The distribution of disturbance-dependent rare plants in a coastal Massachusetts sandplain: Implications for conservation and management

Rare plants in coastal New England sandplains are often restricted to anthropogenically disturbed sites including plowed and mowed firelanes at the Manuel F. Correllus State Forest on Martha’s Vineyard. Little is known about pre-colonial rare plant habitat or how modern management impacts these species. To understand the factors influencing rare plant distribution, we examined the influence of vegetation structure, species composition, environmental characteristics and disturbance history on rare plant populations and potential natural habitat in the 2100-ha Forest. We sampled >100, 100 m² plots - in firelanes and forested/shrubland areas - and conducted extensive searches for rare plants.Linum intercursum and Scleria pauciflora var. caroliniana were frequent in firelanes including in recently plowed areas, whereas Nabalus serpentarius, Sisyrinchium fuscatum, and Aristida purpurascens generally occurred in isolated, locally-abundant patches in firelanes not plowed for many decades. The former group may be characterized by an ability to rapidly establish following disturbances while the latter may take longer to establish and develop large populations. In some respects, rare plants were associated with environmental conditions reflecting the disturbance histories of sites they occupied (e.g., L. intercursum with lower duff depth and N. serpentarius with greater litter cover/depth).In forests and shrublands undisturbed for decades, rare plants only occurred on well-worn paths. Although scrub oak stands supported conditions more similar to those found in firelanes than other native vegetation types, disturbances - far more severe than those in forests/shrublands of the past century - are probably required to create suitable rare plant habitat in sandplain forests and shrublands.     

Historical influences on the vegetation and soils of the Martha’s Vineyard, Massachusetts coastal sandplain: Implications for conservation and restoration

Both disturbance history and previous land use influence present-day vegetation and soils. These influences can have important implications for conservation of plant communities if former disturbance and land use change species abundances, increase colonization of nonnative plant species or if they alter soil characteristics in ways that make them less suitable for species of conservation interest. We compared the plant species composition, the proportion of native and nonnative plant species, and soil biogeochemical characteristics across seven dominant land use and vegetation cover types on the outwash sandplain of Martha’s Vineyard that differed in previous soil tillage, dominant overstory vegetation and history of recent prescribed fire. The outwash sandplain supports many native plant species adapted to dry, low nutrient conditions and maintenance of native species is a management concern. There was broad overlap in the plant species composition among pine (Pinus resinosa, P. strobus) plantations on untilled soils, pine plantations on formerly tilled soils, scrub oak (Quercus ilicifolia) shrublands, tree oak (Q. velutina, Q. alba) woodlands, burned tree oak woodlands, and sandplain grasslands. All of these land cover categories contained few nonnative species. In contrast, agricultural grasslands had high richness and cover of nonnative plants. Soil characteristics were also similar among all of the woodland, shrubland and grassland land cover categories, but soils in agricultural grasslands had higher pH, extractable Ca²⁺ and Mg²⁺ in mineral soils and higher rates of net nitrification. The similarity of soils and significant overlap in vegetation across pine plantations, scrub oak shrublands, oak woodlands and sandplain grasslands suggests that the history of land use, current vegetation and soil characteristics do not pose a major barrier to management strategies that would involve conversion among any of these vegetation types. The current presence of high cover of nonnative species and nutrient-enriched soils in agricultural grasslands, however, may pose a barrier to expansion of sandplain grasslands or shrublands on these former agricultural lands if native species are not able to outcompete nonnative species in these anthropogenically-enriched sites.     

