Exploring spatiotemporal dynamics in temporal stability of soil carbon, nitrogen, phosphorus, and pH in Tibetan grasslands

Effects of human activities and climate change on temporal stability of terrestrial ecosystems remains controversial. This study explored the spatiotemporal patterns and driving mechanisms of the temporal stability of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), their ratios (C:N, C:P, N:P), and pH at 0–10 cm, 10–20 cm, and 20–30 cm in the Tibetan grasslands during 2000–2020. Spatially averaged values of relative changes in temporal stability of soil variables ranged from –19.78 % to –6.85 %. In contrast, the relative changes of temporal stability of soil variables were increased for 31.39–45.98 % grassland areas. Climate change dominated changes in the temporal stability of soil variables in 31.50–44.07 % of grassland areas. Meanwhile, human activities predominated changes in 55.35–68.43 % of it. Compared to precipitation change and warming, radiation change had stronger effects on relative changes of temporal stability of SOC, TN, TP, C:N and C:P at 0–10 cm, SOC and TP at 10–20 cm, and TN and C:N at 20–30 cm. Soil variables themselves were not always positively correlated with their temporal stability, and may even be negatively correlated. Relative changes of temporal stability of soil variables were not always negatively but even positively correlated with relative changes of soil variables. Therefore, the interaction of climate change and human activities can homogenize or heterogeneize the spatial distributions of temporal stability of soil variables. The temporal stability of these soil variables overall decreased, with local increase. The areas of the change of temporal stability of soil variables caused by human activities were greater than those of climate change. Effects of radiation change on the spatio-temporal patterns of temporal stability of soil variables should be underlined. There were not always trade-off relationships between relative changes of soil variables and relative changes of temporal stability of soil variables.