Vegetation and soil seed bank in a 23-year grazing exclusion chronosequence in a Mediterranean dry grassland

Long-term grazing shaped plant diversity in dry Mediterranean grasslands. Abandonment of grazing affects plant diversity especially in the northern Mediterranean. Considerable efforts are, therefore, under way for grassland conservation and restoration. Yet, we do not know at which temporal scales impacts of grazing abandonment appear and in particular how soil seed banks evolve after longer grazing abandonment. Here, we provide detailed data from one of the very few long-term experiments available. These experiments provide data for up to 23 years (1982–2005) of grazing exclusion built in 1982, 1989, 2000 and 2001. Grazing exclusion decreased species richness, modified vegetation structure and changed soil parameters. Decline in species richness appears in communities that experienced 16 and 23 years of grazing exclusion. Only four to nine plant species of this Mediterranean grassland built persistent soil seed banks appearing after grazing exclusion, compared to 40–50 species in the established vegetation of grazed plots. Hence, similarity between vegetation and soil seed bank decreased with time of grazing exclusion. Even 23 years after abandonment, no woody plants colonised the experiments. We conclude that vegetation will recover fast from grazing abandonment in the short-term. Nevertheless, longer abandonment will impact diversity due to reduced soil seed banks.     

Productivity: key factor affecting grazing exclusion effects on vegetation and soil

In this study, we inquire into the effects of short-term goat grazing abandonment on plant species and functional composition, bare ground and net primary productivity (NPP) in two traditionally grazed pastures located in the Canarian Network of Natural Protected Areas and the Natura 2000 Network. In addition, we analyse soil chemical properties, biomass tannin content and energetic value to find out how grazing abandonment affects soil fertility and forage quality of these agroecosystems. Grazing exclusion effects on plant species and functional composition, as well as on soil fertility depended on the productivity of the studied pasture. Erect forbs and shrubs (endemic to Macaronesian region and native) were favoured by grazing removal in the most productive pasture, while soil fertility decreased in the driest and least productive site. An increase in NPP after exclusion was consistent among study sites. Although we consider goat grazing as necessary for maintaining traditional agroecosystems, we also suggest controlling it over time, allowing some periods of rest to give endemic shrub species time to recover from near propagule sources.     

Effect of fencing and grazing on a Kobresia-dominated meadow in the Qinghai-Tibetan Plateau

Grazing is one of the most important factors influencing community structure and productivity in natural grasslands. Fencing to exclude grazers is one of the main management practices used to protect grasslands. Can fencing improve grassland community status by restraining grazing? We conducted a field community study and indoor soil analyses to determine the long-term effects of fencing and grazing on the above-ground community and soil in a Kobresia-dominated meadow in the Qinghai-Tibetan Plateau, NW China. Our results showed that fencing significantly improved above-ground vegetation productivity but reduced plant density and species diversity. Long-term fencing favored the improvement of forage grass functional groups and restrained the development noxious weed functional groups. There were significant positive effects of fencing on below-ground organic matter, total nitrogen, available nitrogen, total phosphorus and available phosphorus. The productivity of grazed meadow showed a weak decrease over time. There were long-term decreasing trends for plant density both in fenced and grazed meadows. Our study suggests that grazing can be considered as a useful management practice to improve species diversity and plant density in long-term fenced grasslands and that periodic grazing and fencing is beneficial in grassland management.     

