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1.
In tallgrass prairie reconstruction, the way desired seeds are arranged on the landscape may affect species establishment, species persistence, and the establishment and persistence of undesired (nonseeded) species from the local propagule pool. To test effects of species seeding pattern on how grasslands develop spatially, we seeded 20—4 × 4–m bare soil plots with 16 tallgrass prairie species. Treatment plots were divided into 16—1 × 1–m subplots, 64—0.5 × 0.5–m subplots, 256—0.25 × 0.25–m subplots, or 1,024—0.125 × 0.125–m subplots. Each species was hand broadcast into separate subplots (1 m2 total area/species) within each plot. An additional treatment included uniformly mixing and broadcasting all seeds across a plot. We recorded species cover at the 0.125 × 0.125–m scale within each plot at the beginning of the second and third growing seasons. While species persistence was greatest within plots seeded with larger subplots, plots with smaller subplots were more spatially diverse and less occupied by nonseeded species over time than larger subplot and mixed plots. As is common in reconstruction efforts, establishment was variable among species and seeding with monospecific subplots enhanced colonization of desired rhizomatous species (e.g., Heliopsis helianthoides, Monarda fistulosa, Elymus virginicus) into unoccupied locations at the expense of species from the local propagule pool. Results suggest that seeding species in smaller, monospecific patches could result in grasslands with a more balanced native species composition than those established with a seed mixture approach. 相似文献
2.
Disturbances create fluctuations in resource availability that alter abiotic and biotic constraints. Exotic invader response may be due to multiple factors related to disturbance regimes and complex interactions between other small- and large-scale abiotic and biotic processes that may vary across invasion stages. We explore how cheatgrass responds to both frequency and season of prescribed burning for a 10-year period in ponderosa pine forested stands. To understand interactions of fire disturbance, other abiotic factors, biotic resistance, and propagule pressure, we use long-term data from different spatial scales representing different invasion stages (local establishment or spread and broader scale extent/impact) to model cheatgrass dynamics. We found that after 10 years, cheatgrass cover increased with fall burning regardless of burn frequency (1 burn vs. 3 burns). There was no evidence that cheatgrass invasion is decreasing through time even in areas burned only once. Factors important for explaining local fine-scale cheatgrass establishment and spread, and broader scale extent/impact varied. The spatial extent of the first burns facilitated fine-scale cheatgrass establishment while bare soil cover constrained establishment. Biotic resistance, in the form of native annual forb cover, constrained fine-scale cheatgrass spread. Initial cheatgrass abundance in 2002, a factor related to propagule pressure, was key for explaining the broader scale extent/impact of cheatgrass by 2012. Biotic resistance, in the form of native perennial grass cover, constrained extent/impact but only when initial cheatgrass abundance was low. Our findings regarding factors affecting invasion dynamics may be useful to consider for future restoration and conservation efforts in burned ponderosa pine forests. 相似文献
3.
Margot Vanhellemont Kris Verheyen Luc De Keersmaeker Kris Vandekerkhove Martin Hermy 《Biological invasions》2009,11(6):1451-1462
Since most studies on Prunus serotina in Western Europe focused on heavily invaded areas, we wondered whether P. serotina also acts as an aggressive invader in areas with a low propagule pressure. Based on long-term data for the Liedekerke forest
reserve, we found that connectivity to seed sources and light availability were the major drivers of P. serotina presence: long-distance dispersal events and ‘windows of opportunity’ seem to direct P. serotina colonization. In the studied forest, P. serotina could not be considered an aggressive invader since its spread slowed down rather quickly and did not hamper the establishment
of native tree species. Furthermore, understory P. serotina showed low growth and seed production, while the high Rubus cover hampered germination and establishment. Nonetheless, calamities opening up the canopy layer in the few areas with high
P. serotina sapling density might alter the course of the invasion process. 相似文献
4.
