Agricultural Activities of a Meadow Eliminated Plant Litter from the Periphery of a Farmland in Inner Mongolia,China

The purpose of our investigation was to clarify the effects of agriculture on the process of loss of litter at the periphery of a farmland. This study revealed the generation process of an ecologically unusual phenomenon that is observed around cropland in semi-arid regions. We hypothesized that the vegetation around a farmland cannot supply plant litter to the ground surface because the ecological structure has been changed by agricultural activities. The study was conducted at Xilingol steppe, Xilingol League, Inner Mongolia Autonomous Region, China. Four study lines were established from the edge of an arable field to the surrounding meadow and parallel to the wind direction during the strong wind season. Key measurement for each line was set at the border between the farmland and steppe. Four study sites were set at intervals along each line. Plant litter, soil particle size distribution, plant species composition, plant volume, and species diversity were investigated. Despite using the same mowing method at the meadows of all study sites, the litter at the only periphery of the farmland completely disappeared. Soil particle size distribution in steppe, which was adjacent to the farmland, was similar to that of the farmland. Plant community structure at the periphery of the farmland was different from that of the far side from the farmland. This implies that soil scattered from the farmland affected the species composition of the steppe. Consequently, the change in plant community structure induced litter loss because of mowing. We concluded that plant litter was lost near the farmland because of the combined effects of farming and mowing. The results support our hypothesis that the vegetation around a farmland cannot supply plant litter because the ecological structure has been changed by agricultural activities.     

不同放牧强度下克氏针茅(Stipa krylovii)草原的根系特征

以呼伦贝尔克氏针茅草原不同放牧强度下的演替群落为对象,开展群落及其群落建群种的地下生物量和根系形态特征研究.结果表明:从轻度放牧到重度放牧,群落种类组成和根系功能群类型趋于简单化;群落地下生物量的空间分布形态呈“T”型;不同放牧强度下草原群落的建群种出现了明显替代现象,轻度放牧样地群落建群种为密丛型根系的克氏针茅,中度放牧为疏丛型根系的糙隐子草(Cleistogenes squarrosa,重度放牧为鳞茎型根系的碱韭(Allium polyrhizum);随着放牧强度的增大,群落建群种根冠比逐渐增加,分别为0.47、1.0、4.1,并且群落建群种根系数量、根系体积、根系生物量、比根长及根长密度等各指标均发生了明显变化.另外,3种放牧强度样地群落建群种根冠比、根长密度均与土壤速效氮含量呈现显著正相关(P＜0.05).     

锡林郭勒草原景观多样性的时间变化

利用锡林郭勒草原典型区段的两个不同年代的遥感信息源,结合实地考察目视解释研究区１９７８年（ＭＳＳ）、１９９２年（ＴＭ）的卫片影像,得到研究两张不同时期的植被图,以植物群落做为确定景观单元的最主要因子,在ＡＲＣ／ＩＮＦＯ软件的支持下,通过景观元素空间格局的变化,进一步分析得出在１４ａ的时间进程中,研究区景观破碎花现象加剧,多样性指数增加,优势度指数下降,人类不合理的放牧利用、农田开展等经营活动,引起     

内蒙古草甸草原地下芽库对极端干旱的响应

全球变化引发的极端气候事件严重影响草地生态系统结构与功能。然而,作为多年生草地重要繁殖体库,半干旱草甸草原地下芽库如何响应极端干旱尚未明确。本研究以内蒙古呼伦贝尔草甸草原为对象,利用模拟极端干旱样地平台,探究地下芽库及其与地上植被关系对模拟生长季极端干旱的响应。结果表明,环境降水水平与干旱处理下总芽密度分别为1443和1128芽·m^-2;分株总密度分别为1791和1346株·m^-2;群落整体分生组织制约系数分别为0.84和0.83。极端干旱对草甸草原地下芽库、地上分株密度以及二者之间关联均无显著影响。就优势植物功能群根茎型禾草而言,极端干旱对其地下芽库同样无显著影响。因此,地下芽库表现出对极端干旱一定程度的抵抗力,可作为草甸草原植被应对极端气候事件的保险策略,有效促进草甸草原在极端气候胁迫下的种群更新与植被恢复,有助于草甸草原植被稳定性与生态系统功能维持。     

克氏针茅草原植物叶片性状对放牧强度的响应

放牧干扰是影响草地植物性状的方式之一,植物叶片性状能够客观反映植物对生长环境的适应性.本文以呼伦贝尔克氏针茅草原不同放牧强度的样地为研究区,探讨叶片性状间的相互关系及在不同放牧梯度上和不同生活型功能群之间的变化规律.结果表明:克氏针茅草原植物的主要叶片性状在不同生活型植物之间差异均不显著,但是各个性状之间的相关性较强.在放牧梯度上,重度放牧样地上叶片磷含量和氮磷比值与中度放牧区和轻度放牧区有显著差异;在生活型功能群分类中,放牧对多年生杂草的叶片磷含量和氮磷比值有显著影响,表明多年生杂草对放牧较为敏感,重度放牧改变了植物养分利用策略.合理放牧可以改善克氏针茅草原植物养分性状并有利于遏制草原的退化.     

Changes of plant N:P stoichiometry across a 3000-km aridity transect in grasslands of northern China

Plant and Soil - Rice cultivars bred for fertile soils may not be the best suited to nutrient limited environments. Therefore, rice cultivars suited to sustain productivity in low-fertile soils and...