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1.
This study investigates the use of aquatic macrophytes as indicators of stream condition in catchments with varied land use and levels of riparian disturbance in the Wet Tropics region of North Queensland (Australia), a region of global significance in terms of faunal and floral diversity. In a paired catchment design spatial variations in macrophyte assemblage structure were characterised using multivariate and univariate techniques. Seven metrics were trialled: total macrophyte cover, species richness, % alien taxa, % native taxa, % submerged taxa, % emergent taxa and % Poaceae. Forty-four macrophyte taxa were recorded from the study area. Poaceae, Cyperaceae and mosses were the most frequently recorded taxa. Upper catchment areas in all tributaries surveyed were dominated by mosses and Cladopus queenslandicus (Domin) C.D.K. Cook (Podestemaceae). This assemblage occurred in areas with intact riparian canopy cover and good overall riparian condition. Macrophyte assemblages in lower catchment areas were distributed along gradients of riparian disturbance. Simultaneous autoregression model coefficients indicated that riparian condition had a negative influence on macrophyte cover, species richness and the proportions of alien taxa, emergent taxa and Poaceae present at sites in the Wet Tropics. Macrophyte metrics were not strongly influenced by the types of land use or water quality. These findings suggest that a riparian condition assessment would provide an adequate first assessment of the state of aquatic macrophyte assemblages in Wet Tropics streams.  相似文献   

2.
Close correlations in species numbers may make it possible to indirectly assess the species richness of difficult taxonomic groups by investigating indicator groups, for which data are more easily collected. We asked if species numbers correlate among the four dominating groups of primary producers in boreal forests (liverworts, macrolichens, mosses, and vascular plants) and if substrate affiliation of species (ground vs. other substrates), sample plot size (0.01–1000 m2), and stand age (young vs. old) influence correlation strength. We used three sets of study plots from northern Sweden each including wide ranges of species richness. Although there are large differences in the ecophysiology and substrate use of vascular plants and the two bryophyte groups (mosses and liverworts), we found strong positive correlations among them not previously reported from boreal forests. In contrast, no correlation in total species richness was found between macrolichens and the two bryophyte groups, despite large overlaps in their ecology. We suggest that the positive correlations among land plants (liverworts, mosses, and vascular plants) are linked to positive relationships between site moisture and species number for all three groups. In contrast, total species number of macrolichens has not been shown to be strongly associated with moisture. However, ground‐living lichens and mosses correlated negatively in old forests. This may relate to the inability of macrolichens to exploit shaded and wet old forest ground, a habitat that is used by many moss species. Furthermore, lichens and mosses of ‘other substrates’ correlated positively in old forests, probably because the amount of boulders was positively related to species richness in both groups. Generally, correlations became stronger with increasing plot size, whereas stand age had relatively little influence. We conclude that vascular plants could be used as an indicator group for species richness of mosses and liverworts in boreal landscapes.  相似文献   

3.
Aim To explore species richness patterns in liverworts and mosses along a central Himalayan altitudinal gradient in Nepal (100–5500 m a.s.l.) and to compare these patterns with patterns observed for ferns and flowering plants. We also evaluate the potential importance of Rapoport’s elevational rule in explaining the observed richness patterns for liverworts and mosses. Location Nepal, Central Himalaya. Methods We used published data on the altitudinal ranges of over 840 Nepalese mosses and liverworts to interpolate presence between maximum and minimum recorded elevations, thereby giving estimates of species richness for 100‐m altitudinal bands. These were compared with previously published patterns for ferns and flowering plants, derived in the same way. Rapoport’s elevational rule was assessed by correlation analyses and the statistical significance of the observed correlations was evaluated by Monte Carlo simulations. Results There are strong correlations between richness of the four groups of plants. A humped, unimodal relationship between species richness and altitude was observed for both liverworts and mosses, with maximum richness at 2800 m and 2500 m, respectively. These peaks contrast with the richness peak of ferns at 1900 m and of vascular plants, which have a plateau in species richness between 1500 and 2500 m. Endemic liverworts have their maximum richness at 3300 m, whereas non‐endemic liverworts show their maximum richness at 2700 m. The proportion of endemic species is highest at about 4250 m. There is no support from Nepalese mosses for Rapoport’s elevational rule. Despite a high correlation between altitude and elevational range for Nepalese liverworts, results from null simulation models suggest that no clear conclusions can be made about whether liverworts support Rapoport’s elevational rule. Main conclusions Different demands for climatic variables such as available energy and water may be the main reason for the differences between the observed patterns for the four plant groups. The mid‐domain effect may explain part of the observed pattern in moss and liverwort richness but it probably only works as a modifier of the main underlying relationship between climate and species richness.  相似文献   

