JOURNAL OF PHYCOLOGY, Issue 4 2009
Helmut Hillebrand
Grazer control of periphyton biomass has been addressed in numerous experimental studies in all kinds of aquatic habitats. In this meta-analysis, the results of 865 experiments are quantitatively synthesized in order to address the following questions: (i) Do lotic, lentic, and marine ecosystems differ in their degree of grazer control of periphyton biomass? (ii) Which environmental variables affect the degree of grazer control? (iii) How much does the result of these experiments depend on facets of experimental design? Across all ecosystems, the grazers removed on average 59% of the periphyton biomass, with grazing being significantly stronger for laboratory (65%) than for field (56%) experiments. Neither field nor lab experiments showed a significant difference among lotic, lentic, and coastal habitats. Among different taxonomic consumer groups, crustaceans (amphipods and isopods) and trichopteran larvae removed the highest proportion of periphyton biomass. Grazer effects increased with increasing algal biomass, with decreasing resource availability and with increasing temperature, especially in field experiments. Grazer effects also increased with increasing total grazer biomass in field experiments but showed the opposite trend in lab experiments, indicating a tendency toward overcrowded lab experiments. Other aspects of experimental design, such as cage type, size, and duration of the study, strongly affected the outcome of the experiments, suggesting that much care has to be placed on the choice of experimental design. [source]

LANDSCAPE-SCALE ANALYSIS AND MANAGEMENT OF CUMULATIVE IMPACTS TO RIPARIAN ECOSYSTEMS: PAST, PRESENT, AND FUTURE,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2001
Eric D. Stein
ABSTRACT: Analyses of cumulative impacts to riparian systems is an important yet elusive goal. Previous analyses have focused on comparing the number of hectares impacted to the number of hectares restored, without addressing the loss of riparian function or the effect of the spatial distribution of impacts. This paper presents an analysis of the spatial distribution of development-related impacts to riparian ecosystems, that were authorized under Section 404 of the Clean Water Act. Impacts on habitat structure, contiguity, and landscape context were evaluated using functional indices scaled to regional reference sites. Impact sites were mapped using GIS and analyzed for spatial associations. Positive spatial autocorrelation (i.e. clustering of impact sites) resulted from the piecemeal approach to impact assessment, which failed to prevent cumulative impacts. Numerous small projects in close proximity have resulted in adverse impacts to entire stream reaches or have fragmented the aquatic resources to a point where overall functional capacity is impaired. Additionally, the ecological functions of unaffected areas have been diminished due to their proximity to degraded areas. A proactive approach to managing cumulative impacts is currently being used in Orange County, California as part of a Corps of Engineers sponsored Special Area Management Plan (SAMP). The SAMP process is evaluating the ecological conditions and physical processes of the study watersheds and attempting to plan future development in a manner that will guard against cumulative impacts. [source]

STUDYING TROPHIC ECOLOGY IN MARINE ECOSYSTEMS USING FATTY ACIDS: A PRIMER ON ANALYSIS AND INTERPRETATION

MARINE MAMMAL SCIENCE, Issue 4 2006
Suzanne M. Budge
First page of article [source]

INTRODUCTION TO SPECIAL ISSUE: INTEGRATED MODELING OF ECONOMIES AND ECOSYSTEMS

NATURAL RESOURCE MODELING, Issue 1 2007
John Tschirhart
[source]

After the Sheep are Gone, Restoring an Invaded Ecosystem

CONSERVATION, Issue 4 2001
Jason Van Driesche
[source]

Beyond Species Richness: Community Similarity as a Measure of Cross-Taxon Congruence for Coarse-Filter Conservation

CONSERVATION BIOLOGY, Issue 1 2004
JEFFREY C. SU
Species richness is only one measure of species diversity, however, and recent studies suggest that investigations of cross-taxon congruence should consider a broader range of assessment techniques. The cross-taxon congruence of community similarity between sites among taxa has rarely been examined and may be the most relevant measure of species diversity in the context of coarse-filter conservation strategies. We examined cross-taxon congruence patterns of species richness and community similarity (Bray-Curtis similarity) among birds, butterflies, and vascular plants in montane meadow habitats in the Greater Yellowstone Ecosystem. Although patterns of species richness (Spearman rank correlation) varied between taxa, we consistently found a positive correlation in community similarity (Mantel test) between all pair-wise comparisons of the three taxa (e.g., sites with similar bird communities also had similar butterfly communities). We suggest that the success of a surrogate taxon depends on the technique used to assess surrogacy and the specific approach to conservation planning. In the context of coarse-filter conservation, measures of community similarity may be more appropriate than measures of species richness. Furthermore, the cross-taxon congruency of community similarity in our study suggests that coarse-filter conservation may be tenable in montane meadow communities. Resumen:,El uso de un taxón sustituto en la planeación de la conservación se ha vuelto cuestionable porque información reciente sugiere que la correlación de riqueza de especies entre pares de taxones es altamente variable taxonómica y geográficamente. Sin embargo, la riqueza de especies es solo una medida de la diversidad de especies, y estudios recientes sugieren que las investigaciones de congruencia trans-taxón debieran considerar una mayor variedad de técnicas de evaluación. La congruencia trans-taxón de la similitud de comunidades entre sitios entre taxones rara vez se ha examinado y puede ser la medida de diversidad de especies más relevante en el contexto de las estrategias de conservación de grano grueso. Examinamos patrones de congruencia trans-taxón de riqueza de especies y similitud de comunidades (similitud Bray-Curtis) en aves, mariposas y plantas vasculares en hábitats de praderas montanas en el Ecosistema Greater Yellowstone. Aunque los patrones de riqueza de especies (correlación Spearman de rangos) variaron entre especies, encontramos consistentemente una correlación positiva en la similitud de la comunidad (prueba de Mantel) entre todas las comparaciones de pares de los tres taxones (es decir, los sitios con comunidades similares de aves también tenían comunidades similares de mariposas). Sugerimos que el éxito de un taxón sustituto depende de la técnica utilizada para evaluar la sustitución y el abordaje específico de la planeación de conservación. En el contexto de la conservación de grano grueso, pueden ser más apropiadas las medidas de similitud de comunidades que las medidas de riqueza de especies. Más aun, la congruencia trans-taxón de similitud de comunidades en nuestro estudio sugiere que la conservación de grano grueso puede ser justificable en comunidades de praderas montanas. [source]

