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1.
Facilitation (positive plant–plant interactions) is a potential means to accelerate vegetation restoration in arid areas. Shrubs can accelerate vegetation recovery by means of soil amelioration, but this effect has not been evaluated at large spatial scales or across scales. Here, we examined the facilitative function of shrub change across spatial scales at a desert steppe in Mongolia. Using a high-resolution satellite image, we established five 2500 m2 plots in each of three shrub density classes (low, moderate, high) in a desert steppe in Mongolia. To evaluate the facilitative functions of shrubs at multiple spatial scales, we recorded the total number of plant species at three nested spatial scales in each plot: 25, 400, and 2500 m2. The facilitative effect of shrubs on plant species richness was more pronounced at larger scales. Denser shrub communities increased plant species diversity at a larger scale. However, the increased taxonomic diversity was not clearly related to increased functional diversity in this system. This scale dependency in species diversity can be explained by the degree to which spatial heterogeneity of habitats within the plots increased as plot size increased. These results support the hypothesis of scale-dependent changes in the balance between facilitation and competition. Therefore, transplanting shrub saplings at high-density and a larger scale could potentially improve the success of vegetation restoration in arid regions.  相似文献   

2.
Understanding processes that underlie ecological resistance to weed invasion is critical for sustainable restoration of invaded plant communities. Experimental studies have demonstrated that invasive nitrophilic annuals can be controlled by addition of carbon to reduce soil nitrate concentrations, sometimes leading to enhanced establishment of native plants. However, effects of carbon supplements on soil nitrate are temporary, and the longer-term value of carbon supplementation as a restoration tool is dependent on the resistance of the re-established ecosystem to repeat invasion. We investigated whether re-established swards of the tussock grass Themeda australis (R.Br.) Stapf (a natural understorey dominant in mesic grassy woodlands of SE Australia) could suppress soil nitrate concentrations, and through this or other means, could impart ongoing resistance to exotic invasion in restored woodlands. In a remnant invaded by exotic annuals, we applied three plot treatments (carbon supplements, annual spring burns and untreated control) and two seed treatments (± Themeda seed) in a replicated, factorial design. Within 3 years, successful establishment of Themeda swards on burnt and carbon-supplemented plots was associated with a reduction in soil nitrate to levels comparable with non-invaded, Themeda-dominated reference sites in the region (<3 mg/kg), and significantly reduced exotic cover compared with unseeded plots. By contrast, on plots not seeded with Themeda, soil nitrate increased after cessation of carbon addition and exotic cover returned to levels comparable with untreated control plots, despite a high cover of other native perennial grasses. Few persistent effects of carbon supplements or spring burning on soil nutrients were evident 9–19 months after cessation of these treatments. Results suggest that Themeda is a keystone species that regulates nitrate cycling, thereby imparting ecological resistance to invasion by nitrophilic annuals.  相似文献   

3.
Quarry exploitation and restoration practices are expected to have overarching and contrasting impacts on animal communities. Although many studies describe these impacts, they generally overlook the effects on population dynamics and individual movements. We assessed the impacts of quarry exploitation and restoration activity on population dynamics, individual movement, and habitat use of a sand‐dwelling specialist beetle (Scarites cyclops). The study was performed on three plots: one adjacent to the margin of quarry exploitation, another subjected to restoration practices, and a control plot with no disturbance. A capture‐mark‐recapture approach was undertaken to estimate population parameters, movement, and habitat use. In the exploitation plot S. cyclops exhibited lower probability of recapture and lower apparent survival, as well as many movements fleeing away from quarry limits. Habitat suitability modeling showed that the exploitation plot provided better habitat conditions for the species than the restoration plot. It exhibited higher bare ground cover with scattered clumps of vegetation and higher proportions of fine sand (<0.4 mm). In the restoration plot, S. cyclops population showed a lower abundance, with a higher rate of recaptures, and a more limited dispersal ability of the individuals. There is an apparent early stage of colonization by S. cyclops in the restoration plot, but movements may already be hampered by unsuitable habitat restoration (higher herbaceous cover and different soil texture). We suggest preserving suitable habitat patches in the vicinity of the impacted areas and providing dispersal routes. Beyond vegetation, soil texture must be considered to allow local animal communities to establish in restored areas.  相似文献   

