Influence Species Composition Research Articles

A meta-analysis of benthic rotifer community structure as a function of lake trophic state

Our understanding of the ecological drivers that control community structure of benthic rotifers is poorly known. By reviewing 21 papers on freshwater benthic rotifers we compiled an inventory of an additional 258 species, 27 genera, and six families not previously listed in the review of benthic, lotic rotifers by Ricci and Balsamo (Freshw Biol 44:15–28, 2000). This raises the number of reported benthic species to 416, ~ 23% of all rotifers. Using selected papers within our dataset we tested two hypotheses: (1) Within lakes of different trophic state benthic rotifer communities differ in their species composition and (2) because rotifer trophi types reflect strong specificity for certain foods, there is a difference in the distribution of trophi types in lakes of different trophic state. We found that the trophic state of water bodies influences species composition of benthic rotifers, but there was no significant difference in the distribution of their trophi types. To aid in understanding community assembly of benthic rotifers, we provide a list of knowledge gaps that future studies could address.

A stream by any other name: does β-diversity differ between Nearctic and Neotropical streams?

Beta diversity typically increases with decreasing latitude, with explanations of this pattern often based on tropical origins of most clades. Black flies (Diptera: Simuliidae) are at odds with this trend, having a northern origin. Increasing β-diversity with decreasing latitude might also be a product of changes in causal mechanisms structuring local assemblages among biogeographical realms. We tested the hypotheses that (i) β-diversity of black flies in streams should be similar between the Nearctic and Neotropical realms, and (ii) causal processes influencing species composition do not differ between these areas. To this end, we examined two Nearctic (USA) and two Neotropical data sets (Ecuador, Venezuela). Results did not show distinct differences in β-diversity between Nearctic and Neotropical streams. Although stream conditions varied among regions, we provide evidence that several causal mechanisms of community structure are shared. We suggest that potentially similar causal mechanisms driving species composition contributed to the lack of distinct differences in β-diversity between Nearctic and Neotropical streams. In addition, dispersal appears to influence the β-diversity of larval black flies, a pattern different from many previous studies of stream invertebrates. The influence of taxon origins on β-diversity across biogeographic realms should be further investigated.

Resilience of a native soil seed bank in a floodplain lake subjected to cropping, grazing and extended drought

Ephemeral floodplain lakes are an integral component of inland wetland ecosystems and experience highly variable hydrology and prolonged dry periods. Although wetland soil seed banks are highly resilient to drought and floods, anthropogenic land use may add an additional stress. Understanding the recovery potential of wetland soil seed banks to different historical land uses helps manage and prioritise environmental water. In this study we explored the resilience of the wetland plant community in an ephemeral floodplain lake (Ita Lake, NSW, Australia). We collected soil samples during an extended dry phase (10 years) from two distinct zones within the lake, one of which was subjected to historical grazing and the other to lakebed ploughing and cropping. The samples were inundated under multiple inundation regimes to assess soil seed bank response. We found that the soil seed bank was viable, indicating a level of resilience not previously recorded for some plant species, namely Ricciocarpus natans, Chara spp., Nitella spp., Alternanthera denticulata and Eleocharis acuta. Although the results highlight the resilience of ephemeral wetland plant communities, intensive land uses such as ploughing and cropping will limit the availability of seeds to germinate, and the inundation regime will influence species composition and the subsequent likelihood of restoration.

Effects of habitat edges on vegetation structure and the vulnerable golden-brown mouse lemur (Microcebus ravelobensis) in northwestern Madagascar

