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1.
Trampling responses of an Atlantic heathland dominated by furzes were experimentally determined. They concerned two levels of biological systems: the vegetal community level (community scale) and the species level (intracommunity scale). Two trampling experiments were conducted: the first one was carried out in summer and the second one in winter. Heathland was trampled over 4 months, at differents intensities: 10, 30 and 90 persons a day. Whether trampling was conducted in the summer or in the winter, immediate responses of heathland (community scale) were similar: resistance of this vegetal community did not vary with the trampling season. Responses also showed that there is no linear relationship between vegetation degradation and trampling intensity. Deferred vegetation responses were similar, but within the community heathland (intracommunity scale) responses of a taxonomic group can depend on the trampling season. For example, resilience of furzes trampled in winter was greater than resilience of furzes trampled in summer. All these results should be considered in order to establish management orientations of trampled heathlands.  相似文献   

2.
The present study experimentally determined the short-term effect of different trampling intensities on the phytal habitat and associated meiofauna, and assessed the recovery of these communities on a coral reef. The experiment was conducted within the protected area on the reef of Porto de Galinhas Beach, northeastern Brazil. Within three areas, 30 × 30 cm2 plots were subjected to different experimental trampling intensities: 0 (control), 32 (low intensity) and 79 (high intensity) footsteps applied during 3 consecutive days. Samples were taken before trampling started and then 1 day and 1, 2 and 3 months after the end of trampling. Multivariate and univariate analyses were used to test for changes in the phytal substrate, the densities of the main meiofaunal major taxa, and the diversity, comparing the trampling intensities and the time periods. The immediate impact of trampling negatively affected the phytal substrate, causing large reductions in sediment content, total substrate weight, and algal turf height. Trampling also drastically decreased the density of the associated meiofauna and modified the community structure. The major meiofauna groups showed different patterns of recovery during the first and second months. However, 3 months after trampling ended, no impact was found for densities of total meiofauna and for most major taxa, and no differences were observed in the community structure among all trampling intensities. Finally, the results for trampling susceptibility and resilience allowed us to extend the discussion to management strategies for the use of reef areas for recreation.  相似文献   

3.
We investigated the macroinvertebrate community structure in Three‐Gorges Reservoir during a three‐year period after the reservoir became operational. Comparison with data of previous authors obtained before the damming showed that the benthic community changed drastically in the reservoir. Oligochaetes and chironomids dominate the present community. An apparent annual cycle in the benthic community (expressed as richness, density and community type) was found in the second year, lagging one year behind the annual cycle of transparency. After the second year, a Nais–Polypedilum community type, occurring in winter and spring with low inflow discharge and high transparency, was followed by a Limnodrilus community type that occurred in autumn and summer under contrasting conditions. Despite river regulation and damming, it appeared that macroinvertebrates in subtropical canyon‐shaped reservoirs remained influenced by floods. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

4.
Gething  Kieran J.  Ripley  Matthew C.  Mathers  Kate L.  Chadd  Richard P.  Wood  Paul J. 《Hydrobiologia》2020,847(20):4273-4284

Artificial drainage ditches are common features in lowland agricultural catchments that support a wide range of ecosystem services at the landscape scale. Current paradigms in river management suggest activities that increase habitat heterogeneity and complexity resulting in more diverse floral and faunal assemblages; however, it is not known if the same principles apply to artificial drainage ditch systems. We examined the effects of four artificial substrates, representing increasing habitat complexity and heterogeneity (bricks, gravel, netting and vegetation), on macroinvertebrate community structure within artificial drainage ditches. Each substrate type supported a distinct macroinvertebrate community highlighting the importance of habitat heterogeneity in maintaining macroinvertebrate assemblages. Each substrate type also displayed differing degrees of community heterogeneity, with gravel communities being most variable and artificial vegetation being the least. In addition, several macroinvertebrate diversity metrics increased along the gradient of artificial substrate complexity, although these differences were not statistically significant. We conclude that habitat management practices that increase habitat complexity are likely to enhance macroinvertebrate community heterogeneity within artificial drainage channels regardless of previous management activities.