How do individual transferable quotas affect marine ecosystems?

FISH AND FISHERIES, Issue 1 2009
Trevor A Branch
Abstract Published papers were reviewed to assess ecosystem impacts of individual transferable quotas (ITQs) and other dedicated access systems. Under ITQs, quota shares increase with higher abundance levels, thus fishers may request lower total allowable catches (TACs) and pay for monitoring and research that improves fishery sustainability. Mortality on target species generally declines because catches are closer to TACs and because ghost fishing through lost and abandoned gear decreases. High-grading and discarding often decline, but may increase if landings (and not catches) count against ITQs and when there is little at-sea enforcement. Overall, ITQs positively impact target species, although collapses can occur if TACs are set too high or if catches are routinely allowed to exceed TACs. Fishing pressure may increase on non-ITQ species because of spillover from ITQ fisheries, and in cases where fishers anticipate that future ITQ allocations will be based on catch history and therefore increase their current catches. Ecosystem and habitat impacts of ITQs were only sparsely covered in the literature and were difficult to assess: ITQs often lead to changes in total fishing effort (both positive and negative), spatial shifts in effort, and fishing gear modifications. Stock assessments may be complicated by changes in the relationship between catch per unit effort, and abundance, but ITQ participants will often assist in improving data collection and stock assessments. Overall, ITQs have largely positive effects on target species, but mixed or unknown effects on non-target fisheries and the overall ecosystem. Favourable outcomes were linked to sustainable TACs and effective enforcement. [source]

Predicting population consequences of ocean climate change for an ecosystem sentinel, the seabird Cassin's auklet

GLOBAL CHANGE BIOLOGY, Issue 7 2010
SHAYE G. WOLF
Abstract Forecasting the ecological effects of climate change on marine species is critical for informing greenhouse gas mitigation targets and developing marine conservation strategies that remain effective and increase species' resilience under changing climate conditions. Highly productive coastal upwelling systems are predicted to experience substantial effects from climate change, making them priorities for ecological forecasting. We used a population modeling approach to examine the consequences of ocean climate change in the California Current upwelling ecosystem on the population growth rate of the planktivorous seabird Cassin's auklet (Ptychoramphus aleuticus), a demographically sensitive indicator of marine climate change. We use future climate projections for sea surface temperature and upwelling intensity from a regional climate model to forecast changes in the population growth rate of the auklet population at the important Farallon Island colony in central California. Our study projected that the auklet population growth rate will experience an absolute decline of 11,45% by the end of the century, placing this population on a trajectory toward extinction. In addition, future changes in upwelling intensity and timing of peak upwelling are likely to vary across auklet foraging regions in the California Current Ecosystem (CCE), producing a mosaic of climate conditions and ecological impacts across the auklet range. Overall, the Farallon Island Cassin's auklet population has been declining during recent decades, and ocean climate change in this century under a mid-level emissions scenario is projected to accelerate this decline, leading toward population extinction. Because our study species has proven to be a sensitive indicator of oceanographic conditions in the CCE and a powerful predictor of the abundance of other important predators (i.e. salmon), the significant impacts we predicted for the Cassin's auklet provide insights into the consequences that ocean climate change may have for other plankton predators in this system. [source]

Ecosystem,atmosphere exchange of CH4 and N2O and ecosystem respiration in wetlands in the Sanjiang Plain, Northeastern China