BackgroundEdge effects can influence species composition and community structure as a result of changes in microenvironment and edaphic variables. We investigated effects of habitat edges on vegetation structure, abundance and body mass of one vulnerable Microcebus species in northwestern Madagascar. We trapped mouse lemurs along four 1000-m transects (total of 2424 trap nights) that ran perpendicular to the forest edge. We installed 16 pairs of 20 m2 vegetation plots along each transect and measured nine vegetation parameters. To determine the responses of the vegetation and animals to an increasing distance to the edge, we tested the fit of four alternative mathematical functions (linear, power, logistic and unimodal) to the data and derived the depth of edge influence (DEI) for all parameters.ResultsLogistic and unimodal functions best explained edge responses of vegetation parameters, and the logistic function performed best for abundance and body mass of M. ravelobensis. The DEI varied between 50 m (no. of seedlings, no. of liana, dbh of large trees [dbh ≥ 10 cm]) and 460 m (tree height of large trees) for the vegetation parameters, whereas it was 340 m for M. ravelobensis abundance and 390 m for body mass, corresponding best to the DEI of small tree [dbh < 10 cm] density (360 m). Small trees were significantly taller and the density of seedlings was higher in the interior than in the edge habitat. However, there was no significant difference in M. ravelobensis abundance and body mass between interior and edge habitats, suggesting that M. ravelobensis did not show a strong edge response in the study region. Finally, regression analyses revealed three negative (species abundance and three vegetation parameters) and two positive relationships (body mass and two vegetation parameters), suggesting an impact of vegetation structure on M. ravelobensis which may be partly independent of edge effects.ConclusionsA comparison of our results with previous findings reveals that edge effects are variable in space in a small nocturnal primate from Madagascar. Such an ecological plasticity could be extremely relevant for mitigating species responses to habitat loss and anthropogenic disturbances.

Flow is more Important than Temperature in Driving Patterns of Organic Matter Storage and Stoichiometry in Stream Ecosystems

Understanding the connections between biological communities and elemental cycles is increasingly important given that alterations to both are occurring on a global scale. Biological control of elemental cycles is tied to patterns of biomass and the elemental stoichiometry of organisms and organic matter (OM) pools that comprise ecosystems. The structure and size of these ecosystem components are, in turn, shaped by key environmental factors that influence species composition, functional traits, and OM and element storage. In stream and river ecosystems, temperature and flow regime have a strong influence on ecosystem structure and function, yet little is known about their relative importance in driving patterns of ecosystem OM and stoichiometry. We quantified ecosystem OM pools and elemental stoichiometry in 11 Icelandic streams across a wide gradient of temperature (~ 5 to 25 °C) and flow. Across these environmental gradients, we observed two orders of magnitude variation in ecosystem OM mass, as well as relatively large variation in certain ecosystem stoichiometries (that is, C:N, C:P). We found that flow regime was more important than temperature in driving variation in OM pools and stoichiometry because of large shifts in community structure, that is, from dominance by large-bodied macrophyte and bryophyte communities to epilithic and detrital OM pools. Although temperature is known to influence mass-specific rates of metabolic and chemical processes, our study suggests that the flow disturbance regime may be the dominant control on patterns of OM storage and may thus control ecosystem fluxes by constraining ecosystem OM pool mass, organism size structure, and stoichiometric traits.

Species composition drives macroinvertebrate community classification

Community classification enables us to simplify, communicate, track and assess complex distribution patterns. Yet, the distribution of organisms may not coincide with predefined geographical and environmental boundaries, and therefore, biology itself should be leading the classification. In this study, we showed how to arrive at such a biology-based classification by clustering locations based on similarity in species composition. A hierarchical classification structure allowed for the selection of classification levels that suit multiple scales of analysis. We also showed how to objectively identify the number of clusters present in a dataset based on the distribution of specific indicator species, allowing to identify clear boundaries in species composition on multiple scales. The resulting biology-based clusters were identified and characterized by local and regional environmental conditions, showing the limited explanatory power of these environmental conditions and the added value of taking biology itself as a starting point of the classification. By departing community classification from species composition, the unknown environmental, geographical, and biotic drivers influencing species composition are accounted for.

Heathland plant species composition and vegetation structures reflect soil‐related paths of development and site history

