Patterns of rarity and taxonomic group size in plants

The objective of this research is to examine the extent to which phylogenetic and geographical drivers of rarity may interact to help us better predict distributions of rare taxa. This information is useful to conservation biologists when considering plans for the effective capture of biological diversity within reserve systems. We use 33 floras, distributed globally among five biomes, to assess pattern of rarity across taxonomic group size for plants. We show that small plant families (1-10 taxa) contain consistently fewer rare taxa than expected, while rare plants are proportionately over-represented in large plant families (>100 taxa). We also examine the distribution of species within families. The degree to which species are inequitably distributed among families varied systematically across floristic biomes. Mediterranean floras, in particular, are characterized by a greater than expected fraction of their species pool concentrated within large families, suggesting a high propensity for rarity simply by virtue of having a higher proportion of their constituent taxa within groups with a high likelihood of rarity. Finally, an analysis of a suite of floras using a common system of identifying rarity shows that the fraction of species within floras that are rare is predicted both by flora size and by a general metric (the Gini coefficient) of inequality among family sizes. Together, these patterns suggest a high degree of predictability in the distribution of rarity in plants that may reflect underlying natural speciation and extinction processes.     

Surface-soil responses to paraplowing of long-term no-tillage cropland in the Southern Piedmont USA

The type of conservation-tillage management employed could impact surface-soil properties, which could subsequently affect relationships between soil and water quality, as well as with soil C sequestration and greenhouse gas emissions. We determined soil bulk density, organic C and N fractions, plant-available N, and extractable P on Typic Kanhapludults throughout a 7-year period, in which four long-term (>10 years), no-tillage (NT) water catchments (1.3–2.7 ha each) were divided into two treatments: (1) continuation of NT and (2) paraplowing (PP) in autumn (a form of non-inversion deep ripping) with NT planting. Both summer [cotton (Gossypium hirsutum L.), maize (Zea mays L.), sorghum (Sorghum bicolor L. Moench), soybean (Glycine max L. Merr.)] and winter [wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.)] crops were NT planted throughout the study under each management system. Soil bulk density was reduced with PP compared with NT by as much as 0.15 Mg m⁻³, but the extent of reduction was inversely related to the time lag between PP operation and sampling event. Soil organic C became significantly enriched with time during this study under NT (0.49 Mg C ha⁻¹ year⁻¹), but not under PP, in which poultry litter was applied equivalent to 5.7 Mg ha⁻¹ year⁻¹ to all water catchments. Soil maintained a highly stratified depth distribution of organic C and N fractions and extractable P under both NT and PP. Inability to perform the PP operation in the last year of this study resulted in rapid convergence of soil bulk density between tillage systems, suggesting that PP had <1-year effectiveness on soil loosening. The high energy cost of PP (ca. 30 kW shank⁻¹) and the lack of sustained improvement in surface-soil properties put into question the value of PP for improving upon long-term NT management in sandy loam and sandy clay loam Ultisols of the Southern Piedmont USA, unless large effects on crop yield, water quality, or other ecosystem processes warrant its use.     

Conservation assessment and prioritization of areas in Northeast India: Priorities for amphibians and reptiles

This study combines niche modeling and systematic area prioritization using distribution data for 131 species of amphibians and reptiles from Northeast India and Burma, with two objectives: (i) to evaluate the performance of the current conservation area network in Northeast India with respect to the representation of amphibians and reptiles, and (ii) to identify potential areas for expanding the current conservation area network. In a two-step protocol, maximum entropy niche modeling was used to project species’ potential geographic occurrences, and the resulting probabilistic distribution data were used to prioritize areas with algorithms that maximize the representation of all species in minimal total area. The results provided a critical assessment of conservation priorities in this data-deficient region, and indicate the utility of combining niche modeling with systematic area prioritization in such situations. Many areas that had been overlooked in previous assessments were identified. Although the existing protected areas were found to be inadequate for representation of amphibian and reptile diversity, the prioritization results show that by targeting a minimal representation of 5% of the current total area suitable for each species, the gaps can be filled with a relatively modest (0.41%) increase in the current total area covered by the network. Extended analyses were also performed to assess the effects of putatively rare species on reserve selection, which showed that the inclusion of these taxa can change the prioritization solutions significantly. The prioritization results also highlight areas of Northeast India that warrant attention from future surveys.     

