Taxonomic and functional characteristics of field edge weed communities along a gradient of crop management intensity

The widespread loss of weed diversity and associated ecosystem functions is raising important concerns. Field edges could play a major role in the maintenance of weed functional diversity in arable landscapes as these habitats still harbour high weed diversity, owing to either a reduced farming management intensity and/or to a spillover of species from adjacent perennial field margins. Here, we investigated the taxonomic and functional characteristics of weed species recorded in surveys of field edges and their associated field cores over six consecutive years in 60 arable fields farmed with five crop management strategies. We found that field edges were richer, with species more functionally diverse and composition more stable over years than field core surveys. The distribution of individual functional traits differed between field edges and field cores, with higher values for seed mass and nitrophily (Ellenberg.N), and a wider distribution of specific leaf area values in field edges. The bimodal distribution of plant height and germination period observed in field edges became unimodal in field cores. Field edges harboured species with ecological strategies associated with field cores (ruderal species) plus a conservative strategy which could be explained by a spillover from the adjacent perennial field margins. Crop management strategies impacted field edge flora, though to a lesser extent than the field core flora whereas the functional differences between the field edge and the field core flora were less marked when crop management intensity was lower. These results indicate that field edges harbour a unique assemblage of species and highly contribute to the maintenance of weed diversity in arable landscapes. Future studies should thus focus on the importance of these specific functional traits to the agroecosystem functioning.     

Effects of experimentally planting non-crop flowers into cabbage fields on the abundance and diversity of predators

Flowery field margins and intersowing of crops with flowers are used as management practices to promote arthropod biodiversity as well as biocontrol agents. Positive effects of enhancement (in abundance and species richness) of hymenopteran parasitoids on control of Lepidoptera pests have previously been demonstrated. However, effects on predatory arthropods, which may also serve as pest control agents, remain unclear. In an experimental study in cabbage fields we tested how sown flower strips on field margins and intersowing with cornflower affected the species richness, abundance and community composition of ground beetles and spiders. Furthermore, we investigated whether effects of flower margins are dependent on the distance from the field margins. We found that field margins generally harboured higher species richness, whereas effects on abundance were weaker. Intersown cornflower had positive effects on spider and ground beetle abundance, but affected species richness only weakly. Our results do not provide evidence for effects of distance from the flowery field margins on predator richness or abundance. Species composition was strongly affected by the habitat management actions. We conclude that habitat management practices like flower strips on field margins and intersowing with flowers, which are primarily added to attract and enhance parasitoids for pest control, also benefit biodiversity conservation in spiders and ground beetles. They also positively affect the abundance of these primarily predatory taxa, which adds to the biocontrol potential of non-crop flowering plants.     

Enhancing the diversity of breeding invertebrates within field margins of intensively managed grassland: Effects of alternative management practices

Severe declines in biodiversity have been well documented for many taxonomic groups due to intensification of agricultural practices. Establishment and appropriate management of arable field margins can improve the diversity and abundance of invertebrate groups; however, there is much less research on field margins within grassland systems. Three grassland field margin treatments (fencing off the existing vegetation “fenced”; fencing with rotavation and natural regeneration “rotavated” and; fencing with rotavation and seeding “seeded”) were compared to a grazed control in the adjacent intensively managed pasture. Invertebrates were sampled using emergence traps to investigate species breeding and overwintering within the margins. Using a manipulation experiment, we tested whether the removal of grazing pressure and nutrient inputs would increase the abundance and richness of breeding invertebrates within grassland field margins. We also tested whether field margin establishment treatments, with their different vegetation communities, would change the abundance and richness of breeding invertebrates in the field margins. Exclusion of grazing and nutrient inputs led to increased abundance and richness in nearly all invertebrate groups that we sampled. However, there were more complex effects of field margin establishment treatment on the abundance and richness of invertebrate taxa. Each of the three establishment treatments supported a distinct invertebrate community. The removal of grazing from grassland field margins provided a greater range of overwintering/breeding habitat for invertebrates. We demonstrate the capacity of field margin establishment to increase the abundance and richness in nearly all invertebrate groups in study plots that were located on previously more depauperate areas of intensively managed grassland. These results from grassland field margins provide evidence to support practical actions that can inform Greening (Pillar 1) and agri‐environment measures (Pillar 2) of the Common Agricultural Policy (CAP). Before implementing specific management regimes, the conservation aims of agri‐environment measures should be clarified by defining the target species or taxonomic groups.     