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5.
The structural characteristics of the macroinvertebrate community can effectively reflect the health status of lake ecosystems and the quality of the lake ecological environment. It is therefore important to identify the limiting factors of macroinvertebrate community structure for the maintenance of lake ecosystem health. In this study, the community composition of macroinvertebrate assemblages and their relationships with environmental variables were investigated in 13 small lakes within Lianhuan Lake in northern China. A self‐organizing map and K‐means clustering analysis grouped the macroinvertebrate communities into five groups, and the indicator species reflected the environmental characteristics of each group. Principal component analysis indicated that the classification of the macroinvertebrate communities was affected by environmental variables. The Kruskal–Wallis test results showed that environmental variables (pH, total phosphorus, nitrate, water temperature, dissolved oxygen, conductivity, permanganate index, and ammonium) had a significant effect on the classification of the macroinvertebrate communities. Redundancy analysis showed that mollusks were significantly negatively correlated with pH and chlorophyll a, while annelids and aquatic insects were significantly positively correlated with chlorophyll a and dissolved oxygen. Spearman correlation analysis showed that the species richness and Shannon''s diversity of macroinvertebrates were significantly negatively correlated with total phosphorus, while the biomass of macroinvertebrates was significantly negatively correlated with pH. High alkalinity and lake eutrophication have a serious impact on the macroinvertebrate community. Human disturbances, such as industrial and agricultural runoff, negatively impact the ecological environment and affect macroinvertebrate community structure. Thus, macroinvertebrate community structure should be improved by enhancing the ecological environment and controlling environmental pollution at a watershed scale.  相似文献   

6.
Effects of human trampling and multispecies competition on the development of a tread community in the first year were examined by comparing changes in the relative abundance of three main component species of tread communities,Plantago asiatica, Eragrostis ferruginea andEleusine indica, between monoculture and mixed culture along a trampling gradient. At low trampling levels in mixed culture,Ambrosia artemisiifolia var.elatior andDigitaria adscendens, which are common pioneer species of secondary succession, predominated and suppressed the tread community species. Severe trampling reduced markedly the predominance of the pioneer species, but not that of the tread community species. The maximum cover of the three tread commiunty species was lower in mixed culture than in monoculture. The trampling levels supporting the maximum cover were higher in mixed culture than in monoculture. The differences in these levels between monoculture and mixed culture varied among the three:P. asiatica< Eragrostis ferruginea<Eleusine indica. These results suggest that (1) the pioneer species interfere with the establishment of tread community species under lower trampling intensity, (2) heavier trampling reduces the competitive ability of pioneer species, while it favors the establishment of tread community species, (3), there are competitive interactions among the tread community species under higher trampling intensity, and (4) the species more susceptible to multispecies competition and tolerant to trampling are established in more heavily trampled habitats.  相似文献   

7.
1. Macroinvertebrate densities and community composition were examined at three spatial scales after substratum disturbance; among reaches along a longitudinal gradient, within reaches and within plots. Reaches consisted of sandstone outcrops that were separated by approximately 2 km of highly mobile sandy silt substratum. 2. Substrata were disturbed by scraping sandstone plots (0.3 ± 0.3 m). Body-sized depressions created by Trichoptera in the sandstone were removed along with the upper 5 mm of sandstone, resulting in areas of newly exposed, smooth sandstone. 3. The spatial scale of examination determined whether patterns of macroinvertebrate distribution and densities were discernible. Initially there were no significant differences in community composition or total densities among reaches or among upstream/ downstream locations within reaches. Following substratum disturbance and 30 days recolonizarion, total macroinvertebrate densities did not differ significantly between undisturbed plots and disturbed plots. However, densities of Petrophilia (Pyralidae: Lepidoptera) differed along the longitudinal gradient and the Simuliidae had its highest density in the upstream reach. Significant differences were found in total macroinvertebrate densities between the upstream and the downstream halves of disturbed plots, with higher densities occurring in the downstream portions. 4. Recolonized plots had similar macroinvertebrate densities and community composition to undisturbed plots, suggesting that the stream community was highly resilient.  相似文献   

