Effects of fertilization and afforestation on community structure of traditionally managed hay meadows in western Norway

The aims of this paper were to find the effects of artificial fertilizer, intensive cultivation and abandonment with afforestation on species composition of traditional meadows at a broad scale, and to describe the ecological variation of different meadow communities. The flora of 21 traditionally managed hay meadows was compared with that of 52 artificially fertilized hay meadows, 28 intensively cultivated grasslands and 29 afforested grasslands by means of classification. Predictors for differences in species composition were tested using multiple regression analyses with associated Monte Carlo permutation tests. Habitat diversity and Ellenberg N were the most important predictors for differences in species composition of traditional meadows. High habitat diversity was associated with maximum occurrences of all kinds of meadow species (high-productive, generalist, low-productive, habitat specialist, regionally rare, vulnerable and orchid species). These meadows are therefore of high conservation value. Traditional meadows contained also some nitrophilous species that dominate artificially fertilized meadows, but in small populations. Artificially fertilized meadows supported the generalist and productive subset of the species from traditional meadows. Thus, artificially fertilized meadows are of low conservation value. As regionally rare and vulnerable species were only recorded at sites with no use of artificial fertilizer, its application should be avoided whenever the aim is to recreate or maintain semi-natural grasslands of high conservation value. Regionally rare and vulnerable meadow species were not recorded in afforested sites, suggesting that afforestation of traditional meadows may have similar negative effects for the traditional meadow flora as the use of artificial fertilizer.     

Abandonment of traditionally managed mesic mountain meadows affects plant species composition and diversity

In recent years abandonment of traditional management of mountain grasslands has been observed throughout Central Europe. However, the impact of abandonment on vegetation of mountain grasslands is still unclear. In this study it was hypothesized that the cessation of traditional management of mesic mountain meadows causes changes in their species composition and a decrease in the biodiversity. In total, 260 plots were established in the Sudetes (SW Poland) on meadows with regular annual mowing, meadows with irregular mowing management, and abandoned meadows. Relevés (5 × 5 m) were performed, and the habitat properties were determined using Ellenberg indicator values. The study confirmed the hypothesis that the various ways of extensive management have an influence on species richness. The lowest species richness was observed on the irregularly managed meadows, while higher species numbers were found on the abandoned and regular managed meadows. The majority of patches on abandoned meadows exhibited degradation through the expansion of Solidago gigantea, Solidago canadensis, Lupinus polyphyllus, Heracleum sosnovsky, Calamagrostis epigejos, Deschampsia flexuosa, Festuca rubra and Hypericum maculatum. Meadows subjected to different management practices differed significantly in Ellenberg indicator values. The abandoned meadows had the highest values of the light index (L) and nitrogen availability (N), whereas the highest values of soil moisture (F) were noted on the irregularly managed meadows. The degradation of mountain mesic meadows requires regular mowing management, which stops ecological succession and preserves their high biodiversity.     

Stimulation of seed germination in an abandoned hay meadow

Abstract. In order to stimulate germination from the soil seed bank in a formerly species-rich hay meadow for conservation purposes, eight gaps were made in each of four habitat types: (1) Dry/open, (2) Dry/shaded, (3) Moist/open and (4) Moist/ shaded; the meadow was abandoned 12 yr before the experiment started. The mean tree cover of the gaps was reduced from 50 % to 22 %. Light was estimated as distance to nearest tree towards south and shade as tree cover. Soil moisture content was estimated from topography and measured from soil samples. There were no significant differences in total herb number between strata before the experiment started. The number of the target group herb indicators of old, traditional management, was however higher in dry, open areas than in shaded areas whether moist or dry. After the treatment, 15 herbs appeared anew in the gaps, nine of these were indicators of traditional management. 80 % of the indicators present after treatment were either new or had increased in frequency in the gaps. More indicators of traditional management appeared in gaps in the open, on dry soils in slopes than in shaded gaps, on moist soils and flat surface. In order to stimulate germination from the seed bank of as many herb indicators of traditional management as possible in abandoned hay meadows of the region, dry, sloping areas, situated as far as possible from large trees towards south and in the open, should be chosen for making gaps for germination.     

