Plant-soil Interaction Of Main Artificial Protective Forest In The Longzhong Loess Plateau

Plant-soil interaction mainly refers to the process in which plant growth changes the biological and abiotic properties of the soil in its growth environment,and the changed soil properties then react on plant growth.Its core is to reveal the interaction relationship between plants and soil biological and abiotic environments.Plant-soil interaction is widely used to explain plant aboveground underground relationships,population dynamics,community construction processes,and biodiversity maintenance.Artificial forests are an important component of forest ecosystems,playing an important role in wood production,carbon and oxygen fixation,soil and water conservation,wind and sand prevention,and biodiversity maintenance.The Longzhong Loess Plateau is a key area for the implementation of the national strategy for ecological protection and high-quality development in the Yellow River Basin,as well as a typical semi-arid ecological fragile area and a key area for soil erosion prevention and control.Since the 1960 s,the area has undergone large-scale artificial afforestation,especially the construction of soil and water conservation protective forests.The study of plant-soil interaction in artificial protective forests is crucial for evaluating the stability and functional quality of artificial protective forests,predicting the evolution direction of artificial forest ecosystems,and is of great significance for ecological restoration and sustainable development of forestry in ecologically fragile areas.In order to gain a deeper understanding of the plant-soil interaction relationship in the main artificial protective forests on the Longzhong Loess Plateau,this study focuses on four types of main artificial tree protective forests on the Loess Plateau: T.chinensis,P.hopeiensis,P.tabuliformis and P.sibirica,as well as C.korshinskii shrub protective forests with different afforestation years(13,35,55 years).Through field investigation,sampling,and indoor testing analysis,the aim is to clarify the effects of different types of artificial tree forests and different ages of caragana shrub forests on soil physicochemical properties and soil quality,and to reveal the relationship between changes in soil properties and the functional characteristics of roots and leaves of artificial protective forests.Finally,based on the changes in soil microbial community characteristics of artificial tree forests,the mechanism of plant soil interaction in artificial protective forests is explored.The main research findings are as follows:(1)The impacts of four artificial arbor forests types on soil physical properties(soil texture,bulk density,moisture content,p H)were ranked as follows: P.hopeiensis > P.tabuliformis > P.sibirica > T.chinensis.The content of soil total carbon and organic carbon decreased in the following order: P.hopeiensis > P.tabuliformis > P.sibirica > T.chinensis.The content of soil total nitrogen and available nitrogen decreased in the following order: P.hopeiensis > P.sibirica > P.tabuliformis > T.chinensis.The content of soil total phosphorus decreased in the following order: P.tabuliformis > P.sibirica > P.hopeiensis > T.chinensis.The content of soil available phosphorus decreased in the following order: P.tabuliformis > T.chinensis > P.sibirica > P.hopeiensis.With the increase of afforestation years,the content of clay and powder particles in the soil under the artificial C.korshinskii shrub forest significantly increased,while the content of sand particles significantly decreased.The soil bulk density and p H gradually decreased.The total carbon content,organic carbon content,total nitrogen content,total phosphorus content,and available phosphorus content of the soil all showed a decreasing trend with the increase of afforestation years,while the available nitrogen showing a first decreasing and then increasing trend.At the same time,the soil quality index of artificial arbor forest ranged from 0.56 to 1.46,and the soil quality index range of P.hopeiensis > P.tabuliformis > P.sibirica > T.chinensis,while the soil quality index range of artificial shrub C.korshinskii was 0.60-2.40,showing a significant increase with increasing afforestation years.The longer the afforestation years,the more obvious the improvement of soil quality.(2)There was a positive correlation between soil organic carbon content,total nitrogen content,total phosphorus content,total porosity and leaf carbon content,dry matter quality,average leaf area,fine root carbon content,and specific root length in four types of artificial arbor forests.There was a positive correlation between soil bulk density and fine root nitrogen content,fine root phosphorus content,and fine root dry matter quality.Additionally,there was a positive correlation between soil total porosity and fine root carbon content and specific root length;There was a positive correlation between soil nutrients and leaf phosphorus content,leaf dry matter content,fine root carbon content,fine root nitrogen content,and fine root dry matter quality in artificial C.korshinskii shrub forests.Soil bulk density was also positively correlated with leaf nitrogen content,leaf phosphorus content,specific leaf area,average leaf area,specific root length,and fine root phosphorus content,while it was negatively correlated with fine root nitrogen content and fine root carbon content.Soil organic carbon,soil nitrogen content,and phosphorus content were the main factors affecting the functional traits of T.chinensis,P.hopeiensis,P.tabuliformis and P.sibirica,while C.korshinskii leaves were less affected by soil nutrient content;The fine root functional traits were mainly influenced by soil bulk density and soil porosity,but the influence of soil bulk density and soil porosity on the fine root functional traits of C.korshinskii was smaller than that of artificial tree protection forest species.(3)A total of 33 bacterial phyla were detected in the soil of four artificial arbor forests,with Actinobacteria,Proteobacteria,Acidobacteria,Chloroflexi,and Gemmatimonadetes as the dominant phyla,accounting for 84.31-88.41% of the bacterial community’s relative abundance.There were significant differences in soil bacterial diversity and community composition among different tree species.Soil bacterial communities were mainly regulated by deterministic heterogeneous selection,and soil enzyme activity,salinity,and organic matter content are the main environmental factors affecting bacterial communities.The co-occurrence network analysis found that the negative correlation connection number among soil bacterial species in the four artificial tree protection forests was higher than the positive correlation connection number,indicating that the species in the soil bacterial community showed asynchronous and complementary adaptive responses to the heterogeneity of soil in different tree forests.Based on the multiple topological properties of the co-occurrence network,it was found that the complexity of the co-occurrence network structure was in the order of P.tabuliformis > T.chinensis > P.hopeiensis > P.sibirica,indicating that the soil bacterial community of P.tabuliformis artificial forest in the Longzhong Loess Plateau was more stable,which was more conducive to promoting the feedback cycle between vegetation,soil bacteria,and soil fertility in the region.(4)A total of 6 fungal phyla were detected in the soil of 4 artificial arbor forests,with Basidiomycota,Ascomycota,and Mucor mycotina as the dominant groups,accounting for 85.56-92.26% of the fungal community’s relative abundance.The diversity and community composition of soil fungi also showed significant differences among different artificial forest species.Unlike bacterial communities,stochastic processes mainly drive the construction of soil fungal communities,and the role of deterministic processes was relatively weak.The co-occurrence network analysis found that the negative correlation connections between soil fungal species in the four tree forests were also higher than the positive correlation.Based on the topological characteristics of the network structure,it was found that the complexity and stability of the network were in the order of T.chinensis > P.hopeiensis > P.sibirica > P.tabuliformis,indicating that T.chinensis artificial forest in the Longzhong Loess Plateau was superior to the other three tree species in stabilizing soil fungal communities and enhancing the mutual feedback between vegetation,soil fungi,and soil fertility.In summary,there were significant differences in soil fertility among different types of artificial arbor forests,and as the afforestation years increase,the artificial C.korshinskii shrub forest has a stronger effect on improving soil quality.Soil fertility can also reverse affect the leaf and root functional characteristics of artificial protective forests.The physical and chemical characteristics and fertility of artificial protective forest soil are the main factors affecting the structure of microbial communities,The P.tabuliformis plantation can form a more stable soil bacterial and microbial community,while T.chinensis plantation can form a more stable soil fungal community.The above research results not only deepen the understanding of the plant soil interaction mechanism of the main artificial protective forests in the Loess Plateau,but also provide important technological support for the construction and management of artificial protective forests in the region.