Non-native plant species richness may be either negatively or positively correlated with native species due to differences
in resource availability, propagule pressure or the scale of vegetation sampling. We investigated the relationships between
these factors and both native and non-native plant species at 12 mainland and island forested sites in southeastern Ontario,
Canada. In general, the presence of non-native species was limited: <20% of all species at a site were non-native and non-native
species cover was <4% m−2 at 11 of the 12 sites. Non-native species were always positively correlated with native species, regardless of spatial scale
and whether islands were sampled. Additionally, islands had a greater abundance of non-native species. Non-native species
richness across mainland sites was significantly negatively correlated with mean shape index, a measure of the ratio of forest
edge to area, and positively correlated with the mean distance to the nearest forest patch. Other factors associated with
disturbance and propagule pressure in northeastern North America forests, including human land use, white-tailed deer populations,
understorey light, and soil nitrogen, did not explain non-native richness nor cover better than the null models. Our results
suggest that management strategies for controlling non-native plant invasions should aim to reduce the propagule pressure
associated with human activities, and maximize the connectivity of forest habitats to benefit more poorly dispersed native
species. 相似文献
5.
Oscar J. Abelleira Martínez 《Plant Ecology》2010,211(1):49-64
There is concern that secondary forests dominated by introduced species, known as novel forests, increase taxonomical similarity
between localities and lead to biotic homogenization in human-dominated landscapes. In Puerto Rico, agricultural abandonment
has given way to novel forests dominated by the introduced African tulip tree Spathodea campanulata Beauv. (Bignoniaceae). In this study, I characterized the tree species composition of S. campanulata forests in Puerto Rico as means to evaluate if biotic homogenization is occurring. Non-metric multidimensional scaling was
used to examine what variables were related to the large (≥10 cm diameter at breast height [DBH]), small (≥2.5 to <10 cm DBH),
and juvenile (<2.5 cm DBH) tree species composition of 20 sites. Species composition was strongly related to substrate properties,
less related to land use history, and unrelated to spatial attributes. The introduced species component was low (mean = 17%,
S.E. = 1.8) and compositional differences were mostly due to native tree species of secondary to old growth forests on equivalent
substrates. Animals appear to disperse most species (86%) into these forests yet because of this some introduced species will
persist. Although uncommon species were largely absent, recent species establishment is shaped by substrate properties making
biotic homogenization in these forests unlikely. The S. campanulata forests of Puerto Rico facilitate native tree species establishment in lands where poor management practices extirpated the
original forest. These results highlight the importance of remnant old growth forests or trees that act as seed dispersal
sources and facilitate native species recovery in novel forests. 相似文献
6.
Regeneration processes of riparian Robinia
pseudoacacia forests after clear-cutting were investigated through dendroecological and microsatellite polymorphism analyses. Age determination
of regenerated R. pseudoacacia trees based on the dendroecological analysis revealed that forests regenerating after clear-cutting were composed of trees
that mostly established within a few years after clear-cutting. This suggests that the stimulus to form new shoots was evoked
by clear-cutting but faded within a few years. Genet identification via the microsatellite polymorphism analysis showed that
ramet trees belonging to the same genet were distributed in a cluster. Almost all trees regenerated asexually through new
ramet formation on the cut stumps and residual horizontal roots after clear-cutting. AMOVA with microsatellite markers showed
that among- and within-population variations contributed 6 and 94% to the total variation, respectively, suggesting that R.
pseudoacacia trees in the forests were initially established from seeds dispersed randomly from mother trees in a wide area. 相似文献
7.
