Variation of soil organic carbon,nitrogen, and phosphorus stoichiometry and biogeographic factors across the desert ecosystem of Hexi Corridor,northwestern China

Purpose

The purposes of present study were to display the vertical distribution of soil organic carbon (SOC), nitrogen (N), and phosphorus (P) stoichiometry; identify the biogeographic characteristics of SOC, N, and P stoichiometry along an aridity gradient across the desert ecosystem of Hexi Corridor; and determine how biogeographic distribution patterns of SOC, N, and P stoichiometry are related to vegetation, soil texture, geography, and climate.

Materials and methods

We investigated the distribution and characteristics of SOC, N, and P stoichiometry based on samples collected from Hexi Corridor during 2011–2012 with total 400 plots of 80 sites. This region presents a precipitation gradient from about 250 mm in the east to less than 50 mm in the west. The measured variables included belowground and aboveground biomass, pH, bulk density, sand, clay, silt, SOC, N, and P contents. ANOVA analysis, reduced major axis, redundancy analysis, Person’s correlation, and regression analysis were used to analysis the variation of SOC, N, and P stoichiometry and related biogeographic factors.

Results and discussion

In present study, SOC, N, and P contents decreased significantly with increasing soil depth. C/N did not change significantly, while C/P and N/P decreased significantly. SOC and N, SOC and P, and N and P were well constrained within 0–100 cm. SOC, N, and P contents in 0–20 cm were higher than them in other studies. Vegetation, soil texture, climate, and geography could explain 91.6% of the total variance of soil stoichiometry. The impact of latitude and longitude on SOC, N, and P stoichiometry was mainly caused by the redistribution of precipitation, while the impact of altitude mainly resulted from the variation of temperature. With increasing aridity, SOC, N, and P contents and C/N/P ratios reduced consistently with inconsistent decrease rates.

Conclusions

Our results suggested that the interaction of vegetation structure, soil condition, and shortage of precipitation should be the main driver for the lower contents and much shallower distributions of SOC, N, and P of Hexi Corridor. The increasing aridity should be the critical factor that is responsible for the decrease of SOC, N, and P contents and C/N/P ratios. This study contributes to the understanding of soil stoichiometry in the desert ecosystem.