Phytosociology and ecology of old hay meadows in Hordaland,western Norway in relation to management

Well-drained mown hay meadows in Hordaland, western Norway, were investigated. The hay meadows are either managed in a traditional or in a semi-traditional way. Traditional management in the area involves little or no use of manure or fertilizer, mowing once or twice a year with a first cut later than June 23, clearing in spring and intensive grazing for short periods in spring and autumn. Semi-traditional management involves use of small to medium quantities of commercial fertilizer, often in addition to manure. Grazing may be irregular, light or lacking.Eight units of hay meadow vegetation are described, all assigned to the class Molinio-Arrhenatheretea, order Arrhenatheretalia; four units to the Atlantic alliance Cardaminion pratensis, association Cardamino pratensis-Conopodietum majoris (with three subassociations); one unit to the alliance Arrhenatherion elatioris, three units are provisionally grouped as Galium uliginosum-Knautia arvensis meadows.Continuous management of these meadows has resulted in characteristic species compositions, which vary along a west-east climatic gradient, and are related to the amount of commercial fertilizer used and the natural mineral-content of the soil.These hay meadows seem to be best maintained by continuing the traditional management regime. Grazing in spring and in autumn reduces fast growing dominants and creates openings for new seedlings of annuals and biennials. A late first cut allows for ripening of the seeds and creates openings for light for the species of the lower field layer. A list of species characteristic of traditionally managed permanent hay meadows is presented, and possible effects of present changes in management on the species composition of the meadows are discussed.The amount of organic matter in the topsoil is small in most stands. The pH values are between 4.0 and 5.6. The highest values were recorded in soil where little or no commercial fertilizer is used, and where the subsoil is naturally rich in minerals. A tendency to Mg impoverishment in the best fertilized stands is demonstrated. Species-rich stands on Ca-rich soils are poor in P.The expected changes in vegetation, future use, and conservation of permanent hay meadows in Hordaland are discussed.     

Vegetation - environment relationships of old hay meadows at Sverveli, Telemark, S Norway

The vegetation of traditionally managed species-rich hay meadows at Sverveli, Telemark, S Norway was studied applying an indirect gradient approach. The vegetation in 93 randomly placed sample plots was analysed in order to detect the main vegetational gradients. Ecological measurements were recorded from each plot. The relationships between vegetation and environment were studied by DCA and LNMDS ordinations and non-parametric correlation analysis. Both ordinations revealed the same two ecologically interpretable vegetation gradients. Soil moisture was identified as the most important environmental factor in determining the species composition, followed by soil nutrient content. The contents of P, K. and Mg in the soil were more strongly correlated with the main vegetational gradients than was soil N. Differences in management history may explain some of the observed variation in species composition that was not accounted for by the recorded environmental variables.     

Plant genotype identity and diversity interact with mesograzer species diversity to influence detrital consumption in eelgrass meadows

Seagrass meadows are among the world's most productive ecosystems, and as in many other systems, genetic diversity is correlated with increased production. However, only a small fraction of seagrass production is directly consumed, and instead much of the secondary production is fueled by the detrital food web. Here, we study the roles of plant genetic diversity and grazer species diversity on detrital consumption in California eelgrass Zostera marina meadows. We used three common mesograzers—an amphipod, Ampithoe lacertosa, an isopod, Idotea resecata, and a polychaete, Platynereis bicanaliculata. Each grazer consumed eelgrass detritus at rates greater than live eelgrass or macroalgae. This detrital consumption, however, was not spread evenly over leaves shed from different eelgrass clones. Palatability and consumption varied because of genotype specific differences in leaf texture, secondary metabolites (phenolics), and nutritional quality (nitrogen). Further, detritus derived from some eelgrass genotypes was palatable to all grazers, while detritus from other genotypes was preferentially consumed by only one grazer species. Under monospecific grazer assemblages, plant genetic identity but not diversity influenced detritus consumption. However, more realistic, diverse mesoconsumer communities combined with high plant‐detrital genotypic diversity resulted in greater consumption and grazer survival. These results provide a mechanism for field observations of increased mesograzer density and diversity in genetically diverse seagrass assemblages and offer a potential explanation for variation in results of resource diversity– detrital processing experiments in the literature, which often exclude macroinvertebrate taxa. More broadly, our findings support the emerging principle that biodiversity effects are strongest when diversity in both consumer and resource taxa are present.     

