Response of the Organic Carbon Fractions and Stability of Soil to Alpine Marsh Degradation in Zoige, East Qinghai-Tibet Plateau

Abstract

Soil organic carbon (SOC) fractions play a crucial role in the carbon cycle of alpine wetland ecosystems and regional climate regulation. In the last decades, alpine marshes at Tibetan Plateau have undergone increased degradation. The effects of marsh degradation on soil labile and recalcitrant organic carbon fractions and on SOC stability remain unclear. In this study, we investigated changes in SOC fractions with different biochemical recalcitrance and stability in the marsh ecosystems with various levels of degradation in the Zoige Wetland, Eastern Qinghai-Tibet Plateau. Soil samples of relatively pristine marsh (RPM), lightly degraded marsh (LDM), moderately degraded marsh (MDM), heavily degraded marsh (HDM) and severely degraded marsh (SDM) were collected and analysed using the acid hydrolysis method. Compared with RPM, the concentrations of SOC labile fraction I (non-cellulosic polysaccharides), SOC labile fraction II (cellulose) and recalcitrant organic carbon (ROC) in degraded marshes decreased significantly: 29-97, 38-95 and 32-99%, respectively, except for the LDM. The SOC recalcitrance index (RIc) in the HDM and SDM was significantly lower than that in RPM by 11-35 and 15-47%, respectively; compared with RPM, the stability of organic carbon was significantly lower in the HDM and SDM. Additionally, the marsh degradation increased vertical variation in the concentrations of SOC fractions. The degradation of alpine marshes decreases the capacity for carbon (C) sequestration via decreasing the resistance of SOC to biodegradation, indicating that the alpine marsh degradation may weaken the carbon sink capacity of the Zoige Plateau, thus aggravating the global greenhouse effect. Keywords Zoige. Marsh degradation. Labile organic carbon. Recalcitrant organic carbon. Soil organic carbon stability Highlights • Concentrations of labile and recalcitrant SOC decreased with marsh degradation. • Vertical variation in labile and recalcitrant SOC increased in degraded marshes. • Resistance of SOC to biodegradation decreased after marsh was moderately degraded. • Marsh degradation reduced the capacity of SOC sequestration.

Transformation of phosphorus forms and its regulation on phosphorus availability across differently degraded marsh soils

“…Additionally, the loss of C pools owing to marsh degradation may also result in the release of moderate labile inorganic P from organic matter (Zhang et al, 2015). In this study, an increase in organic acids associated with a mobilization of phosphate-dissolving bacteria and a loss of organic C (Almeida et al, 2020;Gatiboni et al, 2021;Pu et al, 2020;Susilowati et al, 2019) can improve the activation from soil Ca 10 -P to organic P, non-occluded P and Ca 2 -P under marsh degradation, which was related to aerobic conditions and/or dense plant communities in degraded marshes. Therefore, the transformation from Ca 10 -P to Ca 2 -P via organic P and the nonoccluded P path was an important regulatory mechanism of P availability in soils during marsh degradation on the Zoige Plateau.…”

“…Marsh wetlands on the Zoige Plateau with alpine and fragile environments are located on the eastern edge of the Qinghai‐Tibet Plateau, China, and have undergone degradation to different degrees because of climate changes and anthropogenic activities over the past 60 years (Shen et al, 2019). During the degradation process of marshes, the capacity of soil C sink decreased continuously (Ma et al, 2016; Pu et al, 2020; Zhou et al, 2020), which would likely accelerate wetland degradation and affect the processes of the P cycle, leading to a weakening of wetland ecological service functions, such as regulating climate, biodiversity maintenance and water conservation (Hambäck et al, 2022; Sun et al, 2023). More importantly, there exists a close coupling relationship among C, N and P elements (Luo et al, 2021; Newman et al, 2017).…”

Transformation of phosphorus forms and its regulation on phosphorus availability across differently degraded marsh soils

“…Additionally, the loss of carbon pools owing to marsh degradation may also result in the release of moderate labile inorganic P such as Fe-P and Al-P from organic matter (Yuan et al, 2015;Zhang et al, 2015). In this study, an increase in organic acids associated with a mobilisation of phosphate-dissolving bacteria and a loss of organic carbon (Gatiboni et al, 2021, Almeida et al, 2020Susilowati et al, 2019;Pu et al, 2020) can improve the activation from soil Ca 10 -P to organic P, non-occluded P and Ca 2 -P under marsh degradation. Therefore, the transformation from Ca 10 -P to organic P was an important regulation mechanism of P availability in soils during marsh degradation on the Zoige plateau.…”

“…Marsh wetlands on the Zoige Plateau with alpine and fragile environments are located on the eastern edge of the Qinghai-Tibet Plateau, China, and have undergone degradation to different degrees because of natural threats and human activities over the past 60 years (Li et al, , 2019Shen et al, 2019). Several studies have revealed that alpine marsh degradation has decreased soil C sink function by increasing C emission fluxes in the Zoige Plateau (Ma et al, 2016;Pu et al, 2020;Zhou et al, 2020). Furthermore, total P and available P significantly affect the concentration of organic C in the Zoige peatland soils (Luo et al, 2021).…”

Estimation and mapping of soil texture content based on unmanned aerial vehicle hyperspectral imaging

“…Traditional soil texture measurement methods rely on field soil sampling and laboratory chemical analysis, which are time-consuming, laborious, and costly, making it difficult to conduct large scale and multifrequency soil texture content monitoring 6 , 7 . In recent years, rapidly developing vision-near-infrared hyperspectral technology has been widely used in soil texture content estimation to address the contradiction between the demand for big data of soil texture and high cost 8 .…”