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PubMed1999

Biodiversity and ecosystem productivity in a fluctuating environment: the insurance hypothesis.

Although the effect of biodiversity on ecosystem functioning has become a major focus in ecology, its significance in a fluctuating environment is still poorly understood. According to the insurance hypothesis, biodiversity insures ecosystems against declines in their functioning because many species provide greater guarantees that some will maintain functioning even if others fail. Here we examine this hypothesis theoretically. We develop a general stochastic dynamic model to assess the effects of species richness on the expected temporal mean and variance of ecosystem processes such as productivity, based on individual species' productivity responses to environmental fluctuations. Our model shows two major insurance effects of species richness on ecosystem productivity: (i) a buffering effect, i.e., a reduction in the temporal variance of productivity, and (ii) a performance-enhancing effect, i.e., an increase in the temporal mean of productivity. The strength of these insurance effects is determined by three factors: (i) the way ecosystem productivity is determined by individual species responses to environmental fluctuations, (ii) the degree of asynchronicity of these responses, and (iii) the detailed form of these responses. In particular, the greater the variance of the species responses, the lower the species richness at which the temporal mean of the ecosystem process saturates and the ecosystem becomes redundant. These results provide a strong theoretical foundation for the insurance hypothesis, which proves to be a fundamental principle for understanding the long-term effects of biodiversity on ecosystem processes.

Ecosystem↗

PubMed2001

Microbial diversity, producer-decomposer interactions and ecosystem processes: a theoretical model.

Interactions between the diversity of primary producers and that of decomposers--the two key functional groups that form the basis of all ecosystems--might have major consequences on the functioning of depauperate ecosystems. I present a simple ecosystem model in which primary producers (plants) and decomposers (microbes) are linked through material cycling. The model considers a diversity of plant organic compounds and a diversity of microbial species. Nutrient recycling efficiency from organic compounds to decomposers is then the key parameter that controls ecosystem processes (primary productivity, secondary productivity, producer biomass and decomposer biomass). The model predicts that microbial diversity has a positive effect on nutrient recycling efficiency and ecosystem processes through either greater intensity of microbial exploitation of organic compounds or functional niche complementarity, much like in plants. Microbial niche breadth and overlap should not affect ecosystem processes unless they increase the number of organic compounds that are decomposed. In contrast, the model predicts that plant organic compound diversity can only have a negative effect or, at best, no effect on ecosystem processes, at least in a constant environment. This creates a tension between the effects of plant diversity and microbial diversity on ecosystem functioning, which may explain some recent experimental results.

Bacteria↗

PubMed2006

Conservation planning for ecosystem services.

Despite increasing attention to the human dimension of conservation projects, a rigorous, systematic methodology for planning for ecosystem services has not been developed. This is in part because flows of ecosystem services remain poorly characterized at local-to-regional scales, and their protection has not generally been made a priority. We used a spatially explicit conservation planning framework to explore the trade-offs and opportunities for aligning conservation goals for biodiversity with six ecosystem services (carbon storage, flood control, forage production, outdoor recreation, crop pollination, and water provision) in the Central Coast ecoregion of California, United States. We found weak positive and some weak negative associations between the priority areas for biodiversity conservation and the flows of the six ecosystem services across the ecoregion. Excluding the two agriculture-focused services-crop pollination and forage production-eliminates all negative correlations. We compared the degree to which four contrasting conservation network designs protect biodiversity and the flow of the six services. We found that biodiversity conservation protects substantial collateral flows of services. Targeting ecosystem services directly can meet the multiple ecosystem services and biodiversity goals more efficiently but cannot substitute for targeted biodiversity protection (biodiversity losses of 44% relative to targeting biodiversity alone). Strategically targeting only biodiversity plus the four positively associated services offers much promise (relative biodiversity losses of 7%). Here we present an initial analytical framework for integrating biodiversity and ecosystem services in conservation planning and illustrate its application. We found that although there are important potential trade-offs between conservation for biodiversity and for ecosystem services, a systematic planning framework offers scope for identifying valuable synergies.

Biodiversity↗

PubMed2003

[Approaches for assessing forest ecosystem health].

