Preferences for different nitrogen forms by coexisting plant species and soil microbes

Area of Science:

• Plant Ecology
• Soil Science
• Biogeochemistry

Background:

• Plants utilize diverse nitrogen (N) forms, including organic and inorganic. Resource partitioning via N form preference may reduce competition among coexisting species.
• Understanding plant and microbial N form preferences is crucial for plant community dynamics and nutrient cycling.

Purpose of the Study:

• To investigate N form preferences of coexisting temperate grassland plant species and soil microbes.
• To determine if plants and microbes partition N resources by utilizing different N forms, thereby reducing competition.

Main Methods:

• In situ stable isotope labeling with 13C15N-labeled amino acids (glycine, serine, phenylalanine) and 15N-labeled inorganic N.
• Assessing preferential uptake of different N forms by coexisting grass species and soil microbes in a temperate grassland.

Main Results:

• Coexisting plants simultaneously absorbed various N forms but preferred inorganic N over organic N, and simple amino acids over complex ones.
• Soil microbes initially outcompeted plants for added N, but plants became more effective N competitors in the long term (33 days).
• No preferential N form utilization was observed in soil microbes, contrary to some previous studies.

Conclusions:

• Coexisting grassland plants exhibit similar N form preferences, favoring inorganic N and simple amino acids.
• Plants can outcompete soil microbes for various N forms in the long term, potentially through microbial turnover or N remineralization.
• Resource partitioning by N form may not be a primary mechanism for avoiding competition among these coexisting plant species.