Great Diversity Of Plant Species Research Articles

The effects of substrate depth heterogeneity on plant species coexistence on an extensive green roof

Green roofs are often planted with mixtures of plant species. Studies of green roof plant community composition over time show that species diversity often declines, in part due to competition between plant species. The incorporation of substrate depth heterogeneity into green roof designs is expected to increase habitat heterogeneity, and could reduce interspecific competition among plants, but this has not been tested empirically. Two species with contrasting responses to substrate depth and water availability, Festuca rubra and Sedum acre, were planted in a rooftop substrate depth heterogeneity experiment. There were a total of four treatments: three homogeneous treatments (substrate depth 5cm, 10cm, and 15cm) and one heterogeneous treatment (patches with substrate depths of 5cm and 15cm), with the same substrate volume and average depth as the 10cm homogeneous treatment. By the end of the study period there was little difference in the ratio of species’ cover between the 10cm and 5/15cm treatment. However, there was significantly less spread of each species into areas planted with the other species in the 5/15cm treatment compared to the 10cm treatment, and the 5/15cm (heterogeneous treatment) had significantly greater overall plant cover. The results suggest that, while the effects are subtle, soil depth heterogeneity could allow coexistence of species associated with different conditions for longer than homogeneous conditions, and could result in greater plant species diversity in green roof ecosystems.

Distribution patterns of spontaneous vegetation and pollution at a former decantation basin in southern Québec, Canada

After industrial activities shut down, the brownfields remaining on abandoned sites are often left to revegetate naturally, a process that reflects the site's biotic and abiotic characteristics, including spatial pollutant distribution. The soil of a former decantation basin in Varennes (southern Québec, Canada) was systematically sampled and described in terms of concentration of PAHs (polycyclic aromatic hydrocarbons), PHs (petroleum hydrocarbons C10–C50), various trace metals as well as ruderal plant abundance and diversity. Partial redundancy analysis was used to investigate the effect of heterogeneous pollution on the plant community's spatial distribution. Up to 61% of variance in spontaneous plant distribution was explained by the pollutant dispersion pattern on the study site. These findings provide guidelines for the design of site-specific and within-site remediation or rehabilitation promoting natural processes that are already in progress. They also suggest using local vegetation and a greater diversity of plant species when conditions are conducive as this may have many associated benefits. The resulting design, which promotes development of the local plant community, can be a more cost effective and environmentally sustainable alternative to traditional plant-based remediation approaches.

Effects of grazing on plant species diversity and pasture quality in subalpine grasslands in the eastern Pyrenees (Andorra): Implications for conservation

Mountain areas boast high levels of biodiversity due to the wide variety in topography, climates and traditional land-use practices they embrace. Recent changes in the mountain agro-ecosystems of Europe have led to a decline in these traditional practices (above all grazing) and have had negative effects on biodiversity. In this study we evaluated the effects of grazing pressure on plant species diversity and also focused on the common and rare species diversity, forage quality and forage production in the Festuca airoides, Festuca eskia, Festuca gautieri, Festuca paniculata and Nardus stricta grassland communities. These analyses could be of great importance in identifying the pastoral management practices that are most consistent with the conservation of plant diversity in the Andorran subalpine and alpine grasslands. Data were collected at 113 sampling sites exposed to either high or low grazing pressures. In all, 222 vegetation line-transects were established from which samples were collected and analysed using the NIRS method. In addition the lignin, protein and fibre fractions were obtained in order to evaluate the quality of the forage. In the Andorran summer pastures, the Festuca gautieri calcareous grasslands had the greatest plant species diversity, while the Festuca eskia, Festuca airoides and Nardus stricta grasslands had the lowest plant species diversity and a lack of common species due to their less homogeneous spatial structure. The highest quality forage corresponds to the Festuca gautieri and Nardus stricta grasslands, while the Festuca eskia grasslands have the lowest quality forage. Although high grazing pressure can lead to greater species diversity, it also tends to diminish forage quality and/or energy content by increasing the lignin content. Thus, domestic livestock is a fundamental element in these grasslands and an increase in the grazing pressure of the different types of livestock (cattle, sheep and horses) is necessary since a more balanced distribution of grazers between the grassland types – rather than an increase in grazers – will not be sufficient to maintain plant biodiversity. Likewise, there is a need to re-establish the practice of transhumance, a traditional pastoral practice based on the movement of livestock between winter lowland pastures and upland summer pastures.