AbstractQuestionsTo improve our knowledge on how environmental conditions determine the development of high‐value Calluna vulgaris heathland habitats, we studied the floristic and structural characteristics of heathland plant communities across North Germany and how they are influenced by edaphic, climatic and management factors. We ask how heathland development is related to these factors and what are the implications for conservation management and restoration.LocationNorth German Plain.MethodsWe collected 350 relevés in 18 dry Calluna heathland areas. Plant communities were classified using Isopam, and Redundancy Analysis (RDA) determined effects of environmental conditions. Potential pathways of development and the nature conservation status of the communities were identified on a multifactorial basis.ResultsWe found nine floristically and structurally distinct heathland plant communities. Heathland vegetation showed distinct patterns along Calluna age development stages and environmental conditions. Soil conditions and related effects of long‐term site history and recent management turned out to be the predominant factors influencing species composition and diversity, resulting in three potential heathland succession pathways. Mosaic‐like communities with particularly high taxonomic diversity and conservation value occurred on early‐successional inland dunes or as regeneration stage growing on nutrient‐poor sandy soils without humus accumulation.ConclusionsThe study reveals fundamental differences between historically farmed heathland in the oceanic Northwest and former military training areas mainly in northeastern Germany with consequences for restoration ecology. Present nature conservation criteria turned out to be insufficient in predicting habitat quality, as lichens are frequently disregarded. Our findings highlight the need for intense soil disturbance to maintain early‐stage soil conditions and a diverse Calluna growth‐phase composition, as these factors essentially determine species richness in lowland heaths.

Tree-circles spontaneous vegetation over a long climatic gradient

Urban flora varies between urban habitats within a city and between cities. We used a particular urban habitat - tree-circles to compare floristic differences between urban agglomerations along a long climatic gradient on a continental scale. We recorded flora of this unique habitat in seven West Balkan cities and compared it to seven cities from Western and Central Europe. On average, 91 species were found on tree-circles in every city in the Balkans (compared to 81 in continental Europe). Climate was the most important factor influencing species composition. Western and Central European tree-circles floras are much more uniform and homogeneous than Balkan ones, which have richer species pools.

Environmental factors that influence species diversity of floodplain plant communities in different flooding phases in the Okavango Delta, Botswana

Background and objectives: Species composition and distribution in seasonal floodplain plant communities are influenced by variation in flooding. However, the influence of intra-flooding variation phases on the diversity of seasonalfloodplain plant communities has not been studied in the Okavango Delta. The objective of this study was to investigate environmental factors that influence species composition and distribution of seasonal floodplain communities beforeand after flooding. It was hypothesised that environmental factors that influence the species composition and distribution in seasonal floodplain communities will vary with intra-flooding seasons.Methods: Flooding depth was measured in May (before flooding) and September (flood recession/after flooding) in forty 25 m2 plots. Flooding duration was recorded as the number of weeks in which the plots were inundated. The soil was sampled before and after floods and analysed for pH, extractable P, K, Mg, Ca and Na. Plant identification and estimation of percentage cover were done in the 25 m2 plots in which environmental variables were sampled. The relationshipbetween environmental variables and seasonal floodplain plant community composition and distribution was sought using Non-metric Multi-dimensional Scaling. Paired Student’s t test was used to compare the means of environmentalvariables before and after flooding.Results: Factors that influenced the distribution of species before flooding were Na, K, water depth and flooding duration. After flooding, the factors that influenced species composition and distribution were K, Na, Mg, pH, water depth and flooding duration.Conclusion: These results suggest that during flooding K and Mg are deposited in the floodplains due to lateral water flow. Our results also suggest that any water abstraction from the Okavango River Basin should take into consideration theimportance of flooding duration and depth in sustaining species composition and distribution of seasonal floodplain plant communities so that such developments do not disturb the ecological functioning of the Delta.

Fish assemblage composition within the floodplain habitat mosaic of a tropical lake (Tonle Sap, Cambodia)

