5. Conclusions
In this paper, we studied the compound effects of soil C: N: P ratio and
enzyme stoichiometry under different land use patterns in the YRD, and
better revealed the biochemical cycle and microbial nutrient limitation
of YRD. The results showed that: (1) AG and WM could promote the
formation of soil macro-aggregates (> 0.25mm). AG was
beneficial to promote the mineralization of C, N, and P, but its effect
on the sequestration of TC and TP was not as good as WM. (2) According
to the soil C: N: P ratios, the levels of soil C and N in the YRD were
low, and AG could alleviate the limitation of aboveground vegetation
growth by N. (3) According to the enzyme stoichiometric, soil
microorganisms were generally limited by P in the YRD, while PC could
reduce the C limitation of soil microorganisms due to less soil
disturbance. Accordingly, we suggest that human disturbance, such as
mowing and soil disturbance, should be minimized in the agricultural
production of YRD, to alleviate C restriction. Reasonable planting of
alfalfa can alleviate N limitation. Meanwhile, we should increase the
input of soil P and carry out reasonable N management to deal with the
possible N limitation. In general,
ecological stoichiometry provided a theoretical basis for the rational
land use in the YRD.