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1.
Forest edges affect many aspects of plant communities, causing changes in microclimate, species composition, and community structure. However, the direct role of edges in regulating forest regeneration is relatively unknown. The pattern of tree establishment across a forest-old field edge was experimentally examined to determine the response of three tree species to the edge gradient. We placed 100 1-m(2) plots in a 90 × 90 m grid that began 30 m inside the forest, extended across the edge, and ended at 60 m into the old field. Into each plot, we planted seeds of Acer rubrum, Acer saccharum, and Quercus palustris. Emergence increased with distance into the field for both A. saccharum and Q. palustris. Emergence for A. rubrum increased from forest to field, reaching a maximum near 20 m into the field, and then declined with further distance. Nearly all A. rubrum seedlings died shortly after emergence. Survival of A. saccharum increased with distance into the old field, while survivorship of Q. palustris did not respond to the edge gradient. Establishment probabilities increased with distance into the old field for both A. saccharum and Q. palustris. Growth of Q. palustris and allocation patterns of A. saccharum also varied across the edge gradient. These results suggest that edges have complex, species-specific effects on tree establishment and growth that can influence the spatial pattern and species composition of regenerating forests.  相似文献   

2.
To determine the influence of the proximity of a forest edge on seed bank composition and diversity, we performed a seed bank sampling at ancient deciduous forests bordering intensive arable fields. Also vegetation patterns were taken into account. We hypothised that forest edges may facilitate the entrance of diaspores of invasive species into the forest and the successive incorporation of these species in the forest seed bank. We noticed a substantial influence of the proximity of an edge on seed bank composition at as well the forested side of the edge as the field side. The forest edge zone was limited to 3 m into the forest and the field edge zone extended 3m into the field. The seed bank samples of field and forest edge are characterised by a higher species diversity and seed density and a higher similarity between seed bank and vegetation, compared to field or forest samples. The forest edges contains fewer pioneer species in comparison with the forest interior and more competitive species and species of edges and clearings compared with field and forest samples. The seed longevity index increases towards the forest interior. We can conclude from our data that the forest and edge seed bank are composed by both seeds from recent dispersal processes and local seed set and by seeds originating from past vegetation on the site. Near the edge, actual seed input seems of primal importance. Further towards the forest interior seed input decreases and long-living seeds of past vegetation become more important. Ancient forest edges thus act as a barrier for seeds of species of the surrounding arable field.  相似文献   

3.
The effects of forest edge on ant species richness and community composition were examined within an urbanized area of northeast Ohio. The ground-dwelling ant fauna was inventoried in three deciduous forest fragments that have resulted from human disturbance. We surveyed ants via leaf-litter extraction along 150 m transects positioned perpendicular to the forest edge. We collected 4,670 individuals from 14 genera and 29 species. Samples closest to the forest edge contained more species and accumulated species at a higher rate than did samples located in the forest interior. Our rarefied and expected richness estimates revealed a decline of species richness from edge to forest interior. The higher ant richness at the forest edge was due mostly to the presence of species characteristic of the neighboring open habitats. Although most of the typical forest ant species were represented equally at the edge and at the forest interior, a few responded to the presence of edges with changes in their relative abundance and frequency of occurrence. Forest edges had a higher proportion of opportunistic species and a lower proportion of cryptic ants, whereas interior locations exhibited a more even distribution among ant functional groups. In addition, we documented a community composition shift between the edge and the forest interior. Consistent with previous findings, we suggest that the edge effects are most pronounced within 25 m of the forest edge, which may have implications for the overall conservation of forest-dwelling fauna.  相似文献   

4.
In this paper, we tested four hypotheses relative to edge and shape effects on ant communities: (i) forest edges have lower species richness than the remnant core; (ii) species richness increases with distance from the edge; (iii) irregularly shaped remnants have lower species richness than more regular remnants; (iv) there is a higher similarity of species composition between edge and core in irregular than in regular remnants. We sampled litter ant communities on the edge and core of ten remnants, in Viçosa, Minas Gerais, Brazil. Species richness was larger at the forest core than at the edges, although did not increase with distance from the edge. Species richness did not vary with shape complexity. The similarity of species composition between edge and core showed a decreasing trend with remnant area, and did not vary with shape complexity. The observed differences of species richness between forest core and edge may be due to higher harshness of edges, caused by environmental changes. The absence of relationship between species richness and distance from the edge might indicate the range of edge effects, which would be smaller than the smallest distance of core sampled. Therefore, edges would affect litter-dwelling ant species richness in a distance smaller than 50 m. The observation of species composition allowed us to notice an effect of fragmentation that would not be noticed if we were considering only species richness. Edge may serve as step to generalist species, which may use it to colonise forest remnants. Furthermore, small remnants are more colonisation-prone by such species, and have a more homogeneous species composition than large remnants.  相似文献   

