Patterns of Plant Invasions: A Case Example in Native Species Hotspots and Rare Habitats

Land managers require landscape-scale information on where exotic plant species have successfully established, to better guide research, control, and restoration efforts. We evaluated the vulnerability of various habitats to invasion by exotic plant species in a 100,000 ha area in the southeast corner of Grand Staircase-Escalante National Monument, Utah. For the 97 0.1-ha plots in 11 vegetation types, exotic species richness (log₁₀) was strongly negatively correlated to the cover of cryptobiotic soil crusts (r = −0.47, P < 0.001), and positively correlated to native species richness (r = 0.22, P < 0.03), native species cover (r = 0.23, P < 0.05), and total nitrogen in the soil (r = 0.40, P < 0.001). Exotic species cover was strongly positively correlated to exotic species richness (r = 0.68, P < 0.001). Only 6 of 97 plots did not contain at least one exotic species. Exotic species richness was particularly high in locally rare, mesic vegetation types and nitrogen rich soils. Dry, upland plots (n = 51) had less than half of the exotic species richness and cover compared to plots (n = 45) in washes and lowland depressions that collect water intermittently. Plots dominated by trees had significantly greater native and exotic species richness compared to plots dominated by shrubs. For the 97 plots combined, 33% of the variance in exotic species richness could be explained by a positive relationship with total plant cover, and negative relationships with the cover of cryptobiotic crusts and bare ground. There are several reasons for concern: (1) Exotic plant species are invading hot spots of native plant diversity and rare/unique habitats. (2) The foliar cover of exotic species was greatest in habitats that had been invaded by several exotic species.(3) Continued disturbance of fragile cryptobiotic crusts by livestock, people, and vehicles may facilitate the further invasion of exotic plant species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Changes in forest understorey vegetation in Norway related to long‐term soil acidification and climatic change

Question: Does the understorey vegetation of Norwegian boreal forests change in relation to broad‐scale, long‐term changes? Location: Norway. Methods: Permanently marked 1‐m² vegetation plots from 17 monitoring reference areas in forests dominated by Picea abies (11 areas, 620 plots) and Betula spp. (six areas, 300 plots) were analysed twice, at the start in 1988–1997 and 5 yr later (1993–2002). Species subplot frequency data were analysed separately for each area by univariate and multivariate statistical methods; 5‐yr changes in single species abundances, species number per plot and species composition were tested. Results: Two distinct patterns of change were found: 1. Abundance of several vascular plant species decreased in SE Norwegian Picea forests, most noticeably of species with a preference for richer soils, such as Oxalis acetosella. 2. Abundance of many bryophyte species as well as bryophyte species number per plot increased in forests of both types over most of Norway. Conclusions: The pattern of vascular plant changes is probably a time‐delayed response of long‐lived, mainly clonal, populations to acidified soils resulting from deposition of long‐distance airborne pollutants. The pattern bryophyte changes, with reference to the close link between climatic conditions for growth and abundance changes for Hylocomium splendens established in previous demographic studies, is related to climatic conditions favourable for bryophyte growth. We conclude that many forest understorey plants are sensitive indicators of environmental change, and that the concept used for intensive monitoring of Norwegian forests enables early detection of changes in vegetation brought about by broad‐scale, regional, impact factors.     

The effects of stand structure on ground-floor bryophyte assemblages in temperate mixed forests

The effect of tree species composition, stand structure characteristics and substrate availability on ground-floor bryophyte assemblages was studied in mixed deciduous forests of Western Hungary. Species composition, species richness and cover of bryophytes occurring on the soil and logs were analysed as dependent variables. The whole assemblage and functional groups defined on the basis of substrate preference were investigated separately. Substrate availability (open soil, logs) was the most prominent factor in determining species composition, cover and diversity positively, while the litter of deciduous trees had a negative effect on the occurrence of forest floor bryophytes. Besides, bryophyte species richness increased with tree species and stand structural diversity, and for specialist epiphytic and epixylic species log volume was essential. Sapling density and light heterogeneity were influential on bryophyte cover, especially for the dominant terricolous species. Many variables of the forest floor bryophyte community can be estimated efficiently by examining stand structure in the studied region. Selective cutting increasing tree species diversity, stand structural heterogeneity and dead wood volume can maintain higher bryophyte diversity in this region than the shelter-wood system producing even-aged, monodominant, structurally homogenous stands.     

