The Three-River Headwaters region is a hotspot for studying the response of soil function to climate change. To study the horizontal variation characteristics of alpine grassland soil function and vertical changes along soil genetic horizons, soil functional indicators (including respiration, nitrogen conversion rate, and enzymatic activity) of different genetic horizons in alpine grassland soil profiles and their correlations with environmental factors were analyzed. The results showed that there were no significant differences in soil functional characteristics between alpine meadows and steppes, and topsoil had higher respiration rates, nitrogen conversion rates, and enzymatic activities than those of subsoil. Total nitrogen was a key driver of soil functional characteristics in different genetic horizons, explaining 18.3%, 21.4%, and 27.5% of the horizontal variation in functional characteristics, respectively. Climate and vegetation factors mainly affected soil function indirectly by changing soil physicochemical properties in topsoil, but atmospheric nitrogen deposition still affected soil function in subsoil. These results indicate the significant nitrogen limitation of alpine grassland soil in the Three-River Headwaters region, and the findings provide a new insight into the maintenance of soil functional diversity and the response to climate change in the context of global climate change.
Keywords: Three-River Headwaters region; environmental factors; genetic horizon; soil function; soil profile.