高寒草地植物群落关键种对不同放牧家畜组合放牧的响应

如何通过合理的利用方式提高高寒草地管理水平,实现其可持续利用一直是草地生态学领域的研究热点。为明确不同放牧家畜组合下高寒草地植物群落关键种的演替规律及其驱动因素,基于中等放牧强度设置了不同放牧家畜组合放牧样地（牦牛单牧、藏羊单牧、牦牛藏羊1 ： 2混牧、牦牛藏羊1 ： 4混牧、牦牛藏羊1 ： 6混牧）以及围封样地,并在连续放牧处理7年后系统分析了不同放牧家畜组合下植物群落特征与土壤理化性质变化,以期确定最优放牧组合。结果表明：（1）不同放牧家畜组合均会显著降低高寒草地植物盖度,但对其物种丰富度与多样性指数的影响并不显著。（2）牦牛藏羊1 ： 2混牧下植物群落特征与禁牧处理下植物群落特征较为相似,且牦牛藏羊1 ： 2混牧下的植物群落稳定性最强、组织水平最高。（3）牦牛单牧与1 ： 2混牧下关键种为矮生嵩草;藏羊单牧下关键种为天山针茅;1 ： 4混牧下关键种为星毛委陵菜;1 ： 6混牧与围封下关键种为赖草。（4）围封能够显著降低土壤容重,藏羊单牧则会显著增加土壤容重与土壤速效氮、磷含量。（5）土壤速效氮、容重与含水量是驱动不同放牧家畜组合下植物群落关键种演替的重要理化因子。综上所述,中等放牧强度下,牦牛藏羊1 ： 2混牧是青藏高原高寒草地较为理想的利用方式。此外,相较于单纯增加草地物种丰富度或多样性,建立植物群落物种之间的有效关联是提高青藏高原高寒草地管理水平的另一关键途径。     

Plant traits link hypothesis about resource-use and response to herbivory

Grazing by large herbivores, in interplay with environmental productivity, is a key driver of the composition of the vegetation with important consequences on the ecosystem and, consequently, for land management. We tested the predictions of the resource availability – resource–acquisition theory by assessing the extent to which community averages of plant traits, known to be related to plant growth, competitive ability and response to grazing were correlated with resource gradients within local (200 km²) geographical ranges. Second, we assessed the applicability of the same set of plant traits to make inferences on ecological effects of grazing by sheep in alpine ecosystems in Norway, using a data set consisting of 16 sites in central Norway. We estimated grazing intensity by free-ranging sheep based on GPS telemetry, soil properties, plant species composition and species traits i.e. specific leaf area (SLA), leaf dry matter content (LDMC), leaf size and plant height. Soil fertility and the interaction between soil fertility and grazing, but not grazing intensity alone, were significantly related to plant species and traits composition. Generally, average SLA showed lower correspondence with soil fertility and grazing than the other traits. Leaf size and plant height were lowest at sites with high grazing intensity and in sites with low fertility, and increased with soil fertility in little and moderately grazed sites, but declined at high fertility sites when grazing was intense. LDMC showed the opposite trend. Grazing intensity was more related to the variability in plant composition and average plant traits when environmental productivity was high. Our results therefore are indicative of a convergence of responses to grazing and nutrient limitation.     

内蒙古贝加尔针茅草原不同利用方式土壤微生物功能多样性

基于Biolog-ECO技术,研究了贝加尔针茅草原在自由放牧、刈割和围封3种不同利用方式下土壤微生物群落功能多样性变化。结果表明:不同的利用方式能显著改变土壤微生物群落代谢活性,反映微生物活性的平均颜色变化率表现为围封>自由放牧>刈割,围封时土壤微生物群落代谢活性最高;不同的利用方式改变了土壤微生物群落多样性指数,自由放牧土壤微生物群落丰富度指数、均匀度指数和优势度指数均最高,围封次之,刈割最低。主成分分析结果表明:在自由放牧和刈割2种利用方式下土壤微生物群落碳源利用模式及代谢功能相似,而围封土壤微生物群落具有不同的碳源利用模式和代谢功能;糖类、氨基酸类和代谢中间产物及次生代谢物为土壤微生物利用的主要碳源。不同的利用方式改变了贝加尔针茅草原土壤微生物群落功能多样性。     

Factors limiting early establishment of the Mediterranean grassland species Brachypodium retusum at disturbed sites