Blue sheep in the Annapurna Conservation Area, Nepal: habitat use, population biomass and their contribution to the carrying capacity of snow leopards

The Himalaya region of Nepal provides a habitat for the endangered snow leopard (Panthera uncia) and its principal prey species, the blue sheep (Pseudois nayaur). The aim of this study was to describe the habitat, the distribution and the population structure of blue sheep, and to estimate their contribution to the carrying capacity of snow leopard in the upper Mustang region of Nepal. Blue sheep were recorded at altitudes from 3209-5498 m on slopes with gradients of 16-60° and aspects of 40°NE to 140°SE. A total of 939 blue sheep were counted in the upper Mustang region, and 98 were counted in the Yak Kharka region of Manang district; however, upper Mustang had the lowest population density of blue sheep recorded within their distribution range in Nepal (0.86 blue sheep/km(2)). The results of the study show that a higher density of blue sheep is associated with greater plant species diversity. The most important species present in the blue sheep habitat were Kobresia pygmaea, Artemesia spp., Lonicera spp., Lancea tibetica, Poa spp., Astragalus spp. and Ephedra gerardiana. It is estimated that the existing blue sheep population biomass of approximately 38 925 kg in the upper Mustang region could support approximately 19 snow leopards (1.6 snow leopards/100 km(2)).

Relationship between habitat characteristics and densities of southern Idaho ground squirrels

Many wildlife species living in sagebrush-steppe habitats of the Intermountain West of the United States have experienced population declines. Effective management of such species, especially restoration efforts, is contingent on understanding relationships between habitat characteristics and population densities of the target species. Unfortunately, even such basic information is often lacking. The goal of this 2-year study was to determine the relationship between southern Idaho ground squirrel (Urocitellus endemicus) population densities and habitat variables: soils (texture), topography (slope, aspect), and vegetation (canopy cover, species diversity). We measured population density indirectly through burrow entrance counts and categorized them into high-burrow and low-burrow densities. We used logistic regression and Akaike's Information Criterion to identify a best subset of models. We employed model averaging and calculated odds ratios for averaged parameter estimates found in the best models. A high density of burrows was associated with greater percentages of silt; east-facing aspects; greater plant species diversity; and greater cover of perennial grasses, perennial grasses and forbs, and native perennial forbs. Low burrow density was associated with greater percentages of sand; south-facing aspects; greater cover of exotic annuals; and lesser plant species diversity. Management of southern Idaho ground squirrel habitat should focus on protecting areas with existing native vegetation and restoring native, perennial vegetation in areas that are infested with exotic annuals, especially in areas possessing suitable soil types and topographic features. © 2013 The Wildlife Society.

Influence of conservation reserve program mid‐contract management and landscape composition on northern bobwhite in tall fescue monocultures

AbstractThe United States Department of Agriculture (USDA) authorized mid‐contract management (MCM) in 2004 to restore and maintain plant species composition and structural diversity in aging Conservation Reserve Program (CRP) fields for the northern bobwhite (Colinus virginianus) and other grassland‐dependent wildlife. We implemented 3 USDA‐approved MCM regimes (i.e., strip disking, strip glyphosate spraying, and strip glyphosate spraying in combination with legume interseeding) in 60 tall fescue (Festuca arundinaceae) CRP monocultures in south‐central Illinois, USA, during 2005–2008. We hypothesized that adult bobwhite relative densities and brood presence would increase following MCM that effectively restored early successional plant communities in otherwise monotypic stands of tall fescue. We estimated annual adult bobwhite relative densities and brood presence‐absence in managed and unmanaged CRP. We modeled vegetation characteristics and landscape composition to identify factors influencing adult densities and brood presence. Adult relative densities were 2‐fold greater in managed fields than in unmanaged fields, and were negatively correlated with greater percentages of grass cover. Adult densities were positively correlated with greater plant species diversity, and greater percentages of bare ground and legume cover. Logistic regression and odds ratio estimates indicated that fields managed with glyphosate‐interseed and glyphosate treatments were 39.6% more likely to have broods than unmanaged CRP, whereas disked fields were 10.0% more likely than unmanaged CRP. These models indicated that the probability of brood presence was greater in fields with increased percentage of bare ground, greater plant species diversity, and decreased percentage of grass and litter cover. These findings suggest that a 3‐year rotation of glyphosate or glyphosate‐interseed treatments can enhance habitat conditions for adult bobwhites and broods in CRP tall fescue monocultures. © 2011 The Wildlife Society.