Spatial demographic and genetic consequences of harvesting within populations of the terrestrial orchid Cymbidium goeringii

Populations of many orchids, especially terrestrial species, have been rapidly decreasing due to mass collection by plant sellers and enthusiasts. Given the presumably negative demographic and genetic consequences, such anthropogenic activity should be taken into consideration for predicting ecological and evolutionary dynamics and for planning conservation strategies. To determine how recent human disturbance alters spatial demographic and population genetic processes, populations of the terrestrial orchid Cymbidium goeringii located in South Korea were examined to quantify the spatial distributions of individuals and genotypes with respect to three levels of disturbance: “disturbed” (four populations), “putatively disturbed” (two), and “undisturbed” (two). Undisturbed and putatively disturbed populations were found to possess significantly positive spatial clustering of individuals over a range of spatial scales. In contrast, disturbed populations exhibited little or no spatial aggregation, consistent with the selective removal of plants by collectors from higher density areas within these populations. Although overall genetic differentiation among populations was moderate and significant (F_ST = 0.082), levels of genetic diversity within populations were similar despite the different disturbance histories (mean H_e = 0.257-0.324). Spatial genetic autocorrelation analyses revealed that the undisturbed populations exhibited significant declines in kinship (F_ij) with distance, that mean kinship at interplant distances of ?4-6 m was significantly greater than zero and between plants ?0.5 m apart was in the range expected for first cousins to half-sibs. In contrast, only one putatively disturbed and one disturbed population exhibited significant declines in kinship with distance. These differences between disturbed versus putatively disturbed and undisturbed populations in the spatial distribution of individuals and genetic variation likely reflect the consequences of mass collections. Since these differences (and reduced population density) have important implications for future ecological and evolutionary trajectories, conservation managers of endangered terrestrial orchids may want to analyze the spatial distribution of individuals and their genotypes to infer whether a population with few individuals represents a natural state or the likely outcome of mass collection.     

Outcomes of longterm deciduous forest restoration in southwestern Ontario, Canada

At present, forest cover in southwestern Ontario, Canada, remains at less than 5% due to intensive agricultural and urban land use. Although much of the extant forest is increasingly protected by legislation, remnants continue to be degraded by the spread of non-native plant species, overgrazing, and recreational use. Some parks in the region have adopted management programs aimed at mitigating this degradation. Over the last 35 years, cottages and roads at Point Pelée National Park have been removed and sites either passively restored (i.e. road or cottage eliminated and vegetation allowed to regenerate) or actively restored (i.e. road or cottage eliminated, exotic vegetation removed, and native species planted). In 1994 and 1995, we assessed the effectiveness of restoration by comparing the understorey plant communities in 28 restored sites with those in less disturbed reference sites. There was a significant increase (P<0.0001) in the similarity of understorey plant communities between restored and reference sites as time-since-restoration increased. Soil moisture, canopy cover, distance to continuous forest, and site-shape all significantly affected plant species composition. Former road sites recovered significantly (P<0.05) more rapidly than former cottage sites, and the former lawns of passively restored cottage sites were the slowest to recover. Five years following active restoration, non-native ruderal species continued to dominate restored sites. The observed recovery of understorey plant communities in restored sites is attributed to their proximity to natural vegetation, and its function as a seed source. In some sites, recovery is substantial and, assuming present trajectories of change are maintained, we predict that recovery could occur in many mesic sites within the next 20 years. Restoration activity facilitates forest recovery and would appear to have a valuable function in mitigating ongoing conflicts between conservation and human use in this region.     

Indicator species and the problem of spatial inconsistency in nestedness patterns

The potential as indicators of species richness were investigated for 178 species belonging to six ecologically defined species groups (epiphytic bryophytes on nutrient-rich bark, epiphytic macrolichens on nutrient rich bark, pendant lichens on conifer trees, bryophytes on siliceous rocks, bryophytes on dead conifer wood, and polypore fungi on dead conifer wood), using species data from 0.25 ha plots from three different coniferous forest areas (ca. 200 ha each). A species was defined as a potential indicator species for a species group within a study area if its distribution was statistically significantly nested within the species-plot matrix ranked according to species richness, and if the plot frequency of the species was less than 25%.Only two species were identified as potential indicators within all three areas and on average ≈80% of the potential indicator species were lost from one area to another. The results indicate that inconsistency between areas in the species’ frequency distributions and their position in nested hierarchies may strongly reduce the general predictive power of indicator species of species richness, even if significantly nested patterns are found at the community level. We suggest that indicators related to amount and quality of habitats may be an alternative to lists of indicator species of species richness.     

