Bryophyte Species Diversity in Secondary Forests Dominated by the Introduced Species Spathodea campanulata Beauv. in Puerto Rico

The introduced tree species Spathodea campanulata (Bignoniaceae) forms novel forests in Puerto Rico, these having emerged after the abandonment of fields in the mid‐20th century and resulting in forests with a new species composition. We assessed bryophyte species richness in these novel forests and sought correlations with geological substrate, past land use, forest edge and patch area, forest structure, elevation, microhabitat diversity, tree species richness, and microclimatic conditions. Transects were established (edge and forest interior) in nine moist forest patches dominated by Spathodea in north‐central Puerto Rico. These Spathodea forest patches ranged from 0.6 to 9 ha. ANOVA, Chi‐square, correlation, and cluster analyses were used in data analyses. We found 57 bryophyte species. There was a significant difference in bryophyte richness among patches. Those on karst exhibited highest bryophyte richness due to microhabitat diversity, past land use, and shorter hydroperiods. Alluvial sites scored lowest in bryophyte species richness, and forest structure was important for bryophyte communities on these sites. Significant differences in temperature, relative humidity, and light intensity were observed between edge and forest interior. These appeared important for establishing bryophyte species cover but not richness and composition. Microhabitat diversity, patch area, and forest age were more related to bryophyte species richness than elevation, exposed edge, and tree species richness, regardless of geologic substrate. Collectively, Spathodea patches were similar to mature forests on the Island with respect to bryophyte species richness and composition. Novel Spathodea forests have conservation value due to their habitat suitability for bryophyte communities.     

Effects of environmental heterogeneity on species diversity and composition of terrestrial bryophyte assemblages in tropical montane forests of southern Ecuador

Background: Most studies on tropical bryophytes deal with epiphytic species. This is the first ecological study of tropical forests that focuses specifically on terrestrial bryophytes.

Aim: To investigate the differences between slope and ridge environments in upper montane forests of southern Ecuador in terms of species diversity (richness, abundance), species composition and life forms of terrestrial bryophytes.

Methods: We used Non-metric Multidimensional Scaling (NMDS) to group bryophyte relevés by study location, habitat type and exposure class. Species indicator values were calculated and compared for different habitats.

Results: In total, 140 species were recorded, the majority being liverworts. NMDS analyses and Mantel correlations clearly separated between slope and ridge relevés, and between sunny and shaded microhabitats on ridges. Bryophyte life forms also showed different distribution patterns in slope and in ridge habitats. Mosses were more prominent in sunny than in shaded microhabitats.

Conclusions: Environmental differentiation between ridges and slopes, and small-scale variation in microclimatic conditions caused by differences in exposure, were stronger predictors of species richness and composition than geographical distance between study sites.     

Report of the Alpine Section

Background: Under climate-change scenarios, rock outcrops, by providing microclimatically diverse habitats, different from those of surrounding zonal vegetation matrix, may serve as climatic refugia and thereby facilitate the persistence of specialist species.

Aim: We tested whether rock outcrops of southern temperate latitudes could act as local refugia for a cold-adapted flora in the face of global warming.

Methods: We related species composition of 50 outcrops and that of their surrounding vegetation to climatic data at local and regional scales to establish whether species distributions reflected differences that could indicate the existence of climatic refugia.

Results: While at a regional scale, species composition of the outcrops across the study area was related to mean annual precipitation and mean annual maximum temperature, locally, southern faces of outcrops had different species and lower maximum temperatures than insolated north faces and surrounding vegetation plots.

Conclusions: South faces of outcrops by providing cool microhabitats, and currently harbouring species not found in the surrounding zonal vegetation matrix, could serve as local refugia for heat-intolerant plants and other microthermic organism. The degree of ‘stability’ of these refugia will depend on the degree of future change in climate. Therefore, it is important to plan protected area networks that maximise local environmental heterogeneity, including the protection of rock outcrops both as refugia for cold-adapted species and as potential stepping stones that would allow dispersal of these species between supportive environments through unfavourable ones.     