4.
The ecological role of biodiversity in achieving successful restoration has been little explored in restoration ecology. We tested the prediction that we are more likely to create persistent, species‐rich plant communities by increasing the number of species sown, and, to some degree, by varying functional group representation, in experimental prairie plantings. There were 12 treatments consisting of 1‐, 2‐, 3‐, 4‐, 8‐, 12‐, and 16‐species mixtures of native perennials representing four functional groups (C4 grasses, C3 grasses, nitrogen‐fixing species, and late‐flowering composites) that predominate within Central Plains tallgrass prairies. In 2000, species were seeded into square plots (6 × 6 m), with five replicates per treatment, on former agricultural land. Annually, we measured total species richness and evenness, target species richness and cover, and richness and cover of resident species (i.e., those emerging from the seed bank). Both target species richness and rate of establishment of target communities were highest in the most species‐rich mixtures, but there was no additional benefit for treatments that contained more than eight species. Richness of resident species did not vary with target species richness; however, cover by resident species was lower in the higher target species treatments. Our results, indicating that establishment of species‐rich prairie mimics can be enhanced by starting with larger numbers of species at the outset, have implications for grassland restoration in which community biodiversity creation and maintenance are key goals.  相似文献   

5.
Kotiluoto  Riitta 《Plant Ecology》1998,136(1):53-67
In the Turku Archipelago of SW Finland the traditional animal husbandry dramatically decreased in 1950s after which the unused semi-natural pastures and meadows began to develop into less species rich shrub and tree communities. Restoration of some semi-natural meadows and pastures started in the late 1970s. Removing trees and shrubs, grazing, mowing, and pollarding deciduous trees were used as restoration of practises. Vegetation changes were followed from forty-one permanent sample plots established on restored areas. In this paper the data before restoration and 7–8 years after the first monitoring was analysed with parametric tests. The sample plots were divided into three restoration groups where the main restoration practises were: group 1. grazing, group 2. thinning (clearing plots from shrubs and removing some trees), group 3. thinning, mowing, and grazing (old wooded meadows). The results showed that: (1) The vegetation changed during analysed time. The number of species increased in all restored areas even though the changes were more pronounced in grazed areas and wooded meadows than in thinned areas. During restoration many common herb and grass species immigrated into the sample plots, but very few new indicator species of meadows were recorded. Most of the new species were found in few numbers in a sample plot which led to the significant increase in the number of sparse species (percentage cover < 1) in all restoration groups. The grasses benefited more from the restoration than herbs increasing their percentage cover significantly in grazed areas and in wooded meadows. In thinned areas the total percentage cover of the ten most dominant herb and grass species increased significantly. (2) The different restoration groups changed vegetation quite similarly. In grazed areas and in wooded meadows significant changes were slightly more numerous than in thinned areas. (3) The differences between the islands in vegetation changes were not pronounced. The added variance components among islands increased during restoration which probably indicated that the restoration practises as well as the species pool of the islands influenced the success of restoration.  相似文献   

6.
大保高速公路老营段路域植被生态恢复   总被引:4,自引:0,他引:4  
路域植被生态系统的恢复与重建不仅是道路生态学的重要研究内容,而且也是恢复生态学的重要研究领域.以大保高速公路老营段路域植被生态系统为对象,对比分析了8种植被恢复模式的作用效果与作用机理.研究结果表明,在相同的恢复时间内,自然恢复的植物群落中本土植物的比例相对较高,自然恢复是该区路域植被恢复的理想模式之一.随着恢复演替时间的推移,所有群落中木本植物的比例不断增加,草本植物的比例不断下降,植物群落分层现象明显,植物群落向原生植被发生进展或偏途演替.补播本土植物是促进植被恢复演替进程的主要途径之一,不仅可以增加乡土物种的比例、增加植物群落的多样性和均匀度,而且随着恢复时间的推移,可以形成层次明显、功能群组合合理的植物群落.人工蓝桉经济林不仅降低了植物群落及各功能群的多样性、丰富度和均匀度,而且在一定程度上增加了潜在生态风险.研究结果还表明,植物群落中当地物种的比例、植物群落的物种多样性和植物群落的盖度可以作为植被恢复成功与否的重要判定指标.  相似文献   