Urbanization and riparian forest woody communities: Diversity, composition, and structure within a metropolitan landscape

Understanding how urban land-use structure contributes to the abundance and diversity of riparian woody species can inform management and conservation efforts. Yet, previous studies have focused on broad-scale (e.g., urban to exurban) land-use types and have not examined more local-scale changes in land use (e.g., the variation within “urban”), which could be important in urban areas. In this paper we examine how local-scale characteristics or fine-scale urban heterogeneity affect(s) the diversity, composition, and structure of temperate woody riparian vegetation communities in the highly urbanized area of Cincinnati, Ohio, USA. We use an information-theoretic approach to compare vegetation models and canonical correspondence analyses to compare species responses to urban variables. We found that urban riparian areas can harbor a high diversity of native canopy and shrub species (38 and 41, respectively); however, native and exotic woody plant species responded differently to urbanization. Exotic canopy species increased with the level of urbanization while native canopy and understory species declined. Understory species diversity displayed a greater response to urbanization than did canopy diversity, suggesting temporal lags in canopy response to disturbances associated with present and recent land-use changes. Certain native and exotic woody species represent ecological indicators of different levels of urbanization. Native species characteristic of pre-European settlement conditions were restricted to the wide riparian forests with little urban encroachment. Several native early-successional species appear tolerant to urbanization. Two exotic species, the tree Ailanthus altissima and the shrub Lonicera maackii, were the most abundant and ubiquitous woody species and appear to exploit urban disturbances. These exotic species invasions have the potential to modify forest composition and ecological function of urban riparian systems. In addition, altered hydrology may be a contributing factor as canopy and understory stem density of high-moisture-requiring species decreased with an increase in impervious surface and grass cover and with proximity to roads and railroads. In the face of urbanization, maintaining wide riparian forests and limiting building, road and railroad development within these areas may help reduce the invasion of exotic species and benefit hydrological function in temperate riparian areas.     

Moreton Bay, Queensland, Australia: an example of the co-existence of significant marine mammal populations and large-scale coastal development

Recent analyses assert that large marine vertebrates such as marine mammals are now ‘functionally or entirely extinct in most coastal ecosystems’. Moreton Bay is a large diverse marine ecosystem bordering the fastest growing area in Australia. The human population is over 1.6 million and increasing yearly by between 10% and 13% with resultant impacts upon the adjoining marine environment. Nonetheless, significant populations of three species of marine mammals are resident within Moreton Bay and a further 14 species are seasonal or occasional visitors. This paper reviews the current and historical distributions and abundance of these species in the context of the current management regime and suggests initiatives to increase the resilience of marine mammal populations to the changes wrought by the burgeoning human population in coastal environments.     

Endangered species management requires a new look at the benefit of fire: The Cape Sable seaside sparrow in the Everglades ecosystem

Although disturbance processes play important roles in maintaining habitat heterogeneity, the potential effects of such processes on rare or endangered species is virtually unknown and difficult to test. We use an unplanned fire, which burned half of a long-term study plot, as a natural experiment to test the effects of fire on the federally endangered Cape Sable seaside sparrow in Everglades National Park. By implementing a before-after-control-impact study design we determine the mechanistic link between fire and demography of this endangered sparrow. Our results show that while the sparrow tolerates fire, neither sparrow density nor nesting success are enhanced by fire, which runs contrary to the current paradigm in which sparrows are expected to benefit and therefore require fire for persistence. Our results caution against the assumption that occupancy of disturbance-prone habitat automatically suggests dependence on disturbance. Land managers must prevent large and frequent fires from burning occupied sparrow habitat to best manage for the species. Moreover, it is imperative that more studies focus on the effects of disturbance processes on rare and endangered species in order to prevent further loss of biodiversity.     

Recovery of native plant communities after the control of a dominant invasive plant species, Foeniculum vulgare: Implications for management