Species introduction through seeds from an old,species‐rich hay meadow: Effects of management

Abstract. A local seed mixture from plants growing in a species‐rich, traditionally managed hay meadow site at Varaldsoy, Hardanger, western Norway, where many endangered hay meadow species of the region are growing, was sown in a newly harrowed experimental field 1 km from the source meadow in order to increase the habitat area for the endangered species. Of 25 endangered species recorded in the source meadow, only one (Holcus lanatus) was present in the target meadow. After sowing, 16 of the endangered species in addition to Holcus lanatus were recorded in the new site. Six species were only present in sown plots and seven others were more frequent there, while three species might have arrived by chance or originated from the seed bank. Replacing the traditional management regime, including one late cut and grazing in spring and in autumn, with three cutting times and the creation of gaps in the sward, resulted in a higher number of endangered species in plots which were only cut, possibly because the grazing was too intensive in the small enclosures.     

Plant species diversity changes in abandoned chestnut (Castanea sativa) groves in southern France

Over the last few decades, marked land use changes have taken place in many Mediterranean ecosystems. For example, many chestnut groves in France are now abandoned and have turned into 'natural' coppice stands while others are now clear-cut every 10 or 15 years for wood. Species composition and life form diversity of the plant communities have changed markedly both in the abandoned groves and in the periodically clear-cut coppice stands. What are the consequences of these changes on biodiversity at local and regional scales, and what are the implications for 'new forestry' management intended to conserve biodiversity at the same time as it optimizes productivity and profitability? To answer these questions we studied plant species diversity in the understorey strata along a successional gradient including cultivated grove; abandoned grove; young (15 years old), medium (40 years), and old (>55 years) coppice stands. The results showed that species richness decreased quickly but not steadily along this gradient, but life-form spectra data highlighted that the high levels of plant species biodiversity in cultivated groves were due primarily to the large number of therophytes (annual plants). At a shorter time scale, we also studied the consequences of experimental clear-cutting on plant species biodiversity. Direct measurements over four years showed that species richness and diversity in the understorey increased in the first two years after clear-cutting, but decreased during the 3rd and 4th years. This decrease corresponded closely with a steady increase in Leaf Area Index of the forest canopy. These results have been used to suggest some possible ways to manage the biodiversity in these ecosystems.     

Plant biomass and species composition along an environmental gradient in montane riparian meadows

In riparian meadows, narrow zonation of the dominant vegetation frequently occurs along the elevational gradient from the stream edge to the floodplain terrace. We measured plant species composition and above- and belowground biomass in three riparian plant communities—a priori defined as wet, moist, and dry meadow—along short streamside topographic gradients in two montane meadows in northeast Oregon. The objectives were to: (1) compare above- and belowground biomass in the three meadow communities; (2) examine relations among plant species richness, biomass distribution, water table depth, and soil redox potential along the streamside elevational gradients. We installed wells and platinum electrodes along transects (perpendicular to the stream; n=5 per site) through the three plant communities, and monitored water table depth and soil redox potential (10 and 25 cm depth) from July 1997 to August 1999. Mean water table depth and soil redox potential differed significantly along the transects, and characterized a strong environmental gradient. Community differences in plant species composition were reflected in biomass distribution. Highest total biomass (live+dead) occurred in the sedge-dominated wet meadows (4,311±289 g/m²), intermediate biomass (2,236±221 g/m²) was seen in the moist meadow communities, dominated by grasses and sedges, and lowest biomass (1,403±113 g/m²) was observed in the more diverse dry meadows, dominated by grasses and forbs. In the wet and moist communities, belowground biomass (live+dead) comprised 68–81% of the totals. Rhizome-to-root ratios and distinctive vertical profiles of belowground biomass reflected characteristics of the dominant graminoid species within each community. Total biomass was positively correlated with mean water table depth, and negatively correlated with mean redox potential (10 cm and 25 cm depths; P <0.01) and species richness (P <0.05), indicating that the distribution of biomass coincided with the streamside edaphic gradient in these riparian meadows.Electronic Supplementary Material Supplementary material is available in the online version of this article at     

Plant diversity promotes soil fungal pathogen richness under fertilization in an alpine meadow