5.
We report on soil leaching of dissolved inorganic nitrogen (DIN) along transects across exposed edges of four coniferous and four deciduous forest stands. In a 64-m edge zone, DIN leaching below the main rooting zone was enhanced relative to the interior (at 128 m from the edge) by 21 and 14 kg N ha−1 y−1 in the coniferous and deciduous forest stands, respectively. However, the patterns of DIN leaching did not univocally reflect those of DIN throughfall deposition. DIN leaching in the first 20 m of the edges was lower than at 32–64 m from the edge (17 vs. 36 kg N ha−1 y−1 and 15 vs. 24 kg N ha−1 y−1 in the coniferous and deciduous forests, respectively). Nitrogen stocks in the mineral topsoil (0–30 cm) were, on average, 943 kg N ha−1 higher at the outer edges than in the interior, indicating that N retention in the soil is probably one of the processes involved in the relatively low DIN leaching in the outer edges. We suggest that a complex of edge effects on biogeochemical processes occurs at the forest edges as a result of the interaction between microclimate, tree dynamics (growth and litterfall), and atmospheric deposition of N and base cations.  相似文献   

6.
Large parts of the everwet tropics have been burned, leaving many unburned–burned forest edges. Here we studied a Bornean forest edge to determine: (1) how unburned and burned forest differ in vegetation structure, diversity, composition and plant functional traits 7 yr after fire, and (2) if these variables showed significant edge effects. Environmental and inventory data from 120 plots (0.01 ha each), covering both sides of a ~1.3 km forest boundary were sampled. Differences in vegetation structure, diversity, composition and plant functional traits were analyzed in relation to disturbance type (Mann–Whitney tests) and edge distance (partial correlation analysis that controlled for confounding effects of elevation, slope and fire intensity). Seven years after fire, burned forest differed significantly from unburned forest in most measured variables while few significant edge effects were detected, i.e., there existed a sharp delimitation between the two forest types. The regeneration of the burned forest depended almost entirely on in situ recruitment with little input of late successional species from the neighboring old growth forest. On the other hand, old growth forest showed few signs of edge degradation. A possible explanation for these results might be related to the absence of a mast fruiting event during these first 7 yr of forest recovery, resulting in low levels of late successional species seed input into the burned forest, combined with the quick development of a closed canopy in the burned forest by early successional species that shielded the unburned forest from adverse edge effects.  相似文献   

7.
Summary Roots of two year old willow and poplar planted as cuttings in copper and iron mine tailings were stained intact and examined microscopically for mycorrhizal development. Incidence of mycorrhizae was related to tree vigor and to chemical and physical properties of the tailings. Results showed that no mycorrhizal development occurred on roots of these tree species in the copper tailings; inoculations with natural forest soil extract failed to initiate this symbiosis. Tops and roots of the willow and poplar were stunted and survival was poor. Roots in the iron mine tailings developed extensive ectomycorrhizae and trees showed good growth. Presence of mycorrhizae was confirmed and external morphology examined with the scanning electron microscope. Aseptic jack pine and naturally mycorrhizal white pine roots were used in microscopic comparisons with the hardwoods. re]19760220  相似文献   

