退化沙质草地土壤种子库和地上植被对封育的响应机理

从植物种和植物功能类群两个水平系统探讨退化沙质草地土壤种子库和地上植被对短期封育管理响应机理的研究尚不多。以内蒙古东部的科尔沁沙地退化沙质草地为研究对象,采取随机样方法对禁牧6 a的封育区及与其相邻的自由放牧草地的土壤种子库和地上植物群落的物种密度进行了比较研究,草本植物群落被区分为一年生禾本科植物、非禾本科一年生植物和多年生植物3个主要功能类群。利用测定数据,分析研究了短期禁牧封育对土壤种子库和地上群落不同植物种和各植物功能类群的生态恢复作用机理。主要研究结果是：①短期封育显著促进了退化沙质草地植被的生态恢复,但发现土壤种子库和地上植被对禁牧的响应模式和机理存在明显差异,短期禁牧使土壤种子库中所有3个植物功能类群的密度均得到显著提高,而仅提高了地上植被一年生禾本科植物和多年生植物两个类群的密度;相反,禁牧显著提高了地上植被所有3个功能类群的物种丰富度和多样性,仅提高了土壤种子库中多年生植物类群的物种多样性。②短期禁牧显著增加了地上植物群落组成中可食和优良牧草的比例,提高了草地的经济利用价值。主要结论是：短期禁牧封育是一种经济有效的提高退化沙质草地植被多样性、生产力及对植物群落物种组成和草地品质进行优化调控和改良的重要草地管理手段。研究建议,今后应重点开展不同禁牧时间下对退化沙质草地土壤种子库和地上植被多样性、生产力及其物种组成变化影响的长期生态学控制实验研究。     

塔里木河下游荒漠化过程土壤种子库特征

沿塔里木河下游荒漠河岸林,选择了荒漠化程度依次加重的5个断面,进行了土壤种子库野外萌发试验。结果表明:①在中度荒漠化区土壤种子库的物种相对丰富(11种),密度较高(892.6粒\5m-2);随着荒漠化程度的加剧,土壤种子库物种丰富度、总密度以及多样性指数呈现出明显下降的趋势;②与重度荒漠化区和中度荒漠化区相比,极度荒漠化区土壤种子库中的多年生草本和灌木密度占总密度的百分比有所增加,一年生草本百分比明显降低;③不同荒漠化程度对种子库密度的垂直分布影响不大,70%以上的种子集中在土壤表层0～2 cm深度。综合来看,随着荒漠化程度的加剧,土壤种子库的恢复潜力有所下降。     

太白山土壤种子库储量与物种多样性的垂直格局

通过野外植被调查和室内试验,从1 220份土样中,挑选土壤中的种子,进行分类统计,研究秦岭太白山南坡土壤种子库储量与物种多样性沿海拔梯度的变化。研究结果如下：(1) 太白山南坡土壤种子库中的植物种为172种;从总体上看,土壤种子库中的物种丰富度 (S) 随着海拔的上升呈下降趋势。土壤种子库生物多样性特征表现为在2个海拔段发生较明显的变化：一是从低海拔到中等海拔 (1 500~2 500 m),二是从中等海拔到高海拔 (2 500~3 500 m)。在?琢多样性方面,生态优势度在海拔2 500 m处最大;在海拔2 400 m以下 (包含2 400 m) 的样地中,种子库生态优势度大于海拔2 500 m以上 (含2 500 m) 的样地种子库的生态优势度。 H′(Shannon-Wiener指数)与生态优势度的变化趋势相反。(2) 太白山南坡土壤种子库储量最大值出现在海拔2 600 m的样地,为2.24×104 Ind./m²;种子库储量最小值出现在海拔3 500 m的样地,为4.43×102 Ind./m²。储量沿海拔梯度的变化趋势表现为：在海拔2 600 m以下,种子库储量沿海拔的上升呈逐渐增加的趋势;在海拔2 600 m以上,种子库储量沿海拔的上升呈逐渐下降的趋势。(3) 土壤种子库的种子储量与种子密度的变化规律基本一致。而用单位面积土壤中的种子储量来表示种子库的大小特征比用种子密度来表示更为实用和方便,而且采集具有不同性质的土壤研究种子库,考虑到了土壤性质等因素的影响,更能客观反映土壤种子库的特点。     