QIFANG GENG CHUNLAN LIAN SUSUMU GOTO JIANMIN TAO MEGUMI KIMURA MD SAJEDUL ISLAM TAIZO HOGETSU 《Molecular ecology》2008,17(21):4724-4739
Mangrove tree species form ecologically and economically important forests along the tropical and subtropical coastlines of the world. Although low intrapopulation genetic diversity and high interpopulation genetic differentiation have been detected in most mangrove tree species, no direct investigation of pollen and propagule dispersal through paternity and/or parentage analysis and spatial genetic structure within populations has been conducted. We surveyed the mating system, pollen and propagule dispersal, and spatial genetic structure in a natural population of Kandelia candel, one of the typical viviparous mangrove tree species, using nuclear and chloroplast microsatellite markers. High diversity and outcrossing rates were observed. Paternity and parentage analysis and modelling estimations revealed the presence of an extremely short-distance component of pollen and propagule dispersal (pollen: 15.2 ± 14.9 m (SD) by paternity analysis and 34.4 m by modelling; propagule: 9.4 ± 13.8 m (SD) by parentage analysis, and 18.6 m by modelling). Genetic structure was significant at short distances, and a clumped distribution of chloroplast microsatellite genotypes was seen in K. candel adults. We conclude that the K. candel population was initiated by limited propagule founders from outside by long-distance dispersal followed by limited propagule dispersal from the founders, resulting in a half-sib family structure. 相似文献
8.
Inferring process from pattern in plant invasions: a semimechanistic model incorporating propagule pressure and environmental factors 总被引:1,自引:0,他引:1
Propagule pressure is intuitively a key factor in biological invasions: increased availability of propagules increases the chances of establishment, persistence, naturalization, and invasion. The role of propagule pressure relative to disturbance and various environmental factors is, however, difficult to quantify. We explored the relative importance of factors driving invasions using detailed data on the distribution and percentage cover of alien tree species on South Africa's Agulhas Plain (2,160 km2). Classification trees based on geology, climate, land use, and topography adequately explained distribution but not abundance (canopy cover) of three widespread invasive species (Acacia cyclops, Acacia saligna, and Pinus pinaster). A semimechanistic model was then developed to quantify the roles of propagule pressure and environmental heterogeneity in structuring invasion patterns. The intensity of propagule pressure (approximated by the distance from putative invasion foci) was a much better predictor of canopy cover than any environmental factor that was considered. The influence of environmental factors was then assessed on the residuals of the first model to determine how propagule pressure interacts with environmental factors. The mediating effect of environmental factors was species specific. Models combining propagule pressure and environmental factors successfully predicted more than 70% of the variation in canopy cover for each species. 相似文献
9.
Martin Schmalholz Kristoffer Hylander Katherine Frego 《Biodiversity and Conservation》2011,20(12):2575-2596
The disturbance regime in mixed-wood forests of eastern Canada is characterized by both natural disturbances including wildfires
and insect outbreaks as well as forestry. The understanding of how understorey plant assemblages respond to different disturbances
is mostly limited to short-term wildfire-logging comparisons of vascular plants. Here, we compare patterns of species richness
and composition of four bryophyte guilds in young forests (approx. 40 years old) regenerating after clear-cut logging, wildfire,
and spruce budworm outbreak. In addition, young forests were compared with mature spruce-fir dominated stands (approx. 90 years
old). Although similar in overall species richness at the scale of 1,000 m2 all young forest types were compositionally distinct with fewer species than mature forests. Stands developed after spruce
budworm outbreaks had the highest canopy cover values and the highest surface area of coarse woody debris. These stands had
similar numbers of woody debris species as mature forests and were closest to mature forests in species composition. Wildfire-disturbed
sites were dominated by deciduous trees and a high number of treebase species. Finally, young managed forest had the highest
number of forest floor bryophytes at the scale of 100 m2 among the three young forest types, but was compositionally far from mature forests in their woody debris flora. In conclusion,
young forests regenerating after natural disturbances are distinctly different from young forests regenerated after clear-cutting
and if natural disturbances are eliminated certain species (e.g., epixylic and treebase species) might become more restricted
to older stands in the landscape. 相似文献
10.