4.
5.
We present a first comparison of patterns of alpha and beta diversity of ferns, mosses, liverworts and macrolichens in neotropical montane rainforests, and explore the question whether specific taxa may be used as surrogates for others. In three localities in southern Ecuador, we surveyed terrestrial and epiphytic species assemblages in ridge and slope forests in 28 plots of 400 m2 each. The epiphytic habitat was significantly richer in ferns, liverworts, and macrolichens than the terrestrial habitat; mosses, however, were primarily terrestrial. Alpha diversity of ferns and of liverworts was congruent in both habitats. Mosses were similar to ferns and liverworts only in the epiphytic habitat. Macrolichens did not share patterns of alpha diversity with any other group. Beta diversity of ferns, mosses and liverworts (lichens excluded due to low species richness) was similar in the terrestrial habitat, but not in the epiphytic habitat. Our results demonstrate that patterns of alpha diversity of the studied taxa cannot be used to predict patterns of beta diversity. Moreover, diversity patterns observed in epiphytes are different from terrestrial plants. We noted a general coincidence in species patterns of liverworts and ferns. Diversity patterns of macrolichens, in contrast, were completely independent from any other taxonomic group studied.  相似文献   

6.
7.
Questions: Boreal forests along small streams are bryophyte diversity hotspots because they are moist, productive and relatively high pH. Do these factors also explain the large differences in species richness and species composition found among streamside sites? Do the species of species‐poor sites represent nested subsets of the species of more species‐rich sites? How do the results apply to conservation? Location: Forests along small streams in mid‐boreal Sweden. Methods: Survey of the flora of liverworts and mosses and habitat properties, including calculation of a pH‐index based on species indicator values, in 37 sites (1000‐m2 plots). Results: The number of bryophyte species per plot ranged from 34 to 125. Neither soil moisture nor basal area of trees (a proxy for productivity) correlated significantly with species richness and composition, whereas pH‐index and cover of boulders did. Species richness and composition were more strongly correlated with pH‐index for mosses than for liverworts. The richness and composition of bryophyte species most frequently found on moist ground, stream channel margins and, most unexpected, woody debris were all more strongly associated with the pH‐index than with other habitat properties. Although species composition was significantly nested, there was still some turnover of species along the first ordination axis. Conclusions To attain high numbers of species, streamside forests need to have boulders and at least pockets with higher soil and stream‐water pH. The number of Red list species was weakly correlated with total species richness and the most species‐rich sites contained many species found more in non‐forest habitats. Hence, bryophyte conservation in streamside forests should not focus on species‐rich sites but on the quality and quantity of substrate available for assemblages of forest species that are strongly disfavoured by forestry.  相似文献   

8.
We studied the effects of patch retention felling and soil scarification by harrowing on the coverage and species richness of epixylic species in boreal Norway spruce (Picea abies) forests in Southern Finland. The epixylics were investigated from both the retention tree groups (RTGs) and the surrounding felling areas before and after fellings and after scarification on consecutive years. The cover percentage of all included species groups was shown to decrease after the felling, especially in the felling areas (vascular plants, ?0.4%; mosses, ?27.8%; liverworts, ?4.0%; and lichens,?2.1%). The decrease was considerable also in the RTGs. The amount of dead moss increased in both the areas indicating microclimatic changes. Species richness also declined rapidly after the first year, especially in the felling areas (vascular plants, ?2.2%; mosses, ?27.3%; liverworts, ?30.3%; and lichens, ?22.9%). Scarification also decreases covers and species richness of bryophytes. After the second year, the covers of the species groups generally started to regain, especially in the untreated RTGs. The size of RTG was in positive correlation with the total species number. Another main result indicates that it is possible to maintain much higher initial vegetation abundance and diversity in the RTGs than in the felling areas. Coarse woody debris formed by the frequent tree uprootings may also enhance the long‐term survival of epixylics over forest regeneration period. RTGs should be at least 10 times larger than the size used in current Finnish forestry, so that they could function as species refugia.  相似文献   