Assessment and indicator system become the key issues in the research on ecosystem health in 21st century. Assessing forest ecosystem health gradually attach much attention because it is an important component of terrestrial ecosystem. The definition, measurement, evaluation and its management had been discussed broadly, and some theories, assessing methods and frameworks had been proposed, which provides a new concept and a serial research approaches for dealing with the crisis of terrestrial ecosystems, even the environment problems in the world. Now, the common operational models for assessing forest ecosystem health do not exist owing to the manifold limitations. This paper discussed forest ecosystem health problem, and brought forward three preconditions for assessing forest ecosystem health: 1) a clear conceptual framework; 2) adequate data sets; 3) proper research and analysis techniques. The issues of three preconditions were discussed, and the possible approaches for the assessing research on forest ecosystem health, e.g., long-term studies and environment monitoring, space-for-time substation studies, e.g., history approaches, economics valuation and others were expariated.

Ecosystem↗

PubMed2004

[Ecological regulation services of Hainan Island ecosystem and their valuation].

Ecosystem services imply the natural environmental conditions on which human life relies for existence, and their effectiveness formed and sustained by ecosystem and its ecological processes. In newly research reports, they were divided into four groups, i. e., provisioning services, regulation services, cultural services, and supporting services. To assess and valuate ecosystem services is the foundation of regional environmental reserve and development. Taking Hainan Island as an example and based on the structure and processes of natural ecosystem, this paper discussed the proper methods for regulation services assessment. The ecosystems were classified into 13 types including valley rain forest, mountainous rain forest, tropical monsoon forest, mountainous coppice forest, mountainous evergreen forest, tropical coniferous forest, shrubs, plantation, timber forest, windbreak forest, mangrove, savanna, and cropland, and then, the regulation services and their economic values of Hainan Island ecosystem were assessed and evaluated by terms of water-holding, soil conservancy, nutrient cycle, C fixation, and windbreak function. The economic value of the regulation services of Hainan Island ecosystem was estimated as 2035.88 x 10(8)-2153.39 x 10(8) RMB yuan, 8 times higher to its provisioning services (wood and agricultural products) which were estimated as only 254.06 x 10(8) RMB yuan. The result implied that ecosystem regulation services played an even more important role in the sustainable development of society and economy in Hainan Island.

China↗

PubMed1999

Responses of a loblolly pine ecosystem to CO(2) enrichment: a modeling analysis.

The development of the Free-Air CO(2) Enrichment (FACE) facilities represents a substantial advance in experimental technology for studying ecosystem responses to elevated CO(2). A challenge arising from the application of this technology is the utilization of short-term FACE results for predicting long-term ecosystem responses. This modeling study was designed to explore interactions of various processes on ecosystem productivity at elevated CO(2) on the decadal scale. We used a forest model (FORDYN) to analyze CO(2) responses-particularly soil nitrogen dynamics, carbon production and storage-of a loblolly pine ecosystem in the Duke University Forest. When a 14-year-old stand was exposed to elevated CO(2), simulated increases in annual net primary productivity (NPP) were 13, 10 and 7.5% in Years 1, 2 and 10, respectively, compared with values at ambient CO(2). Carbon storage increased by 4% in trees and 9.2% in soil in Year 10 in response to elevated CO(2). When the ecosystem was exposed to elevated CO(2) from the beginning of forest regrowth, annual NPP and carbon storage in trees and soil were increased by 32, 18 and 20%, respectively, compared with values at ambient CO(2). In addition, simulation of a 20% increase in mineralization rate led to a slight increase in biomass growth and carbon storage, but the simulated 20% increase in fine root turnover rate considerably increased annual NPP and carbon storage in soil. The modeling results indicated that (1) stimulation of NPP and carbon storage by elevated CO(2) is transient and (2) effects of elevated CO(2) on ecosystem processes-canopy development, soil nitrogen mineralization and root turnover-have great impacts on ecosystem C dynamics. A detailed understanding of these processes will improve our ability to predict long-term ecosystem responses to CO(2) enrichment.

Journal Article↗

PubMed1991

Transfer of radiocesium to ruminants in natural and semi-natural ecosystems and appropriate countermeasures.

