摘要
Aims Fine roots play an important role in the biogeochemical cycles of terrestrial ecosystems and are vital for understanding forest ecosystem functioning and services.Higher plant species diversity has been largely reported to increase aboveground community biomass,but how biodiversity affects fine-root production and the related mechanisms in forests remain unclear.In this study,we aim to answer two questions:(i)does fine-root production increase with tree species richness?(ii)Can this effect be explained by niche complementarity among species?Methods We analyzed data from a large forest biodiversity experiment(BEF-China)with 5-year-old trees.Fine-root growth was measured as standing biomass and annual fine-root regrowth was estimated using ingrowth cores.Moreover,relative yield was calculated to test whether over-or under-yielding occurred when mixtures were compared with the average monoculture of the species included in the mixtures.We calculated functional diversity for fine-root(≤2 mm in diameter)traits by Rao’s quadratic entropy index for each species mixture.The effects of manipulated tree species richness and identity on fine-root traits were analyzed with linear mixed-effects models.Mixed models were also used to test the relationships between tree species richness and fine-root standing biomass,annual regrowth and vertical heterogeneity.Important Findings Fine roots of more than one species were found in half of the soil cores in mixtures indicating that belowground interactions in these young forest stands occurred much earlier than canopy closure.We found significant differences among species in fine-root traits such as diameter and specific root length(SRL),which suggested different resource-use strategies and niche partitioning among species.Mean fine-root diameter of species ranged from 0.31 to 0.74 mm,mean SRL ranged from 12.43 m·g^(−1)to 70.22 m·g^(−1)and mean vertical distribution indexβranged from 0.68 to 0.93.There was a significant positive relationship between species richness a
基金
the general support of the whole BEF-China team
the Sino-German Centre for Research Promotion in Beijing for travel grants and the participation in a summer school on scientific writing(GZ 785)
funded by grants from the National Natural Science Foundation of China(No.31270496 and No.31300353).