Changes in Arthropod Assemblages along a Wide Gradient of Disturbance in Gabon

Abstract: Searching for indicator taxa representative of diverse assemblages, such as arthropods, is an important objective of many conservation studies. We evaluated the impacts of a wide gradient of disturbance in Gabon on a range of arthropod assemblages representing different feeding guilds. We examined 4 × 10⁵ arthropod individuals from which 21 focal taxa were separated into 1534 morphospecies. Replication included the understory of 3 sites in each of 4 different stages of forest succession and land use (i.e., habitats) after logging (old and young forests, savanna, and gardens). We used 3 complementary sampling methods to survey sites throughout the year. Overall differences in arthropod abundance and diversity were greatest between forest and open habitats, and cleared forest invaded by savanna had the lowest abundance and diversity. The magnitude of faunal differences was much smaller between old and young forests. When considered at this local scale, anthropogenic modification of habitats did not result in a monotonous decline of diversity because many herbivore pests and their associated predators and parasitoids were abundant and diverse in gardens, where plant productivity was kept artificially high year‐round through watering and crop rotation. We used a variety of response variables to measure the strength of correlations across survey locations among focal taxa. These could be ranked as follows in terms of decreasing number of significant correlations: species turnover > abundance > observed species richness > estimated species richness > percentage of site‐specific species. The number of significant correlations was generally low and apparently unrelated to taxonomy or guild structure. Our results emphasize the value of reporting species turnover in conservation studies, as opposed to simply measuring species richness, and that the search for indicator taxa is elusive in the tropics. One promising alternative might be to consider “predictor sets” of a small number of taxa representative of different functional groups, as identified in our study.     

Savanna tree density, herbivores, and the herbaceous community: bottom-up vs. top-down effects

Herbivores choose their habitats both to maximize forage intake and to minimize their risk of predation. For African savanna herbivores, the available habitats range in woody cover from open areas with few trees to dense, almost-closed woodlands. This variation in woody cover or density can have a number of consequences for herbaceous species composition, cover, and productivity, as well as for ease of predator detection and avoidance. Here, we consider two alternative possibilities: first, that tree density affects the herbaceous vegetation, with concomitant "bottom-up" effects on herbivore habitat preferences; or, second, that tree density affects predator visibility, mediating "top-down" effects of predators on herbivore habitat preferences. We sampled sites spanning a 10-fold range of tree densities in an Acacia drepanolobium-dominated savanna in Laikipia, Kenya, for variation in (1) herbaceous cover, composition, and species richness; (2) wild and domestic herbivore use; and (3) degree of visibility obstruction by the tree layer. We then used structural equation modeling to consider the potential influences that tree density may have on herbivores and herbaceous community properties. Tree density was associated with substantial variation in herbaceous species composition and richness. Cattle exhibited a fairly uniform use of the landscape, whereas wild herbivores, with the exception of elephants, exhibited a strong preference for areas of low tree density. Model results suggest that this was not a response to variation in herbaceous-community characteristics, but rather a response to the greater visibility associated with more open places. Elephants, in contrast, preferred areas with higher densities of trees, apparently because of greater forage availability. These results suggest that, for all but the largest species, top-down behavioral effects of predator avoidance on herbivores are mediated by tree density. This, in turn, appears to have cascading effects on the herbaceous vegetation. These results shed light on one of the major features of the "landscape of fear" in which African savanna herbivores exist.     