The control and/or removal of a dominant invasive species is expected to lead to increases in native species richness and diversity. Small pilot studies were performed on Santa Cruz Island (SCI), California, in the early 1990s to test the efficacy of different methods on the control of Foeniculum vulgare (fennel) and management’s effects on native species recovery. We chose a treatment that showed significant native species recovery, applied it at the landscape scale, and followed its effects on fennel infested plant communities. We tested the hypothesis that results from small-scale studies translate to the landscape level. We found that although the control of fennel translated from the small to landscape scale, decreasing from an average of 60% to less than 3% cover, native species recovery did not occur in the landscape study as it did in the pilot studies. Invasive fennel cover was replaced by non-native grass cover over time. Unexpectedly, fennel cover in untreated fennel plots decreased significantly (though not as drastically) from over 60% cover to just under 40% cover while native species richness in untreated areas increased significantly. The correlation between precipitation and changes in native and non-native species richness and abundance in this study imply that changes in species abundances were highly correlated with environmental fluctuations. The lack of a native seedbank and the accumulation of non-native grass litter likely prevented the recovery of native species in treated areas. Greater vertical complexity found in fennel communities, which increased visitation by frugivorous birds and likely increased native seed dispersal, may have been responsible for the increase in native species richness in the untreated areas. These results suggest that successful invasive species control and native species recovery experiments conducted at small scales may not translate to the landscape level, and active restoration should be an organic component of such large-scale projects.     

Binding,fractionation, and distribution of Cs,Co, and Sr in a US coastal soil under saturated and field capacity moisture regimes

Purpose

The concerns of the public on safe handling of nuclear energy power facilities have increased due to the recent nuclear plant accidents in Japan and others. Cesium, cobalt, and strontium are a few of the major radionuclides released from nuclear power plant accidents. The objectives of this study are to investigate binding, distribution, fractionation, and transformation of cesium (Cs), cobalt (Co), and strontium (Sr) in a US coastal soil under saturated paste (SP) and field capacity (FC) moisture regimes.

Materials and methods

There are four major nuclear power plants in the coast region around the northern Gulf of Mexico where coastal soil often undergoes soil moisture change. A coastal soil was taken from the middle region of these major nuclear power plants and spiked with different concentrations of cesium, cobalt, and strontium salts. The sequential selective dissolution technique was used to investigate the transformation and fractionations of these metals in the coastal soils affected by moisture regime, a key factor in the coastal environment.

Results and discussion

The adsorption kinetics showed that both Co and Sr reached the adsorption plateau even after 5 h of adsorption, indicating a fast initial adsorption process in the coastal soil. Cesium, cobalt, and strontium were dominantly presented in the soluble and exchangeable form (EXC) (Cs?>?Co and Sr), which linearly increased with the addition levels, possessing the high bioavailability, mobility, and ecotoxicity. Saturated regime significantly reduced the soluble and exchangeable form compared to field capacity moisture regime.

Conclusions

The current study provides the fundamental understanding for designing the cost-effective remediation technology to remediate these metals in coastal soil by targeting on the soluble and exchangeable forms and better prepare the USA for future potentially nuclear power plant accidents.

     

Short and medium-term evolution of a coastal sector in Cadiz,SW Spain

The present paper is a combined study on the medium and short-term evolution of the littoral between Chipiona and Rota (SW Spain). The analysis of coastal evolution over a period of 24 years (i.e. medium-term), was carried out using six, well temporally spaced, photogrammetric flights. Cliff top and dune toe were used as shoreline indicators to solve problems related to the use of watermark in tidal environments. Short-term littoral variations were monitored monthly by means of an electronic theodolite over a period of 2 years. The width variations of the dry beach were surveyed by always using a constant, average value for the mean sea level position derived from the numerous surveys carried out. The obtained data was representative of both seasonal and annual variations.     

Ecosystem UV-B experiments in terrestrial communities: a review of recent findings and methodologies

Ecosystem-level UV-B experiments have revealed a variety of responses in terrestrial communities. These include decreases in the growth of some plant species (usually small changes but occasionally >25%), both decreases and increases in herbivory, occasional altered decomposition patterns, changes in populations of fungi and invertebrates, and morphological changes in the growth patterns of mosses. These field experiments have been pursued both with solar UV-B exclusion using selective filters and with supplementation of UV-B using lamps. For UV-B-exclusion studies it is critical that the UV-B-excluding and UV-B-transmitting filters pass the same amount of photosynthetically active radiation (PAR, 400–700 nm) and also infrared. Canopy photosynthesis models indicate that even small differences in PAR transmittance can, under many circumstances, have significant effects on plant carbon gain. It is also important that filters in UV-B-exclusion studies allow precipitation to pass uniformly to the plots unless there is some form of irrigation underneath the filters. For UV-B-supplementation studies with lamps, many factors are involved in the realism of the ozone depletion simulation. We believe the major lamp-system error is excessive supplementation of UV-B by timer-controlled lamps when weather conditions (primarily clouds) decrease ambient solar UV-B irradiance. The choice of biological spectral weighting functions (BSWF) used in adjusting lamp flux is also critical in determining the level of ozone depletion simulated. In addition, shading by the lamp arrays influences plant growth and becomes particularly important when BSWF with substantial weighting in the UV-A are employed.     

