Leaf litter 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 leaf litter cover data from plots with various levels of herbivore exclusion on the Jornada Experimental Range. 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. Each year in spring and fall from 1995-2005, the total percent cover of leaf litter in each quadrat was estimated by summing the percent of each 10 cm square within a quadrat (including 100 10-cm squares) containing leaf litter (See methods for a detailed explanation). After 2005, sampling frequency changed to every 5 years. This study is ongoing.本数据包包含霍纳达实验牧场（Jornada Experimental Range）内设置有不同食草动物排除处理梯度的样地的枯落物（leaf litter）覆盖度数据。研究样地于1995年设立，分别覆盖黑格兰马草草原与石炭酸灌木灌丛（creosotebush shrubland）两种植被类型，旨在对比食草动物对两类植被生态系统过程的影响差异。平行研究同时在美国新墨西哥州的塞维利塔长期生态研究站（Sevilleta LTER site）与墨西哥杜兰戈州的马皮米生物圈保护区（Mapimi Biosphere Reserve）同步开展。所有研究样地的面积均为1千米×0.5千米。在黑格兰马草草原样地中，随机布设了4个重复实验区块，通过以下4组食草动物排除处理开展植被响应监测：a）排除所有哺乳动物食草动物（涵盖牛、兔形目动物与啮齿类）；b）仅排除兔形目动物与牛；c）仅排除牛；d）对照组，允许所有食草动物自由进入样地。由于石炭酸灌木灌丛样地全程禁止放牧牛群进入，该样地仅随机布设了3个重复实验区块，对应的处理组分别为：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）仅排除兔形目动物；c）对照组，允许所有食草动物自由进入样地。每个样地内均以系统抽样方式布设6×6的样点网格，样点间距为5.8米，总计设置36个采样点。每个采样点处均设有永久型1米×1米植被调查样方（quadrat）。1995年至2005年期间，每年春季与秋季均会对每个样方内的枯落物总盖度进行估算：通过统计样方内每一个10厘米×10厘米小样格（样方总计包含100个此类小样格）中存在枯落物的比例并求和得到具体数值（详细方法参见研究方法部分）。2005年之后，采样频率调整为每5年一次。本研究目前仍在持续进行中。