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1.
Sixteen 1-ha study plots covering five regeneration stages were simultaneously trapped five times over a 20-month period to provide data on small mammal response to vegetation changes following fire. Areas regenerating after fires from 9 years to 1 month before the investigation were sampled in a uniform open forest on a coastal sand plain. Two types of understorey were recognized: one dominated by true forest shrubs with which Rattus fuscipes, Antechinus stuartii and Sminthopsis murina were associated, and another dominated by heath elements where the addition of Pseudomys novaehollandiae and Mus musculus produced a significantly more diverse small mammal community. The two communities exhibited different responses to post-fire vegetation changes. Rattus fuscipes was the most abundant species and showed a logistic growth in biomass. No resident populations were established in the first 3 years, but a rapid increase in biomass occurred from 3 to 5 years to plateau after 8 years. Regeneration age had the greatest effect on R. fuscipes biomass mediated through the amount of accumulated leaf litter with additional variation being attributed to several vegetation structure variables and plant species diversity. A replacement sequence in time was observed for species reaching their maximum abundance (P. novaehollandiae and/or M. musculus → S. murina → A. stuartii → R. fuscipes) and was interpreted as species occupying stages in the succession when their optimal habitat requirements were fulfilled. These results have important implications for the design of management policies using fire or fire regimes as tools for habitat maintenance or alteration. A mosaic of forest patches of adequate size covering the entire range of seral stages is necessary to meet the optimum requirements of all the above species.  相似文献   

2.
The terrestrial lizard fauna of a regenerating mining path situated in open forest on coastal sand dunes was surveyed by pitfall trapping. The regeneration age of the series of chronosequence plots used ranged from 3.9 to 15.9 years. No lizards were recorded on plots less than 5.9 years old. Only four species of lizard were regularly found on the mining path. The skink Ctenotus robustus was the first colonizer and attained peak abundance and biomass after 9 years’ regeneration. Amphibolurus muricatus and Ctenotus taeniolatus were less abundant than C. robustus and did not appear on the mining path until 9 to 11 years’ regeneration. The abundance of C. taeniolatus continued to increase up to the oldest age class (16 years). Linear multiple regression analysis showed that sparse patchy vegetation in the 0–1 m layer and the amount of live shrub cover jointly accounted for 72% of the variance in abundance and 68% of variance in biomass for C. robustus. Fifty percent of the variance in C. taeniolatus abundance was explained by the proportion of plant species endemic to forest, regeneration age and the patchiness in understorey vegetation height. However, 67% of C. taeniolatus biomass was accounted for by plant species richness, plant species diversity, and the proportion of endemic forest and heath plant species. Some lizard species recorded from the surrounding forest were not found on the mining path. Lizards appear to recolonize revegetated areas more slowly than some other animal groups; this ‘sensitivity’ implies that they can act as important ‘indicator species’ of successful regeneration in disturbed areas. The non-linear response with time of some habitat variables makes it difficult to predict the time required for the complete rehabilitation of the mining path; however, it seems likely that a period well in excess of 20 years may be necessary before the lizard fauna on the mining path reaches premined levels.  相似文献   

3.
Changes during regeneration after sand mining for heavy minerals were studied on an area that previously supported open-forest on the Holocene high dune system in Myall Lakes National Park. Sixteen study areas, on which topsoil was replaced 0.5–10 yr ago, provided information on changes to be expected on any one site over that time period. A number of environmental variables was used in a linear multiple regression analysis to determine which of them is important in accounting for the variance and patterns observed in the biomass of two rodent species colonizing the regenerating areas. The first small-mammal colonist is the introduced house mouse (Mus musculus), an opportunistic species present on all sites. Its population density increases rapidly to a maximum at 3 yr after which it declines. Three environmental variables: percentage of bare sand, hardness of the soil in the first 30 cm, and a vegetation structure variable, account for 73% of the variance in M. musculus biomass. The native New Holland mouse (Pseudomys novaehollandiae) first appears between 4 yr and 5 yr after topsoil replacement and peaks between 8 yr and 9 yr, after which it also declines. A highly significant multiple regression accounts for 69% of the variance in P. novaehollandiae biomass using five significant variables: the proportíon of heath plants present, two vegetation structure variables, the amount of dead plant cover, and the topsoil depth. The species replacement observed confirms the succession indicated by previous work and suggests competitive interaction between these species. This study confirms the seral positions of rodent species in successions following both mining or fire. There is a stretched time axis for the mining succession following the more complete disruption of the substrate so regeneration more closely approximates primary rather than secondary succession. The non-linearity of the parameters makes it impossible to predict a recovery time and verifies our previous prediction that recovery estimates from heathland should not be extrapolated to forest.  相似文献   