Rapid assessment of butterfly diversity in a montane landscape

We present the results of a rapid assessment of butterfly diversity in the 754 ha Beaver Meadows study area in Rocky Mountain National Park, Larimer County, Colorado. We measured butterfly species richness and relative abundance as part of a landscape-scale investigation of diversity patterns involving several groups of organisms. A stratified random sampling design was used to include replication in both rare and common vegetation types. We recorded 49 butterfly species from the twenty-four 0.1 ha plots that were sampled four times during June, July, and August 1996. Butterfly species richness, diversity, and uniqueness were highest in quaking aspen (Populus tremuloides Michaux) groves and wet meadows, which occupy only a small proportion of the studied landscape. This result supports the suggestion that aspen areas represent hotspots of biological diversity in this montane landscape. Patterns of butterfly species richness were positively correlated with total vascular plant species richness (r = 0.69; P < 0.001), and native plant species richness (r = 0.64; P < 0.001). However, exotic plant species richness (r = 0.70; P < 0.001) and the cover of exotic plant species (r = 0.70; P < 0.001) were the best predictors of butterfly species richness.     

Tree and stand level variables influencing diversity of lichens on temperate broad-leaved trees in boreo-nemoral floodplain forests

Tree and stand level variables affecting the species richness, cover and composition of epiphytic lichens on temperate broad-leaved trees (Fraxinus excelsior, Quercus robur, Tilia cordata, Ulmus glabra, and U. laevis) were analysed in floodplain forest stands in Estonia. The effect of tree species, substrate characteristics, and stand and regional variables were tested by partial canonical correspondence analysis (pCCA) and by general linear mixed models (GLMM). The most pronounced factors affecting the species richness, cover and composition of epiphytic lichens are acidity of tree bark, bryophyte cover and circumference of tree stems. Stand level characteristics have less effects on the species richness of epiphytic lichens, however, lichen cover and composition was influenced by stand age and light availability. The boreo-nemoral floodplain forests represent valuable habitats for epiphytic lichens. As substrate-related factors influence the species diversity of lichens on temperate broad-leaved trees differently, it is important to consider the effect of each tree species in biodiversity and conservation studies of lichens. Nomenclature Randlane et al. (2007) for lichens; Leht (2007) for vascular plants.     

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.     

Tibetan sacred sites conserve old growth trees and cover in the eastern Himalayas

Khawa Karpo, in the eastern Himalayas, is a mountain considered sacred throughout Tibet, and is internationally recognized as a global biodiversity hotspot. Numerous areas within this landscape are considered ‘sacred’ by the indigenous Tibetans of the region, who interact with these sites in ways potentially beneficial to conservation. Our previous remote sensing study indicated that sacred sites are found in habitats with greater species richness, diversity, and endemism than randomly selected non-sacred sites. This study examines the role of sanctity in biodiversity conservation within habitats in the Khawa Karpo region by pairing plots within the same habitats in sacred and non-sacred areas. Understory richness, diversity, cover, and number of useful species are measured; for trees, richness, diversity, cover, and density are measured. Results indicate that within habitats sanctity does not affect understory plant communities; however, within sacred areas trees are larger (p = 0.003) and forests have greater cover (p = 0.003) than non-sacred areas. Our results indicate that, whereas placement of sacred areas and preservation of vegetation cover affects useful plants, biodiversity and endemism, within habitats sacred sites preserve old growth trees and forest structure. In sum, Tibetan sacred sites are ecologically unique and important for conservation on varying scales of landscape, community, and species.     

生态恢复方式对喀斯特生境苔藓植物物种组成的影响

为探究生态恢复方式对苔藓植物的影响，研究了自然弃耕和退耕还林等生态恢复方式对重庆市中梁山喀斯特地区不同生境类型下苔藓植物物种组成特征的影响。结果表明，研究区有苔藓植物15科26属41种，其中藓类39种，苔类2种，美灰藓(Eurohypnum leptothollum)为主要优势物种；研究区石生藓类植物占比较大，生活型以平铺型和丛集型为主，各生境物种多样性及相似性指数整体偏低，但相比弃耕杂草地、灌木林和经济型林地，竹林和马尾松林中苔藓植物具有更高的物种多样性；冗余分析表明，郁闭度和光照强度是影响苔藓植物分布的关键环境因子，乔木林为苔藓植物的生长提供了更适宜的生境。因此，相比于自然恢复和经济性林地等恢复方式，退耕还林是喀斯特退化生境更为理想的生态恢复方式。     

