毛乌素沙地土地利用/覆被变化对草地土壤物理、化学和矿物学性质的影响

In arid and semiarid regions, cultivation and shrub invasion are two important factors to impact grassland. However, there are few studies to compare the effects of cultivation and shrub invasion on soil physical, chemical and mineralogical properties. In this study, three sampling sites, which respectively represent the native grassland, cultivated grassland (farmland), and shrub invasion of grassland (shrub land) in Mu Us sand land, were selected and soil samples were collected and measured for soil particle size distribution (PSD), soil organic carbon (SOC), total nitrogen (TN) and total phosphorous (TP) concentrations, and relative percentages of mineralogical components. Results showed that cultivation and shrub invasion significantly altered the soil PSD, soil C, N and P concentrations and pools, and the relative percentages of soil mineralogical components of the grassland ecosystems. Grassland cultivation and shrub invasion significantly decreased the contents of silt and clay. Moreover, the land cover change from grassland to farmland or shrubland significantly resulted in soil organic carbon, total nitrogen and soil carbonate loss. In this study, we found that grassland cultivation resulted in more sand accumulation and more soil C and N losses than shrub invasion, which indicated that grassland cultivation was stronger than shrub invasion to accelerate soil desertification in Mu Us sand land.     

河西走廊灌丛植被的生态学研究

本文从生态学基本原理出发 ,对河西走廊灌丛植被以群落建群种为基础进行了分类研究 ,将灌丛植被划分为 8个类型 ,分别对灌丛群落的分布、生物学特性、生态学意义以及各类灌丛植被与土壤之间的关系 ,特别是对灌丛植被在改善河西走廊生态环境的作用、在干旱荒漠系统的防风固沙、建立荒漠草场以及防治荒漠化等方面进行了研究 ,并就河西走廊荒漠系统生态重建与可持续发展提出了对策     

Mechanisms Providing for Species Coexistence in the Herb-Dwarf Shrub Layer of a Southern Taiga Birch Forest

Individual species coexisting in the herb-dwarf shrub layer of a mature southern taiga birch forest were studied with respect to their limitation by different environmental resources and differences in the time or localization of the intensive utilization of deficient resources. The results made it possible to estimate the significance of different mechanisms of species coexistence in multispecific communities for herbaceous and dwarf shrub species of the forest phytocenosis studied.     

Microecosystem Analysis of the Structure and Functions of Forest Biogeocenoses

The microecosystem approach and an adequate system of quantitative methods have been used to study the relationship between the chorologic changes in the structure and functions of edificator tree stand and other components of the pine (Pinus sylvestris L.) forest cenoecosystems of the Transural and Northern Turgai regions. Significant correlations of the density of pine undergrowth with the litter thickness; of its growth with root competition, stand closeness, and, to a lower degree, photosynthetically active radiation (PAR); and of the numbers of small mammals and groups of soil mesofauna with herbaceous phytomass have been found. The possibility of the synthesis of population-ecological, synecological, and biogeocenological methods has been demonstrated.     

毛乌素沙地灌木资源区系特征及其保护对策

本文基于对毛乌素沙地的植被调查,分析了该区灌木区系的科、属组成,地理成分,生活型和生态习性,以及灌丛在这一特殊地理生态过渡带的重要地位。在此基础上提出了灌木资源多样性保护和恢复的对策。     

冀北山地绣线菊灌丛的土壤种子库特征

为了了解冀北山地退化植被--绣线菊（Spiraea pubescens）灌丛的生态恢复潜力,采用种子萌发法对其可萌发土壤种子库进行了研究,并与其他群落类型进行了比较。结果表明,绣线菊灌丛种子库的种子密度为4 013.33 粒/m²,低于华北落叶松（Larix gmelinii）人工林（4 646.67 粒/m²）,但高于榛子（Corylus heterophylla）灌丛（1 713.33 粒/m²）和天然次生白桦（Betula platyphylla）林（746.67 粒/m²）;绣线菊灌丛土壤种子库以草本植物为主,没有发现乔木和灌木种子。各群落类型土壤种子库的种子密度有随土壤深度的增加以及坡位的上升而下降的趋势。绣线菊灌丛土壤种子库的物种组成与其他3 种群落类型具有一定的相似性,但低于其他三种群落之间的相似程度。由此得出结论,绣线菊灌丛具有数量庞大的草本植物种子库,群落草本层恢复潜力巨大,但木本植物,尤其是乔木较少,这是限制绣线菊灌丛向森林群落演替的主要限制因素,需要通过人工的方法引入乔木树种,加速群落的演替,促进森林植被的恢复。     

土壤水分植被承载力研究成果在实践中的应用

论文以黄土高原半干旱区柠条林为例,探讨了土壤水分植被承载力研究成果在生产中的应用。结果表明,土壤水分植被承载力不仅是确定森林植被恢复目标、调控植物水关系的理论基础,而且是确定森林植被合理经营方向和利用强度的理论基础。如果人工林密度大于土壤水分承载力,需要对人工林进行疏伐;如果人工林密度小于土壤水分承载力,需要增加密度或改换植被类型。当人工林密度等于土壤水分承载力时,人工林可持续利用土壤水资源。土壤水分承载力时的柠条林可以作为薪炭林和放牧林经营。单位面积结实量与密度关系可用正态分布曲线描述。承载力时的柠条林不仅能有效地保持水土,而且能生产较多的种子,又是良好的蜜源植物,宜作为水土保持林经营。该研究结果可为人工植被恢复和可持续经营提供科技支撑。     