4.
Habitat preferences of five species of small mammals were studied on a 6.6 ha trapping grid in heathland on an undulating, deep, sandy podzol at Cranbourne, Victoria. The 120 sites were sorted into groups using a polythetic, agglomerative, non-hierarchical clustering procedure with (i) floristic and (ii) structural data. The dispersion of 4051 trap captures over 28 months was studied in relation to these groupings. Rattus lutreolus showed no preference for any of the structural groups, but good differentiation was obtained with the floristic groups. Dispersion of R. lutreolus was related to a sedge-food index, and seasonal change in R. lutreolus dispersion was related to change in rainfall. The preference of R. rattus for areas of wet heath of high structural complexity was best revealed using the structural classification. The results for the other species tended to favour the floristic rather than structural groups. Pseudomys novaehollandiae and Isoodon obesulus preferred dry heath of a younger successional stage. Mus musculus captures showed a preference for the dry heath generally. This preference was most pronounced in spring when the population was declining. The wet community species (R. lutreolus, R. rattus) tended to be food specialists and habitat generalists and the dry community species P. novaehollandiae, I. obesulus, M. musculus), exhibited converse traits.  相似文献   

5.
Thirty-four vegetation clusters identified in the present study, after the application of TWINSPAN and DCA multivariate techniques, were assigned into 8 vegetation types, each of definite vegetation and habitat characters. The suggested vegetation types are well segregated along the DCA axis one which reflects soil moisture, salinity (as indicated by EC values), fertility (as indicated by the organic matter and nitrogen contents) and species diversity gradients. In general, soil moisture and soil fertility increase and species diversity decreases with the following sequence of vegetation types:Echinops spinosissimus-Ononis serrata on inland sand dunes,Pancratium maritimum on coastal sand dunes,Halocnemum strobilaceum-Salsola kali in saline sand deposits,Atriplex halimus-Chenopodium murale along the terraces and slopes of drains,Arthrocnemum glaucum-Tamarix nilotica in salt marshes,Chenopodium murale along the slopes of drains,Phragmites australis along the littoral zones of drains, andLemna gibba-Potamogeton crispus in the water zone. This sequence reflects also a gradient of human interference, starting with the vegetation of the less disturbed habitats (sand dunes and saline sand deposits) and ending with the fully man-made habitats (drain zones).  相似文献   

6.
In the subalpine tract of the Bogong High Plains (37°S, 147°E; altitude 1600–1800 m a.s.l.) the vegetation consists of a mosaic of snow gum (Eucalyptus pauciflora) woodland, heathland, grassland and wetland communities. Classification (polythetic-agglomerative) and ordination (principal co-ordinates analysis) of quadrat data from heathlands and grasslands on relatively well drained sites allowed the identification of four main heathland and grassland vegetation units. These units may be ranked in a structural and floristic continuum, from closed heath variously dominated by Prostanthera cuneata, Orites lancifolia and Phebalium squamulosum to closed heath dominated by P. squamulosum and Grevillea australis, open grassy heath of G. australis and Poa hiemata. and grassland of P. hiemata. The transition from Prostanthera closed heath to Poa grassland is correlated with gradients of decreasing steepness and rockiness of terrain, and increasing exposure and frost.  相似文献   