Water-level regulation and coastal wetland vegetation in the upper St. Lawrence River: inferences from historical aerial imagery, seed banks, and Typha dynamics

We evaluated habitat changes of tributary (drowned river mouth) wetlands in the upper St. Lawrence River with analysis of pre-and post-regulation water levels and historical vegetation reconstruction from aerial photographs. In addition, the germination response of transplanted wetland soil was compared to understand responses to moist versus saturated hydrology. Typha stem density was sampled in reference sites under the influence of water-level regulation by the International Joint Commission (IJC) and compared to treatment sites where installed control structures held levels (<0.7 m) higher. Major hydrologic changes due to regulation included a reduction of inter-annual variability with a reduction in peak levels and periodic lows, leading to a dampening of 30–40 year water-level cycles. Wetland photo interpretation indicated that flooded and mixed habitat categories were apparent at all sites for pre-regulation in 1948, but post-regulation photos (1972 and 1994) showed encroachment of robust emergent (Typha angustifolia, T. latifolia, and T. x glauca) in these habitats. Vegetation surveys (7 years, 2001–2007) indicated that reference and treatment sites were dominated by Typha, but mean stem densities were not statistically different. Typha stem density, however, declined in response to decreased summer water level. Periodic summer low water levels coupled with higher winter levels (that promote muskrat activity) were hypothesized to have the greatest effect on reducing Typha density. Seed-bank analysis indicated that a greater diversity of plant species germinated in mesic (moist) conditions than in the saturated treatment (flooded), where Typha was the dominant seedling component. Altered hydrologic regimes and invasive Typha have had a substantial effect on habitat structure within coastal wetlands and inferences from local management of levels provide useful guidance for future system-wide regulation.

Agricultural Land Use and Biodiversity in the Alps

Alpine grasslands are ecosystems with a great diversity of plant species. However, little is known about other levels of biodiversity, such as landscape diversity, diversity of biological interactions of plants with herbivores or fungal pathogens, and genetic diversity. We therefore explored natural and anthropogenic determinants of grassland biodiversity at several levels of biological integration, from the genetic to the landscape level in the Swiss Alps. Differences between cultural traditions (Romanic, Germanic, and Walser) turned out to still affect land use diversity and thus landscape diversity. Increasing land use diversity, in turn, increased plant species diversity per village. However, recent land use changes have reduced this diversity. Within grassland parcels, plant species diversity was higher on unfertilized mown grasslands than on fertilized or grazed ones. Most individual plants were affected by herbivores and fungal leaf pathogens, reflecting that parcels harbored a great diversity of herbivores and pathogens. However, as plant damage by herbivores and pathogens was not severe, conserving these biological interactions among plants is hardly compromising agricultural goals. A common-garden experiment revealed genetic differentiation of the important fodder grass Poa alpina between mown and grazed sites, suggesting adaptation. Pervillage genetic diversity of Poa alpina was greater in villages with higher land use diversity, analogous to the higher plant species diversity there. Overall, landscape diversity and biodiversity within grassland parcels are currently declining. As this contradicts the intention of Swiss law and international agreements, financial incentives need to be re-allocated and should focus on promoting high biodiversity at the local and the landscape level. At the same time, this will benefit landscape attractiveness for tourists and help preserve a precious cultural heritage in the Swiss Alps.