春夏季放牧对古尔班通古特沙漠南部土壤种子库和地上植被的影响

位于新疆北部准噶尔盆地腹地的古尔班通古特沙漠,是世界上温带荒漠生物多样性的精华和最为丰富的典型区域。历史上这里就是北疆羊和部分马匹重要的冬牧场,但近年来的放牧活动在春夏季也开始进入沙漠腹地,使地表性质与植被覆盖发生了明显改变。应用野外随机取样与室内萌发实验相结合的方法,对比研究了古尔班通古特沙漠南部春夏季放牧和冬季放牧沙垄土壤种子库差异及其与地上植被的关系。结果表明：冬季放牧沙垄种子库种数为24种,而春夏季放牧沙垄有20种,后者明显减少了植物种数。冬季放牧沙垄种子库密度为(353.2±87)粒·m-2,而春夏季放牧沙垄为(189.1±23)粒·m-2,比前者减少了88%。两类沙垄土壤种子库的生活型组成都以一年生植物为主,相似性系数为0.711。相同沙垄不同部位的物种相似性系数在0.429～0.600之间,异质性较大,尤其表现在除垄顶之外的其他部位。冬季放牧沙垄和春夏季放牧沙垄地上植被中分别有植物36种和26种,各生活型所有物种均为后者低于前者,其中短命、类短命物种数量减少幅度最大。春夏季放牧沙垄地上植被的物种多样性和均匀度降低,而优势度升高。回归分析显示,冬季放牧沙垄定植群落有21%的变异来源于土壤种子库,而春夏季放牧沙垄有51%的变异来源于土壤种子库,可见不同季节的放牧干扰显著影响土壤种子库及其与地上植被的相关关系。     

岷江上游毛榛、辽东栎灌丛及3种人工幼林土壤种子库的比较

本文采用野外调查与萌发实验相结合的方法对岷江上游地区自然恢复的灌丛以及 3种人工林的土壤种子库状况进行了比较研究。结果显示 ,各样地土壤种子库的储量为 192 5 0～ 3 13 60粒 /(m2 × 10cm)之间 ,人工林的土壤种子库储量和物种数量都大于自然恢复的灌丛 ,其顺序为连香树Cercidiphyllum japonicum、油松Pinustabulaeformis混交林 >连香树林 >油松林 >毛榛Corylusmandshurica、辽东栎Quercusliaotungensis灌丛 ,各样地土壤种子库密度的垂直分布均为上层 >中层 >下层。在各样地土壤种子库的生活型组成中 ,乔木种类所占比例极少 ,而草本种类的数量较多。在灌丛的土壤种子库中 ,灌木的物种数量及其在种子库中所占的比例均大于人工林。大序醉鱼草Buddlejamacrostachya、喜阴悬钩子Rubusmesogaeus、华西绣线菊Spiraealaeta在种子库中的大量存在明显提高了灌木在各样地土壤种子库中所占的比例     

Factors controlling regeneration in a rare desert tree Acacia peuce: Limits to soil seed bank accumulation in time and space

We assessed reasons for rare recruitment in Acacia peuce, an Australian arid zone tree, by testing recruitment-limitation hypotheses relating to seed bank inputs and losses. Viable seed occurred in low density in the soil (<1 seed m²) whereas freshly produced seed was non-dormant and germination was high and fast, indicating small rain events can deplete seed banks without providing sufficient moisture for seedling survival. Seed bank seed had lower viability than fresh seed. Insect predation of seed was negligible but seed pod production and seed number/pod were low. Thus, seed bank accumulation is limited by low inputs and continual high seed losses through germination and potentially seed death. No seed shadow effect under adult canopies was found, but dispersal beyond existing stands was negligible. Seed dispersal from parent plants occurred by wind movement of unopened pods whereas the resident ant fauna did not transport seed. Microsite parameters strongly influenced horizontal distribution of buried seed, with all seed being retrieved from vegetated sandy mounds. Overall, we found that seedling recruitment is likely to be confined to large above average rainfall events because the species is unlikely to maintain a seed bank in below-average and average rainfall phases.     

