Litter Arthropods Research Articles

Effects of isolation on the colonisation of restored habitat patches by forest‐dependent arthropods of soil and litter

Abstract. A novel experimental approach was taken to investigate the effects of distance from rainforest remnants on the recolonisation patterns of ants and other soil and litter arthropods in ‘restored’ habitat patches within a pasture matrix. Experimental habitat patches were created by adding a thick mulch of sterilised woodchips and leaves, and simulating shade using shadecloth, to create conditions similar to those that occur during rainforest restoration. These patches were deployed at five experimental sites in the Maleny plateau of subtropical eastern Australia. Artificial habitat patches were located at varying distances from a rainforest edge at each site, as well as within the rainforest. The experiment also included a test for efficacy of inoculation, which involved translocation of a small quantity of litter (containing live arthropods) from rainforest habitat to isolated habitat patches. The results showed that, after 9 months, there was little colonisation by rainforest‐dependent taxa in any of the experimental plots beyond those closely adjacent to forest patches. Inoculation was unsuccessful in increasing the extent of arthropod establishment. A number of explanations that potentially account for the observed results are suggested. An experimental approach provides an opportunity to test explicitly for factors considered important for the development of biota in restored habitat patches. There are, however, unavoidable limitations associated with the design of experiments that simulate small‐scale analogues of restoration treatments. Avoiding these limitations may require controlled and replicated efforts in experimental restoration over larger areas, based on collaborations between researchers and practitioners.

Invertebrates and the Restoration of a Forest Ecosystem: 30 Years of Research following Bauxite Mining in Western Australia

Abstract Restoration needs to consider more than just soils and plants. The role of terrestrial invertebrates in the restoration of Alcoa’s bauxite mines in the Jarrah (Eucalyptus marginata) forest of Western Australia has been the subject of over 20 individual studies. Projects range from arthropods in soil and leaf litter, to the understorey vegetation, and the tree canopy. Moreover, projects span a range of trophic groups, including decomposers (e.g., springtails and termites), predators (e.g., ants and spiders), and herbivores (e.g., true bugs and ants preying on seeds). Elucidation of recolonization trajectories uses both space‐for‐time substitutions and long‐term regular sampling. Importantly, many studies are at species level rather than coarser taxonomic ranks. This paper provides an historical account and an integrated review of this research. The role of ants as seed predators and as indicators of ecosystem health is described. Successional data for other groups, when measured by species richness (ants, spiders, and hemipterans) and composition (ants and spiders), show their reassembly trajectories tracking toward unmined reference areas. Hemipteran species composition tracks the vegetation reassembly trajectory but not toward unmined reference areas. Studies also have revealed optimal sampling methods for surveying invertebrates and their rich biodiversity in southwestern Australia. In restored mine pits burnt to reduce fuel loads, the response of spiders to this additional disturbance was retrogression/alteration of the post‐mining trajectory. Finally, attention is drawn to research areas receiving limited scrutiny to date, such as the contribution of terrestrial invertebrates to ecosystem function and taxonomic groups not yet studied.

Spatial and temporal distribution of litter arthropods in different vegetation covers of Porto Santo Island (Madeira Archipelago, Portugal)

The main objective of this study is to assess the soil diversity and temporal and spatial distribution of litter macro-arthropods, captured with pitfall traps, on different vegetation covers from Porto Santo Island (Portugal) with different soil physical and chemical characteristics. The PCA clearly separated sampling areas geographically more exposed to winds and solar radiation, from the others that were not. In this analysis, seasons seemed to have no influence on this distribution. Non-exposed areas were characterized by high soil temperatures, water and organic matter contents. Among these areas, those that were covered by Pinus halepensis and Eucalyptus ficifolia showed the highest C/N ratios in winter, which may be explained by likely inhibitory effects of phenolic compounds of the leaves of both species on the decomposition process. The highest number of organisms was recorded on the exposed areas. Variance partitioning using CCA showed that the different vegetation covers and environmental variables explained 19% and 30%, respectively, of the variance in macro-arthropods distribution. Four environmental variables (exposure, temperature, C/N ratio and exchangeable K) were positively correlated with the taxa abundance matrix. The results showed that non-exposed areas with E. ficifolia and Cupressus macrocarpa seemed to favour the establishment of a high diversity of taxa, especially in the summer, when soil conditions tend to be extreme.

