Biotic factors dominantly determine soil inorganic carbon stock across Tibetan alpine grasslands

Abstract

Abstract. The soil inorganic carbon (SIC) pool is a major component of soil carbon (C) pools, and clarifying the predictors of SIC stock is urgent for decreasing soil C losses and maintaining soil health and ecosystem functions. However, the drivers and their relative effects on the SIC stock at different soil depths remain largely unexplored. Here, we conducted a large-scale sampling to investigate the effects and relative contributions of abiotic (climate and soil) and biotic (plant and microbe) drivers on the SIC stock between topsoils (0–10 cm) and subsoils (20–30 cm) across Tibetan alpine grasslands. Results showed that the SIC stock had no significant differences between the topsoil and subsoil. The SIC stock showed a significant increase with altitude, pH and sand proportion, but declined with mean annual precipitation (MAP), plant aboveground biomass (PAB), plant coverage (PC), root biomass (RB), available nitrogen (AN), microbial biomass carbon (MBC), and bacterial abundance (BA) and fungal gene abundance (FA). For both soil layers, biotic factors had larger effects on the SIC stock than abiotic factors did. However, the relative importance of these determinants varied with soil depth, with the effects of plant and microbial variables on SIC stock weakening with soil depth, whereas the importance of climatic and edaphic variables increased with soil depth. Specifically, BA, FA and PC played dominant roles in regulating SIC stock in the topsoil, while soil pH contributed largely to the variation of SIC stock in the subsoil. Our findings highlight differential drivers over SIC stock with soil depth, which should be considered in biogeochemical models for better simulating and predicting SIC dynamics and its feedbacks to environmental changes.

Soil texture and microorganisms dominantly determine the subsoil carbonate content in the permafrost-affected area of the Tibetan Plateau

“…The soil C pool, composed of soil organic carbon (SOC) and soil inorganic carbon ( SIC ) pools, has great potential for carbon sequestration ( Tan et al, 2014 ; Zhang et al, 2015 ). Most previous studies on alleviation of elevated atmospheric CO 2 levels have concentrated on the SOC pool because it responds quickly to global climate change, such as warming and nitrogen (N) deposition, and it is strongly linked with various ecosystem functions ( Jobbagy and Jackson, 2000 ; Yang et al, 2012 ; Pan et al, 2022 ; Mayer et al, 2023 ). On the other hand, compared to the relatively short turnover time of SOC, SIC has a long resident time in the soil C pool and a long renewal cycle, which is considered to be slow in response to global changes and vegetation succession ( Monger et al, 2015 ; Zang et al, 2018 ).…”

“…Contrary to abiotic factors, the role of microorganisms has been overlooked because the soil microbial activity is poor in desert ecosystems, which have sparse vegetation ( Ferdush and Paul, 2021 ). However, it has also been reported that soil microorganisms can induce carbonate mineral formation and increase the storage of inorganic C pools in arid and semi-arid areas ( Pere and Ramn, 2008 ; Zhao et al, 2020 ; Pan et al, 2022 ). Thus, it is important to accurately predict the dynamic change in soil C in a desert ecosystem to determine whether the microbial presence affects carbonate mineral formation.…”

“…In the past several decades, the plateau has experienced significant warming ( Qin et al, 2021 ). This continuous warming has resulted in a significant increase in permafrost thawing rate and microbial activity ( Jansson and Tas, 2014 ; Wu et al, 2015 ), which can likely induce changes in soil carbonate content and SIC stock through biogeochemical processes ( Raza et al, 2020 ; Pan et al, 2022 ). Hence, an alluvial fan distributed in desert and steppe ecosystems was selected to explore the influence of soil microorganisms on carbonate mineral formation in permafrost regions via phospholipid fatty acid (PLFA) analysis.…”

E-SCAN: Electrochemical Scanning of Carbonates, an In Situ Approach for Screening and Quantifying Inorganic Carbon in Soil

“…The potential of efficient carbon sequestration promises improved soil health that increases agricultural productivity, food security values, and climate resilience, i.e., a possibility to combat climate change effects, and also reduces fertilizer usage, which brings down the financial burden on farmers and agricultural overhead. , Therefore, in order to come up with these strategic management practices that will help with carbon sequestration and regenerative farming, it is vital to understand, probe, and track soil carbon from these different sources as an aggregate holistic measure. It has been recently understood by scientific communities, environmental agencies, and community users at large − that although useful, it is not completely sufficient to only track soil organic carbon (SOC), and looking into understanding soil inorganic carbon (CSM) and thereby capitalizing on evaluating total carbon is also important as an objective surrogate measure to keep tabs on carbon sequestration in an on-demand manner at the point of use (PoU), which would be a breakthrough innovation in this field, since monitoring and verifying carbon removal/addition via soil carbon sequestration are currently difficult and costly. This sort of sensing platform that could detect CSM levels and extrapolate TSC values would be greatly beneficial toward governance perspectives for technical assistance, financial incentives, and, just from an environmental standpoint, monitoring, verification, and reporting .…”

The Contribution of Biotic Factors in Explaining the Global Distribution of Inorganic Carbon in Surface Soils

“…However, much less is known about the role of biotic factors in driving SIC across the globe, despite the well‐known importance of vegetation and soil microbes in controlling terrestrial C pools (Chen et al., 2019; García‐Palacios et al., 2021; Gavazov et al., 2022). Recent studies have emphasized the importance of biotic factors in driving SIC distributions at local or regional scales (Ahmad et al., 2013; Pan et al., 2022). For example, the biotic‐driven decomposition of organic matter associated with plant productivity and soil microbial biomass could alter SIC content by increasing CO 2 partial pressure and causing acidification, releasing CO 2 into the atmosphere (Pan et al., 2022; Shi et al., 2020; Zamanian & Kuzyakov, 2019).…”