Land cover of the lower Amazon floodplain, ca. 2008-2009

Land cover of the lower Amazon floodplain ca. 2008-2009 was mapped at 30 m
resolution using a combination of multi-temporal Landsat Thematic Mapper
(TM) and ALOS PALSAR-1 data.  To enable mapping of seasonal
changes in lake and channel areas, map inputs included TM scenes acquired
at very low, mid, and high stage levels of the Amazon River. Land cover
classes mapped were open water (with separate classes for the Amazon
mainstem channel and floodplain lakes and channels), "campo" (3
classes), shrub, and forest. "Campo" refers to seasonally
flooded areas that transition among bare ground, herbaceous, aquatic
macrophyte, and open water states. Campo areas were further divided
between those flooded at  low-, mid-, and high-water levels.
Excluding the main stem channel, the primary  land cover in the
study region was seasonally inundated lakes and channels (59.4%), followed
by permanently inundated lakes and channels (17.9%; these retained water
even at extreme low water stage), seasonally  inundated shrub
(17.1%), and seasonally inundated forest (5.6%).  Seasonally
inundated lakes and channels may be further subdivided into those flooded
at an average low water stage (27.5%), at an average mid-water stage
(59.6%), and at an average high-water stage (12.9%). Renó et al.
(Assessment of deforestation in the Lower Amazon floodplain using
historical Landsat MSS/TM imagery. 2011. Rem. Sens. Envmt.
115(12):3446-3456) estimated that 56% of the floodplain forest cover in
the study area was lost between the late 1970s and 2008, and that 78% of
that deforested area was replaced with non-forest vegetation,
bare/herbaceous, or open water habitats primarily as a result of clearing
for jute plantations and cattle ranching, with smaller areas lost to
channel erosion. We compared 1995 JERS-1 imagery with resampled ALOS
PALSAR imagery for 2007 in order to estimate changes in land cover during
our study period.  The net change from forest habitat to clearing
or water (15.2%) was almost exactly balanced by areas transitioning from
clearing to forest (15.0%).  These results indicate that over
those 20 years, deforestation and regrowth were more or less balanced, and
forest coverage was relatively stable, albeit much lower than in the
pre-colonial era. Our map of floodplain habitats provides input for
scientifically informed policy that incorporates ecological knowledge,
human economic decision-making, and climate-driven hydrologic variability.
The mapped area extends from 57W, 1.4S to 52.9W, 3S and is provided in
GeoTiff and Esri shapefile formats.

亚马逊下游洪泛区约2008-2009年的土地覆盖以30米分辨率绘制，结合了多时相陆地卫星专题制图仪（Landsat Thematic Mapper，TM）和先进陆地观测卫星合成孔径雷达-1（ALOS PALSAR-1）数据。为实现湖泊与河道区域季节变化的制图，输入数据包含亚马逊河极低水位、中水位和高水位期获取的TM影像。绘制的土地覆盖类别包括开阔水域（亚马逊主河道与洪泛区湖泊及河道为单独类别）、‘campo’（3类）、灌木和森林。‘campo’指季节性淹没区域，其状态在裸地、草本、水生大型植物和开阔水域之间转换。campo区域进一步按低水位、中水位和高水位淹没情况划分。排除主河道后，研究区域的主要土地覆盖类型为季节性淹没湖泊及河道（59.4%），其次是永久淹没湖泊及河道（17.9%，即使在极端低水位期仍保留水体）、季节性淹没灌木（17.1%）和季节性淹没森林（5.6%）。季节性淹没湖泊及河道可进一步细分为平均低水位期淹没（27.5%）、平均中水位期淹没（59.6%）和平均高水位期淹没（12.9%）的区域。Renó等人（《利用历史陆地卫星MSS/TM影像评估亚马逊下游洪泛区的森林砍伐》，2011，《环境遥感》（Remote Sensing of Environment），115(12)：3446-3456）估计，1970年代末至2008年间，研究区域洪泛区森林覆盖丧失了56%，其中78%的砍伐区域被非森林植被、裸地/草本或开阔水域栖息地取代——这主要是为种植黄麻和发展牧场而清除植被所致，另有小部分区域因河道侵蚀而丧失。我们将1995年JERS-1影像与重采样后的2007年ALOS PALSAR影像进行对比，以估计研究期间的土地覆盖变化。从森林栖息地向清除区域或水域的净变化（15.2%），与从清除区域向森林转换的区域（15.0%）几乎完全平衡。这些结果表明，在这20年间，森林砍伐与恢复大致平衡，森林覆盖率相对稳定，尽管远低于殖民前时期。我们的洪泛区栖息地地图为科学导向的政策提供了输入，该政策整合了生态知识、人类经济决策及气候驱动的水文变异性。制图区域范围从西经57°、南纬1.4°延伸至西经52.9°、南纬3°，并以GeoTiff和Esri shapefile格式提供。