GLOBAL CHANGE BIOLOGY, Issue 3 2009
CHANGCHUN SONG
Abstract Natural wetlands are critically important to global change because of their role in modulating atmospheric concentrations of CO2, CH4, and N2O. One 4-year continuous observation was conducted to examine the exchanges of CH4 and N2O between three wetland ecosystems and the atmosphere as well as the ecosystem respiration in the Sanjiang Plain in Northeastern China. From 2002 to 2005, the mean annual budgets of CH4 and N2O, and ecosystem respiration were 39.40 ± 6.99 g C m,2 yr,1, 0.124 ± 0.05 g N m,2 yr,1, and 513.55 ± 8.58 g C m,2 yr,1 for permanently inundated wetland; 4.36 ± 1.79 g C m,2 yr,1, 0.11 ± 0.12 g N m,2 yr,1, and 880.50 ± 71.72 g C m,2 yr,1 for seasonally inundated wetland; and 0.21 ± 0.1 g C m,2 yr,1, 0.28 ± 0.11 g N m,2 yr,1, and 1212.83 ± 191.98 g C m,2 yr,1 for shrub swamp. The substantial interannual variation of gas fluxes was due to the significant climatic variability which underscores the importance of long-term continuous observations. The apparent seasonal pattern of gas emissions associated with a significant relationship of gas fluxes to air temperature implied the potential effect of global warming on greenhouse gas emissions from natural wetlands. The budgets of CH4 and N2O fluxes and ecosystem respiration were highly variable among three wetland types, which suggest the uncertainties in previous studies in which all kinds of natural wetlands were treated as one or two functional types. New classification of global natural wetlands in more detailed level is highly expected. [source]

Regional-scale measurements of CH4 exchange from a tall tower over a mixed temperate/boreal lowland and wetland forest

GLOBAL CHANGE BIOLOGY, Issue 9 2003
Cindy Werner
The biosphere,atmosphere exchange of methane (CH4) was estimated for a temperate/boreal lowland and wetland forest ecosystem in northern Wisconsin for 1997,1999 using the modified Bowen ratio (MBR) method. Gradients of CH4 and CO2 and CO2 flux were measured on the 447-m WLEF-TV tower as part of the Chequamegon Ecosystem,Atmosphere Study (ChEAS). No systematic diurnal variability was observed in regional CH4 fluxes measured using the MBR method. In all 3 years, regional CH4 emissions reached maximum values during June,August (24±14.4 mg m,2 day,1), coinciding with periods of maximum soil temperatures. In 1997 and 1998, the onset in CH4 emission was coincident with increases in ground temperatures following the melting of the snow cover. The onset of emission in 1999 lagged 100 days behind the 1997 and 1998 onsets, and was likely related to postdrought recovery of the regional water table to typical levels. The net regional emissions were 3.0, 3.1, and 2.1 g CH4 m,2 for 1997, 1998, and 1999, respectively. Annual emissions for wetland regions within the source area (28% of the land area) were 13.2, 13.8, and 10.3 g CH4 m,2 assuming moderate rates of oxidation of CH4 in upland regions in 1997, 1998, and 1999, respectively. Scaling these measurements to the Chequamegon Ecosystem (CNNF) and comparing with average wetland emissions between 40°N and 50°N suggests that wetlands in the CNNF emit approximately 40% less than average wetlands at this latitude. Differences in mean monthly air temperatures did not affect the magnitude of CH4 emissions; however, reduced precipitation and water table levels suppressed CH4 emission during 1999, suggesting that long-term climatic changes that reduce the water table will likely transform this landscape to a reduced source or possibly a sink for atmospheric CH4. [source]

Aquatic Microbial Ecology: Water Desert, Microcosm, Ecosystem.

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 4-5 2008
What's Next?
Abstract Aquatic microbial ecology aims at nothing less than explaining the world from "ecological scratch". It develops theories, concepts and models about the small and invisible living world that is at the bottom of every macroscopic aquatic system. In this paper we propose to look at the development of Aquatic Microbial Ecology as a reiteration of classical (eukaryotic) limnology and oceanography. This was conceptualized moving historically from the so-called water desert to microcosm to ecosystem. Each of these concepts characterizes a particular historical field of knowledge that embraces also practices and theories about living beings in aquatic environments. Concerning the question of "who is there", however, Aquatic Microbial Ecology historically developed in reverse order. Repetition, reiteration and replication notwithstanding, Aquatic Microbial Ecology has contributed new ideas, theories and methods to the whole field of ecology as well as to microbiology. The disciplining of Aquatic Microbial Ecology happened in the larger field of plankton biology, and it is still attached to this biological domain, even conceiving of itself very self-consciously as a discipline of its own. Today, Aquatic Microbial Ecology as a discipline is much broader than plankton ecology ever was, for it includes not only oceans and freshwaters but also benthic, interstitial and groundwater systems. The success of Aquatic Microbial Ecology is expressed by its influence on other fields in ecology. The challenge is to further develop its theoretical and methodological features while at the same time contributing to current pressing problems such as climate change or the management of global water resources. And then it may not be fanciful to suppose that even in the year nineteen hundred and nineteen a great number of minds are still only partially lit up by the cold light of knowledge. It is the most capricious illuminant. They are still apt to ruminate, without an overpowering bias to the truth, whether a kingfisher's body shows which way the wind blows; whether an ostrich digests iron; whether owls and ravens herald ill-fortune; and the spilling of salt bad luck; what the tingling of ears forebodes, and even to toy pleasantly with more curious speculations as to the joints of elephants and the politics of storks, which came within the province of the more fertile and better-informed brain of the author (1919) Virginia Woolf from the essay "Reading", In: Leonard Woolf (ed.), 1950: The Captain's Death Bed and Other Essays, , London: Hogarth Press, p. 157. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The Ratios of Carbon, Nitrogen, and Phosphorus in a Wetland Coastal Ecosystem of Southern India