Leaf litter diversity and shredder preferences in an Australian tropical rain-forest stream

Consumption of terrestrial leaf litter by stream invertebrates is an important process, but little attention has been paid to the influence of leaf diversity on the process. Tropical forests are known to have much greater diversity of plant species than their temperate counterparts, but studies of litter processing in tropical streams have not explicitly addressed this issue. This paper documents the streambed leaf litter composition and diversity of an Australian tropical rain-forest stream and the leaf preferences of consumers in the stream. We hypothesized that there would be high diversity of litter in the stream and that the shredders would have broad preferences, given that litterfall of any one species would occur over a restricted period. Leaf litter was characterized by high species diversity (81 species from one stream reach sampled on two occasions). Leaf consumers (‘shredders’) were associated with a relatively broad suite of leaf species (38 species) and did not indicate clear leaf preferences. However, in a laboratory feeding experiment, using the three most common shredder species and some of the most abundant leaf species in the stream, all shredder species exhibited clear preference for a single leaf species (Endiandra bessaphila). Preference for this and other species was affected by the conditioning age of leaves (i.e. the length of time leaves were exposed to leaching and microbial colonization), with conditioned leaves usually being preferred, and previously non-selected leaves becoming more palatable with conditioning. Thus, different successional stages were more important than the identity of leaf species in determining the distribution of shredders among the leaves.

Impact of root-rot pathogens on forest succession in unmanaged Pinus mugo stands in the Central Alps

In the mountain pine (Pinus mugo subsp. uncinata (DC.) Domin) forests of the Swiss National Park in the Central Alps, disease centers associated with the root-rot fungi Heterobasidion annosum (Fr.) Bref. and Armillaria spp. are characteristic elements. We assessed the impact of these pathogens on forest dynamics by studying transects running across disease centers into the adjacent forest. Overall, mountain pine was the most abundant regenerating tree species and accounted for 84% of all seedlings (&lt;20 cm high) and 93% of all saplings (20–130 cm high), whereas Swiss stone pine (Pinus cembra L.) was less frequent (15% seedlings : 7% saplings). The density of mountain pine seedlings did not differ significantly between the disease centers and the adjacent forest, whereas mountain pine saplings were more frequent within the disease centers, indicating that growth from the seedling to the sapling stage was favoured in disease centers. There was significantly more dead wood and a greater diversity of plant species in the disease centers than in the adjacent forest. The results suggest that root-rot fungi slow down succession towards stands with a higher proportion of P. cembra by causing premature mortality of mountain pines and creating disease centers with dense mountain pine regeneration.

A comparison of two mountain gorilla habitats in Bwindi Impenetrable National Park, Uganda

AbstractBwindi Impenetrable National Park, Uganda, is a small protected area (331 km2) within which there is large climatic and altitudinal variation. Therefore we compared habitat types and forest composition between two locations to investigate differences that may influence ecological conditions for large mammals, including endangered mountain gorillas. We demonstrate that there is considerable intersite variation in habitat types and spatial and temporal availability of vegetation resources of which the most apparent are the differences in species composition of plants and fruit availability. Buhoma (the lower altitude site) has a greater diversity of plant species and higher tree and shrub densities, yet has a much lower density of herbaceous vegetation eaten by gorillas compared with Ruhija. Fruit availability is significantly higher throughout the year in Buhoma compared with Ruhija. Both sites exhibit seasonal variation in fruit availability although they do not follow the same seasonal pattern, perhaps because of inherent asynchronous phenological differences amongst individual tree species. The results of this study are important because distribution and abundance of both terrestrial herbaceous vegetation and fruit resources are believed to influence aspects of feeding ecology for large mammals.

Use of indigenous ecological knowledge of the Maasai pastoralists for assessing rangeland biodiversity in Tanzania