Determinants of stream bryophyte community structure: bringing ecology into conservation

相似文献   

Microhabitat determines how grazing affects bryophytes in wood-pastures

Wood-pastures are biodiverse biotopes where livestock graze among trees. The diversity of several species groups is related to the structural diversity created by herbivores and by trees, decaying wood and rocks. One of the greatest threats to wood-pastures is abandonment that results in decreased heterogeneity of soil microhabitats as well as encroachment by young trees. We studied the diversity of bryophytes on different microhabitat types (soil, rocks, trees and decaying wood) in grazed and abandoned boreal wood-pastures (48 sites). Most species grew on soil, rocks or both. For both soil and rocks currently grazed sites had higher bryophyte species richness and several individual species also preferred grazed sites over abandoned sites. The grazers increase biodiversity by creating patches of bare soil and exposed rock surfaces. Currently grazed and abandoned sites did not differ significantly in bryophyte species richness on decaying wood or trees, and the overall bryophyte richness on these substrates was quite low due to the scarcity of dead wood and large living deciduous trees with suitable bark conditions. Rare species were observed on all microhabitats, most abundantly on soil and decaying wood. Especially our result on higher richness on rock surfaces shows the complexity of grazing effects on biodiversity. Grazers may affect the biodiversity of a species group that is not consumed by them, on a surface which is not attractive to them. These unobvious interactions should be recalled when planning wood-pasture management and conservation.     

Bryophyte diversity and distribution along an altitudinal gradient on a lava flow in La Réunion

Non‐vascular plant distribution patterns were examined in three microhabitats along an altitudinal gradient on a recent lava flow of the Piton de la Fournaise volcano (La Réunion, Mascarene archipelago). The uniform nature of the lava flow provides an excellent system to study the relationship between altitude and species diversity and distribution, and at the same time avoiding confusing multiple effects of substrate and vegetation heterogeneity. Non‐vascular plants were surveyed with quadrats within an altitudinal range from 250 m to 850 m a.s.l. Fine‐scale variations in bryophyte communities between three ecological microhabitats (the ground and on the rachises of two fern species) were investigated. Three specific questions were addressed: (1) What is the species diversity of bryophyte communities on a 19‐year‐old lava flow? (2) How does altitude influence the diversity and distribution of bryophytes on a lava flow? (3) Does microhabitat variation control bryophyte diversity? In our study, bryophyte diversity increased with altitude. Unexpectedly, species richness was very high; 70 species of bryophytes were recorded including nine new records for the island. Diversity was also controlled by ecological microhabitats. Bryophyte species were structured into six categories according to altitude and microhabitat preferences. Results suggested that the high diversity of these cryptic organisms on this lava flow is fostered in part by their host substrate and their adaptative strategies on new substrates. On a broader scale, it was concluded that lava flows as primary mineral environments are important to conserve, as they support a high diversity of pioneer organisms that constitute the early stages of the development of La Réunion's remnant lowland rainforest.     

Bryophyte diversity and community structure on thatched roofs of the Holnicote Estate,Somerset, U.K.

Abstract

We investigated patterns of bryophyte species richness and community structure, and their relation to roof variables, on thatched roofs of the Holnicote Estate, South Somerset. Thirty-two bryophyte species were recorded from 28 sampled roofs, including the globally rare and endangered thatch moss, Leptodontium gemmascens. Multiple regression analyses revealed that thatch age has a highly significant positive effect on the number of species present, accounting for nearly half the observed variation in species richness after removal of outliers. Aspect has a slight and marginally significant effect on species diversity (accounting for an additional 6% of variation), with north-facing samples having slightly more species. Age also has a significant impact on total bryophyte cover after removal of outlying observations. TWINSPAN analysis of bryophyte cover data suggests the existence of at least five discrete communities. Simple Discriminant Analyses indicate that these communities occupy different ecological subspaces as defined by the measured roof variables, with pitch, aspect and thatch age emerging as especially significant attributes. Contingency Analysis indicates that some communities are disfavoured by water reed as compared to wheat straw. The findings are significant for understanding the structure of bryophyte communities, for evaluating the effect of bryophyte cover on thatch performance, and for conservation of thatch communities, especially those harbouring rare species.     

