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Terrestrial Ecosystems (terrestrial + ecosystem)
Selected AbstractsEditorial: 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 2003Ted M. Zobeck No abstract is available for this article. [source] Ultraviolet Radiation and Terrestrial Ecosystems,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2005Donald T. Krizek First page of article [source] Ultraviolet Radiation and Terrestrial Ecosystems,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2004Donald T. Krizek No abstract is available for this article. [source] The Role of Amoeboid Protists and the Microbial Community in Moss-Rich Terrestrial Ecosystems: Biogeochemical Implications for the Carbon Budget and Carbon Cycle, Especially at Higher Latitudes,THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 3 2008O. ROGER ANDERSON ABSTRACT. Moss-rich terrestrial communities are widely distributed in low- and high-latitude environments, covering vast surface areas in the boreal forests and tundra. The microbial biota in these organic-rich communities may contribute substantially to the carbon budget of terrestrial communities and the carbon cycle on a global scale. Recent research is reported on the carbon content of microbial communities in some temperate and high-latitude moss communities. The total carbon content and potential respiratory carbon dioxide (CO2) efflux is reported for bacteria, microflagellates, naked amoebae, and testate amoebae within sampling sites at a northeastern forest and the tundra at Toolik, Alaska. Quantitative models of the predicted total CO2 efflux from the microbes, based on microscopic observations and enumeration of the microbiota in samples from the research sites, are described and predictions are compared with published field-based data of CO2 efflux. The significance of the predictions for climate change and global warming are discussed. [source] Vegetation, environment, and time: The origination and termination of ecosystemsJOURNAL OF VEGETATION SCIENCE, Issue 5 2006Stephen T. Jackson Abstract Terrestrial ecosystems originate when particular plant species attain dominance at specific locations under specific environmental regimes. Ecosystems terminate, gradually or abruptly, when the dominant species or functional types are replaced by others, usually owing to environmental change or severe and irreversible disturbance. Assessing whether current ecosystems are sustainable in the face of future environmental change can be aided by examining the range of environmental variation those ecosystems have experienced in the past, and by determining the environmental conditions under which those ecosystems arose. The range of environmental variation depends on the time scale at which it is assessed. A narrow time span (e.g. 200,300 years) may underestimate the range of variation within which an ecosystem is sustainable, and it may also underestimate the risk of major transformation or disruption of that ecosystem by environmental change. Longer time spans (e.g. 1000,2000 years) increase the range of variation, by encompassing a larger sample of natural variability as well as non-stationary variability in the earth system. Most modern ecosystems disappear when the time span is expanded to 10000,15 000 years owing to secular changes in earth's climate system. Paleo-ecological records can pinpoint the time of origination of specific ecosystems, and paleo-environmental records can reveal the specific environmental changes that led to development of those ecosystems and the range of environmental variation under which those ecosystems have maintained themselves in the past. This information can help identify critical environmental thresholds beyond which specific modern ecosystems can no longer be sustained. [source] EVOLUTION OF INSECT METAMORPHOSIS: A MICROARRAY-BASED STUDY OF LARVAL AND ADULT GENE EXPRESSION IN THE ANT CAMPONOTUS FESTINATUSEVOLUTION, Issue 4 2005Michael A. D. Goodisman Abstract Holometabolous insects inhabit almost every terrestrial ecosystem. The evolutionary success of holometabolous insects stems partly from their developmental program, which includes discrete larval and adult stages. To gain an understanding of how development differs among holometabolous insect taxa, we used cDNA microarray technology to examine differences in gene expression between larval and adult Camponotus festinatus ants. We then compared expression patterns obtained from our study to those observed in the fruitfly Drosophila melanogaster. We found that many genes showed distinct patterns of expression between the larval and adult ant life stages, a result that was confirmed through quantitative reverse-transcriptase polymerase chain reaction. Genes involved in protein metabolism and possessing structural activity tended to be more highly expressed in larval than adult ants. In contrast, genes relatively upregulated in adults possessed a greater diversity of functions and activities. We also discovered that patterns of expression observed for homologous genes in D. melanogaster differed substantially from those observed in C. festinatus. Our results suggest that the specific molecular mechanisms involved in metamorphosis will differ substantially between insect taxa. Systematic investigation of gene expression during development of other taxa will provide additional information on how developmental pathways evolve. [source] Reassessing the impact of North Atlantic Oscillation on the sub-Saharan vegetation productivityGLOBAL CHANGE BIOLOGY, Issue 4 2003GUILING WANG Abstract The Northern Atlantic Oscillation (NAO) has been shown to have a significant impact on the terrestrial ecosystem in the Sahelian region of Africa during the 1980s, and it has been strongly suggested that NAO may be a reliable predictor for the response of the Sahelian ecosystem to global climate variability. Using data from an extended period, we provide a reassessment for the impact of NAO on the Sahelian climate and ecosystem, and show that there is no consistent relationship between NAO and the ecosystem over Sahel. Statistical analysis on the NAO, vegetation, and precipitation data indicates that NAO influences the Sahelian vegetation productivity exclusively through its impact on precipitation. However, the relationship between the NAO index and Sahelian precipitation varies