Fertilization responses of soil litter fauna and litter quantity, quality, and turnover in low and high elevation forests of Puerto Rico

This study evaluates the effects of chemical fertilization on litter production, litter arthropods, and earthworms in tropical wet and cloud forests in the Luquillo Mountains in northeastern Puerto Rico. Litter production, chemistry and turnover, forest floor mass, litter arthropod density (individuals g −1 dry litter), abundance (individuals m −2) and diversity, and earthworm abundance and fresh mass (g m −2) were measured in 20 m × 20 m control and fertilized plots. We hypothesized that fertilization would increase litter arthropod density, abundance and diversity in both forests through elevating litter production and improving litter quality, and the increased litter quality in fertilized plots was also expected to result in faster litter turnover rates. Fertilization significantly increased monthly litterfall production and litter quality as measured by leaf litter C/N and C/P ratios in both forests, and higher litter production led to significant litter accumulation on the forest floor. Litter arthropod abundance increased in the wet forest fertilized plots due to the accumulated litter. Higher litter quality did not affect litter arthropod density in either forest, and densities were slightly higher in the cloud forest. High litter quality increased litter turnover rate in the cloud forest only. A significant reduction in earthworm populations in fertilized plots may have offset the positive effect of litter quality on litter turnover in the wet forest. Shannon biodiversity index for litter arthropod taxa was similar between treatments in the wet forest, and was higher in the wet forest than cloud forest. We conclude that climate influences litter arthropod diversity, but differences in litter quantity and quality do not affect their densities in island tropical wet and cloud forests.

The use of ants and other soil and litter arthropods as bio-indicators of the impacts of rainforest clearing and subsequent land use

The present study investigated the impacts of rainforest clearance, and associated subsequent land␣use for pasture, on assemblages of soil and litter arthropods in eastern subtropical Australia. We assessed the utility of soil and litter arthropods as potential bio-indicators of cleared and forested habitats. Arthropods were sampled from 24 sites (12 sites each in rainforest and pasture) using two methods (extraction from litter, pitfall traps). Responses of taxa were analysed at various levels of taxonomic resolution, including ‘coarse’ arthropods (all arthropods sorted to Order/Class), ant genera and ant species. Multivariate analyses of arthropod composition indicated that an increase in the level of taxonomic resolution did not provide a commensurate increase in the sensitivity of assemblage response. Indicator values (IndVals), computed for each taxon, showed that a number of arthropod taxa may have potential as bio-indicators of habitat change. However the use of many of these, especially many ant species found in our study, may be unreliable because even after extensive numbers of sites were sampled, most species showed patchy distributions. To overcome this problem, we generated ‘composite indices’, by combining information from sets of indicator taxa. The utility of these composite indices is discussed.