Cattle grazing effects on annual plants assemblages in the Central Monte Desert,Argentina

Plant assemblages' dynamics have been studied to evaluate the influence of different environmental factors. The aim of our work was to assess the effect of a disturbance in the form of livestock grazing on annual plants, in a South American desert. We tested the exclusion of cattle grazing by comparing the composition of annual plants in three major vegetation types within a MaB Reserve in the Monte Desert of Argentina, with those of an adjacent grazed field. Sampling was conducted in two consecutive years that differed in precipitation. We established three sampling sites within each vegetation type at the reserve and the grazed field. Transects were set to assess plant cover, abundance, and richness. Theoretically, changes in diversity are explained by changes in one of its components: species richness. Species richness of annual plants was not different between the grazed and ungrazed sites. However, plant cover and diversity were lower in grazed sites, whereas abundance increased. Owing to a strong species-specific effect, we propose that it is evenness the main parameter involved in diversity dynamics in the heterogeneous vegetation mosaic of the Monte desert. Finally, vegetation types (spatial heterogeneity) and rainfall regime (temporal heterogeneity) greatly interacted with grazing effects. We endorse the idea that rapid responses of annual plant assemblages to changes in rainfall conditions coupled with herbivore control, might result in a restoration pathway for degraded arid landscapes.     

天然固定沙地与人工固沙植被区土壤种子库的比较研究

土壤种子库是退化生态系统植被恢复重建的重要基础,研究土壤种子库特征对于阐明退化生态系统受损与恢复机理具有重要的科学意义。通过野外土样采集、野外种子萌发定位跟踪调查和室内周期性种子萌发实验,对腾格里沙漠东南缘人工固沙植被区和天然固定沙地的土壤种子库特征进行了对比研究。结果表明：人工固沙植被区土壤种子库包含21个物种,分属于8科;天然固定沙地土壤种子库有33种植物,属于11科。人工固沙植被区以一年生植物为主,天然固定沙地以多年生植物为主。人工固沙植被区的种子总密度明显低于天然固定沙地,但不同物种种子的密度变化存在显著差异。人工固沙植被区的物种丰富度和多样性指数均较天然固定沙地低。人工固沙植被区和天然固定沙地的土壤种子库与地上植被物种的相似性系数分别为0.73和0.71。尽管人工固沙植被区土壤种子库存在少量多年生植物种子,但仍未发展到以多年生草本植物为主的群落演替阶段,说明人工固沙植被区的植物多样性恢复尚需要漫长的过程。     

土地利用方式对岩溶山地土壤种子库的影响

本文从种类组成、种子数量、生态优势度、物种多样性、种子分布规律和物种相似性等方面比较了重庆市岩溶低山10种不同土地利用系统的土壤种子库特点，10种土地利用类型包括耕地、弃耕地、果园、灌草坡、人工林和次生林。结果表明，研究区种子以草本为主，随土利用强度增加，种子类和数量减少，与地面农田杂草相似性增加，土壤种子库出质和量方面的锐减。从土壤种子角度说明研究区生态退化严重。     

Influence of aboveground vegetation on seed bank composition and distribution in a Great Basin Desert sagebrush community

The quantity, composition, and spatial dispersion of seed banks can greatly affect community dynamics. While seed banks of hot deserts have been studied extensively, little is known about seed banks in cold deserts, in particular the relationship between the seed bank and the aboveground vegetation. We investigated the relationship between the seed bank and aboveground vegetation and the effect of microhabitat (shrub interspace or beneath shrub) and aboveground community phase (high or low perennial bunchgrass cover) on the seed bank of a Great Basin Desert sagebrush community. The seed bank and aboveground vegetation differed in their most dominant species, resulting in moderately dissimilar species compositions as determined by Sørensen's similarity index and Bray–Curtis distance. In contrast, comparing the seed bank species composition to the aboveground vegetation structure (functional groups) using non-metric multidimensional scaling (NMDS) revealed a correspondence between the two communities. Shrub seed densities were higher beneath shrubs. Neither microhabitat nor community phase explained variation in total seed density or species richness. Therefore, our measures of the aboveground vegetation did not influence seed density across functional groups or species richness, and the similarity between the seed bank and aboveground vegetation varied depending on the aboveground organizational level used in comparisons.     