Structural heterogeneity and tree spatial patterns in an old-growth deciduous lowland forest in Cantabria, northern Spain 总被引:3,自引:0,他引:3
Vicente Rozas 《Plant Ecology》2006,185(1):57-72
Old-growth deciduous forests in western Europe, for the most part, consist of small tracts that often may be atypical due to human disturbance, poor soil productivity or inaccessibility. In addition, very little information on tree age distributions, structural heterogeneity and tree spatial patterns appears to be available for west-European forests. Characterization of the structural features of tree populations in these old-growth stands can provide the basis to design conservation plans and also inform on how present forests might look in the absence of human interference. Four old-growth stands in a deciduous forest in the Cantabrian lowlands, northern Spain, were surveyed to determine forest structure and spatial patterns. Live and dead trees were identified, measured and mapped, and live trees were cored for age estimation. Structural heterogeneity was analyzed by means of the spatial autocorrelation of tree diameter, height and age, and the uni- and bivariate spatial patterns of trees were analyzed. The dominant species, Fagus sylvatica and Quercus robur, showed reverse-J shaped size distributions but discontinuous age distributions, with maximum ages of 255–270 yr. Tree ages suggested that the forest was largely modified by past changes in forest-use, especially by temporal variation in grazing intensity. Spatial autocorrelation revealed that former parkland stands were heterogeneous with respect to tree height only, while high forest stands were composed of patches of even-aged and even-sized trees. Young trees were clumped at varying distances and establishment occurred preferentially in canopy gaps, except for Ilex aquifolium that mainly occurred beneath mature Quercus trees. Surviving trees became less intensely clumped in the dominant species, and more strongly clumped in understorey ones, which may have been due to the effects of intraspecific competition and of canopy trees on tree survival, respectively. The spatial associations between species varied within the forest, probably as a consequence of specific establishment preferences and competitive interactions. 相似文献
11.
Jørn-Frode Nordbakken 《Nordic Journal of Botany》1996,16(2):197-209
The vegetation within an ombrotrophic mire expanse in SE Norway is studied in detail. Percentage cover of 45 species in 436 sample plots (16 ×16 cm), dispersed on 26 transects, are recorded. In addition, species abundance in 6976 subplots (4×4 cm) are recorded. 14 variables are recorded for each of the sample plots, while only distance to the water-table is estimated for the subplots. Spatial co-ordinates are supplied for all sample- and subplots. DCA ordination of a data-set consisting of 412 sample plots reveals two ecologically interpretable vegetational gradients: the hummock-hollow gradient (DCA 1), and a gradient associated with the peat-production of the bottom layer (DCA 2). Passive DCA of subplots is used to get an impression of within sample plot heterogeneity, and shows that the fine-scale compositional turnover may be considerable. Partitioning of the variation in species abundance data is done by use of (partial) CCA. The fraction of unexplained variation is rather large for all the tested data-sets, but within the total variation explained, both distance to the water-table and spatial structure explain large parts. 相似文献
12.
Intermediary disturbance increases tree diversity in riverine forest of southern Brazil 总被引:1,自引:0,他引:1
Jean Carlos Budke João André Jarenkow Ary Teixeira de Oliveira-Filho 《Biodiversity and Conservation》2010,19(8):2371-2387
Floods are frequently associated with disturbance in structuring riverine forests and they lead to environmental heterogeneity
over space and time. We evaluated the distribution of tree species, ecological groups, species richness and diversity from
the point bar to the slope of a riverside forest in southern Brazil (Lat. 30°01′S, Long. 52°47′W) to analyze the effects of
flooding on soil properties and forest structure. A plot of 50 × 200 m divided in five contiguous transects of 10 × 200 m
parallel to the river was installed, where we measured all the individual trees with pbh ≥ 15 cm. A detailed topographical
and soil survey was carried out across the plot and indicated significant differences in organic matter and most mineral nutrients
through the topographical gradient. The 1,229 surveyed individuals belonged to 72 species and 35 families. We used Partial
CCA and Species Indicator Analysis to observe the spatial distribution of species. Both analyses showed that species distribution
was strongly related to the flooding gradient, soil properties and also by space and pure spatial structuring of species and
environmental variables (spatial autocorrelation), although a large part of variation remains unexplained. The ecological
groups of forest stratification, plant dispersal and requirements for germination indicated slight differences among frequently,
occasional and non-flooded transects. Species richness and diversity were higher at intermediate elevations and were associated
to the increased spatial–temporal environmental heterogeneity. Across the plot, the direct influence of flooding on tree species
distribution created a vegetation zonation that is determined by predicted ecological traits. 相似文献
13.
