ISLSCP II C4 Vegetation Percentage

The photosynthetic composition (C3 or C4) of vegetation on the land surface is essential for accurate simulations of biosphere-atmosphere exchanges of carbon, water, and energy. C3 and C4 plants have different responses to light, temperature, CO2, and nitrogen; they also differ in physiological functions like stomatal conductance and isotope fractionation. A fine-scale distribution of these plant types is essential for earth science modeling.

The C4 percentage is determined from data sets that describe the continuous distribution of plant growth forms (i.e., the percent of a grid cell covered by herbaceous or woody vegetation), climate classifications, the fraction of a grid cell covered in croplands, and national crop type harvest area statistics. The staff from the International Satellite Land Surface Climatology Project (ISLSCP) Initiative II have made the original data set consistent with the ISLSCP-2 land/water mask. This data set contains a single file in ArcInfo ASCIIGRID format.

This data set is one of the products of the International Satellite Land-Surface Climatology Project, Initiative II (ISLSCP II) data collection which contains 50 global time series data sets for the ten-year period 1986 to 1995. Selected data sets span even longer periods. ISLSCP II is a consistent collection of data sets that were compiled from existing data sources and algorithms, and were designed to satisfy the needs of modelers and investigators of the global carbon, water and energy cycle. The data were acquired from a number of U.S. and international agencies, universities, and institutions. The global data sets were mapped at consistent spatial (1, 0.5 and 0.25 degrees) and temporal (monthly, with meteorological data at finer (e.g., 3-hour)) resolutions and reformatted into a common ASCII format. The data and documentation have undergone two peer reviews.

ISLSCP is one of several projects of Global Energy and Water Cycle Experiment (GEWEX) [http://www.gewex.org/] and has the lead role in addressing land-atmosphere interactions -- process modeling, data retrieval algorithms, field experiment design and execution, and the development of global data sets.

地表植被的光合组成（C3或C4）对于精确模拟生物圈与大气之间的碳、水、能量交换至关重要。C3和C4植物对光、温度、二氧化碳和氮的反应不同；它们在生理功能上亦存在差异，如气孔导度和同位素分馏。这些植物类型的精细分布对于地球科学建模至关重要。

C4植物百分比是通过描述植物生长形态连续分布的数据集（即网格单元被草本或木本植被覆盖的百分比）、气候分类、网格单元被耕地覆盖的比例以及国家作物类型收获面积统计数据确定的。国际卫星陆地气候学项目（ISLSCP）倡议II的团队成员已使原始数据集与ISLSCP-2陆地/水域掩膜保持一致。该数据集包含一个以ArcInfo ASCIIGRID格式存储的单一文件。

此数据集是国际卫星陆地气候学项目（ISLSCP）倡议II（ISLSCP II）数据收集之一，该数据集包含1986年至1995年十年期间50个全球时间序列数据集。选定的数据集跨越更长的时间段。ISLSCP II是一个一致的数据集集合，这些数据集由现有数据源和算法编制而成，旨在满足全球碳、水、能量循环建模者和研究者的需求。数据来自多个美国和国际机构、大学和机构。全球数据集在一致的时空分辨率下进行了映射（空间分辨率为1度、0.5度和0.25度，时间分辨率为月度，气象数据更细，例如3小时），并重新格式化为通用ASCII格式。数据和文档已经过两次同行评审。

ISLSCP是全球能量和水循环实验（GEWEX）[http://www.gewex.org/]的多个项目之一，并在解决陆地-大气相互作用方面扮演主导角色——过程建模、数据检索算法、实地实验设计和执行，以及全球数据集的开发。