7.
The distribution of biomass of the macrophyte community in Badfish Creek was examined in three sections (A–C) totaling ten kilometers. Biomass samples were taken in a stratified-random manner, with sediment characteristics, depth, current velocity and incident light measured at each site to correlate individual biomass samples with environmental factors. Total community biomass decreased in the downstream section (C), with the biomass ofElodea canadensis decreasing abruptly below section A. The only environmental factors which were correlated with the decrease in macrophyte community biomass, especially that ofPotamogeton pectinatus, in section C was the increase in substrate heterogeneity and sand substrates which lacked surface gravel. The change in substrate was related to channelization. Considering the stream as a whole, the biomass of the dominant species,Potamogeton pectinatus, was correlated with incident light. Other species present wereCeratophyllum demersum andCladophora glomerata. Analysis of riparian vegetation type indicates that tree cover significantly reduced macrophyte biomass by incident light reduction.  相似文献   

8.
The abundance of two native rodent species, Rattus lutreolus and Pseudomys gracilicaudatus, has been shown to correlate with vegetation density in coastal wet heath. Fox's habitat accommodation model relates relative abundances of such small mammal species to heathland vegetation regeneration following disturbance. Implicit in the model is recognition that it is successional changes in vegetation, not time per se, that drives the responses of small mammal species along a regeneration axis. Using a brush‐cutter we deliberately removed approximately 85% of vegetation around trapping stations and recorded significant reductions in the abundance of both P. gracilicaudatus (an earlier‐stage colonizing species) and R. lutreolus (a late seral‐stage species). A significant decrease in the abundance of only the latter had been demonstrated previously when 60–70% of the vegetation had been removed. Following the brush‐cutting both species re‐entered the mammalian secondary succession at different times, first P. gracilicaudatus followed by R. lutreolus after the vegetation cover thresholds of each species had been reached. The impact of this habitat manipulation experiment was to produce a retrogression of the small mammal succession, experimentally demonstrating causality between changes in vegetation density and subsequent small mammal habitat use.  相似文献   

9.
Responses of alpine tree line ecosystems to increasing atmospheric CO2 concentrations and global warming are poorly understood. We used an experiment at the Swiss tree line to investigate changes in vegetation biomass after 9 years of free air CO2 enrichment (+200 ppm; 2001–2009) and 6 years of soil warming (+4 °C; 2007–2012). The study contained two key tree line species, Larix decidua and Pinus uncinata, both approximately 40 years old, growing in heath vegetation dominated by dwarf shrubs. In 2012, we harvested and measured biomass of all trees (including root systems), above‐ground understorey vegetation and fine roots. Overall, soil warming had clearer effects on plant biomass than CO2 enrichment, and there were no interactive effects between treatments. Total plant biomass increased in warmed plots containing Pinus but not in those with Larix. This response was driven by changes in tree mass (+50%), which contributed an average of 84% (5.7 kg m?2) of total plant mass. Pinus coarse root mass was especially enhanced by warming (+100%), yielding an increased root mass fraction. Elevated CO2 led to an increased relative growth rate of Larix stem basal area but no change in the final biomass of either tree species. Total understorey above‐ground mass was not altered by soil warming or elevated CO2. However, Vaccinium myrtillus mass increased with both treatments, graminoid mass declined with warming, and forb and nonvascular plant (moss and lichen) mass decreased with both treatments. Fine roots showed a substantial reduction under soil warming (?40% for all roots <2 mm in diameter at 0–20 cm soil depth) but no change with CO2 enrichment. Our findings suggest that enhanced overall productivity and shifts in biomass allocation will occur at the tree line, particularly with global warming. However, individual species and functional groups will respond differently to these environmental changes, with consequences for ecosystem structure and functioning.  相似文献   