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2003
Lizen Mathews
Abstract The fertility of the coastal and estuarine waters is of great concern because of its influence on the productivity of these waters. Seasonal variations in the distribution of organic carbon, total nitrogen and total phosphorus in the sediments of Kuttanad Waters, a part of the tropical Cochin Estuary on the south west coast of India, are examined to identify the contribution of sediments to the fertility of the aquatic systems. The adjoining region has considerable agricultural activity. The fresh water zones had higher quantities of silt and clay whereas the estuarine zone was more sandy. Organic carbon, total phosphorus and total nitrogen were higher in the fresh water zones and lower in the estuarine zones. Total phosphorus and organic carbon showed the lowest values during monsoon periods. No significant trends were observed in the seasonal distributions of total nitrogen. Ratios of C/N, C/P and N/P, and the phosphorus and nitrogen content indicate significant modification in the character of the organic matter. Substantial amounts of the organic matter can contribute to reducing conditions and modify diagenetic processes. [source]

Ecosystem functioning in stream assemblages from different regions: contrasting responses to variation in detritivore richness, evenness and density

JOURNAL OF ANIMAL ECOLOGY, Issue 3 2008
B. G. McKie
Summary 1The diversity of species traits in a biological assemblage varies not only with species richness, but also with species evenness and organism density, which together influence the concentration of traits within functional guilds. Potential trait diversity at local scales is also constrained by the regional species pool. Implications of such variation for spatio-temporal variability in biodiversity,ecosystem functioning relationships are likely to be complex, but are poorly understood. 2In microcosm experiments conducted at laboratories in Sweden, Ireland and Romania, we investigated effects of species richness, evenness and density of stream-living detritivores on two related processes: detritivore leaf-processing efficiency (LPE) and growth. Assemblage composition varied among laboratories: one taxonomic order (Plecoptera) was studied in Sweden, whereas two orders, encompassing wider trait variation, were studied in Romania (Trichoptera and Plecoptera) and Ireland (Trichoptera and Isopoda). 3Relationships between density and both LPE and growth ranged from negative to positive across the study species, highlighting the potential for density-dependent variation in process rates to alter ecosystem functioning, but indicating that such effects depend on species identity. 4LPE varied with species diversity in the two more heterogeneous assemblages, but whereas LPE in the Romanian study was generally enhanced as richness increased, LPE in the Irish study increased only in less-even polycultures dominated by particular species. Transgressive overyielding was detected in the Irish experiment, indicating complementary resource use and/or facilitation (complementarity). These mechanisms could not be distinguished from the selection effect in the Romanian study. 5Growth was elevated in Romanian species mixtures, reflecting positive complementarity, but lower than expected growth in some Swedish mixtures was associated with negative complementarity, indicating interspecific interference competition. 6Our results emphasize the potential importance of detritivore diversity for stream ecosystem functioning, but both the effects of diversity on the studied processes, and the mechanisms underlying those effects, were specific to each assemblage and process. Such variability highlights challenges in generalizing impacts of diversity change for functional integrity in streams and other ecosystems in which the occurrence of important species traits fluctuates over relatively small spatio-temporal scales. [source]

A framework for assessing the biodiversity and fishery aspects of marine reserves

JOURNAL OF APPLIED ECOLOGY, Issue 4 2009
Phillip S. Levin
Summary 1. ,Resource management agencies are often charged with managing natural resources for economic and social goals, while also protecting and conserving biodiversity and ecosystem function. However, this may not always be possible. Ecosystem-based management is frequently suggested as a way to achieve multiple objectives in resource management and requires that trade-offs among conflicting objectives be identified and an effective means to utilize these trade-offs developed. 2. ,We examine the relationship between area and species richness in a diverse assemblage of fishes along the US West Coast and then use parameters from this relationship as input for a model that considers trade-offs between fisheries yield and the number of species protected by different management strategies. 3. ,The species,area relationship (S = cAz) for fishes along the US Pacific coast is well described by the relationship S = 16·18A0·226. 4. ,There are nearly linear trade-offs between diversity and yield when fishing effort is low. However, the trade-offs become nonlinear as fishing effort increases and imposing MPAs increases both the conservation and fisheries value of the system when the system is overfished. 5. ,Synthesis and applications. Solving conflicts between fisheries and conservation requires attention as to how conservation benefits accrue as fishing effort is reduced. However, scientists often lack quantitative information about the trade-offs inherent in human activities such as fisheries. The approach we develop here can begin to help frame the questions to be posed and evaluate the likely consequences of different management options. [source]

Ecosystem to regional impacts of introduced pests and pathogens: historical context, questions and issues

JOURNAL OF BIOGEOGRAPHY, Issue 10-11 2002
David A. Orwig
First page of article [source]

Participatory wildlife surveys in communal lands: a case study from Simanjiro, Tanzania