Mizue Ohashi Tomo’omi Kumagai Tomonori Kume Koichiro Gyokusen Taku M. Saitoh Masakazu Suzuki 《Biogeochemistry》2008,90(3):275-289
Although soil carbon dioxide (CO2) efflux from tropical forests may play an important role in global carbon (C) balance, our knowledge of the fluctuations
and factors controlling soil CO2 efflux in the Asian tropics is still poor. This study characterizes the temporal and spatial variability in soil CO2 efflux in relation to temperature/moisture content and estimates annual efflux from the forest floor in an aseasonal intact
tropical rainforest in Sarawak, Malaysia. Soil CO2 efflux varied widely in space; the range of variation averaged 17.4 μmol m−2 s−1 in total. While most CO2 flux rates were under 10 μmol m−2 s−1, exceptionally high fluxes were observed sporadically at several sampling points. Semivariogram analysis revealed little
spatial dependence in soil CO2 efflux. Temperature explained nearly half of the spatial heterogeneity, but the effect varied with time. Seasonal variation
in CO2 efflux had no fixed pattern, but was significantly correlated with soil moisture content. The correlation coefficient with
soil moisture content (SMC) at 30 and 60 cm depth was higher than at 10 cm depths. The annual soil CO2 efflux, estimated from the relationship between CO2 efflux and SMC at 30 cm depth, was 165 mol m−2 year−1 (1,986 g C m−2 year−1). As this area is known to suffer severe drought every 4–5 years caused by the El Nino-Southern Oscillation, the results
suggest that an unpredictable dry period might affect soil CO2 efflux, leading an annual variation in soil C balance. 相似文献
14.
Spatial structural patterns emerging from local tree interactions influence growth, mortality and regeneration processes in forest ecosystems, and decoding them enhance the understanding of ecological mechanisms affecting forest regeneration. Point-Patterns analysis was applied for the very first time to mangrove ecology to explore the spatial structure of Rhizophora mucronata regeneration in a disturbed mangrove forest; and the pattern of associations of juvenile–adult trees. R. mucronata trees were mapped in plots of 50 m × 10 m located at the seaward, central and landward edge along 50 m wide transect in the forest, and the mapped patterns were analysed with pair correlation and mark-connection functions. The population density of R. mucronata differed along the tidal gradient with the highest density in the central region, and the least near the shoreline. The study revealed that short distance propagule dispersal, resulting in the establishment of juveniles in closed distance to the mother trees, might not be the driving force for distribution of this species. The spatial structural pattern of R. mucronata population along tidal gradient showed a characteristic spatial aggregation at small scale, but randomly distributed as the distances become larger. There was a distinct spatial segregation between recruits and adult trees, and hence spatially independent. Though, adult–adult trees associations did not show a clear spatial segregation pattern; the recruit–recruit species associations exhibited significant clustering in space. Although habitat heterogeneity might be responsible for the local scale aggregation in this population, the effect of plant–plant conspecific interactions is more probable to inform the long-term structure and dynamics of the population of R. mucronata, and ditto for the entire forest. 相似文献
15.