Homogenization of ant communities in mediterranean California: The effects of urbanization and invasion

In coastal California, the invasive Argentine ant (Linepithema humile) displaces nearly all above ground foraging native ant species. The loss of native ants following invasion by Argentine ants homogenizes these faunas; natural habitats invaded by L. humile have lower beta diversity compared to comparable uninvaded areas. Argentine ant abundance in the seasonally dry mediterranean environments of this region correlates strongly and positively with soil moisture. For this reason, the displacement of native ants across natural and artificial moisture gradients often resembles an edge effect, the magnitude of which is inversely proportional to the suitability of the physical environment from the perspective of L. humile. The direct effects of Argentine ant invasions in natural environments are therefore amplified by inputs of urban and agricultural run off. Indirect ecological effects of these invasions arise from the loss of large-bodied ants, arid adapted ants, and behavioral repertoires unique to particular native ant species. Further research is needed to quantify how these aspects of functional homogenization affect invaded communities. The close association between L. humile and moist soils suggests that, at least in arid regions, control strategies might be aimed at reducing urban run off in order to maintain functionally diverse communities of native ants.     

Soil organic carbon as affected by land use in young and old reclaimed regions of a coastal estuary wetland,China

Soil organic carbon (SOC) and selected soil properties were measured in fringe and ditch marshes and cropland of old and young reclaimed areas in a subtropical estuary in China in order to investigate the effects of land use and reclamation history on SOC. The results show that after the conversion of wetlands to cropland, a longer reclamation history (>20 yr) resulted in greater soil bulk density, salinity, clay and silt, and lower soil moisture, SOC and sand content, whereas a shorter reclamation history (<20 yr) induced smaller values for soil pH, moisture and sand. Ditch marshes had greater average SOC in the top 50 cm than fringe marshes and cropland. SOC decreased generally down soil profiles from 0 to 50 cm in depth, except for the obvious accumulation of SOC in deeper soils from old fringe and young ditch marshes. Ditch marshes had the greatest SOC densities in the top 50 cm in both regions compared to the other land uses. SOC densities in the top 50 cm were less in croplands than in fringe marshes in the young region, while there were no significant differences between them in the older one. Except for cropland, SOC densities in the top 50 cm of the fringe or ditch marshes in the old region were not significantly different from those in the young region. SOC in both regions was reduced by 13.53 × 10⁴ t (12.98%) in the top 50 cm of the marshes after conversion to cropland, whereas the regional SOC storage increased by 29.25 t when ditch marshes were included. The results from regression analysis show that bulk density and soil moisture significantly influenced SOC. The total SOC stored in both ditch marshes and croplands was higher compared to fringe marshes. The regional SOC storage in the top 50 cm was not reduced after reclamation due to C accumulation in the ditch marshes. The regional effects of cultural practices should be taken into account in devising strategies for managing soils in coastal wetlands, particularly in the developing world.     