Habitat preferences of red-listed fungi and bryophytes in woodland key habitats in southern Sweden – analyses of data from a national survey

The aim of this study was to identify habitat preferences of red-listedepiphytic and epixylic bryophyte, lichenized and non-lichenized fungi speciesinwoodland key habitats (WKHS) (areas less than 10 ha, where foreststructures indicate occurrence of red-listed species) in southern Sweden. Therelative importance of different groups of environmental factors was assessedwith partial canonical correspondence analysis techniques and across-validationapproach using data from 7196 selected WKHs. Different woody substrates (oldtrees, logs and snags) made up the most important variable group for occurrenceof red-listed species (30% unique explainable variation). Species associatedwith Fagus sylvatica and Picea abieshabitats, but also species associated with Quercus spp.andPopulus tremula habitats showed distinct habitatpreferences. The second most important variable group (16% unique explainablevariation) was geographical location. A west–east gradient was identified, andspecies concentrated to Baltic islands in the east were separated from otherspecies. This gradient, and an identified south–north gradient, probablyreflect differences in temperatures and rainfall between different regions.Among the remaining variable groups, historical land-use, ground conditions andforest stand composition were of similar importance (5–7% uniqueexplainable variation). Traditional management regimes resulting in semi-openforest habitats (leaf harvesting, forest grazing and selective cutting) wereassociated with the occurrence of many species, probably due to differences inmicroclimate between sites of different openness. Furthermore, a groundmoisturegradient extending from species associated with dry sites (mainly lichenizedfungi) to species associated with wet sites (mainly bryophytes), and a nutrientgradient from species associated with nutrient-poor sites to species occurringat nutrient-rich sites, were identified. Thus, conservation measures are neededin a broad spectrum of habitats with different substrates. Also sites withsimilar substrates, but situated in different regions (and climates), or withdifferent ground moisture and nutrient conditions are needed to cover the fullspectrum of habitat conditions suitable for different red-listed bryophytes andfungi.     

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.     

Inter- and intra-habitat relationships between woodland cryptostigmata species diversity and the diversity of soil and litter microhabitats

Summary Soil animal communities contain a large number of species exhibiting a low degree of trophic specialization. Competition between animal species with similar food requirements is frequently reduced by partitioning habitat space and this ecological principle is demonstrated for woodland mite communities. Microhabitat diversity was determined for the litter (L), fermentation (F) and humus (H) sub-horizons using gelatine embedded soil sections and compared with mite species diversity for the same layers of the soil and litter profile. Cryptostigmata species diversity was correlated with microhabitat diversity (r=0.67, P<0.01) in six woodland soils with a range of humus forms. Intra-habitat relationships were determined for one site on two sampling occasions: in November an exceptionally high correlation was obtained (r=0.91, P<0.001) but samples collected in February showed a lower correlation (r=0.63, P<0.01). Within sub-horizon relationships showed significant correlations for the L (r=0.59, P<0.01) and H sub-horizons (r=0.72, P=0.001). The F sub-horizon data were more variable than the other two sub-horizons but a correlation of 0.60 (P=0.05) was obtained for the intrahabitat study.     

Epiphytic bryophytes growing on Laurus azorica (Seub.) Franco in three laurel forest areas in Tenerife (Canary Islands)

We examined bryophyte species growing on Laurus azorica, in three localities of the laurel forest in Tenerife (Canary Islands), in order to determine differences in species composition, richness and cover, that depend on variations in mist frequency and density. Among the 35 bryophyte species found (26 liverworts and nine mosses), 16 occurred in all three locations while nine species occurred in only one location. Detrended correspondence analysis and canonical correspondence analysis revealed that the epiphyte–phorophyte relationship varied in terms of cover, richness and bryophyte composition, depending on the humidity conditions (related to mist frequency and plot height) and tree age. In spite of differences in the dominant species found at each locality, the community types have many species in common and may be seen as a natural unit of the communities involved. Variation in the dominant species at each locality is mainly related to a trade off between humidity conditions and tree diameter, and the speed of the successional processes. Plot aspect was the only variable among those considered with no significant influence, which might be related to the closed canopy conditions. Variation in cover, richness and bryophyte composition related to plot height and tree diameter increased in the drier location. Cover was positively related to species richness in all analyses. This is related to low diversity during initial colonization and the fact that the highest biomass species, related to later successional stages, also occur on younger trees, especially in the more humid areas.     