AFRICAN JOURNAL OF ECOLOGY, Issue 3 2010
Fortunata U. Msoffe
Abstract It is widely accepted that protected areas alone are not sufficient to conserve wildlife populations particularly for migratory or wide-ranging species. In this study, we assess the population density of migratory species in the Tarangire,Simanjiro Ecosystem by conducting a ground census using DISTANCE sampling. We focus on the Simanjiro Plains which are used as a dispersal area by wildebeest (Connochaetes taurinus) and zebra (Equus burchellii). We demonstrate that DISTANCE sampling can provide precise estimates of population density and is an affordable method for monitoring wildlife populations over time. We stress the importance of involving local communities in monitoring programmes across landscapes that incorporate communal lands as well as protected areas. Résumé On reconnaît généralement que les aires protégées ne suffisent pas, seules, à préserver les populations de faune sauvage, particulièrement celles d'espèces migratrices ou très largement distribuées. Dans cette étude, nous évaluons la densité de population d'espèces migratrices de l'Ecosystème Tarangire-Simanjiro en réalisant un recensement au sol recourant à l'échantillonnage par distance. Nous nous concentrons sur les plaines de Simanjiro qui sont utilisées comme aire de dispersion des gnous Connochaetes taurinus et des zèbres Equus burchellii. Nous montrons que l'échantillonnage par distance peut donner des estimations précises de la densité d'une population et que c'est une méthode accessible pour suivre des populations sauvages dans le temps. Nous soulignons l'importance d'impliquer les communautés locales dans les programmes de suivi, dans des paysages qui intègrent des terres publiques aussi bien que des aires protégées. [source]

Density and habitat associations of Henslow's Sparrows wintering in saline soil barrens in southern Arkansas

JOURNAL OF FIELD ORNITHOLOGY, Issue 4 2008
William C. Holimon
ABSTRACT Although the habitat requirements of breeding populations of Henslow's Sparrow (Ammodramus henslowii) have been examined, less is known about their habitat requirements and ecology during the nonbreeding season. We estimated population densities and quantified habitat associations of Henslow's Sparrows wintering in saline soil barrens in southern Arkansas. Densities of Henslow's Sparrows in the saline soil barrens were similar to those in the Longleaf Pine (Pinus palustris) Ecosystem of the southeastern United States, considered by many to be their primary wintering habitat. Henslow's Sparrows were closely associated with open areas with greater cover of Aristida spp. and globe beaksedge (Rhynchospora globularis), greater stem density at 11,20 cm above ground, more lichens, more herbaceous cover, more bare ground, greater occurrence of little bluestem (Schizacyrium scoparium) as the tallest vegetation, less moss, and less shrub cover than randomly selected sites. In contrast to the results of studies conducted in the Longleaf Pine Ecosystem, the presence of Henslow's Sparrows in our study was not correlated with the height of the tallest vegetation. Our results indicate that saline soil barrens of southern Arkansas support a high density of wintering Henslow's Sparrows and do so for longer postdisturbance periods than longleaf pine savanna. We also found that stem density near the ground was similar to that reported from longleaf pine savanna, but only about half that observed on their breeding grounds. Areas used by Henslow's Sparrows had more lichen and less moss cover, suggesting that those areas were drier than random sites within the barrens. Further research is needed to determine if large populations of Henslow's Sparrows winter in other saline soil barrens and if fire influences habitat associations and densities in the barrens. SINOPSIS Aunque los requisitos de hábitat para las poblaciones reproductivas de Ammodramus henslowii han sido determinadas, se conoce muy poco sobre su ecología y requerimientos de hábitat durante la temporada no-reproductiva. Estimamos la densidad poblacional y cuantificamos el hábitat asociado a Gorrión de Henslow que pasan el invierno en un salitral con suelo empobrecido en el sur de Arkansas. La densidad de las aves en el salitral resultó similar a lo encontrado en Ecosistemas de Pinos (Pinus palustris) en el sureste de los EUA, considerado por muchos como el principal hábitat invernal para la especie. Los gorriones estuvieron altamente asociados a áreas abiertas con covertura de Aristida spp. y Rhynchospora globularis, con mayor densidad de tallos, altura entre 11,20 cm sobre el suelo, mayor cantidad de líquenes, mayor cubierta herbácea, más suelo desnudo, mayor presencia de Schzacyrium scoparium (como la vegetación de mayor tamaño), menos musgos, y menos arbustos que localidades seleccionadas al azar. En contraste a los resultados de estudios conducidos en Ecosistemas de Pinos, la presencia del gorrión en nuestra área de estudio no estuvo correlacionada con la altura de la vegetación de mayor tamaño. Nuestros resultados indican que las salinas en Arkansas sostienen una alta densidad de aves invernales, y lo hacen por periodos más largos, después de disturbios, que en las savanas de pinos. También encontramos que la densidad de tallos, cerca del suelo, era similar a la informada en savanas de pinos, pero tan solo la mitad de lo indicado para lugares en donde las aves se reproducen. Las áreas utilizadas tienen más líquenes, pero menos musgos, lo que sugiere que dichas áreas son más secas que lugares con suelo empobrecido muestreados al azar. Se necesitan más trabajos para determinar si otras grandes poblaciones del gorrión de Henslow pasan el invierno en otras salinas con suelos empobrecidos y si eventos como fuegos incluyen en la asociación del hábitat y densidades en los lugares con suelo empobrecido. [source]

Significant Achievements in Protection and Restoration of Alpine Grassland Ecosystem in Northern Tibet, China