8.
The response of aquatic macroinvertebrate communities to flow permanence within limestone springs and headwater streams was examined across the English Peak District. At the regional scale, macroinvertebrate communities of perennial and intermittent springs displayed significant differences in the number of taxa, macroinvertebrate community abundance, diversity indices (Shannon and Simpson indices) and the Berger–Parker dominance index at intermediate discharge. However, no significant difference was recorded between intermittent and perennial sites at high discharge or when all sampling occasions were pooled. At the catchment scale, the number of taxa, community abundance and Bray–Curtis similarity coefficients within the River Lathkill differed significantly between intermittent springs and other habitats. At both the regional and catchment scale the macroinvertebrate communities of intermittent springs were characterised by a small number of taxa displaying life cycle adaptations to intermittent aquatic habitats, particularly Trichoptera.  相似文献   

9.
10.
Studies of exotic plant demography among habitats within its novel range may elucidate mechanisms of competitive dominance at local scales and invasive spread at landscape scales. We compared demographic trends of Anthriscus caucalis, an exotic herbaceous annual, across several plant communities within canyon grasslands of the Inland Pacific Northwest, USA. Greater observed survival and fecundity vital rates, as well as less spatial or temporal variability of vital rates, were considered indicators of greater plant community susceptibility to A. caucalis invasion. In addition, we investigated the role of differing habitat suitability across plant community types on potential landscape-level dispersal processes. To accomplish this objective, population matrix models were utilized to simulate stochastic transient (5 years) population growth rates (log λt) of A. caucalis under different net dispersal rate scenarios among the selected plant communities. We observed aboveground demography for 4 years within two bunchgrass community types and two shrub community types within a study area where livestock grazing occurred and within another study area that was not subjected to livestock grazing. Our results indicated that juvenile survival did not differ among communities, but the spatial variance of juvenile survival was significantly lower in shrub communities. Mean fecundity was significantly higher in high shrub (Celtis reticulata) communities compared to others, whereas spatial and temporal variances were significantly lower in high shrub communities compared to others. Within high shrub communities, total seed production was lower at the grazed site, which likely results from frequent livestock trampling within these refuge habitats. Under assumptions of no net seed dispersal, two of four bunchgrass sites maintained positive growth rates (log λt > 0; 95 % CI) whereas growth rates were positive in each shrub community. Notably, high shrub communities maintained positive growth rates under assumptions of 60 % net seed dispersal, while population growth rates in other communities declined with increasing net seed dispersal. In summary, our study suggests that high shrub communities are comparatively greater suitable habitat for A. caucalis growth and development and may act as source populations for invasive spread at a landscape scale.  相似文献   

11.
  1. Understanding changes in macroinvertebrate communities is important because they play a large role in stream ecosystem functioning, and they are an important food resource for fish. Beaver-induced changes to stream morphology could alter macroinvertebrate communities, which in turn could affect food webs and ecosystem function. However, studies investigating the effects of North American beaver activities on macroinvertebrates are rare in the inter-mountain west, an area with high potential for beaver-assisted restoration.
  2. The aim of this study was to quantify differences in the macroinvertebrate community between unaltered segments of streams and within beaver ponds in north-eastern Utah, U.S.A. We assessed macroinvertebrate species richness, biomass, density, functional feeding group composition, mobility group composition, and macroinvertebrate habitat characteristics to test the hypothesis that macroinvertebrate communities will differ among habitat types (undammed stream segments and beaver ponds) in beaver-occupied streams.
  3. Beaver pond communities significantly differed from lotic reach communities in many ways. Beaver ponds were less diverse with 25% fewer species. Although there was variability among streams, in general, beaver ponds had 75% fewer individuals and 90% lower total macroinvertebrate biomass compared to lotic reaches.
  4. Regarding functional feeding groups, beaver ponds contained more engulfers, while lotic reaches contained more scrapers, filterers, and gatherers. For mobility groups, beaver ponds had more sprawlers, while lotic reaches had more clingers. Swimmers were also more prevalent in lotic reaches, although this is probably due to the abundance of Baetis within lotic reaches. More beaver pond taxa were classified as lentic-dwelling insects, while more lotic reach taxa were categorised as preferring lotic habitats.
  5. The creation of ponds by beavers fundamentally altered the macroinvertebrate community in north-eastern Utah streams. Such changes to stream macroinvertebrate communities suggest that recolonisation of beavers across North America may be altering stream functioning and food webs. Our study highlights the need to further investigate the effects of beaver recolonisation on stream communities.
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12.
We examined the influence of riparian vegetation on macroinvertebrate community structure in streams of the Upper Thames River watershed in southwestern Ontario. Thirty-three μ-basins (129–1458 ha) were used to identify land cover variables that influenced stream macroinvertebrates. Micro-basins represented the entire drainage area of study streams and were similar in stream order (first, second) and land cover (agricultural or forest; no urban). We described the structure and composition of riparian vegetation and benthic macroinvertebrate communities at the outflow reach. The nature of the land cover was quantified for the stream network buffer (30 m) and the whole μ-basin. The objective of this study was to measure the magnitude and nature of the relationship between the riparian vegetation and benthic macroinvertebrate community at the outflow reach, stream network buffer, and whole μ-basin scales. Taxon richness (including total number of Ephemeroptera, Plecoptera, and Trichoptera taxa) and Simpson’s diversity of the macroinvertebrate community all increased with increased tree cover in the riparian zone at the outflow reach scale. Simpson’s equitability was lower with greater agricultural land cover in the stream network buffer. No relationship between the macroinvertebrate community and land cover was found at the whole μ-basin scale. Analysis of the influence of land cover on stream communities within a spatial hierarchy is important for understanding the interactions of stream ecosystems with their adjacent landscapes.  相似文献   

