| Bamboo and broad-leaved mixed forest is an excellent bamboo-wood mixed forest in southern China.It has high ecological and economic value,especially in maintaining the balance of the bamboo forest ecosystem and improving the productivity of Phyllostachys edulis in the forest.The bamboo and broad-leaved mixed forests are mostly formed after the degradation of natural secondary forests.However,there are different research opinions on the optimal mixed ratio of bamboo and broad-leaved mixed forests and the optimal associated broad-leaved species of bamboo,and most of the studies are not systematic,which seriously restricts the scientific management and comprehensive benefits of the bamboo and broad-leaved mixed forest.Therefore,the internal environment of different types of bamboo and broad-leaved mixed forests is unscientific.The systematic research on the environmental factors and bamboo biomass is beneficial to the sustainable management of bamboo and broad-leaved mixed forests.From the perspective of the population,we analyzed the canopy structure,soil characteristics,soil microbial community and bamboo biomass along a proportional gradient of 0–40% mixed-ratio(as represented by the width and size of the broad-leaved tree crown over the plot area)of bamboo and broad-leaved forest in Tianbao Yan Nature Reserve.From an individual point of view,a quantitative analysis of the light environment,soil nutrients,microbial activity and biomass of bamboos around the different native broadleaved trees in moso bamboo and broadleaved mixed forest,including Castanopsis chinensis Hance(CC),Alniphyllum fortune(Hemsl.)Makino(AF),Choerospondias axillaris(CA)in this work.Finally,the forest environment,micro-ecology,and economy are comprehensively evaluated,the best mixed ratio is recommended at the group level,and the appropriate mixed broad-leaved tree species and the corresponding mixed ratio are recommended at the individual level.The research has enriched the theoretical basis for the cultivation of broad-leaved trees in the bamboo and broad-leaved mixed forest.Provide theoretical reference for precise management of bamboo and broad-leaved mixed forest.The main results are as follows:1.In the study of forest canopy structure and light environment,the canopy structure of different mixed ratios of bamboo and multi-broad-leaved mixed forests are significantly different.The canopy structure of bamboo and broad-leaved mixed forest with a mixed ratio of 20%-30%is the best.With the increase of the mixing ratio,the leaf area index(LAI)and the leaf inclination(MLA)in bamboo and multi-broad-leaved mixed forests show a trend of first increasing and then decreasing.The LAI of bamboo and multi-broad-leaved mixed forests with a mixed ratio of 20%-30% is the largest.Among bamboo and single broad-leaved tree mixed forests,the forest canopy structure is greatly affected by the mixed tree species,the forest canopy structure of CAB is best.The canopy structure of bamboo and single broad-leaved tree mixed forests was significantly correlated with the understory light.The understory light radiation was significantly negatively correlated with the leaf area index,and the scattered radiation is significantly positively correlated with the average leaf angle.2.In the study of soil quality,the mixing ratio of bamboo and multiple broad-leaved trees mixed forests significantly affects the soil quality,the soil quality evaluation index were follow:20%-30%(0.3878)> 30%-40%(0.2236)>0-10%(0.0704)>40% or more(-0.0915)> 10%-20%(-0.5904).The soil properties of bamboo and multiple broad-leaved trees mixed forests with the mixed ratio of 20%-30% are significantly better than other forests.In bamboo and multiple broad-leaved trees mixed forests,the soil nutrient status in the forest with a mixing ratio of 20%-30% and 30%-40% is the best,and the soil enzyme activity and soil microbial biomass content are preferably in the forest with a mixed ratio of 20%-30%.In bamboo and single broad-leaved tree mixed forests,the soil nutrient content in the CAB forest is higher than other forests.The soil enzyme activity and soil microbial biomass in CAB and CCB stands is significantly higher than AFB;soil quality comprehensive evaluation ranking: CAB/10%-20% > CAB/0-10% >CAB/20%-40% > AFB/0-10% > CCB/20%-40% > AFB/10%-20% > CCB/0-10% > CCB/10%-20% > AFB/20%-40%.3.The mixing ratio and