8.
Taylor DL  Bruns TD 《Molecular ecology》1999,8(11):1837-1850
We have investigated colonization strategies by comparing the abundance and frequency of ectomycorrhizal fungal species on roots in a mature Pinus muricata forest with those present as resistant propagules colonizing potted seedlings grown in the same soil samples. Thirty-seven fungal species were distinguished by internal transcribed spacer (ITS) restriction fragment length polymorphisms (RFLPs); most were identified to species level by sporocarp RFLP matches or to genus/family level by using sequence databases for the mitochondrial and nuclear large-subunit rRNA genes. The below-ground fungal community found in the mature forest contrasted markedly with the resistant propagule community, as only four species were found in both communities. The dominant species in the mature forest were members of the Russulaceae, Thelephorales and Amanitaceae. In contrast, the resistant propagule community was dominated by Rhizopogon species and by species of the Ascomycota. Only one species, Tomentella sublilacina (Thelephorales), was common in both communities. The spatial distribution of mycorrhizae on mature roots and propagules in the soil differed among the dominant species. For example, T. sublilacina mycorrhizae exhibited a unique bias toward the organic horizons, Russula brevipes mycorrhizae were denser and more clumped than those of other species and Cenococcum propagules were localized, whereas R. subcaerulescens propagules were evenly distributed. We suggest that species differences in resource preferences and colonization strategies, such as those documented here, contribute to the maintenance of species richness in the ectomycorrhizal community.  相似文献   

9.
Åke Berg  Tomas Pärt 《Ecography》1994,17(2):147-152
The aim with this study was to investigate whether abundance of farmland birds on fields at forest edges were associated with (I) type of field (young set-aside vs arable fields), (n) the length and structure of the field-forest edge zone, and/or (m) with residual habitats such as habitat islands, ditches, roads etc Twenty-eight farmland bird species (all nesting and/or foraging on open fields) were censused during the breeding season on 48 plots (open fields with adjoining forest edges) in the central parts of Sweden, covering a total area of 595 ha Skylark Alauda arvensis , linnet Carduelis cannabina , whitethroat Sylvia communis and whinchat Saxicola rubetra were found in significantly higher numbers in set-aside-plots than cereal ones However, the most important factor explaining variation in the abundance of most species was the structure of the field-forest ecotone, with the length of shrubby southern deciduous forest edges being the most important factor in 7 of the species Mixed forest edges seemed to be of some importance for the abundance of 3 species, while associations between abundance and length of the other deciduous and coniferous field-forest ecotones only were significant for one species each Skylarks, white wagtails Motaalla alba and whinchats were positively associated to ditches and yellowhammers Emberiza citrinella and linnets were significantly associated to habitat islands The observed preferences for set-asides and shrubby field forest edges are suggested to be results of reduced predation risk and increased food abundance  相似文献   

10.
The study was conducted in a hydroponics set-up to determine the suitability of zinc (Zn) and copper (Cu) contaminated wastewater as a growth medium for edible crops; to identify accumulation of Zn and Cu in different parts of the plants and to understand their effects on plant growth. Silver beet was found to produce adequate yields in the Zn (1.7 mg/L and 2.0mg/L) and Cu (0.35 mg/L and 1.1mg/L) spiked medium but not in the secondary treated domestic effluent. The plants grown in secondary treated effluent showed stunted growth and accumulated Zn and Cu to a high level in their shoots. In all other mediums Zn and Cu accumulated more in the roots. The stunted growth of silver beet in secondary treated wastewater and uptake of Zn in particular was considered to be due to the deficiency of nitrogen and other plant nutrients rather than the effect of heavy metals. The study also revealed that if there was adequate amount of macronutrients available for growth, silver beet could be grown in domestic effluent without the risk of Zn or Cu contamination to the undesired level through hydroponics.  相似文献   

11.
Abstract The distributions of lizards across habitat edges delimiting open‐forest and regenerating sand‐mined areas as a function of distance from the edge were studied at Tomago, New South Wales, Australia. Pitfall‐trapping was used to survey lizards across the northern edges of four forest fragments, to determine if lizards displayed characteristic responses across the edge, and whether these could be explained by the different habitat conditions. At each site, 11 equally spaced drift fences (each parallel to the edge) were arranged in a transect running perpendicular to the edge, and stretching 50 m into each habitat type. Captures of Amphibolurus muricatus (Agamidae) decreased substantially across the edge from the mine‐path to the forest so that it was identified as a mine‐path specialist lizard species. Captures of two skink species decreased across the mine‐path before reaching the edge, and were not caught (Ctenotus taeniolatus) or were seldom caught (Ctenotus robustus) in the forest, so they were identified as mine‐path specialist, edge avoiding, lizard species. Captures of Lampropholis delicata (Scincidae) increased across edges into the forest, consistent with the expectation for a forest specialist. Regression analyses indicated the responses to edges of three lizard species (A. muricatus, C. robustus and C. taeniolatus) were negatively correlated with canopy cover (probably due to its influence on temperature, as captures of A. muricatus and C. robustus were also correlated positively with mean daily temperature). In addition, the response of C. robustus correlated negatively with a vegetation factor (dense, even vegetation in the first 50 cm from ground level). The response of L. delicata correlated positively with understorey height. We have identified edge response strategies for four species of lizards across edges delimiting temperate open‐forest and mined areas, and identified habitat and microclimate variables that may have driven these responses.  相似文献   