Functional diversity and composition of bryophyte water-related traits in Azorean native vegetation

Background: Functional trait-based approaches link species diversity patterns to ecosystem functioning. In the context of global change, understanding these links is vital for developing holistic biodiversity management strategies. Bryophytes, important ecosystem components owing to their biogeochemical functions, have not been the focus of many functional studies.

Aims: This is the first assessment of bryophyte functional diversity in the Azores archipelago, aiming to uncover multivariate trait richness and composition patterns along the elevational gradient on Terceira Island.

Methods: Based on five water acquisition and retention traits of leafy liverworts and mosses, we calculated functional diversity metrics within and among six bryophyte communities sampled along a 1021-m elevational transect.

Results: Trait composition differed significantly between coastal and mountain communities. Mosses presented inrolled leaves and ornamented leaf cells at low elevation but not at high elevation. These patterns were associated with an uphill shift from drier and warmer conditions to a moister and cooler environment.

Conclusions: Future climatic changes might affect bryophyte functional diversity patterns in Terceira Island, particularly for mosses. These results can be directly compared with those obtained for other archipelagos where the same protocol has been applied, allowing a joint assessment of insular vegetation functional diversity patterns.     

Plant communities on ironstone outcrops: a diverse and endangered Brazilian ecosystem

Mountain areas are recognized centres of endemism and diversity on account of their isolation and altitudinal diversity. In tropical regions, mountain tops usually stand as islands of xeric vegetation among mesophytic assemblages. Unlike the vegetation growing on other rock outcrops lithologies, such as inselbergs (granite/gneiss) or campos rupestres (quartz/arenite), ironstone outcrop plant communities still lack systematic studies in Brazil. These outcrops (locally known as canga) share most of the characteristics of other rock outcrops, such as isolation and edapho-climatic harshness, but differ in that they are the object of opencast mining, and thus subjected to irrecoverable degradation. In addition, they are expected to harbour metal-tolerant and hyperaccumulator plant species. A botanical survey of two ironstone outcrop locations in the most important mining region of southeastern Brazil, the Iron Quadrangle, revealed a high within-site (138 and 160 species per site), and between-site diversity (only 27% of common species), totaling 64 families and 234 species among basal families and eudicots (154 species), monocots (68 species), and ferns (12 species). Canga crusts are rich in dicots, several of which play an important role in community structuring, together with the more usual monocot aggregations. Distinct plant communities are found associated to different microhabitats within the iron crust, depending primarily on the amount of soil and moisture retention in the different microtopographies. The environmental uniqueness, high diversity, lack of studies and rapid destruction of these ecosystems pose an immediate challenge for their conservation.     

Detecting impacts of non‐native species on associated invertebrate assemblages depends on microhabitat

Invasive plants that displace native floral communities can cause changes to associated invertebrate species assemblages. Using a mini‐review of the literature and our own data we add to the still considerable debate about the most effective methods for testing community‐level impacts by invasive species. In endangered saltmarshes of southeast Australia, the non‐native rush Juncus acutus L. is displacing its native congener J. kraussii Hochst., with concurrent changes to floral and faunal assemblages. In two coastal saltmarshes, we tested the hypothesis that the ability to detect differences in the invertebrate assemblage associated with these congeneric rushes depends on the microhabitat of the plant sampled. We used three sampling methods, each targeting specific microhabitats: sweep netting of the plant stems, vacuum sampling of the plant tussock, and vacuum sampling of the ground directly below the plants. Over 3800 individuals and 92 morphospecies were collected across four main taxa: gastropods, crustaceans, hexapods and arachnids. Detection of differences in invertebrate density, richness and composition associated with native compared with non‐native rushes was dependent on the microhabitat sampled and these differences were spatially variable. For example, at one saltmarsh the stems and tussock of J. acutus had a lower density and richness of total invertebrates and hexapods than those of the native J. kraussii. In contrast, crustaceans on the ground were in greater abundance below J. acutus than J. kraussii. This study demonstrates that on occasions where overall differences in the assemblage are not detected between species, differences may become apparent when targeting different microhabitats of the plant. In addition, separately targeting multiple microhabitats likely leads to a greater probability of detecting impacts of invasion. Comparing the invertebrate assemblage without differentiating between or sampling an array of microhabitats can fail to determine the impact of invasive species. These results highlight that a combination of methods targeting different microhabitats is important for detecting differences within the invertebrate community, even for phylogenetically related species.     