In Mediterranean dry grasslands, water availability and grazing strongly influence plant establishment. Although higher water availability and lower grazing pressure usually increase seedling recruitment in the beginning, higher competition may reduce seedling survival. In our study, we analysed this trade-off for the dominant species of Western Mediterranean steppes Brachypodium retusum which hardly recolonises restoration sites degraded by soil disturbance such as arable use.A split-plot experiment was set up on an ex-arable site in the “La Crau” steppe in order to test the effects of initial watering and sheep grazing on seedling recruitment, survival and early growth during two years. The watering treatment was applied in the first autumn and spring doubling the usual precipitation during this period and grazing was tested using exclosures. Survival and growth of seedlings established from field-sown seeds were compared to those of transplanted seedlings pre-grown in a growth chamber.Watering did not affect germination whereas the grazing effect was negative. Initial watering had a positive effect on survival only in grazed plots suggesting a compensatory effect under grazing disturbance. Significant main effects of watering on early growth disappeared in the second season. Grazing significantly reduced most measured growth traits whereas the effect on survival was only marginally significant. Planted seedlings (49%) survived better than seedlings emerged from field-sown seeds (36%). In conclusion, initial fencing increases establishment success of B. retusum in ecological restoration. Initial watering may help to mitigate negative grazing effects when fencing is not possible.     

The impact of forest encroachment after agricultural land abandonment on passerine bird communities: The case of Greece

Agricultural land abandonment is one of the main drivers of land use change, leading to various responses of farmland ecological communities. In an effort to better understand the effect of agricultural land abandonment on passerine bird communities, we sampled 20 randomly selected sites [1 km × 1 km] in remote Greek mountains, reflecting an abandonment gradient, in terms of forest encroachment. We sampled 169 plots using the point count method of fixed distance (47 passerine species), and we investigated bird diversity and community structure turnover along the gradient. We found that grazing intensity has a beneficial effect hampering forest encroachment that follows progressively land abandonment. Habitat composition changes gradually with forests developing at the expense of open meadows and heterogeneous grasslands. Forest encroachment has a significant negative effect on bird diversity and species richness, affecting in particular typical farmland and Mediterranean shrubland species. Birds form five distinct ecological clusters after land abandonment: species mostly found in pinewoods and cavity-dwelling species; species that prefer open forests forest edges or ecotones; species that prefer shrubland or open habitats with scattered woody vegetation; Mediterranean farmland birds that prefer semi-open habitats with hedges and/or woodlots; and, generalist forest-dwelling or shrubland species. We extracted a set of 22 species to represent the above ecological communities, as a new monitoring tool for agricultural land use change and conservation. We suggest that the maintenance of rural mosaics should be included in the priorities of agricultural policy for farmland bird diversity conservation.     

围封与放牧管理对高寒草甸植物功能性状和功能多样性的影响

植物功能性状能够响应生存环境的变化并直接决定着生态系统功能。为了揭示围封与放牧管理对物种共存和驱动群落构建的影响机理,该研究以青藏高原东缘高寒草甸为对象,分析了围封与放牧处理对植物功能性状和功能多样性的影响。结果显示:(1)在群落水平,放牧显著降低了比叶面积和植物高度;在物种水平,放牧群落中多数杂类草比叶面积减小,而莎草类和禾草类的比叶面积在处理间无显著差异。(2)叶干物质含量与比叶面积在围封和放牧处理中均呈显著负相关关系,在放牧处理中,叶干物质含量与植物高度呈显著的二次函数关系,即随着叶干物质含量的增大,植物高度先减小后增大;在同等比叶面积的情况下,与围封相比,放牧降低了叶干物质含量;在相同叶干物质含量的情况下,与围封相比,放牧降低了植物高度。(3)放牧在总体上降低了种间性状的平均差异,植物性状表现出趋同响应,具体表现为放牧减小了叶干物质含量和植物高度的种间差异;与围封相比,放牧显著提高了功能均匀度,减小了功能分离度。研究表明,不同植物种对放牧的响应模式存在差异,放牧降低了种间对光资源的竞争,可能增加了对土壤养分的竞争,放牧驱动群落构建的过程中,土壤养分是非常重要的作用因子,说明放牧影响物种共存依赖于对多种资源的竞争。     

