Identifying Establishment Year and Pre-Conversion Land Cover of Rubber Plantations on Hainan Island, China Using Landsat Data during 1987-2015
Identifying Establishment Year and Pre-Conversion Land Cover of Rubber Plantations on Hainan Island, China Using Landsat Data during 1987-2015
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利用 1987-2015 年 Landsat 数据确定中国海南岛橡胶园的建立年份和转变前的土地覆盖
DOI：
10.3390/rs10081240
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发表时间：
2018-08-01
期刊：
影响因子：
5
通讯作者：
Cao, Jianhua
中科院分区：
文献类型：
--
作者：
Chen, Bangqian;Xiao, Xiangming;Cao, Jianhua
了解橡胶树（Hevea brasiliensis）人工林的林龄对于最佳管理实践、橡胶胶乳产量估计和碳循环研究（例如，生物量、碳库和通量）。然而，在大的地区，没有林分年龄（根据橡胶种植园的建立年份估计）。在这项研究中，我们分析了1987-2015年的Landsat时间序列图像，并开发了识别算法（1）橡胶种植园的建立年份;（2）转换前的土地覆盖类型，如旧橡胶种植园，万年青林和农田。暴露的土壤在人工林建立和线性增加，在非生产期间（橡胶苗成熟的种植园）的冠层关闭被用来确定建立年的橡胶种植园。基于2015年的橡胶林地图（总体精度= 97%）和1987年以来的1981幅Landsat影像，我们绘制了海南岛橡胶林的建立年份（R2 = 0.85/0.99，RMSE = 2.34/0.54年，在像素/种植园尺度上）。结果表明：（1）2000年以来，海南岛西北部和北方地区的农田和老橡胶林向新橡胶林的转化显著，老橡胶林主要分布在东南部内陆地带;（2）1987年以来橡胶种植园的扩张模式是小农户分散种植，没有向高海拔和陡坡地区扩展的趋势;（3）1988年以来新胶园最大的土地来源是老胶园（1.26 × 105公顷），其次是农田（0.95 × 105公顷）和万年青林（0.68 × 105公顷）。建立的算法和地图的建立年和转换前的土地覆盖类型可能是有用的人工林管理，在中国的橡胶种植园扩张的生态评估。
Knowing the stand age of rubber tree (Hevea brasiliensis) plantations is vitally important for best management practices, estimations of rubber latex yields, and carbon cycle studies (e.g., biomass, carbon pools, and fluxes). However, the stand age (as estimated from the establishment year of rubber plantation) is not available across large regions. In this study, we analyzed Landsat time series images from 1987–2015 and developed algorithms to identify (1) the establishment year of rubber plantations; and (2) the pre-conversion land cover types, such as old rubber plantations, evergreen forests, and cropland. Exposed soil during plantation establishment and linear increases in canopy closure during non-production periods (rubber seedling to mature plantation) were used to identify the establishment year of rubber plantations. Based on the rubber plantation map for 2015 (overall accuracy = 97%), and 1981 Landsat images since 1987, we mapped the establishment year of rubber plantations on Hainan Island (R2 = 0.85/0.99, and RMSE = 2.34/0.54 years at pixel/plantation scale). The results show that: (1) significant conversion of croplands and old rubber plantations to new rubber plantations has occurred substantially in the northwest and northern regions of Hainan Island since 2000, while old rubber plantations were mainly distributed in the southeastern inland strip; (2) the pattern of rubber plantation expansion since 1987 consisted of fragmented plantations from smallholders, and there was no tendency to expand towards a higher altitude and steep slope regions; (3) the largest land source for new rubber plantations since 1988 was old rubber plantations (1.26 × 105 ha), followed by cropland (0.95 × 105 ha), and evergreen forests (0.68 × 105 ha). The resultant algorithms and maps of establishment year and pre-conversion land cover types are likely to be useful in plantation management, and ecological assessments of rubber plantation expansion in China.