Al/Fe Mineral Controls on Soil Organic Carbon Stock Across Tibetan Alpine Grasslands

Adequate understanding of the controlling factors of soil carbon (C) stock is crucial for improving the predictability of Earth System Models in exploring terrestrial C-climate feedback. Current studies, however, mainly focus on climatic and edaphic variables and rarely explore the effects of mineral protection in regulating soil organic carbon (SOC) stock over broad geographic scale. Particularly, the relative importance of mineral protection compared with other factors is unclear. Based on large-scale soil inventory, here we filled this knowledge gap by exploring the effects of Al/Fe-(hydr) oxides on SOC and three C fractions across Tibetan alpine grasslands via linear regression, partial correlation, and variance partitioning analyses, and also by comparing the degree of mineral protection in alpine grasslands with other ecosystems. Our results showed that SOC and C fractions across Tibetan alpine grasslands were regulated by Al/Fe-(hydr) oxides, with the incorporation of mineral variables increasing the explained variations by 10.1% for SOC content, 13.4% for coarse particulate organic matter, 12.6% for microaggregate associated C, and 21.9% for silt and clay associated C. Moreover, the contribution of mineral effects exceeded that of climatic and edaphic factors, particularly in the silt and clay associated C fraction. In addition, about 15.812.0% of SOC pools were associated with Fe, which was equal to or higher than those in temperate and tropical-subtropical ecosystems. Taken together, these results demonstrate the significant role of Al/Fe minerals in the stabilization of SOC across Tibetan alpine grasslands, highlighting the importance of incorporating C-mineral interactions into ESMs for better understanding the terrestrial C-climate feedback

Increasing water availability and facilitation weaken biodiversity–biomass relationships in shrublands

Positive biodiversity–ecosystem‐functioning (BEF) relationships are commonly found in experimental and observational studies, but how they vary in different environmental contexts and under the influence of coexisting life forms is still controversial. Investigating these variations is important for making predictions regarding the dynamics of plant communities and carbon pools under global change. We conducted this study across 433 shrubland sites in northern China. We fitted structural equation models (SEMs) to analyze the variation in the species‐richness–biomass relationships of shrubs and herbs along a wetness gradient and general liner models (GLMs) to analyze how shrub or herb biomass affected the species‐richness–biomass relationship of the other life form. We found that the positive species‐richness–biomass relationships for both shrubs and herbs became weaker or even negative with higher water availability, likely indicating stronger interspecific competition within life forms under more benign conditions. After accounting for variation in environmental contexts using residual regression, we found that the benign effect of greater facilitation by a larger shrub biomass reduced the positive species‐richness–biomass relationships of herbs, causing them to become nonsignificant. Different levels of herb biomass, however, did not change the species‐richness–biomass relationship of shrubs, possibly because greater herb biomass did not alter the stress level for shrubs. We conclude that biodiversity in the studied plant communities is particularly important for plant biomass production under arid conditions and that it might be possible to use shrubs as nurse plants to facilitate understory herb establishment in ecological restoration.ISSN:0012-9658ISSN:1939-917