Diversity patterns of ground beetles and understory vegetation in mature,secondary, and plantation forest regions of temperate northern China

Plantation and secondary forests form increasingly important components of the global forest cover, but our current knowledge about their potential contribution to biodiversity conservation is limited. We surveyed understory plant and carabid species assemblages at three distinct regions in temperate northeastern China, dominated by mature forest (Changbaishan Nature Reserve, sampled in 2011 and 2012), secondary forest (Dongling Mountain, sampled in 2011 and 2012), and forest plantation habitats (Bashang Plateau, sampled in 2006 and 2007), respectively. The α‐diversity of both taxonomic groups was highest in plantation forests of the Bashang Plateau. Beetle α‐diversity was lowest, but plant and beetle species turnover peaked in the secondary forests of Dongling Mountain, while habitats in the Changbaishan Nature Reserve showed the lowest turnover rates for both taxa. Changbaishan Nature Reserve harbored the highest proportion of forest specialists. Our results suggest that in temperate regions of northern China, the protected larch plantation forest established over extensive areas might play a considerable role in maintaining a high biodiversity in relation to understory herbaceous plant species and carabid assemblages, which can be seen as indicators of forest disturbance. The high proportion of phytophagous carabids and the rarity of forest specialists reflect the relatively homogenous, immature status of the forest ecosystems on the Bashang Plateau. China's last remaining large old‐growth forests like the ones on Changbaishan represent stable, mature ecosystems which require particular conservation attention.     

Reproductive Responses of Northern Goshawks to Variable Prey Populations

ABSTRACT Developing comprehensive conservation strategies requires knowledge of factors influencing population growth and persistence. Although variable prey resources are often associated with fluctuations in raptor demographic parameters, the mechanisms of food limitation are poorly understood, especially for a generalist predator like the northern goshawk (Accipiter gentilis). To determine the reproductive responses of goshawks to variable prey populations, we evaluated 823 goshawk breeding opportunities on the Kaibab Plateau, Arizona, USA, during 1994–2002. Concurrently, density was estimated for 4 prey species (2 avian, 2 mammalian). We explored the relationship between goshawk reproduction and prey density at one temporal scale (year) and 2 spatial scales (study area, forest type). Prey density for all 4 species combined accounted for 89% of the variation in goshawk reproduction within the entire study area (P < 0.001), 74% in mixed conifer forest (P = 0.003) and 85% in ponderosa pine (Pinus ponderosa) forest (P < 0.001). We found that an incremental increase in prey density resulted in a greater increase in goshawk reproduction in ponderosa pine forest than in mixed conifer forest, suggesting that the denser structural conditions of mixed conifer forest may have reduced prey availability. Red squirrel (Tamiasciurus hudsonicus) density explained more annual variation in goshawk reproduction within the study area (r² = 0.87, P < 0.001), mixed conifer forest (r² = 0.80, P = 0.001), and ponderosa pine forest (r² = 0.85, P < 0.001) than did any other individual species. Although certain prey species were more strongly correlated with fluctuations in goshawk reproduction than were others, the high model selection uncertainty and the strong relationship between total prey density and number of goshawk fledglings produced indicated that alternate prey species were readily substituted for one another. Therefore, conservation strategies concerned with the status of goshawk populations should incorporate forest management practices that increase the abundance, diversity, and availability of prey resources.     

Recovery of conservation values in Central African rain forest after logging and shifting cultivation

