Seasonal non-destructive vegetation measurements at 15 net primary production (NPP) study sites at Jornada Basin LTER, 1989-ongoing

This data package contains non-destructive quadrat measurements collected for the long-term Net Primary Production (NPP) study at the Jornada Basin LTER. Data here include measurements of horizontal cover and vertical height of plants observed at permanent NPP quadrats at 15 study sites. Sites were selected to represent the 5 major ecosystem types in the Chihuahuan Desert (upland grasslands, playa grasslands, mesquite-dominated shrublands, creosotebush-dominated shrublands, tarbush-dominated shrublands). For each ecosystem type, three sites were selected to represent the range in variability in production and plant diversity; thus the locations are not replicates. All sites are excluded from domestic grazing. Eleven sites are in non-grazed pastures, and at the other four sites 1 hectare areas around the observational plots were fenced in 1988. At all sites a grid of 49 (48 at one playa location) 1m x 1m replicate quadrats was laid out when sampling began in 1989. Grids consist of 49 quadrats arranged in a square 7 x 7 pattern, with quadrats 10 m apart (P-COLL has 48 quadrats in a 3 x 16 pattern). Standing vegetation in quadrats is sampled three times a year: in winter (February - March), before shrubs begin spring growth; in spring (May), when shrubs and spring annuals have reached peak biomass; in fall (late summer; October), when summer annuals have reached peak biomass but before killing frosts. Additional observations of plant count and phenological stage are also made. This dataset is subsequently used to determine quadrat biomass and net primary production. Details and linked data packages are described in the methods element. This is an ongoing dataset with new quadrat measurements collected in the spring, fall and winter of each year. Attention: 1) For most species, these data are not appropriate for estimates of percentage cover because of the way the data are collected. See Note 1 in the methods element for further details.

本数据集包含为霍罗那盆地长期生态研究站（LTER）开展的长期净初级生产力（Net Primary Production, NPP）研究采集的非破坏性样方测量数据，涵盖15个研究站点的永久性NPP样方中观测得到的植物水平盖度与垂直高度测量结果。

研究站点的选取旨在代表奇瓦瓦沙漠的5种主要生态系统类型：高地草原、干盐湖草原、牧豆树主导灌丛、杂酚灌丛主导灌丛与塔布什灌丛主导灌丛。针对每一类生态系统类型，我们选取3个站点以覆盖生产力与植物多样性的变异梯度，因此这些站点并非重复样点。

所有站点均禁止家畜放牧。其中11个站点位于未放牧牧场内，其余4个站点的观测样地周边1公顷区域于1988年完成围栏布设。1989年启动采样时，所有站点均布设了由49个（其中1个干盐湖站点为48个）1米×1米重复样方组成的样方网格：49个样方的网格采用7×7正方形排布，样方间距为10米（P-COLL站点采用3×16排布，共包含48个样方）。

样方内现存植被每年开展3次采样：冬季（2月-3月，灌丛春季萌发前）、春季（5月，灌丛与春季一年生植物生物量达到峰值时）、秋季（夏末/10月，夏季一年生植物生物量达到峰值但初霜来临前）。此外还同步开展了植物个体计数与物候期观测。

本数据集后续将用于计算样方生物量与净初级生产力。详细信息与关联数据集详见方法模块。本数据集为持续更新的动态数据集，每年春、秋、冬三季均会采集新的样方测量数据。

注意事项：1）由于数据采集方式的限制，本数据集的多数物种数据不适用于百分比盖度估算，详细说明请参见方法模块中的注释1。