内蒙古中部地区退耕还林还草后植被与土壤性状的变化

北方农牧交错带中部的内蒙古乌盟一带退耕还林还草有10余年的历史.通过野外调查和实验室分析,探讨了不同退耕还林还草模式和年限下植物群落和土壤性质的变化,结果表明:(1)人为控制了苜蓿、沙打旺的种植周期的退耕还草工程使得退耕还草后植物群落完全不同于自然群落的演替过程,退耕年限达到6年后严重退化指示植物才大量消失;(2)退耕还林与退耕还草均起到了阻沙作用.但退耕还草在降低土壤砂含量方面效果相对明显;(3)退耕还林还草所带来的植物物种多样性变化与土壤性状变化存在正相关关系,说明土壤性状的改良与物种多样性的增加可能     

金尾矿废弃地不同植被恢复模式群落特征

为探讨矿山废弃地不同植被恢复模式的植被特征和物种多样性,以福建紫金山金矿废弃地为研究对象,对6种不同植被恢复模式群落的结构特征和数量组成进行样方调查,统计分析了不同植被恢复模式群落的物种组成、重要值和物种多样性,并与未被破坏的自然植物群落进行了比较分析。结果表明:人工植被恢复群落的丰富度指数、多样性指数和优势度指数呈现出相同的变化趋势。植被恢复9a后,人工植被恢复群落物种组成仍以草本植物为主,五节芒、藿香蓟、艾草、三叶鬼针草和柳叶箬对废弃地有较强的适应能力,可作为乔、灌、草相结合治理模式的配置草种。不同植被恢复模式的群落特征和物种多样性存在差异,马尾松—枫香—本地河滩草模式物种多样性较高,植被恢复效果较好,其次为马尾松—邓恩桉—本地河滩草模式,马尾松—樟树—胡枝子—本地河滩草模式的植被恢复效果不明显。     

黄土丘陵沟壑区退耕地植被自然恢复过程——以吴起县双树沟流域为例

采用TWINSPAN分类法对黄土丘陵沟壑区吴起县双树沟流域30个自然恢复草地植被进行分类,并对分类后各植被群落特征和地上生物量进行统计分析。结果表明：在自然恢复条件下,随着退耕年限的不断增加,退耕地植被自然恢复依次经历了猪毛蒿群落-赖草＋长芒草群落-赖草＋铁杆蒿群落-铁杆蒿群落-铁杆蒿＋茭蒿群落5个发展阶段,地带性植被类型铁杆蒿＋茭蒿群落在研究区内开始出现,并且已经占有一定优势;随着退耕地植被自然恢复的不断进行,Margalef等丰富度指数以及Shannon-wiener等多样性指数、Pielou等物种均匀度指数和地上生物量都呈现出先减小后增大的发展趋势;在植被自然恢复的稳定阶段,虽然物种丰富度指数和物种多样性指数有一定的增加,但是相对恢复初期来讲还是有所下降,并且有达到与初期相当水平的趋势;物种丰富度指数均在第1恢复阶段最大,而均匀度指数Jsw以及Shannon-wiener指数在第5恢复阶段最高。随着退耕地植被自然恢复的不断进行,植被群落总盖度随着退耕年限的延长而不断增大。     

巴山山地退耕地植被自然恢复过程及物种多样性变化

 巴山山地是我国南北方过渡地区,亦是长江重要的水源涵养区,探讨该地区退耕地植被自然恢复演替过程及其物种多样性的变化规律,对于指导该地区的人工植被建设具有重要的理论价值与实际意义。采用时空互代法对巴山山地退耕地植被自然恢复过程及其物种多样性变化进行研究,结果表明:1)巴山山地退耕地植被演替依次经过1年生植被草本群落、多年生草本群落、杂灌草群落及以栓皮栎、橿子栎或栓皮栎为建群种的阔叶林群落等不同阶段,形成地带性植物群落大致需要40～50a;2)物种多样性会随立地环境的变化有所差异,阴坡的各物种多样性指标明显高于阳坡,但其变化规律基本一致。演替初期,植被群落的物种数、Shannon-wiener指数、Simpson指数和Pielou指数相对较低,随着植被群落演替的进行,各指标均呈波浪上升趋势;当植被恢复25a时,各多样性指数均达到最大,分别为23、2.5、0.89和0.8;到地带性植物群落阶段时,其各物种多样性指标又略有降低并趋于稳定。该结论对于充分利用植被自然恢复进行生态改善,并根据植被演替进程采取相应的人工管理措施具有重要的指导意义。     

