| China is the country with the largest existing area of plantation in the world,but how to improve the sustainability and stability of forest ecosystem is the main problem in the construction of plantation.Mixed forestry can effectively protect the surface structure,improve the site conditions,enhance the ability of stand to defend against natural disasters,protect biodiversity and improve the restoration of degraded areas.It is considered to be the most appropriate planting method to provide environmental services and product supply.Biomass is the energy basis and nutrient source for the operation of the whole ecosystem,and it is an important index to judge whether the forest ecosystem is high-quality or not.Therefore,through the study of the biomass difference between mixed forest and pure forest in forest ecosystem,it is of great significance to explore the management of forest production and the response mechanism to climate change in the future.In recent years,many studies have been carried out on the biomass difference between mixed forests and pure forests in China,but these studies are mainly based on field investigation,which has spatial scale limitations.The meta-analysis method can not only clarify the spatial characteristics of biomass differences between mixed forests and pure forests in China,but also clarify the driving factors of biomass differences.Therefore,this study collected 156 articles on related topics published in recent years for meta-analysis,defined the difference characteristics of biomass between mixed forests and pure forests in China,clarified the influencing factors of stand biomass difference,and discussed the confusion effect between various influencing factors.The research results provide reliable data support and theoretical basis for the operation and management of plantation.The main results of this study are as follows:(1)The biomass of each component of mixed forests was significantly higher than that of pure forests.Among them,the total biomass of mixed forests increased significantly by 21%,the biomass of tree layer increased significantly by 31%,the biomass of shrub layer increased significantly by 130%,the biomass of herb layer increased significantly by 45%,and the biomass of litter layer increased significantly by 55%.In the organs of tree layer,the biomass of leaves,branches,stems and roots increased significantly by 62%,59%,37% and 28% respectively.(2)Dry and wet area is the most important driving factor for all biomass changes,followed by stand density and temperature band.In the difference of biomass between mixed forests and pure forests,the order of importance of influencing factors of total biomass,tree layer biomass,herb layer biomass and litter layer biomass is mainly dry and wet area > stand density > temperature zone;For shrub layer biomass,the order of importance of influencing factors is dry and wet area > temperature zone > stand density.(3)Compared with pure forests,the closer to the tropical area,the more the total biomass of mixed forests increased;The total biomass of mixed forests in humid area increased more than that in semi-humid area;The mixed forests with nitrogen fixing species can obtain higher total biomass than the mixed forests without nitrogen fixing species.In addition,the mixed planting effect of coniferous forest and broadleaved forest is better than that of coniferous forest and coniferous forest,broadleaved forest and broad-leaved forest;The effect of increasing total forest biomass was the best under the mixed condition of young and middle age;When the mixed proportion was 6:4,the total biomass and shrub biomass of the mixed forests increased the most;From low stand density to high stand density,the total biomass of mixed forests increased first and then decreased;No human disturbance produces higher total forest biomass than human disturbance.(4)There are confounding effects among mixed leaf types,temperature zones and dry and wet areas.Compared with pure forests,the total biomass and tree layer biomass of coniferous and broad-leaved mixed forests in semi-humid area increased the most,increased by 32.89% and 45.76%,respectively;Compared with the pure forests,the biomass of shrub layer and herb layer of coniferous and broad-leaved mixed forests in humid area increased the most,increased by 169.92% and 84.81%,respectively;Compared with the pure forests,the litter layer biomass of broad-leaved and broad-leaved mixed forests in humid area increased the most,significantly increased by 131.52%. |