7.
The objective of this study was to determine the influence of distance from surface water on riparian woodland communities in the Okavango Delta. Vegetation sampling was conducted in seven sites within the Okavango Delta in 20 m × 10 m belted plots placed perpendicular to the river bank. The plots were placed at 0–10 m, 10–20 m, 20–30 m, 30–40 m and 40–50 m distance classes increasing away from the river bank. Tree height, basal area, species richness, canopy cover and diversity were determined for each distance class. Indicator species analysis was used to determine the characteristic species at each distance class. Single‐factor ANOVA and Tukey post hoc analysis were used to compare species diversity, mean tree height, cover and basal area between distance classes. Correlation between distance from surface water and vegetation parameters was sought using Spearman regression analysis. All parameters except for species richness varied significantly (< 0.05) along distance from surface water. Distance from surface water was positively correlated all vegetation parameters except for mean species richness/plot. These results show that distance from surface water influences riparian plant community composition and distribution in the Okavango Delta. This implies that riparian plant species can be indicators of long‐term hydrologic conditions in the Delta.  相似文献   

8.
Woody debris is an important component of forest ecosystems, but its use in mine site restoration has been limited and it can be slow to build up naturally. A new technique of spreading snipped wood waste onto restored mine pits prior to seeding has been subjected to a preliminary trial at Alcoa's Huntly mine site, in the northern jarrah forest of south‐western Western Australia. We examined whether the application of snipped wood during restoration encourages the return of ground‐ and litter‐dwelling invertebrates without negatively suppressing plant establishment. Invertebrates were sampled across three seasons from experimental plots treated with 0 t/ha (control), 100 t/ha or 300 t/ha snipped wood waste. Invertebrate communities in treatment plots comprised higher numbers and diversity of wood and litter decomposers such as mites, Diplopoda, Dermaptera and Blattodea than control plots. Plant responses were variable, with wood treatment resulting in lower tree and overall plant density but having no effects on plant species richness or plant cover. Wood treatment plots were associated with higher soil nitrogen than controls. We hypothesise that the use of a fine wood treatment at the lowest rate of 100 t/ha (approximately 30% wood cover) is likely to enhance the diversity and abundance of invertebrates in restored areas, with minimal effect on plant establishment. Encouraging a diverse invertebrate fauna to recolonise restoration should help speed up succession and ecosystem functions such as decomposition and nutrient cycling, and more quickly return the land to previous ecosystem values.  相似文献   

9.
10.
We assessed the impacts of co‐occurring invasive plant species on fire regimes and postfire native communities in the Mojave Desert, western USA. We analyzed the distribution and co‐occurrence patterns of three invasive annual grasses (Bromus rubens, Bromus tectorum, and Schismus spp.) known to alter fuel conditions and community structure, and an invasive forb (Erodium cicutarium) which dominates postfire sites. We developed species distribution models (SDMs) for each of the four taxa and analyzed field plot data to assess the relationship between invasives and fire frequency, years postfire, and the impacts on postfire native herbaceous diversity. Most of the Mojave Desert is highly suitable for at least one of the four invasive species, and 76% of the ecoregion is predicted to have high or very high suitability for the joint occurrence of B. rubens and B. tectorum and 42% high or very high suitability for the joint occurrence of the two Bromus species and E. cicutarium. Analysis of cover from plot data indicated two or more of the species occurred in 77% of the plots, with their cover doubling with each additional species. We found invasive cover in burned plots increased for the first 20 years postfire and recorded two to five times more cover in burned than unburned plots. Analysis also indicated that native species diversity and evenness as negatively associated with higher levels of relative cover of the four invasive taxa. Our findings revealed overlapping distributions of the four invasives; a strong relationship between the invasives and fire frequency; and significant negative impacts of invasives on native herbaceous diversity in the Mojave. This suggests predicting the distributions of co‐occurring invasive species, especially transformer species, will provide a better understanding of where native‐dominated communities are most vulnerable to transformations following fire or other disturbances.  相似文献   

