Quadrat vegetation cover data on 1m x 1m plots from the long-term Small Mammal Exclusion Study (SMES) at Jornada Basin LTER, 1995-2020

This data package contains vegetation cover from plots with various levels of herbivore exclusion on the Jornada Experimental Range (JER) and Chihuahuan Desert Rangeland Research Center (CDRRC) in Dona Ana County, southern New Mexico, USA. 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. At each quadrat, percent cover by individual plant species is measured. Other measurements include height (cm) of each species in the quadrat, and plant condition (living or dead). Data were collected in the spring and fall of every year from 1995 to 2005. After 2005, sampling frequency changed to every 5 years in the fall. This study is ongoing.

本数据集包含美国新墨西哥州南部多纳·安娜县乔纳达实验牧场（Jornada Experimental Range, JER）与奇瓦瓦荒漠牧场研究中心（Chihuahuan Desert Rangeland Research Center, CDRRC）内不同食草动物排除梯度样地的植被覆盖数据。
研究样地于1995年设立，分别设置于黑格兰马草草原与杂酚油灌丛两种植被类型中，用以对比食草动物对两类生态系统过程的影响。同期在新墨西哥州塞维利塔长期生态研究（Long-Term Ecological Research, LTER）站点与墨西哥杜兰戈州马皮米生物圈保护区设立了平行研究。
各研究样地的面积均为1千米×0.5千米。草原样地内随机布设4个重复实验区，采用以下排除处理以探究植被响应：a) 排除所有哺乳动物食草动物（涵盖牛类、兔形目动物与啮齿类）；b) 仅保留牛类与兔形目动物，排除啮齿类；c) 仅保留牛类，排除兔形目动物与啮齿类；d) 对照组，允许所有食草动物自由进入。
由于杂酚油灌丛样地全域已排除放牧牛类，因此仅布设3个重复实验区，处理设置为：a) 排除所有哺乳动物食草动物（涵盖兔形目动物与啮齿类）；b) 仅保留兔形目动物，排除啮齿类；c) 对照组，允许所有食草动物自由进入。
每个样地内以系统布设的6×6样点网格设置36个采样点，样点间距为5.8米。每个采样点均配备永久性1米×1米植被调查样方。在每个样方中，需记录各植物物种的盖度百分比，同时测量各物种的株高（单位：厘米）与植株存活状态（存活或枯死）。
采样工作于1995年至2005年期间，每年春季与秋季各开展一次；2005年后，采样频率调整为每5年秋季开展一次。本研究目前仍在持续进行。