RESTORATION ECOLOGY, Issue 3 2009
Qing-zhu Gao
Abstract Alpine grassland is a fragile ecosystem, and a large area of this grassland type has been severely degraded in Northern Tibet, to the extent that it has become the primary ecological problem in the region. Various levels of government, including the national central government, the Tibetan Autonomous Region government, and the Nagqu Prefecture government have worked together to achieve alpine grassland ecosystem protection and prevent grassland degradation. These efforts have resulted in significant ecological, social, and economic benefits in Northern Tibet. [source]

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

RESTORATION ECOLOGY, Issue 2007
Jonathan D. Majer
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. [source]

Landscape linkages and conservation planning for the black bear in west-central Florida

ANIMAL CONSERVATION, Issue 1 2004
Jeffery L. Larkin
The Greater Chassahowitzka black bear population is the smallest documented in North America with fewer than 20 individuals. Its future depends on landscape linkages with other bear populations that are separated by denatured habitat. We used a Geographic Information System (GIS) to identify potential landscape linkages between this isolated population and six others in Florida. Pathway lengths ranged from 60,194 km with varying potentials for facilitating black bear dispersal. Each pathway incorporated 35,88% conservation land and encountered at least 11 dispersal bottlenecks. Even pathways that incorporated extensive conservation land encountered bottlenecks that make these linkages potentially unviable. All six pathways, however, passed through ,95% core black bear habitat. Thus, the infrastructure for a conservation network is still largely intact. The Suwannee pathway provides the best opportunity to restore connectivity between the Greater Chassahowitzka Ecosystem (GCE) and a southward colonising bear population in the Big Bend region. However, intensification of development poses an immediate threat to maintaining connectivity between the GCE and other bear populations in Florida. Through immediate strategic planning and active conservation and restoration measures, many of the generated pathways can provide long-term connectivity. Least-cost path analyses can aid in the conservation of wide-ranging animals by providing managers with a science-based, empirically derived blueprint of potential landscape linkages. [source]

On the Karst Ecosystem

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2001
Yuan Daoxian
Abstract In this paper the author gives a definition of the karst ecosystem and discusses the characteristics of the karst environment and karst ecosystem and the relationship between life and the karst environment. Finally he clarifies the structure, driving force and functions of the karst system. [source]

Protagonists of Healthy Ecosystems

CONSERVATION BIOLOGY, Issue 3 2007
Norman Owen-Smith
No abstract is available for this article. [source]

Motivations for the Restoration of Ecosystems

CONSERVATION BIOLOGY, Issue 2 2006
ANDRE F. CLEWELL
cambio climático; capital natural; restauración ecológica Abstract:,The reasons ecosystems should be restored are numerous, disparate, generally understated, and commonly underappreciated. We offer a typology in which these reasons,or motivations,are ordered among five rationales: technocratic, biotic, heuristic, idealistic, and pragmatic. The technocratic rationale encompasses restoration that is conducted by government agencies or other large organizations to satisfy specific institutional missions and mandates. The biotic rationale for restoration is to recover lost aspects of local biodiversity. The heuristic rationale attempts to elicit or demonstrate ecological principles and biotic expressions. The idealistic rationale consists of personal and cultural expressions of concern or atonement for environmental degradation, reengagement with nature, and/or spiritual fulfillment. The pragmatic rationale seeks to recover or repair ecosystems for their capacity to provide a broad array of natural services and products upon which human economies depend and to counteract extremes in climate caused by ecosystem loss. We propose that technocratic restoration, as currently conceived and practiced, is too narrow in scope and should be broadened to include the pragmatic rationale whose overarching importance is just beginning to be recognized. We suggest that technocratic restoration is too authoritarian, that idealistic restoration is overly restricted by lack of administrative strengths, and that a melding of the two approaches would benefit both. Three recent examples are given of restoration that blends the technocratic, idealistic, and pragmatic rationales and demonstrates the potential for a more unified approach. The biotic and heuristic rationales can be satisfied within the contexts of the other rationales. Resumen:,Las razones por la que los ecosistemas deben ser restaurados son numerosas, dispares, generalmente poco sustentadas, y comúnmente poco apreciadas. Ofrecemos una tipología en la que estas razones,o motivaciones,son ordenadas entre cinco razonamientos: tecnocrático, biótico, heurístico, idealista y pragmático. El razonamiento tecnocrático se refiere a la restauración que es llevada a cabo por agencias gubernamentales u otras grandes organizaciones para satisfacer misiones y mandatos institucionales específicos. El razonamiento biótico de la restauración es la recuperación de aspectos perdidos de la biodiversidad local. El razonamiento heurístico intenta extraer o demostrar principios ecológicos y expresiones bióticas. El razonamiento idealista consiste de expresiones personales y culturales de la preocupación o reparación de la degradación ambiental, reencuentro con la naturaleza y/o cumplimiento espiritual. El razonamiento pragmático busca recuperar o reparar ecosistemas por su capacidad de proporcionar una amplia gama de servicios y productos naturales de la que dependen las economías humanas y para contrarrestar extremos en el clima causados por la pérdida de ecosistemas. Proponemos que la restauración tecnocrática, como se concibe y practica actualmente, es muy corta en su alcance y debiera ampliarse para incluir al razonamiento pragmático, cuya importancia apenas comienza a ser reconocida. Sugerimos que la restauración tecnocrática es demasiado autoritaria, que la restauración idealista esta muy restringida por la falta de fortalezas administrativas, y que una mezcla de los dos enfoques podría beneficiar a ambas. Proporcionamos tres ejemplos recientes de restauración que combinan los razonamientos tecnocrático, idealista y pragmático y demuestran el potencial para un enfoque más unificado. Los razonamientos biótico y heurístico pueden ser satisfechos en el contexto de los otros razonamientos. [source]