Pedro Beja Carlos David Santos Joana Santana Maria João Pereira J. Tiago Marques Hélder Lima Queiroz Jorge M. Palmeirim 《Biodiversity and Conservation》2010,19(1):129-152
We examined seasonal patterns of spatial variation in understory bird assemblages across a mosaic of upland and floodplain
forests in central Amazonia, where variation in flooding patterns and floodwater nutrient load shapes a marked spatial heterogeneity
in forest structure and composition. Despite great differences in productivity due to flooding by either nutrient-rich “white
waters” (várzea) or nutrient-poor “black waters” (igapó), bird assemblages in the two floodplain forest types were relatively
similar, showing lower abundances than adjacent upland forests (terra firme) and sharing a set of species that were absent
or scarce elsewhere. Species that breed in pensile nests overhanging water were abundant in floodplain forests, whereas species
that feed on the ground were generally scarce. Flooding affected assemblage dynamics in floodplain forests, with some influx
of ground-dwelling species such as ant-following birds from adjacent upland during the low-water season, and the occupation
by riverine and aquatic species such as kingfishers during floods. Spatial configuration influenced the seasonal pattern of
assemblage structuring, with movements from terra firme occurring primarily to adjacent igapó forests. No such influx was
detected in várzea forests that were farther from terra firme and isolated by wide river channels. Results support the view
that habitat heterogeneity created by flooding strongly contributes to maintain diverse vertebrate assemblages in Amazonia
forest landscapes, even in the case of largely sedentary species such as understory forest birds. Including both upland and
floodplain forests in Amazonia reserves may thus be essential to preserve bird diversity at the landscape scale. 相似文献
16.
Since inference concerning the relative effects of propagule pressure, biotic interactions, site conditions and species traits on the invasibility of plant communities is limited, we carried out a field experiment to study the role of these factors for absolute and relative seedling emergence in three resident and three non-resident confamilial herb species on a nutrient-poor temperate pasture. We set up a factorial field experiment with two levels each of the factors litter cover (0 and 400 g m(-2)), gap size (0.01 and 0.1 m(2)) and propagule pressure (5 and 50 seeds) and documented soil temperature, soil water content and relative light availability. Recruitment was recorded in spring and autumn 2010 and in spring 2011 to cover initial seedling emergence, establishment after summer drought and final establishment after the first winter. Litter alleviated temperature and moisture conditions and had positive effects on proportional and absolute seedling emergence during all phases of recruitment. Large gaps presented competition-free space with high light availability but showed higher temperature amplitudes and lower soil moisture. Proportional and absolute seedling recruitment was significantly higher in large than in small gaps. In contrast, propagule pressure facilitated absolute seedling emergence but had no effects on proportional emergence or the chance for successful colonisation. Despite significantly higher initial seedling emergence of resident than non-resident species, seed mass and other species-specific traits may be better predictors for idiosyncratic variation in seedling establishment than status. Our data support the fluctuating resource hypothesis and demonstrate that the reserve effect of seeds may facilitate seedling emergence. The direct comparison of propagule pressure with other environmental factors showed that propagule pressure affects absolute seedling abundance, which may be crucial for species that depend on other individuals for sexual reproduction. However, propagule batch size did not significantly affect the chance for successful colonisation of disturbed plots. 相似文献
17.
Variations in species richness and diversity at a local scale are affected by a number of complex and interacting variables,
including both natural environmental factors and human-made changes to the local environment. Here we identified the most
important determinants of woody species richness and diversity at different growth stages (i.e. adult, sapling and seedling)
in a bamboo–deciduous forest in northeast Thailand. A total of 20 environmental and human disturbance variables were used
to determine the variation in species richness and diversity. In total, we identified 125 adult, 111 sapling (within fifty
20 × 20-m plots) and 89 seedling species (within one hundred and twenty 1 × 1-m subplots). Overall results from stepwise multiple
regression analyses showed that environmental variables were by far the most important in explaining the variation in species
richness and diversity. Forest structure (i.e. number of bamboo clumps and canopy cover) was important in determining the
adult species richness and diversity (R
2 = 0.48, 0.30, respectively), while topography (i.e. elevation) and human disturbance (i.e. number of tree stumps) were important
in determining the sapling species richness and diversity (R
2 = 0.55, 0.39, respectively). Seedling species richness and diversity were negatively related to soil phosphorus. Based on
our results, we suggest that the presence of bamboos should be incorporated in management strategies for maintaining woody
species richness and diversity in these forest ecosystems. Specifically, if bamboos cover the forest floor at high densities,
it may be necessary to actively control these species for successful tree establishment. 相似文献
18.