Arbuscular mycorrhizal fungal communities in changing environments: The effects of seasonality and anthropogenic disturbance in a seasonal dry forest

The landscape of Mexican seasonal dry forests is affected by various periodic (long and drastic drought) and random (elimination of the forest coverage for agricultural purposes) disturbance events. The community of arbuscular mycorrhizal fungi (AMF) responds to these changes, sporulating and reducing its activity during the dry season, and slowly reestablishing itself following abandonment of cultivated fields. To determine the dynamics of the AMF community in response to natural phenomena and anthropogenic disturbances, we collected soil samples during the wet and dry seasons from plots with different time periods since abandonment of agricultural activity, categorized as early (less than 5 years), middle (11–23 years), and late (over 30 years) age plots. From each plot, AMF spores were isolated and identified in order to estimate abundance, richness and diversity. In addition, the number of infective propagules and value of mycorrhizal inoculum potential were calculated for each plot. Twenty-three species were recorded, for which Glomeraceae and Acaulosporaceae were the most commonly represented families. Significant differences were found in AMF species richness among plots and seasons and the diversity index of AMF was higher than 1.0 in most cases. There were no significant differences in spore abundance. Viable propagules were observed in all soil samples, with fluctuations relating mainly to time since abandonment. Overall, seasonality has a strong influence on AMF diversity but not on AMF infectivity, while time since abandonment had a more important impact.     

The role of ants in conservation monitoring: If, when, and how

Ants are increasingly being recognized as useful tools for land managers to monitor ecosystem conditions. However, despite an abundance of studies on ant responses to both environmental disturbance and land management techniques, an analysis of the practice and value of including ants in monitoring is lacking. Consequently, conservation managers are left with little guidance as to if, when, and how ants can be used to assess conservation activities. Based on our review of approximately 60 published studies, we outline five areas where ants provide valuable information for management-based monitoring: (1) to detect the presence of invasive species, (2) to detect trends among threatened or endangered species, (3) to detect trends among keystone species, (4) to evaluate land management actions, and (5) to assess long-term ecosystem changes. We also discuss practical considerations when designing a monitoring framework for ants, including appropriate methods, taxonomic resolution for sampling, and spatial and temporal scale. We find that when integrated with management goals, monitoring ants can provide information over the short-term on topics such as the status of invasive or keystone species, as well as over longer time frames, for instance the impact of climate change. Overall, we conclude that ants merit monitoring based on their inherent ecological qualities, independent of any “indicator” attributes they might have.     

The roles of habitat features, disturbance, and distance from putative source populations in structuring alien plant invasions at the urban/wildland interface on the Cape Peninsula, South Africa

Natural areas are becoming increasingly fragmented and embedded in an urban matrix. Natural and semi-natural areas at the urban/wildland interface are threatened by a variety of ‘edge effects’, and are especially vulnerable to invasion by introduced plants, with suburban gardens acting as significant sources of alien propagules. Urban/wildland interfaces also provide access for humans, leading to various types of disturbance. Alien plant invasions are one of the biggest threats facing remaining natural areas on the Cape Peninsula, South Africa. The area provides an ideal opportunity to study the dynamics of invasions at the urban/wildland interface, since the largest natural area, the Table Mountain National Park (TMNP), is surrounded by the city of Cape Town. We explored invasion patterns in Newlands Forest (a small section of the TMNP) and detailed the roles of habitat features and distance from putative source populations in three main habitat types: natural Afromontane forest, riverine woodland habitats, and plantations of exotic pines (Pinus radiata and P. pinaster). We also examined the role of disturbance in driving invasions in two of these habitat types (Afromontane forest and pine plantations). We hypothesized that alien richness and alien stem density would decrease with distance from the urban/wildland interface, and that alien richness and alien stem density would increase with increasing levels of human disturbance.Distance from putative source populations and levels of anthropogenic disturbance influenced alien richness in Newlands Forest but not alien stem density. Alien richness decreased significantly with distance from presumed sources in the pine habitat, and increased significantly with disturbance in the forest habitat. Percentage overstorey cover and soil pH were important environmental variables associated with alien plant species. A socio-economic approach is discussed as being the most effective approach to the management and prevention of alien plant species in Newlands Forest.     