13.
The assessment of benthic invertebrate community condition is an integral component of freshwater biomonitoring and water quality determination. Several sampling devices have been developed to collect benthic macroinvertebrates, including qualitative, semi-quantitative, and quantitative methods. In this study, we compared several benthic macroinvertebrate metrics and community assemblage measures calculated from data obtained from two sampling methods, namely the Kick- and U-net sampling devices. We reasoned that if the two methods produced similar values for benthic metrics and community composition, then samples collected by these methods should be able to be combined to build larger data sets for use in regional bioassessment analyses. No statistical differences between Kick- and U-net methods were found among standard benthic macroinvertebrate metrics, except for Kick-nets collecting more Chironomidae. Invertebrate assemblages were very similar between collection methods, although slightly greater taxonomic richness was found in U-net samples. Bray–Curtis similarity was typically >75% between methods within a stream, while classification strength-sampling-method comparability, an approach for analyzing differences in similarity between groups, indicated invertebrate assemblage similarity between collection methods was virtually identical at approximately 100%. Since these two methods produce similar results, we conclude that benthic macroinvertebrate data collected by these methods can be combined for data analysis and bioassessments with the caveat that mesh size of the sample nets is similar. In addition, if the primary study objective is to assess macroinvertebrate biodiversity, then the U-net sampling device may be more appropriate, despite the slightly greater time needed to complete field sample collection, as it tended to collect a greater diversity of species.  相似文献   

14.
Worldwide declines in shorebird populations, driven largely by habitat loss and degradation, motivate environmental managers to preserve and restore the critical coastal habitats on which these birds depend. Effective habitat management requires an understanding of the factors that determine habitat use and value to shorebirds, extending from individuals to the entire community. While investigating the factors that influenced shorebird foraging distributions among neighboring intertidal sand flats, we built upon species-level understandings of individual-based, small-scale foraging decisions to develop more comprehensive guild- and community-level insights. We found that densities and community composition of foraging shorebirds varied substantially among elevations within some tidal flats and among five flats despite their proximity (all located within a 400-m stretch of natural, unmodified inlet shoreline). Non-dimensional multivariate analyses revealed that the changing composition of the shorebird community among flats and tidal elevations correlated significantly (ρs = 0.56) with the spatial structure of the benthic invertebrate prey community. Sediment grain-sizes affected shorebird community spatial patterns indirectly by influencing benthic macroinvertebrate community compositions. Furthermore, combining sediment and macroinvertebrate information produced a 27% increase in correlation (ρs = 0.71) with shorebird assemblage patterns over the correlation of the bird community with the macroinvertebrate community alone. Beyond its indirect effects acting through prey distributions, granulometry of the flats influenced shorebird foraging directly by modifying prey availability. Our study highlights the importance of habitat heterogeneity, showing that no single patch type was ideal for the entire shorebird community. Generally, shorebird density and diversity were greatest at lower elevations on flats when they became exposed; these areas are at risk from human intervention by inlet sand mining, construction of groins and jetties that divert sediments from flats, and installation of seawalls on inlet shorelines that induce erosion of flats.  相似文献   

