Environmental Drivers of Water Use for Caatinga Woody Plant Species: Combining Remote Sensing Phenology and Sap Flow Measurements
Environmental Drivers of Water Use for Caatinga Woody Plant Species: Combining Remote Sensing Phenology and Sap Flow Measurements
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DOI：
10.3390/rs13010075
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发表时间：
2020-12
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影响因子：
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通讯作者：
Rennan A. Paloschi;D. Ramos;D. Ventura;R. Souza;Eduardo Souza;L. Morellato;R. Nóbrega;Í. C. Coutinho
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文献类型：
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作者：
Rennan A. Paloschi;D. Ramos;D. Ventura;R. Souza;Eduardo Souza;L. Morellato;R. Nóbrega;Í. C. Coutinho
我们调查了南美最大的季节性干旱森林Caatinga植被的用水情况。我们确定并分析了木本植物的环境物候驱动因素及其与蒸腾作用的关系。为了监测物候的演变，我们在不同的空间和时间尺度上使用遥感指标：归一化差异植被指数（NDVI），土壤调整植被指数（SAVI），和绿色色度坐标（GCC）。为了代表物候，我们使用的GCC提取自原位自动数码相机图像;指数计算的传感器包括NDVI，SAVI和GCC从哨兵-2A和B卫星图像，和NDVI产品MYD 13 Q1和MOD 13 Q1从中等分辨率成像光谱仪（MODIS）。环境驱动因素包括持续监测的降雨量、气温、土壤湿度、净辐射和蒸汽压力不足。为了监测土壤水分状况和植被水分利用，我们沿沿着三个土壤剖面安装了土壤水分传感器，并为五种植物安装了液流传感器。我们的研究表明，近地表GCC数据发挥了重要作用，允许个人监测的物种，而物种的树干液流数据相关性更好地与NDVI，SAVI，和GCC比物种的近地表GCC。木材密度似乎影响蒸腾停止时间在旱季，鉴于最低木材密度的物种达到可以忽略不计的值的蒸腾早在本赛季比那些高木质密度。我们的研究结果表明，土壤水分的有效性是主要的限制因素，在80%以上的一年中的蒸腾作用，和物候响应和水的利用直接相关的水的有效性时，土壤剖面的相对饱和度下降到0.25以下。
We investigated the water use of Caatinga vegetation, the largest seasonally dry forest in South America. We identified and analysed the environmental phenological drivers in woody species and their relationship with transpiration. To monitor the phenological evolution, we used remote sensing indices at different spatial and temporal scales: normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI), and green chromatic coordinate (GCC). To represent the phenology, we used the GCC extracted from in-situ automated digital camera images; indices calculated based on sensors included NDVI, SAVI and GCC from Sentinel-2A and B satellites images, and NDVI products MYD13Q1 and MOD13Q1 from a moderate-resolution imaging spectroradiometer (MODIS). Environmental drivers included continuously monitored rainfall, air temperature, soil moisture, net radiation, and vapour pressure deficit. To monitor soil water status and vegetation water use, we installed soil moisture sensors along three soil profiles and sap flow sensors for five plant species. Our study demonstrated that the near-surface GCC data played an important role in permitting individual monitoring of species, whereas the species’ sap flow data correlated better with NDVI, SAVI, and GCC than with species’ near-surface GCC. The wood density appeared to affect the transpiration cessation times in the dry season, given that species with the lowest wood density reach negligible values of transpiration earlier in the season than those with high woody density. Our results show that soil water availability was the main limiting factor for transpiration during more than 80% of the year, and that both the phenological response and water use are directly related to water availability when relative saturation of the soil profile fell below 0.25.