substantially with time. The correlation coefficient fluctuates between positive and negative values, and does not pass the 5% significance test during most of the twentieth century. The NAO system, although documented to govern the ecosystem dynamics over many other regions, does not have a consistent impact on the ecosystem over the Sahel. Therefore, the NAO index cannot produce a useful prediction on the ecosystem variability and changes in this region. This study provides an example that correlations based on short climate and ecological records (less than 20 years in this case) can be spurious and potentially misleading. [source] Global pattern of NPP to GPP ratio derived from MODIS data: effects of ecosystem type, geographical location and climateGLOBAL ECOLOGY, Issue 3 2009Yangjian Zhang ABSTRACT Aim, To examine the global pattern of the net primary production (NPP)/gross primary production (GPP) ratio of the Earth's land area along geographical and climatic gradients. Location, The global planetary ecosystem. Methods, The 4-year average annual NPP/GPP ratio of the Earth's land area was calculated using 2000,03 Moderate Resolution Imaging Spectroradiometer (MODIS) data. The global pattern of the NPP/GPP ratio was investigated by comparing it among each typical terrestrial ecosystem and plotting it along a geographical and climatic gradient, including latitude, altitude, temperature and precipitation. Results, The global terrestrial ecosystem had an average NPP/GPP ratio value of 0.52 with minor variation from 2000 to 2003. However, the NPP/GPP ratio showed considerable spatial variation associated with ecosystem type, geographical location and climate. Densely vegetated ecosystems had a lower NPP/GPP ratio than sparsely vegetated ecosystems. Forest ecosystems had a lower NPP/GPP ratio than shrub and herbaceous ecosystems. Geographically, the NPP/GPP ratio increased with altitude. In the Southern Hemisphere, the NPP/GPP ratio decreased along latitude from 30° to 10° and it exhibited high fluctuation in the Northern Hemisphere. Climatically, the NPP/GPP ratio exhibited a decreasing trend along enhanced precipitation when it was less than 2300 mm year,1 and a static trend when the annual precipitation was over 2300 mm. The NPP/GPP ratio showed a decreasing trend along temperature when it was between ,20 °C and 10 °C, and showed an increasing trend along rising temperature when it was between ,10 °C and 20 °C. Within each ecosystem, the NPP/GPP ratio revealed a similar trend to the global trend along temperature and precipitation. Conclusions, The NPP/GPP ratio exhibited a pattern depending on the main climatic characteristics such as temperature and precipitation and geographical factors such as latitude and altitude. The findings of this research challenge the widely held assumption that the NPP/GPP ratio is consistent regardless of ecosystem type. [source] The grassland farming system and sustainable agricultural development in ChinaGRASSLAND SCIENCE, Issue 1 2005Zhibiao Nan Abstract Grassland is the largest terrestrial ecosystem in China, at about 39 280 × 104 ha and covers 41% of the total land area. Grasslands not only provide forage to feed livestock, but also play a critical role in alleviating many of the most challenging environmental and ecological problems that humankind is facing. About 90% of the total usable grassland in China has been degraded to various extents and this is the number one problem facing agricultural production, rural development and environmental improvement. Research on grassland degradation has been carried out since the early 1950s. Enormous achievements have been made and theory and a technical system for pastoral agriculture have been developed. This pastoral agriculture system is a well-organized modern farming system including four production levels, that is, preplant, plant, animal and postbiotic levels, and is linked by three interfaces, including vegetation-site, grassland-animal and production-management. The system capacity and productivity could be improved by system coupling. Since it emerged, this pastoral agriculture system has been established in various ecological regions in China and significant improvements in agricultural sustainability, farmer's income and environmental stability have been obtained. In the future, it will play a more critical role in developing sustainable agriculture in China. [source] Documenting Loss of Large Trophy Fish from the Florida Keys with Historical PhotographsCONSERVATION BIOLOGY, Issue 3 2009LOREN McCLENACHAN arrecifes de coral; ecología histórica; directrices cambiantes; peces de arrecife; sobrepesca Abstract:,A loss of large vertebrates has occurred in aquatic and terrestrial ecosystems, but data to measure long-term population changes are sparse. Historical photographs provide visual and quantitative evidence of changes in mean individual size and species composition for groups of marine fish that have been targeted by sport fishing. I measured such trends for 13 groups of recreationally caught "trophy" reef fish with photographs taken in Key West, Florida, from 1956 to 2007. The mean fish size declined from an estimated 19.9 kg (SE 1.5) to 2.3 kg (SE 0.3), and there was a major shift in species composition. Landings from 1956 to 1960 were dominated by large groupers (Epinephelus spp.), and other large predatory fish were commonly caught, including sharks with an average length of just <2 m. In contrast, landings in 2007 were composed of small snappers (Lutjanus spp. and Ocyurus chrysurus) with an average length of 34.4 cm (SE 0.62), and the average length of sharks declined by more than 50% over 50 years. Major declines in the size of fish caught were not reflected in the price of fishing trips, so customers paid the same amount for a less-valuable product. Historical photographs provide a window into a more pristine coral reef ecosystem that existed a half a century ago and lend support to current observations that unfished reef communities are able to support large numbers of large-bodied fish. Resumen:,Una pérdida de vertebrados mayores ha ocurrido en ecosistemas acuáticos y terrestres, pero los datos para medir los cambios poblaciones a largo plazo son escasos. Las fotografías históricas proporcionan evidencia visual y cuantitativa de cambios en el tamaño individual promedio y de la composición