Ontogenetic Diet Change in the Arthroleptid Frog Schoutedenella xenodactyloides

Anuran amphibians are important consumers of arthropods in tropical ecosystems. Previous research has indicated that very small, terrestrial frogs, especially juveniles, largely consume small leaf litter arthropods. To date, few studies have examined diet in African anurans, and no studies exist of ontogenetic change in prey composition for any African frog. We investigated the change in diet that accompanies body size increase in the arthroleptid frog Schoutedenella xenodactyloides (Anura: Ranoidea) from a population located on the Mulanje Massif in Malawi, central Africa. Schoutedenella xenodactyloides is a miniature (< 22 mm snout–urostyle length; SUL), direct-developing frog that is often very abundant and is likely an important consumer of small leaf litter arthropods. Based on examination of stomach and intestinal contents from specimens that span the known range of posthatching body sizes, we document the taxonomic diversity of prey consumed by S. xenodactyloides. We present evidence that S. xenodactyloides exhibits a size-related ontogenetic change in the type and relative proportions of prey taxa. Small frogs (≤ 13 mm SUL) consume large numbers of collembolans and mites. As frogs attain larger body sizes; ants constitute a larger percentage of the total number of prey consumed; and collembolan and mite consumption falls below 10% of the total prey items. The prey consumed by S. xenodactyloides include at least 10 orders of arthropods and an unidentified mollusk. This is a greater diversity of prey items than previously found in Schoutedenella as well as most other arthroleptid species.

Arthropod response to prescription burning at the soil–litter interface in oak–pine forests

In the southeastern U.S., forest managers are returning repetitive fire to the landscape to facilitate regeneration of desirable species. The increased use of prescribed fire generates questions regarding the effects of single- and multiple-burning events on leaf-litter and ground-dwelling arthropods, and recovery of these arthropods following fire disturbance. In this study, the effects of early season single- and multiple-burns were assessed on leaf-litter arthropods and ground-dwelling arthropods in oak–pine forests for two growing seasons following fire disturbance. Arthropods were sampled by leaf-litter extraction and pitfall trapping, where pitfall trapping was restricted to single-burned areas. For each sampling method, arthropod abundance, diversity, richness, and evenness were calculated at the family or ordinal level. Forest characteristics were also surveyed to measure impacts from the prescribed fires and to assess variability in the forest environment. Leaf-litter arthropod abundance was devastated by burning, and resurgence of populations was not evident until the second growing season in the multiple-burned areas. In single-burned plots, litter arthropod abundance remained low for the duration of the study possibly due to greater fire intensity relative to the multiple-burn plots. Leaf-litter arthropod diversity was not affected by either burn regime. Burning decreased leaf-litter arthropod richness and increased leaf-litter arthropod evenness, but these effects were only marginally significant. Prescription burning had no impact on ground-dwelling arthropod abundance, diversity, or richness, but arthropod community evenness increased following the single-burn disturbance. In the principal components analysis (PCA), burning was a major gradient explaining 46% of the variation in the data. Burning decreased leaf-litter cover and depth and lower canopy cover, and contributed to the variance explained by PCA. Our data confirm that prescription burning is accomplishing its management goal of removing undesirable lower-canopy cover in the mixed hardwood forests of the Cumberland Plateau. Following early-season, low-intensity burns, recovery of leaf-litter arthropods was not evident until two-growing seasons after fire disturbance. Any differences we observed could be attributed to lower fire intensity in forests that are repeatedly burned. Prescribed burns should be utilized on a rotation greater than 2 years to allow resurgence of the leaf-litter arthropod community and recovery of the leaf-litter habitat.

Fire and fire surrogate treatment effects on leaf litter arthropods in a western Sierra Nevada mixed-conifer forest

Frequent, low-intensity fires were a common feature of Sierran forest ecosystems, but suppression policies over the past century have left many forests at risk for catastrophic wildfires. Recent policies highlight the use of prescribed burning or harvesting as fire risk reduction tools, but few studies have investigated the impacts of these management practices on the leaf litter fauna of Sierran forests. This study examines how three fire and “fire surrogate” treatments, prescribed burning, overstory thinning with understory mastication, and combined thinning and burning, impact diversity and abundance of Coleoptera and other leaf litter arthropods. Pitfall trapping was used to collect litter arthropods before and immediately after treatments in replicated forest compartments. The diverse Coleoptera assemblage was dominated by only a few common species, with many rare species represented by only one or two individuals. Rank–abundance diagrams indicated that much of the change in the beetle assemblage due to the treatments was a result of changes in the numbers of rare species. Indicator species analysis showed several species closely allied with the treated compartments, but few with the untreated controls. Both NMS and CCA ordination show considerable change in overall assemblage structure on compartments treated with fire, but less change in the thinned compartments. Coleoptera species richness was slightly higher in burned compartments. Some common beetle species, families of beetles, and other common groups such as ants and spiders showed changes in abundance due to the treatments, but the changes were taxon-specific and showed no general pattern. Overall impacts of the treatments appear to be moderate, and the increased habitat heterogeneity at the compartment level may provide additional habitat for many rare species to coexist. We conclude that the use of fire and fire surrogate treatments in Sierran mixed-conifer forests is justified from the standpoint of their effects on leaf litter arthropods, but the history of management at the site and the scale of treatments must be carefully considered.