Effects of Restoring Oak Savannas on Bird Communities and Populations

Abstract:  Efforts to restore and maintain oak savannas in North America, with emphasis on the use of prescribed fire, have become common. Little is known, however, about how restoration affects animal populations, especially those of birds. I compared the breeding densities, community structure, and reproductive success of birds in oak savannas maintained by prescribed fire (12 sites) with those in closed-canopy forests (13 sites). All sampling was conducted in Illinois (U.S.A.). Of the 31 bird species analyzed, 12 were more common in savannas, 14 were not affected by habitat structure, and 5 were more common in forest habitat. The species favored by disturbance and restoration included Northern Bobwhites ( Colinus virginianus ), Mourning Doves (  Zenaida macroura ), Red-headed Woodpeckers (  Melanerpes erythrocephalus ), Indigo Buntings (  Passerina cyanea ), and Baltimore Orioles ( Icterus galbula ). Those more common in closed-canopy forest included Ovenbirds ( Seiurus aurocapilla ) and Wood Thrushes (  Hylocichla mustelina ). Few species were unique to one type of habitat, but overall avian community structure in oak savannas and closed-canopy forests was generally distinctive. Estimates of nesting success (derived from 785 nests) revealed that 6 of the 13 species considered experienced greater productivity in the savanna habitat. Rates of brood parasitism were unaffected by restoration and habitat structure. Within savannas, tract size had little effect on breeding abundances and reproductive success. My results illustrate that restoration techniques can significantly affect the ecology of constituent animal populations and communities and have key implications regarding avian conservation and the management of forest habitat in fragmented landscapes. Small patches of forest habitat that regularly function as population sinks may offer far better prospects for birds if they are subjected to disturbance and ecosystem restoration.     

Rodent Communities in an Exurbanizing Southwestern Landscape (U.S.A.)

Abstract:  Ranches are being converted to exurban housing developments in the southwestern United States, with potentially significant but little-studied impacts on biological diversity. We captured rodents on 48 traplines in grasslands, mesquite savannas, and oak savannas in southeastern Arizona that were grazed by livestock, embedded in exurban housing developments, grazed and embedded in development, or neither grazed nor embedded in development. Independent of habitat or development, rodent species richness, mean rank abundance, and capture rates of all rodents combined were negatively related to presence of livestock grazing or to its effects on vegetative ground cover. Exurban development had no obvious effects on rodent variety or abundance. Results suggest southwestern exurban developments can sustain a rich assemblage of grassland and savanna rodents if housing densities are low and houses are embedded in a matrix of natural vegetation with little grazing.     

Impacts of Alternative Timber Harvest Practices on Leaf-Chewing Herbivores of Oak

Abstract:  Studies of the effects of logging on Lepidoptera rarely address landscape-level effects or effects on larval, leaf-feeding stages. We examined the impacts of uneven-aged and even-aged logging on the abundance, richness, and community structure of leaf-chewing insects of white ( Quercus alba L.) and black ( Q. velutina L.) oak trees remaining in unharvested areas by sampling 3 years before and 7 years after harvest. After harvest, white oaks in uneven-aged sites had 32% fewer species of leaf-chewing insects than control sites. This reduction in species richness may have resulted from changes in microclimate (reducing plant quality and/or changing leaf phenology) that affected a much larger total area of each site than did even-aged cuts. For black oak after harvest, species richness in uneven- and even-aged sites increased relative to levels before harvest. Harvesting did not alter total insect density or community structure in the unlogged habitat for either oak species with one exception: insect density on black oak increased in the oldest forest block. Community structure of herbivores of black and white oaks in clearcut gaps differed from that of oaks in intact areas of even-aged sites. Furthermore, both richness and total insect density of black oaks were reduced in clearcut gaps. We suggest that low-level harvests alter herbivore species richness at the landscape level. Treatment effects were subtle because we sampled untreated areas of logged landscapes, only one harvest had occurred, and large temporal and spatial variation in abundance and richness existed. Although the effects of logging were greater in uneven-aged sites, the effects of even-aged management are likely to increase as harvesting continues.     

Woody encroachment decreases diversity across North American grasslands and savannas

Woody encroachment is a widespread and acute phenomenon affecting grasslands and savannas worldwide. We performed a meta-analysis of 29 studies from 13 different grassland/savanna communities in North America to determine the consequences of woody encroachment on plant species richness. In all 13 communities, species richness declined with woody plant encroachment (average decline = 45%). Species richness declined more in communities with higher precipitation (r2 = 0.81) and where encroachment was associated with a greater change in annual net primary productivity (ANPP; r2 = 0.69). Based on the strong positive correlation between precipitation and ANPP following encroachment (r2 = 0.87), we hypothesize that these relationships occur because water-limited woody plants experience a greater physiological and demographic release as precipitation increases. The observed relationship between species richness and ANPP provides support for the theoretical expectation that a trade-off occurs between richness and productivity in herbaceous communities. We conclude that woody plant encroachment leads to significant declines in species richness in North American grassland/savanna communities.     