de especies en grupos de peces marinos que han sido blanco de la pesca deportiva. Medí esas tendencias en 13 grupos de peces de arrecife capturados recreativamente como "trofeos" mediante fotografías tomadas en Key West, Florida, desde 1956 a 2007. El peso promedio de los peces declinó de unos 19.9 kg (ES 1.5) a 2.3 kg (ES 0.3), y hubo un cambio mayor en la composición de especies. Las capturas entre 1956 y 1960 estuvieron dominadas por meros (Epinephelus spp.) grandes, y otros peces depredadores eran capturados comúnmente, incluyendo tiburones con una longitud promedio de poco menos de 2m. En contraste, las capturas en 2007 fueron compuestas de pargos (Lutjanus spp. y Ocyurus chrysurus) pequeños con una longitud promedio de 34.4 cm (ES 0.62), y la longitud promedio de los tiburones declinó más de 50% en 50 años. La gran declinación en el tamaño de los peces capturados no se reflejó en los precios de los viajes de pesca, así que los clientes pagaron la misma cantidad por un producto menos valioso. Las fotografías históricas proporcionan una visión de un ecosistema arrecifal coralino prístino que existió hace medio siglo y proporcionan soporte a los comentarios actuales de que las comunidades arrecifales no explotadas son capaces de soportar numerosos peces de talla grande. [source] Carnivore-Livestock Conflicts: Effects of Subsidized Predator Control and Economic Correlates on the Sheep IndustryCONSERVATION BIOLOGY, Issue 3 2006KIM MURRAY BERGER Canis latrans; coyotes; depredación; evaluación de política Abstract:,Despite the importance of carnivores in terrestrial ecosystems, many nations have implemented well-coordinated, state-funded initiatives to remove predators, largely because of conflicts with humans over livestock. Although these control efforts have been successful in terms of the number of carnivores removed, their effects on the viability of the industries they seek to protect are less understood. I assessed the efficacy of long-term efforts by the U.S. government to improve the viability of the sheep industry by reducing predation losses. I used regression analysis and hierarchical partitioning of a 60-year data set to explore associations among changes in sheep numbers and factors such as predator control effort, market prices, and production costs. In addition, I compared trends in the sheep industry in the western United States, where predator control is subsidized and coyotes (Canis latrans) are abundant, with trends in eastern states that lack federally subsidized predator control and that were (1) colonized by coyotes before 1950 or (2) colonized by coyotes between 1950 and 1990. Although control efforts were positively correlated with fluctuations in sheep numbers, production costs and market prices explained most of the model variation, with a combined independent contribution of 77%. Trends in sheep numbers in eastern and western states were highly correlated (r ,0.942) independent of the period during which they were colonized by coyotes, indicating either that control has been ineffective at reducing predation losses or that factors other than predation account for the declines in both regions. These results suggest that government-subsidized predator control has failed to prevent the decline in the sheep industry and alternative support mechanisms need to be developed if the goal is to increase sheep production and not simply to kill carnivores. Resumen:,A pesar de la importancia de carnívoros en los ecosistemas terrestres, muchos países han implementado iniciativas bien coordinadas, financiadas por el gobierno, para remover depredadores, principalmente debido a conflictos entre humanos y ganado. Aunque estos esfuerzos de control han sido exitosos en términos del número de carnívoros removidos, sus efectos sobre la viabilidad de las industrias que se busca proteger son poco comprendidos. Evalué la eficacia de los esfuerzos a largo plazo del gobierno de E.U.A. para mejorar la viabilidad de la industria ovina mediante la reducción de pérdidas por depredación. Utilicé análisis de regresión y partición jerárquica de un conjunto de datos de 60 años para explorar asociaciones entre cambios en el número de ovejas y factores como el esfuerzo de control de depredadores, precios de mercado y costos de producción. Adicionalmente comparé las tendencias en la industria ovina en el oeste de Estados Unidos, donde el control de depredadores está subsidiado y los coyotes (Canis latrans) son abundantes, con las tendencias en los estados orientales que carecen de control subsidiado federalmente y que fueron (1) colonizados por coyotes antes de 1950 o (2) colonizados por coyotes entre 1950 y 1990. Aunque los esfuerzos de control se correlacionaron positivamente con las fluctuaciones en el número de ovejas, los costos de producción y los precios de mercado explicaron la mayor parte de la variación del modelo, con una contribución independiente combinada de 77%. Las tendencias en el número de ovejas en los estados orientales y occidentales estaban muy correlacionadas (r , 0.942) independientemente del período en que fueron colonizados por coyotes, lo que indica que el control ha sido ineficiente en la reducción de depredación o que factores, distintos a la depredación, son responsables de las declinaciones en ambas regiones. Estos resultados sugieren que el control subsidiado por el gobierno ha fallado en prevenir la declinación de la industria ovina y que se necesitan desarrollar mecanismos de soporte alternativos si la meta es incrementar la producción de ovejas y no simplemente matar carnívoros. [source] The ecosystem approach in corporate environmental management , expert mental models and environmental drivers in the Finnish forest industryCORPORATE SOCIAL RESPONSIBILITY AND ENVIRONMENTAL MANAGEMENT, Issue 2 2009Petteri Vihervaara Abstract The ecosystem approach has been adopted as the framework of the Convention on Biological Diversity, and is recommended to be used widely in the integrated management of land, water and living resources, to promote conservation and sustainable use in an equitable way, also in corporations. The forest industry is a resource-intensive branch with various impacts on aquatic and terrestrial ecosystems. Our aims in this study were to examine (i) how the ecosystem approach is implemented in the Finnish forest industry; and (ii) to outline the