12.
? Premise of the study: Leaf venation is linked to physiological performance, playing a critical role in ecosystem function. Despite the importance of leaf venation, associated bundle sheath extensions (BSEs) remain largely unstudied. Here, we quantify plasticity in the spacing of BSEs over irradiance and precipitation gradients. Because physiological function(s) of BSEs remain uncertain, we additionally explored a link between BSEs and water use efficiency (WUE). ? Methods: We sampled leaves of heterobaric trees along intracrown irradiance gradients in natural environments and growth chambers and correlated BSE spacing to incident irradiance. Additionally, we sampled leaves along a precipitation gradient and correlated BSE spacing to precipitation and bulk δ(13)C, a proxy for intrinsic WUE. BSE spacing was quantified using a novel semiautomatic method on fresh leaf tissue. ? Key results: With increased irradiance or decreased precipitation, Liquidambar styraciflua decreased BSE spacing, while Acer saccharum showed little variation in BSE spacing. Two additional species, Quercus robur and Platanus occidentalis, decreased BSE spacing with increased irradiance in growth chambers. BSE spacing correlated with bulk δ(13)C, a proxy for WUE in L. styraciflua, Q. robur, and P. occidentalis leaves but not in leaves of A. saccharum. ? Conclusions: We demonstrated that BSE spacing is plastic with respect to irradiance or precipitation and independent from veins, indicating BSE involvement in leaf adaptation to a microenvironment. Plasticity in BSE spacing was correlated with WUE only in some species, not supporting a function in water relations. We discuss a possible link between BSE plasticity and life history, particularly canopy position.  相似文献   

13.
This article examines the influence of nutritional status on the emergence of deciduous dentition in a cross-sectional sample of 510 rural Rajput children from the Jubbal and Kotkhai Tehsils, Shimla District, Himachal Pradesh, India. The nutritional status of each child was evaluated using Z-scores of height/supine length-for-age (HAZ), weight-for-age (WAZ), and weight-for-height (WHZ). The effects of sex and side on deciduous dental emergence were not statistically significant. Partial correlation indicates that the number of emerged teeth (T) was more strongly correlated with height than with other anthropometric variables. In most age groups, the stunted boys and girls (HAZ <-2) had fewer emerged teeth than nonstunted age peers (HAZ >-2). The mean T in underweight children was also less than that of the normal children, with a few exceptions. The stunted children have a significantly greater likelihood of delayed emergence of deciduous dentition. Measures of linear growth status are more closely related to dental development than measures of growth in mass. The findings indicate that even moderate undernutrition can delay deciduous tooth emergence.  相似文献   

14.
BACKGROUND AND AIMS: Acer saccharum and Fagus grandifolia are among the most dominant late-successional tree species in North America. The influence of sapling growth responses to canopy gaps on the co-dominance of the two species in an old-growth forest in southern Quebec, Canada was examined. Two predictions were evaluated: (a) F. grandifolia is more shade tolerant than A. saccharum due to greater sapling leaf area and net production per sapling in closed-canopy conditions; and (b) the height growth rate of A. saccharum in canopy gaps is greater than that of F. grandifolia due to increased net production per sapling. METHODS: Sapling crown allometry, net production and height growth rates were compared between and within the two species in closed canopy vs. canopy gaps. Standardized major axis regression was used to analyse differences in crown allometry. KEY RESULTS: F. grandifolia had greater crown projection, sapling leaf area and net production rate per sapling than A. saccharum in closed-canopy conditions. In response to canopy gaps, net production per sapling increased to the same degree in both species. The net production per sapling of F. grandifolia thus was much greater than that of A. saccharum in both canopy gap and closed-canopy conditions. The height growth rate of both species increased in canopy gaps, but the degree of increase was greater in F. grandifolia than in A. saccharum. CONCLUSIONS: F. grandifolia regenerated more successfully than A. saccharum in both closed-canopy conditions and canopy gaps, which indicates that the co-dominance of the two species cannot be maintained simply by interspecific differences in shade tolerance and growth in gaps. Previous research showed that although Fagus and Acer shared dominance at this site, their relative dominance shifted with edaphic conditions. This suggests that the widespread co-dominance of the two species in eastern North American forests is maintained by the joint influence of canopy disturbance and species-specific responses to the heterogeneity of moisture and fertility regimes within forested landscapes.  相似文献   

15.

