Predicting potential suitable distribution areas for Juniperus przewalskii in Qinghai Province of northwestern China based on the optimized MaxEnt model

Objective This paper aims to predict the potential distribution area of Juniperus przewalskii in Qinghai Province of northwestern China, and to provide a theoretical basis for the management, protection and restoration of J. przewalskii.

Method The potential distribution of J. przewalskii in Qinghai Province was predicted by a variety of environmental variables (climate, topography, soil, ecosystem and human activity intensity) based on the MaxEnt model optimized by the Kuenm package of R, and the dominant environmental factors and value ranges affecting the geographical distribution of J. przewalskii were discussed, and the accuracy of the prediction results was verified by the project team from 2018 to 2020 in the field survey of J. przewalskii resources in Qinghai Province.

Result The predicted suitable areas of J. przewalskii were mainly distributed in the eastern, northeastern and northern Qinghai Province, with a suitable area of 32 000 km². From 2018 to 2020, sub-compartment for field investigations of J. przewalskii resources in Qinghai Province fell into the predicted suitable area, and the environmental conditions suitable for the growth of J. przewalskii, i.e. climate (max. temperature of the warmest month was 15−22 ℃, min. temperature of the coldest month was −23−15 ℃, annual mean precipitation was 300−600 mm, isothermality was < 39%, the variance of precipitation was 88 − 103), topography (elevation was 2 800−3 950 m, slope was 12°−18°, slope to sunny slope, semi-sunny slope and semi-shaded slope), soil (AWC range > 0.4 mm/m), topsoil gypsum < 0.2%), ecosystem type (farmland, forest land and grassland ecosystem). The human footprint index of J. przewalskii distribution area > 10.

Conclusion In this study, the optimized MaxEnt model can accurately reflect the distribution of potential suitable areas of J. przewalskii. The geographical distribution of J. przewalskii is the result of the comprehensive influence of topography, temperature, precipitation, ecosystem type, soil and human activities, and altitude is the dominant environmental factor affecting the distribution of J. przewalskii in Qinghai Province. The research results can provide a reliable theoretical basis and implementation direction for the selection of suitable space for afforestation in J. przewalskii, and at the same time, the results of the suitability classification of distribution area can provide a reference for the management and protection and restoration decisions of J. przewalskii.