Ground cover and biomass projection photos for the BBC collapse scar

We used digital photographs to project the biomass over the growing season. This data set contains ground cover photos of plots from the center of the BBC collapse scar (0m) into the surrounding fire scar (30m) of the Survey Line Fire (burned in June-July 2001) for the growing seasons of 2003 and 2004. Also included are ground cover photos of plots along the biomass transect used to create the projected biomass data.
We calculated the percent cover of vegetation for the biomass and intensively monitored transects from digital photographs. Photographs were rectified to 10,000 x 10,000 pixels and a 20 x 20 grid was applied to the photograph. The percentage of each plant type was estimated in each grid cell. The percent cover was regressed against the measured dry biomass to project biomass for the intensively measured transect. We did not project moss biomass and instead assumed it to be the same for both transects.
We projected the change in biomass over the growing season from the change in greenness determined from digital photographs. We chose five dates throughout the growing season with pictures of equal color saturation, focus and aspect. From these we estimated the percent photosynthetic biomass by selecting areas of green on the photograph and calculating the percentage of the total pixels made up by these areas. We estimated curves for the change in % green vegetation for 0, 6 m and the mean of the remaining distances along the transect (12, 18, 24, and 30 m), as these regions of the transect exhibited different patterns of greenness across the growing season of 2004. To estimate photosynthetic biomass over the growing season, we corrected the biomass estimates for the study transect to account for the change in green vegetation associated with growth and senescence

我们采用数码照片推演生长季内的生物量变化。本数据集涵盖2003年与2004年生长季的样地地表覆盖照片，采样范围自BBC坍塌坑（BBC collapse scar）中心（0米处）延伸至2001年6-7月过火的测线火灾（Survey Line Fire）周边火烧迹地（30米处）。此外，数据集还包含用于生成推演生物量数据的生物量样带沿线样地的地表覆盖照片。
我们基于数码照片，计算了生物量样带与密集监测样带的植被盖度百分比。所有照片均校正至10000×10000像素分辨率，并叠加20×20的网格。对每个网格单元内的各植物类型占比进行估算。将植被盖度百分比与实测干生物量进行回归分析，以此推演密集监测样带的生物量。我们未对苔藓生物量进行推演，而是假设两条样带的苔藓生物量一致。
我们通过数码照片获取的绿度变化，推演生长季内的生物量变化。我们在生长季内选取5个采样日期，确保各日期拍摄的照片具有一致的色彩饱和度、对焦效果与拍摄方位。基于这些照片，我们通过选取图像中的绿色区域并计算其占总像素的比例，估算光合生物量占比。鉴于2004年生长季内样带不同区域的绿度变化模式存在差异，我们分别针对样带上的0米、6米点位，以及其余距离区间（12、18、24与30米）的平均绿度，估算了绿色植被百分比的变化曲线。为准确估算生长季内的光合生物量，我们对研究样带的生物量估算值进行校正，以修正植物生长与衰老过程中绿色植被变化所带来的偏差。