Composition and diversity of herbaceous patches in woody vegetation: The effects of grazing,soil seed bank,patch spatial properties and scale

Herbaceous plants contribute much to plant diversity in Mediterranean-type ecosystems though mostly occupying relatively small patches within the dense woody vegetation. While studying species diversity in the herbaceous patches, we hypothesized that grazing, soil seed bank, and spatial properties of the patch affect plant diversity and composition at different spatial scales. The study site was in an LTER site located in the Mediterranean region in north Israel. We determined herbaceous species composition in: (1) randomly sampled quadrats in herbaceous patches in grazed and un-grazed plots; (2) soil seed bank samples taken from the same patches and germinated under optimal greenhouse conditions; (3) quadrats in the same patches sown with a homogenous mixture of local soil samples. Using GIS methods, we determined small-scale spatial characteristics of the herbaceous patches. Alpha and beta diversities were calculated at the patch and plot scales using Shannon's entropy H. Grazing increased alpha diversity of local untreated seed bank samples but decreased alpha diversity of the artificial homogenous soil seed bank mixture at both patch and plot scales. Positive relation between alpha diversity and patch area was detected only under grazing. Grazing increased beta diversity in all three treatments at the patch scale. Grazing decreased the similarity in species composition between above-ground vegetation and soil seed bank. The results indicate that moderate cattle-grazing affects species diversity in the herbaceous patches within the dense maquis. This effect is scale-dependent, and interacts with the effects of soil seed bank and patch spatial-properties: without grazing soil seed bank plays a more important role than patch spatial properties, but under grazing the size and the accessibility of the patch are more important in the determination of herbaceous species composition.     

Variation in structure and diversity in Mediterranean grasslands related to trophic status and grazing intensity

Abstract. The spatial organization of Mediterranean grassland in Spain is described, based on samples from 71 sites covering the existing variation in slope exposition and inclination.The whole set can be regarded as representing a trophic gradient, along which gradual variation in soil, species composition, biomass, and coverage were quantified. Corresponding to other studies from varying habitats, maximal species richness, diversity, and heterogeneity were observed on moderately infertile sites. Maximum species richness, over 60 species, occurred on sites with biomass values from 150–350 g / m². Species richness values are much higher and biomass values are much lower than those found in temperate grasslands. The decrease in diversity towards the mosteutrophic communities is stronger than expected, but can be easily explained by the high grazing pressure here. The variation in diversity observed runs parallel with that in heterogeneity. Zones with a high species richness also have a high heterogeneity, meaning a low amount of dominance. Grazing is understood as abiotic form of disturbance. Differences in grazing pressure may modify the relation between richness and fertility. While the greatest grazing pressure coincides with the most eutrophic communities, decreasing progressively towards the oligotrophic ones, the trend predicted by the resource availability theory is maintained; species diversity will be maximal at intermediate levels of disturbance. Absence of grazing in the eutrophic communities would lead to an investment in the soil of the unconsumed organic matter.     

How do sheep affect plant communities and arthropod populations in temperate grasslands?