Invertebrate Morphospecies as Surrogates for Species: A Case Study

Environmental monitoring and conservation evaluation in terrestrial habitats may be enhanced by the use of invertebrate inventories, but taxonomic and logistic constraints frequently encountered during conventional taxonomic treatment have greatly restricted their use. To overcome this problem we suggest that nonspecialists may be used to classify invertebrates to morphospecies without compromising scientific accuracy. To test this proposition, large pitfall and litter samples of ants, beetles, and spiders from four forest types were sorted to morphospecies by a nonspecialist and to species by specialists. These data were used to generate morphospecies and species inventories and to estimate richness (α diversity) and turnover (β diversity), information frequently used in the above activities. Our results show that the estimates of richness of ants and spiders varied little between morphospecies and species inventories. Differences between estimates of beetle richness were largely influenced by errors of identification in two families, Curculionidae and Staphylinidae. But morphospecies and species inventories yielded identical ranking of forest type using richness. Turnover was assessed by sample ordination, which revealed similar clusters regardless of the type of inventory. Analysis of similarities of assemblages of ants and beetles showed significant differences between all forest types. Spider assemblages showed a lower level of discrimination. The assessment of turnover was consistent among inventories but different between the major taxa. Our findings suggest that morphospecies may be used as surrogates for species in some environmental monitoring and conservation, in particular when decisions are guided by estimates of richness and the assessment of turnover.     

Countryside Biogeography of Moths in a Fragmented Landscape: Biodiversity in Native and Agricultural Habitats

Abstract: Studies of fragmented landscapes, especially in the tropics, have traditionally focused on the native fragments themselves, ignoring species distributions in surrounding agricultural or other human-dominated areas. We sampled moth species richness within a 227-ha forest fragment and in four surrounding agricultural habitats (coffee, shade coffee, pasture, and mixed farms) in southern Costa Rica. We found no significant difference in moth species richness or abundance among agricultural habitats, but agricultural sites within 1 km of the forest fragment had significantly higher richness and abundance than sites farther than 3.5 km from the fragment. In addition, species composition differed significantly between distance classes ( but not among agricultural habitats), with near sites more similar to forest than far sites. These results suggest that (1) different agricultural production regimes in this region may offer similar habitat elements and thus may not differ substantially in their capacities to support native moth populations and (2) that the majority of moths may utilize both native and agricultural habitats and move frequently between them, forming "halos" of relatively high species richness and abundance around forest fragments. Correlations between species richness and the amount of nearby forest cover, measured over circles of various radii around the sites, suggest that halos extend approximately 1.0–1.4 km from the forest edge. The extent of these halos likely differs among taxa and may influence their ability to survive in fragmented landscapes.     

Conservation of Insect Diversity: a Habitat Approach

Abstract: Neither time nor resources exist to design conservation plans for every species, particularly for little-studied, noncharismatic, but ecologically important taxa that make up most of biodiversity. To explore the feasibility of basing conservation action on community-level biogeography, we sampled a montane insect community. We addressed three issues: (1) the appropriate scale for sampling insect communities; (2) the association of habitat specialization—perhaps a measure of extinction vulnerability—with other ecological or physical traits; and (3) the correlation of diversity across major insect groups. Using malaise traps in Gunnison County, Colorado, we captured 8847 Diptera (identified to family and morphospecies), 1822 Hymenoptera (identified to morphospecies), and 2107 other insects (identified to order). We sampled in three habitat types—meadow, aspen, and conifer—defined on the basis of the dominant vegetation at the scale of hundreds of meters. Dipteran communities were clearly differentiated by habitat type rather than geographic proximity. This result also holds true for hymenopteran communities. Body size and feeding habits were associated with habitat specialization at the family level. In particular, habitat generalists at the family level—taxa perhaps more likely to survive anthropogenic habitat alteration—tended to be trophic generalists. Dipteran species richness was marginally correlated with hymenopteran species richness and was significantly correlated with the total number of insect orders sampled by site. Because these correlations result from differences in richness among habitat types, insect taxa may be reasonable surrogates for one another when sampling is done across habitat types. In sum, community-wide studies appear to offer a practical way to gather information about the diversity and distribution of little-known taxa.     

