The Integrated Stand Growth Model of Pure Pinus massoniana Forest based on Climate Change Scenarios

Based on field data of Pinus massoniana sample plots from the Tropical Forestry Research Center of Guangxi, a climate-sensitive integrated stand growth model was established by incorporating the effects of climate change. The dataset was split into two subsets: 80% for model fitting and 20% for validation. Model parameters were estimated using the nonlinear seemingly unrelated regression method. Furthermore, the BCC–CSM2–MR climate model and four future climate scenarios (SSP126, SSP245, SSP370, and SSP585) were adopted to predict the dynamics of mean dominant tree height, stand basal area per hectare, and stand volume per hectare of Pinus massoniana stands. The results revealed that the climate-sensitive integrated stand growth model outperformed the traditional version in simulation performance. Mean annual precipitation was the sole key factor positively correlated with the mean dominant tree height of stands, while mean annual temperature was the only significant factor negatively affecting stand basal area per hectare. In addition, rising temperatures intensified stand self-thinning and reduced the number of trees per hectare. Projections from China’s BCC–CSM2–MR climate model indicate that both future mean annual precipitation and temperature will be higher than those under the baseline normal climate (NC) scenario. Increased precipitation facilitates the growth of mean dominant tree height, whereas rising temperatures restrain the growth of stand basal area. Higher precipitation boosts height growth of dominant trees, while increasing temperature significantly inhibits the increment of stand basal area and volume; such inhibitory effects become stronger under higher-emission scenarios. Among the four climate scenarios, SSP585 predicts the highest mean annual temperature and precipitation.