History and Management of Crown-Fire Ecosystems: a Summary and Response

CONSERVATION BIOLOGY, Issue 6 2001
Jon E. Keeley
First page of article [source]

Prescribing Flood Regimes to Sustain Riparian Ecosystems along Meandering Rivers

CONSERVATION BIOLOGY, Issue 5 2000
Brian D. Richter
By managing river flows for water supplies and power generation, water management agencies have inadvertently caused considerable degradation of riverine ecosystems and associated biodiversity. New approaches for meeting human needs for water while conserving the ecological integrity of riverine ecosystems are greatly needed. We describe an approach for identifying the natural flooding characteristics that must be protected or restored to maintain riparian ( floodplain) ecosystems along meandering rivers. We developed a computer model to simulate flood-driven changes in the relative abundance of riparian patch types along the Yampa River in Colorado ( U.S.A.). The model is based on research suggesting that the duration of flooding at or above 209 m3 per second (125% of bankfull discharge) is particularly important in driving lateral channel migration, which is responsible for initiating ecological succession in the Yampa's riparian forest. Other hydrologic variables, such as the magnitude of annual peak flows, were not as strongly correlated with lateral channel migration rates. Model simulations enabled us to tentatively identify a threshold of alteration of flood duration that could lead to substantial changes in the abundance of forest patch types over time should river flows be regulated by future water projects. Based on this analysis, we suggest an ecologically compatible water management approach that avoids crossing flood alteration thresholds and provides opportunity to use a portion of flood waters for human purposes. Recommended improvements to the Yampa model include obtaining additional low-elevation aerial photographs of the river corridor to enable better estimation of channel migration rates and vegetation changes. These additional data should greatly improve the model's accuracy and predictive capabilities and therefore its management value. Resumen: La composición y estructura de ecosistemas ribereños están fuertemente ligadas a la variabilidad hidrológica natural. Al manejar el flujo de ríos para abastecer agua y generar energía, las agencias de manejo de agua han causado inadvertidamente una degradación considerable de los ecosistemas ribereños y la biodiversidad asociada a ellos. Se necesitan nuevas estrategias para satisfacer las necesidades humanas de agua al mismo tiempo que se conserva la integridad de los ecosistemas ribereños. Describimos una estrategia para identificar las características de inundaciones naturales que deben ser protegidas o restauradas para mantener ecosistemas riparios ( planicies de inundación) a lo largo de ríos sinuosos. Desarrollamos un modelo de computadora para simular los cambios causados por inundaciones en la abundancia relativa de tipos de parche ripario a lo largo del río Yampa, en Colorado ( Estados Unidos de Norteamérica). Este modelo se basa en investigación que sugiere que la duración de la inundación a, o mayor a, 209 m3 por segundo (125% de descarga del banco lleno a su capacidad) es particularmente importante en la conducción de la migración de canales laterales, lo cual es responsable de la iniciación de la sucesión ecológica en el bosque ripario del río Yampa. Otras variables hidrológicas, como lo es la magnitud del pico de los flujos anuales no estuvieron tan fuertemente correlacionadas con las tasas de migración lateral de canales. Las simulaciones del modelo nos permitieron identificar límites tentativos de alteración de la duración de la inundación que podrían conducir a cambios sustanciales en la abundancia de tipos de parches forestales en el tiempo si los flujos de los ríos son regulados en proyectos de agua futuros. En base a este análisis, sugerimos una estrategia de manejo de agua ecológicamente compatible que evita sobrepasar los límites de alteración de las inundaciones y provee la oportunidad de usar una porción del agua de las inundaciones para fines humanos. Las recomendaciones de mejoras al modelo del río Yampa incluyen la necesidad de obtener fotografías aéreas de baja elevación adicionales del corredor del río, que permitan una mejor estimación de las tasas de migración de los canales y los cambios en la vegetación. Estos datos adicionales deberán mejorar en gran medida la precisión del modelo y sus capacidades predictivas y, por lo tanto, su valor de manejo. [source]

Editorial: joint meeting of the 5th International Conference on Aeolian Research and the Global Change and Terrestrial Ecosystems,Soil Erosion Network,

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 11 2003
Ted M. Zobeck
No abstract is available for this article. [source]

Accounting for uncertainty in marine reserve design

ECOLOGY LETTERS, Issue 1 2006
Benjamin S. Halpern
Abstract Ecosystems and the species and communities within them are highly complex systems that defy predictions with any degree of certainty. Managing and conserving these systems in the face of uncertainty remains a daunting challenge, particularly with respect to developing networks of marine reserves. Here we review several modelling frameworks that explicitly acknowledge and incorporate uncertainty, and then use these methods to evaluate reserve spacing rules given increasing levels of uncertainty about larval dispersal distances. Our approach finds similar spacing rules as have been proposed elsewhere , roughly 20,200 km , but highlights several advantages provided by uncertainty modelling over more traditional approaches to developing these estimates. In particular, we argue that uncertainty modelling can allow for (1) an evaluation of the risk associated with any decision based on the assumed uncertainty; (2) a method for quantifying the costs and benefits of reducing uncertainty; and (3) a useful tool for communicating to stakeholders the challenges in managing highly uncertain systems. We also argue that incorporating rather than avoiding uncertainty will increase the chances of successfully achieving conservation and management goals. [source]

