Larix principis-rupprechtii Mayr (larch) is a native conifer species in North China, and also a major silvicultural and timber species in the region. Climate change has led to a change in its suitable distribution area. However, the dominant factors affecting changes in its suitable distribution and migration trends are not clear. In this study, based on forest resource inventory data and bioclimatic data in Hebei and Shanxi provinces, China, we built an ensemble model based on seven algorithms to simulate the larch’s potential suitable distribution areas under three shared socioeconomic pathways (SSPs: SSP1-2.6, SSP2-4.5, and SSP5-8.5) for the current and future (2021–2040, 2041–2060 and 2080–2100). The results revealed that: (1) ensemble models significantly improved the predictive accuracy (ROC = 0.95, TSS = 0.81, KAPPA = 0.65); (2) the current potentially suitable distribution area was concentrated in the Bashang Plateau and the northwestern mountain range of the study area. Among them, 12.38% were highly suitable distribution areas, 12.67% were moderately suitable distribution areas, and 12.01% were lowly suitable distribution areas; (3) the main climatic factors affecting larch distribution were mean temperature of driest quarter, mean diurnal range, precipitation of warmest quarter, and temperature annual range; (4) under different future climate scenarios, the contraction of the suitable distribution area of larch increased significantly with increasing SSP radiation intensity. By 2100, the suitable distribution area of larch was expected to decrease by 26.5% under SSP1-2.6, 57.9% under SSP2-4.5, and 75.7% under SSP5-8.5 scenarios; (5) from 2021 to 2100, the different suitable distribution areas of larch showed a trend of migration to the northeast. Under the SSP5-8.5 scenario, the migration distance of different suitable distribution areas was the largest, in which the high suitable distribution area migrated 232.60 km, the middle suitable distribution area migrated 206.75 km, and the low suitable distribution area migrated 163.43 km. The results revealed the impact of climate change on the larch distribution, which provided a scientific basis for making forest management decisions.

Larix principis-rupprechtii Mayr (larch) is one of the main afforestation and timber production species used in North China. Climate change has led to a change in its suitable distribution and growth. However, the impact of climate change on its growth suitability is not clear. In this study, using forest resource inventory data and spatially continuous environmental factor data (temperature, precipitation, topography, and soil) in Hebei and Shanxi Provinces, China, the random forest model (RF) was used to simulate the larch site index (SI) and growth suitability under three shared socioeconomic pathways (SSPs: SSP1-2.6, SSP2-4.5, and SSP5-8.5) for the current and future (2021–2040, 2041–2060 and 2080–2100). The results revealed that (1) RF had excellent performance in predicting the regional SI (R2 = 0.73, MAE = 0.93 m, RMSE = 1.35 m); (2) the main factors affecting the productivity of larch were the mean temperature of the warmest quarter (BIO10), elevation (ELEV), mean diurnal range (BIO2), and annual precipitation (BIO12); and (3) larch currently had a higher SI in the Bashang areas and in the high-altitude mountains. The areas characterized as unsuitable, poorly suitable, moderately suitable, and highly suitable accounted for 15.45%, 42.12%, 31.94%, and 10.49% of the total area, respectively. (4) Future climate warming had an obvious inhibitory effect on the SI, and the effect strengthened with increasing radiation intensity and year. (5) The moderately suitable and highly suitable areas of larch growth showed a downward trend under future climate scenarios. By the end of this century, the suitable growth areas would decrease by 14.14% under SSP1-2.6, 15.17% under SSP2-4.5, and 19.35% under SSP5-8.5. The results revealed the impact of climate change on larch growth suitability, which can provide a scientific basis for larch forest management.

Larch (Larix principis-rupprechtii Mayr) is a major coniferous tree species in northern China, and climate change has serious impacts on larch growth. However, the impact of future climate change on net primary productivity (NPP) and the growth suitability of larch is unclear. Based on forest inventory data, spatially continuous environmental factor data (climate, topography, soil), and NPP from the Carnegie-Ames-Stanford approach (CASA) model in the study area, the random forest (RF) model was used to simulate the potential NPP and growth suitability of larch under different shared socioeconomic pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5) for current and future (2041–2060, 2080–2100). The correlation between potential NPP and determinants under different climate scenarios was analyzed at the pixel scale. The results showed that: (1) RF showed excellent performance in predicting the potential NPP of the region (R2 = 0.80, MAE = 15.61 gC·m−2·a−1, RMSE = 29.68 gC·m−2·a−1). (2) Under current climatic conditions, the mean potential NPP of larch was 324.9 gC·m−2·a−1. Low growth suitability of larch occurred in most parts of the study area, and high growth suitability only existed in the Bashang area and the high-elevation mountains. (3) The total area of high and medium growth suitable areas were projected to be 76.0%, 66.7%, 78.2%, and 80.8% by the end of this century under the SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 climate scenarios, respectively. (4) Under the SSP1-2.6 and SSP2-4.5 climate scenarios, the temperature had a significant contribution to the accumulation of the larch’s NPP, whereas precipitation had less effect on the larch’s growth. The results provided a theoretical basis for the adaptive management of larch forests under global climate change.