基于AVIM-CHM模型对黄土高原退耕还林区植被动态模拟及预估

Since the implementation of Grain for Green Project in 2000, the vegetation coverage in Loess Plateau has been improving significantly, but at the same time, the soil drying gets more severe. Thus, the survival of the artificially planted trees and shrubs has been called into question. However, few works were conducted to study the vegetation dynamic in the Loess Plateau under climate change background. Moreover, the land surface-ecology-hydrology model which is applicable to the Loess Plateau is lacking, and the current models do not describe the groundwater-vegetation interaction very well, which limits the simulation of dynamic vegetation processes. In this study, we will firstly select the classic area for Loess Plateau’s Grain for Green Project. Secondly, improve the former developed AVIM-CHM coupled mode, which can effectively simulate the groundwater–vegetation interaction, and carry out the model’s calibration and validation in study area. Lastly, forecast the vegetation’s change characteristics and space-time structure, as well as the soil water variation trend, and analyze the relationship between climate-hydrology factors and vegetation growth, then reveal whether or not the artificially planted trees and shrubs can survive over long time. The investigations can provide scientific basis for the further implementation of the “adapting to climate change Grain for Green policy in Loess Plateau”, and also benefit for the vegetation-hydrology-land- atmosphere coupling research.

黄土高原自2000年正式实施退耕还林以来，植被覆盖明显改善，但土壤干燥化程度有所加剧，因此退耕还林中新种植物是否能长期生存尚不明确。而气候变化背景下，退耕还林区的人工植被动态生长研究比较缺乏；同时，缺乏适用于黄土高原的陆面生态水文模型，且现有模型通常对地下水与动态植被的相互作用过程考虑不足，限制了植被动态的模拟。本项目拟选取位于黄土高原的退耕还林典型区，首先改进前期发展的能有效模拟地下水与动态植被相互作用的AVIM-CHM耦合模式；并综合利用重力卫星、遥感、实地观测和再分析等多源资料，开展模型率定和验证；进而预估气候变化背景下，典型区植被的动态变化特征和时空格局、以及土壤水变化趋势，并定量分析气候水文因子与植被生长的关系，揭示人工新种植物能否长期生存的疑问。本项目的实施可以为“适应气候变化的黄土高原退耕还林政策”进一步实施提供科学依据，同时对生态-水文-陆地-大气耦合研究具有重要意义。

自2000年正式实施退耕还林以来，黄土高原植被覆盖明显改善，但未来人工植被能否长期生存尚不明确。为此，我们 1）首先针对主流陆面模式对地表、地下不同径流组分模拟的偏差较大，尤其对地下水位的模拟具有相当大的不确定性问题，进行了系统深入的原因分析；2）进而自主发展了一个新的水文模型SMD (Soil Moisture Dependent)，并在多个流域尺度得到了较好的验证；3）系统评估了中国科学院大气物理研究所自主知识产权的、以动态植被为主要特色的AVIM (Atmosphere–Vegetation Interaction Model) 陆面模式在水文模拟中存在的问题和不足；4）根据黄土高原特性，改进SMD模型，并耦合到AVIM陆面模式中，发展了适用于黄土高原水文植被模拟的自主模式，预估表明未来气候变化背景下黄土高原土壤湿度有进一步变干风险，导致人工植被生长限制，建议未来黄土高原退耕还林人工植被尽量选用蒸发需水量小的深根植物。本项目可以为黄土高原退耕还林进一步实施提供重要的科学支撑。