Defining Historical Baselines for Conservation: Ecological Changes Since European Settlement on Vancouver Island,Canada

Abstract: Conservation and restoration goals are often defined by historical baseline conditions that occurred prior to a particular period of human disturbance, such as European settlement in North America. Nevertheless, if ecosystems were heavily influenced by native peoples prior to European settlement, conservation efforts may require active management rather than simple removal of or reductions in recent forms of disturbance. We used pre‐European settlement land survey records (1859–1874) and contemporary vegetation surveys to assess changes over the past 150 years in tree species and habitat composition, forest density, and tree size structure on southern Vancouver Island and Saltspring Island, British Columbia, Canada. Several lines of evidence support the hypothesis that frequent historical burning by native peoples, and subsequent fire suppression, have played dominant roles in shaping this landscape. First, the relative frequency of fire‐sensitive species (e.g., cedar [Thuja plicata]) has increased, whereas fire‐tolerant species (e.g., Douglas‐fir [Pseudotsuga menziesii]) have decreased. Tree density has increased 2‐fold, and the proportion of the landscape in forest has greatly increased at the expense of open habitats (plains, savannas), which today contain most of the region's threatened species. Finally, the frequency distribution of tree size has shifted from unimodal to monotonically decreasing, which suggests removal of an important barrier to tree recruitment. In addition, although most of the open habitats are associated with Garry oak (Quercus garryana) at present, most of the open habitats prior to European settlement were associated with Douglas‐fir, which suggests that the current focus on Garry oak as a flagship for the many rare species in savannas may be misguided. Overall, our results indicate that the maintenance and restoration of open habitats will require active management and that historical records can provide critical guidance to such efforts.     

Using Gall Wasps on Oaks to Test Broad Ecological Concepts

Abstract:  Planning conservation of insect herbivores requires knowing what needs to be conserved and developing a set of predictor variables that aid management. We conducted a state-wide survey to examine the species richness of gall wasps (Hymenoptera: Cynipidae) on six oak species dominant in the threatened scrub-oak vegetation in peninsular Florida. Eighty-eight cynipid species were recorded; 23 were new species to Florida (a 35% increase), including 17 species new to science and 6 species newly recorded in the state. The cynipid species represented 68% of cynipids of Florida, on only 24% of oak species sampled. This fauna represents a hotspot of richness, justifying conservation initiatives in scrub-oak habitat and throughout the state. We derived predictor variables from general ecological concepts: (1) the theory of island biogeography that insect species richness increases as host plant geographic area increases and as local abundance increases, (2) the plant-architecture hypothesis that insect species richness increases with increased plant size, and (3) phytochemical patterns in leaves, including nutrients and digestibility reducers predicting suitability for insect herbivores. Concepts 1 and 2, developed for large scales and species numbers, were tested at smaller scales relevant to much conservation research and management. A stepwise multiple regression including all predictor variables accounted for 99% of the variance in cynipid species richness with three variables: foliar hemicellulose concentration (81%), host geographic area (16%), and tree height (2%). The trends were negative, however, and opposite to those predicted by concepts 1 and 2. Ecological theory was not applicable to discovery of predictors of cynipid species richness on six oak species. Thus, we promote caution in applying ecological theory to a narrow set of species without specific testing of how patterns conform to theoretical predictions.     

