East and west boundary fence plant line intercepts - percent cover for all species beginning 1986

BACKGROUND. In the spring of 1982, as part of the establishment of the Jornada Long-Term Ecological Research site in southern New Mexico, a 135 ha portion of a 1500 ha, internally drained, watershed was exclosed from grazing by domestic livestock. Prior to exclosure the watershed, as well as the rest of the Jornada basin, had been moderately to heavily grazed for the past 100 years. Concurrent with grazing, the vegetation had undergone a dramatic change from desert grassland, with an almost continuous cover of C4 perennial grasses, to isolated patches of the original grassland in a mosaic with desert shrub dominated plant communities (Buffington and Herbel, 1965). The exclosure lies along a northeast facing piedmont slope at the base of a steep isolated mountain peak, and covers a variety of component landforms from the foot of the mountain to the basin floor. This provided the opportunity to investigate the response of vegetation with respect to landscape characteristics as well as release from grazing. This summary data set consists of percent cover of all perennial plant species from the plant line intercept measurements on either side of the LTER-I exclosure East and West boundary fence. Data is sorted by treatment (grazed, ungrazed), year, fence line, station, then species i.d. Along the East Boundary fence line, the east side is ungrazed (control) and the west side is grazed (treatment). Along the West Boundary fence line, the east side is grazed and the west side is ungrazed. Each plant line transect is divided into 6 5-meter segments. All perennials were measured at about 5 year intervals as the length of intercept for each species along a 30-meter line oriented perpendicular to the fence. Summary data presented in this data set is the average percent cover for the outer-most 2 5-meter segments for the respective treatment (grazed or ungrazed). The term outer-most is relative to the fence. The 5-meter segment on either side of the fence is not included in the cover estimates due to fence line effect disturbances; e.g., cattle trails, tumbleweeds trapped along fence, etc. This summary data does not include the first year of measurement in 1982 because of numerous problems with species codes used that could not resolved.研究背景 1982年春季，为设立位于新墨西哥州南部的乔兰达长期生态研究站点（Jornada Long-Term Ecological Research），从一片1500公顷的内流流域（internally drained watershed）中划定135公顷区域，实施家畜放牧封禁。此前的100年间，该流域与乔兰达盆地其余区域均遭受了中度至重度的放牧干扰。伴随放牧活动，植被发生了显著转变：原本覆盖近乎连续的C4多年生草本荒漠草原，逐渐演变为以荒漠灌丛为优势群落的镶嵌格局，仅残存零星的原生草原斑块（Buffington与Herbel，1965）。 该封禁样地坐落于一座陡峭孤立山峰基部的东北向山麓缓坡，涵盖了从山麓到盆地底部的多种地貌单元。这为探究植被对景观特征的响应以及放牧解除后的植被动态变化提供了理想的研究契机。 本汇总数据集包含LTER-I封禁样地（LTER-I exclosure）东西两侧围栏沿线通过样线截距法（line intercept measurements）测得的所有多年生植物物种的盖度百分比数据。数据按照处理类型（放牧组、禁牧组）、年份、围栏线、样站及物种标识进行排序。在东侧围栏沿线，围栏东侧为禁牧对照样地，西侧为放牧处理样地；在西侧围栏沿线，围栏东侧为放牧处理样地，西侧为禁牧对照样地。每条植物样线样带被划分为6段5米的样段。所有多年生植物的测量均沿垂直于围栏的30米样线开展，以各物种的截距长度为测定指标，采样间隔约为5年。本数据集所呈现的汇总数据，为对应处理组（放牧组或禁牧组）最外侧2段5米样段的平均盖度百分比。此处的“最外侧”是相对于围栏而言：由于围栏沿线存在牲畜步道、沿围栏堆积的风滚草等干扰效应，围栏两侧各5米的样段未纳入盖度估算。 由于1982年首次测量时存在诸多无法解决的物种编码问题，本汇总数据未纳入1982年的测量结果。