Changes in soil and litter arthropod abundance following tree harvesting and site preparation in a loblolly pine ( Pinus taeda L.) plantation

Soil and litter arthropods are important in many forest ecosystem processes where they help to regulate nutrient dynamics and soil quality, and are useful bioindicators of ecosystem condition and change. This study was initiated in response to concerns about possible decline in site productivity due to intensive forestry practices. We investigated the effects of tree harvesting and site preparation treatments on soil and litter arthropod abundance in a loblolly pine plantation in eastern Texas, USA. Using soil and litter cores, we sampled abundance of selected arthropods over two years following tree harvesting. Response to treatments varied somewhat among arthropod taxa. Acari (mites) and Collembola (springtails), the numerically dominant taxa in core samples, were initially higher in abundance in less intensive harvesting and site preparation treatments. However, after 2 years, abundance of these arthropods was comparable in all harvesting and site preparation treatments. Fertilization with nitrogen and phosphorus had a strong positive effect on abundance of most arthropod groups in the second year of the study. The recovery of arthropod abundance through time suggests that the silvicultural practices used did not jeopardize the ecological integrity of the site. The results reported here contrast with other similar studies which suggests that soil and litter arthropod communities respond differently in different geographic locations and forest types. Further comparative and extensive studies of this nature are needed therefore for a deeper understanding of the impacts of forest management practices.

Effects of surface fires on understorey insectivorous birds and terrestrial arthropods in central Brazilian Amazonia

AbstractUnderstorey insectivorous birds are highly vulnerable to different forms of habitat disturbance in tropical forests. Here we examine the effects of an unprecedented surface fire on understorey insectivores and forest litter arthropods in a terra firme forest of central Brazilian Amazonia, and compare species and guild abundance both close to and far from the clearly distinguishable fireline separating burnt and unburnt forest. All six of the most abundant insectivorous foraging guilds examined were detrimentally affected by fire, with dead‐leaf gleaners and professional ant‐followers being the most heavily affected. While army ants were apparently absent from the burnt forest, results from pit‐fall traps showed that wildfires had only a limited effect on the abundance of most leaf‐litter invertebrates. The fireline appeared to be an abrupt barrier to many understorey insectivorous birds, and there was little evidence to suggest that primary forest species were recolonizing burnt forest up to 1 year after the fires. Factors affecting the capture frequency of insectivorous birds are discussed.

Using soil and litter arthropods to assess the state of rainforest restoration

Summary The present study investigated recolonization patterns of selected soil and litter arthropods following replanting of pasture with rainforest species in the Mary River catchment of eastern subtropical Australia. While extensive research has been conducted in rehabilitated mined sites in Australian dry sclerophyll forests, very little attention has been paid to rainforest restoration on previously pastoral land. We examined the utility of soil and litter arthropod groups for monitoring the progress of restoration, and the relationship between arthropod assemblage patterns and environmental factors potentially under the control of those doing the replanting. Leaf litter was extracted from 20 sites: five remnant rainforest, five pasture, and 10 sites that had been revegetated (from 1 to 12 years previously) with a diversity of indigenous species. Ants (identified to genus), centipedes, millipedes, isopods, amphipods and mites were enumerated and their assemblages described with multi‐ and univariate methods. Ant genera alone proved unable to distinguish pasture from rainforest, and mites (identified only to oribatid or non‐oribatid) proved of limited use because these two groups were present in all samples in extremely high numbers that overwhelmed the contributions of other arthropod groups. However, a coarse taxonomic approach using five arthropod groups (ants, centipedes, millipedes, isopods, amphipods) clearly discriminated between pasture and rainforest, and also arranged the revegetated sites between these two extremes. Simple frequency scores based on the presence/absence of these arthropod groups in each of three replicate subplots were sufficient to achieve this separation of site types. Habitats created by close planting of trees and mulching may accelerate invertebrate colonization and, thus, promote the rapid establishment of processes and functions characteristic of developing rainforests.