Effect of Human Disturbance on Bee Communities in a Forested Ecosystem

Abstract:  It is important for conservation biologists to understand how well species persist in human-dominated ecosystems because protected areas constitute a small fraction of the Earth's surface and because anthropogenic habitats may offer more opportunities for conservation than has been previously thought. We investigated how an important functional group, pollinators (bees; Hymenoptera: Apiformes), are affected by human land use at the landscape and local scales in southern New Jersey (U.S.A.). We established 40 sites that differed in surrounding landscape cover or local habitat type and collected 2551 bees of 130 species. The natural habitat in this ecosystem is a forested, ericaceous heath. Bee abundance and species richness within forest habitat decreased, not increased, with increasing forest cover in the surrounding landscape. Similarly, bee abundance was greater in agricultural fields and suburban and urban developments than in extensive forests, and the same trend was found for species richness. Particular species groups that might be expected to show greater sensitivity to habitat loss, such as floral specialists and bees of small or large body size, did not show strong positive associations with forest habitat. Nevertheless, 18 of the 130 bee species studied were positively associated with extensive forest. One of these species is a narrow endemic that was last seen in 1939. Our results suggest that at least in this system, moderate anthropogenic land use may be compatible with the conservation of many, but not all, bee species.     

Shifts in southern Wisconsin forest canopy and understory richness, composition, and heterogeneity

We resurveyed the under- and overstory species composition of 94 upland forest stands in southern Wisconsin in 2002-2004 to assess shifts in canopy and understory richness, composition, and heterogeneity relative to the original surveys in 1949-1950. The canopy has shifted from mostly oaks (Quercus spp.) toward more mesic and shade-tolerant trees (primarily Acer spp.). Oak-dominated early-successional stands and those on coarse, nutrient-poor soils changed the most in canopy composition. Understories at most sites (80%) lost native species, with mean species density declining 25% at the 1-m2 scale and 23.1% at the 20-m2 scale. Woody species have increased 15% relative to herbaceous species in the understory despite declining in absolute abundance. Initial canopy composition, particularly the abundance of red oaks (Quercus rubra and Q. velutina), predicted understory changes better than the changes observed in the overstory. Overall rates of native species loss were greater in later-successional stands, a pattern driven by differential immigration rather than differential extirpation. However, understory species initially found in early-successional habitats declined the most, particularly remnant savanna taxa with narrow or thick leaves. These losses have yet to be offset by compensating increases in native shade-adapted species. Exotic species have proliferated in prevalence (from 13 to 76 stands) and relative abundance (from 1.2% to 8.4%), but these increases appear unrelated to the declines in native species richness and heterogeneity observed. Although canopy succession has clearly influenced shifts in understory composition and diversity, the magnitude of native species declines and failure to recruit more shade-adapted species suggest that other factors now act to limit the richness, heterogeneity, and composition of these communities.     

Effectiveness of Vegetation Surrogates for Parasitoid Wasps in Reserve Selection

Abstract:  Selecting suitable nature reserves is a continuing challenge in conservation, particularly for target groups that are time-consuming to survey, species rich, and extinction prone. One such group is the parasitoid Hymenoptera, which have been excluded from conservation planning. If basic characteristics of habitats or vegetation could be used as reliable surrogates of specific target taxa, this would greatly facilitate appropriate reserve selection. We identified a range of potential habitat indicators of the species richness of pimpline parasitoid communities (Hymenoptera: Ichneumonidae: Pimplinae, Diacritinae, Poemeniinae) and tested their efficiency at capturing the observed diversity in a group of small woodlands in the agricultural landscape of the Vale of York (United Kingdom). Eight of the 18 vegetation-based reserve-selection strategies were significantly better at parasitoid species inclusion than random selection of areas. The best strategy maximized richness of tree species over the entire reserve network through complementarity. This strategy omitted only 2–3 species more (out of 38 captured in the landscape as a whole) than selections derived from the parasitoid survey data. In general, strategies worked equally well at capturing species richness and rarity. Our results suggest that vegetation data as a surrogate for species richness could prove an informative tool in parasitoid conservation, but further work is needed to test how broadly applicable these indicators may be.     