高寒草甸植物多样性促进了施肥条件下土壤真菌病原体的丰富度 在农业生态系统中,氮添加对植物病原真菌丰富度和相对多度的影响已被基本阐明,然而在自然生态系统中,氮添加如何影响土壤中的植物病原真菌(通过影响植物群落结构或土壤理化指标)仍知之甚少。本研究以青藏高原东部高寒草甸为研究对象,基于7年的氮添加梯度野外实验,使用Miseq平台,针对土壤真菌的ITS1基因进行测序,以评估氮添加对高寒草甸土壤中的植物病原菌丰富度和相对多度的影响,并阐明氮添加通过不同途径(即植物群落结构和土壤理化指标)影响病原菌的潜在机制。基于模型筛选和结构方程模型等统计方法,本研究发现,氮添加通过改变土壤理化指标影响土壤中的植物病原菌相对多度。但是,在排除掉氮添加对土壤中植物病原菌丰富度的影响后,地上植物物种丰富度与土壤中植物病原菌丰富度仍存在显著的正相关性。因此,我们认为高寒草甸土壤中植物病原菌丰富度和相对多度受到不同的机制调控。世界范围内,自然生态系统中氮素输入量的加剧(包括氮沉降和氮肥施用)所引起的植物物种丧失引起了人类的较大关注。除此之外,氮素输入所引起的植物病原菌丰富度和相对多度的变化也值得我们警醒,因为植物病原菌群落结构的改变可能会对生态系统功能和服务产生重要影响。     

Plant species diversity in abandoned coppice forests in a temperate deciduous forest area of central Japan

We investigated plant species diversity as it related to stand structure and landscape parameters in abandoned coppice forests in a temperate, deciduous forest area of central Japan, where Fagus crenata was originally dominant. The species occurring in the study plots were classified into habitat types based on a statistical analysis of their occurrence bias in particular habitats (e.g., primary forest, coniferous plantation) in the landscape studied. The relationships between stand structure, which reflected the gradient of management, and forest floor plant species diversity (H and J) and richness (number of species per unit area) were not significant. However, these factors did influence the forest floor plant composition of the different types of habitat. According to the multiple regression analysis, species diversity and the richness of forest floor plants was affected by landscape parameters rather than by stand structure. For trees, species richness was mainly affected by the relative dominance of F. crenata, which is one of the stand structure parameters that decreases with intensive management. This is probably because many of the tree species that are characteristic of coppice forests increase after F. crenata have been eliminated by management; these species are not dominant in the original forest, where they are suppressed by F. crenata, the shade-tolerant dominant species. The species diversity (H and J) of trees was positively correlated with some landscape parameters, including the road density around the study plot, which may be associated with the intensity of management activity. The number of disturbance-tolerant species increased with increasing road density. Stand structure mainly affected disturbance-intolerant forest floor plant species and disturbance-tolerant tree species. Thus, the species diversity responses differed between forest floor plants and trees. The impact of forest management on species diversity was more prominent for forest floor plants.     

Effects of light competition and litter on the performance of Viola palustris and on species composition and diversity of an abandoned fen meadow

Theeffects of light competition and litter on seedling recruitment and theperformance of established individuals were examined in Violapalustris. This polycarpic perennial plant was a common component ofspecies-rich fen meadows in northwestern Germany until the middle of thiscentury, but today is considered to be regionally endangered. From summer 1996until summer 1998 a bi-factorial field experiment combining three standing croptreatments (mowing, thinning, control) with two litter layer treatments (litterremoval, no litter removal) was carried out in an abandoned fen meadow toinvestigate the effects of these factors both on V.palustris and on aboveground species composition and diversity.MANOVAs (multivariate analysis of variance) revealed significant treatmenteffects for the performance of V. palustris related toexperimental manipulation. Mowing increased vital attributes including thenumber of rosette leaves, the percentage of individuals with chasmogamous andcleistogamous flowers and the number of rhizomes. In contrast, the length of theleafstalk, mean leaf area and the length of rhizomes were negatively associatedwith mowing. Litter removal significantly increased the number of V.palustris seedlings. The removal of the litter layer already resultedin an increase in aboveground species richness in the first year of theexperiment. After three years of experimental manipulation, both abovegroundspecies richness and diversity were positively associated with mowing.Redundancy Analysis showed that typical wet meadow species (Cardaminepratensis, Lychnis flos-cuculi, Lotuspedunculatus) and species of mesotrophic fens (Violapalustris, Agrostis canina, Potentillapalustris) were positively influenced by mowing. It can be concludedthat V. palustris recruitment and growth is promoted by aregular disturbance regime on fen meadows. The conservation of many typicalspecies of wet meadows and fens in northwestern Germany depends on moderategrazing or cutting. These management types prevent successional changes whichlead to an increase in standing crop and the development of a litter layer, bothof which can cause local extinction.     

