Objective This paper aims to analyze the current and future potential distributions of four common tree species (Pinus sylvestris, Pinus tabuliformis, Caragana korshinskii and Larix gmelinii var. principis-rupprechtii) in the Loess Plateau region of northern China, and to reveal the effects of climate change on spatial distribution patterns of plants.
Method Four dominant species on the Loess Plateau were studied based on 19 climate factors and 5 indicators from Holdridge life zone model and Kira index system: bio-temperature (ABT), potential evapotranspiration rate (PER), warmth index (WI), coldness index (CI) and humidity index (HI). The Maxent model was used to predict the potential geographical distribution of the four tree species under current and future scenarios (2041−2060, 2061−2080) SSP126, SSP245 and SSP585. The Jackknife method was used to analyze the main environmental factors affecting its distribution, and the predicted results were tested by the area under receiver operating characteristic curve (AUC).
Result (1) Maxent model can well simulate the potential geographical distribution range of major established species in the Loess Plateau, and the average AUC of each species was greater than 0.8. (2) For Pinus sylvestris, Pinus tabuliformis and Caragana korshinskii, both temperature and precipitation limited their distribution, while for Larix gmelinii var. principis-rupprechtii, precipitation was the main factor affecting their distribution. Temperature seasonality, potential evapotranspiration rate, precipitation of the driest month and precipitation of the wettest quarter were the main environmental factors affecting the distribution of Pinus sylvestris. Temperature annual range, temperature seasonality, minimum temperature of the coldest month, precipitation of the warmest quarter and potential evapotranspiration rate were the main factors affecting the distribution of Pinus tabuliformis. The main factors affecting the distribution of Caragana korshinskii are maximum temperature of the warmest month, warmth index, isotherm, potential evapotranspiration rate and precipitation of the coldest season. The main factors affecting the distribution of Larix gmelinii var. principis-rupprechtii were mainly related to precipitation, which were precipitation of the wettest month, precipitation of the wettest quarter, variation coefficient of precipitation, and potential evapotranspiration rate. (3) The potential suitable areas of Pinus tabuliformis, Caragana korshinskii and Larix gmelinii var. principis-rupprechtii will migrate to the northwest, while that of Pinus sylvestris will migrate to the southwest. The potential suitable areas of Pinus tabuliformis and Larix gmelinii var. principis-rupprechtii showed a trend of expanding first and then decreasing, while the potential suitable areas of Caragana korshinskii and Pinus sylvestris would continue to expand, especially the proportion of highly suitable areas of Pinus sylvestris would expand to 50.97% in 2070s.
Conclusion Climate change will deprive Pinus tabuliformis and Larix gmelinii var. principis-rupprechtii of some of their highly suitable areas, but at the same time, the highly suitable areas of Caragana korshinskii and Pinus sylvestris will expand significantly. Caragana korshinskii and Pinus sylvestris are preferred in the project of converting farmland to forest land on the Loess Plateau.