Grasslands being used in sheep farming systems are managed under a variety of agricultural production, recreational and conservational objectives. Although sheep grazing is rarely considered the best method for delivering conservation objectives in seminatural temperate grasslands, the literature does not provide unequivocal evidence on the impact of sheep grazing on pasture biodiversity. Our aim was therefore to review evidence of the impacts of stocking rate, grazing period and soil fertility on plant communities and arthropod populations in both mesotrophic grasslands typical of agriculturally improved areas and in native plant communities. We therefore conducted a literature search of articles published up to the end of the year 2010 using ‘sheep’ and ‘grazing’ as keywords, together with variables describing grassland management, plant community structure or arthropod taxa. The filtering process led to the selection of 48 articles, with 42 included in the stocking rate dataset, 9 in the grazing period dataset and 10 in the soil fertility dataset. The meta-analysis did not reveal any significant trends for plant species richness or plant community evenness along a wide stocking rate gradient. However, we found frequent shifts in functional groups or plant species abundance that could be explained by the functional properties of the plants in the community. The meta-analysis confirmed that increasing soil fertility decreased plant species richness. Despite the very limited dataset, plant species richness was significantly greater in autumn-grazed pastures than in ungrazed areas, which suggests that choosing an appropriate grazing period would be a promising option for preserving biodiversity in sheep farming systems. Qualitative review indicated that low grazing intensity had positive effects on Orthoptera, Hemiptera (especially phytophagous Auchenorrhyncha) and, despite a diverse range of feeding strategies, for the species richness of Coleoptera. Lepidoptera, which were favoured by more abundant flowering plants, also benefited from low grazing intensities. Spider abundance and species richness were higher in ungrazed than in grazed pastures. In contrast, there are insufficient published studies to draw any firm conclusions on the benefits of late grazing or stopping fertilization on insect diversity, and no grounds for including any of this information in decision support tools at this stage.     

The Influence of Tropical Plant Diversity and Composition on Soil Microbial Communities

There is growing interest in understanding the linkages between above- and belowground communities, and very little is known about these linkages in tropical systems. Using an experimental site at La Selva Biological Station, Costa Rica, we examined whether plant diversity, plant community composition, and season influenced microbial communities. We also determined whether soil characteristics were related to differences in microbial communities. Phospholipid fatty acid (PLFA) composition revealed that microbial community composition differed across a plant diversity gradient (plots contained 1, 3, 5, or over 25 species). Plant species identity also was a factor influencing microbial community composition; PLFA composition significantly varied among monocultures, and among three-species combinations that differed in plant species composition. Differences among treatments within each of these comparisons were apparent in all four sampling dates of the study. There was no consistent shift in microbial community composition between wet and dry seasons, although we did see significant changes over time. Of all measured soil characteristics, soil C/N was most often associated with changes in microbial community composition across treatment groups. Our findings provide evidence for human alteration of soil microbial communities via the alteration of plant community composition and diversity and that such changes are mediated in part by changes in soil carbon quality.     

Interacting effects of fertilization,mowing and grazing on plant species diversity of 1500 grasslands in Germany differ between regions

The relationship of different types of grassland use with plant species richness and composition (functional groups of herbs, legumes, and grasses) has so far been studied at small regional scales or comprising only few components of land use. We comprehensively studied the relationship between abandonment, fertilization, mowing intensity, and grazing by different livestock types on plant diversity and composition of 1514 grassland sites in three regions in North-East, Central and South-West Germany. We further considered environmental site conditions including soil type and topographical situation. Fertilized grasslands showed clearly reduced plant species diversity (?15% plant species richness, ?0.1 Shannon diversity on fertilized grasslands plots of 16 m²) and changed composition (?3% proportion of herb species), grazing had the second largest effects and mowing the smallest ones. Among the grazed sites, the ones grazed by sheep had higher than average species richness (+27%), and the cattle grazed ones lower (?42%). Further, these general results were strongly modulated by interactions between the different components of land use and by regional context: land-use effects differed largely in size and sometimes even in direction between regions. This highlights the importance of comparing different regions and to involve a large number of plots when studying relationships between land use and plant diversity. Overall, our results show that great caution is necessary when extrapolating results and management recommendations to other regions.     

