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Litter Depth (litter + depth)
Selected AbstractsUse of Premontane Moist Forest and Shade Coffee Agroecosystems by Army Ants in Western PanamaCONSERVATION BIOLOGY, Issue 1 2000Dina L. Roberts Behavioral and distributional studies of these two species have been confined largely to humid lowland forest. We conducted intensive systematic area searches at elevations between 1200 and 1800 m in western Panama to assess the distribution of both species in intact premontane moist forest, shade coffee plantations, and sun coffee plantations. Both species were repeatedly observed in forest, shade coffee plantations close to forest, and shade coffee plantations distant from forest. Neither species was observed in sun coffee plantations. We believe that retention of certain forest-like characteristics in the traditional shade coffee farm contributes to the persistence of these forest organisms in modified landscapes. Large canopy trees not only provide shade that buffers temperature extremes but also supply the ground layer with regular inputs of leaf litter and coarse woody debris from fallen trunks. Both E. burchelli and L. praedator hunt in leaf litter, and E. burchelli uses coarse woody debris as nesting sites ( bivouacs). There were significantly fewer potential bivouacs available in sun coffee plantations than in forest and shade coffee habitats. Also, litter depth was less in sun coffee than in forest and shade coffee. Our results provide the first evidence that shade coffee plantations can provide additional habitat for E. burchelli and L. praedator, top predators of the leaf litter arthropod community. E. burchelli and L. praedator act as critical links between swarm-attendant bird species and leaf-litter arthropods, providing an easily exploited food resource that would otherwise be unavailable for many birds. Continued conversion of shade coffee plantations to sun coffee plantations could have negative effects on army ants and associated biodiversity. Resumen: Las hormigas arrierras Neotropicales, Eciton burchelli y Labidus praedator ( Hymenoptera: Formicidae: Ecitoninae) son especies que requieren de extensas áreas de hábitat para cazar. Los estudios conductuales y de la distribución de estas especies se han realizado principalmente en bosques húmedos en tierras bajas. Desarrollamos búsquedas sistemáticas intensivas en elevaciones entre 1200 y 1800 msnm en Panama occidental para determinar la distribución de ambas especies en bosque húmedo premontano intacto, en plantaciones de café con y sin sombra. Las dos especies fueron observadas recurrentemente en bosque y en plantaciones de café de sombra cercanos y lejanos al bosque. Consideramos que la retención de ciertas características del bosque en las plantaciones de café de sombra contribuye a la persistencia de estos organismos de bosque en ambientes modificados. Los árboles no solo proporcionan sombra que amortigua la temperatura, sino que proporcionan hojarasca y restos leñosos de troncos caídos. Tanto E. burchelli como L. praedator cazan en la hojarasca, E. burchelli utiliza restos leñosos para anidar (vivaques). Encontramos significativamente menos vivaques en plantaciones de café sin sombra al compararlos con bosque y plantaciones de café con sombra. Asimismo, la profundidad de la capa de hojarasca fue menor en plantaciones de café sin sombra en comparación con bosque y plantaciones de café con sombra. Nuestros resultados proporcionan la primera evidencia de que las plantaciones con sombra proporcionan hábitat adicional para E. burchelli y L. praedator, depredadores de la comunidad de artrópodos en la hojarasca. E. burchelli y L. praedator actúan como eslabones críticos entre especies de aves que se alimentan de hormigas y los artrópodos de la hojarasca, proporcionando un recurso alimenticio fácilmente explotado que de otra manera no estaría disponible para muchas aves. La continua transformación de plantaciones de café con sombra a plantaciones sin sombra pudiera tener efectos negativos sobre las hormigas arrieras y la biodiversidad asociada. [source] Non-enzymatic hydrolysis of fluorescein diacetate (FDA) in a Mediterranean oak (Quercus ilex L.) litterEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2008E. Alarcón-Gutiérrez Summary We show the presence of interfering substances when the total microbial activity in litter samples is measured with fluorescein diacetate (FDA), and we propose some methodological modifications to avoid such interference. Three distinct litter layers (the OhLn, the OhLv and the OhLf) of evergreen oak (Quercus ilex L.) were characterized by 13C CPMAS NMR and the spectra show that the recalcitrant aromatic and phenolic compounds increase with the degree of degradation of litter. A wide range of sources of interference in the hydrolysis of FDA was found. To understand the origin of this interference, sterilized litter materials (i.e. ,-irradiated or autoclaved) and a wide range of organic substances (i.e. amino acids, glucose, sorbitol and organic humic acids) were investigated. Insignificant differences on the FDA hydrolysis activity (FDA activity) were found in the ,-irradiated and non-irradiated OhLn litter, indicating that ,-irradiation does not destroy enzymes. Conversely, after heat-sterilization of litter, samples showed