Secondary forests in Central Africa are increasing in importance for biodiversity conservation as old growth forests outside the few protected areas are disappearing rapidly. We examined vegetation recovery in a lowland rain forest area in Cameroon based on a detailed botanical survey of old growth forest and different-aged logging gaps (5–27 years) and shifting cultivation fields (10–60 years). Our analysis focuses on the long-term recovery of botanical conservation values by analysing trends in vegetation structure, species composition, species diversity and levels of endemism and rarity. In the total survey (4.25 ha), we recorded 834 species of which 23% were endemic to the Lower Guinea forest region. The proportion of endemic species was high in shrubs and low in herbs. Geographic range and (local) rarity were not significantly associated. The proportion of rare species (relative frequency <10%) was high in woody climbers and low in trees. In logging gaps, recovery of all vegetation characteristics was relatively quick (5–14 years). Recovery in shifting cultivation sites took longer (30–60 years). Endemic species were found to be highly sensitive to shifting cultivation practices and even after 50–60 years the level of endemism was still significantly lower compared to old growth forest. The proportion of rare species was not significantly different between disturbed sites and old growth forest. We conclude that secondary forests can contribute to biodiversity conservation, e.g. as buffer zones around protected areas. However, this contribution should be assessed differently between land use types and widespread versus endemic species.     

The effects of environmental variation on bryophytes at a regional scale

The distribution of bryophytes in central Belgium was investigated using species grid‐mapping superimposed on a series of maps which included information on soil conditions and land use. Our objectives were to assess the influence of environmental variation on the bryoflora at a regional scale, to examine how bryophytes respond to environmental variation, and to assess the extent to which species ecological and life‐history traits determine the accuracy of the predictability of species occurrence in order to provide comprehensive lists of species based on environmental conditions. The first two axes of a correspondence analysis (CA) of the floristic data explained 14.6% of the total χ². CA1 was significantly correlated with loamy‐sandy soils on a sand layer (r=?0.74, p<0.001), forest cover (r=?0.80, p<0.001), loamy soils (r=0.79, p<0.001), and agricultural fields cover (r=0.61, p<0.001). CA2 had a low but significant correlation coefficient with pebbly soils cover (r=0.38, p<0.001). The probability of occurrence of 59% of the investigated species could be significantly predicted by logistic regression from the sets of environmental variables. About 55% of the species exhibited an increasing probability of occurrence with increasing forest cover and loamy‐sandy soils cover, 1% with agricultural fields and loamy soils cover, and 3% with pebbly soils cover. The predictability of species occurrence varied as a function of four life‐history traits (minimum spore size, life expectancy, type of gametophyte and papillose leaf cell walls) and three ecological traits (indicator values of light, temperature and soil acidity). The most predictable species, including a number of leafy liverworts, were characteristic for acidic, fresh and shaded conditions and displayed a strong preference for forest habitats. Taxa with limited predictability included epiphytes and mosses characteristic of pebbly soils due to the ability of these species to efficiently disperse and adapt to various ecological conditions. Species for which the distribution range could not successfully be predicted were either ubiquitous, characteristic for ephemeral habitats, or highly successful in a very common habitat.     

Species assemblages and community structure of adult caddisflies along a headwater stream in southeastern Ghana (Insecta: Trichoptera)

Adult caddisflies were collected at 12 sites along a 5 km stretch of a forested headwater stream in southeastern Ghana in March and November 1993 and the catches are related to environmental variables. Some 34,000 specimens, belonging to 178 morphospecies in 43 genera and 11 families, were caught with Malaise traps and light traps. Many species demonstrate differences between sampling method, seasonal occurrence, and sex-ratios, with the light trap in the second wet sunny season (November) being most efficient with respect to the diversity of the catches. A Moran index analysis for global structures indicates a major transition in the fauna from the ravine with waterfalls to the forest, and secondly, a gradient through the forest. A Geary index analysis for local structures indicates further faunal turnovers in the lower reaches of the stream. Species-environment relationships were analyzed through correspondence analysis and co-inertia analysis, allowing ordination of both species and the environment into three zones. The first co-inertia axis reveals a transition between the waterfalls in the open ravine (sites 1–3), and the stream through the riverine forest (sites 4–12), while the second co-inertia axis reveals a gradient from the lotic stream in the moist semi-deciduous forest (sites 4–8) to more lentic stretches of the stream in a gradually more depleted forest (sites 9–12). The most important environmental factors related to the species transition are: riparian moss growth (r=0.94), leaves in the stream substratum (r=0.91), forest type (r=0.90), hygropetric surfaces (r=0.88), bedrock (r=0.87), lotic [riffle] (r=0.85) and lentic [pool] (r=0.85) stretches. The most important environmental factors related to the species gradient are: lotic [riffle] stretches (r=0.92), gravel (r=0.88) and leaves (r=0.85) in the stream substratum, forest type (r=0.81), and agricultural use (r=0.76). Three clusters representing three major environmental zones (zone I, II and III) along the stream are identified by projecting the average species positions on the co-inertia plane. By analyzing the Malaise trap samples significant indicator values are found for 29 species in zone I, 16 species in zone II, and 18 species in zone III. By analyzing the light trap samples significant indicator values are found for 17 species in zone I, 57 species in zone II, and 38 species in zone III. The high diversity of caddisflies in the sanctuary might be reflected both in the geological and climatological history of West Africa, as well as in the recognition of three major environmental zones, and the clean water with high diversity of stream microhabitats favorable for Trichoptera larvae. The closed forest seems to play an important role for the Trichoptera community, and the study demonstrates the importance of protecting forested headwater streams in order to maintain a sustainable aquatic biodiversity in tropical Africa.     