黄土丘陵沟壑区退耕还林工程对植被恢复影响的研究--以陕西吴旗县为例

在对吴旗县乔木林、灌木林和草原群落野外调查的基础上，对其植被恢复及植被恢复与水土流失的关系进行了定量分析，结果表明，在吴旗县这样的自然地理条件下，通过退耕还林、封山禁牧，植被完全可以得到恢复，完全可以控制水土流失的发生。在自然恢复初期，植物群落将以草原地带性植被为主，并可以恢复到稳定阶段。三种植被群落在植物多样性方面差异并不大，草原群落的物种多样性和群落均匀度要略小于乔木林和灌木林群落。     

桂西北喀斯特人为干扰区植被自然恢复与土壤养分变化

为促进桂西北喀斯特退化生态系统的恢复与重建,采用全面调查和样方调查方法,以自然保护区的顶级群落为对照,研究了桂西北喀斯特人为干扰区自然恢复22a后植被的演替规律与土壤养分变化。结果表明,干扰区物种丧失严重,种类仅有自然保护区的26.6%,随着群落由草丛→草灌丛→灌丛→藤刺灌丛→乔灌丛→顶级群落的顺向演替和发展,群落的高度、生物量和物种多样性、土壤有机质、养分、阳离子交换量和硅、铁、铝、钛等矿质全量逐步增加,钙、镁全量显著减少,pH值降低,土壤质量随着植被的恢复呈波折性提高。     

退化喀斯特植被恢复对土壤微生物数量及群落功能多样性的影响

采集不同恢复阶段的土壤样品,采用微生物培养法研究了退化喀斯特植被恢复对土壤微生物数量、群落功能多样性的影响。研究结果表明随着退化喀斯特植被的恢复,土壤微生物数量增加,表现为乔木群落阶段灌木群落阶段草本群落阶段裸地阶段。土壤微生物群落代谢功能分析表明:植被恢复往往导致较高的平均颜色变化率、物种丰富度和功能多样性。乔木群落阶段的平均诱导底物利用率最高,明显地与其他3个恢复阶段不同。总之,植被恢复使得土壤微生物数量增加,碳源平均利用率增强。因此,创造了更好的土壤条件更有利于退化喀斯特植被的恢复。     

杭锦旗穿沙公路周边植被群落特征与多样性研究

采取路线考察和典型样地调查方法对内蒙古自治区杭锦旗穿沙公路段周边区域的植被群落进行了研究,分析了不同植被群落特征和物种多样性.结果表明,该区域共有16种植被群落,植物37种,分别隶属于14科30属.主要由沙地植物、盐碱化植物和低湿地植物组成.草灌类群落占优势地位,黑沙蒿等群落有较高优势度,但是在演替中处于退化趋势.沙柳、沙棘、柽柳等灌木群落虽然频度较低,但是优势度较高,说明在演替中处于进化趋势.     

坡面植被恢复试验示范区植被群落特征初步研究

以延庆上辛庄开发建设项目坡面试验小区为研究对象,采用样方调查法,对36个小区的植被群落特征进行了调查,探讨了各个小区植被群落的物种组成变化,并运用物种丰富度指数、多样性指数和均匀度指数对各个小区的物种多样性进行了比较分析.研究发现:①对于土质边坡,植草+截水沟、等高绿篱埂等8种护坡方式比较适宜,植物成活成长良好;对于石质边坡,砖砌挡墙+生态袋等4种护坡方式适应性较好;②选用单一植物进行护坡,小区物种多样性变化出现两种趋势,一种是原有物种仍居优势地位,一种是原有物种逐渐退化,被侵人物种取代;③在对照小区中,自然恢复形成的植物群落多样性较好,向着丰富、均匀、稳定的群落发展.     