9.
Riparian ecosystems have unique biodiversity, are highly sensitive to disturbance and anthropogenic influence. As world water resources become scarcer, scientists predict greater competition among species for water resources. Indeed, increased encroachment of upland plants into the riparian zone is already occurring, irreversibly changing riparian plant communities. Since semi-arid regions such as Mediterranean-type ecosystems are likely to follow this same trajectory, assessing the contributions of riparian versus upland (sclerophyllous) plants to community composition is important. A survey of seventy 2 km-long riparian transects on the Sado and Guadiana watersheds in southern Portugal assessed (1) the woody riparian plant community composition, (2) how much richness is due to strictly riparian plants versus sclerophyllous upland plants, and (3) which combinations of biotic and abiotic factors allow higher species richness in the strictly riparian, sclerophyllous, and overall plant communities. The survey detected 53 different woody plant species (28 endemic) across all communities. Riparian community richness was on average 16 species, seven of which were strictly riparian and the remainder being sclerophyllous, exotic species or fruit trees. Sclerophyllous plant species occurred consistently across sampling units (90% of transects). On average, 46% of the total woody plant community richness was due to strictly riparian plants and 28% was due to sclerophyllous plants. Community richness was positively affected by the area of shrubs in the riparian zone and by the absence of human activities and goats. Surrounding landscape pattern only affected the strictly riparian plant richness. These results suggest that natural and human-mediated disturbances in riparian ecosystems create gaps and clearings for which riparian and sclerophyllous plants compete. Establishment success seems to be related to the propagule pressure of the neighbouring landscape, its diversity and density, as well as the presence of herbivores. Preserving strictly riparian plants, removing exotic species, preventing grazing, and promoting riparian values (recreation, aesthetics and the provision of ecosystem services) will aid the future conservation of the unique biodiversity of riparian ecosystems.  相似文献   

10.
Due to ongoing global changes, it is essential to establish a baseline record from which to determine future shifts in species distributions and community assembly patterns. In this context, we used digitised historical bryophyte distribution data along a 1021?m elevational gradient in Terceira Island (Azores) to determine how bryophyte species distribution varies with elevation and which spatial and climatic drivers contribute to this variation. We used ordinary least squares analysis to test for climatic and spatial data as explanatory variables for bryophyte richness and Mid-Domain Null simulations to assess the influence of spatial constraints on species distributions. Bryophyte richness follows a hump-shaped pattern, with mosses predominating in the first half of the gradient and liverworts in the second half. While moss richness did not correlate to any climatic variables and responded weakly to the presence of forest cover, liverwort presence was related to temperature, rainfall, humidity and the occurrence of native forest areas, suggesting that these plants are more sensitive to changes in their environment and can thus be used as better indicator species for climate change. Despite their inherent biases, our study shows that historically compiled data can be a valuable tool for preliminary assessment of macroecological patterns.  相似文献   

11.
Swan CM  Palmer MA 《Oecologia》2006,147(3):469-478
Leaf litter derived from riparian trees can control secondary production of detritivores in forested streams. Species-rich assemblages of leaf litter reflect riparian plant species richness and represent a heterogeneous resource for stream consumers. Such variation in resource quality may alter consumer growth and thus the feedback on leaf breakdown rate via changes in feeding activity. To assess the consequences of this type of resource heterogeneity on both consumer growth and subsequent litter breakdown, we performed a laboratory experiment where we offered a leaf-shredding stream detritivore (the stonefly Tallaperla maria, Peltoperlidae) ten treatments of either single- or mixed-species leaf litter. We measured consumer growth rate, breakdown rate and feeding activity both with and without consumers for each treatment and showed that all three variables responded to speciose leaf litter. However, the number of leaf species was not responsible for these results, but leaf species composition explained the apparent non-additive effects. T. maria growth responded both positively and negatively to litter composition, and growth on mixed-litter could not always be predicted by averaging estimates of growth in single-species treatments. Furthermore, breakdown and feeding rates in mixed litter treatments could not always be predicted from estimates of single-species rates. Given that species richness and composition of senesced leaves in streams reflects riparian plant species richness, in-stream secondary production of detritivores and organic matter dynamics may be related to species loss of trees in the riparian zone. Loss of key species may be more critical to maintaining such processes than species richness per se.  相似文献   