We examined differences in the responses of deciduous and evergreen broadleaved trees to fluvial disturbance and light environment near a river-facing forest edge in order to identify the factors limiting the distribution of deciduous trees, which are important components of warm-temperate mountainous riparian forests. Deciduous trees tended to be distributed on lower terraces of less than 2-m relative elevation from the water level, which corresponded with sites suffering from strong bank erosion due to high flood frequency. On the other hand, evergreen trees showed an opposite trend of distribution, indicating that high flood frequency associated with strong erosion-dominated soil disturbances might be a constraint for their establishment and/or survival. Furthermore, crowns of deciduous trees tended to be in the canopy layer at the forest edge, with fewer individuals observed beneath the canopy of evergreen trees, even at the forest edge. In contrast, evergreen trees were concentrated in the understory of the forest interior. These observations suggested that the light environment is the predominant factor affecting the establishment and survival of deciduous trees in warm-temperate mountainous riparian forests; however, the river-facing forest edge beneath the evergreen canopy is not a suitable habitat for deciduous trees. We concluded that erosion-dominated soil disturbance on lower terraces provides suitable habitats for deciduous trees by facilitating their reaching the canopy layer by limiting the establishment and/or survival of evergreen trees.

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16.
The spatial distribution of patchy insect populations is partly caused by behavioral patterns of insect movement that are influenced by habitat quality, isolation, and the permeability of the surrounding matrix. We recorded insect movements, abundance, and edge behaviors in two species of butterflies, the great-spangled fritillary (Speyeria cybele F., Lepidoptera: Nymphalidae) and the pearl crescent (Phyciodes tharos Drury, Lepidoptera: Nymphalidae), inhabiting remnant prairies surrounded by a forest matrix in south-central Ohio. We also determined the number of forest matrix types present and recorded the permeability of the different types to butterfly movement. The great-spangled fritillary exhibited a relatively high number of interpatch movements, a higher abundance at patch edges, and a propensity to cross the prairie-forest edges, and the forest matrix had a high permeability to butterfly movement. The pearl crescent, in contrast, rarely crossed edge boundaries, moved infrequently among patches, and was more abundant within the patch interior and in patches with high host-plant and flower densities. There were three structurally different forest matrix types separating habitat patches, which in previous studies would have been classified as a single deciduous forest matrix. Butterfly movement and edge behaviors mechanistically interact with patch quality, isolation, and the matrix permeability to determine the spatial structure of these populations in fragmented habitats.  相似文献   

17.
Question: How do habitat edges and trampling affect mesic (Myrtillus type) understorey vegetation in fragmented urban forests, and what are the relative strengths and spatial extent of these effects? Location: The city of Helsinki, southern Finland. Methods: Vegetation sample plots were placed at different distances from the forest edge. At each distance we selected plots on, next to and away from paths of different levels of wear, and the covers and frequencies of plant species were sampled. We used generalized linear mixed models and ordination techniques to test our hypotheses. Results: The effect of the edge penetrated up to 50 m into the forest interior. Only light effects of trampling were found in seemingly untrampled areas, in addition to the direct effects of trampling on the paths. Both trampling and edge effects changed the forest understorey species composition. Trampling changed plant species composition locally on paths, and provided opportunities for new species to establish in previously unbroken forest vegetation. Urban forest edges were characterised by species better adapted to sunny, warm and dry conditions. These species, such as grasses, replaced more sensitive forest species, such as dwarf shrubs and mosses. We observed a large number of light demanding deciduous trees at the edges, which may be one of the factors increasing soil fertility and consequently promoting the high abundance of fast growing species, such as grasses and herbs related to more fertile site types. Conclusions: We recommend that urban forest fragments left within urban development should be at least 2–3 ha in size and that the shape of the patch and the number of potential recreational users should be taken into account when preserving true forest understorey vegetation from the effects of edges and trampling.  相似文献   