青藏高原高寒嵩草草甸植被群落特征对退化演替的响应

以空间代替时间的方法,于2012年7月中旬-8月中旬在青藏高原祁连山南麓分别选取原生、轻度、中度和重度4种不同退化梯度的高寒嵩草（Kobresia）草甸,对其土壤理化、水分特征和植被群落进行研究,以探究高寒嵩草草甸生态功能退化过程中植被群落的变化特征.结果表明,中度退化样地的地上生物量、表层（0-10cm）土壤含水量和降水地表入渗速率显著最小（P＜0.01）,表层地下生物量、表层土壤有机质、表层田间持水量和草毡层厚度显著最大（P＜0.01）.基于退化高寒嵩草草甸群落的植被功能群和群落多样性的非度量多维排序结果表明,其退化过程可明确划分为原生植被、轻度退化、中度退化和重度退化4个阶段,冠层高度、地上生物量、草毡层厚度和降水地表入渗速率对群落变化的相对贡献较大.植被群落对退化过程的响应为非平衡型（Non-equilibrium）,群落变化的“分水岭”存在于中度退化和重度退化之间.研究结果对退化嵩草草甸的恢复措施选择具有重要的指导意义.     

Soil phosphorus and tree cover modify the effects of livestock grazing on plant species richness in Australian grassy woodland

The effects of grazing on the richness of understorey plant communities are predicted to vary along gradients of resources and tree cover. In temperate Australia livestock management has involved phosphorus addition and tree removal but little research has examined how the effects of grazing on plant species richness may vary with these management regimes. Patterns of understorey plant species richness were examined in 519, 0.09 ha quadrats in grazed pastures and remnant grassy forests and woodlands in southern Australia. Sheep grazing was the primary land use and sites varied widely in grazing frequency and density, tree cover and phosphorus fertiliser history. Using an information theoretic approach the available data provides strong evidence that the effect of grazing on total species richness varies according to available phosphorus and tree cover. Intermittent grazing and no grazing were associated with high total and native plant richness, but only at low phosphorus concentrations. Phosphorus was strongly negatively correlated with richness, particularly at low grazing frequency. Total species richness was positively correlated with tree cover except under frequent grazing at high stocking rates, suggesting that heavy grazing eliminates spatial and temporal heterogeneity imposed by trees. Native plant species richness was negatively correlated with a history of cultivation, positively correlated with tree cover and varied according to landscape position and geological substrate. Frequent high density grazing, particularly when associated with clearing, cultivation and fertiliser addition, was associated with the persistence of very few native plant species. In contrast, the richness of exotic plant species was relatively invariant and performance of the best model was low. While several studies have highlighted the importance of the grazed and cleared matrix for the conservation of native plant species, this benefit may be limited in landscapes where intensive grazing management systems dominate. Strong evidence for interactions between grazing, phosphorus and tree cover suggest that failure to consider other land use practices associated with grazing management systems could lead to erroneous conclusions regarding vegetation responses to livestock grazing.     