阿拉善高原荒漠植被组成分布特征及其环境解释 Ⅳ.土壤种子库特征研究

阿拉善荒漠土壤种子库种子密度主要受到水、热变化梯度的影响而呈现水平地带性分布规律。土壤种子库的分布主要集中在0～5cm的土层中,深层土壤很少有种子库的存在。阿拉善土壤种子库共统计到26种植物种子,分属9科22属,以禾本科最多;生活型以一年生草本植物种子的比例最高,达到51.36%。极端干旱环境条件下不存在有效的土壤种子库。土壤种子库多样性(Simpson指数)在东阿拉善草原化荒漠区为最高,在0.546～0.917之间;西阿拉善荒漠区次之为0.417～0.915;额济纳绿洲区为0.855,说明阿拉善荒漠区从东到西,土壤种子库物种多样性指数呈现下降的趋势。土壤种子库相似性研究表明,阿拉善荒漠不同区域的土壤种子库相似性差异较大,东阿拉善荒漠化草原植被区,相似性系数范围为0.17～0.67,西阿拉善典型荒漠区为0～0.75,额济纳戈壁荒漠区和东、西阿拉善土壤种子库的相似性系数范围是0～0.4。说明阿拉善荒漠区,由于生境和植被的异质性程度高,导致土壤种子库之间的差异性显著。阿拉善荒漠的土壤种子库和地上植被组成上差异显著,地上植被的优势种以旱生、中生灌木、半灌木为主,土壤种子库中以一年生、多年生草本为主,没有统计到灌木种子的存在,表明土壤种子库对于灌木层片更新和演替的贡献非常小。这些发现对了解干旱荒漠植被自然修复特点具有重要的潜在贡献。     

Assessment of grazing effect on sheep fescue (Festuca valesiaca) dominated steppe rangelands, in the semi-arid Central Anatolian region of Turkey

In the semi-arid steppe rangelands of Central Turkey, Festuca valesiaca and Thymus sipyleus ssp rosulans have become the dominant species on degraded pastures. We hypothesized that decreases in species richness and abundance are correlated with increasing prevalence of these two species. Therefore, our objectives were to determine whether there are patterns in examined vegetation; how dominant species contribute to these patterns; and how patterns differ between grazed and ungrazed vegetation. We determined that protection from grazing increased species richness. Grazing significantly changed composition through decreasing total plant, forb, grass and F. valesiaca covers, while substantially increasing T. sipyleus cover. Topography, soil and grazing appear to impact the dominance of plant communities where F. valesiaca and T. sipyleus prevail. These two dominant species had a significant effect in shaping vegetation patterns. Based on regression analysis, alterations in species richness with changes in cover of forbs and shrubs were evident, and spatial heterogeneity of F. valesiaca and T. sipyleus indicated unstable vegetative patterns in heavily grazed pastures and successional changes in protected pastures. Our study results identify F. valesiaca and T. sipyleus as indicator species of vegetation suppression in condition assessments of degraded steppe rangelands.     

Soil seed flora, germination and regeneration pattern of woody species in an Acacia woodland of the Rift Valley in Ethiopia

The objectives of this study were to determine the composition, density and spatial distribution of the soil seed bank of woody species, as well as their regeneration pattern in two different land use systems, controlled (ranch) and open grazing, in an Acacia woodland of the Rift Valley in Ethiopia. We also compared the species composition of the soil seed bank and the above-ground vegetation to find out if differences exist in the soil seed bank and advance regeneration between the two land use systems. The germination requirements of seeds of the woody species were also investigated under laboratory conditions. Acacia senegal, Acacia seyal, Acacia tortilis, Dichrostacys cinerea and Balanites aegyptiaca were encountered in the above-ground vegetation in both systems. Seeds of only A. tortilis (90±32 seeds m⁻²) from the ranch, and A. senegal (5±3 seeds m⁻²) and A. tortilis (72±34 seeds m⁻²) from the open system were found in the soil seed bank along transects with patchy horizontal pattern. The two systems were not significantly different in density of soil seed banks of A. senegal andA. tortilis . Jaccard's similarity index showed that only a few woody species were common in the soil seed flora and above ground vegetation. However, all of the species accumulated seeds (58±43–331±130 seeds m⁻²) in/on the soil under the canopy. Very large numbers of seeds of A. tortilis (19382±9722 seeds m⁻²) and D. cinerea (1278±494 seeds m⁻²) were also found in barns. Most of the seeds recovered from the soil samples (60–80%) were found in the litter layer. Acid and mechanical scarification improved legume germination (36–99% and 60–99%, respectively) over boiling water (0–48%). Treatment means differed significantly for all the legumes (p<0·001) but not for Balanites. Height and diameter class distribution of regeneration of A. tortilis and D. cinerea in both systems and A. senegal in the open system had a negative exponential correlation (r_s=−0·5, −0·25 and −0·86, respectively). A. seyal and B. aegyptiaca showed poor regeneration. Horizontal distribution of advance regeneration of all the species was patchy. Advance regeneration of A. seyal, A. tortilis and B. aegyptiaca were not significantly different, while that of A. senegal and D. cinerea were significantly different between the two systems. Poor representation of species in the soil seed bank along transects and in the different height and diameter classes may be attributed to the low density of mature trees as well as the mode and strategy of seed dispersal. Ungulate and wind dispersed species (e.g. A. senegal, A. tortilis and D. cinerea) were highly favoured. Patchiness in the distribution of seeds and advance regeneration was also a result of endozoochory. Dispersal of non-ungulate dispersed seeds (A. senegal, A. seyal and B. aegyptiaca) was restricted to the canopy zone. Piles of seeds ofA. tortilis and D. cinerea that were found in barns were a result of consumption of their pods by cattle. High concentration of seeds in the litter layer may be due to low soil disturbance and larger size of seeds. The height and diameter class distribution of A. senegal (in the open system), A. tortilis and D. cinerea also indicated that the species have good regeneration. Results from the germination tests indicated that seeds of the legumes require pre-sowing treatments to give a rapid, uniform and improved germination. Intervention through artificial regeneration should be employed to improve the density and regeneration capacity of those species with hampered regeneration at both systems.     