Net regional ecosystem CO2 exchange from airborne and ground-based eddy covariance, land-use maps and weather observations

GLOBAL CHANGE BIOLOGY, Issue 3 2007
F. MIGLIETTA
Abstract Measurements of regional net ecosystem exchange (NEE) were made over a period of 21 days in summer 2002 in the South-Central part of the Netherlands and extrapolated to an area of 13 000 km2 using a combination of flux measurements made by a Sky Arrow ERA research aircraft, half-hourly eddy covariance data from four towers, half-hourly weather data recorded by three weather stations and detailed information on regional land use. The combination of this type of information allowed to estimate the net contribution of the terrestrial ecosystems to the overall regional carbon flux and to map dynamically the temporal and spatial variability of the fluxes. A regional carbon budget was calculated for the study period and the contributions of the different land uses to the overall regional flux, were assessed. Ecosystems were, overall, a small source of carbon to the atmosphere equivalent to to 0.23±0.025 g C m,2 day,1. When considered separately, arable and grasslands were a source of, respectively, 0.68±0.022 and 1.28±0.026 g C m,2 day,1. Evergreen and deciduous forests were instead a sink of ,1.42±0.015 g C m,2 day,1. During the study period, forests offset approximately 3.5% of anthropogenic carbon emission estimates obtained from inventory data. Lacking of a robust validation, NEE values obtained with this method were compared with independent state of art estimates of the regional carbon balance that were obtained by applying a semi-empirical model of NEE driven by MODIS satellite fAPAR data. The comparison showed an acceptable matching for the carbon balance of forest that was a sink in both cases, while a much larger difference for arable and grassland was found. Those ecosystems were a sink for satellite-based estimates while they were a source for the combined aircraft and tower estimates. Possible causes of such differences are discussed and partly addressed. The importance of new methods for determining carbon balance at the regional scale, is outlined. [source]

Conundrums in mixed woody,herbaceous plant systems

JOURNAL OF BIOGEOGRAPHY, Issue 11 2003
Joanna I. House
Abstract Aims To identify approaches to improve our understanding of, and predictive capability for, mixed tree,grass systems. Elucidation of the interactions, dynamics and determinants, and identification of robust generalizations that can be broadly applied to tree,grass systems would benefit ecological theory, modelling and land management. Methods A series of workshops brought together scientific expertise to review theory, data availability, modelling approaches and key questions. Location Ecosystems characterized by mixtures of herbaceous and woody plant life-forms, often termed ,savannas', range from open grasslands with few woody plants, to woodlands or forests with a grass layer. These ecosystems represent a substantial portion of the terrestrial biosphere, an important wildlife habitat, and a major resource for provision of livestock, fuel wood and other products. Results Although many concepts and principles developed for grassland and forest systems are relevant to these dual life-form communities, the novel, complex, nonlinear behaviour of mixed tree,grass systems cannot be accounted for by simply studying or modelling woody and herbaceous components independently. A more robust understanding requires addressing three fundamental conundrums: (1) The ,treeness' conundrum. What controls the relative abundance of woody and herbaceous plants for a given set of conditions at given site? (2) The coexistence conundrum. How do the life-forms interact with each other? Is a given woody,herbaceous ratio dynamically stable and persistent under a particular set of conditions? (3) The net primary productivity (NPP) conundrum. How does NPP of the woody vegetation, the herbaceous vegetation, and the total ecosystem (woody + herbaceous) change with changes in the tree,grass ratio? Tests of the theory and conceptual models of determinants of mixed woody,herbaceous systems have been largely site- or region-specific and have seldom been broadly or quantitatively evaluated. Cross-site syntheses based on data and modelling are required to address the conundrums and identify emerging patterns, yet, there are very few data sets for which either biomass or NPP have been quantified for both the woody and the herbaceous components of tree,grass systems. Furthermore, there are few cross-site comparisons spanning the diverse array of woody,herbaceous mixtures. Hence, initial synthesis studies should focus on compiling and standardizing a global data base which could be (1) explored to ascertain if robust generalizations and consistent patterns exist; and (2) used to evaluate the performance of savanna simulation models over a range of woody,herbaceous mixtures. Savanna structure and productivity are the result of complex and dynamic interactions between climate, soils and disturbances, notably fire and herbivory. Such factors are difficult to isolate or experimentally manipulate in order to evaluate their impacts at spatial and temporal scales appropriate for assessing ecosystem dynamics. These factors can, however, be evaluated with simulation models. Existing savanna models vary markedly with respect to their conceptual approach, their data requirements and the extent to which they incorporate mechanistic processes. Model intercomparisons can elucidate those approaches most suitable for various research questions and management applications. Conclusion Theoretical and conceptual advances could be achieved by considering a broad continuum of grass,shrub,tree combinations using data meta-analysis techniques and modelling. [source]