气候变化对落叶松人工林生物量生长的影响模拟

Modelling the effects of climate change on stand biomass growth of larch plantations

【目的】研究气候变化对落叶松人工林生物量及其生长的影响,为落叶松人工林碳估测和适应性经营决策提供依据。【方法】利用华北和东北地区第6~8次森林资源连续清查落叶松人工纯林固定样地数据,基于理论生长方程建立林分生物量生长模型。并将不同种落叶松作为哑变量,建立了气候敏感的林分生物量生长模型,气候因子为年湿热指数(AHM)。模拟未来气候不变、两种温室气体代表性浓度路径(RCPs)(包括RCP 4.5和RCP 8.5)3种气候变化情景下的林分生物量及其连年生长量,采用两种RCP气候情景与当前情景生物量估计结果的相对差值量化气候变化对林分生物量及其生长的影响。【结果】林分生物量的基础模型、含哑变量的模型、含气候变量和哑变量生长模型的决定系数R 2分别为0.9382、0.9470和0.9507,采用哑变量和考虑气候因子能够明显改善模型表现。模型模拟结果表明,与当前情景比较,各树种的林分生物量及其连年生长量在RCP 4.5和RCP 8.5气候变化情景下既有增加也有减少的趋势。对于林分生物量,RCP 4.5和RCP 8.5情景下的相对差值的均值区间分别为-3.02%~2.69%和-4.72%~3.41%;对于林分生物量连年生长量,RCP 4.5和RCP 8.5情景下的相对差值的均值区间分别为-1.92%~0.30%和-2.66%~0.72%。【结论】建立的林分生物量生长模型可用于模拟气候变化下落叶松人工林的林分生物量生长过程。在气候变化的背景下,不同种落叶松人工林生物量及其生长量既有增加也有减少。未来气候变化对不同种的林分生物量及生长量的影响存在差异。总体来看,2011—2060年气候变化对华北落叶松和日本落叶松林分生物量的影响为正,其余树种为负;对华北落叶松的林分生物量连年生长量的影响为正,其余为负。

【Objective】This study aimed to understand the effects of climate change on the stand biomass and growth in larch(Larix spp.)plantations to provide a basis for estimating carbon storage and employing adaptive management decision⁃making.【Method】Sample plot data of pure larch plantations from the 6th to 8th National Forest Inventories in northern and northeastern China were used to develop stand biomass growth models based on theoretical growth equations.Taking the tree species as a dummy variable,a climate⁃sensitive stand biomass growth model was developed with the inclusion of the annual heat⁃moisture index(AHM).The stand biomass and annual increment under three climate change scenarios,including a constant climate and two greenhouse gas representative concentration paths(RCPs)(RCP 4.5,RCP 8.5),were simulated using the model.The relative differences between the estimated results under two RCP climate scenarios and the current scenario were calculated to quantify the effects of climate change on the stand biomass and annual increment.【Result】The R 2 values of the basic stand biomass growth model,model with dummy variables,and model with dummy and climate variables were 0.9382,0.9470,and 0.9507,respectively.Dummy variables and climatic factors improved the performances of the models.Compared with the current scenario,both increasing and decreasing trends were found for the stand biomass and annual increment of each tree species under RCP 4.5 and RCP 8􀆰5.For stand biomass,the ranges of the mean values of relative differences under RCP 4.5 and RCP 8.5 scenarios were from-3.02%and-4.72%to 2.69%and 3.41%,respectively.For the annual increment of stand biomass,the ranges of the mean values of relative differences under RCP 4.5 and RCP 8.5 scenarios were from-1.92%and-2.66%to 0􀆰30%and 0.72%,respectively.【Conclusion】The stand biomass growth model established in this study can be used to simulate the stand biomass growth in pure larch plantations under climate change conditions.There were both increasing and decreasing trends for the stand biomass and annual increments of larch plantations with future climate change in different tree species.The direction and magnitude of the impacts of future climate change on the stand biomass and annual increments differed among tree species.Generally,positive effects on the stand biomass were found for Larix principis⁃rupprechtii and L.kaempferi,but negative effects were found for other tree species;and negative effects on the stand biomass annual increment were found for all tree species with the exception of L.principis⁃rupprechtii.