施肥和杂草多样性对土壤微生物群落的影响

常年使用化肥和除草剂以及农业新技术的高投入,使我国粮食主产区耕地出现了生产力降低、土壤生物多样性失调和污染严重等生态问题。采用磷脂脂肪酸(PLFA)方法来评估施肥和杂草多样性对冬小麦土壤微生物群落结构的影响。实验采用裂区实验设计,施肥作为主因素,杂草多样性作为次因素。化肥和有机肥两个施肥处理,在两个施肥处理中进行杂草多样性设置,实验盆中心种植作物(冬小麦8株),四周种植杂草(8株),杂草种类选择野燕麦、苜蓿、菊苣、播娘蒿。杂草多样性处理设为0、1、2、4种杂草处理,0种杂草处理仅种植作物,有6盆;1种杂草处理为每盆种1种杂草,有12盆;2种杂草处理为每盆种两种杂草,有12盆;4种杂草处理为每盆种4种杂草,有6盆。结果表明:在两种施肥处理中,增加杂草多样性显著增加了土壤碳氮比和p H值,碳氮比都是在4种杂草处理中最高。施化肥处理中,增加杂草多样性显著影响真菌和细菌比,真菌和细菌比在4种杂草处理中最大,显著高于0、1、2种杂草处理。在施有机肥处理中,增加杂草多样性显著影响阳性菌和阴性菌比,阳性菌和阴性菌比在0种杂草处理中最低,显著低于1、2、4种杂草处理。在两个施肥处理中,土壤碳氮比与各类群微生物量显著相关,杂草多样性通过改变土壤碳氮比改变微生物群落构成,并且微生物群落结构转变方式不同。     

The role of various meadow margin types in shaping carabid and staphylinid beetle assemblages (Coleoptera: Carabidae,Staphylinidae) in meadow dominated landscapes

Less intensively managed semi-natural habitats, e.g., field and meadow margins like hedgerows, are thought to be crucial landscape components for maintaining biodiversity in highly disturbed and intensively managed agricultural landscapes. In this study, we focused on the effects of three meadow margin types on activity-density, species richness and species composition of carabid and staphylinid beetles recorded by pitfall traps in Central European landscapes dominated by intensively managed meadows. Carabid activity-density was significantly higher in meadows than in meadow margins and within meadow margins their activity-density increased from grassy meadow margins via shrubby ones to woody meadow margins. We found that recorded species richness of both carabid and staphylinid beetles was not significantly affected by habitat identity (meadow margin or neighbouring meadow) and meadow margin type. Recorded species composition of both investigated taxa was significantly affected by habitat identity and interaction between habitat identity and meadow margin type (i.e. it differed between particular meadow margin types). Assemblages inhabiting various meadow margin types were more dissimilar between each other than assemblages from neighbouring meadows. Meadow margins within grassland dominated landscapes maintain local species richness by hosting different species from those living in surrounding meadows. Dissimilarity of carabid and staphylinid assemblages from meadows neighbouring both sides of particular meadow margin did not differ between meadow margin types. Our results indicate that semi-natural habitats play an important role in maintaining biodiversity not only in agricultural landscapes dominated by arable fields, but also in those dominated by meadows.     