11.
Given that land‐use change is the main cause of global biodiversity decline, there is widespread interest in adopting land‐use practices that maintain high levels of biodiversity, and in restoring degraded land that previously had high biodiversity value. In this study, we use ant taxonomic and functional diversity to examine the effects of different land uses (agriculture, pastoralism, silviculture and conservation) and restoration practices on Cerrado (Brazilian savanna) biodiversity. We also examine the extent to which ant diversity and composition can be explained by vegetation attributes that apply across the full land management spectrum. We surveyed vegetation attributes and ant communities in five replicate plots of each of 13 land‐use and restoration treatments, including two types of native vegetation as reference sites: cerrado sensu stricto and cerradão. Several land‐use and restoration treatments had comparable plot richness to that of the native reference habitats. Ant species and functional composition varied systematically among land‐use treatments following a gradient from open habitats such as agricultural fields to forested sites. Tree basal area and grass cover were the strongest predictors of ant species richness. Losses in ant diversity were higher in land‐use systems that transform vegetation structure. Among productive systems, therefore, uncleared pastures and old pine plantations had similar species composition to that occurring in cerrado sensu stricto. Restoration techniques currently applied to sites that were previously Cerrado have focused on returning tree cover, and have failed to restore ant communities typical of savanna. To improve restoration outcomes for Cerrado biodiversity, greater attention needs to be paid to the re‐establishment and maintenance of the grass layer, which requires frequent fire. At the broader scale, conservation planning in agricultural landscapes, should recognize the value of land‐use mosaics and the risks of homogenization.  相似文献   

12.
Question: Do traits of liana regeneration differ among secondary forest types of varying land‐use history and primary forest? Location: Eighty kilometers north of Manaus, Brazil. Methods: We compared plant functional traits and growth rates of liana regeneration (<1.7‐m length) among two secondary forest types and primary forest. Secondary forest types were: Vismia (on land formerly clear‐cut, used for pasture and intensively burned) and Cecropia (no pasture usage or intensive fires after clear‐cut). Results: A principal components analysis indicated that most of the primary forest species exhibited a similar habit and were characterized by short shoots and small, round leaves with low specific leaf area, whereas secondary forest species had a broad range of trait values. At the plot level, primary and secondary forest communities were separated mainly by plant length and leaf size. Plant size varied more within secondary than within primary forest plots. The two secondary forest types could not be separated based on the traits of liana regeneration. Relative growth rate (RGR) did not correlate significantly with any measured plant trait, except for a negative relation to initial length. RGR increased with decreasing canopy cover and was highest in Vismia forest plots. Conclusion: Plant functional traits of liana regeneration were more similar in the primary forest and differed substantially from secondary forests, yet canopy cover only partly explained the observed differences.  相似文献   

13.
Historical data from the 1930s were compared with new data gathered during the 2000s to evaluate the effects of increased numbers of larger stature submersed species (both elodeids and characeans) on resident isoetid communities. The cover and species richness of submersed species were assessed in 23 seepage lakes in northwestern Wisconsin, USA, using randomly located 1 m × 1 m plots. Water clarity, conductivity and residential land use were determined on a whole-lake basis and the sediment type and water depth were recorded at each plot. The probability of elodeids or characeans occurring in isoetid plots increased with the number of elodeids and characeans gained by a lake since the 1930s, with additions ranging from two to 15 species per lake. However, not all species were equally likely to co-occur with isoetids. Six elodeid species (Najas flexilis, Najas gracillima, Potamogeton gramineus, Potamogeton pusillus, Potamogeton spirillus and Vallisneria americana) along with Chara spp. were the most frequent isoetid associates, while other species that were common in the lakes, such as Elodea canadensis and Potamogeton robbinsii, were less frequent in isoetid plots. The lake-wide proportion of isoetid plots colonized by elodeids or characeans ranged from 5% to 100%, with increasing conductivity and total elodeids (plus Chara spp. and Nitella spp.) the strongest predictors of this colonization. Approximately half (49.6%) of all isoetid plots sampled had elodeids or characeans present (39.2% elodeids, 7.4% elodeids and characeans, 3.0% characeans), and isoetid cover and species richness were lower when these larger stature species were present. The risks this colonization poses for the long-term viability of isoetid species appeared to depend on multiple factors, including whole-lake characteristics, opportunities for refuge, and connections among regional isoetid populations. There was evidence of a time lag between the introduction of elodeid or characean species to a lake and invasion of isoetid plots within the lake, a process that deserves further study.  相似文献   