mental models of environmental experts of corporations, and their conceptualization of some key terms of ecosystem thinking. We interviewed 12 experts about their opinions on the main future challenges, the risks, the mistakes of the past, the possibilities and the successes confronting the forest industry. The results were analyzed using the DPSIR (Driving forces-Pressures-State-Impacts-Responses) framework model. Finally, we give several recommendations as to how the ecosystem approach can be integrated into corporate environmental management. Copyright © 2009 John Wiley & Sons, Ltd and ERP Environment. [source] Community effects of praying mantids: a meta-analysis of the influences of species identity and experimental designECOLOGICAL ENTOMOLOGY, Issue 4 2002William F. Fagan Abstract ,1. Generalist arthropod predators are ubiquitous in terrestrial ecosystems but experimental studies have yielded little agreement as to their effects on prey assemblages. Drawing on results from a suite of experimental field studies, a meta-analysis was conducted of the impact of praying mantids (Mantodea: Mantidae) on arthropod assemblages in order to identify predictable and unpredictable effects of these extremely generalised predators. 2. Results across different experiments were synthesised using the log response ratio framework, with a focus on quantifying net mantid impacts on arthropod density across taxonomic orders and trophic levels of arthropods, paying special attention to the contribution of mantid species identity and experimental design variables, such as the use of cages, length of experiment, and manipulated mantid density. 3. Calculated on a per mantid-day basis, the net impacts of Tenodera sinensis on arthropod density were generally weaker but more predictable than the effects of Mantis religiosa. Mantids in general had weak negative effects on density for most taxa but exhibited strong negative and positive effects on some taxa. Tenodera sinensis tended to have negative effects on Homoptera, Diptera, and Hemiptera and herbivores as a group, however M. religiosa exhibited greater variation in response of different taxa that appeared to be affected more strongly by experimental design. The effects of Stagmomantis carolina tended to be negative or non-significant. 4. Experimental cages had little influence on either the sign or magnitude of net community impacts for T. sinensis, however cage experiments reversed the sign of the mean effect for two of six taxonomic orders when the experimental predator was M. religiosa. Cages also increased the variability of effect size greatly for M. religiosa but not for T. sinensis. 5. It was concluded that it is possible to use log response ratios to determine general, predictable trends in a well-studied system. Similar meta-analyses of generalist predator effects in other systems should produce predictions of how these predators influence food webs, an important step towards defining more clearly the influences of generalist predators on community structure and dynamics. [source] Testing for criticality in ecosystem dynamics: the case of Amazonian rainforest and savanna fireECOLOGY LETTERS, Issue 7 2010Salvador Pueyo Ecology Letters (2010) 13: 793,802 Abstract We test for two critical phenomena in Amazonian ecosystems: self-organized criticality (SOC) and critical transitions. SOC is often presented in the complex systems literature as a general explanation for scale invariance in nature. In particular, this mechanism is claimed to underlie the macroscopic structure and dynamics of terrestrial ecosystems. These would be inextricably linked to the action of fire, which is conceived as an endogenous ecological process. We show that Amazonian savanna fires display the scale-invariant features characteristic of SOC but do not display SOC. The same is true in Amazonian rainforests subject to moderate drought. These findings prove that there are other causes of scale invariance in ecosystems. In contrast, we do find evidence of a critical transition to a megafire regime under extreme drought in rainforests; this phenomenon is likely to determine the time scale of a possible loss of Amazonian rainforest caused by climate change. [source] Atmospheric CO2 enrichment facilitates cation release from soilECOLOGY LETTERS, Issue 3 2010L. Cheng Ecology Letters (2010) 13: 284,291 Abstract Atmospheric CO2 enrichment generally stimulates plant photosynthesis and nutrient uptake, modifying the local and global cycling of bioactive elements. Although nutrient cations affect the long-term productivity and carbon balance of terrestrial ecosystems, little is known about the effect of CO2 enrichment on cation availability in soil. In this study, we present evidence for a novel mechanism of CO2 -enhancement of cation release from soil in rice agricultural systems. Elevated CO2 increased organic C allocation belowground and net H+ excretion from roots, and stimulated root and microbial respiration, reducing soil redox potential and increasing Fe2+ and Mn2+ in soil solutions. Increased H+, Fe2+, and Mn2+ promoted Ca2+ and Mg2+ release from soil cation exchange sites. These results indicate that over the short term, elevated CO2 may stimulate cation release from soil and enhance plant growth. Over the long-term, however, CO2 -induced cation release may facilitate cation losses and soil acidification, negatively feeding back to the productivity of terrestrial ecosystems. [source] A review of nitrogen enrichment effects on three biogenic GHGs: the CO2 sink may be largely offset by stimulated N2O and CH4 emissionECOLOGY LETTERS, Issue 10 2009Lingli Liu Abstract Anthropogenic nitrogen (N) enrichment of ecosystems, mainly from fuel combustion and fertilizer application, alters biogeochemical cycling of ecosystems in a way that leads to altered flux of biogenic greenhouse gases (GHGs). Our meta-analysis of 313 observations across 109 studies evaluated the effect of N addition on the flux of three major GHGs: CO2, CH4 and N2O. The objective was to quantitatively synthesize data from agricultural and non-agricultural terrestrial ecosystems across the globe and examine whether factors, such as ecosystem type, N addition level and chemical form of N addition influence the direction and magnitude of GHG fluxes. Results indicate that N addition increased ecosystem carbon content of