18.
Boreal forest trees are highly dependent on root-colonizing mycorrhizal fungi. Since the maintenance of mycorrhizal symbiosis implies a significant carbon cost for the host plant, the loss of photosynthetic leaf area due to herbivory is expected to reduce the host investment in mycorrhizae. We tested this hypothesis in a common garden experiment by exposing ectomycorrhizal white birch (Betula pubescens Ehrh.) seedlings to simulated insect defoliation of 50 or 100% intensity during either the previous or the current summer or repeatedly during both seasons before harvest. The shoot and root growth of the seedlings were distinctly reduced by both 100% defoliation and repeated 50% defoliation, and they were more strongly affected by previous-year than current-year defoliation. The root to shoot ratio significantly decreased after 100% defoliation, indicating reduced proportional allocation to the roots. Ergosterol concentration (i.e. fungal biomass) in the fine roots decreased by 100% defoliation conducted either in the year of harvest or in both years. No such decrease occurred following the 100% defoliation conducted in the previous year, indicating the importance of current photosynthates for fungal symbionts. The trend was similar in the colonization percentage of thick-mantled mycorrhizae in the roots, the most marked decline occurring in the repeatedly defoliated seedlings. The present results thus support the prediction that the plant investment in ectomycorrhizae may decline as a response to foliage loss. Moreover, the colonization percentage of thick-mantled mycorrhizae correlated positively with the ratio of leaf to heterotrophic plant biomass in the defoliated birch seedlings, but not in the control ones. This tends to indicate a stronger carbon limitation of ectomycorrhizal colonization in defoliated seedlings.  相似文献   

19.
Abstract. This study deals with stand dynamics over a 6‐yr period in a conifer/broad‐leaved mixed forest in Hokkaido, northern Japan. The annual rates of gap formation and recovery were 81.3 m2/ha and 66.7 m2/ha, respectively and turnover time of the canopy was 125 yr. The recruitment processes of the component species in this cool‐temperate forest were governed by different canopy types: gap, canopy edge and closed canopy. Magnolia obovata regenerated in canopy edges, and Acer mono and Prunus ssiori regenerated in canopy edges and gaps. The results suggested that the mosaic structure made up of closed canopy, canopy edge and gap was related to various regeneration niches. Abies sachalinensis had high mortality rates, initiating gap expansion. The transition probabilities from closed canopy or canopy edge to gap for deciduous broad‐leaved trees were lower than for A. sachalinensis, which implies that the difference in degeneration patterns of conifer and broad‐leaved canopies contributes to the heterogeneity of spatial structure in the mixed forests. Spatial dynamics were determined by a combination of gap expansion by A. sachalinensis (neighbour‐dependent disturbance) and gap formation by deciduous broad‐leaved trees (random disturbance).  相似文献   

20.
Edge effects are a widespread and ubiquitous ecological phenomenon, yet they remain poorly studied across edges between restored and natural forests. To address this lack of knowledge, we studied vertebrate communities across edges between 3‐year old restored mine‐pits and adjacent unmined forest in the jarrah (Eucalyptus marginata) forest of south‐western Australia. We found that mammal communities showed no edge response but reptile communities did. Overall reptile abundance and Morethia obscura abundance were higher in unmined forest along edges, Egernia napoleonis abundance was lower in unmined forest along edges, while Pogona minor abundance was lower in restored mine‐pits along edges. Predictive models were unable to predict species edge responses, due to the lack of knowledge of the ecology of jarrah forest reptiles, but proved useful in identifying potential ecological mechanisms behind observed edge responses and suggested that potential mechanisms were likely different for each species. Our study is the first to show edge responses in both habitats forming the edge between restored and natural forests, emphasizing the importance of studying both habitats forming the edge. Our results also suggest that, despite being poorly studied, edge responses are common across edges between restored and natural forest and result from a variety of ecological mechanisms. An increased understanding of the ecological mechanisms driving edge responses across edges between restored and natural forests will improve our ability to integrate restored areas into cross‐landscape management and, ultimately, improve our ability to manage landscapes for biodiversity conservation.  相似文献   

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