贵州思雅河河谷地区喀斯特峰丛石漠苔藓植物群落研究

采用样带调查取样法,初步分析贵州思雅河河谷地区的喀斯特石漠区4座受人类活动影响频繁的峰丛以及3个坡段（坡底、坡中、坡顶）上的苔藓植物群落,研究苔藓植物群落在不同峰丛及其不同坡段的分布规律。结果显示:(1)在研究区域内,苔藓植物群落组成有8科19属40种,而且苔藓植物群落分为19个类型,其中纯群落有14个,常见群落有穗枝赤齿藓群落、真藓群落和卷叶湿地藓群落。(2)由于强烈的人类活动造成的干燥、贫瘠的环境,该区域苔藓主要生活型只有矮丛集型和交织型。(3)在这种特殊生境下,苔藓植物群落的丰富性也随着人类干扰范围的增大而减小。(4)在每座峰丛的不同坡段中,穗枝赤齿藓群落有着最大的综合优势比。推测穗枝赤齿藓群落对治理此类人为造成的石漠化生境具有实际应用潜力。     

Obituaries

Abstract

It has been suggested that bryophyte communities differ from those of higher plants, in that species coexistence is not limited by inter-specific competition. To test this hypothesis, bryophyte ‘lawns’ were-sampled at six locations in southern New Zealand. At each site, 625 quadrats, each ca 1 X 1cm, were arranged on a contiguous grid.

Variance in quadrat richness was significantly less than expected on a random basis at four sites, with the same trend in a fifth, i.e. quadrat richness was relatively constant. Since a patch model was used to reduce the effects of micro-environmental variation and spatial autocorrelation, this suggests that competition was restricting coexistence. The degree of restriction was similar to that found previously in grass lawn communities.

Species association was calculated on a patch basis, examining only small spatial-scale deviations from expectations. At four- sites this gave only negative associations. At the other two sites there were both positive and negative associations, but the pattern of associations gave no indication of Root/Pianka-type guilds.

Examination of the variance in guild proportions, using taxonomic (moss vs liverwort) and morphological (prostrate vs erect) guilds, gave- no indication of significant guild structure for any site (i.e. in the overall analyses for each site, index RV_gp was very close to the null-model expectation of 1.0).

Searches using the Wilson- Roxburgh method failed to reveal any significant intrinsic guild classification. That is, there was no indication of groups of species within a community that tended to be mutually exclusive because of similarity in resource use. Thus, lack of guild proportionality using a priori guilds was not due to the use of an inappropriate guild classification, but to lack of a guild structure in the communities.

It is concluded that there is community structure among bryophytes, in that species exclude each other to the same degree as higher-plants do in their communities. However, there is no evidence of structuring of these bryophyte communities into guilds; it seems that bryophyte species all form one guild.     

Geographical,anthropogenic and climatic determinants of bryophyte species composition and richness in the Shengsi archipelago,East China Sea

Introduction. Few attempts have been made to assess the comparative contributions of different environmental factors on species composition (SC) and richness (SR) of bryophytes on continental islands.

Methods. The bryophyte flora and the impact of seven environmental variables (island area, elevation, isolation, human disturbance, rainfall, vegetation cover, and exposed rock area) on 18 continental islands of the Shengsi archipelago in the East China Sea were investigated. Redundancy Analysis and Canonical Correspondence Analysis were used to determine to what extent the environmental variables could explain variation in species richness and species composition on these islands.

Key results & Conclusions. Island elevation, isolation, area and human disturbance intensity all significantly influenced bryophyte SC at island level, accounting for 12.7%, 9.9%, 8.8% and 7.8% of the total SC variation, respectively. Island area was the most important determinant of bryophyte SR (P?=?0.002), accounting for 58.3% of the total variation (9.7% by area per se and 48.6% confounded with other variables); elevation and human disturbance intensity also significantly influenced species richness, accounting for 10.5% and 6.9% of the total SR variation (conditional effects), respectively. Elevation and area had a positive interaction effect on SR while isolation exerted no significant effects (P?>?0.05). The relationships of bryophyte species number (S) with area (A) follow log₁₀ (S)?=?c?+?z?×?log₁₀ (A), with z values from 0.28 to 0.38. The effects of human disturbance on bryophyte SR followed the Gaussian model, supporting the ‘intermediate disturbance hypothesis’ to some extent.     