forests by 6%, marginally increased soil organic carbon of agricultural systems by 2%, but had no significant effect on net ecosystem CO2 exchange for non-forest natural ecosystems. Across all ecosystems, N addition increased CH4 emission by 97%, reduced CH4 uptake by 38% and increased N2O emission by 216%. The net effect of N on the global GHG budget is calculated and this topic is reviewed. Most often N addition is considered to increase forest C sequestration without consideration of N stimulation of GHG production in other ecosystems. However, our study indicated that although N addition increased the global terrestrial C sink, the CO2 reduction could be largely offset (53,76%) by N stimulation of global CH4 and N2O emission from multiple ecosystems. [source] Mass invariance of population nitrogen flux by terrestrial mammalian herbivores: an extension of the energetic equivalence ruleECOLOGY LETTERS, Issue 9 2008Christopher W. Habeck Abstract According to the energetic equivalence rule, energy use by a population is independent of average adult body mass. Energy use can be equated with carbon flux, and it has been suggested that population fluxes of other materials, such as nitrogen and phosphorus, might also be independent of body mass. We compiled data on individual nitrogen deposition rates (via faeces and urine) and average population densities of 26 species of mammalian herbivores to test the hypothesis of elemental equivalence for nitrogen. We found that the mass scaling of individual nitrogen flux was opposite to that of population density for the species in our dataset. By computing the product of individual nitrogen flux and average population density for each species in our dataset, we found that population-level nitrogen flux was independent of species mass, averaging c. 3.22 g N ha,1 day,1. Results from this analysis can be used to understand the influence of mammalian herbivore communities on nitrogen cycling in terrestrial ecosystems. [source] A cross-system synthesis of consumer and nutrient resource control on producer biomassECOLOGY LETTERS, Issue 7 2008Daniel S. Gruner Abstract Nutrient availability and herbivory control the biomass of primary producer communities to varying degrees across ecosystems. Ecological theory, individual experiments in many different systems, and system-specific quantitative reviews have suggested that (i) bottom,up control is pervasive but top,down control is more influential in aquatic habitats relative to terrestrial systems and (ii) bottom,up and top,down forces are interdependent, with statistical interactions that synergize or dampen relative influences on producer biomass. We used simple dynamic models to review ecological mechanisms that generate independent vs. interactive responses of community-level biomass. We calibrated these mechanistic predictions with the metrics of factorial meta-analysis and tested their prevalence across freshwater, marine and terrestrial ecosystems with a comprehensive meta-analysis of 191 factorial manipulations of herbivores and nutrients. Our analysis showed that producer community biomass increased with fertilization across all systems, although increases were greatest in freshwater habitats. Herbivore removal generally increased producer biomass in both freshwater and marine systems, but effects were inconsistent on land. With the exception of marine temperate rocky reef systems that showed positive synergism of nutrient enrichment and herbivore removal, experimental studies showed limited support for statistical interactions between nutrient and herbivory treatments on producer biomass. Top,down control of herbivores, compensatory behaviour of multiple herbivore guilds, spatial and temporal heterogeneity of interactions, and herbivore-mediated nutrient recycling may lower the probability of consistent interactive effects on producer biomass. Continuing studies should expand the temporal and spatial scales of experiments, particularly in understudied terrestrial systems; broaden factorial designs to manipulate independently multiple producer resources (e.g. nitrogen, phosphorus, light), multiple herbivore taxa or guilds (e.g. vertebrates and invertebrates) and multiple trophic levels; and , in addition to measuring producer biomass , assess the responses of species diversity, community composition and nutrient status. [source] The unseen majority: soil microbes as drivers of plant diversity and productivity in terrestrial ecosystemsECOLOGY LETTERS, Issue 3 2008Marcel G. A. Van Der Heijden Abstract Microbes are the unseen majority in soil and comprise a large portion of life's genetic diversity. Despite their abundance, the impact of soil microbes on ecosystem processes is still poorly understood. Here we explore the various roles that soil microbes play in terrestrial ecosystems with special emphasis on their contribution to plant productivity and diversity. Soil microbes are important regulators of plant productivity, especially in nutrient poor ecosystems where plant symbionts are responsible for the acquisition of limiting nutrients. Mycorrhizal fungi and nitrogen-fixing bacteria are responsible for c. 5,20% (grassland and savannah) to 80% (temperate and boreal forests) of all nitrogen, and up to 75% of phosphorus, that is acquired by plants annually. Free-living microbes also strongly regulate plant productivity, through the mineralization of, and competition for, nutrients that sustain plant productivity. Soil microbes, including microbial pathogens, are also important regulators of plant community dynamics and plant diversity, determining plant abundance and, in some cases, facilitating invasion by exotic plants. Conservative estimates suggest that c. 20 000 plant species are completely dependent on microbial symbionts for growth and survival pointing to the importance of soil microbes as regulators of plant species richness on Earth. Overall, this review shows that soil microbes must be considered as important drivers of plant diversity and productivity in terrestrial ecosystems. [source] Metabolic responses of novel cellulolytic and saccharolytic agricultural soil Bacteria to oxygenENVIRONMENTAL MICROBIOLOGY, Issue 4 2010Stefanie Schellenberger Summary Cellulose is the most abundant biopolymer in terrestrial ecosystems and is degraded by microbial communities in soils. However, relatively