Diversity and conservation of forest-floor arthropods on a small Seychelles island

Cousine Island, Seychelles, is of major conservation significance as it is in a biodiversity hotspot. Furthermore, it is relatively pristine, and is apparently the only tropical island over 20 ha with no alien invasive mammals. This study focuses on the island's log and litter arthropods, which were sampled by extraction methods from the dominant species, Pisonia grandis, Ficus spp. and Cocos nucifera. Stage of decomposition, and forest type in which the logs occurred, both significantly influenced the composition and structure of the arthropod assemblages. Young logs were significantly richer in species than older logs, possibly because they had the most resources and microhabitats. There were some significant changes in arthropod species richness, composition and abundance between species of young logs, but not old ones, because as logs decomposed, arthropod assemblages converged. Nevertheless, each old log species had some arthropod species not present in other log species, which has important implications for conservation. Arthropod assemblages in woody litter varied according to the forest type in which they occurred, and were different from those in logs in the same forest type. Cousine Island arthropod species richness, both in logs and litter, was comparable to figures from other tropical areas. As the logs, especially P. grandis, are home to many Seychelles endemic species, their conservation is essential. Furthermore, as the arthropods are also the main food of certain threatened Seychelles vertebrates, their conservation also underpins a food chain on this unique tropical island.

Logging and burning impacts on cockroaches, crickets and grasshoppers, and spiders in Jarrah forest, Western Australia

In 1985 new silvicultural prescriptions for managing Jarrah ( Eucalyptus marginata) forest in southwest Western Australia came into operation. The most extreme logging treatment involved removal of most of the overstorey from 10 ha patches, followed by a regeneration fire. This study, part of a broader integrated research program, examined the impact of these disturbances on more than 400 species of leaf litter arthropods captured in pitfall traps one year before logging, 1 year before burning, and 4 years after burning. Most species of cockroaches (Blattodea), crickets and grasshoppers (Orthoptera), and spiders (Araneae) were resilient to logging and burning, and immediate decreases in species richness or total abundance were rapidly reversed. Changes in community structure caused by the imposed disturbances were also minimal or short term. Community structure in both the treatment and control sites at the end of the study was different from that at the beginning of the study, perhaps indicative of the overriding importance of climatic variation. The results of this study have broader relevance to understanding the long-term resilience of forest ecosystems in southwest Western Australia. Because of the role of the taxa studied in mediating decomposition, herbivory and predation, these ecosystem processes appear to be robust to the logging and burning prescriptions applied.

Spiders and Other Arthropods as Indicators in Old‐Growth Versus Logged Redwood Stands

AbstractThis study, conducted in the Santa Cruz Mountains of California, provides data on the abundance and diversity of litter spiders and other arthropods in three redwood forest conditions: old growth, second growth, and tree farm. Litter spiders are linked to and reflect habitat structure and prey abundance and can act as indicators for redwood forest restoration and monitoring. There were significant declines in spider and other arthropod diversity and abundance with increased logging and decreased herb cover. The absolute and relative increase in nocturnal spiders and detritivores in unlogged sites suggests that guild structures of spiders and other arthropods can indicate forest recovery from logging disturbance. Furthermore, selectively harvested stands do not retain old‐growth levels of litter arthropod diversity or abundance. This study identifies potential indicator redwood litter spiders that show higher abundances in old‐growth areas, Zelotes sp. (Gnaphosidae), Xysticus sp. (Thomisidae), and Ceratinops inflata (Linyphiidae) and a possible old‐growth specialist, Phrurotimpus sp. (Liocranidae). These findings strengthen the case for including soil arthropods in redwood forest monitoring and assessment and for the preservation of undisturbed forest areas.

