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1.
Communities containing bolster (hard cushion) plants are widespread in alpine and subalpine treeless plant communities in Tasmania. Numerical analysis of species presence/absence data from 227 quadrats defined thirteen communities, the distributions of which proved strongly related to a southwest to northeast edaphic gradient and altitude. The high altitude communities and those on oligotrophic soils are most likely to be dominated by bolster species, whereas the eastern communities are more frequently dominated by shrubs or graminoids.Nomenclature follows Curtis (1963, 1967), Curtis & Morris (1975), Curtis & Stones (1978) and Willis (1970) except where authorities are given at first mention. Structural nomenclature follows Kirkpatrick (1983). 相似文献
2.
During a two year period 13498 individuals of 66 species of carabids were taken from 44 sites on peat and upland grasslands over an altitude range of 11-847 m in the north of England. The similarities between the carabid faunas of each site have been assessed using a modified form of the Sørensen's Index and the sites clustered according to their similarities. Five carabid communities on peat and three on mineral soils have been identified and the more abundant species have been used to characterise them. Peat Community I occurs on dry heath and is characterised by peat associated species such as Trichocellus cognatus and Bradycellus ruficollis together with widespread open habitat species such as Pterostichus madidus, Notiophilus aquaticus, Calathus melanocephalus and Nebria salina. Peat Community II is found on areas where dry heath and deep wet peat are adjacent and is characterised by the species already mentioned together with typical wet habitat species such as Pterostichus diligens, P. nigrita, Patrobus assimilis. Agonum fuliginosum. Peat Community III is found on blanket bog and is characterised by the wet habitat species in the absence of the species present on the dry heath. Peat Community IV found on the lowland oligotrophic mires is characterised by the small number of species present and the addition of Pterostichus niger and Agonum ericeti to the few wet habitat species present. Peat Community V, on the scarp slope of Dun Fell, consists of the wet habitat species of Peat Community III together with Pterostichus madidus. Nebria salina, Notiophilus aquaticus and Calathus melanocephalus. Grassland Community I, on the fell tops, is characterised by the presence of Nebria gyllenhali, Notiophilus germinyi and Patrobus assimitis. Grassland Community II and III are less clearly defined but Grassland Community II may be present on wetter sites than III and is characterised by the presence of Pterostichus nigrita, P. diligens and P. strennus together with Notiophilus biguttatus. N. aquaticus, Pterosfichus madidus and Patrobus afrorufus. Grassland Community III consists of the latter group of species together with Nebria salina, Calathus melanocephalus and Notiophilus aestuans. The number of grassland sites studied was small and there may be further communities on the upland grasslands. 相似文献
3.
Differences among lake morphologies often explain variation in characteristics of lentic ecosystems. Although beaver ponds
also vary in morphology, previous studies have not examined the effects of such variation on downstream ecosystems. This study
evaluated downstream effects of multiple beaver ponds in the Colorado Rocky Mountains during one low and one high-flow year.
Beaver pond morphology was described as the natural log transformed ratio of beaver dam height (which determines hydraulic
head) to pond surface area and related to pond spillover phytoplankton and characteristics of the ecosystem downstream (nutrient
concentrations, limiting nutrients, periphyton, benthic organic matter (BOM), and benthic invertebrate consumers). Nitrate
concentration increased systematically downstream of beaver ponds, but only in the low flow year when groundwater influences
predominated. Effects of beaver ponds on soluble reactive phosphorus concentration depended on pond morphology, increasing
downstream of small ponds with high dams, but only during the low-flow year. In situ experiments showed that neither beaver
activity nor pond morphology predicted periphyton-limiting nutrients downstream. Both periphyton biomass and BOM decreased
downstream of small ponds with high dams but pond morphology did not predict abundance of invertebrate grazers or detritus-feeding
consumers. While suspension feeding invertebrates increased downstream from small ponds with high dams, variation in chlorophyll
a from water spilling over beaver dams did not follow a similar pattern. We conclude that the effects of beaver ponds on downstream
nutrients, resources and consumers are rarely systematic, but instead depend on variation in pond morphology and on annual
hydrologic variation. 相似文献
4.
