海河流域土地利用变化对地表蒸散发和总初级生产力影响的模拟研究

The strong human activity induced land-use/land-cover change (LUCC) significantly changed evapotranspiration (ET), photosynthesis, and many other land processes. However, because the restrictions of the methods and the uncertainties associated with data, the magnitudes of these LUCC influences and their spatial-temporal characteristics are inadequately researched. The new generation land surface models (LSMs) include biogeochemical modules and provide a feasible method for quantitatively investigating the responses of land carbon and water fluxes to LUCC. The proposed project takes Hai River basin as an example to research the influences of LUCC on ET and gross primary productivity (GPP). In the first step, we improve the sub-grid LUCC parameterizations of two LSMs (CLM4.5 and DLM). Secondly, using observations from 7 flux towers we optimize the key parameters of ET and photosynthesis processes in the two models. Then, we run the improved LSMs with high accuracy China LUCC data from five historical periods during 1980-2015, observation-based forcing and soil data. Based on the LSMs simulations and the LUCC datasets, we quantify the influencing magnitudes of LUCC on ET and GPP, and their spatial-temporal characteristics in Hai River basin. This project research can not only provide insights into the development of human modules in LSMs, but also has important scientific significance for regulating human land use types to mitigate and adapt climate change.

区域尺度上剧烈的人类活动引起的土地利用/土地覆盖变化（LUCC）显著影响地表蒸散发（ET）和光合作用等陆面过程。然而，受研究方法和数据资料不确定性等因素限制，这些影响的强度及其特征的定量研究仍然有限。耦合生物地球化学过程的新一代陆面过程模型(LSM)为定量揭示LUCC对陆表碳水通量的影响提供了一种可行的方法。本项目以海河流域为例，首先改进两个LSM（DLM和CLM4.5）次网格LUCC参数化方案。其次利用7个通量塔观测数据优化改进后模型ET和光合作用过程关键参数。在此基础之上，以1980-2015年间5期高精度LUCC数据和基于观测的气象及土壤数据作为输入，通过模型模拟定量揭示近40年海河流域剧烈LUCC过程对陆表ET和总初级生产力扰动影响的强度及其时空特征。本项目的实施不仅能够为LSM人类活动影响模块的研发提供理论基础，而且对于减缓与适应气候变化的土地利用方式调控具有科学指导意义。

项目实施中，利用基于卫星遥感观测的连续土地利用/土地覆盖变化（LUCC）、植被指数结合气象、土壤等多源数据定量分析了1980年以来海河流域LUCC过程及其主要驱动力。在此基础之上，利用目前最具代表性的CLM5.0陆面过程模式，以1980年以来7期LUCC数据和基于观测的气象数据作为模式输入设置多组模式模拟实验，通过模拟实验结果分析，揭示了1980年以来，海河流域LUCC和气候变化及CO2浓度上升（CCO）对地表-大气间光合作用（GPP）、水（ET）和能量通量（感热通量和潜热通量）交换的影响。研究结果显示，在人类活动强烈影响地表覆被的海河流域，农田扩张主导的LUCC过程使得地表蒸散发和潜热通量总体上增加，CCO总体上减小蒸散发和潜热通量；LUCC和CCO共同促进了海河流域 GPP增加；LUCC和CCO对海河流域感热通量影响总体上相似，即均使得地表吸收热量增加。