科尔沁沙丘-草甸梯级生态带水热碳循环机理及其对禁牧围封的响应

The national "ecological protection red line" was introduced to protect the important ecological function areas, ecological fragile areas and sensitive areas, and biodiversity conservation areas at an unprecedented height. Since the implementation of the national grassland ecological subsidy incentives and grazing prohibition policy was carried out, although the Horqin sandy land vegetation coverage increased, the vegetation diversity was worse, many lakes shrink or even disappear, the eco hydrological process of grazing enclosure is not clear. This project selected Horqin meadow dune with different landforms and vegetation ecological cascade combination unit, did the continuous observation of the implementation of carbon fluxes of water and heat, the fixed-point field, using model, quantitative description, factorial analysis and response identification method, reveal the grazing and grazing enclosure in typical ecological zones of water - heat - carbon cycle coupling the mechanism, clear step ecological zone eco hydrological processes in response to grazing enclosure, coupled identification of environmental factors on water and heat factors of sand dunes and meadow ecosystem carbon decoupling effect, discussion on the key problems of cascade ecological zone hydrothermal carbon cycle and its interaction process, the research of eco hydrology theory to reveal the rich sand, human activities have important significance of hydrothermal carbon cycle for the scientific response relationship, provide a scientific basis for sand sealing and grazing around the national ecological protection.

国家 “生态保护红线”的出台对重要生态功能区、生态脆弱区或敏感区、生物多样性保育区以前所未有的高度加以保护。国家实施草原生态补助奖励机制和禁牧围封政策以来，尽管科尔沁沙地植被盖度有所增大，但植被多样性变差，众多湖泡萎缩甚至消失，禁牧围封下生态水文过程尚不明确。本项目选取科尔沁沙丘-草甸梯级生态带不同地貌-植被组合单元，实施水分、热量、碳通量的野外定点连续观测，采用模型构建、定量描述、析因分析与响应辨识等方法，揭示放牧与禁牧围封下典型生态类型区水-热-碳耦合循环机理，明晰梯级生态带生态水文过程对禁牧围封的响应关系，辨识环境因子对沙丘与草甸生态系统水热碳要素的耦合-解耦影响、探讨梯级生态带水热碳循环规律及其互馈动力学过程等关键问题，本研究对丰富沙地生态水文学理论，揭示人类活动下水热碳循环响应关系有重要意义，为科学实施沙地禁牧围封与国家生态保护提供科学依据。

国家实施草原生态补助奖励机制和禁牧围封政策以来，尽管科尔沁沙地植被盖度有所增大，但植被多样性变差，禁牧围封下生态水文过程尚不明确。本项目开展了科尔沁沙丘-草甸梯级生态带不同生态类型区水、热、碳通量的野外定点连续观测与模拟、定量评价典型生态类型区水热、水碳关系、探求梯级生态带水热碳循环规律及生态水文过程对禁牧围封的响应。研究表明：.沙丘土壤储水量由大到小依次为固定沙丘＞流动沙丘＞半流动沙丘＞半固定沙丘，与降雨量具有很好的一致性。流动和半流动沙丘深层渗漏量是降雨的主要转化形式，分别占总降雨量的57.35%和54.56%；半固定和固定沙丘植被蒸腾是降雨的主要转化形式，分别占总降雨量的77.15%和54.88%。草甸地水分补给来源不仅源于降水，而且部分水量源于地下水补给；研究区近地表能量耗散以潜热通量为主；秋季(9月后期)潜热通量显著降低，冬季时略低于显热通量，各季节碳通量峰值呈夏季>秋季>春季>冬季。沙丘生长季NEE的季节变化呈先增后减趋势，表现为碳汇。草甸生长季NEE曲线表现为先下降后上升的较大波动，表现为强碳汇；草地禁牧围封后，表层凋落物积累增多，使土壤的肥力得到改善，酶活性增加，降雨量显著性减少的趋势下差巴嘎蒿、小叶锦鸡儿等植物覆盖度仍然逐年增大，沙丘逐渐由流动沙丘演变成半流动沙丘、半固定沙丘和固定沙丘，水、热、碳循环也发生了相应的改变，虽然植被覆盖度增大，但物种多样性降低，但仍不能称其为健康的水文生态系统，但应该是在气候变化和人类影响下系统演变的必然阶段。.本研究对丰富沙地生态水文学理论，揭示人类活动下水热碳循环响应关系有重要意义，为科学实施沙地禁牧围封与国家生态保护提供科学依据。