The conversion of mangrove forest to aquaculture ponds has been increasing in recent decades. One of major concerns of this habitat loss is the release of stored ‘blue’ carbon from mangrove soils to the atmosphere. In this study, we assessed carbon dioxide (CO2) efflux from soil in intensive shrimp ponds in Bali, Indonesia. We measured CO2 efflux from the floors and walls of shrimp ponds. Rates of CO2 efflux within shrimp ponds were 4.37 kg CO2 m−2 y−1 from the walls and 1.60 kg CO2 m−2 y−1 from the floors. Combining our findings with published data of aquaculture land use in Indonesia, we estimated that shrimp ponds in this region result in CO2 emissions to the atmosphere between 5.76 and 13.95 Tg y−1. The results indicate that conversion of mangrove forests to aquaculture ponds contributes to greenhouse gas emissions that are comparable to peat forest conversion to other land uses in Indonesia. Higher magnitudes of CO2 emission may be released to atmosphere where ponds are constructed in newly cleared mangrove forests. This study indicates the need for incentives that can meet the target of aquaculture industry without expanding the converted mangrove areas, which will lead to increased CO2 released to atmosphere. 相似文献
5.
S. Saarnio Jukka Alm Jouko Silvola Annalea Lohila Hannu Nykänen Pertti J. Martikainen 《Oecologia》1997,110(3):414-422
Temporal and spatial variation in CH4 emissions was studied at hummock, Eriophorum lawn, flark and Carex lawn microsites in an oligotrophic pine fen over the growing season using a static chamber method, and CH4 production and oxidation potentials in peat profiles from hummock and flark were determined in laboratory incubation experiments.
Emissions were lowest in the hummocks, and decreased with increasing hummock height, while in the lawns and flarks they increased
with increasing sedge cover. Statistical response functions with water table and peat temperature as independent variables
were calculated in order to reconstruct seasonal CH4 emissions by reference to the time series for peat temperature and water table specific to each microsite type. Mean CH4 emissions in the whole area in the snow-free period of 1993, weighted in terms of the proportions of the microsites, were
1.7 mol CH4 m–2. Potential CH4 production and oxidation rates were very low in the hummocks rising above the groundwater table, but were relatively similar
when expressed per dry weight of peat both in the hummocks and flarks below the water table. The CH4 production potential increased in autumn at both microsites and CH4 oxidation potential seemed to decrease. The decrease in temperature in autumn certainly reduced in situ decomposition processes,
possibly leaving unused substrates in the peat, which would explain the increase in CH4 production potential.
Received: 16 August 1996 / Accepted: 30 November 1996 相似文献
6.
Rachel L. Malison Mark S. Lorang Diane C. Whited Jack A. Stanford 《Freshwater Biology》2014,59(6):1229-1246
Our aim was to determine how beavers affect habitats and food resources for juvenile salmon in the Kwethluk River in western Alaska.
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7.
John Proctor K. Bartlem S.P. Carter D.A. Dare S.B. Jarvis D.R. Slingsby 《Plant Ecology & Diversity》2013,6(1):47-63
Summary The vegetation of two ultramafic sites (MK1 and MK2) at Meikle Kilrannoch are described. MK1 is dome shaped and has much weathering bedrock whilst MK2 is flatter, lacks weathering bedrock and has probably been entirely peat covered. Six vegetation Groups were recognized: I, high-level blanket bog; II and III, grass heath (with II more sedge-rich); IV, dwarf shrub heath; V and VI, debris (an open vegetation on stony skeletal soils). Vegetation maps were produced which had five mapping units: Group I, Groups II and IH combined, Group IV, Groups V and VI combined, and non-vegetated eroding peat. Three main soil types occur: peat, which underlies Group I; a complex of freely draining magnesian brown soils and imperfectly drained magnesian gleys which bear Groups II–IV; and skeletal soils, derived either from weathering bedrock (MK1 only) or ultramafic drift, which bear vegetation in Groups V or VI. The rare plants are commonest in, but not restricted to, debris vegetation on skeletal soils. The likely plant toxicity of soil magnesium at the sites is reaffirmed but it is suggested that the low plant cover in the debris is more likely to result from low nutrients or intensive frost action or both. Floristic differences between MK1 and MK2 are discussed and quantified for Lychnis alpina (which had 68000individuals on the former site and 46 on the latter) but the causes of the differences remain unexplained. 相似文献
8.