Partitioning of arthropod species diversity in temperate meadows,wildflower areas and pastures

To counteract the rapidly ongoing species decline in modern agroecosystems, most European countries have developed and adopted agri-environment schemes. The efficiency of these schemes, however, ranges from successful to nearly ineffective. To estimate the efficiency of the Swiss agri-environment scheme in particular, we investigated the contribution of extensively managed pastures and meadows and wildflower areas to beetle, heteropteran bug and spider diversity. Extensively managed meadows were shown to contribute most to landscape-scale richness (highest species richness for beetles and bugs), followed by wildflower areas (bugs). Meadows harboured approximately twice as many beetle species unique to this habitat type than wildflower areas and pastures. Bug species unique to a specific habitat type were similar between meadows and wildflower areas, but much lower (approximately 30%) in pastures. To increase beetle species richness, extensively managed meadows should be represented more often in the landscape because meadows harboured the highest number of species and most uniquely found species. To increase species richness of true bugs, both meadows and wildflower areas should be represented more often in the landscape because they harboured more species and more uniquely found species compared to pastures. Across arthropod taxa and habitat types, β diversity was more important for γ diversity than α diversity, indicating that distinctiveness, rather than within-site diversity, was key in determining the contribution of sites to γ (landscape) diversity. This substantiates the argument that increasing the number of sites is efficient to increase landscape species richness. The turnover component of β diversity was far more important than the nestedness component for all arthropod taxa and habitat types and accounted for 79.0% to 95.4% of total β diversity. In conclusion, extensively managed meadows and wildflower areas should be particularly promoted by the Swiss agri-environment scheme, as they contributed more to landscape species richness and species uniqueness than pastures.     

Plant species diversity as a driver of early succession in abandoned fields: a multi-site approach

Succession is one of the most studied processes in ecology and succession theory provides strong predictability. However, few attempts have been made to influence the course of succession thereby testing the hypothesis that passing through one stage is essential before entering the next one. At each stage of succession ecosystem processes may be affected by the diversity of species present, but there is little empirical evidence showing that plant species diversity may affect succession. On ex-arable land, a major constraint of vegetation succession is the dominance of perennial early-successional (arable weed) species. Our aim was to change the initial vegetation succession by the direct sowing of later-successional plant species. The hypothesis was tested that a diverse plant species mixture would be more successful in weed suppression than species-poor mixtures. In order to provide a robust test including a wide range of environmental conditions and plant species, experiments were carried out at five sites across Europe. At each site, an identical experiment was set up, albeit that the plant species composition of the sown mixtures differed from site to site. Results of the 2-year study showed that diverse plant species mixtures were more effective at reducing the number of natural colonisers (mainly weeds from the seed bank) than the average low-diversity treatment. However, the effect of the low-diversity treatment depended on the composition of the species mixture. Thus, the effect of enhanced species diversity strongly depended on the species composition of the low-diversity treatments used for comparison. The effects of high-diversity plant species mixtures on weed suppression differed between sites. Low-productivity sites gave the weakest response to the diversity treatments. These differences among sites did not change the general pattern. The present results have implications for understanding biological invasions. It has been hypothesised that alien species are more likely to invade species-poor communities than communities with high diversity. However, our results show that the identity of the local species matters. This may explain, at least partly, controversial results of studies on the relation between local diversity and the probability of being invaded by aliens. Received: 13 July 1999 / Accepted: 4 February 2000     

Plant diversity patterns in semi-natural grasslands along an elevational gradient in southern Norway

Leaf demography and growth of six common, co-occurring woody plant species that varied in stature (tree vs. shrub) and leaf texture (sclerophyllous, coriaceous, malacophyllous) were examined in a subtropical savanna parkland in southern Texas, USA. We tested the hypotheses that, (a) leaves of plants with evergreen canopies would have longer life spans than those of deciduous species; (b) supplementation of soil moisture would decrease leaf life span in both evergreen and deciduous species; (c) species responses to increased soil moisture availability would be inversely related to leaf longevity; and (d) deciduous growth forms would exhibit a greater growth response to increased soil moisture availability than their evergreen counterparts.A variety of seasonal leaf habits (evergreen, winter-deciduous and summer-deciduous canopies) and leaf life spans (median = 66 to 283 days) were represented by the targeted species, but there was no clear relationship between seasonal leaf habit and leaf longevity. Among species with evergreen canopies, median leaf longevity ranged from short (Zanthoxylum fagara = 116 days; Condalia hookeri = 158 days) to long (Berberis trifoliolata = 283 days) but did not exceed 1 yr. In fact, leaf longevity in evergreen shrubs was often comparable to, or shorter than, that of species with deciduous canopies (Ziziphus obtusifolia = 66 days; Diospyros texana = 119 days; Prosopis glandulosa = 207 days). Augmentation of surface soil moisture had no detectable effect on median leaf life span in any species and there was no clear relationship between leaf longevity and species growth responses to irrigation. Contrary to expectations, species with evergreen canopies responded to irrigation by producing more leaf biomass, longer shoots and more leaf cohorts/year than did deciduous species.Species differences in the annual cycle of leaf initiation, leaf longevity and canopy development, combined with contrasts in root distributions and a highly variable climate, may allow for spatial and temporal partitioning of resources and hence, woody species coexistence and diversity in this system. However, the lack of expected relationships between leaf longevity, leaf habit and plant responses to resource enhancement suggests that structure-function relationships and functional groupings developed in strongly seasonal environments cannot be applied with confidence to these subtropical savannas and thorn woodlands.     