Abstract Understanding how habitat heterogeneity is linked to biodiversity patterns within flood–pulse catchments is needed for their effective conservation. To study those communities, researchers have begun to explore how local environmental factors influence species composition patterns at relatively fine scales within complex habitat mosaics. However, a robust description of the link between communities’ composition and their floodplain habitat characteristics remains poorly articulated. In the Tonle Sap Lake (TSL) of Cambodia, we evaluated whether mesohabitat‐scale (1–5 km) factors throughout the floodplain structured the fish assemblage temporally and spatially. First, we determined whether TSL fish assemblage changed seasonally and, if so, what assemblage components were driving that change. Second, we determined whether environmental factors structured fish composition across floodplain mesohabitat patches during the wet season. Third, we evaluated whether dominant species displayed affinities for specific areas within the floodplain during the wet season, potentially identifying critical mesohabitat patches for the fish assemblage. Fish were collected from nine sites along an elevational gradient traversing the floodplain every 3 months from March 2014 through January 2015. Correspondence analysis and analysis of variance were used to assess seasonal variation in the species composition. Canonical correspondence analysis and a mantel test were then used to identify the significance of environmental factors structuring the fish assemblage. Fish assemblages changed across seasons; in particular, migratory species occurrence decreased during the dry season. During the wet season, the fish assemblage was structured spatially by mesohabitat‐scale factors such as vegetation and water quality. Furthermore, the flooded forest mesohabitat directly adjacent to the permanent lake displayed particularly high species richness and abundance. However, a majority of TSL species appeared to be highly mobile, occurring across multiple floodplain mesohabitats. We concluded that fish assemblage structure and floodplain mesohabitat use within TSL may depend strongly upon the maintenance of the natural flow regime. Since the flow regime will probably be modified by upstream dam development, trade‐offs will emerge between the cycle of fishing on which local residents depend, and the hydropower and agricultural benefits of damming the Mekong River system.

Forest complexity drives dung beetle assemblages along an edge‐interior gradient in the southwest Amazon rainforest

1. The habitat heterogeneity hypothesis predicts that heterogeneous habitats may provide more niches and diverse ways of exploiting environmental resources, thereby allowing more species to coexist, persist and diversify.2. We aimed to investigate how an edge‐interior gradient related to forest complexity influences species composition, abundance and richness of dung beetles in the western Amazon rainforest. We expected dung beetle abundance and richness to increase along the forest edge‐interior gradient, in accordance with the habitat heterogeneity hypothesis. We also expected strong changes in species composition driven by species turnover in the forest interior and nestedness along the forest edges. We sampled dung beetles using baited pitfall traps across an edge‐interior gradient. We also assessed the variation in forest features along the edge‐interior gradient to identify changes in forest complexity.3. Both species richness and abundance of dung beetles increased along the forest edge‐interior, following the gradient of forest complexity. The Sorensen dissimilarity of dung beetle assemblages was higher among sampling units placed near the forest edge, although neither turnover, nor nestedness was different between the extremes of the forest edge‐interior gradient. There was a clear compositional change along the edge‐interior gradient mostly driven by species turnover. Individual indicator value analysis revealed that species were strongly associated with the forest interior conditions.4. The simplification of the Amazon rainforest near clearings causes compositional changes in dung beetle assemblages. These changes are characterised by species‐poor and low‐abundance assemblages and may impair dung beetle ecological functions and therefore forest recovery.

Effects of field margins and other uncultivated fields on Orthoptera assemblages in the mountainous paddy field area of northeast Japan

To understand how farmlands help maintain biodiversity, we investigated the relationship between habitat heterogeneity and Orthoptera community composition on multiple spatial scales. First, we determined the impact of 12 environmental variables on the Orthoptera community diversity by sampling 37 quadrats in uncultivated fields over a broad spatial scale. Canonical correspondence analysis (CCA) demonstrated that environmental parameters influenced species composition. The first two canonical axes were associated with forest cover, grass (including harvested dried grass in some cases), bare or paddy fields, and plants with tall stems. Secondly, we conducted a local-scale survey of Orthoptera assemblages in an operational farm unit consisting of paddy fields, fallow fields, marginal grass fields, and secondary forests. Eleven Orthoptera species (46%) were found exclusively on specific vegetation types. Thirdly, we carried out a habitat-scale survey to elucidate the correspondence between consecutive spatial changes in vegetation and Orthoptera community composition in a paddy field and surrounding marginal fields. Even within narrower ranges, the compositional habitat heterogeneity induced changes in the dominant Orthoptera species composition. These results indicate that a high degree of habitat segregation occurs among Orthoptera species in field margins and in uncultivated fields, and that farmland management significantly affects spatial distribution of Orthoptera.