农田边界生物多样性保护功能的初步研究——以北京东北旺步甲群落多样性研究为例

农田边界是农田间的过渡带 ,包含了树篱、防护林、草皮 (带 )、墙、篱笆、沟渠、道路、作物边界带等景观要素[3] 。许多研究表明 ,农田边界在保护生物多样性方面有着重要的作用。Ｄｅｎｎｉｓ等[7] 的研究表明 ,通过为节肢动物提供多样、稳定的栖息地和越冬场所 ,增加农田中节肢动物的多样性。Ｈｏｌｌａｎｄ等[12 ] 的研究也表明 ,林地边界在农业生态系统中能起到保护生物多样性的作用 ,这种作用不仅使林地中有较高的多样性 ,而且还使相邻农田生物多样性增加。同时 ,多样化的农田生态系统比纯作系统具有更为丰富和多样的害虫天敌[6 ] 。国…     

Relationship between species richness and spatial and temporal distance from seed source in semi‐natural grassland

Question: How do traditional management practices of field margins maintain the biodiversity of native grassland species? Location: Semi‐natural grassland on the field margins of traditional and consolidated agricultural fields on Awaji Island, central Japan. Methods: The distance to the nearest traditional field margin to the study sites was determined because the traditional field was considered as a seed source of native vegetation to the semi‐natural grasslands under study. We selected field margins in consolidated fields of different ages and distances from seed sources. Indicator species for both field types were sought. Regression analysis and detrended correspondence analysis (DCA) were used to determine the effect of spatial and temporal distances on the species composition of native vegetation. Results: Species richness differed significantly between the margin of traditional and consolidated fields. We identified significant indicator species of traditional fields, but not of consolidated fields. In consolidated fields, species richness increased significantly with age and decreased significantly with increasing distance to the source. At younger sites, species richness decreased faster with distance to the source because of strong negative correlation, but not at older sites. DCA ordination plots similarly indicated that similarities of vegetation composition in consolidated and traditional fields decreased with distance, and the effect of distance decreased with age. Conclusions: The species composition of the grassland margins of consolidated field was more similar to the margins of traditional fields if the consolidated fields were older, and/or closer to traditional fields. This pattern suggests that dispersal may play a role in the establishment of species on field margins.     

Biodiversity and agro-ecology in field margins

This multidisciplinary study investigates agro-ecological functions (nature conservation, agriculture, environment) and implications of newly created, mown sown and unsown field margin strips installed on ex-arable land to increase biodiversity. From conservational concern, the development of species rich field margin strips was not strongly affected by the installed type of margin strip since species diversity converged over time, whether strips were sown or not. Convergence between unsown and sown margin strips occurred also in terms of species composition: unsown and sown strips became similar over time. Mowing without removal of cuttings significantly reduced species richness, yielded more grassy margin strips and delayed similarity in species composition between sown and unsown margin strips. Species richness on the longer term was not significantly affected by light regime nor by disturbance despite significant temporary effects shortly after the disturbance event. On the contrary vegetation composition in terms of importance of functional groups changed after disturbance: the share of spontaneous species within functional groups increased resulting in higher similarity between the sown and unsown vegetation. Furthermore risk of invasion was highest in the disturbed unsown community on the unshaded side of a tree lane. A positive effect of botanical diversity on insect number and diversity was found. However the effects of botanical diversity on insect number was mediated by light regime. At high light availability differences between plant communities were more pronounced compared to low light availablilty. The abundance of some insect families was dependent on the vegetation composition. Furthermore light availability significantly influenced insect diversity as well as the spatial distribution of families. From agricultural concern, installing margin strips by sowing a species mixture and a mowing regime with removal of cuttings are good practices to diminish the risk of species ingrowth into adjacent crops by creeping roots and rhizomes. Seed dispersal was only problematic one year after the installation of the field margin strips particularly nearby the unsown margin strip and wind-borne seeds were dispersed over limited distances, mainly within 4 m of field margins. Annual herbage yield was not affected by mowing management. DM yield of sown/unsown communities converged over time. Compared to herbage from an intensively managed fertilized grassland, field margin herbage revealed a low feeding value, owing to a low crude protein content, a low digestibility and a high crude fibre content. The unsown community had a higher forage quality than communities sown to bred commercially available grass varieties. Both digestibility and crude protein content decreased over time irrespective of plant community or location. Mid June cuts were more productive than mid September cuts but digestibility and crude protein content was lower. The use of herbage from field margins as hay for horses or as a component in farmland compost are good alternatives. A strong relation was found between the distribution of pest insects and their antagonist families along field margin strips indicating a status of biological equilibrium. From environmental concern, field margin strips buffered boundary vegetation and watercourses against cropped areas loaded with high levels of mineral nitrogen. Margin strips reduced the mineral nitrogen content of the soil in the margin and mineral nitrogen loss during wintermonths. Mineral nitrogen loss was not affected by field margin type but by distance from the field crop. A minimal width of 5 m is necessary to reach an optimal reduction in mineral soil N and N losses.     