A review of studies conducted before and after the Chernobyl accident is presented, showing that both the duration and the extent of radiocesium contamination of ruminants will be more severe in unimproved ecosystems compared with agricultural areas. Although such unimproved ecosystems provide comparatively small quantities of food for human consumption, the integrated dose from these areas to the human population can be large. Ecological characteristics that make unimproved ecosystems particularly vulnerable to this form of pollution include the presence of (1) soils that do not immobilize radiocesium and therefore allow its uptake into vegetation; (2) vegetation species with high uptake rates of radiocesium; (3) the predominant utilization by small ruminants which attain higher muscle radiocesium levels than cattle. Unimproved ecosystems, which often are located at high altitudes, are predisposed to receiving higher fallout because of high precipitation rates which enhance the likelihood of deposition. Countermeasures have been developed and used successfully to reduce radiocesium levels in ruminants grazing in unimproved ecosystems. Apart from decontamination by altering farming practices and providing uncontaminated feeds, sustained reductions of 50% to 80% in the radiocesium concentrations of both milk and meat have been achieved in many ruminant species when AFCF is given via a sodium chloride lick or as a sustained-release bolus. Food production in unimproved ecosystems must be evaluated separately from that of ordinary agricultural systems. In addition to detailed studies on the behavior of radiocesium, consideration should be given to the collection of aggregated transfer coefficients from various ecosystems which were affected by Chernobyl fallout. By combining bioavailability estimates and aggregated transfer coefficients, based on Chernobyl and nuclear weapons test fallout data, it may in the future be possible to make a rapid assessment of both the immediate and the long-term impact of a future nuclear accident on food production in unimproved ecosystems.

Animals↗

PubMed1983

[2 rules for the life cycles of cestodes in the ecosystem].

Rule I: The more advanced in its primary evolution the life cycle of a cestode is, the greater is the participation of the animal component of the ecosystem in it. The direct influence of the non-living component of the ecosystem on the course of the cycle is one and the same with both the primarily evolved 2-host and 3-host life cycles within the separate orders. Rule II: In the secondarily evolved life cycles of cestodes, when compared with their initial life cycles, the following things are observed: a) either a decrease of both the participation of the animal component of the ecosystem in the life cycle and the direct influence of the non-living component of the ecosystem on the course of the cycle; b) or a decrease only of the participation of the animal component of the ecosystem in the life cycle, without any change in the direct influence of the non-living component of the ecosystem on the course of the cycle; c) or, quite rarely, a decrease only of the direct influence of the non-living component of the ecosystem on the course of the life cycle, without any change in the participation of the animal component of the ecosystem in the life cycle.

Animals↗

PubMed1999

Stable isotopes in ecosystem science: structure, function and dynamics of a subtropical Savanna.

Stable isotopes are often utilized as intrinsic tracers to study the effects of human land uses on the structural and functional characteristics of ecosystems. Here, we illustrate how stable isotopes of H, C, and O have been utilized to document changes in ecosystem structure and function using a case study from a subtropical savanna ecosystem. Specifically, we demonstrate that: (1) delta 13C values of soil organic carbon record a vegetation change in this ecosystem from C4 grassland to C3 woodland during the past 40-120 years, and (2) delta 2H and delta 18O of plant and soil water reveal changes in ecosystem hydrology that accompanied this grassland-to-woodland transition. In the Rio Grande Plains of North America, delta 13C values of plants and soils indicate that areas now dominated by C3 subtropical thorn woodland were once C4 grasslands. delta 13C values of current organic matter inputs from wooded landscape elements in this region are characteristic of C3 plants (-28 to -25/1000), while those of the associated soil organic carbon are higher and range from -20 to -15/1000. Approximately 50-90% of soil carbon beneath the present C3 woodlands is derived from C4 grasses. A strong memory of the C4 grasslands that once dominated this region is retained by delta 13C values of organic carbon associated with fine and coarse clay fractions. When delta 13C values are evaluated in conjunction with 14C measurements of that same soil carbon, it appears that grassland-to-woodland conversion occurred largely within the past 40-120 years, coincident with the intensification of livestock grazing and reductions in fire frequency. These conclusions substantiate those based on demographic characteristics of the dominant tree species, historical aerial photography, and accounts of early settlers and explores. Concurrent changes in soil delta 13C values and organic carbon content over the past 90 years also indicate that wooded landscape elements are behaving as sinks for atmospheric CO2 by sequestering carbon derived from both the previous C4 grassland and the present C3 woody vegetation. Present day woodlands have hydrologic characteristics fundamentally different from those of the original grasslands. Compared to plants in remnant grasslands, tree and shrub species in the woodlands are rooted more deeply and have significantly greater root biomass and density than grasslands. delta 18O and delta 2H values of plant and soil water confirm that grassland species acquire soil water primarily from the upper 0.5 m of the soil profile. In contrast, trees and shrubs utilize soil water from throughout the upper 4 m of the profile. Thus, soil water that formerly may have infiltrated beyond the reach of the grassland roots and contributed to local groundwater recharge or other hydrologic fluxes may now be captured and transpired by the recently formed woodland plant communities. The natural abundances of stable isotopes revealed fundamental information regarding the impacts of human land use activities on the structure and function of this subtropical savanna. Stable isotopes provided direct, spatially explicit evidence for dramatic changes in ecosystem physiognomy and demonstrated some functional consequences for the hydrologic cycle. Furthermore, grassland-to-woodland conversion has been geographically extensive in the worlds' drylands, suggesting that these ecosystem-level changes in vegetation structure, carbon cycling, and hydrology may have implications for regional/global biogeochemistry and climate.