little is known about the diversity and function of soil prokaryotes that might participate in the overall degradation of this biopolymer. The active cellulolytic and saccharolytic Bacteria in an agricultural soil were evaluated by 16S rRNA 13C-based stable isotope probing. Cellulose, cellobiose and glucose were mineralized under oxic conditions in soil slurries to carbon dioxide. Under anoxic conditions, these substrates were converted primarily to acetate, butyrate, carbon dioxide, hydrogen and traces of propionate and iso-butyrate; the production of these fermentation end-products was concomitant with the apparent reduction of iron(III). [13C]-cellulose was mainly degraded under oxic conditions by novel family-level taxa of the Bacteroidetes and Chloroflexi, and a known family-level taxon of Planctomycetes, whereas degradation under anoxic conditions was facilitated by the Kineosporiaceae (Actinobacteria) and cluster III Clostridiaceae and novel clusters within Bacteroidetes. Active aerobic sub-communities in oxic [13C]-cellobiose and [13C]-glucose treatments were dominated by Intrasporangiaceae and Micrococcaceae (Actinobacteria) whereas active cluster I Clostridiaceae (Firmicutes) were prevalent in anoxic treatments. A very large number (i.e. 28) of the detected taxa did not closely affiliate with known families, and active Archaea were not detected in any of the treatments. These collective findings suggest that: (i) a large uncultured diversity of soil Bacteria was involved in the utilization of cellulose and products of its hydrolysis, (ii) the active saccharolytic community differed phylogenetically from the active cellulolytic community, (iii) oxygen availability impacted differentially on the activity of taxa and (iv) different redox guilds (e.g. fermenters and iron reducers) compete or interact during cellulose degradation in aerated soils. [source] Relative abundance and diversity of ammonia-oxidizing archaea and bacteria in the San Francisco Bay estuaryENVIRONMENTAL MICROBIOLOGY, Issue 11 2008Annika C. Mosier Summary Ammonia oxidation in marine and estuarine sediments plays a pivotal role in the cycling and removal of nitrogen. Recent reports have shown that the newly discovered ammonia-oxidizing archaea can be both abundant and diverse in aquatic and terrestrial ecosystems. In this study, we examined the abundance and diversity of ammonia-oxidizing archaea (AOA) and betaproteobacteria (,-AOB) across physicochemical gradients in San Francisco Bay , the largest estuary on the west coast of the USA. In contrast to reports that AOA are far more abundant than ,-AOB in both terrestrial and marine systems, our quantitative PCR estimates indicated that ,-AOB amoA (encoding ammonia monooxygenase subunit A) copy numbers were greater than AOA amoA in most of the estuary. Ammonia-oxidizing archaea were only more pervasive than ,-AOB in the low-salinity region of the estuary. Both AOA and ,-AOB communities exhibited distinct spatial structure within the estuary. AOA amoA sequences from the north part of the estuary formed a large and distinct low-salinity phylogenetic group. The majority of the ,-AOB sequences were closely related to other marine/estuarine Nitrosomonas -like and Nitrosospira -like sequences. Both ammonia-oxidizer community composition and abundance were strongly correlated with salinity. Ammonia-oxidizing enrichment cultures contained AOA and ,-AOB amoA sequences with high similarity to environmental sequences. Overall, this study significantly enhances our understanding of estuarine ammonia-oxidizing microbial communities and highlights the environmental conditions and niches under which different AOA and ,-AOB phylotypes may thrive. [source] Quantitative analyses of the abundance and composition of ammonia-oxidizing bacteria and ammonia-oxidizing archaea of a Chinese upland red soil under long-term fertilization practicesENVIRONMENTAL MICROBIOLOGY, Issue 9 2007Ji-zheng He Summary The abundance and composition of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were investigated by using quantitative real-time polymerase chain reaction, cloning and sequencing approaches based on amoA genes. The soil, classified as agri-udic ferrosols with pH (H2O) ranging from 3.7 to 6.0, was sampled in summer and winter from long-term field experimental plots which had received 16 years continuous fertilization treatments, including fallow (CK0), control without fertilizers (CK) and those with combinations of fertilizer nitrogen (N), phosphorus (P) and potassium (K): N, NP, NK, PK, NPK and NPK plus organic manure (OM). Population sizes of AOB and AOA changed greatly in response to the different fertilization treatments. The NPK + OM treatment had the highest copy numbers of AOB and AOA amoA genes among the treatments that received mineral fertilizers, whereas the lowest copy numbers were recorded in the N treatment. Ammonia-oxidizing archaea were more abundant than AOB in all the corresponding treatments, with AOA to AOB ratios ranging from 1.02 to 12.36. Significant positive correlations were observed among the population sizes of AOB and AOA, soil pH and potential nitrification rates, indicating that both AOB and AOA played an important role in ammonia oxidation in the soil. Phylogenetic analyses of the amoA gene fragments showed that all AOB sequences from different treatments were affiliated with Nitrosospira or Nitrosospira- like species and grouped into cluster 3, and little difference in AOB community composition was recorded among different treatments. All AOA sequences fell within cluster S (soil origin) and cluster M (marine and sediment origin). Cluster M dominated exclusively in the N, NP, NK and PK treatments, indicating a pronounced difference in the community composition of AOA in response to the long-term fertilization treatments. These findings could be fundamental to improve our understanding of the importance of both AOB and AOA in the cycling of nitrogen and other nutrients in terrestrial ecosystems. [source] Spatial characterization of arbuscular mycorrhizal fungal molecular diversity at the submetre scale in a temperate grasslandFEMS MICROBIOLOGY ECOLOGY, Issue 2 2008Daniel L. Mummey Abstract Although arbuscular mycorrhizal fungi (AMF) form spatially complex communities in terrestrial ecosystems, the scales at which this diversity manifests itself is poorly