Consequence of grazing pattern and vegetation structure on the spatial variations of net N mineralisation in a wet grassland

The aim of this study was to determine whether the spatial heterogeneity of grassland vegetation structure would lead to spatial heterogeneity in the net nitrogen mineralisation process in the soil and therefore in the quantity of mineral nitrogen available for the plants. The net nitrogen mineralisation in the soil was compared between different vegetation patches generated by grazing, on two different types of plant communities: mesophilous and meso-hygrophilous.In ungrazed conditions, the net soil nitrogen mineralisation rates did not vary significantly between the two plant communities and remained relatively constant with time. Grazing by cattle or horses appeared to have two effects on the process of net soil nitrogen mineralisation. Firstly, it significantly stimulated net nitrogen mineralisation compared to ungrazed conditions and secondly, it led to spatial heterogeneity in mineralisation rates in the grazed enclosures. This spatial heterogeneity of nitrogen available for plants occurred both between and within plant communities.In the meso-hygrophilous plant community, net nitrogen mineralisation increased with grazing pressure. We suggest that a decrease of C inputs to the soil, concomitant with increasing grazing pressure, could decrease microbial nitrogen immobilisation.By contrast, in the mesophilous plant community net nitrogen mineralisation did not vary with grazing pressure. These differences in the functional responsiveness to grazing and biomass between the two plant communities could be related to the differences in the functional traits characterizing their dominant species along the grazing gradient. In the meso-hygrophilous community, the species composition switch with grazing intensity gradient led to the replacement of the perennial plant species by annual plant species which could lead to an improvement in the litter nitrogen content and an acceleration in the litter decomposition rate. By contrast, in the mesophilous plant community, the perennial species remained dominant along the grazing intensity gradient and could explain the absence of effect on the net nitrogen mineralisation rates.We suggest that at the scale of the vegetation patch, the decrease in plant biomass linked to grazing could regulate soil microorganism activity, in relation with shift in plant functional traits which improve litter decomposability.     

Grazing as a management tool in dune grasslands: Evidence of soil and scale dependence of the effect of large herbivores on plant diversity

In nature management, the introduction of large herbivores into human-influenced grasslands is thought to be effective to maintain or enhance plant diversity. In order to test the validity of this assumption, we studied the effect of grazing by large herbivores on plant species richness and community heterogeneity across a soil acidity gradient at different spatial scales in dry coastal dune grasslands in western Belgium and north-western France. The effect of grazing on plant richness varied with scale and soil acidity. Grazing had a predominantly positive effect on plant species richness in all habitats at the small scale (0.25 × 0.25 m). However, at site scale (8 × 8 m) it had only positive effects in grasslands with higher soil pH (6-7.4). Similarly, grazing resulted in a homogenization of grassland vegetation at lower pH, while heterogeneity increased with grazing on soil with higher pH. In general, grazing increased the number of rare species, independent of soil pH. The results confirm that the impact of grazing on plant diversity depends on the scale considered and that the effects further depend on soil acidity which was correlated to biomass production at the given soil pH range in this study. Although grazing seems an appropriate management tool to maintain and even enhance plant biodiversity under many circumstances, it may negatively affect plant species richness, where soil resources limit plant biomass production.     

Remnant grassland habitats as source communities for plant diversification in agricultural landscapes

Lately there has been a shift in Sweden from grazing species-rich semi-natural grasslands towards grazing ex-arable fields in the modern agricultural landscape. These fields normally contain a fraction of the plant species richness compared to semi-natural grasslands. However, small remnant habitats have been suggested as important for plant species diversity and conservation as they may function as refugia for grassland specialists in fragmented and highly modified agricultural landscapes. In this study, we examined whether plant communities on small remnant habitats, i.e. midfield islets, can function as sources for grassland species to disperse out into surrounding grazed ex-fields (former arable fields). We examined species richness and grassland specialists (species favoured by grazing) and their ability to colonize fields after 5 and 11 years of grazing. The fields that had been grazed for a shorter time were fairly species-poor with few grassland specialists. A longer period of grazing had a positive effect on total and small-scale species diversity in both islets and fields. Species composition became more similar with time, and the number of grassland specialists in both habitats increased. We found that grassland specialists dispersed step-wise into the fields, and the number of grassland specialists decreased with distance from the source. Our study suggests that remnant habitats, such as midfield islets, do function as a source community for grassland specialists and enhance diversification of grassland species when grazing is introduced. For long-term conservation of plant species, incorporating small refugia into larger grazing complexes may thus enhance species richness.     