Quantifying the Indicator Power of an Indicator Species

Abstract:  Biodiversity indicator species are needed for classifying biotopes and sites for conservation, and a number of methods have been developed for determining indicator species for this purpose. Nevertheless, in addition to site classification, there is sometimes a need to define an indicator species that indicates the occurrence of another species. For example, when a species of interest (target species) is difficult to detect or identify, a reliable indicator species can function as a tool that saves time and money. We derived a method that provides a quantitative measure of the indicator power (IP) of an indicator species for the target species or any species assemblage. We calculated the measure of IP from a presence–absence matrix that covered several sites. The method provided a list of indicator species, the presence of which reliably indicated the presence of another species (e.g., a threatened or rare species in a given area). The IP of the species was highest when the number of shared occurrences between the indicator species and the target species was high and, simultaneously, when the indicator species and the target species occurred separately in only a few cases. The IP was also positively influenced by the number of sites with no occurrences of either the indicator or the target species. Our method can also be used to quantify different types of species occurrence indications. We refer to these types as presence–presence, presence–absence, absence–presence, and absence–absence indications. To clarify the use of the method, we examined the situation with red-listed polypores in White-backed Woodpecker (Dendrocopos leucotos) habitats in Fennoscandia and found some suitable indicator species. Our method provides a new, objective way to evaluate the IP of an indicator species.     

Bat Diversity and Abundance as Indicators of Disturbance in Neotropical Rainforests

Abstract: Evaluating the degree of disturbance of any region to determine its relative importance for conservation purposes requires procedures that are relatively inexpensive and that yield accurate results fast. Because bats are abundant, diverse, and easy to sample, especially in the Neotropical rainforest, they fulfill several of the requirements of indicator species as identified in the literature. For 10 months we sampled bat communities in the Selva Lacandona in Chiapas, Mexico, at 15 sites representing five habitats. We also measured 10 variables representing vegetation structure and diversity at each site. With fuzzy-set techniques we produced a gradient classification of disturbance for the 15 sites based on the vegetation data. We explored the relationship between vegetation conditions, described as the membership degrees in the construct "fuzzy forest set" (the complementary fuzzy set of "disturbance"), and four bat community variables. Bat species richness, number of rare bat species, and the bat diversity index were positively correlated with the vegetation scores, and relative abundance of the most abundant bat species was negatively correlated with vegetation scores. A high number of phyllostomine species in a community is a good indicator of low levels of disturbance. Although a single indicator group will probably not be sufficient for decision-making processes in conservation, evaluating bat populations may be a good first step in assessing an area's conservation value, especially in rainforest regions.     

Rove beetles (Coleoptera: Staphylinidae) collected during the long term ecological research in a Hungarian oak forest

Along term ecological research was carried out in a Hungarian oak forest, in "Bükk" National Park starting with 1972. During the faunistical studies 3,602 insect species and more than 200,000 individuals were collected. The dominant orders were Coleoptera (1,051 species), Lepidoptera (803 species), Hymenoptera (470 species) and Diptera (400 species). The relative species abundance (RSA) for all insects collected in all years of sampling period suggests a rather J shape curve than a not clear scaling property. This means that we were able to identify almost three quarters of the insect species from one ha European oak forest during the survey (from 1987 to 2003), and two third of the staphylinides expected. Considering the staphylinid fauna a total number of 160 species and 4,022 individuals were collected. The most widely occurring species in dominance order were: Ocypus biharicus, Pseudocypus mus, Atheta gagatina, Philonthus quisquiliarius, Oxypoda acuminate, Platydracus chalcocephalus, Atheta crassicomis, Latrimaeum atrocephalum, Haploglossa puncticollis, Philonthus succicola and Anotylus mutator. The pooled value of alpha diversity was 1.51. The Shannon-Weiner Index (H') was relatively high (3.29) in comparison with other studies.     