mixed tree species changed the soil micro-ecology.In bamboo and multiple broad-leaved trees mixed forest,the diversity of soil bacteria is the largest in bamboo and multiple broad-leaved trees mixed forests with a mixed ratio of 10%-20%,and gradually decreases with the deepening of the soil layer.The dominant bacteria such as Acidobacteria,Proteobacteria and Actinobacteria,and the highest relative abundance is in stands with a mixing ratio of 20%-30%.The mixing ratio can significantly change the relationship between the bacteria in bamboo and multiple broad-leaved trees mixed forest.The stability of the soil bacterial community is 30%-40%>0-10%>40% or more >20%-30%>10%-20%;the functional genes related to the metabolic pathways of soil bacteria are significantly different in different soil layers with the change of the mixing ratio.For the forest stand of 20%-30%,the bacteria have the strongest metabolic ability.In bamboo and single broad-leaved tree mixed forests,the influence of mixed broad-leaved tree species on the diversity of soil bacterial community is greater than that of its uniformity,the soil bacterial diversity presents a higher level in the CAB forests.At the phylum level,the main dominant bacteria are Acidobacteria,Proteobacteria and Actinobacteria in the CAB forest,the relative abundance of bacteria in CAB is relatively high.Mixed broad-leaved tree species significantly changed the relationship between soil bacteria in the forest,and compared with CAB and CCB,AFB significantly improves the stability of bacterial communities.The overall metabolic capacity of soil bacteria in different forests is :AFB>CAB>CCB.4.In bamboo and multiple broad-leaved trees mixed forest,the existing biomass,the existing biomass of bamboo whip,the annual productivity of fine roots,the existing litter and the annual litter amount of the forest show a normal distribution with the increase of the mixing ratio.They have the highest value among forest with a mixing ratio of 20%-30%,which are2522.85 kg/acre,791.18 kg/acre,79.73 kg/acre,202.73 kg/ acre,and 270.62 kg/ acre respectively.The results showed that the mixed ratio can promote the growth of bamboo in the forest under a certain range.In bamboo and single broad-leaved tree mixed forest,The existing biomass and productivity of Phyllostachys edulis in the forest are significantly different among different forest stands.Compared with AFB and CCB,CAB changed the biomass of various parts of Phyllostachys edulis in the forest,the productivity of fine roots,and the input and storage of litter in the forest.the Phyllostachys edulis in the CAB forest has the best productivity.5.The set pair analysis method was used to evaluate the quality of different types of bamboo and broad-leaved mixed forests.The results showed that in bamboo and multiple broad-leaved trees mixed forest,the quality of forest with a mixed ratio of 20%-30% was the best.The rank characteristic values of the different stands are ranked 20%-30%<30%-40%< 10%-20%<0-10%<40% or more.The interactive effect of the mixed tree species and the mixed ratio on the comprehensive quality of the stand is more significant in bamboo and single broad-leaved tree mixed forest.The result shows that the CAB forest with a mixed ratio of 20%-40% has the smallest stand-level characteristic value,therefore,the forest environment and potential productivity are the best.In summary,in the process of cultivating bamboo and broad-leaved mixed forests,it is possible to adjust the mixed ratio and select dominant associated tree species and other tending measures to improve the soil quality of the forest,increase the potential productivity of bamboo,and promote the sustainability of the forest.Our Studies have shown that the best proportion of broad-leaved trees in bamboo and multiple broad-leaved trees mixed forest is 20%-30%.For forest stands where bamboo and individual broad-leaved trees are mixed(with broad-leaved trees as the center,with a radius of 9m),it is recommended that the optimal tree species choose Choerospondias axillaris,and the mixed ratio within the forest under the control of the management process is within the range of 20%-40%.Secondly,the Alniphyllum fortune(Hemsl.)Makino is selected,and the optimal mixing ratio is 0-10%,and the optimal mixing ratio of Phyllostachys edulis and Castanopsis chinensis Hance mixed forest is 10%-20%. |