Hedgerows support rich communities of harvestmen (Opiliones) in upland agricultural landscape

Hedgerows play important roles in agricultural landscapes and they increase biodiversity by providing habitat refugia for species sensitive to agricultural disturbance. We have studied the characteristics of the communities of harvestmen (Opiliones) inhabiting hedgerows. Harvestmen are terrestrial arachnids associated with soil surface and subsurface and sensitive to land-use and disturbance. We were specifically interested in quantifying how hedgerow characteristics (e.g., elevation, length, width, connectivity, and plant diversity) affect harvestman diversity and community composition. We expected harvestman diversity and community composition to be positively related to both hedgerow size (area, length, width) and biological attributes of hedgerows (e.g., connectivity, plant community diversity). We surveyed hedgerow characteristics and harvestman communities of 20 hedgerows in an upland agricultural landscape in the Western Carpathians. Hedgerow characteristics were measured in the field or derived from GIS layers and we used correlation and ordination methods to relate them to harvestman community metrics. We found surprisingly high taxonomic richness of harvestmen within the studied hedgerows (15 species). Importantly, the Shannon index of harvestman communities was positively related to hedgerow length and hedgerow tree layer species richness and diversity. Harvestman community composition varied with hedgerow area and width. Despite their small total area, hedgerows represented an important habitat for diverse harvestman communities and hedgerow attributes such as size and tree diversity significantly affected the composition and the Shannon index of harvestman communities. Thus, greater lengths and widths of hedgerows can provide habitats for a higher Shannon index of harvestman communities, within surrounding agricultural landscapes.     

Functional response of plant assemblages to management practices in road–field boundaries

Questions

Management practices implemented on road verges are partly established to preserve biodiversity in agricultural landscapes. Their evaluation was primarily based on the analysis of the taxonomic structure and composition of communities. What is the relationship between management practices and the functional characteristics of road–field plants within elements?

Location

West‐central France.

Methods

We sampled the berm, the embankment and the field margin of 40 road–field boundaries located in west‐central France, an area where delayed mowing of some berms has been practised since 2009 for biodiversity reasons. We characterized management practices implemented on the different elements, i.e., the frequency and timing of mowing (early summer or late summer), the frequency of herbicide treatment in field margins and the N input rate. We retrieved from databases seven functional traits and types known to be influenced by management practices. To identify relationships between traits or types and environmental variables we first performed partial RLQ analyses to remove any potential confounding effect of the landscape context studied. We then computed fourth‐corner statistics to quantify relationships between traits or types, environmental variables and partial RLQ axes.

Results

Late mowing of the berm promoted nitrophilous species within berms and competitive rather than ruderal species within arable field margins. The frequency of herbicide treatment in field margins promoted broad‐leaf species within this element and, to a lesser extent, within embankments. Finally, the functional characteristics of communities of the three elements were not influenced by the level of N input in field margins.

Conclusions

In our environmental context, managing road verges affected the functional structure of plant assemblages both within them and within their adjacent arable field margins. We suggest a single early mowing of berms as a valuable practice for both conservation purposes and weed risk control in adjacent field margins.     