Effects of different fencing regimes on community structure of degraded desert grasslands on Mu Us desert,China

Grazing is one of the major anthropogenic driving factors influencing community structure and ecological function of grasslands. Fencing has been proved to be one of the main measures for rehabilitating degraded grasslands in northwestern China. However, data from combined empirical studies on the effects of different management regimes in desert grasslands are lacking. So we selected long‐term fencing (fenced since 1991), mid‐term fencing and seasonal fencing (fenced since 2002), and adjacent free‐grazing grasslands to investigate vegetation and soil properties on southwest Mu Us desert. Our results showed that fencing increased plant cover, height, aboveground biomass (AGB) of different plant life‐form groups, Shannon–Wiener diversity index, Evenness index, Simpson index, total soil nitrogen, total soil phosphorus, and soil organic matter, but decreased plant density, species richness, Richness index, soil bulk density, water content, and pH. However, 22–24 years of long‐term complete fencing might cause redegradation of vegetation and soil nutrients, characterized by the reduction of some vegetation properties, biodiversity, total AGB, and some soil properties. Seasonal fencing with 11–13 year was more beneficial to vegetation restoration than that with completely fencing measures. Our study suggests that appropriate artificial disturbances, such as seasonal fencing (winter grazing and summer fencing), should be used after long‐term fencing in order to maintain grassland productivity and biodiversity. These findings will help to provide theoretical support for vegetation restoration and sustainable management in grassland under grazing prohibition at Mu Us desert.     

Grazing increases functional richness but not functional divergence in Tibetan alpine meadow plant communities

Plant community diversity and ecosystem function are conditioned by competition among co-occurring species for multiple resources. Previous studies suggest that removal of standing biomass by grazing decreases competition for light, but coincident grazing effects on competition for soil nutrients remain largely unknown in Tibetan rangelands where grazing tends to deplete soil phosphorus availability. We measured five functional traits indicative of plant productivity and stoichiometry leaf carbon concentration (LCC), leaf nitrogen concentration (LNC), leaf phosphorus concentration (LPC), specific leaf area (SLA), leaf dry matter content (LDMC) for component species of plant communities in grazed and ungrazed plots in five Tibetan alpine meadows. We examined the diversity of traits singly Rao index of functional diversity (FDrao) and in aggregate functional richness (FRic), functional divergence (FDiv), and functional evenness (FEve) in response to grazing. We tested whether foliar trait diversity increases with nutrient competition but decreases with light competition when competitive exclusion is reduced by grazing. The FDrao of LPC significantly increased under grazing, but FDrao for LCC, LNC and SLA tended to decrease. The FDrao of LDMC increased at the drier site but decreased at the wettest site. There was a strong negative association between increase in FDrao of LPC and decrease in soil nutrients, especially soil phosphorus availability. The FRic for all five traits together increased with species diversity following grazing, but neither FDiv nor FEve differed significantly between grazed and ungrazed plots at most sites. Grazing in Tibetan alpine meadows tends to increase competition for soil phosphorus while decreasing competition for light, resulting in an increase in the functional richness in grazed plant communities without any significant changes in the overall functional diversity of foliar traits. Our study highlights the potential importance of grazing mediated competition for multiple resources in alpine meadow ecosystems.     

The impact of grazing management on Orthoptera abundance varies over the season in Mediterranean steppe-like grassland