Effects of anthropogenic land use on forest birds and butterflies in Subic Bay, Philippines

Despite the loss of 83% of native forests in the Philippines, little is known on the effects of this massive habitat loss and degradation on its forest biotas. This is a cause for concern because of the threat posed to the country’s large number of endemic taxa. To investigate the impacts of anthropogenic disturbance, forest birds and butterflies were surveyed in closed and open canopy forests, as well as suburban, rural and urban areas within the Subic Bay Watershed Reserve and Olongapo City in western Luzon. Measures of forest species richness and population densities for both taxa were similar in the two forest types, but showed different patterns in the other habitats. Indirect gradient analysis showed that forest bird species were positively correlated with vegetation variables (i.e., canopy cover, tree density, height to inversion and ground cover), while forest butterflies were not strongly correlated to any of the measured habitat variables. Community composition of birds in forests was distinct from those in modified habitats, while butterfly communities were more similar. A simulation showed that canopy cover of 60% or higher was required by 24 of the 26 bird species that were sensitive to canopy loss. Endemicity and nesting strata were the significant predictors of vulnerability to habitat disturbance for birds, while endemicity and larval hostplant specificity were significant for butterflies. Both taxa were negatively affected by anthropogenic disturbance but may respond to different components in the habitat (i.e., structure and resources), and thus cannot be used as surrogates of each other. Conservation of forests with contiguous canopy cover should be prioritized, and more ecological research is needed to improve the knowledge on the effects of disturbance on Philippine biodiversity.     

High human density in the irreplaceable sites for African vertebrates conservation

The identification of priority sites that ensure the achievement of conservation goals is key to direct conservation efforts. An estimation of the level of vulnerability of each priority area allows the identification of sites that need urgent conservation action. We present a systematic reserve selection for 1654 African mammals and amphibians that uses habitat suitability models as estimates of the area occupied by each species. These are based on the geographic range and habitat preferences for each species, which we collected in the framework of the World Conservation Union (IUCN) Global Amphibian Assessment and IUCN Global Mammal Assessment. Our results showed that in addition to existing protected areas, approximately 2.8 million km² of land is irreplaceable to achieve the protection of 10% of the area occupied by all amphibians and mammals. This figure is higher than previous estimates from other studies. Most irreplaceable sites are located in the sub-Saharan region. More than half (55%) of the irreplaceable sites have high human population density; for only 17% the human population density is low. African amphibians and mammals have therefore to be conserved in densely populated areas where innovative management policies will be required to accommodate conservation successfully.     

Large-scale habitat associations of birds in lowland Iceland: Implications for conservation

Iceland is responsible for many internationally important populations of breeding bird species, yet very little is currently known about how these species use the habitats available to them. Lowland areas of Iceland, in particular, have undergone significant landscape changes over the last century, such as widespread drainage of wetlands and conversion to agriculture, changes in grazing pressure and recently, extensive afforestation. The impact of these changes on breeding bird species will depend on the relative importance of different habitats for each species, and the threats facing those habitats. Here we report the results of a large-scale survey of the factors influencing patterns of habitat selection of eight populations of Charadriiform bird species throughout lowland Iceland; oystercatcher Haematopus ostralegus, golden plover Pluvialis apricaria, dunlin Calidris alpina, snipe Gallinago gallinago, whimbrel Numenius phaeopus, black-tailed godwit Limosa limosa, redshank Tringa totanus and arctic skua Stercorarius parasiticus. Ordination analyses and multiple logistic regression models are constructed to explore the components of habitats that influence the distribution of these species. Five of the eight species analysed showed significant preferences for lowland wetland habitats and four significantly selected areas containing wet features such as pools and high water tables. These results allow us to identify future conflicts in land use that are likely to result from government-supported large-scale afforestation of lowland areas and hydro-electric developments.     

不同耕作方式对中国东北黑土有机碳的短期影响

A tillage experiment, consisting of moldboard plow （MP）, ridge tillage （RT）, and no-tillage （NT）, was performed in a randomized complete block design with four replicates to study the effect of 3-year tillage management on SOC content and its distribution in surface layer （30 cm） of a clay loam soil in northeast China. NT did not lead to significant increase of SOC in topsoil （0-5 cm） compared with MP and RT; however, the SOC content in NT soil was remarkably reduced at a depth of 5-20 cm. Accordingly, short-term （3-year） NT management tended to stratify SOC concentration, but not necessarily increase its storage in the plow layer for the soil.