14.
The identification of shape and size of sampling units that maximises the number of plant species recorded in multiscale sampling designs has major implications in conservation planning and monitoring actions. In this paper we tested the effect of three sampling shapes (rectangles, squared, and randomly shaped sampling units) on the number of recorded species. We used a large dataset derived from the network of protected areas in the Siena Province, Italy. This dataset is composed of plant species occurrence data recorded from 604 plots (10 m × 10 m), each divided in a grid of 16 contiguous subplot units (2.5 m × 2.5 m). Moreover, we evaluated the effect of plot orientation along the main environmental gradient, to examine how the selection of plot orientation (when elongated plots are used) influences the number of species collected. In total, 1041 plant species were recorded from the study plots. A significantly higher species richness was recorded by the random arrangement of 4 subplots within each plot in comparison to the ‘rectangle’ and ‘square’ shapes. Although the rectangular shape captured a significant larger number of species than squared ones, plot orientation along the main environmental gradient did not show a systematic effect on the number of recorded species. We concluded that the choice of whether or not using elongated (rectangular) versus squared plots should dependent upon the objectives of the specific survey with squared plots being more suitable for assessing species composition of more homogeneous vegetation units and rectangular plots being more suited for recording more species in the pooled sample of a large area.  相似文献   

15.
This study assessed the effectiveness of plot patterns for estimating recruit density of woody species in the dense forest of Lama Reserve (Bénin). The experimental design consisted of thirty 0.04 ha plots randomly settled in the forest and each subdivided into four hundred 1‐m² quadrats. Within each quadrat, recruits (dbh ≤10 cm) were counted and saplings (h ≥ 2 m and 2 cm ≤ dbh < 7 cm) and young trees (h ≥ 2 m and 7 cm ≤ dbh < 10 cm) were measured in dbh. In each 0.04 ha plot, seven different plot shapes and sizes were considered by grouping adjacent 1‐m2 quadrats. Relationship between mean square error of the estimation of the density of recruitments and the plot sizes was modelled using the Smith law. Results obtained showed an average value of density of recruitments of 10.7 plants/m2 with Green index value of 0.01. Shape and size of plots highly influenced the estimation of the density of recruitments. Rectangular plots of length/width = 2 and size of 72 m² (12 m × 6 m) were most efficient for the estimation of the density of recruitments in tropical dense forest with standard error of 0.79 plants/m2.  相似文献   

16.
Questions: Do ordination patterns differ when based on vegetation samples recorded in plots of different size? If so, how large is the effect of plot size relative to the effects of data set heterogeneity and of using presence/absence or cover‐abundance data? Can we combine plots of different size in a single ordination? Methods: Two homogeneous and two heterogeneous data sets were sampled in Czech forests and grasslands. Cover‐abundances of plant species were recorded in series of five or six nested quadrats of increasing size (forest 49‐961 m2; grassland 1‐49 m2). Separate ordinations were computed for plots of each size for each data set, using either species presences/absences or cover‐abundances recorded on an ordinal scale. Ordination patterns were compared with Procrustean analysis. Also, ordinations of data sets jointly containing plots of different size were calculated; effects of plot size were evaluated using a Monte Carlo test in constrained ordination. Results: The results were consistent between forest and grassland data sets. In homogeneous data sets, the effect of presence/absence vs. cover‐abundance was similar to, or larger than, the effect of plot size; for presence/absence data the differences between ordinations of differently sized plots were smaller than for cover‐abundance data. In heterogeneous data sets, the effect of plot size was larger than the effect of presence‐absence vs. cover‐abundance. The plots of smaller size (= 100 m2 in forests, = 4 m2 in grasslands) yielded the most deviating ordination patterns. Joint ordinations of differently sized plots mostly did not yield patterns that would be artifacts of different plot size, except for plots from the homogeneous data sets that differed in size by a factor of four or higher. Conclusions: Variation in plot size does influence ordination patterns. Smaller plots tend to produce less stable ordination patterns, especially in data sets with low ß‐diversity and species cover‐abundances. Data sets containing samples from plots of different sizes can be used for ordination if they represent vegetation with large ß‐diversity. However, if data sets are homogeneous, i.e. with low ß‐diversity, the differences in plot sizes should not be very large, in order to avoid the danger of plot size differences distorting the real vegetation differentiation in ordination patterns.  相似文献   