- Alpine rivers are, despite anthropogenic water flow regulation, still often highly dynamic ecosystems. Plant species occurring along these rivers are subject to ecological disturbance, mainly caused by seasonal flooding. Gypsophila repens typically grows at higher altitudes in the Alps, but also occurs at lower altitudes on gravel banks directly along the river and in heath forests at larger distances from the river. Populations on gravel banks are considered non‐permanent and it is assumed that new individuals originate from seed periodically washed down from higher altitudes. Populations in heath forests are, in contrast, permanent and not regularly provided with seeds from higher altitudes through flooding. If the genetic structure of this plant species is strongly affected by gene flow via seed dispersal, then higher levels of genetic diversity in populations but less differentiation among populations on gravel banks than in heath forests can be expected.
- In this study, we analysed genetic diversity within and differentiation among 15 populations of G. repens from gravel banks and heath forests along the alpine River Isar using amplified fragment length polymorphisms (AFLP).
- Genetic diversity was, as assumed, slightly higher in gravel bank than in heath forest populations, but genetic differentiation was, in contrast to our expectations, comparable among populations in both habitat types.
- Our study provides evidence for increased genetic diversity under conditions of higher ecological disturbance and increased seed dispersal on gravel banks. Similar levels of genetic differentiation among populations in both habitat types can be attributed to the species' long lifetime, a permanent soil seed bank and gene flow by pollinators among different habitats/locations.
9.
Marjan De Block Sofie Geenen Kurt Jordaens Thierry Backeljau Robby Stoks 《Genetica》2005,124(2):137-144
Several insect species seem to persist not only in permanent but also in temporary ponds where they face particularly harsh
conditions and frequent extinctions. Under such conditions, gene flow may prevent local adaptation to temporary ponds and
may promote phenotypic plasticity, or maintain apparent population persistence. The few empirical studies on insects suggest
the latter mechanism, but no studies so far quantified gene flow including both pond types. We investigated the effects of
pond type and temporal variation on population genetic differentiation and gene flow in the damselfly Lestes viridis in northern Belgium. We report a survey of two allozyme loci (Gpi, Pgm) with polyacrylamide gel electrophoresis in 14 populations from permanent and temporary ponds, and compared these results
with similar data from the same permanent populations one year before. The data suggested that neither pond-drying regime,
nor temporal variation have a substantial effect on population genetic structuring and did not provide evidence for stable
population differentiation in L. viridis in northern Belgium. Gene flow estimates were high within permanent and temporary ponds, and between pond types. Our data
are consistent with a source-sink metapopulation system where temporary ponds act as sinks in dry years, and are quickly recolonized
after local population extinction. This may create a pattern of apparent population persistence of this species in permanent
and temporary ponds without clear local adaptation. 相似文献
10.
Hydro-ecological analysis of the Biebrza mire (Poland) 总被引:2,自引:0,他引:2
Martin J. Wassen Aat Barendregt Adam Palczynski Jacques T. de Smidt Hans de Mars 《Wetlands Ecology and Management》1992,2(3):119-134
Vegetation composition and structure of 58 sites along gradients in the valley mire of Biebrza, Poland, are related to physical and chemical variables of groundwater and peat. The three most prominent hydrochemical processes in the valley are (a) dissolution of calcite; (b) dissolution of iron, manganese and aluminium; and (c) enrichment with nitrogen and potassium. Major factors determining these processes are vertical flow of the groundwater and river flooding.Within the rheophilous zone of the mire, calcium-richness of the shallow groundwater and base-saturation of the peat are caused by upward seepage of groundwater originating from adjacent higher grounds. This groundwater movement keeps the larger part of the mire saturated with calcium.Good correlations exist between hydrochemistry and vegetation patterns. Groundwater-fed sites support a characteristic rich fen vegetation (Caricetum limoso-diandrae) with a low biomass production. The flood-plain vegetation consists of highly-productive communities of Glycerietum maximae and Caricetum elatae. In a belt in the Upper Basin where neither flooding nor upward seepage occurs, succession, probably caused by intensified drainage, leads to a dwarf-shrub vegetation (Betuletum humilis; poor fen). 相似文献
11.
