海滨湿地盐沼植被盐分胁迫高光谱遥感响应机理研究

Coastal wetlands are continuously damaged because of people seeking the tremendous economical benefits in a short term. Therefore, researches on the ecosystem structure, ecological function and ecological restoration in coastal wetlands have become the great demand because our government pays much attention to ecological safety and protection in coastal zones. When salt marsh vegetation is subjected to different environmental stress, photosynthetic efficiency and carbon allocation will be affected. Consequently, it will have some negative impacts on the exchange of carbon, water and energy between vegetation and atmosphere. The author discussed the hyperspectral response mechanism of salt marsh vegetation in coastal wetland to salt stress by using microscopic and macroscopic, qualitative and quantitative approaches. Field experimental work was carried out on several salt marsh plants grown in coastal wetland under controlled laboratory conditions over a full growth cycle. Firstly, we identified the change of phenological phase and external characteristics under the impact of salt stress. Then, we quantitatively analyzed the response pattern between the salt content in the soil and in the leaves of salt marsh plant and spectral reflectance. At the same time, we still quantitatively estimated the response patterns between the biophysical and biochemical of salt marsh plants sensitive to salt stress and hyperspectral indices retrieved from the spectral reflectance during the whole growth cycle. Based on above analysis, we further achieved the spatial distribution and its characteristics of salt stress at pixel scale by using high spectral and spatial resolution remotely sensed images. In addition, we also attained the spatial distribution and its characteristics of biochemical parameters of salt marsh vegetation and dug through the impact of salt stress on the health and sustainable development of coastal wetland ecosystem. Through the research, we can enrich the theory and method of degraded ecosystem restoration in coastal wetlands.

因经济增长而释放的短视利益驱动，海滨湿地植物不断受到侵占和破坏。海滨湿地生态系统的结构、生态功能及环境修复研究已成为国家对沿海区域生态安全与保护的重大需求。盐沼植被一旦受到盐分胁迫，势必会影响光合作用效率和碳分配，造成植物和大气之间的碳、水和能量之间的交换。本项目拟综合运用微观与宏观、定性与定量分析相结合的方法，深入探讨海滨湿地盐沼植物盐分胁迫的高光谱响应机理。通过野外盐分胁迫试验，厘清盐分胁迫造成盐沼植物物候期以及外在表征特征变化，定量分析土壤盐分含量、叶片盐分含量与反射光谱之间的响应模式；受盐分胁迫影响的盐沼植物叶片色素含量与对盐分胁迫敏感的高光谱指数的响应模式；利用高光谱高空间分辨率遥感图像，揭示像元尺度下海滨湿地盐沼植物盐分胁迫和对盐分胁迫敏感的盐沼植物生化指标的高光谱空间分布及其特征，并挖掘盐分胁迫对湿地生态系统健康与可持续发展的影响，丰富退化海滨湿地生态系统修复方法。

当胁迫因子通过生化机理损害植物生理机能时，就势必会造成植物和大气之间的碳、水和能量之间的交换。因此，深入理解环境胁迫作用的时空分布特征和对生态系统功能的影响机制（或模式）已势在必行。申请者以滨海湿地典型盐沼植被为研究对象，基于变量(R800-R635)／(R800+R635)应用逐步线性回归法构建的海滨湿地碱蓬地上鲜生物量估算模型精度最高，R2为0.715，均方根误差RMSE为99.79g/m2。滨海湿地土壤总碳、有效磷、速效钾、全盐和有机质含量在研究区从东到西的推进过程中呈现逐渐递减规律；而土壤pH值则呈现逐渐递增的趋势。土壤盐度对滩涂湿地植被群落分布特征具有关键作用，从某种程度上也影响着滩涂湿地植被的耐盐性强弱。基于SVM构建滨海湿地土壤有机质的估算模型精度最高，预测决定系数R2为0.93，均方根误差RMSE为0.23。碱蓬野外盐分胁迫试验结果表明：盐度对盆栽碱蓬生理指标(株高、鲜质量、干质量、叶绿素含量、可溶性总糖和蛋白质质量比)存在比较明显的响应作用。盐度对盆栽碱蓬冠层反射光谱存在显著响应。盐度越大，碱蓬冠层反射光谱在绿光反射率和近红外反射坪台的反射率就越小。不同盐度处理下，碱蓬植株生理指标株高、鲜质量、干质量、叶绿素含量、可溶性总糖和蛋白质质量比均在反射光谱中存在敏感波段，分别是547 nm，555 nm，548 nm，556 nm，546 nm和2300 nm。在不同盐度下MTCI、MNDVI1、DCNI、TCARI/OSAVI和R546光谱特征指数值之间存在明显差异，可作为盐分胁迫下碱蓬植株生理指标的高光谱响应特征变量。基于盐沼植被的冠层反射光谱，应用差异分析、相关分析和敏感性分析发现D974/ D628，(D816- D592)/( D816+ D592), (D816- D628)/( D816+ D628)，(D903- D851)/( D903+ D851)，(D974- D592)/( D974+ D592)，(D974- D628)/( D974+ D628)植被指数与盐分胁迫的判定系数均达到0.90以上，且(D903- D851)/( D903+ D851)植被指数与盐分胁迫的相关性最高，多重判定系数为0.96。