Lizards and landscapes: integrating field surveys and interviews to assess the impact of human disturbance on lizard assemblages and selected reptiles in a savanna in South Africa

Habitat degradation through over-grazing and wood collection is especially prevalent in developing countries such as South Africa. As human populations expand and the demand for land increases, the traditional idiom of setting aside protected areas for conservation is insufficient and assessment and protection of diversity outside these areas is needed. We assessed the impact of land use on lizard assemblages in communal rangelands in South Africa by comparing abundance, species richness and species diversity between degraded communal lands with a protected area. We first quantified vegetation differences between the study areas and found marked differences. Communal lands had significantly fewer large trees and less ground cover. Contrary to prediction, we found no evidence that any species of lizard was negatively affected by habitat disturbance. Some species were more common in communal lands, and species richness and diversity were also higher using certain sampling techniques. Terrestrial diversity was likely enhanced due to the preference of many terrestrial lizards for open, sparsely grassed areas. We discuss other reasons for increased diversity such as the intermediate disturbance hypothesis and/or reduced numbers of predators and competitors. We also conducted surveys of households and traditional healers to investigate the relationship between human uses of reptiles and abundance. The predominant users of reptiles were traditional healers. The most commonly used species were not encountered in our field surveys, and respondents indicated that they appeared to be declining. Our results emphasise the importance of integrating local knowledge into biodiversity assessment and conservation planning. Although we did not identify a negative impact of disturbance on lizard communities, community structure was different and this likely influenced ecosystem integrity and function in some way.     

Long-term influence of mowing on population dynamics in the rare orchid Dactylorhiza lapponica: The importance of recruitment and seed production

Many orchids are currently red-listed due to changes in land use, and their future persistence will depend on management. Traditional land use like mowing is believed to favour orchids through increased survival and reproduction of established individuals, but the lack of data connecting their complex life cycle presently limits our ability to evaluate effects of management. Here we used data from 16 years of demographic monitoring to study how mowing affects population dynamics in two populations of the rare orchid Dactylorhiza lapponica. Both populations were characterized by long-lived individuals, low adult mortality and high seedling mortality. The traditional regime of mowing every second year strongly increased recruitment and reduced seed production in both populations, but had moderate effect on adult survival, growth rate and flowering probability. Population growth rate was positive for all population × treatment combinations. Traditional mowing significantly increased growth rate in both populations, and LTRE-analyses revealed that this primarily was a result of increased recruitment. The results indicate that demographic rates commonly associated with orchid persistence may be insensitive to traditional management, and underscores the importance of seed production and recruitment to maintain population growth in this long-lived species. The combination of low establishment success and no seed bank makes D. lapponica dependent on high seed input. Our results suggest that D. lapponica would benefit most from traditional mowing performed after seed dispersal in the study areas, but also suggest a high probability of future survival in the absence of mowing.     

Estimating occupancy of a data deficient mammalian species living in tropical rainforests: Sun bears in the Kerinci Seblat region, Sumatra

Tropical mammals represent some of the most threatened species, but also the least known because they tend to be difficult to study. To objectively evaluate the conservation status of these species, standardized methods are urgently required. The sun bear Helarctos malayanus is a case in point: it is cryptic, difficult to detect and consequently classified on the IUCN Red List as Data Deficient, and the highest priority for bear conservation research. In this study, we apply a detection/non-detection sampling technique using camera trap data with environmental covariates to estimate sun bear occupancy from three tropical forest study areas with different levels of degradation and protection status in Sumatra. Sun bear detections, and encounter rates, were highest in one of the primary forest study areas, but sun bear occupancy was highest in the degraded forest study area. Whilst, sun bears were recorded at a greater proportion of camera placements in degraded forest, these records were often on only one occasion at each placement, which greatly increased the final occupancy estimate. Primary forests with their large fruiting trees undoubtedly represent good sun bear habitat, but our results indicate that degraded forest can also represent important habitat. These forests should therefore not be considered as having limited conservation value and assigned to other uses, such as oil palm production, as has previously happened in Sumatra. Estimating occupancy between years will yield information on the population trends of sun bears and other tropical mammals, which can be used to provide more reliable conservation assessments.     