植物物种多样性与岛屿面积的关系

由于水库蓄水导致千岛湖原有生境的破碎化和岛屿化.研究选取了50个岛屿,共设立样方70个.调查这些岛屿上乔木和灌木的种类及数量,选择9种曲线拟合岛屿面积与物种多样性指数之间的数学关系.结果发现:乔木、灌木和木本物种数与岛屿面积关系拟合较好的是对数函数、幂函数和S型曲线,其中对数函数为最优模型;乔木、木本Shannon-Wiener多样性指数与岛屿面积关系拟合较好的是S型曲线和逆函数,灌木Shannon-Wiener多样性指数与岛屿面积关系拟合不显著,乔木和木本Shannon-Wiener多样性指数与较小岛屿(y小于1 hm2)面积拟合呈S形曲线和逆函数,而灌木Shannon-Wiener多样性指数与较大岛屿(y大于1 hm2)面积拟合呈S形曲线和逆函数;均匀度、优势度指数与面积拟合关系不显著. 在岛屿面积较小时,物种多样性指数随着面积的增加而迅速增加,但在面积增加到一定限度时,物种多样性指数增加的速率就逐渐变缓.植物物种数增加速率的转折点约为4 hm2,乔木、木本Shannon-Wiener多样性指数增加速率的转折点约为1 hm2,对面积小于的1 hm2的岛屿进行拟合时发现,乔木、木本Shannon-Wiener多样性指数增加速率的转折点在0.15～0.2 hm2之间.     

高寒草甸种间性状差异和物种均匀度对物种多样性与功能多样性关系的影响

物种多样性(SD)与功能多样性(FD)之间存在多种关系,但由于生态系统功能主要由物种的功能属性决定,因而功能多样性对生态系统功能的影响大于物种多样性的影响。但在种间性状差异和物种均匀度这两个构成功能多样性的基本成分中,何者对功能多样性影响更大,并进而决定SD-FD关系尚不明确。通过在高寒矮嵩草(Kobresia humilis)草甸为期6a的刈割(留茬1 cm、3 cm及不刈割)和施肥(尿素7.5 g m~(-2)a~(-1)+磷酸二胺1.8 g m~(-2)a~(-1)、不施肥)控制实验,研究了种间性状差异(33个物种13个性状)和物种均匀度(所有物种)对物种多样性(所有物种)与功能多样性(33个物种13个性状)之间关系的影响。研究结果显示:(1)物种多样性与功能多样性正相关,它们与多性状种间差异负相关,而与物种均匀度正相关。物种均匀度是导致功能多样性变化的主要因素,也是导致SD-FD正相关的原因,这是因为随着物种多样性增加,物种均匀度的增加程度大于多性状种间差异的减少程度,因而功能多样性增加,SD-FD正相关;(2)功能多样性指数(FD_(Rao)和FDis)随物种多样性指数(H')减速递增,表明群落存在一定的功能冗余,且功能冗余随物种多样性的增大而增大,但尚未达到产生SD-FD无相关性的极限H'值;(3)功能多样性对高寒草甸生态系统地上净初级生产力(ANPP)的影响大于物种多样性的影响,二元线性回归显示在同时考虑二者对ANPP的影响时,可排除物种多样性的作用。但由于物种多样性下降或物种丧失引起的物种功能性状丢失或性状空间维度减小将导致功能多样性降低,表明它们之间存在一定互补性,在研究生物多样性与生态系统功能关系时,同时考虑物种多样性和功能多样性的影响仍十分必要。     