FDA activity corresponding to 60, 34.8 and 30.8% (in the OhLn, the OhLv and the OhLf layers, respectively) of that of control litters. This indicates the presence of non-enzymatic interfering substances in the FDA assays. As the humification and litter depth increased, hydrolysis of FDA due to interferences decreased, indicating degradation and/or chelation of interfering substances. We hypothesize that lysine, arginine, histidine and cysteine are mainly responsible for the hydrolysis of FDA. We suggest that the use of phosphate buffer (50 mm, pH 7.0) with incubation <,30 minutes, in combination with a temperature between 30 and 40°C, produces insignificant interference in the determination of the final FDA activity in litter samples. [source] Shrub effects on herbs and grasses in semi-natural grasslands: positive, negative or neutral relationships?GRASS & FORAGE SCIENCE, Issue 1 2008A. Pihlgren Abstract The present study investigated how the abundance and sexual reproduction of herbs and grasses relates to the presence of shrubs of Rosa dumalis in three semi-natural pastures in Sweden. Shrubs may affect grassland plants negatively by competition, positively by serving as grazing refuge, or neutrally. At different distances from shrubs of R. dumalis, data were collected on plant abundance, frequency of reproductive shoots, vegetation height and litter depth. In one grassland, data were collected on seedling density and frequency of reproductive shoots in the presence and absence of grazing. The shrubs functioned as grazing refuges with taller vegetation, deeper litter and higher probability of reproduction by plants. The overall number of plant species remained the same at all distances from shrubs. Most species showed a neutral relationship with shrubs. Proportionately, 0·08,0·26 of the species showed a negative pattern to shrubs and 0·14,0·30 a positive pattern. Seedling density was negatively correlated with litter depth and peaked at 60,90 cm from shrubs. Establishment of seedlings of small-seeded species was negatively related to shrubs probably because of thicker litter layer close to shrubs. The observed patterns were compared with different functional traits, such as Ellenberg values, plant height, growth form and Raunkiaer life form. Plant height from data in the literature was the trait that best explained the relationship of plant species to shrubs because tall species were more common in proximity to shrubs. It was concluded that shrubs increase the heterogeneity in grasslands and that intensive shrub-clearing may negatively affect biodiversity. [source] Quantifying the impact of soil water repellency on overland flow generation and erosion: a new approach using rainfall simulation and wetting agent on in situ soilHYDROLOGICAL PROCESSES, Issue 17 2007G. Leighton-Boyce Abstract The conventional view of soil water repellency is that it promotes overland flow and soil erosion, but this is not always borne out by observations. This study aimed to isolate the effects of repellency on long-unburnt and recently burnt terrain on infiltration, overland flow and erosion at the small plot scale (0·36 m2). Rainfall simulations (30 min; intensity 100 mm h,1), using untreated water, and water treated with surfactants to eliminate repellency, were conducted on in situ repellent soils in fire-prone Eucalyptus globulus plantations, north-central Portugal at (i) a long-unburnt site with and without litter, and (ii) a recently burnt site. On long-unburnt terrain, the mean overland flow coefficient (33%) was 16 times higher and mean slopewash was 23 times higher under repellent compared with wettable conditions. On recently burnt terrain, no overland flow was recorded under wettable conditions, while under repellent conditions the mean coefficient was 70%. The water storage capacity of the litter layer under 10-year-old eucalyptus stands for dry antecedent conditions was at least 3 mm water depth per cm litter depth, implying at least a delay to the onset of overland flow. Severe repellency (36% ethanol) was found to persist through a 30-min storm (100 mm h,1) when a litter layer was present. A continuous wetting front was observed in the upper ,1 cm of exposed soil, indicating a breakdown in repellency at the time of observation. Below ,1 cm, repellent, dry soil conditions generally persisted through the simulated storm event. A major implication is that prediction of hydrological impacts of repellency must also take into account the infiltration characteristics of any litter layer and any non-repellent soils, if present. Copyright © 2007 John Wiley & Sons, Ltd. [source] Present and past old-growth forests of the Lake Tahoe Basin, Sierra Nevada, USJOURNAL OF VEGETATION SCIENCE, Issue 4 2002M. Barbour Hickman (1993) for vascular plants; Furniss & Carolin (1977) for bark beetles; Hansen & Lewis (1997) for pathogens Abstract. We described 38 relictual old-growth stands , with data on the mortality, regeneration, floristic richness, fuel load and disease incidence in our study area in the Tahoe Basin of California and Nevada. The stands are within the lower and upper montane zones (1900,2400 m a.s.l.) and they are rare, occupying < 2% of the land in the Basin's watershed. Correlation matrices and ANOVAs of forest types and conifer species with environmental gradients revealed