Mateusz Ciechanowski Weronika Kubic Aleksandra Rynkiewicz Adrian Zwolicki 《European Journal of Wildlife Research》2011,57(4):737-747
Beavers strongly modify their environment by not only building dams and creating ponds, which slow the water flow, but also
by selective cutting and removing of trees, which change the spatial structure of the forest. We aimed to test the hypothesis
that beaver activity promotes new foraging sites for insectivorous bats. The beaver’s influence can be especially significant
on aerial hawkers that prefer moderate structural clutter, like the Pipistrellus species (by creating new canopy gaps), and on water-surface foragers, like Myotis daubentonii (by creating ponds with smooth water surface). The study was conducted on small streams in forest areas of northern Poland,
which were colonized by the European beaver (Castor fiber). Bat activity was recorded with a Pettersson D-980 ultrasound detector on line transects. The number of bat passes was significantly
higher in the stream sections modified by beavers (flooded and subjected to intensive tree cutting) than in the unmodified
sections (for Pipistrellus nathusii, Pipistrellus pipistrellus, Pipistrellus pygmaeus, Nyctalus noctula, and all species lumped together). Contrary to our expectations, the activity of the Myotis species was significantly lower on the transect with the largest beaver ponds, possibly due to the blanket of duckweed (Lemnaceae),
which is known to produce clutter echoes, thereby reducing prey detection by echolocating M. daubentonii. 相似文献
12.
C. Ouellette S. C. Courtenay A. St-Hilaire A. D. Boghen 《Zeitschrift fur angewandte Ichthyologie》2006,22(1):15-24
Current methods used in harvesting peat in eastern Canada have raised concerns regarding potential impacts of escaped peat particles on aquatic ecosystems. A study was carried out in Mill Creek, an estuarine tributary of the Richibucto River in New Brunswick, where peat originating from a commercial operation has accumulated over several years. The sand shrimp Crangon septemspinosa Say (1818) was selected to determine potential environmental stress related to presence of peat in the sediment because of its close association with the substrate. Despite the introduction of sedimentation ponds at the harvesting site in 1994, peat particles continued to enter and accumulate in Mill Creek between 1997 and 1999. Increases in peat depth ranged from 6 to 31 cm and the volume of surficial (0–15 cm) sediments containing peat increased from 35% in 1997 to 44% in 1998 and 76% in 1999. Beach seine surveys carried out during July to September of 1996–1998 indicated that fewer sand shrimp occurred over substrates having higher (>66%) peat concentration than over sand or mud with lower (<33%) peat concentration. Length of sand shrimp did not vary consistently with peat concentration but sand shrimp caught over substrates containing medium (34–65%) peat concentration displayed lower condition [wet weight at total length (TL)] than conspecifics from substrates of both higher and lower peat concentration in all surveys. In a separate survey, peat was found in the stomachs of sand shrimp caught over substrates composed of high but not low peat concentration. We conclude that present mitigation measures at this site have been ineffective in preventing escape of peat moss into the estuarine environment and that the resulting peat deposition has reduced habitat quality for estuarine macrofauna as reflected in a reduction of the number and condition of sand shrimp. 相似文献
13.
Substrate instability is a common problem in many disturbed ecosystems. In the case of milled harvested peatlands, the pioneer moss Polytrichum strictum is commonly found; it is well adapted to tolerate the harsh microclimatic conditions and peat instability of these sites. A field experiment was used to determine the effectiveness of P. strictum against frost heaving, a major type of disturbance on bare peat. Wooden dowels and fir trees (Abies balsamea) placed in a P. strictum carpet experienced almost no frost heaving, whereas heaving was severe on bare peat. Reintroduced P. strictum fragments thinly spread on bare peat reduced but did not eliminate frost heaving. Straw mulch (a protective cover often required in peatland restoration) effectively reduced heaving in the fall, but was less effective in the spring because it had partially decomposed. The P. strictum carpet, P. strictum fragments, and straw mulch reduced frost heaving by reducing the number of freeze–thaw cycles, by slowing the rate of ground thaw in the spring, and by reducing the unfrozen water content of the peat during the spring thaw. Different species of Polytrichum mosses should be considered for the restoration or regeneration of disturbed ecosystems where soil stability is problematic. 相似文献
14.
