Grassland management regimes alter the coordination of plant functional traits and nutrient resorption in semiarid grasslands

Grazing and enclosure (grazing exclusion) are the main grassland management regimes that affect nutrient cycling and ecosystem function by altering plant traits.  However, the coordination among plant functional traits and nutrient resorption under different grassland management regimes remains unclear. We examined the coordination of eight root and four leaf traits along with the nitrogen (N) and phosphorus (P) resorption efficiencies under four grazing intensities and two enclosure chronosequences in a semiarid steppe ecosystem in China. The principal components analysis (PCA) of root traits and multiple factors analysis of root and leaf traits showed two-dimensional economic spaces at the individual level.  Increasing grazing intensity shifts species and community trait composition from conservative to acquisitive with increases in specific root length, specific root area, root alkaline phosphatase activity, and specific leaf area, accelerating nutrient cycling and coordination among..., Study site
The study was conducted in the Xilin River basin in China’s Inner Mongolia Autonomous Region, in the Sino-German grazing experiment sites and enclosure (grazing exclusion) sites of the Inner Mongolia Grassland Ecosystem Research Station (IMGERS, 43º38'N, 116º42'E, 1260m a.s.l.), affiliated with the Chinese Academy of Sciences.  Here, the mean annual temperature is 0.3°C and the mean annual precipitation is 346.1mm, with precipitation primarily occurring during the main growing season of June to August (Bai et al., 2010).  The dominant species are Stipa grandis, Leymus chinensis, Agropyron cristatum, and Carex korshinskyi.  The soil is classified as dark chestnut (Calcic Chernozem according to ISSS Working Group RB, 1998).
Study design
The grazing experiment site was started in 2005 and has been maintained continuously for 15 years by 2020 (Wan et al., 2011).  The grazing experiment employed a split-split plot design within a randomized complete block encompassing a total area..., , # Grassland management regimes alter the coordination of plant functional traits and nutrient resorption in semiarid grasslands

**Plant functional trait measurements**

We measured twelve plant traits that are related to plant resource economic strategies, following standardized protocols (Pérez-Harguindeguy et al., 2016).  The four leaf traits were measured on the third or fourth leaf, as these leaves are the greatest biomass in the leaf cohorts.  We measured leaf area (LA, cm2) using a Li-3100 (Li-COR, Lincoln, NE, USA). We measured saturated water content after the leaves were immersed in deionized water for 24 hours.  Leaf dry mass was obtained by oven-drying each leaf at 65 °C for 48 hours and then weighing it.  The specific leaf area (SLA, cm2 g-1) was calculated as leaf area divided by its dry biomass.  The leaf dry matter content (LDMC, mg g-1) was water-saturated fresh biomass per unit of dry mass. We measured leaf N (N, mg g-1) and P (P, mg g-1) concentrations with a Kjeltec ...

放牧与围封（禁牧）是两类核心草地管理方式，二者通过改变植物性状调控养分循环与生态系统功能。然而，不同草地管理模式下植物功能性状与养分回收效率之间的协调机制仍未明晰。本研究在中国半干旱草原生态系统中，设置4个放牧强度梯度与2个围封年限序列，测定了8个根系性状、4个叶片性状以及植物氮（N）、磷（P）回收效率，旨在探究二者间的协调关系。对根系性状开展的主成分分析（PCA），以及对根、叶性状开展的多因素分析均显示，植物个体水平存在二维资源经济空间。随着放牧强度升高，物种与群落的性状组成从保守型向获取型转变，具体表现为比根长、比根面积、根系碱性磷酸酶活性与比叶面积均显著提升，进而加速养分循环并强化性状间的协调作用……
研究样地
本实验设于中国内蒙古自治区锡林河流域，隶属于中国科学院的内蒙古草地生态系统研究站（Inner Mongolia Grassland Ecosystem Research Station, IMGERS，43°38'N，116°42'E，海拔1260m）的中德放牧实验样地与围封（禁牧）样地。该区域年平均气温0.3℃，年平均降水量346.1mm，降水主要集中在6-8月的主要生长季（Bai等，2010）。群落优势物种包括大针茅（Stipa grandis）、羊草（Leymus chinensis）、冰草（Agropyron cristatum）与克氏苔草（Carex korshinskyi）。土壤类型为暗栗钙土（依据国际土壤学会RB工作组1998年分类标准，对应Calcic Chernozem）。
实验设计
该放牧实验始于2005年，截至2020年已连续开展15年（Wan等，2011）。实验采用随机完全区组内的裂区-裂区设计，总实验面积……
# 草地管理方式调控半干旱草原植物功能性状与养分回收的协调关系
植物功能性状测定
本研究参照标准化操作规程（Pérez-Harguindeguy等，2016），测定了12个与植物资源经济策略相关的植物功能性状。4个叶片性状均选取叶龄组中生物量占比最高的第3或第4片叶进行测定：使用Li-3100叶面积仪（Li-COR，美国内布拉斯加州林肯市）测定叶面积（LA，cm²）；将叶片浸没于去离子水中24小时后测定饱和含水量；将叶片置于65℃烘箱中烘干48小时后称量得到叶干重；比叶面积（SLA，cm²·g⁻¹）通过叶面积除以叶干生物量计算得到；叶干物质含量（LDMC，mg·g⁻¹）为叶片饱和鲜重与干重的比值。采用凯氏定氮仪（Kjeltec）测定叶片氮（N，mg·g⁻¹）与磷（P，mg·g⁻¹）浓度……