Soil depth shapes plant functional diversity in granite outcrops vegetation of Southwestern Australia

Background: The arid and nutrient-poor Southwestern Australia is one of the global biodiversity hotspots. Embedded in this landscape, granite outcrops are considered terrestrial insular habitats supporting habitat heterogeneity when compared to the more homogenous surrounds. Ecology of plant species and communities on granite outcrops has been addressed in numerous studies. However, functional diversity (FD) in context of the environmental heterogeneity remained unexplored.

Aims: We tested whether mesic deep-soil habitats on granite outcrops can sustain larger FD than dry shallow-soil habitats.

Methods: We calculated FD for dominant species for five single traits (leaf dry matter content, foliar δ¹³C, foliar C:N ratio, plant height and specific leaf area) and their combinations. We employed Generalized Additive Mixed Models to quantify the relationship between selected climate and soil depth variables, and FD.

Results: More benign (deep-soil) habitats supported larger FD for foliar C:N, plant height and for multiple traits than did shallow-soil habitats.

Conclusions: We suggest that: (1) functional diversification, likely aimed at avoiding intra- and interspecific competition for light and nutrients acquisition, might be the important factor in deep-soil habitats; (2) deep-soils patches on and around granite outcrops may serve as ecological microrefugia for biota associated with resource-rich environments.     

High plant taxonomic beta diversity and functional and phylogenetic convergence between two Neotropical inselbergs

ABSTRACT

Background: Inselbergs (granitic and gneissic rock outcrops) are common elements in the Atlantic Forest and present large taxonomic (TD), functional (FD) and phylogenetic (PD) diversity.

Aims: We investigated how plant diversity changed across ecological and biogeographic scales by comparing TD, FD and PD of communities within and between two inselbergs. We expected converging FD and PD but distinct TD between outcrops, because of similar local environmental conditions in inselbergs and the long-term lineage isolation.

Methods: We calculated TD, PD and FD, and partitioned diversity into α (each inselberg), β (between inselbergs) and γ (whole sample) components. Phylogenetic signal was estimated for all traits. To link environmental predictors to functional traits a redundancy analysis was run. Variation in TD, FD and PD was analysed by general linear models with patch area and the two inselbergs as predictors.

Results: The inselbergs were taxonomically different, but showed convergence in their functional and phylogenetic diversity. The limited retention of phylogenetic signal suggests that different species may converge and respond similarly to environmental variables. Within inselbergs, larger patches displayed higher TD, FD and PD.

Conclusions: Seeking conservation strategies for inselbergs is challenging since, despite their functional and phylogenetic similarity, endemic species make individual rock outcrops unique.     

Plant communities and landscape diversity along a Canadian Arctic river

Abstract. We analysed the structure and diversity of the vegetation along an Arctic river to determine the relationship between species richness and plant community structure. We examined whether variation in species richness along the corridor is structured as (1) an increase in the number of communities due to increasing landscape heterogeneity, (2) an increase in the floristic distinctiveness (β-diversity) of communities, or (3) an increase in within-community richness (α-diversity) as species-poor communities are replaced by species-rich communities. We described 24 community types and analysed the relationship between site vascular species richness (γ-diversity) and β-diversity, α-diversity, site environmental heterogeneity, and the number of distinct plant communities. We also measured diversity patterns of vascular, bryophyte, and lichen species within communities and examined their relationship to community-level estimates of environmental factors. We found that an increase in site species richness correlated with an increase in the number of communities (r²= 0.323, P= 0.0173) and β-diversity (r²= 0.388, P= 0.0075), rather than an increase in the α-diversity of individual communities. Moisture and pH controlled most of the differences in composition between communities. Measures of species richness and correlations with moisture and pH within communities differed among vascular, bryophyte, and lichen species. Bryophyte richness was positively correlated with moisture (r²= 0.862, P= 0.0010) and lichen richness was negatively correlated with moisture (r²= 0.809, P= 0.0031). Vascular plants had a peak in richness at pH 6.5 (r²= 0.214, P < 0.0001). We conclude that site variation in vascular richness in this region is controlled by landscape heterogeneity, and structured as variation in the number and distinctiveness of recognizable plant communities.     