ABSTRACTThe objective of this paper is to draw attention to a previously unrecognised habitat for Unio crassus Philipsson, 1788 (Bivalvia: Unionidae), namely beaver dam-and-pond complexes. The construction of beaver ponds will allow the colonisation of high energy streams by providing flow refuges during periods of high near-bed shear stress. The absence of freshwater mussels (Unionidae) in mountain streams may result from steep slopes, shear stress during floods, lack of food suspended in the water column (seston), and unfavourable conditions for the settlement and growth of juvenile mussels. Transportation of parasitic larvae on host fish is the main dispersal mechanism for the mussels. A possible constraint on the colonisation of beaver complexes by freshwater mussels is that beaver dams may hinder the upstream movement of their minnow hosts. In the surveyed beaver ponds, the first specimens of U. crassus were found in 2008. Single mussels were also found in subsequent years. It is uncertain whether the occurrence of U. crassus depends on the periodic support of the population from the main river, but the presence of beaver ponds is certain to have given it the opportunity of colonising new areas. 相似文献
15.
In the Netherlands peat was excavated for fuel until 1950. This gave rise to waterbodies (called turf ponds) which were then colonized by aquatic plants. Succession resulted in different aquatic plant communities and more terrestrialized stages such as floating fens. Nature conservation authorities started to excavate new turf ponds in 1990(ca. 2 ha y–1) with the aim to restore calcareous, mesotraphent ecosystems by totally setting back succession. A sequence of new species was revealed by mapping the aquatic vegetation from 1990 onwards.Chara spp. proved early colonizers, which was not expected because they have not been present in ditches and ponds in the area for the last 20 years. The denseChara vegetation prevents the resuspension of organic soil and contributes to keep the water column nutrient-poor and clear. ability of species such asStratiotes aloides to colonise the ponds from adjacent waterbodies is not possible because no open contact exists between a turf pond and a ditch. Management measures, such as re-introduction, have to be considered if the full-range of aquatic plant communities remains the goal. 相似文献
16.
Abstract. Little is known of the dynamics of the alpine cushion plant communities of Tasmania. The present study investigates the nature of the short (5 yr) and long (850 yr plus) term dynamics within one such community at Newdegate Pass, Tasmania. This involved observations of permanent plots, quadrat sampling of cushion heath in different stages of a secondary succesion and cuticular analysis of a core through the cushion peat. Data from the peat core showed the continued presence of the cushion heath community at this site for at least 850 yr, while the regeneration patterns indicated community composition was largely achieved by species accumulation rather than species replacement. Over a 5–yr period there was little or no change in total percentage cover yet a surprisingly high degree of interspecific competition for space in areas of complete plant cover. These observations best fit non equilibrium models of community succession and stability. 相似文献
17.
Peat bogs are regarded as extreme environments due to their low pH and low nutrient concentration, and thus hold a unique biota adapted to these particular conditions. The island of Tierra del Fuego encompasses the southernmost extensive peat bog area in the world, and is therefore particularly interesting from a biogeographical viewpoint. Within the same peat bog, different environment types can be identified: clear ponds, vegetated ponds and Sphagnum patches. In this study we compare the abundance, richness and species diversity of microinvertebrates (Copepoda, Cladocera and Rotifera) in these three types of environments from two peat bogs (Andorra and Rancho Hambre). Out of the 29 taxa recorded, 19 were common to both peat bogs, including four cladocerans endemic to Southern Patagonia and three rotifers endemic to Fuegian peat bogs. The rotifers were the dominant group in all environment types from Rancho Hambre, while in Andorra the Sphagnum moss was dominated by copepods, particularly harpacticoids. The results revealed that the environment type rather than peat bog was the key factor at explaining differences in species richness and diversity among microinvertebrate communities. This study highlights the importance of Sphagnum moss as a low diversity extreme environment which supports highly endemic species. 相似文献
18.