understood. This information is critical to the understanding of the role of AMF in plant community composition. We examined small-scale (submetre) variability of AMF community composition (terminal restriction fragment length polymorphism fingerprinting) and abundance (extraradical hyphal lengths) in two 1 m2 plots situated in a native grassland ecosystem of western Montana. Extraradical AMF hyphal lengths varied greatly between samples (14,89 m g soil,1) and exhibited spatial structure at scales <30 cm. The composition of AMF communities was also found to exhibit significant spatial autocorrelation, with correlogram analyses suggesting patchiness at scales <50 cm. Supportive of overall AMF community composition analyses, individual AMF ribotypes corresponding to specific phylogenetic groups exhibited distinct spatial autocorrelation. Our results demonstrate that AMF diversity and abundance can be spatially structured at scales of <1 m. Such small-scale heterogeneity in the soil suggests that establishing seedlings may be exposed to very different, location dependent AMF communities. Our results also have direct implications for representative sampling of AMF communities in the field. [source] Trophic interactions in the methanogenic microbial community of low-temperature terrestrial ecosystemsFEMS MICROBIOLOGY ECOLOGY, Issue 1 2005O.R. Kotsyurbenko Abstract The formation of methane in various ecosystems is due to the functioning of an anaerobic community, which combines trophically different groups of microorganisms. The methanogenic microbial community is a complex biological system, which responds to low temperatures by changes in its trophic structure resulting in redistributing matter flows. The enhanced activity of homoacetogenic bacteria at low temperature plays a significant role in this redistribution. Due to their relatively high growth rates and metabolic versatility, homoacetogens can successfully compete with fermenting bacteria and hydrogenotrophic methanogenic archaea for common substrates. The concentration of hydrogen is an important regulatory factor in the psychroactive methanogenic community. At low temperature methanogenic archaea possessing a higher affinity for hydrogen than homoacetogens provide for interspecies H2 transport in syntrophic reactions of fatty acid decomposition. The formation of a balanced community at low temperature is a longtime process. Cold terrestrial ecosystems are dominated by psychroactive (psychrotolerant) microorganisms, which can grow over a wide range of ambient temperatures. [source] Ecology and microbial structures of archaeal/bacterial strings-of-pearls communities and archaeal relatives thriving in cold sulfidic springsFEMS MICROBIOLOGY ECOLOGY, Issue 1 2004Christian Rudolph Abstract Recently, a unique microbial community, growing in a whitish, macroscopically visible strings-of-pearls-like structure was discovered in the cold, sulfidic marsh water of the Sippenauer Moor near Regensburg, Bavaria, Germany. The pearls interior is predominated by microcolonies of the non-methanogenic SM1 euryarchaeon; the outer part of the pearls is mainly composed of Thiothrix. To screen sulfidic ecosystems for the distribution of such unique microbial communities, comparative microbial and geochemical analyses of cold, sulfidic springs of three geographically distinct locations in Bavaria, Germany, and Dalyan, Turkey, were performed. Here, we report on the discovery and study of another type of strings-of-pearls revealing a new microbial community structure. While the SM1 euryarchaeon is again the predominant archaeal constituent, the bacterial partner is the so-called IMB1 ,-proteobacterium. Due to the predominance of the IMB1 ,-proteobacterium, the strings-of-pearls reveal a fluffy and greyish macroscopical appearance. The phylogenetic survey revealed SM1 euryarchaeal relatives, designated as SM1 group, in all sites studied, indicating a widespread distribution of these archaea in terrestrial ecosystems. [source] Comparative single-strand conformation polymorphism (SSCP) and microscopy-based analysis of nitrogen cultivation interactive effects on the fungal community of a semiarid steppe soilFEMS MICROBIOLOGY ECOLOGY, Issue 2-3 2001Jennifer L. Lowell Abstract The effects of nitrogen accretion on fungal diversity and community structure in early-seral (cultivated) and native (uncultivated) shortgrass steppe soils were evaluated using single-strand conformation polymorphism (SSCP) and microscopy in a comparative experiment. Selected haplotypes generated from fungal 18S gene fragments were also sequenced for species identification. Microscopy-based analyses showed significantly shorter fungal hyphal lengths in the early-seral control plots in comparison with the native control plots (P<0.0003), independent of nitrogen addition. Although diversity indices did not show significant differences between the plots, SSCP analyses indicated that fungal community structure differed in the native and early-seral control sites. In nitrogen-amended sites, gene sequences from dominant haplotypes indicated a shift to a more common nitrogen-impacted fungal community. While nitrogen amendments appear to be more important than cultivation in influencing these soil fungal communities, hyphal lengths were only decreased due to cultivation. The use of microscopic and molecular techniques, as carried out in this study, provided integrative information concerning fungal community responses to wide spread stresses being imposed globally on terrestrial ecosystems, that is not provided by the individual techniques. [source] Genetic processes in arbuscular mycorrhizal fungiFEMS MICROBIOLOGY LETTERS, Issue 2 2005Teresa E. Pawlowska Abstract Arbuscular mycorrhizal (AM) fungi (Glomeromycota) colonize roots of the majority of land plants and facilitate their mineral nutrient uptake. Consequently, AM fungi play an important role in terrestrial ecosystems and are becoming a component of sustainable land management practices. The absence of sexual reproductive structures in modern Glomeromycota combined with their long evolutionary history suggest that these fungi may represent an ancient asexual lineage of great potential interest to evolutionary biology. However, many aspects of basic AM fungal biology, including genome structure, within-individual genetic variation, and reproductive