10.
Carbon cycle feedbacks from permafrost ecosystems are expected to accelerate global climate change. Shifts in vegetation productivity and composition in permafrost regions could influence soil organic carbon (SOC) turnover rates via rhizosphere (root zone) priming effects (RPEs), but these processes are not currently accounted for in model predictions. We use a radiocarbon (bomb‐14C) approach to test for RPEs in two Arctic tall shrubs, alder (Alnus viridis (Chaix) DC.) and birch (Betula glandulosa Michx.), and in ericaceous heath tundra vegetation. We compare surface CO2 efflux rates and 14C content between intact vegetation and plots in which below‐ground allocation of recent photosynthate was prevented by trenching and removal of above‐ground biomass. We show, for the first time, that recent photosynthate drives mineralization of older (>50 years old) SOC under birch shrubs and ericaceous heath tundra. By contrast, we find no evidence of RPEs in soils under alder. This is the first direct evidence from permafrost systems that vegetation influences SOC turnover through below‐ground C allocation. The vulnerability of SOC to decomposition in permafrost systems may therefore be directly linked to vegetation change, such that expansion of birch shrubs across the Arctic could increase decomposition of older SOC. Our results suggest that carbon cycle models that do not include RPEs risk underestimating the carbon cycle feedbacks associated with changing conditions in tundra regions.  相似文献   

11.
Questions: Does stand age influence the direction and rate of post‐fire successional dynamics in coastal Calluna heaths and can old degraded heath vegetation be restored through reintroduction of fire? Location: Coastal heaths in the Tarva archipelago, central Norway. Methods: We investigated revegetation dynamics after experimental fires set in young (8 years since last fire) and old (>50 years since last fire) grazed heath stands. A repeated measures design was used, with floristic data recorded in permanent plots in the post‐fire successions (n=12) over a 7‐year period. The data were analysed using multivariate ordination techniques (PCA, RDA and PRC) and mixed effects models. Results: The age of Calluna stands strongly influenced post‐fire succession, different trends due to age explained 10.4% of variation in floristic data. Young heath showed faster succession towards pre‐fire community composition than old heath, and this could partially be explained by succession‐related factors: young heath had lower cover of mosses and lichens in the pre‐burned vegetation, and lower cover of litter early in succession. Young heath had a less pronounced overall community response to fire than old heath. Vegetative regeneration of C. vulgaris was absent in both old and young heath, but Calluna still re‐established as the dominant species within 5–7 years in both young and old stands. Regeneration dynamics were also affected by habitat conditions, different trends due to habitat explained 6% of variation. Conclusions: Our study demonstrates that old stands do develop characteristic heathland vegetation and structure after fire, and while potential invasives into the system such as trees and rhizomatous species are present, they do not impair Calluna regeneration or vegetation development towards the target heathland community composition and structure. Further, as our young stands are only in their second fire rotation after restoration, we suggest that characteristic dynamics of managed heathlands can re‐establish relatively rapidly, even in severely degenerated sites (>50 years since last fire). Site‐specific factors also need to be considered. We conclude that there is restoration potential in old heaths, despite slow dynamics in the first rotation.  相似文献   

12.
We investigated the role of post-fire residual organic matter (ROM) thickness as a driver of community assembly in eastern Newfoundland. We hypothesized that if post-fire community assembly is predominantly controlled by ROM thickness (an abiotic habitat filter), then post-fire species composition and functional traits should correspond to the depth and distribution of ROM. However, if species interactions (biotic filter) are the primary constraints on community assembly, then post-fire species composition and their functional traits should be independent of the depth and distribution of ROM. We tested these predictions in three relatively mature plant communities, Kalmia angustifolia heath, black spruce (Picea mariana)-Kalmia shrub savannah and black spruce forest. Through pre-fire stand reconstruction, we found evidence that the three communities originated from black spruce forest. ROM thickness in heath was almost twice that of shrub savannah and six times more than forest, suggesting a gradient in fire severity. Distribution of ROM corresponded to patterns in vegetation dominance, where thick ROM (>2 cm) filtered out black spruce in favour of Kalmia. ROM thickness was a strong predictor of vegetation composition and function between heath and forest, but this was not found between the shrub savannah and forest. We attribute this to species interactions and allelopathy, which may have become important when ROM thickness was suitable for both seed (black spruce) and vegetative (Kalmia) regenerating species. Thus, priority effects or “who came first” may have lead to shrub savannah formation when ROM thickness was ~2 cm. We conclude that abiotic habitat filtering of thick ROM (>2 cm) on (primarily) species’ regeneration traits was the primary driver of community divergence from forest to heath and shrub savannah.  相似文献   

