| High water-holding forests are essential for adapting to drought climates under global warming,and a central issue is which type of forests could conserve more water in the ecosystem.720 sample plots were investigated,including 28 tree species and 18054 trees.Water-holding capacities were measured as four soil indices(Maxwc,maximum water-holding capacity;Fcwc,field water-holding capacity;Cpwc,soil capillary water-holding capacity;Ncpwc,non-capillary water-holding capacity),two litter metrics(Maxwcl,maximum water-holding capacity of litters;Ewcl,effective water-holding capacity of litters),and canopy interception.This paper explores how forest structure,plant diversity,and soil physics impact forest water-holding capacities.The research results are as follows:(1)The tree size index in the community structure has a significant impact on the water conservation function: compared with small trees,big-sized trees plot was 4-25% higher in the litters,54-64% in the canopy,and 6-37% in the soils.The litter with high tree density has a stronger water-holding capacity,which is 1.19-2.19 times that of low tree density.With the increase of ECM species,the explanation rate of community structure for water conservation function increases,ranging from 9.7-47.3%.(2)The soil with higher species richness has stronger water-holding capacity,and the effective water-holding capacity and canopy interception of litter in the sample plots with high Simpson and Shannon-Wiener are 10-27% higher than those in the plots with the lowest species richness.Structural equation model analysis showed that species richness significantly increased the effective water-holding capacity of litter(0.081),and all water-holding capacity parameters could be improved(0.013-0.077).Tree size indexes(tree height,DBH and height under branches)directly increased canopy interception(0.161),soil non-capillary water capacity(0.135)and effective water capacity of litter.(3)The analysis of the impacts of different mycorrhizal types on water conservation function revealed that the litter water-holding capacity in ECM communities was 1.6–2.0 times that of AM and AM+ECM.The C of ECM was the highest,which was significantly higher than that of AM+ECM;The Fcwc of ECM was significantly lower than that of AM and AM+ECM.The Ncpwc of ECM was 42% and 78% higher than that of AM and AM+ECM,respectively(p< 0.05).ECM-dominant forest with low species evenness,big-sized trees,low bulk density and high soil moisture content increased the multiple water-holding capacities.AM-dominant forest with high density,high mingling degree had stronger litter water holding capacity,and the canopy interception capacity of big-sized trees was stronger.4)Physical properties of soil are the most powerful explanatory factors of water conservation function.It explains 90.5% of the variation of water conservation function,followed by 5.9% of the community structure,and the plant diversity is at least 0.2%.And the contribution of soil properties to water conservation function ranks in the top three under different mycorrhizal types.Bulk density was negatively correlated with the Maxwcl,Fcwc and Cpwc(p< 0.05),while soil water content was positively correlated with soil water capacity and canopy interception.The results showed that the establishment and management of temperate water conservation forest should increase the dominance of ECM trees,and the mixed forest of large trees and rich species can effectively improve the water conservation function of the ecosystem. |