AbstractThis paper incorporates the indigenous ecological knowledge (IEK) of the Maasai pastoralists and ecological methods to assess effects of grazing and cropping on rangeland biodiversity at macro‐ and micro‐landscape scales in northern Tanzania. The joint surveys with pastoralists identified indicator plant species and their associations with micro‐landscapes and livestock grazing suitability (i.e. for cattle and small ruminant grazing), while traditional calf‐pasture reserves (alalili pl. alalilia) were evaluated for preservation of rangeland biodiversity. The macro‐landscapes comprising the cool high plateau (osupuko pl. isipuki) and montane forest highland (endim) were included in the survey. At micro‐landscape scales, the osupuko was classified into uplands (orkung'u), slopes (andamata) and dry valley bottomlands (ayarata). The micro‐landscapes were assessed in terms of herbaceous plant species and woody species richness and risks of soil erosion. Biodiversity varied at both the macro‐ and micro‐landscape scales and in accordance with the land‐use types. Greater plant species diversity and less erosion risks were found in the pastoral landscapes than in the agro‐pastoral landscapes. The calf‐grazing pastures had greater herbaceous species richness than the non‐calf pastures, which in turn had more woody species. The study concludes that the indigenous systems of landscape classification provides a valuable basis for assessing rangeland biodiversity, which ecologists should incorporate into ecological surveys of the rangelands in East Africa in the future.

DIFFERENTIAL RESOURCE USE BY PRIMATES AND HORNBILLS: IMPLICATIONS FOR SEED DISPERSAL

Arboreal frugivores, such as primates and hornbills, are important seed dis- persers for many tropical plant species, yet the degree to which they use the same resources is unknown. If primates and hornbills consume the same fruit species, they may be redundant in their roles as seed dispersers, and the loss of one of these taxa may be compensated for by the other. To examine resource use by tropical frugivores, we quantified the feeding habits of two hornbill species, Ceratogymna atrata and C. cylindricus, and five primate species, Colobus guereza, Lophocebus albigena, Cercopithecus pogonias, C. cephus, and C. nictitans, in the lowland rainforest of south-central Cameroon. Based on over 2200 feeding observations recorded between January and December 1998, we characterized the diets and estimated dietary overlap among frugivore species. Previous studies have cal- culated dietary overlap by counting the number of diet species that two animals share, often leading to inflated estimates of overlap. Our method incorporated the proportional use of diet species and fruit availability into randomization procedures, allowing a clearer as- sessment of the actual degree of overlap. This added complexity of analysis revealed that, although the diets of a hornbill and a primate species may have as many as 36 plant species in common, actual dietary overlap is low. These results suggested that there are distinct hornbill and primate feeding assemblages, with primates consuming a greater diversity of plant species and higher levels of nonfruit items like leaves and seeds. Using Correspon- dence Analysis, we also identified two primate assemblages, separated largely by degree of frugivory and folivory. In addition, we found that hornbills feed at significantly higher strata in the forest canopy and eat fruits of different colors than primates. Averaged across the year, overlap between groups (hornbill-primate) was significantly lower than combined within-group overlap (primate-primate and hornbill-hornbill), showing that primates and hornbills have dissimilar diets and are not redundant as seed dispersers. In equatorial Africa, primate populations face greater declines than hornbill populations because of hunting. It is unlikely that seed dispersal by hornbills will compensate for the loss of primates in maintaining forest structure.

Differential Resource Use by Primates and Hornbills: Implications for Seed Dispersal

Arboreal frugivores, such as primates and hornbills, are important seed dispersers for many tropical plant species, yet the degree to which they use the same resources is unknown. If primates and hornbills consume the same fruit species, they may be redundant in their roles as seed dispersers, and the loss of one of these taxa may be compensated for by the other. To examine resource use by tropical frugivores, we quantified the feeding habits of two hornbill species, Ceratogymna atrata and C. cylindricus, and five primate species, Colobus guereza, Lophocebus albigena, Cercopithecus pogonias, C. cephus, and C. nictitans, in the lowland rainforest of south-central Cameroon. Based on over 2200 feeding observations recorded between January and December 1998, we characterized the diets and estimated dietary overlap among frugivore species. Previous studies have calculated dietary overlap by counting the number of diet species that two animals share, often leading to inflated estimates of overlap. Our method incorporated the proportional use of diet species and fruit availability into randomization procedures, allowing a clearer assessment of the actual degree of overlap. This added complexity of analysis revealed that, although the diets of a hornbill and a primate species may have as many as 36 plant species in common, actual dietary overlap is low. These results suggested that there are distinct hornbill and primate feeding assemblages, with primates consuming a greater diversity of plant species and higher levels of nonfruit items like leaves and seeds. Using Correspondence Analysis, we also identified two primate assemblages, separated largely by degree of frugivory and folivory. In addition, we found that hornbills feed at significantly higher strata in the forest canopy and eat fruits of different colors than primates. Averaged across the year, overlap between groups (hornbill–primate) was significantly lower than combined within-group overlap (primate–primate and hornbill–hornbill), showing that primates and hornbills have dissimilar diets and are not redundant as seed dispersers. In equatorial Africa, primate populations face greater declines than hornbill populations because of hunting. It is unlikely that seed dispersal by hornbills will compensate for the loss of primates in maintaining forest structure.