The influence of stand density on the structure of harvestmen communities (Opiliones) in a submountain beech forest

Abstract Modification of forest stand density by thinning is a common silvicultural practice implemented in management of production forests. However, changes in the stand density can entail considerable changes to the present forest environment and communities. The current knowledge about the effect of stand density modification on the local animal communities is based mainly on the flagship groups such as carabid beetles or birds. We focused our study on harvestmen. We explored how the stand density influences species composition of this species communities in submountain beech forests. The study was conducted in the Kováčovská dolina valley (Kremnické vrchy Mts, Central Slovakia) in 1997 and 1998, the method used was pitfall trapping. In total, 9 harvestmen species from 5 families were recorded. Prior to our research, the forest stands at the study locality were subject to thinning interventions the intensity of which influenced the structure of the local harvestmen communities. The most pronounced was the effect of very intensive thinning with stand density reduced below 0.5. From the recorded species, four preferred forest stands with lower stand density (Lophopilio palpinalis, Oligolophus tridens, Nemastoma lugubre, Trogulus nepaeformis), two species (Platybunus bucephalus, Dicranolasma scabrum) preferred forest stands with higher stand density. Generalization of the observed pattern requires to explore a wider spectrum of beech forests.

Late Holocene fire history and charcoal decay in subtropical dry forests of Puerto Rico

BackgroundFire is an important disturbance that influences species composition, community structure, and ecosystem function in forests. Disturbances such as hurricanes and landslides are critical determinants of community structure to Caribbean forests, but few studies have addressed the effect of paleofire disturbance on forests in Puerto Rico, USA. Soil charcoal is widely used to reconstruct fire history. However, the occurrence and frequency of paleofire can be underestimated due to charcoal decay.ResultsWe reconstructed the fire history of subtropical dry forests of Puerto Rico based on the analysis of soil macrocharcoal numbers adjusted by the negative exponential decay function of charcoal. Twenty-one fire events occurred over the last 1300 yr in the subtropical dry forest of northeastern Puerto Rico, and 10 fire events occurred over the last 4900 yr in the subtropical dry forest of southeastern Puerto Rico. The average turnover time of charcoal in these subtropical dry forest soils of Puerto Rico was 1000 to 1250 yr. Soil charcoal decay leads to an underestimation of one to two undetected fire events during the Late Holocene in the subtropical dry forests of Puerto Rico. The peak of paleofire events for subtropical dry forests in northeastern and southeastern Puerto Rico was broadly similar, occurring between 500 to 1300 calibrated years before present (cal yr BP; before present is understood to mean before 1950 AD). Fire frequency of the subtropical dry forests in Puerto Rico decreased after the immigration of Europeans in the past 500 yr. The fire that occurred between 4822 and 4854 cal yr BP can be interpreted as either a natural fire or a new record of a native peoples settlement in southeastern Puerto Rico. Fire became a frequent disturbance in the subtropical dry forest of Puerto Rico after the development of cultigens by native peoples.ConclusionsOur data suggested that fire was a frequent disturbance and human activity was likely a dominant cause of these paleofires in the subtropical dry forests of Puerto Rico.

Floristic composition and ecological gradient analyses of the Liakot Forests in the Kalam region of District Swat, Pakistan

Kalam Kohistan is a dry, temperate hilly region in the Hindu Raj Series of the Greater Hindu Kush Mountains with diverse forests. As plant distribution and composition is expression of a range of various environmental variables, ecological and floristic attributes of vegetation in the Laikot Forests were therefore evaluated via consecutive explorative trips. These forests have not been evaluated ecologically before due to harsh climatic conditions and issues of accessibility and the study in hand is one of the first in its nature. Quantitative ecological techniques were used to sample forest vegetation and identify species in quadrats of 2 m × 2 m for herbs, 5 m × 5 m for shrubs and 10 m × 10 m for trees. All the data of 195 plant species and environmental factors were analyzed via Two-way Cluster Analysis and Canonical Correspondence Analysis using PCORD and CANOCO software. Among 195 plant species from 63 families were 27 species of Asteraceae, the most-speciose family, followed by Poaceae (20 spp.). The dominant life form was therophyte (86 spp.; 44% share), followed by phanerophyte (41 spp.; 21% share). For the leaf size spectrum, most prevalent was nanophyll (73 spp.; 44%) followed by microphyll (66 spp., 34%) and mesophyll (44 spp.; 23%). Calcium carbonate, pH, potassium, sand, silt, organic matter, slope aspect and grazing significantly influenced species composition, distribution and habitat. The floristic variation in the region was diverse due to elevational and aspect gradients and thus devided into three zones. This vegetation zonation can be utilized for forest management, species and habitat conservation. Both in situ and ex situ conservation of threatened plant species may improve their conservation status in future if address properly.