Agricultural matrix provides modest habitat value for ants on mixed farms in eastern Australia

Agricultural development has contributed to the global erosion of biodiversity. The farmed matrix in agricultural landscapes can and must be important for the conservation of biodiversity and provision of ecosystem services, but this assumes that the matrix has biodiversity value. We investigate the contribution of pastures and crops to ant diversity on mixed farms in eastern Australia. Remnant native woodlands, pastures of native grasses, sown pastures of exotic species, and crops were sampled for epigaeic ants on 3 farms using pitfall trapping. Ants were sorted to species and assigned to functional groups. Ant species richness and functionality followed consistent patterns across the three farms. Significant differences in assemblage composition were found between the major habitat types, and in species richness between woodland and non-woodland habitats (native and sown pastures, and crops), which did not contribute appreciably to farm-level biodiversity: 1–10% of species were found only in the farmed matrix. Insect conservation in agricultural landscapes is important for the provision of ecosystem services, including pest control and the maintenance of soil condition. As the farmed matrix makes only a modest contribution to farm-scale biodiversity, appropriate management of the unfarmed parts of the landscape is critical and habitat restoration may be warranted where the level of native vegetation is low. Maintaining a mix of land uses within the production matrix will also be a necessary bet-hedging strategy in a world with changing climates, commodities, community expectations and farming practices.     

Biodiversity effects on ecosystem functioning in a 15-year grassland experiment: Patterns,mechanisms, and open questions