Seasonal Variations in Sedimentation and Organic Content in Five Plant Associations on a Chesapeake Bay Tidal Freshwater Delta

Research on sedimentation processes in tidal freshwater marshes is lagging far behind that for salt marshes despite the importance of tidal freshwater systems for understanding impacts of watershed land use on estuarine habitats and water quality. From September 1996 to November 1997, biweekly sedimentation rates were monitored at 30 sites spanning 5 distinct habitat types across the intertidal zone of the tidal freshwater delta at the head of the Bush River tributary to upper Chesapeake Bay. These data were used to determine the spatio-temporal dynamics of sedimentation and erosion in the delta as well as the role of vegetation in seasonal to interannual physical processes. The observed mean net sedimentation rate was 1·00gcm−2yr−1, with a range of −74·15 to 145·2gcm−2yr−1. No relations between delta sedimentation rate and total precipitation, peak precipitation intensity, or watershed discharge were found over time. Instead, three distinct temporal regimes in the data predominantly reflected seasonal patterns in vegetation life cycle. With regard to spatial patterns, nonparametric statistical tests demonstrated that each habitat had a unique cycle of sedimentation and erosion. When sedimentation rates were multiplied by habitat area, the floating leaf habitat was found to have sequestered 6370tyr−1. In contrast, the high marsh lost 624tyr−1. These data indicate that the greater diversity of plant species in tidal freshwater marshes generates a wider variation in geomorphic processes than is possible for salt marshes.

An ecological comparison of spiders from urban and natural habitats in California

A comparative study of spider communities in urban, native, and semi-native habitats was conducted in 1980 in northern California. Selected biotic and abiotic factors thought to be responsible for observed differences in spider-community composition among habitats were investigated. Three backyards in the city of Berkeley comprised the urban study site. Plants found at this site included: Sequoia sempervirens, Juniperus sabina ‘Tamariscifolia,’ Hedera helix, Camellia japonica, and various annual and perennial flowers. Spider-community composition at the urban habitat consisted primarily of web-building spiders above ground level (aerial). Ground-surface spiders were fewer in number and species due to manipulation of the environment by homeowners. A relatively undisturbed coastal chaparral habitat, 7.7 km east of Berkeley (in Contra Costa County), was chosen to represent the native site. A limited number of plant species and structural diversity was characteristic of this habitat. Baccharis pilularis, Lupinus albifrons, Lupinus bicolor, and various grasses (Avena fatua, Bromus mollis, etc.) dominated the plant community at this study site, Briones Reservior. Total numbers and numbers of species of aerial spiders were low at this habitat. However, ground-surface spiders were more numerous, probably due to an abundance of prey. A semi-native habitat (Tilden Park) located between the urban and native habitats shared plant species with both these habitats. Plant species included both ornamental plants (Juniperus sabina, Pyracantha sp., and Prunus sp.) and native plants (Quercus agrifolia and Baccharis pilularis). The climate was most similar to the native habitat, although more humid. The aerial and ground-surface spider communities resembled the urban and native habitats, respectively. Plant architecture in conjunction with local climate influenced aerial spider community composition. A greater diversity of plant species provided a heterogeneous habitat for aerial spiders at both urban and semi-native habitats. The cooler and more humid climates at these sites reduced exposure to potentially limiting factors such as desiccation. Low diversity of plant architecture and a hot and dry climate restricted aerial spider numbers and species at the native site. Greater numbers of ground-surface spiders at the native and semi-native habitats were probably due to an abundance of prey, while owner manipulation of urban gardens negatively influenced ground-surface spider numbers and species at the urban habitat.