Three-dimensional light structure of an upland Quercus stand post-tornado disturbance

Light is the most common limiting factor in forest plant communities, influencing species composition, stand structure, and stand productivity in closed canopy stands. Stand vertical light structure is relatively simple under a closed canopy because most light is captured by overstory trees. However, wind disturbance events create canopy openings from local to landscape scales that increase understory light intensity and vertical light structural complexity. We studied the effects of an EF-1 tornado on horizontal and vertical (i.e. three-dimensional) light structure within a Quercus stand to determine how light structure changed with increasing disturbance severity. We used a two-tiered method to collect photosynthetic photon flux density at 4.67 m and 1.37 m above the forest floor to construct three-dimensional light structure across a canopy disturbance severity gradient to see if light intensity varied with increasing tornado damage. Results indicate that increased canopy disturbance closer to the tornado track increased light penetration and light structure heterogeneity at lower forest strata. Increased light intensity correlated with increased sapling density that was more randomly distributed across the plot and had shifted light capture higher in the stand structure. Light penetration through the overstory was most strongly correlated with decreased stem density in the two most important tree species (based on relative dominance and relative density) in the stand, Quercus alba L. (r = − 0.31) and Ostrya virginiana (Mill.) K. Koch (r = − 0.27, p < 0.01), and indicated that understory light penetration was most affected by these two species. As managers are increasingly interested in patterning silvicultural entries on natural disturbances, they must understand residual stand and light structures that occur after natural disturbance events. By providing spatial light data that quantifies light structure post-disturbance, managers can use these results to improve planning required for long-term management. The study also provides comparisons with anthropogenic disturbances to the midstory that may offer useful comparisons to natural analogs for future silvicultural consideration.

Soil characteristics influence species composition and forest structure differentially among tree size classes in a Bornean heath forest

Whilst several studies have shown that edaphic variability influences species composition in nutrient-poor tropical forests, the determinants of local species distributions and, in particular, how these change from younger to mature individuals in such forests are still under debate, and have been poorly explored in tropical heath forests that are among the least fertile tropical forest ecosystems. We investigated the influence of soil fertility and topography on a Bornean heath forest species composition, α-, β-diversity and tree size structure among size classes by recording all trees ≥1 cm DBH in 16 forest plots totalling 0.36 ha. Tree species distributions generally followed gradients in available Al and soil depth; α- and β-diversity were linked to soil depth, and to some extent also to pH and the H:Al ratio. In contrast, forest structural attributes (basal area and stem density) were negatively correlated with both available and total P and a wider suite of soil nutrients, although trees ≥10 cm DBH were positively correlated with total P. Our study shows that heath forest species distribution, richness and structure is related to both edaphic and topographic characteristics and that soil acidity might have a strong influence in shaping these forests’ features. Among size classes, small trees are less influenced by soil and topography, whereas the sensitivity to these variables increases with tree size. We thus highlight that multiple edaphic factors influence different aspects of tropical forest structure, including different tree life stages, and species composition.

What factors influence colonization of lichens, liverworts, mosses and vascular plants on snags?

The dead standing trees i.e. snags are known as habitat for epiphytic and epixylic species including first of all lichens and bryophytes. The vascular plants are much rarer on this type of coarse woody debris (CWD). The eighty snags (CWD elements higher than 1.5 m) of Norway spruce Picea abies and beech Fagus sylvatica in the Karkonosze Mts. were examined for the presence of lichens, liverworts, mosses and vascular plants. The height of snags, their decomposition stage, cover of bark, diameter at breast height (DBH) as well as site conditions (elevation, slope and aspect, presence in forest community) were measured and noted. The percent cover of plants and lichens were estimated on each snag. Totally 99 taxa were recorded. There lichen species were dominant (44), followed by mosses (34), liverworts (13) and there were only 8 vascular plants. The total species richness varied from 1 to 22 taxa. The species composition growing on snags was subjected to canonical correspondence analysis and statistical analyses. They revealed that the species identity of snag is one of the most important factors influencing species composition. The number of species is positively correlated with DBH whereas decomposition stage, presence of bark, snag height are not significant factors. The species richness increases also with altitude what is connected with higher abundance of spruce snags. The occurrence of snags in this area is mainly associated with forest management practices in the past. Despite of some observed patterns in colonization of snags they are important habitat especially for lichens.