In the past two decades, a large number of studies have investigated the relationship between biodiversity and ecosystem functioning, most of which focussed on a limited set of ecosystem variables. The Jena Experiment was set up in 2002 to investigate the effects of plant diversity on element cycling and trophic interactions, using a multi-disciplinary approach. Here, we review the results of 15 years of research in the Jena Experiment, focussing on the effects of manipulating plant species richness and plant functional richness. With more than 85,000 measures taken from the plant diversity plots, the Jena Experiment has allowed answering fundamental questions important for functional biodiversity research.First, the question was how general the effect of plant species richness is, regarding the many different processes that take place in an ecosystem. About 45% of different types of ecosystem processes measured in the ‘main experiment’, where plant species richness ranged from 1 to 60 species, were significantly affected by plant species richness, providing strong support for the view that biodiversity is a significant driver of ecosystem functioning. Many measures were not saturating at the 60-species level, but increased linearly with the logarithm of species richness. There was, however, great variability in the strength of response among different processes. One striking pattern was that many processes, in particular belowground processes, took several years to respond to the manipulation of plant species richness, showing that biodiversity experiments have to be long-term, to distinguish trends from transitory patterns. In addition, the results from the Jena Experiment provide further evidence that diversity begets stability, for example stability against invasion of plant species, but unexpectedly some results also suggested the opposite, e.g. when plant communities experience severe perturbations or elevated resource availability. This highlights the need to revisit diversity–stability theory.Second, we explored whether individual plant species or individual plant functional groups, or biodiversity itself is more important for ecosystem functioning, in particular biomass production. We found strong effects of individual species and plant functional groups on biomass production, yet these effects mostly occurred in addition to, but not instead of, effects of plant species richness.Third, the Jena Experiment assessed the effect of diversity on multitrophic interactions. The diversity of most organisms responded positively to increases in plant species richness, and the effect was stronger for above- than for belowground organisms, and stronger for herbivores than for carnivores or detritivores. Thus, diversity begets diversity. In addition, the effect on organismic diversity was stronger than the effect on species abundances.Fourth, the Jena Experiment aimed to assess the effect of diversity on N, P and C cycling and the water balance of the plots, separating between element input into the ecosystem, element turnover, element stocks, and output from the ecosystem. While inputs were generally less affected by plant species richness, measures of element stocks, turnover and output were often positively affected by plant diversity, e.g. carbon storage strongly increased with increasing plant species richness. Variables of the N cycle responded less strongly to plant species richness than variables of the C cycle.Fifth, plant traits are often used to unravel mechanisms underlying the biodiversity–ecosystem functioning relationship. In the Jena Experiment, most investigated plant traits, both above- and belowground, were plastic and trait expression depended on plant diversity in a complex way, suggesting limitation to using database traits for linking plant traits to particular functions.Sixth, plant diversity effects on ecosystem processes are often caused by plant diversity effects on species interactions. Analyses in the Jena Experiment including structural equation modelling suggest complex interactions that changed with diversity, e.g. soil carbon storage and greenhouse gas emission were affected by changes in the composition and activity of the belowground microbial community. Manipulation experiments, in which particular organisms, e.g. belowground invertebrates, were excluded from plots in split-plot experiments, supported the important role of the biotic component for element and water fluxes.Seventh, the Jena Experiment aimed to put the results into the context of agricultural practices in managed grasslands. The effect of increasing plant species richness from 1 to 16 species on plant biomass was, in absolute terms, as strong as the effect of a more intensive grassland management, using fertiliser and increasing mowing frequency. Potential bioenergy production from high-diversity plots was similar to that of conventionally used energy crops. These results suggest that diverse ‘High Nature Value Grasslands’ are multifunctional and can deliver a range of ecosystem services including production-related services.A final task was to assess the importance of potential artefacts in biodiversity–ecosystem functioning relationships, caused by the weeding of the plant community to maintain plant species composition. While the effort (in hours) needed to weed a plot was often negatively related to plant species richness, species richness still affected the majority of ecosystem variables. Weeding also did not negatively affect monoculture performance; rather, monocultures deteriorated over time for a number of biological reasons, as shown in plant-soil feedback experiments.To summarize, the Jena Experiment has allowed for a comprehensive analysis of the functional role of biodiversity in an ecosystem. A main challenge for future biodiversity research is to increase our mechanistic understanding of why the magnitude of biodiversity effects differs among processes and contexts. It is likely that there will be no simple answer. For example, among the multitude of mechanisms suggested to underlie the positive plant species richness effect on biomass, some have received limited support in the Jena Experiment, such as vertical root niche partitioning. However, others could not be rejected in targeted analyses. Thus, from the current results in the Jena Experiment, it seems likely that the positive biodiversity effect results from several mechanisms acting simultaneously in more diverse communities, such as reduced pathogen attack, the presence of more plant growth promoting organisms, less seed limitation, and increased trait differences leading to complementarity in resource uptake. Distinguishing between different mechanisms requires careful testing of competing hypotheses. Biodiversity research has matured such that predictive approaches testing particular mechanisms are now possible.     

Effects of maternal genotypic identity and genetic diversity of the red mangrove Rhizophora mangle on associated soil bacterial communities: A field‐based experiment

Loss of plant biodiversity can result in reduced abundance and diversity of associated species with implications for ecosystem functioning. In ecosystems low in plant species diversity, such as Neotropical mangrove forests, it is thought that genetic diversity within the dominant plant species could play an important role in shaping associated communities. Here, we used a manipulative field experiment to study the effects of maternal genotypic identity and genetic diversity of the red mangrove Rhizophora mangle on the composition and richness of associated soil bacterial communities. Using terminal restriction fragment length polymorphism (T‐RFLP) community fingerprinting, we found that bacterial community composition differed among R. mangle maternal genotypes but not with genetic diversity. Bacterial taxa richness, total soil nitrogen, and total soil carbon were not significantly affected by maternal genotypic identity or genetic diversity of R. mangle. Our findings show that genotype selection in reforestation projects could influence soil bacterial community composition. Further research is needed to determine what impact these bacterial community differences might have on ecosystem processes, such as carbon and nitrogen cycling.     