Carbon Isotopes↗

PubMed1999

Phenotypic diversity and stability of ecosystem processes.

The resistance of an ecosystem to perturbations and the speed at which it recovers after the perturbations, which is called resilience, are two important components of ecosystem stability. It has been suggested that biodiversity increases the resilience and resistance of aggregated ecosystem processes. We test this hypothesis using a theoretical model of a nutrient-limited ecosystem in a heterogeneous environment. We investigate the stability properties of the model for its simplest possible configuration, i.e. , a system consisting of two plant species and their associated detritus and local resource depletion zones. Phenotypic diversity within the plant community is described by differences in the nutrient uptake and mortality rates of the two species. The usual measure of resilience characterizes the system as a whole and thus also applies to aggregated ecosystem processes. As a rule this decreases with increased diversity, though under certain conditions it is maximum for an intermediate value of diversity. Resistance is a property that characterizes each system component and process separately. The resistance of the inorganic nutrient pools, hence of nutrient retention in the ecosystem, decreases with increased diversity. The resistance of both total plant biomass and productivity either monotonically decreases or increases over part of the parameter range with increased diversity. Furthermore, it is very sensitive to parameter values. These results support the view that there is no simple relationship between diversity and stability in equilibrium deterministic systems, whether at the level of populations or aggregated ecosystem processes. We discuss these results in relation to recent experiments.

Ecosystem↗

PubMed2002

Microbial mats and the search for minimal ecosystems.

This article reviews some ecological concepts common to all kinds of ecosystems, describes the characteristics of microbial mats, and focuses on the description of the Ebro Delta microbial mats, to assess whether they fit the concept of a minimal ecosystem. First, microorganisms as components of ecosystems are considered, and some features of microbial life, including ubiquity, size and metabolism, genetic versatility, and strategies to overcome unfavorable conditions, are discussed. Models for ecosystems, regardless of their size, have the same basic components; tropical forests, multilayered planktonic microbial communities, and benthic microbial mats are analogous ecosystems at different scales. The structure--in terms of populations and communities--and ecophysiology of microbial mats are also discussed. The linear distribution of microbial populations along steep gradients of light and hydrogen sulfide allows for the simultaneous presence of different microbial populations. Defining the minimal ecosystem requirements necessary for the survival and proliferation of organisms is crucial in the search for extraterrestrial life and for establishing ecosystems beyond the Earth.

Biofilms↗

PubMed2004

Ecosystem growth and development.

One of the most important features of biosystems is how they are able to maintain local order (low entropy) within their system boundaries. At the ecosystem scale, this organization can be observed in the thermodynamic parameters that describe it, such that these parameters can be used to track ecosystem growth and development during succession. Thermodynamically, ecosystem growth is the increase of energy throughflow and stored biomass, and ecosystem development is the internal reorganization of these energy mass stores, which affect transfers, transformations, and time lags within the system. Several proposed hypotheses describe thermodynamically the orientation or natural tendency that ecosystems follow during succession, and here, we consider five: minimize specific entropy production, maximize dissipation, maximize exergy storage (includes biomass and information), maximize energy throughflow, and maximize retention time. These thermodynamic orientors were previously all shown to occur to some degree during succession, and here we present a refinement by observing them during different stages of succession. We view ecosystem succession as a series of four growth and development stages: boundary, structural, network, and informational. We demonstrate how each of these ecological thermodynamic orientors behaves during the different growth and development stages, and show that while all apply during some stages only maximizing energy throughflow and maximizing exergy storage are applicable during all four stages. Therefore, we conclude that the movement away from thermodynamic equilibrium, and the subsequent increase in organization during ecosystem growth and development, is a result of system components and configurations that maximize the flux of useful energy and the amount of stored exergy. Empirical data and theoretical models support these conclusions.

Animals↗

PubMed2006

The methane sink associated to soils of natural and agricultural ecosystems in Italy.

