In tropical dry forests, deciduousness (i.e., leaf shedding during the dry season) is an important adaptation of plants to cope with water limitation, which helps trees adjust to seasonal drought. Deciduousness is also a critical factor determining the timing and duration of carbon fixation rates, and affecting energy, water, and carbon balance. Therefore, quantifying deciduousness is vital to understand important ecosystem processes in tropical dry forests. The aim of this study was to map tree species deciduousness in three types of tropical dry forests along a precipitation gradient in the Yucatan Peninsula using Sentinel-2 imagery. We propose an approach that combines reflectance of visible and near-infrared bands, normalized difference vegetation index (NDVI), spectral unmixing deciduous fraction, and several texture metrics to estimate the spatial distribution of tree species deciduousness. Deciduousness in the study area was highly variable and decreased along the precipitation gradient, while the spatial variation in deciduousness among sites followed an inverse pattern, ranging from 91.5 to 43.3% and from 3.4 to 9.4% respectively from the northwest to the southeast of the peninsula. Most of the variation in deciduousness was predicted jointly by spectral variables and texture metrics, but texture metrics had a higher exclusive contribution. Moreover, including texture metrics as independent variables increased the variance of deciduousness explained by the models from R² = 0.56 to R² = 0.60 and the root mean square error (RMSE) was reduced from 16.9% to 16.2%. We present the first spatially continuous deciduousness map of the three most important vegetation types in the Yucatan Peninsula using high-resolution imagery.

中文翻译：

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结合反射率，光谱解混和高分辨率图像的纹理数据绘制热带干旱森林的树种落叶图

在热带干旱森林中，落叶（即干旱季节的叶子脱落）是植物适应水分限制的重要适应措施，有助于树木适应季节性干旱。落叶性也是决定固碳速率的时间和持续时间，并影响能量，水和碳平衡的关键因素。因此，量化落叶性对于了解热带干燥森林中重要的生态系统过程至关重要。这项研究的目的是使用Sentinel-2图像绘制尤卡坦半岛沿降水梯度的三种热带干旱森林中树木的落叶状况。我们提出了一种将可见和近红外波段的反射率，归一化差异植被指数（NDVI），光谱解混落叶分数，和几个纹理量度来估计树木落叶的空间分布。研究区的落叶度高度可变，并且随着降水梯度的增加而降低，而各站点之间的落叶度空间变化呈反比模式，从半岛的西北到东南分别为91.5％至43.3％和3.4％至9.4％。 。落叶度的大多数变化是由光谱变量和纹理度量共同预测的，但是纹理度量具有更高的排他性贡献。此外，将纹理度量作为独立变量包括在内，增加了模型解释的落叶性方差。站点之间的落叶性空间变化呈反比模式，从半岛西北部到东南部分别为91.5％至43.3％和3.4％至9.4％。落叶度的大多数变化是由光谱变量和纹理度量共同预测的，但是纹理度量具有更高的排他性贡献。此外，将纹理度量作为独立变量包括在内，可以增加模型解释的落叶性差异。站点之间的落叶性空间变化呈反比模式，从半岛西北部到东南部分别为91.5％至43.3％和3.4％至9.4％。落叶度的大多数变化是由光谱变量和纹理度量共同预测的，但纹理度量具有更高的排他性贡献。此外，将纹理度量作为独立变量包括在内，增加了模型解释的落叶性方差。R ² = 0.56至R ² = 0.60，并且均方根误差（RMSE）从16.9％降低至16.2％。我们使用高分辨率图像介绍了尤卡坦半岛三种最重要植被类型的第一个空间连续落叶图。