Jennifer C. Rowe Christopher A. Pearl Adam Duarte Brome McCreary Michael J. Adams 《The Journal of wildlife management》2024,88(1):e22496
Amphibians are among the most sensitive taxa to climate change, and species inhabiting arid and semiarid landscapes at the extremes of their range are especially vulnerable to drought. The Jack Creek, Oregon, USA, population of Oregon spotted frogs (Rana pretiosa) faces unique challenges because it occupies the highest elevation site in the species' extant range and one that has been transformed by loss of American beavers (Castor canadensis), which historically maintained open water. We evaluated the effects of drought mitigation (addition of excavated ponds) on relationships between local and regional water availability, inactive legacy beaver dams, and Oregon spotted frog population dynamics in the Jack Creek system. We conducted egg mass surveys and capture-mark-recapture sampling at a treatment reach with excavated ponds and 3 reference reaches over 13 years; surveys spanned a period before and after pond excavation at the treatment and 1 primary comparison reference reach. We analyzed data using a combination of robust design capture-mark-recapture estimators and generalized linear mixed models to characterize population dynamics. Adult Oregon spotted frog survival was approximately 19.5% higher at the treatment reach than the primary reference reach during the study period. Annual survival was most strongly associated with late summer vegetation greenness, a proxy for water availability, and males had higher survival than females. Among the 4 study reaches, the treatment reach consistently had higher late summer vegetation greenness, and the hydrology functioned more independently of regional precipitation patterns relative to the reference reaches; however, these dynamics were not linked to pond excavation. Breeding was concentrated in 2 legacy beaver ponds that were deepened by excavation during the study compared to an unexcavated beaver pond, 2 excavated ponds without legacy beaver dams, and 9 reference ponds. These results point to the benefit of enhancing existing beaver structures and indicate that management actions aimed at maintaining surface water for breeding in spring and saturated soils and ponded water for adults in late summer would benefit this unique population of Oregon spotted frogs in the face of drought. 相似文献
19.
1. The North American beaver has been studied as a model ecosystem engineer for many decades. Previous studies have documented physical, chemical and biological impacts attributed to beaver engineering in both aquatic and terrestrial environments. This study focused on the effects of ecosystem engineering by beavers on life histories of a common mayfly and on the potential consequences for mayfly populations. 2. We studied 18 montane beaver ponds of varying size and shape in western Colorado near the Rocky Mountain Biological Laboratory. Our goal was to test whether variation in beaver pond morphology (pond size and shape) explains downstream changes in stream temperature, mayfly size and timing of emergence. 3. Downstream water temperatures varied predictably with pond morphology, being colder downstream of high‐head dams and warmer downstream of low‐head dams. Pond morphology was also a significant predictor of variation in the size of mature female Baetis bicaudatus (the most abundant mayfly), with larger females emerging downstream of high‐head dams and smaller females downstream of low‐head dams. The size of male B. bicaudatus was not significantly related to pond morphology or stream temperature. There was no relationship between pond morphology and variation in the timing of emergence of Baetis (males or females) between upstream and downstream reaches. 4. Our results have implications for the effects of beaver ponds on Baetis individual fitness because large Baetis females are more fecund. Therefore, predictable female size variation associated with beaver pond morphology makes it possible to model the effects of beaver activity on local contributions of Baetis to the regional pool of reproductive adults at the catchment scale. Additionally, predictable changes in the size of emerging mayflies may have important consequences for the magnitude of aquatic to terrestrial resource subsidies in beaver‐modified systems. 相似文献
20.
Sanna R. Piilo Minna M. Väliranta Matt J. Amesbury Marco A. Aquino-López Dan J. Charman Angela Gallego-Sala Michelle Garneau Natalia Koroleva Mai Kärppä Anna M. Laine A. Britta K. Sannel Eeva-Stiina Tuittila Hui Zhang 《Global Change Biology》2023,29(6):1530-1544
Climate warming is leading to permafrost thaw in northern peatlands, and current predictions suggest that thawing will drive greater surface wetness and an increase in methane emissions. Hydrology largely drives peatland vegetation composition, which is a key element in peatland functioning and thus in carbon dynamics. These processes are expected to change. Peatland carbon accumulation is determined by the balance between plant production and peat decomposition. But both processes are expected to accelerate in northern peatlands due to warming, leading to uncertainty in future peatland carbon budgets. Here, we compile a dataset of vegetation changes and apparent carbon accumulation data reconstructed from 33 peat cores collected from 16 sub-arctic peatlands in Fennoscandia and European Russia. The data cover the past two millennia that has undergone prominent changes in climate and a notable increase in annual temperatures toward present times. We show a pattern where European sub-Arctic peatland microhabitats have undergone a habitat change where currently drier habitats dominated by Sphagnum mosses replaced wetter sedge-dominated vegetation and these new habitats have remained relatively stable over the recent decades. Our results suggest an alternative future pathway where sub-arctic peatlands may at least partly sustain dry vegetation and enhance the carbon sink capacity of northern peatlands. 相似文献