片断化热带雨林土壤种子库初步研究

通过萌发实验研究片断化热带雨林的森林土壤种子库的储量、种类组成以及种子的分布。结果表明,在厚度为10cm的土壤中,受次生植被隔离的城子龙山雨林片段土壤种子库储量达到6494±155粒/m2,高于连续森林的4585±235粒/m2。而受人工植被隔离的曼仰广龙山雨林片段由于缺乏种源,土壤种子库储量较低,仅达到3505±43粒/m2。土壤种子库中的种子种类也以城子龙山为最多,达到69种。从土壤种子库的水平分布看,受次生植被影响的城子龙山和迁地保护区从林缘至林内种子储量呈下降的趋势,而需子龙山隔离程度较高、受人畜干扰严重,森林内外土壤种子库储量显差异不显著。     

Seasonal variation of the soil seed bank of grasses in central Argentina as related to grazing and shrub cover

The objectives of this research were to (a) study seasonal variation of the seed bank of grasses in two areas with different grazing history, (b) analyse the effect of the presence of shrubs on the seed bank and (c) study seed viability and dormancy in buried seeds of Piptochaetium napostaense and Stipa tenuis. The seed density of grasses was in general low and showed seasonal variation. Most of the grasses showed maximum seed density in December when seed dispersal occurs. Shrub cover did not show a marked influence in seed accumulation. The relatively high number of damaged seeds suggests that predation may be an important factor in seed bank dynamics in the Caldenal. Seeds of dominant perennial forage grasses showed dormancy that could explain, at least in part, persistence of these species in spite of periodical disturbance.     

微生境尺度上放牧退化草原群落特征与土壤有机质的空间分异性

 格局和过程与异质性有关。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,开展群落植被空间分布格局及土壤有机质空间异质性研究。结果显示,不同放牧强度样地群落结构和群落种类组成存在明显差异。轻度放牧样地样方内有8种植物,群落优势种为克氏针茅（Stipa krylovii）;中度放牧样地样方内有12种植物,群落优势种为糙隐子草（Cleistogenes squyarrosa）;而重度放牧样地样方内只有7种植物,群落优势种为多根葱（Allium polyrhizum）。随放牧强度的增强,植被地上生物量及其变异系数逐渐降低;土壤有机质含量表现为轻度放牧>中度放牧>重度放牧,而其变异系数表现为中度放牧>轻度放牧>重度放牧。从植被地上生物量和土壤有机质含量变异函数分析来看,随放牧压力的增大,植被地上生物量空间自相关性增强,空间异质性变大;土壤有机质含量空间分布自相关性先增强,然后减弱,空间变异性先变大,然后变小。在10 cm×10 cm的微尺度上,重牧群落植被地上生物量和土壤有机质含量之间表现出明显的相关性（P<0.05）。     