12.
Habitat degradation through agricultural land use is the major factor threatening lotic ecosystems. Although black flies are major components of these ecosystems, the impact of agricultural land use on species diversity and species assemblages has been largely ignored in tropical streams of the Oriental region. The objectives of this study are to examine patterns of species distribution and species richness and to compare black fly species richness and species assemblages in forest and agricultural streams in Thailand. A total of 143 collections were made from 70 stream sites between June 2007 and May 2008. Whereas 19 black fly species found in these collections were all found in forest sites, only 13 species were found in agricultural sites. High species richness was associated with larger, faster, and cooler streams with larger streambed particles and the presence of riparian trees. Logistic regression analyses revealed that stream size, velocity, and riparian vegetation are among the most important factors determining patterns of spatial distribution. The results are largely consistent with studies in other zoogeographic regions, suggesting the existence of general rules for black fly species distributions. Comparisons of the physicochemical conditions between forest and agricultural streams indicated that streams in agricultural areas are warmer, with higher conductivity and fewer riparian trees. Species richness was significantly higher in forest than in agricultural streams (t = 3.61, P < 0.001). Streams in forest areas were predominantly occupied by S. siamense (73%) but other species were also found at a relatively high frequency (>20%) of the sampling sites. In contrast, streams in agricultural areas were predominantly occupied by S. aureohirtum (>80%) among the sole black fly species at 27% of the sites. The results indicate that agricultural land use has a significantly detrimental impact on black fly diversity and species assemblages. Handling editor: D. Dudgeon  相似文献   

13.
《Fungal biology》2022,126(10):631-639
The fungi associated with leaf litter play a key role in decomposition and can be affected both by the warming water and the invasion of non-native species in riparian vegetation. Warming water and invasion of non-native riparian species on stream fungal communities have been studied mainly in temperate ecosystems. We tested the effects of warming water and non-native plant Psidium guajava on leaf litter decomposition, conidia density, species richness and beta diversity of tropical stream fungi. Thus, we carried out an experiment using the current mean temperature of streams from northwestern Paraná in South Brazil (22 °C) and two temperatures above the current mean temperature (26 °C and 29 °C). We also used the leaves of a non-native plant (P. guajava), and two native plants (one of similar nutritional quality, and the other of higher nutritional quality than the non-native species) occurring in Neotropical streams riparian vegetation. Warming water accelerated leaf litter decomposition and reduced conidia density and fungal richness in native and non-native plants. However, species composition and beta diversity were not affected by water temperature. Our study showed that warming affects the fungi of streams, the main microorganisms responsible for decomposition and that the nutritional quality of the leaves may be more important than the origin of riparian plant species. Despite this, further investigations should be conducted on the interaction of P. guajava with the flow of nutrients in these environments and how it can affect other ecosystem processes and the food chain. Efforts to study the effects of water warming and biological invasion on the attributes and distribution of fungi in streams are vital, making them a tool for the conservation of riparian ecosystems.  相似文献   