15.
A study was undertaken within a sub-tidal Zostera marina seagrass bed (Devon, U.K.), with the aim of elucidating the relationship between seagrass structural complexity and the size and composition of the associated macroinvertebrate community. Samples of macroinvertebrates were recovered from three designated areas of shoot density. Various physical characteristics were measured for individual plants, and an a priori complexity index was determined relevant to the associated target organisms. Resulting data were analysed using linear regression and multivariate techniques. Significant relationships were found between shoot density and number of leaves/shoot, leaf length, stem length and algal epiphyte biomass. Neither the number of species nor abundance of macroinvertebrates was significantly related with the derived complexity index. Multivariate analysis indicated that macroinvertebrate communities from the three areas of shoot density were significantly different, the pattern of macroinvertebrate community composition being best explained by sea-grass biomass. Linear regression of seagrass biomass with macroinvertebrate number of species and abundance revealed significant positive relationships. Regression also indicated that there was no significant increase in complexity with increasing seagrass biomass. The results suggest that within a seagrass bed the size and composition of the associated macroinvertebrate community is not determined by the structural complexity of the plants, but by the amount of plant available. This finding indicates a simple species-area relationship, and arguably one brought about as a result of a sampling artefact. Thus, the current paradigm that structural complexity of seagrass is responsible for increased species diversity, can only be justifiably applied to comparisons between seagrass and other habitats, and not within a seagrass bed itself.  相似文献   

16.
Stream restorations that increase geomorphic stability can improve habitat quality, which should benefit selected species and local aquatic ecosystems. This assumption is often used to define primary restoration goals; yet, biological responses to restoration are rarely monitored or evaluated methodically. Macroinvertebrate communities were inventoried at 6 study reaches within 5 Catskill Mountain streams between 2002 and 2006 to characterize their responses to natural‐channel‐design (NCD) restoration. Although bank stability increased significantly at most restored reaches, analyses of variation showed that NCD restorations had no significant effect on 15 of 16 macroinvertebrate community metrics. Multidimensional scaling ordination indicated that communities from all reach types within a stream were much more similar to each other within any given year than they were in the same reaches across years or within any type of reach across streams. These findings indicate that source populations and watershed‐scale factors were more important to macroinvertebrate community characteristics than were changes in channel geomorphology associated with NCD restoration. Furthermore, the response of macroinvertebrates to restoration cannot always be used to infer the response of other stream biota to restoration. Thus, a broad perspective is needed to characterize and evaluate the full range of effects that restoration can have on stream ecosystems.  相似文献   

17.
The accumulation of sand and fine gravel (<5 mm diameter) on riverbeds can adversely affect benthic macroinvertebrates, which are good indicators of the ecological health of rivers. The possibility arises, therefore, that predictions of sedimentation could form a useful proxy for indicating the health of a river. The Sediment River Network Model (SedNet) constructs sediment budgets to predict the depth of bed material accumulation (BMA) in each link of a river network. This study tests whether the predicted BMA depth was associated with spatial differences in macroinvertebrate community structure, in the Upper Murrumbidgee River catchment of southeast Australia. There was a significant, albeit limited, correlation. Riffle sites with low BMA depth (0–0.01 m) had a significantly different macroinvertebrate community structure compared to sites with medium (0.01–0.3 m) or high (>0.3 m) BMA depth. At these sites, taxa sensitive to habitat were in greater abundance when BMA depth was low. Additionally, riffle sites with high predicted BMA depth had lower values for three macroinvertebrate community structure measures—AUSRIVAS observed-to-expected (OE) taxa ratio, Ephemeroptera abundance and Plecoptera abundance. There was no significant difference in macroinvertebrate community structure between sites with medium and high levels of BMA depth. Possible reasons for this result are: (1) there may have been few sites in the high and medium categories to provide sufficient statistical power to detect a significant difference; (2) spatial variation in BMA depth within SedNet river links; or (3) only a minimal amount of BMA is required to change community structure. To further define spatial variation in biological damage from BMA, data are required on the spatial scale of variations in BMA depth and damage to macroinvertebrate community structure.  相似文献   