Although strip clear-cutting has a long history of use in the temperate zone, it was only recently introduced for timber extraction
in tropical rain forests, where it is known as the Palcazú Forest Management System. In this system heterogeneous tropical
forests are managed for native gap-dependent timber species by simulating gap dynamics through clear-cutting long, narrow
strips every 40 years. As part of an assessment of the sustainability of this system, we evaluated the recovery of tree basal
area, species richness, and composition after 15 years of regeneration on two strips (30 × 150 m) clear-cut in 1989 in Jenaro
Herrera, Peru. Timber stocking and the effects of silvicultural thinning were assessed in both strips. The strips recovered
58–73% of their original basal area and 45–68% of their original tree species richness. Although both strips recovered more
than 50% of their original composition, commercial species had lower basal areas and lower densities than in the forest before
the clearing. Pioneer species with high basal areas remained dominant 15 years after the cutting. Silvicultural thinning in
1996 reduced the abundance of pioneer species in both strips, and increased the abundance of commercial species in one of
the strips. Half of one strip was harvested by deferment-cut (only commercial trees >30 cm dbh and “other” species >5 cm dbh
were cut); regeneration here had greater abundance of commercial species and lower abundance of pioneer species. The low stocking
of commercial trees challenges the sustainability claims for this forest management system. 相似文献
19.
Luciana F. Alves Marco A. Assis Juliano van Melis Ana L. S. Barros Simone A. Vieira Fernando R. Martins Luiz A. Martinelli Carlos A. Joly 《Ecological Research》2012,27(2):323-332
Lianas play a key role in forest structure, species diversity, as well as functional aspects of tropical forests. Although
the study of lianas in the tropics has increased dramatically in recent years, basic information on liana communities for
the Brazilian Atlantic Forest is still scarce. To understand general patterns of liana abundance and biomass along an elevational
gradient (0–1,100 m asl) of coastal Atlantic Forest, we carried out a standard census for lianas ≥1 cm in five 1-ha plots
distributed across different forest sites. On average, we found a twofold variation in liana abundance and biomass between
lowland and other forest types. Large lianas (≥10 cm) accounted for 26–35% of total liana biomass at lower elevations, but
they were not recorded in montane forests. Although the abundance of lianas displayed strong spatial structure at short distances,
the present local forest structure played a minor role structuring liana communities at the scale of 0.01 ha. Compared to
similar moist and wet Neotropical forests, lianas are slightly less abundant in the Atlantic Forest, but the total biomass
is similar. Our study highlights two important points: (1) despite some studies have shown the importance of small-scale canopy
disturbance and support availability, the spatial scale of the relationships between lianas and forest structure can vary
greatly among tropical forests; (2) our results add to the evidence that past canopy disturbance levels and minimum temperature
variation exert influence on the structure of liana communities in tropical moist forests, particularly along short and steep
elevational gradients. 相似文献
20.
Strong topographic variation interacting with low stature alpine vegetation creates a multitude of micro-habitats poorly represented
by common 2 m above the ground meteorological measurements (weather station data). However, the extent to which the actual
habitat temperatures in alpine landscapes deviate from meteorological data at different spatial scales has rarely been quantified.
In this study, we assessed thermal surface and soil conditions across topographically rich alpine landscapes by thermal imagery
and miniature data loggers from regional (2-km2) to plot (1-m2) scale. The data were used to quantify the effects of spatial sampling resolution on current micro-habitat distributions
and habitat loss due to climate warming scenarios. Soil temperatures showed substantial variation among slopes (2–3 K) dependent
on slope exposure, within slopes (3–4 K) due to micro-topography and within 1-m2 plots (1 K) as a result of plant cover effects. A reduction of spatial sampling resolution from 1 × 1 m to 100 × 100 m leads
to an underestimation of current habitat diversity by 25% and predicts a six-times higher habitat loss in a 2-K warming scenario.
Our results demonstrate that weather station data are unable to reflect the complex thermal patterns of aerodynamically decoupled
alpine vegetation at the investigated scales. Thus, the use of interpolated weather station data to describe alpine life conditions
without considering the micro-topographically induced thermal mosaic might lead to misinterpretation and inaccurate prediction. 相似文献