13.
Vegetation dynamics of subalpine wetlands in the Sierra Nevada, California, were studied from 1988 through 1996. During this period, the region experienced a drought lasting from 1988 to 1994 and reaching its extreme in 1992. Our intention was to analyze the changes in plant species diversity, composition, and biomass, and interpret them in terms of drought resistance and resilience. Four plant communities, dominated respectively byCarex rostrata, Juncus balticus, Scirpus acutus orNuphar polysepalum were clearly discernible in the marsh along the water depth gradient. Species diversity ofCarex rostrata, Scirpus acutus andNuphar polysepalum communities was the highest during the driest year, 1992, while biomass was lowest for all vegetation types in that year. Dominance ofCarex andJuncus has not changed over the years, however,Scirpus almost totally disappeared from the marsh, and theNuphar zone become dominated by the rhizomatous perennial,Hippuris vulgaris, and terrestrial ruderals in dry years. In terms of changes in species composition,Carex andJuncus communities were both resistant and resilient. TheNuphar community seemed to be less resistant and more resilient, while theScirpus community was neither resistant nor resilient. If we consider biomass per plot as a variable of interest, regardless of species composition, thenCarex andJuncus were to some extent resistant and all plots were resilient because they were able to recover quickly to their pre-drought biomass. Life histories of dominant species were a more important determinant of community stability than species diversity.  相似文献   

14.
Soil pH was measured at two different spatial scales in coastal dunes on Norderney, North Sea, and in Mecklenburg-Vorpommern, Baltic Sea, Germany. Relationships between the variability in soil pH, species richness and species diversity are presented. Species richness and diversity were highest in grey dunes, where soil pH was at intermediate levels; both variables were lower in yellow and brown dunes. The variability in pH increased with increasing species diversity and also with scale. Overall, soil pH variability decreased with increasing vegetation cover. The lowest pH heterogeneity was found in heath dominated by Empetrum nigrum L. and grey dunes dominated by Campylopus introflexus (Hedw.) Brid. Increasing abundance of dominant species and decreasing species diversity of vegetation apparently reduces soil heterogeneity. Decreasing species diversity of vegetation is likely to explain decreasing variability in soil pH.  相似文献   

15.
The abundance and diversity of ectomycorrhizal fungi (EMF) was assessed based on the collection of basidiocarps during 12 months comprising the spring of 1995, and the summer, autumn, and winter of 1996, in three stands of young, middle-aged, and rotation age plantations of Pinus taeda and Eucalyptus dunnii, in the state of Santa Catarina, southern Brazil. A total of 3,085 collections yielded 34 presumed EMF taxa in ten genera, including mushroom-like and sequestrate species. Fruiting patterns of EMF differed with host and season, and host specificity was apparent in some. The overall relative importance (RI) and the Shannon diversity index (H) suggested that stands of E. dunnii had a more diverse aboveground EMF community than those of P. taeda. Overall, species of Scleroderma and Laccaria were not only the most abundant but also had the highest biomass values. The results show that a small number of species of abundant biomass and a larger number of species of less-abundant biomass characterize each forest class.  相似文献   