In the present work, the CH4 sink associated to Italian soils was calculated by using a process-based model controlled by gas diffusivity and microbial activity, which was run by using a raster-based geographical information system. Georeferenced data included land cover CLC2000, soil properties from the European Soil Database, climatic data from the MARS-STAT database, plus several derived soils properties based on published algorithms applied to the above mentioned databases. Overall CH4 consumption from natural and agricultural sources accounted for a total of 43.3 Gg CH4 yr(-1), with 28.1 Gg CH4 yr(-1) removed in natural ecosystems and 15.1 Gg CH4 yr(-1) in agricultural ecosystems. The highest CH4 uptake rates were obtained for natural areas of Southern Apennines and islands of Sardinia and Sicily, and were mainly associated to areas covered by sclerophyllous vegetation (259.7+/-30.2 mg CH4 m(-2) yr(-1)) and broad-leaved forest (237.5 mg CH4 m(-2) yr(-1)). In terms of total sink strength broad-leaved forests were the dominant ecosystem. The overall contribution of each ecosystem type to the whole CH4 sink depended on the total area covered by the specific ecosystem and on its exact geographic distribution. The latter determines the type of climate present in the area and the dominant soil type, both factors which showed to have a strong influence on CH4 uptake rates. The aggregated CH4 sink, calculated for natural ecosystems present in the Italian region, is significantly higher than previously reported estimates, which were extrapolated from fluxes measured in other temperate ecosystems.

Ecosystem↗

PubMed2000

Functional diversity governs ecosystem response to nutrient enrichment.

The relationship between species diversity and ecosystem functioning is a central topic in ecology today. Classical approaches to studying ecosystem responses to nutrient enrichment have considered linear food chains. To what extent ecosystem structure, that is, the network of species interactions, affects such responses is currently unknown. This severely limits our ability to predict which species or functional groups will benefit or suffer from nutrient enrichment and to understand the underlying mechanisms. Here our approach takes ecosystem complexity into account by considering functional diversity at each trophic level. We conducted a mesocosm experiment to test the effects of nutrient enrichment in a lake ecosystem. We developed a model of intermediate complexity, which separates trophic levels into functional groups according to size and diet. This model successfully predicted the experimental results, whereas linear food-chain models did not. Our model shows the importance of functional diversity and indirect interactions in the response of ecosystems to perturbations, and indicates that new approaches are needed for the management of freshwater ecosystems subject to eutrophication.

Animals↗

PubMed2005

Effects of species and functional group loss on island ecosystem properties.

Considerable recent attention has focused on predicting how the losses of species and functional groups influence ecosystem properties, but the extent to which these effects vary among ecosystems remains poorly understood. Island systems have considerable scope for studying how biotic and abiotic factors influence processes in different ecosystems, because they enable the simultaneous study of large numbers of independent replicate systems at ecologically meaningful spatial scales. We studied a group of 30 islands in northern Sweden, for which island size determined disturbance history, and therefore vegetation successional stage and biotic and abiotic ecosystem properties. On each island we conducted a seven-year study that involved experimental removals of combinations of both plant functional groups and plant species. We show that although losses of functional groups and species often impaired key ecosystem processes, these effects were highly context-dependent and strongly influenced by island size. Our study provides evidence that the consequences of biotic loss for ecosystem functioning vary greatly among ecosystems and depend on the specific abiotic and biotic attributes of the system.

Biomass↗

PubMed2003

Eutrophication of freshwater and coastal marine ecosystems: a global problem.

GOAL, SCOPE AND BACKGROUND: Humans now strongly influence almost every major aquatic ecosystem, and their activities have dramatically altered the fluxes of growth-limiting nutrients from the landscape to receiving waters. Unfortunately, these nutrient inputs have had profound negative effects upon the quality of surface waters worldwide. This review examines how eutrophication influences the biomass and species composition of algae in both freshwater and costal marine systems. MAIN FEATURES: An overview of recent advances in algae-related eutrophication research is presented. In freshwater systems, a summary is presented for lakes and reservoirs; streams and rivers; and wetlands. A brief summary is also presented for estuarine and coastal marine ecosystems. RESULTS: Eutrophication causes predictable increases in the biomass of algae in lakes and reservoirs; streams and rivers; wetlands; and coastal marine ecosystems. As in lakes, the response of suspended algae in large rivers to changes in nutrient loading may be hysteretic in some cases. The inhibitory effects of high concentrations of inorganic suspended solids on algal growth, which can be very evident in many reservoirs receiving high inputs of suspended soils, also potentially may occur in turbid rivers. Consistent and predictable eutrophication-caused increases in cyanobacterial dominance of phytoplankton have been reported worldwide for natural lakes, and similar trends are reported here both for phytoplankton in turbid reservoirs, and for suspended algae in a large river CONCLUSIONS: A remarkable unity is evident in the global response of algal biomass to nitrogen and phosphorus availability in lakes and reservoirs; wetlands; streams and rivers; and coastal marine waters. The species composition of algal communities inhabiting the water column appears to respond similarly to nutrient loading, whether in lakes, reservoirs, or rivers. As is true of freshwater ecosystems, the recent literature suggests that coastal marine ecosystems will respond positively to nutrient loading control efforts. RECOMMENDATIONS AND OUTLOOK: Our understanding of freshwater eutrophication and its effects on algal-related water quality is strong and is advancing rapidly. However, our understanding of the effects of eutrophication on estuarine and coastal marine ecosystems is much more limited, and this gap represents an important future research need. Although coastal systems can be hydrologically complex, the biomass of marine phytoplankton nonetheless appears to respond sensitively and predictably to changes in the external supplies of nitrogen and phosphorus. These responses suggest that efforts to manage nutrient inputs to the seas will result in significant improvements in coastal zone water quality. Additional new efforts should be made to develop models that quantitatively link ecosystem-level responses to nutrient loading in both freshwater and marine systems.