Comparison of the Reproductive Biology of Two Neotropical Wrens in an Unpredictable Environment in Northeastern Colombia

Abstract Buff-breasted (Thryothorus leucotis) and Rufous-and-white (T. rufalbus) wrens living in a dry forest in northeast Colombia (Parque Nacional Natural Tayrona) are faced with a large year-to-year uncertainty in the arrival time of the rainy season, as well as the amount of rain falling in the first six months of the year. Those factors are thought to be important cues used by those species in their reproductive decisions. In this study, I gathered data on several reproductive parameters (clutch size, nesting success, timing of breeding, renesting attempts) for both species during two years of contrasting rainfall patterns. I collected information on the foraging behavior of both species to identify their main food and to study how rainfall affects the dynamics of those resources. Buff-breasted Wrens fed mostly in the understory, gleaning arthropods from upper and lower leaf surfaces, dry branches, and aerial litter. Numbers of arthropods in those microhabitats depend strongly on the amount of rainfall; understory arthropod levels are low during the dry season and increase with the arrival of the rains. Buff-breasted Wrens timed their reproduction with the arrival of the rains in both years, delaying the onset of breeding significantly and continuing to breed during the dry year (1994). Rufous-and-white Wrens spent a large proportion of their time feeding on arthropods in the leaf litter. Number of arthropods in the litter varied little between dry and wet periods. Therefore, Rufous-and-white Wrens had a more constant food environment despite large differences in rainfall within and between the years of the study. That species started breeding earlier in the dry season and extended its breeding longer than Buff-breasted Wrens. My observations suggest that the evolution of the reproductive strategies in those species was mostly through the change of behavioral parameters rather than physiological reproductive parameters such as changes in clutch size, egg size, or number of broods.

Impacts of silvicultural practices on soil and litter arthropod diversity in a Texas pine plantation

In this study we used the diversity of soil and litter arthropods as a metric for evaluating the ecological effects of silvicultural practices of various intensities in a loblolly pine ( Pinus taeda L.) forest ecosystem. The treatments included low and high intensity harvesting, soil bedding, chemical herbicide application, and nitrogen and phosphorus fertilization. Soil and litter cores were used to sample arthropods after harvesting. In the first year following removal of trees, species diversity was higher in hand-fell, bole-only harvested plots than in mechanical, whole-tree harvested plots and higher in non-bedded plots than in bedded plots. However, these differences did not persist into the second year following harvesting. The recovery of undergrowth vegetation in the second year and the development of a rudimentary litter layer may have increased diversity in the more intensively treated plots. Arthropod species richness increased following nitrogen and phosphorus fertilization, but Shannon diversity did not. This indicates that the arthropod community had responded to fertilization with a shift in community composition. The rapid recovery of arthropod diversity in the second year following tree removal suggests that the silvicultural treatments used at this site did not put long-term productivity at risk. Comparisons with other similar studies suggest that when aiming for sustainable forest management, the particular silvicultural practices that allow for ecosystem recovery may depend on local and regional conditions.

