Different nitrogen uptake patterns of plant and soil microorganisms in the forest-grassland transition zone on the Loess Plateau.

INTRODUCTION

It is unclear whether plants and microorganisms achieve niche complementarity by taking up different inorganic nitrogen (N) forms to alleviate N competition, particularly in N-limited regions.

METHODS

This paper conducted a 15-day N tracer study (NHNO or NHNO) to quantitatively calculate the uptake rates of plants and microorganisms in four stands (pure L, pure Carrière, mixed -, and Weber ex Stechm grassland) in the forest-grassland transition zone on the Loess Plateau during the growing season. Among them, and can associated with arbuscular mycorrhizal and ectomycorrhizal, respectively.

RESULTS

The results indicated that in the pure stand and preferred to take up NO , whereas in the pure stand preferred NH . Compared to pure stands, mixed afforestation decreased the NH and NO uptake rate of by 87% and 70%, respectively, but did not alter the N preference of plants. Plants and microorganisms differed in their N preferences in the pure stand, whereas this was not the case in the mixed stand. The proportional similarity index between and (0.90 ± 0.01) was higher than that between plants and microorganisms in forest stands, except for and microorganisms in the mixed stand (0.90 ± 0.02).

DISCUSSION

Those results indicated that niche complementarity by preferring different N forms can alleviate N competition. This study helped to gain a deeper understanding of the plasticity of N uptake patterns by plants and microorganisms in the forest-grassland transition zone, and provides theoretical support for vegetation restoration during the implementation of the Grain for Green program on the Loess Plateau.