Relative importance of environmental factors and farming practices in shaping weed communities structure and composition in French vineyards

Understanding the relative importance of spatial, temporal variables, environmental conditions and management practices as filters for weed assemblages is essential to promote biodiversity in agrosystems. In this study, we used a unique data set covering 46 vineyard plots in France (Champagne, Beaujolais and Languedoc winegrowing areas) with 883 flora surveys performed between 2006 and 2012. The three objectives of the present study were: (1) to characterize weed communities composition and structure (richness and abundance) in vineyards from three traditional winegrowing areas in France; (2) to evaluate the relative importance of spatial, temporal variables, environmental conditions and management practices on weed species composition and structure; (3) to determine whether or not weed composition and structure are affected by the same factors. The results of the study revealed that season (including timing of management practices) was the most important filter for weed communities in vineyards, opposing in each plot a spring community and a summer-autumn community. Furthermore, spatial variations between regions (latitude), soil types (pH) and inter-annual variations (2006 to 2012) were also seen to have a strong effect on species turnover. Farming practices explained an overall low variation in composition of weed communities but some species showed a high and consistent fit to contrasting practices. For example, herbicide applications (mostly glyphosate) promoted some species such as Malva sylvestris and Sorghum halepense whereas tillage in inter-rows selected typical annual weeds such as Cerastium glomeratum and Galium aparine. Farming practices had a much higher influence on species richness and abundance with equal effect of both herbicides and soil tillage for controlling weed species richness and abundance in inter-rows, but stronger effects of herbicides were observed on species abundance in the rows. Tillage along the rows and a combination of mowing and tillage along the inter-rows were associated to the highest level of weed richness and abundance. Our study suggests that grapevine growers have a limited ability to influence species composition (mostly determined by abiotic factors) but their choice of management can modulate the level of weed richness and abundance. Our results will contribute to guide farmers towards more integrated management practices, ensuring both an optimal management of the spontaneous vegetation in vineyards and allowing this vegetation to provide various ecosystem services.

Factors affecting 13C enrichment of vegetation and soil in temperate grasslands in Inner Mongolia, China

Soil organic carbon (SOC) dynamics are central to understanding the effects of environmental change on the carbon cycle of ecosystems. Vegetation and soil stable carbon isotope composition (δ13C), especially the difference of δ13C between surface soils and source vegetation (Δδ13C), can provide useful information about the SOC dynamics. The variations and patterns of vegetation and soil δ13C and Δδ13C along climatic and edaphic gradients were analyzed to improve the understanding of SOC dynamics in temperate grassland ecosystems. Soil and plant samples were collected along climatic and edaphic gradients. Meteorological data were extracted from a regional climate database, which was spatially interpolated based on the records at 107 climatic stations located in Inner Mongolia. δ13C, carbon and nitrogen contents of soil and plant, soil pH, soil clay, silt, and sand contents were determined. Δδ13C and soil C:N were calculated. The integrative effects of these factors were further estimated using stepwise regression, redundancy analysis (RDA) and T value biplots. As expected, soil δ13C was positively related to vegetation δ13C, and higher than the vegetation δ13C. Vegetation and soil δ13C and Δδ13C were all related to growing season precipitation (GSP) and growing season temperature (GST). However, when climatic and edaphic factors were considered together, vegetation δ13C was positively related to GST and soil C:N, soil δ13C was positively related only to GST, and Δδ13C was negatively related only to soil C:N. Unlike previous research conducted at the species level which only included C3 species, GST, instead of precipitation, was the dominant controlling factor of vegetation δ13C. GST influences vegetation δ13C mainly through its effect on relative abundance of C4 plants. Soil C:N rather than climatic factors is the dominant controlling factor of SOC decomposition, and the effects of climatic factors on SOC decomposition are indirect and induced by their effects on soil C:N through influencing species composition and plant C:N. Measuring vegetation δ13C, soil δ13C, and △δ13C simultaneously is necessary to comprehensively understand how environmental changes influence ecosystem carbon cycles.