −2 •year −1 based on monitoring data and flux data, which are similar to the results of Harris et al [52] (0.64 tC•hm −2 •year −1 ).…”

Spatial Distribution of Soil Organic Carbon in the Forests of Nepal

“…Group I includes 15 different forest types classified by the DFRS [43] based on tree species composition. They are (1) Shorea robusta forest (S), (2) Terai mixed hardwood forest (TMH), (3) lower mixed hardwood forest (LMH), (4) Pinus roxburghi forest (Pr), (5) Pinus wallichiana forest (Pw), (6) Quercus forest (Q), (7) upper mixed hardwood forest (UMH), (8) Abies forest (A), ( 9) Cedrus deodara forest (Ce), (10) Betula utilis forest (Bu), (11) Picea smithiana forest (Ps), (12) Cupressus torulosa forest(Ct), ( 13) Tsuga dumusa forest (Td), ( 14) Juglans wallichiana forest (Jw), and (15) Acacia catechu/Dalbergia sisso forest (AC/DS). Group II includes broadleaved forest, mixed forest, and coniferous forest, as classified by Shrestha [47] based on structural features.…”

“…Understanding the dynamics and distribution of SOC in forest soils is essential to better predict the forest SOC [10]. However, the dynamics of the SOC stock are poorly quantified, largely due to a lack of direct field measurements [11]. The estimations presented in this study provide a baseline for estimating future changes in soil C stocks in Nepal, and for assessing their vulnerability to key global change drivers, thereby informing future actions aimed at the conservation and management of C stocks [12].…”