17.
In the Taita Hills in southern Kenya, remnants of the original Afromontane forest vegetation are restricted to isolated mountain peaks. To assess the level of degradation and the need for forest restoration, we examined how forest plant communities and their indicator species vary between and within remnant patches of cloud forest. We used ordinal abundance data to compare plant communities in eight forest fragments. We also analyzed data on the diversity and abundance of trees in 57 0.1 ha plots to compare tree communities within and between the largest two of these fragments, Ngangao (120 ha) and Mbololo (220 ha). The extant vegetation of the Taita Hills at landscape scale consists of secondary moist montane to intermediate montane forest. There was a high species dissimilarity between fragments (69%). Variation in species composition coincided with an abiotic gradient related to elevation. At plot level, secondary successional species and species of forest edges were most abundant and most frequent. Inferred clusters of plots almost entirely coincided with the two forest fragments. Indicator species associated with forest margins and gaps were more frequent in the smaller of the two forest fragments, while indicators for the larger fragment were more typical for less disturbed moist forest. Abiotic site variability but also different levels of disturbance determine site-specific variants of the montane forest. Conservation efforts should not only focus on maintaining forest quantity (size), but also on forest quality (species composition). Late-successional rainforest species are underrepresented in the woody plant communities of the Taita Hills and assisting restoration of viable populations of cloud forest climax tree species is urgently needed.  相似文献   

18.
19.
Forest restoration requires strategies such as passive restoration to balance financial investments and ecological outcomes. However, the ecological outcomes of passive restoration are traditionally regarded as uncertain. We evaluated technical and legal strategies for balancing economic costs and ecological outcomes of passive versus active restoration in agricultural landscapes. We focused in the case of Brazil, where we assessed the factors driving the proportion of land allocated to passive and active restoration in 42 programs covering 698,398 hectares of farms in the Atlantic Forest, Atlantic Forest/cerrado ecotone and Amazon; the ecological outcomes of passive and active restoration in 2955 monitoring plots placed in six restoration programs; and the legal framework developed by some Brazilian states to balance the different restoration approaches and comply with legal commitments. Active restoration had the highest proportion of land allocated to it (78.4%), followed by passive (14.2%) and mixed restoration (7.4%). Passive restoration was higher in the Amazon, in silviculture, and when remaining forest cover was over 50 percent. Overall, both restoration approaches showed high levels of variation in the ecological outcomes; nevertheless, passively restored areas had a smaller percentage canopy cover, lower species density, and less shrubs and trees (dbh > 5 cm). The studied legal frameworks considered land abandonment for up to 4 years before deciding on a restoration approach, to favor the use of passive restoration. A better understanding of the biophysical and socioeconomic features of areas targeted for restoration is needed to take a better advantage of their natural regeneration potential.  相似文献   

20.
A field study was conducted at Little Topashaw Creek in northern Mississippi, aimed at expanding the limited database on the survivorship of Salix nigra (black willow) cuttings planted on riparian restoration sites. We tested the hypothesis that sediment moisture availability (deficit, excess) as mediated by sediment texture and depth to the prevailing water table is a major factor governing black willow survival during the initial stage of establishment following transplanting. Replicated plots were established across elevational gradients and a range of soil texture. Each plot contained 16 planted cuttings (2.5 cm diameter × 2.5 m length). Plot depth to water table, soil texture, and soil redox potential were measured. Plant gas exchange, leaf chlorophyll content, growth, and survival were monitored periodically over two growing seasons. Survival was best at low elevation compared to cuttings planted at mid- and high elevations. Poor survival and growth were noted for cuttings that encountered sediment moisture deficits in plots with coarse texture while the best cutting survival was recorded for intermediate sand content plots. Results indicated that plot location on the bank and soil texture are two important factors that influence riverbank restoration success. Therefore, any riparian restoration plan should include careful assessment of these factors prior to undertaking such efforts.  相似文献   

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