Temperate Forest Distribution Pattern And Influencing Factors Of Carbon Sink In North China

As one of the most important terrestrial ecosystem types,forest has important ecosystem functions.In recent years,due to climate change and the interference of human activities,temperate forests in North China have faced many threats such as biodiversity loss.At the same time,the significant precipitation and temperature gradient have made the region a variety of forest types.Exploring the influencing factors of forest type distribution and carbon storage in this region will help to further understand the function and community assembly of temperate forests,and also provide basic data for the protection and conservation of temperate forests.This study relied on quadrat data obtained from field investigation.The spatial distribution pattern and its influencing factors of temperate forests in North China were studied by using variance analysis and variation partition method.Seven Alliance Groups of Populus Forest Alliance Group,Robinia Forest Alliance Group,Pinus Forest Alliance Group,Platycladus Forest Alliance Group,Quercus Forest Alliance Group,Larix Forest Alliance Group and Betula Forest Alliance Group were used as study objects.Using 1,986 forest plots as research objects,the influencing factors and mechanism of carbon storage in each forest layer were expounded.Spatial interpolation analysis was conducted to explore the spatial distribution of above-ground carbon stocks and biodiversity.The generalized least square model and structural equation model were used to explore the relationship between above-ground carbon stocks of each forest layer with biodiversity,plant functional traits,stand structure,climate and topography.The effects of soil physicochemical properties,topographic factors,stand density,above-ground biomass and biodiversity on soil organic carbon content were studied using regression analysis and random forest analysis,and the influencing factors of soil organic carbon content were revealed.The main conclusions are as follows:(1)The spatial distribution of different forest communities showed significant regional characteristics.Pinus forests and Quercus forests were more widely distributed in Shandong,Henan,Hebei,Shanxi,etc.The Betula forests were mainly distributed in Shanxi province,and the Robinia forests were mainly distributed in the relatively warm and humid Shandong province.The response of different communities to environmental factors is also different.The community distribution of Platycladus and Robinia forest was most affected by environmental factors with interpretation rates of 40%and 39%,which was mainly driven by spatial distance,followed by topographic factors and climate factors.Topographic factors had the greatest influence on Robinia forest and Platycladus forest,while the climate factors had little effect on forest community distribution.(2)The aboveground carbon stocks in the overstory and understory of temperate forests are determined by different factors.The overstory was mainly affected by mass ratio effect,while the understory was mainly driven by niche complementary effect.In overstory,the forest with high tree-size dimension inequality and high dominant tree height had larger above-ground carbon stocks.Therefore,the mass ratio effect and the complexity of stand structure were the main ecological mechanisms affecting carbon stocks.In the understory,species diversity and overstory properties were the main factors affecting carbon storage.Tree height and aboveground carbon storage of the overstory decreased aboveground carbon storage of the understory.Overstory diversity had a positive effect on understory diversity,and thus affected above-ground carbon storage of understory.In consequence,overstory attributes and niche complementation were the main ecological mechanisms in the understory.The overstory affected the understory through resource quantity and resource heterogeneity.(3)Soil physicochemical properties,vegetation and altitude affected soil organic carbon,and had an obvious interaction with above-ground carbon storage.Soil N and soil organic carbon showed a significant positive correlation,and soil organic carbon decreased with the increase of pH,while soil organic carbon content increased first and then decreased with the increase of soil P.Tree diversity and aboveground biomass increased soil organic carbon.Soil organic carbon increased with the increase of tree DBH,but too large DBH decreased soil organic carbon.Soil organic carbon was positively correlated with elevation,but not significantly correlated with slope direction and slope.In conclusion,this study further elucidates the interaction between the above-ground carbon storage of forest layers and the soil organic carbon content.It provides important data support and theoretical foundation for understanding the formation and development of temperate forests in this region,and also provides scientific guidance for forest protection,management and precise improvement of forest quality in China.