Biomass↗

PubMed2003

Food-web constraints on biodiversity-ecosystem functioning relationships.

The consequences of biodiversity loss for ecosystem functioning and ecosystem services have aroused considerable interest during the past decade. Recent work has focused mainly on the impact of species diversity within single trophic levels, both experimentally and theoretically. Experiments have usually showed increased plant biomass and productivity with increasing plant diversity. Changes in biodiversity, however, may affect ecosystem processes through trophic interactions among species as well. An important current challenge is to understand how these trophic interactions affect the relationship between biodiversity and ecosystem functioning. Here we present a mechanistic model of an ecosystem with multiple trophic levels in which plants compete for a limiting soil nutrient. In contrast to previous studies that focused on single trophic levels, we show that plant biomass does not always increase with plant diversity and that changes in biodiversity can lead to complex if predictable changes in ecosystem processes. Our analysis demonstrates that food-web structure can profoundly influence ecosystem properties.

Animals↗

PubMed2007

Total and component carbon fluxes of a Scots pine ecosystem from chamber measurements and eddy covariance.

BACKGROUND AND AIMS: Distinguishing between, and quantifying, the different components of ecosystem C fluxes is critical in predicting the responses of ecosystem C cycling to climate change. The aims of this study were to quantify the photosynthetic and respiratory fluxes of a 50-year-old Scots pine (Pinus sylvestris) ecosystem, and to distinguish respiration of branches with needles from that of stems, and that of soil. METHODS: The CO2 flux of the ecosystem was continuously measured using the eddy covariance (EC) method, and its components (respiration and photosynthesis of a branch with needles, stem and soil surface) were measured with an automated chamber system, from 2001 to 2004. KEY RESULTS: All values below are chamber based. The average temperature coefficient (Q10) of respiration was 2.7, 2.2 and 4.0, respectively, for branch (Rbran), stem (Rstem) and the soil surface (Rsoil). Respiration at a reference temperature of 15 degrees C (R15) was 1.27, 0.49 and 4.02 micromol CO2 m(-2) ground s(-1) for the three components, respectively. Over 4 years, the annual Rbran, Rstem and Rsoil ranged from 196 to 256, 56 to 83 and 439 to 598 g C m(-2) ground year(-1), respectively, with a 4-year average of 227, 72 and 507 g C m(-2) ground year(-1). Annual ecosystem respiration (Reco) was 731, 783, 909 and 751 g C m(-2) ground year(-1) in years 2001-2004, respectively, gross primary production (GPP) was 922, 1030, 1138 and 1001 g C m(-2) ground year(-1), and net ecosystem production (NEP) was 191, 247, 229 and 251 g C m(-2) ground year(-1). The average contribution of Rbran, Rstem and Rsoil to Reco was 29, 9 and 62 %, respectively. Overstorey photosynthesis accounted for 96 % of GPP. The average Reco/GPP ratio was 0.78. Net primary production (NPP) in the 4 years was 469, 581, 600 and 551 g C m(-2) year(-1), respectively, with the NPP/GPP ratio 0.54 averaged over the years. CONCLUSIONS: Respiration from the soil is the dominant component of ecosystem respiration. Differences between years in Reco were due to differences in temperature during the growing season. Rsoil was more sensitive to temperature than Rbran and Rstem, and differences in Rsoil were responsible for the differences in Reco between years.

Carbon↗