18.
Climate warming may lead to changes in the trophic structure and diversity of shallow lakes as a combined effect of increased temperature and salinity and likely increased strength of trophic interactions. We investigated the potential effects of temperature, salinity and fish on the plant-associated macroinvertebrate community by introducing artificial plants in eight comparable shallow brackish lakes located in two climatic regions of contrasting temperature: cold-temperate and Mediterranean. In both regions, lakes covered a salinity gradient from freshwater to oligohaline waters. We undertook day and night-time sampling of macroinvertebrates associated with the artificial plants and fish and free-swimming macroinvertebrate predators within artificial plants and in pelagic areas. Our results showed marked differences in the trophic structure between cold and warm shallow lakes. Plant-associated macroinvertebrates and free-swimming macroinvertebrate predators were more abundant and the communities richer in species in the cold compared to the warm climate, most probably as a result of differences in fish predation pressure. Submerged plants in warm brackish lakes did not seem to counteract the effect of fish predation on macroinvertebrates to the same extent as in temperate freshwater lakes, since small fish were abundant and tended to aggregate within the macrophytes. The richness and abundance of most plant-associated macroinvertebrate taxa decreased with salinity. Despite the lower densities of plant-associated macroinvertebrates in the Mediterranean lakes, periphyton biomass was lower than in cold temperate systems, a fact that was mainly attributed to grazing and disturbance by fish. Our results suggest that, if the current process of warming entails higher chances of shallow lakes becoming warmer and more saline, climatic change may result in a decrease in macroinvertebrate species richness and abundance in shallow lakes.  相似文献   

19.
Regulating mobility by actively entering the drift under imminent predation risk is an avoidance strategy employed by aquatic macroinvertebrate species that is widely accepted within the scientific community. This response was most evident with respect to diurnal predators that feed in the water column, such as many salmonids. We investigated the role of the nocturnal benthivorous gudgeon [Gobio gobio (L.)] on the drift activity of two macroinvertebrate species known to display this behaviour: Baetis rhodani (PICTET) and Gammarus pulex (L.). Laboratory drift experiments using gudgeon kairomones were conducted with the results determining significant altered activity in the presence of gudgeon kairomones for both macroinvertebrate species. B. rhodani showed reduced drift activity in the kairomone treatment compared to the kairomone-free control, with a distinct nocturnal pattern being observed for both. G. pulex shifted from a similar day/night movement pattern to a nocturnal movement pattern with decreased activity during the day. Reduce activity during the day, whilst maintaining normal activity at night would not reduce the probability of encountering a nocturnal predator under natural conditions and therefore appears to not be a meaningful anti-predator response. To assess the relevance of these findings under natural conditions, we compared the experimental results with drift measurements from field observations. These show a significant reduction in drift activity for G. pulex and slight tendencies for reduced night-time drift for B. rhodani, under seasonal variations. We conclude that the behaviour in response to the physical contact or the hydrodynamic stimuli of nocturnal predators is the most likely explanation for the differences between the results from our laboratory experiment and the field observation. We further discuss that the observed migration patterns might have different species specific consequences for density stabilisation on a population level.  相似文献   

20.
We test the hypothesis that secondary succession in Tropical Montane Cloud Forest (TMCF) in Mexico is accompanied by an increase in the spatial structuring of litter resources, soil nutrient concentrations and the soil macroinvertebrate community at a within-plot scale (5–25 m). This increased spatial structuring is expected because secondary succession in these forests is associated with an increase in the diversity of trees that dominate the canopy. If each tree species generates a particular soil environment under its canopy, then under a diverse tree community, soil properties will be spatially very heterogeneous. Tree censuses and grid sampling were performed in four successional stages of a secondary chronosequence of TMCF. Variography was used to analyse spatial patterns in continuous variables such as nutrient concentrations, while Spatial Analysis by Distance Indices (SADIE) was applied to determine patchiness in the distribution of soil macroinvertebrate taxa. Secondary succession was found to be accompanied by the predicted increase in the spatial structuring of litter resources and the macroinvertebrate community at the within-plot scale. Spatial patterns in the macroinvertebrate community only became evident for all taxa in the oldest forest (100 years old). Patches with low Ca and Mg concentrations in early successional soils were associated with patches where pine litter was most abundant while those with low P concentrations in late successional stages were associated with patches where oak litter was most abundant. Results suggest that anthropogenic disturbance aboveground promotes a more homogeneous resource environment in the surface soil, which compared to older forests, sustains a less diverse and less spatially structured macroinvertebrate community.  相似文献   

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