14.
Macrophytes are an important component of aquatic ecosystems and are used widely within the Water Framework Directive (WFD) to establish ecological quality. In the present paper we investigated macrophyte community structure, i.e., composition, richness and diversity measures in 60 unimpacted stream and river sites throughout Europe. The objectives were to describe assemblage patterns in different types of streams and to assess the variability in various structural and ecological metrics within these types to provide a basis for an evaluation of their suitability in ecological quality assessment. Macrophyte assemblage patterns varied considerably among the main stream types. Moving from small-sized, shallow mountain streams to medium-sized, lowland streams there was a clear transition in species richness, diversity and community structure. There was especially a shift from a predominance of species-poor mosses and communities dominated by liverwort in the small-sized, shallow mountain streams to more species-rich communities dominated by vascular plants in the medium-sized, lowland streams. The macrophyte communities responded to most of the features underlying the typological framework defined in WFD. The present interpretation of the WFD typology may not, however, be adequate for an evaluation of stream quality based on macrophytes. First and most important, by using this typology we may overlook an important community type, which is characteristic of small-sized, relatively steep-gradient streams that are an intermediate type between the small-sized, shallow mountain streams and the medium-sized, lowland streams. Second, the variability in most of the calculated metrics was slightly higher when using the pre-defined typology. The consistency of these results should be investigated by analysing a larger number of sites. Particularly the need of re-defining the typology to improve the ability to detect impacts on streams and rivers from macrophyte assemblage patterns should be investigated. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.  相似文献   

15.
Describing spatial variation in species richness and understanding its links to ecological mechanisms are complementary approaches for explaining geographical patterns of richness. The study of elevational gradients holds enormous potential for understanding the factors underlying global diversity. This paper investigates the pattern of species richness and range-size distribution of epiphytic bryophytes along an elevational gradient in Marojejy National Park, northeast Madagascar. The main objectives are to describe bryophyte species composition and endemism in Marojejy National Park, to describe the species richness and distribution patterns of epiphytic bryophytes along an elevational gradient from 250 m to 2050 m and to evaluate the explanatory value of environmental variables for the observed patterns. Bryophyte samples were collected following a nested design with four hierarchical levels: elevational belts, plots, quadrats, and microplots. In total, 254 epiphytic bryophyte species were recorded, comprising 157 liverworts and 97 mosses. Twenty-three of these are endemic to Madagascar. Species richness exhibits a hump-shaped pattern along the elevational gradient, peaking at 1,250 m. Eighty-seven percent of the total recorded species have a range distribution lower than 1,000 m, at which point 36% are restricted to these single elevations. Our results suggest that mean temperature, relative humidity, and vapor pressure deficit play important roles in shaping the richness pattern observed in this study. While the liverwort richness pattern did not correlate to vapor pressure deficit and responded only weakly to relative humidity, the richness pattern shown by mosses correlates well with mean temperature, relative humidity, and vapor pressure deficit.  相似文献   

16.
Hood  W. Gregory  Naiman  Robert J. 《Plant Ecology》2000,148(1):105-114
We compared the invasibility of riparian plant communities high on river banks with those on floodplain floors for four South African rivers. Analyses of abundant and significant riparian species showed that the floors have 3.1 times more exotic plants than the banks. The percent exotics ranges from 5% to 11% of total species richness for the banks, and from 20% to 30% for the floors. Species richness and percent exotics are negatively correlated for the banks, but not correlated for the floors.Despite great differences in climate, species richness, and landuse history, the percentages of exotic plants in three rivers in the Pacific Northwest of the USA and one river in southwestern France are similar to those in South Africa (24-30% vs. 20-30%, respectively). Furthermore, the high proportions of exotic species in these riparian plant communities are comparable to those reported for vascular plant communities on islands. We conclude that the macro-channel floor regions of the riparian zones of South African rivers are highly vulnerable to invasion by exotic vascular plants.  相似文献   