Single Species as Indicators of Species Richness and Composition in California Coastal Sage Scrub Birds and Small Mammals

Abstract: Individual species may be useful as indicators of biodiversity if an association exists between the presence of a species and another component of biodiversity. We evaluated 40 species of birds and small mammals, including 11 species of conservation concern, as potential indicators of species richness and species composition in southern California coastal sage scrub habitats. This habitat, which is the target of large-scale conservation planning, has been greatly reduced by human development and supports many plants and animals of conservation concern. We asked whether there is an association between the presence of a potential indicator species and the species richness and composition of the bird or small-mammal community in which it is found. We used point counts and live-trapping to quantify the distribution of birds and small mammals, respectively, at 155 points in 16 sites located in three counties. Of the few species we found associated with species richness, some were associated with higher species richness and others with lower richness, and species of conservation concern were not more frequently associated with species richness than were common species. Ordination analysis revealed a geographic gradient in coastal sage scrub bird and small-mammal species composition across southern California, and 18 of the species we evaluated were associated with the composition of the bird and small-mammal community in which they were found. Our results suggest that efforts to conserve bird and small-mammal biodiversity in coastal sage scrub should not focus exclusively on rare species or on locations with the highest species richness, but instead should focus on a diverse suite of species that are representative of the range of variation in communities found in coastal sage scrub habitats.     

N biogeochemistry and cycling in two well-drained savannas: a comparison between the Orinoco Basin (Llanos,Venezuela) and Ivory Coast (western Africa)

When a savanna burns, a decline in the input of organic matter and nutrients to the soil occurs. However, the existence of recurrent fires is a natural condition and N depletion by fire is not incompatible with the existence of savannas per se. Consequently, savanna vegetations have evolved under fires, implying a near to steady-state N budget. In some Australian and African ecosystems, N fixation appears to be insufficient to replace losses inducing soil-N depletion, whereas in neotropical Llanos and western African savannas, the N-fixation and precipitation seem to be enough to maintain production despite fires. This review presents information about well-drained savannas, namely Trachypogon savannas in Orinoco Llanos and Andropogonae savannas in Ivory Coast. The sites present similarities in climate and fire regime differing in soil parent material. A report on N budgets is presented. The budget was positive, since losses seem to be balanced by inputs in rainfall and biological fixation. Uncertainties in flux measures indicate that more work on those aspects are required. Results indicate that the estimated amounts of dinitrogen fixation and deposition seem to be enough to maintain plant production. Data support the hypothesis that the vegetation in the natural savanna has evolved under fire constraint.     

A Multiscale Landscape Approach to Predicting Bird and Moth Rarity Hotspots in a Threatened Pitch Pine–Scrub Oak Community

Abstract:  In the northeastern United States, pitch pine (  Pinus rigida Mill.)–scrub oak ( Quercus ilicifolia Wang.) communities are increasingly threatened by development and fire suppression, and prioritization of these habitats for conservation is of critical importance. As a basis for local conservation planning in a pitch pine–scrub oak community in southeastern Massachusetts, we developed logistic-regression models based on multiscale landscape and patch variables to predict hotspots of rare and declining bird and moth species. We compared predicted moth distributions with observed species-occurrence records to validate the models. We then quantified the amount of overlap between hotspots to assess the utility of rare birds and moths as indicator taxa. Species representation in hotspots and the current level of hotspot protection were also assessed. Predictive models included variables at all measured scales and resulted in average correct classification rates (optimal cut point) of 85.6% and 89.2% for bird and moth models, respectively. The majority of moth occurrence records were within 100 m of predicted habitat. Only 13% of all bird hotspots and 10% of all moth hotspots overlapped, and only a few small patches in and around Myles Standish State Forest were predicted to be hotspots for both taxa. There was no correlation between the bird and moth species-richness maps across all levels of richness ( r =−0.03, p = 0.62). Species representation in hotspots was high, but most hotspots had limited or no protection. Given the lack of correspondence between bird and moth hotspots, our results suggest that use of species-richness indicators for conservation planning may be ineffective at local scales. Based on these results, we suggest that local-level conservation planning in pitch pine–scrub oak communities be based on multitaxa, multiscale approaches.