Whinchat Saxicola rubetra reproductive success according to hay cutting schedule and meadow passerine density in alluvial and upland meadows in France

In France, whinchat Saxicola rubetra populations now rarely breed at altitudes below 1,000 m except in flooded alluvial plains. Whinchat reproductive success, the timing of haymaking and meadow bird density were assessed in 2003 in six areas selected in three different flooded plains, in five areas from two massifs at altitudes ranging from 990 to 1,250 m, and in 2004 in six areas of three flooded plains, in seven areas from three massifs at altitudes ranging from 1,200 to 2,000 m. The percentage of whinchat territories in which juveniles were observed was negatively correlated with mown areas at the time when 80% of hatched broods (observation of prey carryings by adults) would theoretically be fledged. Additionally, assessed hatching success was negatively correlated with early haymaking in 2003 and with meadow passerine territory density in 2004. In upland meadows, whinchat populations exhibited either low reproductive success and low density (1,200 m) or high reproductive success and high density (1,200 m). In lowland flooded meadow however, high density could match low reproductive success and whinchat population then acts as a sink population. We conclude that adequate agri-environmental policy should not focus only on lowland meadows, even if the highest meadow bird diversity is often found there.     

甘南亚高寒草甸稀有种对物种多样性和物种多度分布格局的贡献

稀有种不仅影响群落的物种多度分布格局, 同时也是α多样性的重要贡献者。本研究主要通过加性分配和Fortran软件的RAD程序包拟合的方法, 研究了甘南亚高寒草甸不同坡向物种多样性及多度分布格局的变化, 分析了物种多度分布格局及其α多样性的变化特征, 确定了稀有种在物种多度分布格局中的相对贡献。结果表明: (1)在南坡到北坡的变化中, 环境因子差异比较明显, 其中, 土壤全磷、有机碳、速效磷、碳氮比及含水量呈递增趋势; 土壤氮磷比和pH值呈递减趋势; 土壤全氮在西坡显著低于其他坡向, 而速效氮在所有坡向上差异不显著。(2)稀有种对群落物种多样性的影响在南-北坡向梯度上依次增大, 去除稀有种的影响在各坡向均高于去除非稀有种, 可见, 稀有种在甘南亚高寒草甸物种多样性中的相对贡献高于非稀有种。(3)各坡向的稀有种资源获取模式以随机分配占领模式(random fraction模型)为主, 而非稀有种则以生态位优先占领模式(geometric series模型)为主。由于稀有种有较大的扩散率, 在物种多样性较高的生态系统中, 物种之间的生态位重叠会更加明显, 从而抑制物种多样性的增加, 因此能达到维持原有物种多样性的目的。     

高寒草甸物种多样性对藏系牧羊放牧行为的影响

为探究草原植物物种多样性对家畜放牧行为的影响及其机制,在青藏高原高寒草甸开展藏系牧羊轮牧试验,调查植被物种多样性,观察藏系牧羊采食速率、觅食速率和采食时间,并计算藏系牧羊日采食量。结果表明：两年间,植物物种丰富度与藏系牧羊采食速率呈显著正相关关系（P<0.05）;觅食速率、采食时间和日采食量对放牧率响应敏感（P<0.05）,呈夏秋增冬春减的趋势。植物Shannon-Wiener指数与藏系牧羊的采食时间显著负相关（P<0.05）;在暖季或8羊/hm²放牧率下植物Shannon-Wiener指数与藏系牧羊日采食量呈显著正相关（P<0.05）。Pilelou均匀度指数与藏系牧羊采食速率和采食时间显著负相关（P<0.05）;在暖季或8羊/hm²放牧率下Pilelou均匀度指数与藏系牧羊日采食量呈显著负相关（P<0.05）。植物物种丰富度对藏系牧羊放牧行为贡献较大,且放牧藏系牧羊的采食速率和采食时间比觅食速率和日采食量对植物物种丰富度响应更敏感,以用植物物种丰富度为自变量可以更好预测藏系牧羊放牧行为。放牧管理通过影响植被物种多样性从而进一步影响了藏系牧羊放牧行为。放牧行为不仅是评价草地营养价值和家畜生产力的关键指标,也是草地健康管理的基础。因此,明确草原植物物种多样性-藏系牧羊放牧行为的互作机制有助于更好的提高藏系牧羊地生产力,维护草原生态健康。