Commonness and rarity in plants with special reference to the Sheffield flora Part I: The identity,distribution and habitat characteristics of the common and rare species

By reference to extensive vegetation surveys the habitats of common and rare herbaceous plants and small (<1 m) woody species have been compared for the Sheffield region of Central England.Common species are frequent at sites of high fertility, are strongly represented in habitats which are heavily disturbed or of recent origin and generally have a wide geographical and ecological range in the Sheffield region and within Britain as a whole.Many of the rare species are restricted to the lowland half of the region and most of the species which have become extinct from the region in the recent past were associated with lowland agricultural areas where the pressures of changing land use are greatest. Rare species are concentrated within less fertile sites, particularly those with calcareous soils, and they are often present in species-rich vegetation in ancient habitats. Many rare species have a narrow ecological range, some appear restricted to ‘intermediate’ habitats (either ecoclines or ecotones) and a high proportion are near the northern limit of their geographical range.No single ecological characteristic is totally diagnostic of either common or rare species. Most of the differences between common and rare species in the Sheffield region may be interpreted in terms of the availability of suitable habitats within the region with common species occupying common, and rare species less common, habitats.     

The challenge of maintaining Atlantic forest biodiversity: A multi-taxa conservation assessment of specialist and generalist species in an agro-forestry mosaic in southern Bahia

Recent developments have highlighted the importance of forest amount at large spatial scales and of matrix quality for ecological processes in remnants. These developments, in turn, suggest the potential for reducing biodiversity loss through the maintenance of a high percentage of forest combined with sensitive management of anthropogenic areas. We conducted a multi-taxa survey to evaluate the potential for biodiversity maintenance in an Atlantic forest landscape that presented a favorable context from a theoretical perspective (high proportion of mature forest partly surrounded by structurally complex matrices). We sampled ferns, butterflies, frogs, lizards, bats, small mammals and birds in interiors and edges of large and small mature forest remnants and two matrices (second-growth forests and shade cacao plantations), as well as trees in interiors of small and large remnants. By considering richness, abundance and composition of forest specialists and generalists, we investigated the biodiversity value of matrix habitats (comparing them with interiors of large remnants for all groups except tree), and evaluated area (for all groups) and edge effects (for all groups except trees) in mature forest remnants. Our results suggest that in landscapes comprising high amounts of mature forest and low contrasting matrices: (1) shade cacao plantations and second-growth forests harbor an appreciable number of forest specialists; (2) most forest specialist assemblages are not affected by area or edge effects, while most generalist assemblages proliferate at edges of small remnants. Nevertheless, differences in tree assemblages, especially among smaller trees, suggest that observed patterns are unlikely to be stable over time.     

Land abandonment,landscape evolution,and soil erosion in a Spanish Mediterranean mountain region: The case of Camero Viejo

The Spanish Mediterranean mountains have played an important social and economic role for many centuries. However, since the 1950s these regions have been considered of little economic interest, and this has led to the abandonment of villages, reduced productive activity, and significant changes in the landscape. In the last 50 years the Camero Viejo region (Iberian System, northeast Spain) has been subject to these changes, and was selected as our study area. Landscape evolution and soil erosion, as a result of agricultural abandonment, were studied using different analysis techniques: photointerpretation, geographic information systems and rainfall simulation. The results showed that a large proportion of previously cultivated land has been subject to plant recolonization processes. From 1956 to 2001, woodlands area increased from 10·1 per cent to 37 per cent, and scrubland increased from 42 per cent to 60 per cent. Changes in landscape structure in the same period suggest that the Camero Viejo is in a transitional stage from a highly humanized landscape to a more natural landscape. Although plant cover expansion is evident on most Camero Viejo hillslopes, in some terraced areas erosion processes are active. The generalized abandonment of agricultural terraces has favored the collapse of the stone walls of the terraces, with sliding of the soil. Surface runoff on abandoned terraces is also important. These erosion processes are related to the hydrological functioning of slopes following abandonment, neglect, and in some areas the intensification of grazing. Terrace destruction has a negative impact on the landscape and represents the loss of fertile soils. Landscape diversity should be preserved as an essential element of the economic potential of the Camero Viejo. Copyright © 2010 John Wiley & Sons, Ltd.