significant relationships with elevation, distance east of the Sierran crest, slope aspect, annual precipitation, date of complete snow melt, litter depth and degree of soil profile development. Pathogens, parasites and wood-boring insects were present on 23% of living trees; 16% of all trees were dead. We compared these stands to a reconstruction of pre-contact Basin forests and to ecologically analogous old-growth forests of Baja California that have never experienced fire suppression management. Currently, overstorey trees (> 180 yr old) in the Basin stands have ca. 33% cover, 54 m2.ha -1 basal area and 107 individuals.ha -1, values very similar to reconstructions of pre-contact Basin forests and to modern Baja California forests. Understorey trees (60,180 yr old), however, are several times more dense than historic levels and species composition is strongly dominated by A. concolor, regardless of the overstorey composition. The ratio of Pinus: Abies has increased , and the age structure of extant stands predicts that it will continue to increase , from approximately 1:1 in pre-contact time to 1:7 within the next century. Disease incidence and mortality in Baja forests were lower. Although we quantitatively defined current Basin old-growth forests , in terms of stand structure , we realize that our definition will differ from that of both past and future old-growth forests unless management protocols are changed. [source] Habitat Overlap and Facilitation in Tamarisk and Box Elder Stands: Implications for Tamarisk Control Using Native PlantsRESTORATION ECOLOGY, Issue 3 2010John M. DeWine Invasive plants are typically managed using top-down control techniques that focus on the removal of the target organism. Bottom-up control limits the resources available to the undesired species by manipulating disturbance, competition, and successional processes, and thus may prevent reinvasion. Tamarisk species (Tamarix sp.) have invaded riparian areas throughout western North America, resulting in expansive control efforts. A companion study has shown that a native competitor, Box elder (Acer negundo), is capable of outcompeting and killing established Tamarisk through light interception in canyons of Dinosaur National Monument (DNM), Colorado. The goal of this study was to determine the feasibility of using Box elder as a bottom-up control agent by (1) determining the distributional overlap of the two species in DNM; (2) determining if Tamarisk facilitates Box elder establishment; and (3) analyzing Box elder seedling survival across a range of physical gradients. The distribution of Tamarisk and Box elder overlapped considerably throughout the study area. Box elder seedlings were planted under Tamarisk canopies or areas with the canopy removed. Survival was significantly higher under Tamarisk canopies, indicating that Tamarisk facilitates Box elder seedling survival. Box elder seedling survival was tested across soil texture, litter depth, groundwater depth, and shade intensities indicative of conditions found in the canyons of DNM, and survival was high for all treatments. The manipulation of competitive and successional processes through the promotion of Box elder and other native tree establishment is suggested as a means of bottom-up Tamarisk control to complement traditional control techniques. [source] Ecological parameters of the leaf-litter frog community of an Atlantic Rainforest area at Ilha Grande, Rio de Janeiro state, BrazilAUSTRAL ECOLOGY, Issue 3 2007M. Van SLUYS Abstract The Atlantic Rainforest originally covered much of the Brazilian coast and is now reduced to approximately only 7% of its original area. Data on abundance distribution and microhabitat characteristics of anuran amphibians living on the forest floor leaf litter in the Atlantic Rainforest are scarce. In this study, we analysed the effect of litter depth and structure on the abundance and species richness of leaf-litter frogs in an area of Atlantic Rainforest at Ilha Grande, Rio de Janeiro State, south-eastern Brazil. We performed monthly samples (nocturnal and diurnal) from August 1996 to October 1997 using small (2 m × 1 m) plots. We sampled 234 plots, totalling 468 m2 of forest leaf litter. We estimated leaf-litter depth and the proportion of leaves in the plot and tested their effect on the total abundance of frogs and species richness using multiple regression analysis. We found 185 frogs from eight species: Brachycephalus (=Psyllophryne) didactylus (Izecksohn, 1971) (Brachycephalidae), Dendrophryniscus brevipollicatus Jiménez de la Espada 1871 (Bufonidae), Adenomera marmorata Steindachner 1867, Eleutherodactylus parvus (Girard 1853), Eleutherodactylus guentheri (Steindachner 1864), Eleutherodactylus binotatus (Spix 1824) and Zachaenus parvulus (Girard 1853) (Leptodactylidae), and Chiasmocleis sp. (Microhylidae). Brachycephalus didactylus was the most abundant species, with 91 individuals, whereas Dendrophryniscus brevipollicatus was the rarest, with two individuals. Mean litter depth and the proportion of leaves in the leaf litter were significantly related to frog abundance (R2 = 0.17; F2,107 = 10.779; P = 0.0001) and species richness (R2 = 0.11; F2,107 = 6.375; P = 0.002) indicating that microhabitat characteristics may affect local distribution and abundance of frogs in the forest