Effects of grazing by horses and/or cattle on the diversity of coastal grasslands in western France

In the coastal grasslands of western France, extensive mixed grazing by cattle and horses has been practised for many centuries. The vegetation of these old embanked grasslands varies along a topographical gradient with a hygrophilous plant community in low-lying depressions seasonally flooded, a mesophilous community on high level flats that are never flooded, and a meso-hygrophilous community on slopes where the soil remains saline. Recently, fewer horses have been grazed on these pastures and so a 6-year study was designed to investigate the effects of monospecific and mixed grazing by horses and cattle on plant community structure, composition and diversity. Mixed grazing produced the most species-rich and structurally diverse swards. Mixed grazing enhanced the development of rosette, sub-halophyte and halophyte species where the soil is saline, due to additive effects between the two herbivore species. Mixed grazing also limited the strongly competitive Elymus repens and Agrostis stolonifera on horse latrine areas, cattle grazing, thus showing a compensatory effect. The combination of additive and compensatory effects with mixed grazing could be used to manage plant diversity, heterogeneity in vegetation structure and communities of conservation value at the scale of the grassland ecosystem.     

Impact of Fencing and Irrigation on Species Composition and Diversity of Desert Plant Communities in the United Arab Emirates

Grazing and water are among the most important factors influencing community structure and productivity in natural rangelands. Little is known about the independent effects of grazing and water and their interaction on plant community structure and productivity in rangelands of the arid Arab Gulf deserts. Paired sampling plots were used to compare plant species composition, diversity and plant abundances and sizes inside and outside 14‐month irrigated and 30‐month non‐irrigated exclosures constructed during dry years on sandy dunes of the arid Dubai Desert Conservation Reserve. The results showed that the negative impacts of high grazing pressures on plant productivity (plant sizes and abundances) and diversity were stronger in the non‐irrigated sites. Both irrigation (IR) and protection (PR) enhanced plant diversity and productivity of the overgrazed degraded Dubai Desert Conservation Reserve. The combined effects of PR and IR resulted in the occurrence of a total of 22 species inside the irrigated exclosures; however, none of them appeared in the irrigated grazed sites. Eighteen palatable species occurred inside, but not outside, the irrigated exclosures. Chamaephytes, which are more sensitive to human and animal disturbances, recovered more than other life forms under PR and IR. Dipterygium glaucum showed a great potential to be used for restoration projects under water IR in the Arab Gulf deserts. It is concluded that grazing and water independently affected plant diversity and productivity, but the relative role of grazing is more important than that of water in conserving desert plants, especially the palatable ones. Copyright © 2016 John Wiley & Sons, Ltd.     

不同干扰方式对桂西北灌草植被物种多样性和生产力的影响

灌草植被在生态系统功能的维持中发挥着重要作用,不同的干扰方式可能改变退化土地灌草植被的多样性及其分布格局,甚至多样性与生产力的关系。以未受干扰的植被作为对照,研究放牧和火烧两种主要干扰对桂西北灌草植被的物种多样性和生产力的影响,并分析了两者之间的关系。结果表明:放牧和火烧处理均降低了灌木的物种丰富度和Shannon-Wiener多样性指数,但放牧处理的均匀度指数与对照相比无显著差异,火烧处理反而显著增加了其均匀度指数。对草本而言,放牧不影响物种丰富度指数,但显著降低了Shannon-Wiener多样性指数和均匀度指数;火烧显著降低了物种丰富度指数,但不影响Shannon-Wiener多样性指数和均匀度指数。与对照相比,放牧和火烧均降低了灌木的地上和地下部分生物量,但两者对草本的地上和地下生物量却产生了正面影响或无影响。此外,这两种干扰方式对灌木和草本多样性与生产力间关系的影响具有不一致性。     

Influence of combined grazing by wild boar and small ruminant on soil and plant nutrient contents in a coppice oak forest

