Storage, Distribution, and Associated Controlling Factors of Soil Total Phosphorus Across the Northeastern Tibetan Plateau Shrublands

Although soil total phosphorus (TP) plays an important role in soil productivity and natural ecosystems, its spatial distribution patterns and controlling factors are rarely investigated at the regional scale of the Tibetan Plateau shrublands, due to great soil heterogeneity and the unavailability of soil samples. This study aims to explore storage, distribution, and associated controlling factors of TP across the northeastern Tibetan Plateau shrublands. To address this issue, we collected samples from 59 sites across the northeastern Tibetan Plateau shrublands in growing season from 2011 to 2013. The spatial distribution of TP was explored using kriging method, and the edaphic and climatic controlling factors were investigated. Our results showed that the 63.61 Tg TP stored in soil at 0-100 cm in the Tibetan Plateau shrublands, including 23.01 +/- 11.02 Tg in alpine shrublands and 40.60 +/- 23.20 Tg in desert shrublands. Overall, the TP density in the east was higher than that in the west, while that in the northwest was higher than that in the southwest. The mean annual precipitation (MAP) exhibited a significant increasing trend with increasing TP density in alpine shrublands, whereas the mean annual temperature (MAT) did not. The MAP in desert shrublands has relatively small effects on TP density than that in alpine shrublands. Effect of MAT on TP density was small in shrublands. These results differ from global trends showing that both the MAT and MAP are negatively correlated with TP, thus contributing to our understanding of the TP cycle under scenarios of global climate change. The TP density was positively correlated with soil organic carbon (SOC) while soil pH was negatively correlated with TP density. Nearly half portion of TP density variation in alpine shrublands was explained by soil pH, SOC density, MAP, while that in desert shrubland was explained by soil pH and SOC density. These results provide that in the Tibetan Plateau changes of increasing wetter and nitrogen deposition scenario, soil may potentially contribute to the TP sequestration in Tibetan Plateau shrublands.