16.
Questions: Is plant species richness, diversity and above‐ground standing biomass enhanced after establishing exclosures on communal grazing lands? What factors influence the effectiveness of exclosures to restore degraded native vegetation in Tigray, Ethiopia? Location: Northern Ethiopia. Methods: We used a space‐for‐time substitution approach to detect changes in plant species richness, diversity and above‐ground standing biomass after conversion of communal grazing lands to exclosures. We selected replicated (n=3) 5‐, 10‐, 15‐ and 20‐year‐old exclosures and paired each exclosure with an adjacent communal grazing land to ensure that soil and terrain conditions were as similar as possible among each pair. Results: All exclosures displayed higher plant species richness, diversity and biomass than the communal grazing lands. Differences in plant species richness and biomass between an exclosure age and adjacent communal grazing land were higher in oldest than in youngest exclosures. In exclosures, much of the variability in plant species composition and biomass was explained by a combination of edaphic (total nitrogen, phosphorus, texture and soil pH) and site (precipitation and altitude) variables (R2=0.72–0.82). Edaphic and site variables also explained much of the variability in plant species composition in communal grazing lands (R2=0.76–0.82). Our study shows that all exclosures are at an early stage of succession. The increase in economically important indigenous shrub and tree species with exclosure age suggests that, with time, a valuable afromontane forest may develop. Conclusions: Establishment of exclosures on communal grazing lands is a viable option to restore degraded native vegetation. However, before expanding exclosures, the ecological consequences of additional exclosures should be investigated as further expansion of exclosures could increase grazing pressure on remaining grazing areas. Furthermore, consideration of edaphic and site variables will help optimize selection of areas for establishment of exclosures and enhance natural regeneration in exclosures in the future.  相似文献   

17.
To date, no study has explicitly addressed effects of variation in species diversity of root‐feeding herbivores on host plant biomass. Root‐feeding nematodes typically occur in multi‐species communities. In a three‐year field experiment, we investigated how variation in species diversity of root‐feeding nematodes affected nematode dynamics and response of the dune grass Ammophila arenaria to root‐feeder activity. This plant species needs regular burial by fresh beach sand to remain vigorous, suggesting that A. arenaria benefits from a temporary escape from root‐feeding soil organisms and that root‐feeders are involved in plant degeneration in stabilized dunes. We created series of ceased and continued sand burial and added the endoparasitic nematodes Meloidogyne maritima, Heterodera arenaria and Pratylenchus penetrans alone or in combination to A. arenaria. We included treatments with and without the whole soil community, measured plant biomass and quantified numbers of nematodes. Addition of H. arenaria and P. penetrans decreased numbers of M. maritima juveniles and delayed the first appearance in time of both juveniles and females, while numbers of males only decreased when plants had been buried. Burial with sand and addition of the other two endoparasites affected numbers of H. arenaria juveniles, while numbers of P. penetrans were low and not affected. Shoot biomass of A. arenaria was lower when M. maritima had been added alone than when the three species had been added together. Addition of root zone soil decreased biomass of all plant parts. Burial with sand decreased aboveground shoot biomass, whereas it increased belowground shoot and root biomass. Our results point at idiosyncratic effects of nematode diversity on A. arenaria biomass. Heterodera arenaria and P. penetrans protected their host by reducing numbers and delaying activity of M. maritima to a later stage in the growth season, when root‐feeding activity was less harmful for plant biomass development.  相似文献   

18.
基于长期定位监测数据,量化揭示了红锥纯林(Castanopsis hystrix)、10种与30种乡土树种混交林等3种乡土人工林植物群落的生物量、物种多样性、生物热力学健康水平(eco-exergy)和土壤理化性状在种植后13年内的发展动态,并与尾叶桉(Eucalyptus urophylla)纯林,以及自然恢复系统(灌草坡)进行了比较。结果表明:(1)研究期间,5种恢复模式的植物群落生物量均呈现波动上升趋势,但在发展节率上有所差异。13龄时的尾叶桉纯林与两种乡土树种混交林生物量显著高于其各自1龄时的水平,且显著高于自然恢复灌草坡;相较于其他人工林,红锥纯林生物量增长缓慢,但快于灌草坡;(2)5种恢复模式植物群落的物种多样性(物种丰富度、Shannon-Wiener指数、Pielou均匀度指数)在6至13龄间均呈下降趋势,且30种乡土树种混交林下降趋势最为显著。13龄时,两种混交林Shannon-Wiener指数略高于两种纯林,显著高于灌草坡;10种乡土树种混交林的Pielou均匀度指数略高于红锥纯林与30种乡土树种混交林,显著高于尾叶桉纯林与灌草坡。(3)4种人工林的植物群落生物热力学健康水平皆在6至13龄间显著增加;13龄时两种乡土混交林群落生态显著高于两种纯林,两种纯林显著高于灌草坡,且该差异主要源自于乔木层生态的差异。(4)不同植被恢复模式中,10种乡土树种混交林土壤养分的累积效果最佳,13龄时其土壤总氮含量显著高于红锥纯林和自然恢复灌草坡,但与30种乡土树种混交林和尾叶桉纯林无显著差异。(5)冗余分析结果显示,研究期间植被与土壤间的相关关系逐步建立,土壤理化性状对地上植被结构变化的解释度由1龄时的73.3%逐步上升至13龄时的82.0%,但只有土壤有机碳含量在13龄时与地上植被结构的相关性达到显著水平。上述结果表明,乡土种人工林与外来种人工纯林群落结构、生物热力学健康水平、及植被与土壤间关系的发展规律相似,且相对而言,混交林优于纯林,纯林优于自然恢复灌草坡。植被恢复的起始物种丰富度并不是越高越好;发展到13龄时,10种乡土树种混交林在植被结构与土壤改良方面均优于30种乡土树种混交林。植被与土壤间相关关系的建立是一个长期的过程,不同植被恢复模式对土壤理化性状的差异性影响难以在短期内有所显现。  相似文献   