The effects of burning on the understorey composition of 11–13 year-old rehabilitated bauxite mines in Western Australia – Vegetation characteristics

Alcoa of Australia Limited has been rehabilitating bauxite mines in the jarrah (Eucalyptus marginata) forest of Western Australia for more than 30 years. Mines rehabilitated in the early 1980s using out-dated methods have built up substantial fuel loads that may be reduced through prescribed burning. The vegetation response of 11–13 year-old rehabilitated bauxite mines to fire regimes differing in intensity and season over the first two years of post-burn succession is compared to the native jarrah forest. A total of 243 species from 137 genera and 56 families were identified in the native forest reference sites and in the 11–13 year-old rehabilitated areas before and after burning. The vegetation of the pre-burn rehabilitated areas was very different to that of the native jarrah forest. While total live plant cover, Acacia density, non-native eucalypt seedling density, weed density and the evenness index were similar between the two areas, total plant density, live Acacia cover, the proportion of weeds, native species numbers and diversity were significantly different. However, the greatest difference between the vegetation of the pre-burn rehabilitated sites and the native jarrah forest was the higher dominance of seeding species (plants killed by fire) in rehabilitated areas. In contrast, native jarrah forest was dominated by resprouting species (plants that survive fire). Burning the rehabilitated sites was successful in making the areas more similar to the forest in terms of total plant density, live Acacia cover and native species numbers but decreased their similarity in terms of live plant cover, Acacia density, non-native eucalypt seedling density, weed density and evenness. The vegetation response of the rehabilitated areas to different seasons of burning showed that autumn burning led to a greater increase in plant establishment than spring burning. Autumn burning also resulted in an undesirable increase in the density of non-native eucalypt seedlings that was not observed following spring burning. Although burning these 11–13 year-old rehabilitated sites will increase similarity to the native forest, it is unlikely that they will resemble the native jarrah forest without further management intervention.     

Landscape mosaic of Araucaria forest and forest monocultures influencing understorey spider assemblages in southern Brazil

Abstract This study investigates how abundance, diversity and composition of understorey spiders were influenced by four different forest habitats in a southern Brazilian Araucaria forest. The study area encompasses a landscape mosaic comprised of Araucaria forest, Araucaria plantation, Pinus plantation, and Eucalyptus plantation. Understorey spiders were collected by beating the vegetation inside three patches of each forest habitat. To assess possible predictors of spider assemblage structure, several patch features were analysed: potential prey abundances, estimation of vegetation cover, diversity index of vegetation types, patch ages, patch areas, and geographical distance between patches. To assess the influence of high‐level taxa approaches on spider assemblage patterns, analyses were carried out individually for family, genera and species levels. Additionally, Mantel tests were carried out in underlying similarity matrices between each taxon. Significant differences in spider abundances among forest habitats were found. Pinus plantations showed the highest abundance of spiders and Eucalyptus plantations showed the lowest abundance. Spider abundance was significantly influenced by patch ages, geographical distance and vegetation cover. Expected numbers of families, genera and species did not vary among forest habitats. Spider composition of two Eucalyptus patches differed from the other forest patches, probably due to their low vegetation cover and isolation. Genera composition was the best correlate of species composition, showing that a higher‐level surrogate can be an alternative to the species approach. The understorey spider diversity in this managed area could be maintained when suitable habitat structures are provided, thus ensuring the connectivity between different habitat types. Further studies should focus on individual species responses to the conversion of native forest to monocultures.     

Agricultural land use and black fly (Diptera,Simuliidae) species richness and species assemblages in tropical streams,Northeastern Thailand

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