mode are poorly understood. These knowledge gaps hinder research on the mechanisms of AM fungal interactions with individual plants and plant communities, and utilization of AM fungi in agricultural practices. I present here the current state of research on the reproduction in AM fungi and indicate what new findings can be expected in the future. [source] Nutrient dependent effects of consumer identity and diversity on freshwater ecosystem functionFRESHWATER BIOLOGY, Issue 1 2008ANDREW R. DZIALOWSKI Summary 1. Over the past decade, ecologists have tried to determine how changes in species composition and diversity affect ecosystem structure and function. Until recently, the majority of these studies have been conducted in terrestrial ecosystems and have not taken into account environmental variability. The purpose of this research was to determine how species identity and diversity in the freshwater zooplankton affected biomass of algae and zooplankton at two levels of nutrient enrichment. 2. Several species of cladocerans were grown alone and together in microcosms at both ambient and raised phosphorus concentrations to determine if the effects of consumer identity and diversity were nutrient dependent. 3. Total zooplankton biomass was greater, while algal biomass was lower, in mixed culture than in monoculture. The effects of zooplankton diversity on algal biomass, however, were only observed at raised phosphorus concentrations, suggesting that diversity effects were nutrient dependent. Specifically, diversity effects appeared to be related with biological mechanisms such as complementarity in resource use and/or facilitation. 4. More diverse communities of zooplankton appear to be better able to control algae than single species of zooplankton at high nutrient concentrations; therefore, zooplankton diversity may provide a buffer against eutrophication in freshwater ecosystems. [source] Riverine landscapes: taking landscape ecology into the waterFRESHWATER BIOLOGY, Issue 4 2002JOHN A. WIENS 1.,Landscape ecology deals with the influence of spatial pattern on ecological processes. It considers the ecological consequences of where things are located in space, where they are relative to other things, and how these relationships and their consequences are contingent on the characteristics of the surrounding landscape mosaic at multiple scales in time and space. Traditionally, landscape ecologists have focused their attention on terrestrial ecosystems, and rivers and streams have been considered either as elements of landscape mosaics or as units that are linked to the terrestrial landscape by flows across boundaries or ecotones. Less often, the heterogeneity that exists within a river or stream has been viewed as a `riverscape' in its own right. 2.,Landscape ecology can be unified about six central themes: (1) patches differ in quality (2) patch boundaries affect flows, (3) patch context matters, (4) connectivity is critical, (5) organisms are important, and (6) the importance of scale. Although riverine systems differ from terrestrial systems by virtue of the strong physical force of hydrology and the inherent connectivity provided by water flow, all of these themes apply equally to aquatic and terrestrial ecosystems, and to the linkages between the two. 3.,Landscape ecology therefore has important insights to offer to the study of riverine ecosystems, but these systems may also provide excellent opportunities for developing and testing landscape ecological theory. The principles and approaches of landscape ecology should be extended to include freshwater systems; it is time to take the `land' out of landscape ecology. [source] Drought changes phosphorus and potassium accumulation patterns in an evergreen Mediterranean forestFUNCTIONAL ECOLOGY, Issue 2 2007J. SARDANS Summary 1Climate models predict more extreme weather in Mediterranean ecosystems, with more frequent drought periods and torrential rainfall. These expected changes may affect major process in ecosystems such as mineral cycling. However, there is a lack of experimental data regarding the effects of prolonged drought on nutrient cycling and content in Mediterranean ecosystems. 2A 6-year drought manipulation experiment was conducted in a Quercus ilex Mediterranean forest. The aim was to investigate the effects of drought conditions expected to occur over the coming decades, on the contents and concentrations of phosphorus (P) and potassium (K) in stand biomass, and P and K content and availability in soils. 3Drought (an average reduction of 15% in soil moisture) increased P leaf concentration by 18·2% and reduced P wood and root concentrations (30·9% and 39·8%, respectively) in the dominant tree species Quercus ilex, suggesting a process of mobilization of P from wood towards leaves. The decrease in P wood concentrations in Quercus ilex, together with a decrease in forest biomass growth, led to an overall decrease (by approximately one-third) of the total P content in above-ground biomass. In control plots, the total P content in the above-ground biomass increased 54 kg ha,1 from 1999 to 2005, whereas in drought plots there was no increase in P levels in above-ground biomass. Drought had no effects on either K above-ground contents or concentrations. 4Drought increased total soil soluble P by increasing soil soluble organic P, which is the soil soluble P not directly available to plant capture. Drought reduced the ratio of soil soluble inorganic P : soil soluble organic P by 50% showing a decrease of inorganic P release from P bound to organic matter. Drought increased by 10% the total K content in the soil, but reduced the soil soluble K by 20·4%. 5Drought led to diminished plant uptake of mineral nutrients and to greater recalcitrance of minerals in soil. This will lead to a reduction in P and K in the ecosystem, due to losses in P and K through leaching and erosion, if the heavy rainfalls predicted by IPCC (Intergovernmental Panel on Climate Change) models occur. As P is currently a limiting factor in many Mediterranean terrestrial ecosystems, and given that P and K are necessary for high water-use efficiency and stomata control, the negative effects of drought on P and K content in the ecosystem may well have additional indirect negative effects on plant fitness. [source] | |||||||||||||||||||||||||||||||||||||||||||