As semi-natural grassland has a high level of biological diversity, understanding the effects of grazing and its variation over time is important in order to identify sustainable grazing practices. We measured temporal variation in Orthoptera abundance and spatial vegetation structure during seasonal grazing in an extensive sheep-farming system. We studied five grazed pasture areas (pre-grazing and post-grazing) and two adjacent ungrazed grasslands. We recorded the total abundance of Orthoptera and described the vegetation structure of 175 replicate plots (25 per pasture/grassland) during six field sampling sessions. We demonstrated that the impact of grazing on Orthoptera abundance is species-specific and greatly varies over the grazing season. The decrease of phytovolume is significant after 4–7 weeks of sheep grazing. Total Orthoptera abundance was higher in pre-grazed plots than in ungrazed plots, and higher in ungrazed plots than in post-grazed plots. These differences were particularly high during the peak of adult abundance. No difference in species richness was observed between grazing intensities. Total Orthoptera abundance positively correlated to phytovolume only when grazing pressure was high. However, the relationship between abundance and phytovolume differed between species. Extensive grazing by sheep tends to homogenize spatial vegetation structure and to temporarily reduce total Orthoptera abundance at pasture scale. However, rotational grazing allows spatial and temporal heterogeneity in vegetation structure to be maintained at farm scale, heterogeneity that is beneficial for Orthoptera. In contrast, absence of grazing has a negative impact on Orthoptera abundance as it favours the accumulation of litter, which is detrimental for a high proportion of xerothermophilic Orthoptera associated with bare ground and short vegetation.     

Use of sheep grazing in the restoration of semi‐natural meadows in northern Finland

Abstract. The biodiversity of species‐rich semi‐natural meadows is declining across Europe due to ceased management. In this study we aimed to find out how successfully the local species richness of an overgrown semi‐natural mesic meadow could be restored by sheep grazing after a long period of abandonment. The cover of vascular plant species in grazed plots and ungrazed exclosures was studied for five years and the responses of different functional plant groups were followed (herbs vs grasses, tall vs short species, species differing in flowering time, species representing different Grime's CSR strategies and species indicative of rich vs poor soil). Grazing increased species number by nearly 30%. On grazed plots the litter cover practically disappeared, favouring small herbs such as Rhinanthus minor, Ranunculus acris, Trifolium pratense and the grass Agrostis capillaris. Grazing decreased the cover of the late flowering tall herb Epilobium angustifolium but had no effect on the abundance of the early flowering tall herbs Anthriscus sylvestris or Geranium sylvaticum. We suggest that to succeed in restoration it is useful to determine the responses of different functional plant groups to grazing. Grassland managers need this information to optimize the methods and timing of management used in restoration. Additional management practices, such as mowing, may be needed in mesic meadows to decrease the dominance of tall species. The availability of propagules seemed to restrict further increase of species richness in our study area.     

放牧干扰下的蝗虫－植物相互作用关系

本文研究了内蒙古典型草原植物和蝗虫群落在不同放牧强度影响下的多样性、均匀性和丰盛度变化。比较了蝗虫群落与植物群落在放牧梯度上的相互作用关系。研究发现,放牧干扰活动会明显地影响植物和蝗虫群落结构,但蝗虫群落结构的变化趋势并非与植物完全同步。蝗虫与植物间的联系更多地表现在植物起着蝗虫栖息地条件的作用,而并不完全是食料植物的作用。文中对放牧实践与多样性保护的关系进行了讨论。     

Best management practices to face degraded territories occupied by Cistus ladanifer shrublands – Portugal case study

Land degradation in the Mediterranean Basin is clearly connected to the resilience of perturbed ecosystems, contributing to land abandonment, recurrent fires and biodiversity loss, with the prevalence of secondary shrublands that tend to occupy large areas. This is the case of Cistus ladanifer shrublands, one of the most widespread shrub communities in the Iberian Peninsula and a poor, uniform and resilient system. Here, we analyse the impact of several management practices in the recovery of territories largely occupied by this shrubland. We tested “non-intervention”, “cut”, “fire”, “mechanical mobilisation” and “pasture” in 100-m² plots of Cistus ladaniferus L., in Central Portugal, and followed them from 1993. Flora were analysed using Braun–Blanquet's methodology and the plots were compared with hierarchical cluster analysis and principal component analysis. An analysis of variance was also performed to investigate differences in management practices, both between plots and between two periods of time. The results show that extensive grazing or continuous cut have a high impact on plant diversity and community structure, with extensive grazing being the best way to improve plant diversity in a short period of time, using fewer resources.