| Coniferous and broadleaved forests are the two most important forest types in northern China.Pinus tabuliformis and Populus davidiana are respectively dominant tree species of coniferous and broadleaved forests,playing roles in environmental greening and soil conservation,with high ecological and economic values.Therefore,they are often used as the main forest species in the Grain-for-Green program,making great contributions to afforestation and ecological protection.However,the excessively focus on planting areas has resulted in overly dense and structurally homogeneous for the vegetation ecosystems,leading to low-yield and low-efficiency forests.Understanding the relationship between different types of forest distribution and the ecological environment is a new focus for afforestation and ecological protection.This paper aimed at the problems of vegetation structure and survival rate in the Grain-for-Green program by combining ecological and statistical theory,using Max Ent models to predict the potential suitable habitats of coniferous and broadleaved forests in Shanxi Province based on sample data environmental data from four aspects:climate,terrain,soil,and socio-economy with a spatial resolution of 90 m.The previously published thresholds of soil organic carbon(SOC)contents as a prior knowledge were used to screen sample points of P.tabuliformis and P.davidiana;and we applied the Max Ent model to predict their marginal probability of potential suitable habitat.The main environmental variables that affected coniferous forests,broadleaved forests,P.tabuliformis and P.davidiana were selected by geographic detectors,and the relationship between the main environmental variables and the potential suitable probability was explored.The main research results are as follows:1.The habitat suitability prediction results for coniferous and broadleaved forest was reliable.The main environment variables that influences the potential suitable habitat for coniferous forests is temperature seasonality(BIO4),population density(PD),topsoil calcium carbonate(CACO3),slope(SLOPE),aspect(ASPECT)and maximum temperature of warmest month(BIO5).The maximum temperature of warmest month combined with other environmental variables can greatly improve the suitability of coniferous forests.The habitat suitability conditions for coniferous forests were as follows:temperature seasonality range of952-1027,slope>43°,topsoil calcium carbonate is 3 wt.%(weight percent),aspect is north,and maximum temperature of warmest month<21℃.The main environment variables that influences the potential suitable habitat for broadleaved forests is temperature annual range(BIO7),topsoil sand fraction(SAND),population density(PD),topsoil calcium carbonate(CACO3),Coefficient of variation of precipitation seasonality(BIO15),solar radiation(SRAD).The topsoil sand fraction with other environmental variables can greatly improve the suitability of broadleaved forests.The habitat suitability conditions for broadleaved forests were as follows:The temperature annual range<35.9℃,topsoil sand fraction is 41 wt.%,topsoil calcium carbonate is 9 wt.%,precipitation seasonality range of 106-111.5,solar radiation range of 14710-15443 W/m~2.2.Compared to broadleaved forests,the suitable habitat area of coniferous forests was larger and more suitable areas were distributed further north.However,the distribution of suitable areas in broad-leaved forests was more concentrated.The suitable areas for coniferous forests were mainly concentrated in the Lvliang Mountains on the west bank of the Fen River and Mount Taiyue on the western side of the Taihang Mountains.They also extended towards the western side of the Lvliang Mountains and the northeast of Mount Taiyue,resulting in scattered distribution in the northern part of Shanxi province.Broadleaved forests were mainly distributed in the central region of Lvliang Mountains on the west bank of the Fen River,and in the triangular region formed by the Fen River,Qinhe River,Shuishi River,and the southern boundary of Shanxi province.They also extended towards the eastern side of the Lvliang Mountains and the western side of the triangular area.3.The prediction accuracy of habitat suitability for P.tabuliformis and P.davidiana were high,and indicating the prediction results of the model had a high level of confidence.These results indicated that a high-precision habitat suitability model for P.tabuliformis and P.davidiana can be constructed by selecting typical sample points with prior knowledge.According to the model results,the temperature annual range(BIO7)and population density(PD)had the greatest influence on the suitability of P.tabuliformis.The habitat suitability conditions for P.tabuliformis were as follows:The temperature annual range of 35.4-39.7℃,topsoil calcium carbonate of 3 wt.%,topsoil clay fraction range of 48 wt.%,precipitation of warmest quarter range of 308-366 mm,precipitation of driest quarter range of 12.8-17.0 mm.The temperature annual range(BIO7)had the greatest influence on the suitability of P.davidiana.The interaction between temperature annual range and topsoil sand fraction had the greatest influence on the suitability of P.davidiana.The habitat suitability conditions for P.davidiana were as follows:The temperature annual range of 33.2-35.7℃,topsoil calcium carbonate of 3 wt.%,topsoil clay fraction range of 48 wt.%,precipitation of wettest period range of 120-134 mm,topsoil sand fraction is 45 wt.%,topsoil gravel content range of 5-6vol%,topsoil clay fraction is 22 wt.%.This study revealed the distribution patterns and differences in the suitable areas of coniferous and broadleaved and forests in Shanxi Province,and the environmental conditions of high suitable distribution were identified.It provides support for a comprehensive and accurate understanding of the detailed distribution differences and habitat characteristics of different species in the large-scale regions with complex ecological environments.Furthermore,it is proved that the high-precision habitat suitability model of dominant tree species of P.tabuliformis and P.davidiana can be established by selecting typical sample points with prior knowledge,to provide a theoretical basis for the detailed planning of forest management and afforestation programs in Shanxi Province and other regions.As research in ecology and related disciplines deepens,much prior knowledge about a wide variety of species can now be found,including those with small distributions and rare species.This paper suggests that incorporating diverse forms of prior knowledge into species distribution models in future studies can not only reduce research costs and save time,but also yield biologically more meaningful predictive results,thereby significantly enhancing our understanding of species distribution patterns. |
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