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Undisturbed Sites (undisturbed + site)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Testing the Home-Site Advantage in Forest Trees on Disturbed and Undisturbed Sites

RESTORATION ECOLOGY, Issue 3 2010
Eleanor K. O'Brien
Restoration of plant populations is often undertaken using seed or plants from local sources because it is assumed they will be best adapted to the prevailing conditions. However, the effect of site disturbance on local adaptation has rarely been examined. We assessed local adaptation in three southwestern Australian forest tree species (Eucalyptus marginata, Corymbia calophylla, and Allocasuarina fraseriana) using reciprocal transplant trials at disturbed and undisturbed sites. Performance of plants within the trials was assessed over 2 years. Planting location accounted for the majority of the variation in most measures of performance, although significant variation of percent emergence among source populations was also detected. In all species, percent emergence and survival of plants sourced from Darling Range populations was significantly higher than that of plants from the Swan Coastal Plain, regions of contrasting edaphic and climatic environment. Survival of E. marginata over the first 18 months and emergence of C. calophylla were both higher in local plants, providing at least weak evidence for local adaptation. Where a local advantage was observed, the relative performance of local and nonlocal seed did not vary among disturbed and undisturbed sites. Evidence for enhanced establishment from local seed in at least one species leads us to recommend that where sufficient high-quality seed supplies exist locally, these should be used in restoration. We also recommend longer-term studies to include the possibility of local adaptation becoming evident at later life history stages. [source]

Abandoned anthills of Formica polyctena and soil heterogeneity in a temperate deciduous forest: morphology and organic matter composition

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2001
S. M. Kristiansen
Summary Ants can modify the properties of soil when they build their nests. We have investigated the degree and persistency of changes of soil morphology and chemistry in abandoned anthills in a temperate, deciduous wood in Jutland, Denmark. For this purpose, we sampled surface soils (0,10 cm) from each of five abandoned anthills (Formica polyctena Förster) and adjacent undisturbed sites, where anthills covered about 0.5% of the surface area. In addition, one soil profile in an abandoned anthill was sampled for morphological descriptions. All samples were analysed for pH, C, N, lignin-derived phenol, and cellulosic and non-cellulosic carbohydrate concentrations. The results showed that soils under the anthills were enriched in organic matter, were yellower and showed features of Podzol degradation. Former Podzols had to be reclassified to Umbrisols or Arenosols, whereas anthills on Luvisols affected soil classification only at the subdivision level. The C/N ratio and soil pH were not significantly affected by the ants' activity. However, lignin-derived phenols and cellulosic polysaccharides were enriched inside the mounds by a factor of 6 and 7, respectively. This probably reflected collection of woody debris for nest construction while the nest was occupied, and large input of C from an increased root density. The degree of changes in the quality of the organic matter decreased with time since abandonment, but changes were still detectable within anthills left 20 years ago. As ant colonies are concentrated, and move regularly on a decadal timescale, formation of Formica anthills has an intrinsic influence on the heterogeneity of the soil within this forest ecosystem. [source]

The potential roles of biological soil crusts in dryland hydrologic cycles

HYDROLOGICAL PROCESSES, Issue 15 2006
Jayne Belnap
Abstract Biological soil crusts (BSCs) are the dominant living cover in many drylands of the world. They possess many features that can influence different aspects of local hydrologic cycles, including soil porosity, absorptivity, roughness, aggregate stability, texture, pore formation, and water retention. The influence of biological soil crusts on these factors depends on their internal and external structure, which varies with climate, soil, and disturbance history. This paper presents the different types of biological soil crusts, discusses how crust type likely influences various aspects of the hydrologic cycle, and reviews what is known and not known about the influence of biological crusts on sediment production and water infiltration versus runoff in various drylands around the world. Most studies examining the effect of biological soil crusts on local hydrology are done by comparing undisturbed sites with those recently disturbed by the researchers. Unfortunately, this greatly complicates interpretation of the results. Applied disturbances alter many soil features such as soil texture, roughness, aggregate stability, physical crusting, porosity, and bulk density in ways that would not necessarily be the same if crusts were not naturally present. Combined, these studies show little agreement on how biological crusts affect water infiltration or runoff. However, when studies are separated by biological crust type and utilize naturally occurring differences among these types, results indicate that biological crusts in hyperarid regions reduce infiltration and increase runoff, have mixed effects in arid regions, and increase infiltration and reduce runoff in semiarid cool and cold drylands. However, more studies are needed before broad generalizations can be made on how biological crusts affect infiltration and runoff. We especially need studies that control for sub-surface soil features such as bulk density, micro- and macropores, and biological crust structure. Unlike the mixed effects of biological crusts on infiltration and runoff among regions, almost all studies show that biological crusts reduce sediment production, regardless of crust or dryland type.Copyright © 2006 John Wiley & Sons, Ltd. [source]

Another diet of worms: the applicability of polychaete feeding guilds as a useful conceptual framework and biological variable

MARINE ECOLOGY, Issue 3-4 2005
Paulo Roberto Pagliosa
Abstract A fundamental question in guild studies is how to separate species into guilds. In a seminal manuscript, Fauchald & Jumars [Oceanography and Marine Biology Annual Review17 (1979) 193] summarized polychaete feeding biology and proposed a conceptual framework to test hypotheses on the sympatric occurrence of congeners with limited morphological differentiation. Twenty-six years after this publication, few studies have tested the validity and practical functioning of this scheme of polychaete feeding guilds and then only using part of the classification. The objective of the present study was to analyze the applicability of polychaete feeding guilds to ecological and environment assessments. Two data sets from Santa Catarina Island Bay, southern Brazil, were used. The first data set deals with spatial distribution of natural polychaete assemblages along the bay. The second data set treats fauna in urbanized versus relatively pristine mangroves. Multivariate analysis showed similar patterns in sample groups formed using guilds or densities and composition data. The role of feeding guilds in benthic systems was assessed through comparison with environmental variables. The polychaete assemblage from the Bay was related to sediment type. Motile and discretely motile carnivores and herbivores with jawed probosces matched coarse sands; surface deposit feeders and filter feeders were found in fine sands; and surface and subsurface deposit feeders and carnivores, all with soft probosces matched silt and clay sediments. The data analyses in mangroves showed surface deposit feeders and filter feeders in undisturbed sites and omnivorous species in disturbed ones. The polychaete feeding guilds appear relevant to assembly rules based on resource availability, to resource partitioning and to interspecific competition. [source]