19.
We tested the prediction that the successional replacement of plant species during succession on inland sand dunes results from the effects of an increase in nitrogen mineralization on competitive interactions. The growth and competitive strength of Festuca ovina and Deschampsia flexuosa on soil substrates with different amounts of soil organic matter or nitrogen supply were measured. Small tillers of Festuca ovina and Deschampsia flexuosa were grown in monocultures and 1:1-mixtures on soil columns with undisturbed layers of soil organic matter from different successional age. There was (a) no visible soil organic matter, (b) a thin soil organic layer (0.5 cm) and (c) a thicker soil organic layer (6.0 cm) present on the soil columns. The species were also grown on columns with no visible soil organic matter (bare sand) with two different levels of N fertilization to mimic the increased N mineralization in the older successional stages.In monoculture, Festuca produced more biomass on the substrates with a soil organic layer compared to the unfertilized sand substrate. It also produced more biomass on sand substrates with N fertilization. Deschampsia produced more biomass in treatments with a soil organic layer compared to the bare sand treatments, but did not respond to the ammonium-nitrate addition. In competition, Festuca seemed to be the stronger competitor on the unfertilized sand substrate. Festuca was also the better competitor on the N fertilized sand treatments, while on the treatments with a soil organic layer Deschampsia was the winning species. Our results do not support the hypothesis that an increase in N supply is responsible for the replacement of Festuca by Deschampsia that concur with the accumulation of soil organic matter during succession in inland dunes.  相似文献   

20.
采用典型样地法,以金马河流域温江段河岸带草本植物为研究对象,经实地踏查,根据采沙运沙干扰程度及样地具体使用情况,将样地划分为河滩地(未受采沙行为干扰,但后期受人类其他活动影响较大)、砾石地(采沙后经河水水位变化形成)、芦苇地[经运沙的车辆碾压形成,后长满芦苇(Phragmites australis)]、斑茅地[采沙后不再受水位影响的高地部分,后长满斑茅(Saccharum arundinaceum)]、沙坑(采沙后直接形成)5个生境类型,以探究不同生境对河岸带草本植物物种多样性和构件生物量的影响。结果表明:(1)在5个生境类型样地中共记录草本植物113种,隶属32科80属,其中沙坑生境草本植物物种数最多,共计59种,隶属21科46属,物种丰富度高,菊科(Compositae)、禾本科(Gramineae)植物在各样地中均较多。(2)斑茅地、芦苇地物种多样性指数较小,优势度指数较大,均匀度指数较小,群落物种分布极不均匀,集中度与均匀度较差,群落存在极大的不稳定性。(3)河滩地植物构件生物总量最少,斑茅地最多且根、茎干重与其他生境存在显著差异。(4)与其它生境类型相比,沙坑物种多样性丰富,分布均匀,构件生物量较多,其环境有利于河岸带植物生长。  相似文献   

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