岩溶区典型灌丛植物根系丛枝菌根真菌群落结构解析

运用末端限制性片段长度多态性T-RFLP法(terminal restriction fragment length polymorphism),检测岩溶区典型13种灌丛植物根系丛枝菌根(arbuscular mycorrhizal,AM)群落结构变化特征,探讨岩溶区AM与宿主植物是否存在选择特性.结果表明,不同灌丛植物根际土壤养分存在显著差异,豆科植物显著高于非豆科植物.聚类分析表明,13种灌丛植物均能被AM侵染,不同灌丛植物根系AM群落结构存在显著差异,尤其豆科与非豆科植物,但AM群落结构在9种非豆科植物间差异显著而在4种豆科植物间则差异不显著.冗余分析表明,影响豆科与非豆科植物根系AM群落结构的因子各异,土壤Olsen-P、p H和全氮是影响岩溶区灌丛植物根系AM群落组成结构的主要因子.研究还表明,岩溶区灌丛植物根系AM与宿主植物具有选择特性,这种选择特性出现在植物功能群的几率比植物种类大,将AM应用于岩溶区植物恢复时,应考虑AM与宿主植物的选择特性问题.     

Spatial Patterns of Soil Moisture as Affected by Shrubs, in Different Climatic Conditions

At three study sites, representing Mediterranean, semi-aridand mildly-arid climatic conditions, the effect of shrubs onthe spatial patterns of soil moisture was studied. At eachsite soil moisture was measured, on hillslopes, at thevicinity of 8 shrubs. For each shrub the measurements havebeen taken at 3 microenvironments, i.e. under the shrub (US),at the margins of shrub (MS) and between shrubs (BS). At themicroenvironments US and MS the measurements were taken at 3 directions: upslope, downslope and sideslope of the shrubs. At all sampling points soil samples were taken from 3 depths: 0–2, 2–5 and 5–10 cm. In addition, rock fragments cover percentage near the shrubs was determined. A soil moisture pattern was found, around each shrub,which is composed of a radial gradient and a downslope gradient. The radial gradient is expressed by soil moisture decreasingfrom the US microenvironment, in all directions, through the MS towards the BS microenvironment. The US microenvironmenthas a `spatial advantage' of higher soil moisture content dueto (1) relatively higher infiltration rate, (2) capture overlandflow from the BS area upslope that shrub and (3) low evaporationrate because of the shading effect.The downslope gradient is expressed by decreasing soil moisturefrom the upslope direction of each shrub (MS and US microenvironments) towards the downslope direction of that shrub (MS and US microenvironments, respectively). Thisgradient is controlled by the relatively high content of rockfragments near the shrubs at their upslope direction. Suchrock fragments spatial distribution is attributed to (1) thedetachment and transport of rock fragments by sheep and goatstrampling and (2) the effect of shrub on the continuity ofoverland flow and sediment transport. The effect of rockfragments is similar to that of shrubs regarding increasinginfiltration and decreasing evaporation rate. The relativelyhigh soil moisture at the upslope direction of each shrubenhances annuals growth producing a positive feedback loop:soil moisture – annuals growth – trampling. This sequencemaintains the typical rock fragments spatial organization andcontributes to the sustainability of the grazing system.At all the study sites at the US microenvironment there isa trend of decreasing soil moisture with increasing soildepth. At microenvironments MS and BS soil moisture increaseswith soil depth.The results are of great relevance for rehabilitationstrategies as they suggest that in order to combatdesertification in degraded semi-arid and mildly-arid areas,where the main land use is grazing, both shrubs and rockfragment should be kept at their present spatial distribution.     

黄土高原3种锦鸡儿种子萌发对温度的响应

锦鸡儿属(Caragana Fabr．)植物是黄土高原植被的重要组分，对维持生态系统的功能具有重要作用，在黄土高原的植被恢复中具有重要意义．外来种中间锦鸡儿(C．intermedia Kuang et H．C．Fu)和乡土种白毛锦鸡儿(C．1icen-tiana Hand-Mazz)、甘蒙锦鸡儿(Caragana opulerts Kom．)种子在室内5℃、10℃、15℃、20℃、25℃、30℃恒温及10℃／5℃、25℃／15℃、30℃／20℃、35℃／20℃昼(10h)／夜(14h)的变化温度下培养．结果表明，中间锦鸡儿适于萌发的温度范围最为宽泛，为5℃到30℃，萌发率普遍较高．甘蒙锦鸡儿适于萌发的温度在30℃以下，萌发率很高，大部分为100％，5℃下仍有较高的萌发率．而白毛锦鸡儿适于萌发的温度范围相对较窄，萌发率普遍较低，5℃时种子不萌发．昼／夜温度变化对3种锦鸡儿种子萌发的影响不大．从萌发速度来看，中间锦鸡儿倾向于适宜温度范围内在很短时间内很快完成萌发，高温下萌发速度更快，另有0．8％的硬实种子．白毛锦鸡儿萌发速度最慢，呈现每次都有少部分种子萌发的格局，另外有5．1％的硬实种子进入持久种子库．而甘蒙锦鸡儿的萌发速度介于二者之间，且没有硬实种子．3种锦鸡儿种子萌发格局与其地带性分布和生境有关，萌发格局的不同也揭示了这3种锦鸡儿在不同生境下的繁殖更新策略．图2表1参17