Canopy nitrogen and water addition affect fine-root survival strategies and carbon allocation in a warm-temperate forest in China

Abstract

Fine roots adapt to habitat changes, influencing plant survival strategies. However, there is a limited understanding of fine-root survival strategies under different nitrogen (N) and water treatments. Therefore, in an eight-year field control experiment conducted in a warm-temperate forest, we investigated the effects of changes in fine-root survival strategies in response to canopy N, canopy water, and N–water addition on fine-root biomass and functional diversity. Increases in soil nutrients (available N and moisture) promoted a conservative strategy of fine roots in dominant species, as indicated by the community-weighted mean. Compared to increasing tissue density in the non-growth period (with a maximum 44.6 % increase under canopy water addition), increasing fine-root diameter (up to 55.1 % increase under canopy N–water addition) and competition mitigated (maximum 49.9 % reduction under canopy N addition) the decrease in nutrient absorption rate indicators during the growth period, especially for absorptive fine roots. The conservative survival strategy adopted by dominant species provided living spaces for other species, thereby increasing fine-root biomass at the community level (maximum 33.4 % increase in non-growing seasons and 39.3 % in growing seasons, both under combined canopy N–water addition), particularly for non-dominant species. Our study elucidates the changes in fine-root survival strategies under different contexts that reflect potential climate change scenarios, and provides important evidence on the relationship between functional diversity and subsurface carbon allocation.