Limited information is available about the impact of grazing on soil and plant nutrient contents in Mediterranean deciduous oak forests grazed by both livestock and wild life. Thus, the main objective of this study was to investigate the effect of wild boar and small ruminants grazing in a coppice oak forest in N Greece. Eight even‐aged stands of similar canopy cover and site quality were selected: four stands with long‐time grazing mainly by wild boar and four stands with long‐time grazing by sheep and goats. A plot of 150 m² in each of the stands was fenced in order to be protected from grazing. A similarly sized plot open to grazing was assigned next to the fenced plot. Species composition was recorded in fenced and grazed plots. Soil samples and individual plants of the dominant palatable grass species Dactylis glomerata and Brachypodium sylvaticum were collected in every fenced and grazed plot. These samples were analysed for contents of nutrients. The results indicated that grazing increased organic matter, C, and total N, P and Ca, while it had no effect on the plant nutrients Mg, Na, K and all micronutrients, and pH as well. Wild boar grazing had a significantly negative impact on the concentrations of Na, Fe, Zn, and Mn in the soil. Beside a decrease in K and Mn, grazing had minimal effects on the contents of plant nutrients. Conversely, wild boar grazing increased the contents of several nutrients such as N, Na, Cu and Fe in plant tissue. It seems that species composition was more affected by the topography and management than by the soil features as revealed by RDA analysis. The results of this study indicate that it is important to maintain moderate small ruminant grazing intensity for the sustainable multi‐disciplinary management of coppice oak forests. It is also important to control wild boar population in order to facilitate ecosystem process, soil preservation and forage quality.     

Grazing intensity and environmental factors effects on species composition and diversity in rangelands of Iran

The aim of this study was to analyze the effects of grazing, precipitation and temperature factors on plant species dynamics (diversity and composition) in the semi-steppe of Isfahan semi-arid rangelands, Iran. The effects of Sheep grazing were studied in a controlled experiment along grazing gradient with seven intensities (from very heavily grazed to nongrazed) during six consecutive years (2006–2011). The results show that plant species dynamics varied among years, but were only slightly affected by grazing intensity. Since the experimental years were much dryer than the long term average, the abiotic constraints may have overridden any grazing effect. The differences among the years were predominantly determined by the abiotic factors of temperature and precipitation. Most of the variations in species dynamics and coexistence between the C₄ and C₃ species were explained by seasonal weather conditions, i.e., temperature and precipitation regimes during the early season (March-June). The dominant C₃ species, Poa bulbosa, was highly competitive in March-June at low and high temperature and rainfall levels, respectively. In contrast, the most common C₄ species Cynodon dactylon benefited from high and low early season temperature and rainfall levels, respectively. However, biomass of P. bulbosa was positively correlated with temperature in March, when effective mean temperature ranges from 0 to 5°C and thus promotes vernalization and vegetative sprouting. Our results suggest that, over a six-year period, it is temporal variability in temperature and precipitation rather than grazing that determines vegetation dynamics and species distributions in grazed semi-steppe ecosystems. Our results also support that the variability in the dominant species biomass, rather than diversity, determine ecosystem functioning. This study provides fundamental knowledge on the complex interaction of climate, vegetation, and grazing.     

划区轮牧制度在草地资源可持续利用中的作用研究

通过对比研究放牧制度及围栏封育对退化草地植被的影响来探讨划区轮牧在退化草地植被恢复中的作用。结果表明，在相同的载畜率条件下，划区轮牧制度通过对放牧利用时间与空间的合理配置，使建群种短花针茅与优势种无芒隐子草在质量百分比、重要值、生产力等方面比连续放牧都有所提高，与围栏禁牧的对照小区有同样的恢复效果。因此，将划区轮牧用于荒漠草原植被恢复在实践中是可行的，是实现草地资源持续利用的有效途径之一，建议在今后的退化草地恢复中要从优化放牧方式上寻找新的发展出路。