floor. [source] Shell shape and habitat use in the North-west Pacific land snail Mandarina polita from Hahajima, Ogasawara: current adaptation or ghost of species past?BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2007SATOSHI CHIBA The endemic land snail genus Mandarina of the Ogasawara Islands provides an excellent model system to investigate adaptive radiation. Previously, it has been shown that coexisting species of the islands segregate by microhabitat, so that they are either predominantly found on the ground in relatively wet and sheltered sites, dry and exposed sites, or else are arboreal. Moreover, shell morphology correlates with microhabitat, so that species in wet and sheltered sites tend to have high-spired shells with a high aperture, and those in dry and exposed sites tend to have relatively low-spired shells with a wide aperture. We have now found that on Hahajima, Mandarina polita have variable shell morphology, and there is a correlation between morphology and the depth of leaf litter, as well as the presence/absence of other terrestrial species. Specifically, when high-spired terrestrial Mandarina ponderosa is present, M. polita tend to be low-spired and have a large aperture, indicative of character displacement. When M. ponderosa is absent, the shell shape of M. polita is much more variable, the overall spire is higher, individuals are found in deeper litter, and there is a strong correlation between litter depth and spire height. We argue that these patterns are due to local adaptation, but it remains possible that they are an artefact due to the ,ghost of species past'. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 149,159. [source] Impact of Flooding on the Species Richness, Density and Composition of Amazonian Litter-Nesting AntsBIOTROPICA, Issue 5 2009Amy L. Mertl ABSTRACT Litter-nesting ants are diverse and abundant in tropical forests, but the factors structuring their communities are poorly known. Here we present results of the first study to examine the impact of natural variation in flooding on a highly diverse (21 genera, 77 species) litter-nesting ant community in a primary Amazonian forest. Fifty-six 3 × 3 m plots experiencing strong variation in flooding and twenty-eight 3 × 3 m terra firme plots were exhaustively searched for litter-nesting ants to determine patterns of density, species richness and species composition. In each plot, flooding, litter depth, twig availability, canopy cover, plant density, percent soil nitrogen, carbon, and phosphorus were measured. Degree of flooding, measured as flood frequency and flood interval, had the strongest impact on ant density in flooded forest. Flooding caused a linear decrease in ant abundance, potentially due to a reduction of suitable nesting sites. However, its influence on species richness varied: low-disturbance habitat had species richness equal to terra firme forest after adjusting for differences in density. The composition of ant genera and species varied among flood categories; some groups known to contain specialist predators were particularly intolerant to flooding. Hypoponera STD10 appeared to be well-adapted to highly flooded habitat. Although flooding did not appear to increase species richness or abundance at the habitat scale, low-flooding habitat contained a mixture of species found in the significantly distinct ant communities of terra firme and highly flooded habitat. [source] Dung Beetle Assemblages and Seasonality in Primary Forest and Forest Fragments on Agricultural Landscapes in Budongo, UgandaBIOTROPICA, Issue 4 2009Philip Nyeko ABSTRACT Very little is known about the diversity of arthropods in the fast-disappearing fragments of natural forests in sub-Saharan Africa. This study investigated: (1) the influence of forest fragment characteristics on dung beetle species richness, composition, abundance, and diversity; and (2) the relationship between dung beetle assemblages and rainfall pattern. Beetles were sampled through 12 mo using dung baited pitfall traps. A total of 18,073 dung beetles belonging to three subfamilies and 45 species were captured. The subfamily Scarabaeinae was the most abundant (99%) and species rich (89%). Fast-burying tunnellers (paracoprids) were the most dominant functional group. Catharsius sesostris, Copris nepos, and Heliocopris punctiventris were the three most abundant species, and had the highest contributions to dissimilarities between forests. With few exceptions, dung beetle abundance, species richness, and diversity were generally higher in larger forest fragments (100,150 ha) than in smaller ones (10,50 ha) and the nature reserve (1042 ha). Forest fragment size had a highly significant positive relationship with beetle abundance, but only when the nature reserve is excluded in the analysis. Dung beetle abundance and species richness showed direct weak relationships with litter depth (positive) and groundcover (negative) but not tree density, tree species richness, and fragment isolation distance. Dung beetle abundance and species richness were strongly correlated with monthly changes in rainfall. Results of this study indicate that forest fragments on agricultural lands in the Budongo landscape, especially medium-sized (100,150 ha) ones, represent important conservation areas for dung beetles. [source] | |||||||||||||