Agroecological transition increases arthropod diversity and decreases herbivore abundance on field margins

1. In peri-urban areas, many farmers are transitioning from conventional agriculture to agroecological practices to reduce pesticide input and preserving ecosystem services such as natural pest control. Field margins represent a stable habitat for arthropods, but community structure depends on many factors, including management type and vegetation features.
2. We studied the effects of agroecological transitions and vegetation features on arthropods of horticultural field margins, focusing on three feeding guilds (herbivores, predators and parasitoids). We sampled arthropods using the beat-sheet method in five conventional fields and five under agroecological transition. We also measured vegetation height, richness, flower abundance and plant cover.
3. Our results showed that arthropod diversity was higher in agroecological fields whereas herbivore abundance was lower, with a consistent pattern across most taxonomic orders. Vegetation features displayed multiple effects among functional and taxonomic groups. Herbivores did not respond to most vegetation variables whereas predators correlated with several, with similar trends among orders.
4. We conclude that agroecological transitions and field margins with high vegetation richness and floral resources influence arthropod communities with potential benefits regarding pest regulation. These practices might be more effective if considered alongside other methods that enhance biodiversity and if they are consistent at a landscape scale.

     

高寒草甸不同草地类型功能群多样性及组成对植物群落生产力的影响

对不同类型草地功能群多样性和组成与植物群落生产力之间的关系进行了探讨。结果表明：(1)在矮嵩草(Kobresia humlis)草甸和金露梅(Potentilla froticosa)灌丛中,豆科植物的作用比较明显,而其他功能群植物的作用较弱。(2)在藏嵩草(Kobresia tibetica)沼泽化草甸和小嵩草(K．pygmaca)草甸中,虽然杂类草、C3植物和莎草科植物功能群的生产力占群落初级生产力的比例较大,但二者在统计上没有显著性差异,这表明群落生产力除受物种多样性的影响外,也受物种本身特征和环境资源的影响,更主要的是受到功能群内物种密度和均匀度的影响,即功能群组成比功能群多样性更能说明对生态系统过程的影响。(3)不同类型草地群落植物功能群盖度与群落初级生产力呈显著的线性相关。(4)不同类型草地群落生产力与功能群内物种数的变化均表现为单峰曲线关系,即功能群内物种数处于中间水平时,群落生产力最高。     

Linking Land‐Use Scenarios,Remote Sensing and Monitoring to Project Impact of Management Decisions

Large‐scale modifications of natural ecosystems lead to mosaics of natural, semi‐natural and intensively used habitats. To improve communication in conservation planning, managers and other stakeholders need spatially explicit projections at the landscape scale of future biodiversity under different land‐use scenarios. For that purpose, we visualized the potential effect of five forest management scenarios on the avifauna of Kakamega Forest, western Kenya using different measures of bird diversity and GIS data. Future projections of bird diversity combined: (1) remotely sensed data on the spatial distribution of different forest management types; (2) field‐based data on the biodiversity of birds in the different management types; and (3) forest management scenarios that took into account possible views of various stakeholder groups. Management scenarios based on the species richness of forest specialists were very informative, because they reflected differences in the proportions of near‐natural forest types among the five scenarios. Projections based on community composition were even more meaningful, as they mirrored not only the proportions of near‐natural forest types, but also their perimeter to area ratios. This highlights that it is important to differentiate effects of the total area of available habitat and the degree of habitat fragmentation, both for species richness and community composition. Furthermore, our study shows that an approach that combines land‐use scenarios, remote sensing and field data on biodiversity can be used to visualize future biodiversity. As such, visualizations of alternative scenarios are valuable for successful communication about conservation planning considering different groups of stakeholders in species‐rich tropical forests.     

农田景观和管理方式对稻田系统植物多样性的复合影响

农田生物多样性对于维持农田生态系统服务功能和农业可持续发展具有重要意义.为揭示农田景观特征和管理方式对农田生态系统植物群落和物种多样性的影响,以有机稻田(ON)、常规化防稻田(天然林脚下,CN)、常规化防稻田(距天然林>10km,CF)系统为研究对象,调查了田内、田埂和沟渠生境的植物物种组成和多样性特征,并对三种类型稻...     

