油松飞播林土壤有机碳密度的影响因素

Factors affecting soil organic carbon density of Pinus tabuliformis aerial seeding plantation.

森林土壤碳库是森林生态系统碳库的重要组成部分,对于调节陆地生态系统碳循环和大气CO_(2)浓度变化起着非常重要的作用。以往的研究主要探究了各种因素(如地形、植被、土壤理化性质等)与森林土壤碳之间的单因子或多因子关系。然而,对于多因子中的关键因子识别及其相互作用机制尚不清楚。本研究利用陕西省商洛市丹凤县50块油松(Pinus tabuliformis)飞播林标准地调查数据,采用结构方程模型探究土壤有机碳密度的影响因素。选取了林分结构、物种多样性、生物量、土壤理化性质等方面的23个指标作为观测指标,形成乔木特征,林下灌、草及凋落物特征,其他土壤理化性质和土壤有机碳密度4个潜变量,构建偏最小二乘法的结构方程模型。结果表明:(1)最终的结构方程模型筛选出12个观测变量,其他土壤理化性质中筛选出3个观测变量,分别为土壤全氮、土壤全磷、土壤含水量;林下灌、草及凋落物特征潜变量中筛选出5个观测变量,分别为灌木Simpson指数、草本Simpson指数、草本Margalef指数、草本生物量、凋落物层厚度;乔木特征潜变量中筛选出3个观测变量,分别为乔木Simpson指数、林分大小比数、乔木物种数。(2)其他土壤理化性质是土壤有机碳密度的直接影响因素(路径系数为0.877,P<0.01),林下灌、草及凋落物特征与乔木特征是土壤有机碳密度的间接影响因素(路径系数分别为0.552和-0.299,均P<0.01)。(3)林下灌、草及凋落物特征通过直接影响其他土壤理化性质(路径系数为0.630,P<0.01)进而影响土壤有机碳密度,乔木特征通过直接影响林下灌、草及凋落物特征(路径系数为-0.541,P<0.01)进而影响土壤有机碳密度。本研究为揭示不同驱动因素之间的关系提供了新的见解,对于理解飞播林土壤有机碳调节有重要意义。

Soil carbon pool is an important component of forest ecosystem carbon pool,which plays an important role in regulating carbon cycling of terrestrial ecosystems and atmospheric CO_(2) concentration.Previous studies mainly investigated the relationships between forest soil carbon and various factors(such as topography,vegetation,soil physical and chemical properties).However,key factors in the multiple factors and their interaction mechanisms are still unclear.Based on the observed data of 50 plots of Pinus tabuliformis aerial seeding plantation in Danfeng County,Shangluo City,Shaanxi Province,we used structural equation model to explore the influencing factors of soil organic carbon density.A total of 23 indices including stand structure,species diversity,biomass and soil physicochemical properties were selected as observation variables,and four latent variables including tree characteristics,shrub,herb and litter characteristics,other soil physicochemical properties,and soil organic carbon density were formed.A partial least square structural equation model was constructed.The results showed that:(1)12 observation variables were included in the final structural equation model.Three observation variables were screened out from other soil physicochemical properties,namely,soil total nitrogen,soil total phosphorus,and soil water content.Five observation variables were selected from the latent variables of shrub,herb and litter characteristics,including shrub Simpson index,herb Simpson index,herb Margalef index,herb biomass,and litter layer thickness.Three observation variables were screened out from the latent variables of tree characteristics,including tree Simpson index,neighborhood comparison and number of tree species.(2)Other soil physicochemical properties were the direct influencing factors of the latent variable of soil organic carbon density(path coefficient of 0.877,P<0.01).Shrub,herb,and litter characteristics and tree characteristics were considered as the indirect influencing factors of the latent variable of soil organic carbon density(path coefficient of 0.552 and-0.299 respectively,both P<0.01).(3)The characteristics of shrub,herb,and litter affected the latent variable of soil organic carbon density by directly affecting other soil physicochemical properties(path coefficient of 0.630,P<0.01),and tree characteristics affected the latent variable of soil organic carbon density by directly affecting shrub,herb,and litter characteristics(path coefficient of-0.541,P<0.01).In conclusion,this study provides new insights into the relationship between different driving factors and has important implications for understanding soil organic carbon regulation in aerial seeding plantations.