Tufa Barriers from a Caddisfly's Point of View: Streams or Lake Outlets?

The caddisfly community composition in different microhabitats at tufa barriers was studied in the Plitvice Lakes NP, Croatia. Three tufa barriers were investigated and six emergence traps were installed at each site covering various microhabitats. Sampling was conducted monthly during the year 2008. Tufa barriers are lake outlet habitats, but they feature a variety of microhabitats similar to streams, which is reflected in the composition of caddisfly communities regarding longitudinal distribution preferences. The caddisfly communities at all three sites were dominated by species typical for the rhithral zone, but there was a shift in species composition along a longitudinal gradient, from the epirhithral to the metarhithral zone. Analysis of functional feeding guilds showed considerable differences between the caddisfly community at the Labudovac barrier and both downstream barriers, shifting from one with a quite diverse composition, to one completely dominated by passive filter‐feeders. Passive filter feeders were not represented by the same taxa at up‐ and downstream barriers (i.e., by Hydropsyche species and Wormaldia species, at the Labudovac barrier and at both downstream barriers, respectively). Due to high complexity and habitat diversity, the highest diversity and equitability of caddisfly communities were recorded at microhabitats with particulate tufa and medium current velocity (10–20 cm/s). The lowest diversity and species richness were recorded for silt with low current velocity (0–10 cm/s). Abundance of caddisflies was positively correlated with current velocity due to a very high proportion of rheophilic passive filter feeders in the communities. However, community composition and structure is only to some degree influenced by microhabitat characteristics, but rather by their general position within the barrage‐lake system, i.e., longitudinal distribution and thereby availability of different food resources. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Plant richness and composition in hardwood forest understories vary along an acidic deposition and soil-chemical gradient in the northeastern United States

Aims

A century of atmospheric deposition of sulfur and nitrogen has acidified soils and undermined the health and recruitment of foundational tree species in the northeastern US. However, effects of acidic deposition on the forest understory plant communities of this region are poorly documented. We investigated how forest understory plant species composition and richness varied across gradients of acidic deposition and soil acidity in the Adirondack Mountains of New York State.

Methods

We surveyed understory vegetation and soils in hardwood forests on 20 small watersheds and built models of community composition and richness as functions of soil chemistry, nitrogen and sulfur deposition, and other environmental variables.

Results

Community composition varied significantly with gradients of acidic deposition, soil acidity, and base cation availability (63% variance explained). Several species increased with soil acidity while others decreased. Understory plant richness decreased significantly with increasing soil acidity (r?=?0.60). The best multivariate regression model to predict richness (p?<?0.001, adjusted-R²?=?0.60) reflected positive effects of pH and carbon-to-nitrogen ratio (C:N).

Conclusions

The relationship we found between understory plant communities and a soil-chemical gradient, suggests that soil acidification can reduce diversity and alter the composition of these communities in northern hardwood forests exposed to acidic deposition.

     

Zygodon forsteri(Brld.) Mitt. in Buckinghamshire

Abstract

Data from hemispherical (‘fisheye’) photographs are presented from twenty bryophyte sites, including open grassland and rock outcrops of various slopes and aspects, habitats of mountain species on shaded cliffs and in corries, and wooded habitats of lowland atlantic species. These demonstrate effects of slope and aspect on both instantaneous and total energy income in direct sunshine, especially marked during the winter half of the year. Corrie habitats of northern atlantic species such as Herberta adunca and Mastigophora woodsii were exposed to direct sun only for a limited period in summer, with peak direct irradiance in June (about half that for an unobstructed level site in the examples considered). Wooded habitats of lowland atlantic species received their peak irradiance (both direct and diffuse) immediately before leaf expansion in spring; direct irradiance at this period relative to an unobstructed level site ranged from 0.8 (instantaneous)/0.35 (daily total) (Plagiochila spinulosa, Scapania gracilis: Devon) down to negligible values (Drepanolejeunea hamatifolia, Aphanolejeunea microscopica; ravine sites in N. Wales and Yorkshire).