Temperate forest fragments maintain aboveground carbon stocks out to the forest edge despite changes in community composition

Edge effects are among the primary mechanisms by which forest fragmentation can influence the link between biodiversity and ecosystem processes, but relatively few studies have quantified these mechanisms in temperate regions. Carbon storage is an important ecosystem function altered by edge effects, with implications for climate change mitigation. Two opposing hypotheses suggest that aboveground carbon (AGC) stocks at the forest edge will (a) decrease due to increased tree mortality and compositional shifts towards smaller, lower wood density species (e.g., as seen in tropical systems) or, less often, (b) increase due to light/temperature-induced increases in diversity and productivity. We used field-based measurements, allometry, and mixed models to investigate the effects of proximity to the forest edge on AGC stocks, species richness, and community composition in 24 forest fragments in southern Quebec. We also asked whether fragment size or connectivity with surrounding forests altered these edge effects. AGC stocks remained constant across a 100 m edge-to-interior gradient in all fragment types, despite changes in tree community composition and stem density consistent with expectations of forest edge effects. We attribute this constancy primarily to compensatory effects of small trees at the forest edge; however, it is due in some cases to the retention of large trees at forest edges, likely a result of forest management. Our results suggest important differences between temperate and tropical fragments with respect to mechanisms linking biodiversity and AGC dynamics. Small temperate forest fragments may be valuable in conservation efforts based on maintaining biodiversity and multiple ecosystem services.     

Butterfly diversity at the ecotone between agricultural and semi‐natural habitats across a climatic gradient

Aim Understanding the response of species to ecotones and habitat edges is essential to designing conservation management, especially in mosaic agricultural landscapes. This study examines how species diversity and composition change with distance from semi‐natural habitats, over ecotones into agricultural fields, and how within‐site patterns of community transition change across a climatic gradient and differ between crop types. Location A total of 19 sites in Israel where semi‐natural habitats border agricultural fields (wheat fields or olive groves) distributed along a sharp climatic gradient ranging between 100 and 800 mm mean annual rainfall. Methods  We performed butterfly surveys in 2006. We analysed species richness (α‐diversity), diversity, community nestedness and species turnover (β‐diversity) within sites and between sites (γ‐diversity). We also assessed where species of conservation concern occurred. Results In wheat sites, richness and diversity declined abruptly from ecotones to fields and remained homogenously poor throughout the fields, regardless of climate. In olive sites, despite the sharp structural boundary, richness and diversity remained high from the semi‐natural habitat to the grove margins and then declined gradually into groves. Species of conservation concern occurred across all habitats at olive sites, but none were found inside wheat fields or at their ecotones. The contrast in community structure between semi‐natural habitats and fields was affected by both climate and field type. Irrigation in arid regions did not augment species diversity. Main conclusions Our results indicate that consideration of crop type, within a climatic context, should receive high priority in biodiversity conservation in agricultural areas. In ‘hostile’ crops, such as wheat, we suggest favouring a combination of high‐intensity management and wide margins over less intensive management without margins, which may merely aid generalist butterfly species. The scarcity of butterflies in arid irrigated fields suggests a need to carefully assess the effects of irrigation and agrochemicals on species’ communities.     

耕作方法和除草剂对玉米田杂草群落的影响

应用群落生态学方法,在中国科学院沈阳生态实验站对玉米田杂草群落进行了调查研究,探讨了耕作方法和除草剂对杂草群落组成、多样性和生物量的影响.结果表明,玉米田优势种杂草为野黍、苘麻、大狼把草和鸭趾草,其中野黍重要值最高;免耕不施加除草剂处理6月下旬杂草生物量较大,5月末到8月中旬物种丰富度较高(S),7月1日和8月1日均匀度(J)较低,优势集中性(C)较高,均与常规施加除草剂处理有显著差异.施用除草剂可减少免耕玉米田杂草种类,抑制杂草生物量的增长.耕作方法和除草剂可对杂草群落组成、多样性及稳定性产生影响.