Surface and leaf‐litter arthropods in the coastal forests of Tanzania

Surface and leaf litter arthropod assemblages of the seasonal lowland coastal forests of eastern Tanzania were investigated from eleven sites over a 3‐year period (1991–93). Pit‐fall trap data show that four groups comprise more than 10% of the total sample: ants (Hymenoptera: Formicidae, 31%), grasshoppers and crickets (Orthoptera, 22%), beetles (Coleoptera: 17.39%) and spiders (Araneae: 13.48%). Arthropod abundance varies considerably with season, with greater total numbers of arthropods in all groups found in wetter periods. Arthropod abundance also varies considerably according to habitat, with greatest numbers found in forests with the most intact canopy cover, and in valley‐bottom forest as compared to ridge‐top forest; the valleys are normally both wetter and with a more complete and taller canopy. Tullgren Funnel data show that over 50% of the leaf litter fauna comprises tiny arthropods of the groups Collembola and Acarina. Abundance of arthropods in the leaf litter of these forests varies from a maximum of ≈ 16,000 m–2, to a minimum of 780 m–2. Abundance is highest in wetter periods, in the forest areas with the most intact canopy cover, and in valley‐bottom as opposed to ridge‐top habitats.

Effects of three short rotation prescribed fires in spring on surface-active arthropods in dry sclerophyll eucalypt forest of west-central Victoria

Summary The effects of three prescribed low intensity fires varying from means of 80 to 209 kWm−1 within six years on invertebrates in litter/upper soil were assessed. The 8.6 year study was based on 88 934 arthropod specimens, representing 35 ordinal or lower level taxa contained in 3520 pitfall trap samples from a site burnt three times in spring and an unburnt control site within a 30.7 ha area. The three fires had no discernible effect on total taxa, total non-insects, Araneae (spiders), Acarina (mites), Collembola (springtails), total insects and Formicidae (ants), although activity of the Coleoptera (beetles) decreased significantly after the second and third fires while that of the Diptera (flies) increased over the same period. However, as Coleoptera and Diptera activity on the unburnt control site decreased and increased respectively over the same period, it is uncertain whether the changes in activity were due to the fires or other non fire-related environmental factors. Futhermore, these changes in activity resulted from one or two of the spring fires only, and not all three, further questioning whether the fires were the contributing causal factors. Three prescribed low-intensity fires in spring appear therefore, not to impact adversely on the activity of major forest litter arthropod groups, although the situation of the Coleoptera and Diptera is less clear due to similar activity on the unburnt control site in both cases. This therefore suggests that any fuel reduction burning in spring be conducted at intervals of not less than three years in order to minimize any impact on litter arthropods. Where a period of drought has occurred, burning should be delayed until the drought period has ended.

The Effects of Size on the Diets of Six Sympatric Species of Postmetamorphic Litter Anurans in Central Amazonia

The Effects of Size on the Diets of Six Sympatric Species of Postmetamorphic Litter Anurans in Central Amazonia

Response of soil and leaf litter microarthropods to forest application of diflubenzuron

The objective of this study was to assess the effects of forest application of diflubenzuron (Dimilin®), a gypsy moth suppressant, on nontarget invertebrates in litter and soil on the forest floor. Four experimental watersheds (two treatment and two reference) in the Fernow Experimental Forest, West Virginia, were sampled for two years before and one year after application of diflubenzuron (70 g ha−1, AI). Soil and leaf litter arthropods were monitored before and after application using soil cores and litter bag colonization samplers. Frequency analysis, BACIP, and ANOVA were used to analyse the data for diflubenzuron treatment effects. During the 36 month study, soil core samples were dominated by mites (49%) and springtails (28%). A total of 19 taxonomic groups were suitable for statistical analysis. We detected no significant treatment effects based on total organism counts or counts by trophic categories (p < 0.05). There were no significant treatment effects for populations of major taxonomic groups, except for Araneae (spiders). Analysis of leaf litter bags also showed no significant differences in total numbers of invertebrates or in trophic categories between treated and reference watersheds during the 12 month post-treatment study. Density of one species of springtail (Sminthurus purpurescens) and springtails as a group were significantly lower in treated watersheds. High variation was associated with both soil core and leaf bag samples; because of this variation, a significance level of 0.05 should be considered very conservative. Long-term trends in soil biota were evident, demonstrating the need for well-established pre-treatment baseline data for pesticide impacts on soil organisms