17.
18.
Spatial and temporal patterns of species richness in a riparian landscape   总被引:6,自引:0,他引:6  
Aim To test for control of vascular plant species richness in the riparian corridor by exploring three contrasting (although not mutually exclusive) hypotheses: (1) longitudinal patterns in riparian plant species richness are governed by local, river‐related processes independent of the regional species richness, (2) riparian plant species richness is controlled by dispersal along the river (longitudinal control), and (3) the variation in riparian plant species richness mirrors variation in regional richness (lateral control). Location The riparian zones of the free‐flowing Vindel River and its surrounding river valley, northern Sweden. Methods We used data from three surveys, undertaken at 10‐year intervals, of riparian reaches (200‐m stretches of riverbank) spanning the entire river. In addition, we surveyed species richness of vascular plants in the uplands adjacent to the river in 3.75‐km2 large plots along the same regional gradient. We explored the relationship between riparian and upland flora, and various environmental variables. We also evaluated temporal variation in downstream patterns of the riparian flora. Results Our results suggest that local species richness in boreal rivers is mainly a result of local, river‐related processes and dispersal along the corridor. The strongest correlation between species richness and the environment was a negative one between species number and soil pH, but pH varied within a narrow range. We did not find evidence for a correlation between species richness on regional and local scales. We found that the local patterns of species richness for naturally occurring vascular plants were temporally variable, probably in response to large‐scale disturbance caused by extreme floods. Most previous studies have found a unimodal pattern of species richness with peaks in the middle reaches of a river. In contrast, on two of three occasions corresponding to major flooding events, we found that the distribution of species richness of naturally occurring vascular plants resembled that of regional diversity: a monotonic decrease from headwater to coast. We also found high floristic similarity between the riparian corridor and the surrounding landscape. Main conclusions These results suggest that local processes control patterns of riparian species richness, but that species composition is also highly dependent on the regional species pool. We argue that inter‐annual variation in flood disturbance is probably the most important factor producing temporal variability of longitudinal species richness patterns.  相似文献   

19.
1. Urbanisation severely affects stream hydrology, biotic integrity and water quality, but relatively little is known about effects on organic matter dynamics. Coarse particulate organic matter (CPOM) is a source of energy and nutrients in aquatic systems, and its availability has implications for ecosystem productivity and aquatic communities. In undisturbed environments, allochthonous inputs from riparian zones provide critical energy subsidies, but the extent to which this occurs in urbanised streams is poorly understood. 2. We investigated CPOM inputs, standing stocks, retention rates and retention mechanisms in urban and peri‐urban streams in Melbourne, Australia. Six streams were chosen along a gradient of catchment urbanisation, with the presence of reach scale riparian canopy cover as a second factor. CPOM retention was assessed at baseflow via replicate releases of marked Eucalyptus leaves where the retention distance and mechanism were recorded. CPOM and small wood (>1 cm diameter) storage were measured via cores and direct counts, respectively, while lateral and horizontal CPOM inputs were assessed using riparian litter traps. Stream discharge, velocity, depth and width were also measured. 3. CPOM inputs were not correlated with urbanisation, but were significantly higher in ‘closed’ canopy reaches. Urbanisation and riparian cover altered CPOM retention mechanisms, but not retention distances. Urban streams showed greater retention by rocks; while in less urban streams, retention by small wood was considerably higher. CPOM and small wood storage were significantly lower in more urban streams, but we found only a weak effect of riparian cover. 4. These findings suggest that while riparian vegetation increases CPOM inputs and has modest/weak effects on storage, catchment scale urbanisation decreases organic matter availability. Using an organic matter budget approach, it appears likely that the increased frequency and magnitude of high flows associated with catchment urbanisation exerts an overriding influence on organic matter availability. 5. We conclude that to maintain both organic matter inputs and storage, the restoration and protection of streams in urban or rapidly urbanising environments relies on the management of both riparian vegetation and catchment hydrology.  相似文献   

20.
1. Effects of the frequency and duration of flooding on the structural and functional characteristics of riparian vegetation were studied at four sites (n = 80, 50 × 50 cm, plots) along medium‐sized naturally meandering lowland streams. Special focus was on rich fens, which – due to their high species richness – are of high priority in nature conservation. 2. Reed beds, rich fens and meadows were all regularly flooded during the 20‐year study period, with a higher frequency in reed bed areas than in rich fen and meadow areas. In rich fens, species richness was higher in low frequency flooded areas (≤3 year?1) than in areas with a high frequency of flooding (>3 year?1) or no flooding, whereas species richness in reed beds and meadows was unaffected by flood frequency. 3. The percentage of stress‐tolerant species was higher in low intensity flooded rich fen areas than in high intensity and non‐flooded areas, indicating that the higher species richness in low frequency flooded rich fens was caused by competitive release. We found no indication that increased productivity was associated with high flooding frequencies. 4. We conclude that the restoration of morphological features in stream channels to increase the flooding regime can be beneficial for protected vegetation within riparian areas, but also that groundwater discharge thresholds and critical levels for protected vegetation should be identified and considered when introducing stream ecosystem restoration plans.  相似文献   

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