Vegetation cover data from line-intercept transects in the long-term Small Mammal Exclusion Study (SMES) at Jornada Basin LTER, 1995-2005

This package contains perennial vegetation cover data measured using the line-intercept method from plots with various levels of herbivore exclusion on Jornada Experimental Range (JER) and Chihuahuan Desert Rangeland Research Center (CDRRC) lands. Study sites were established in 1995; one in black grama grassland and the other in creosotebush shrubland to compare the impact of herbivores on ecosystem processes between these vegetation types. Parallel studies were established at the Sevilleta LTER site (New Mexico, USA) and Mapimi Biosphere Reserve (Durango, Mexico). Each study site is 1 km by 0.5 km in area. Four replicate experimental blocks were randomly located at the grassland study site to measure vegetation responses using exclusion treatments including a) all mammalian herbivores, including cattle, lagomorphs, and rodents, b) lagomorphs and cattle only, c) cattle only, and d) control accessible to all herbivores. Because grazing cattle are excluded from the entire creosote site, only three replicate experimental blocks were randomly located there including a) all mammalian herbivores, including lagomorphs, and rodents, b) lagomorphs only, and c) control accessible to all herbivores. Thirty-six sampling points were positioned at 5.8-meter intervals on a systematically located 6 by 6 point grid within each plot. A permanent one-meter by one-meter vegetation measurement quadrat is located at each of the 36 points. The vegetation line-intercept measurements in this data package were made in fall 1995 and fall 2005 to coincide with low-level aerial photography campaigns. Three 29-meter lines were measured along three out of six rows of permanent vegetation quadrats. Intercept locations for live, perennial plant cover and bare ground were measured along each line at 10cm resolution, which is comparable to the resolution of the aerial photos. Plants were identified to species level where possible. The resulting cover data can used to ground-truth cover estimates from aerial photography or for comparison to annual measures of vegetation from 1 x 1 meter permanent vegetation quadrats. This study is complete.

本数据包包含采用截线法（line-intercept method）采集的多年生植被覆盖度数据，数据采集于霍纳达实验牧场（Jornada Experimental Range, JER）与奇瓦瓦荒漠牧场研究中心（Chihuahuan Desert Rangeland Research Center, CDRRC）的不同食草动物排除处理样地。研究样地于1995年设立，分别设置在格兰马草（black grama）草原与牧豆灌丛（creosotebush shrubland）中，用以对比不同植被类型下食草动物对生态系统过程的影响。同时在美国新墨西哥州塞维利塔长期生态研究站（Sevilleta LTER site）与墨西哥杜兰戈州马皮米生物圈保护区（Mapimi Biosphere Reserve）设立了平行研究样地。各研究样地面积均为1 km × 0.5 km。在格兰马草草原研究样地中，随机布设了4个重复实验区组，采用以下食草动物排除处理方案以观测植被响应：a) 排除所有哺乳动物食草动物（包括牛类、兔形目动物与啮齿类）；b) 仅允许牛类与兔形目动物进入；c) 仅允许牛类进入；d) 对照样地，允许所有食草动物进入。由于牧豆灌丛样地整体已排除放牧牛类，仅布设了3个重复实验区组，其处理方案为：a) 排除所有哺乳动物食草动物（包括兔形目动物与啮齿类）；b) 仅允许兔形目动物进入；c) 对照样地，允许所有食草动物进入。每个样地内布设6×6的系统采样网格，网格内各采样点间距为5.8米，共设置36个采样点。每个采样点处均设置永久性1m×1m植被调查样方（quadrat）。本数据包中的植被截线法测量数据采集于1995年秋季与2005年秋季，与低空航空摄影作业时间同步。在永久性植被样方的6排中选取3排，沿每排布设3条29米长的截线。沿每条截线以10厘米分辨率记录活的多年生植物覆盖与裸地的截点位置，该分辨率与航空照片的分辨率相当。尽可能对植物进行物种水平鉴定。所得覆盖度数据可用于验证航空摄影获取的覆盖度估算结果，或与1m×1m永久性植被样方的年度植被监测数据进行对比。本研究已完成。