石羊河上游干旱草原星毛委陵菜群落土壤种子库

星毛委陵菜(Potentilla aclaulis)被认为是阻止草原进一步退化的一道"绿色屏障",其群落土壤种子库的退化机制能够为草地生态恢复提供依据.通过大面积调查,研究了石羊河上游干旱草原退化演替过程中星毛委陵菜群落的土壤种子库,结果表明,土壤种子库共有19个物种,分属14个科;随着星毛委陵菜种群分盖度的增加,种子库种类及密度呈递减趋势,禾本科的密度减少,不食草种类减少,但是密度增大;在垂直方向上,种子库的种类逐层减少,密度出现0～5 cm>10～15 cm>5～10 cm的变化趋势;星毛委陵菜种子库很小,只占2.93%,其再生途径倾向于无性繁殖;种子库和地上植被的相似性指数平均为0.392,土壤种子库中没有发现原生地带性植被优势种群的种子,反映了草地群落退化的不可逆转性.     

塔里木河下游退化荒漠河岸林地上植被与土壤种子库关系初探

以塔里木河下游为研究区,选择退化程度不同的4个典型断面19个样地,利用种子萌发法进行了两年的种子库土壤萌发实验,试图就生态严重退化区的土壤种子库与地上植被的关系以及退化程度的差异对种子库特征的影响开展针对性的研究。结果显示: ①塔里木河下游土壤种子库的基本特征是:种子库密度小、物种种类组成较单一、物种的多样性低和地上植被与种子库的相似性较低;②随退化程度的加剧,土壤种子库密度明显下降、表层种子库比例升高、一年生草本占优势逐渐向多年生草本和灌木转变、地上植被与土壤种子库物种组成上差异显著;③退化过程中种子库多样性的变化比地上植被变化要迟缓,但是在植被退化演替的末期,土壤种子库的物种多样性指数衰减的幅度又明显快于地上植被的衰减幅度;④受干旱环境和严重退化的双重影响塔里木河下游土壤种子库与地上植被的关系表现出退化演替末期共有物种数的减少和相似性明显递减的特点。     

Effects of grazing and climate change on species diversity in sandy grassland, Inner Mongolia, China

To understand the effects of animal grazing activities and climate change on sandy grassland vegetation in northern China, a field grazing and protected enclosure experiment was conducted from 1992 through 2006 in Horqin Sand Land, Inner Mongolia. The results showed that (1) the grazing was primary responsible for changes of the vegetation richness and diversity in the grazing grassland and that changing climate was the main reason for changes in the species richness and diversity in the grassland protected from grazing; (2) light and moderate grazing can promote restoration of the richness and the diversity in the degraded grassland, and heavy grazing could result in a decrease of the richness and diversity; (3) heavy grazing can result in significant decrease of the perennial diversity, and moderate and light grazing promotes increase of the perennial diversity; the grazing, whether heavy or moderate and light grazing, was beneficial to increase of the annual diversity; (4) heavy grazing was not beneficial to diversity of Graminean and Chenopodiaceae, and moderate and light grazing was favorable the diversity of Compositae and Chenopodiaceae; (5) the warm-humid climate was favorable to increase of the richness and the diversity, and the warm-drought climate could result in decease of the richness and the diversity; (6) increased precipitation was favorable to perennial diversity and the diversity of Graminean, Leguminosae, and Compositae, and decreased precipitation had few effects on the annual diversity and Chenopodiaceae diversity.     

放牧强度对科尔沁沙地沙质草地植被的影响

为了研究科尔沁沙地沙质草地在不同放牧强度下植被特征的变化规律,比较了围封、中度放牧、重度放牧3种条件下的植被盖度、群落组成、物种多样性、地上/地下生物量和凋落物量等植被特征的变化特征。结果表明:(1)围封、中度放牧和重度放牧沙质草地的优势植物均为一年生植物,但围封和中度放牧中多年生禾本科植物优势度高于重度放牧,重度放牧沙质草地一年生植物所占优势度最大;(2)放牧强度对沙质草地植被盖度、地上生物量及凋落物量有显著影响。随着放牧强度的增加,植被盖度、地上生物量和凋落物量均降低;(3)围封、中度放牧和重度放牧沙质草地物种丰富度及多样性差异均不显著;(4)放牧强度和土壤深度及其交互作用均能影响地下生物量。随着放牧强度的增加,总的地下根系生物量减小。而重度放牧草地中, 3个土壤深度间地下根系生物量差异不显著。放牧改变了沙质草地植物群落的组成、极大降低了植被盖度和生产力;尤其是重度放牧急剧增加了一年生植物的优势、且对浅层根分布的减少影响最大。