Indicators Of Ecosystem Function Research Articles

Realizing ecosystem services: wetland hydrologic function along a gradient of ecosystem condition

Wetlands provide numerous ecosystem services, from habitat provision to pollutant removal, floodwater storage, and microclimate regulation. Delivery of particular services relies on specific ecological functions, and thus to varying degree on wetland ecological condition, commonly quantified as departure from minimally impacted reference sites. Condition assessments are widely adopted as regulatory indicators of ecosystem function, and for some services (e.g., habitat) links between condition and function are often direct. For others, however, links are more tenuous, and using condition alone to enumerate ecosystem value (e.g., for compensatory mitigation) may underestimate important services. Hydrologic function affects many services cited in support of wetland protection both directly (floodwater retention, microclimate regulation) and indirectly (biogeochemical cycling, pollutant removal). We investigated links between condition and hydrologic function to test the hypothesis, embedded in regulatory assessment of wetland value, that condition predicts function. Condition was assessed using rapid and intensive approaches, including Florida's official wetland assessment tool, in 11 isolated forested wetlands in north Florida (USA) spanning a land use intensity gradient. Hydrologic function was assessed using hydrologic regime (mean, variance, and rates of change of water depth), and measurements of groundwater exchange and evapotranspiration (ET). Despite a wide range in condition, no systematic variation in hydrologic regime was observed; indeed reference sites spanned the full range of variation. In contrast, ET was affected by land use, with higher rates in intensive (agriculture and urban) landscapes in response to higher leaf area. ET determines latent heat exchange, which regulates microclimate, a valuable service in urban heat islands. Higher ET also indicates higher productivity and thus carbon cycling. Groundwater exchange regularly reversed flow direction at all sites in response to rainfall. This buffering effect on regional aquifer levels, an underappreciated service of isolated wetlands, was provided regardless of condition. Intensive landscapes may benefit most from the hydrologic services that wetlands provide because that is where certain services (floodwater storage, microclimate regulation) are realized. While the portfolio of wetland services clearly changes with disturbance, our results support a revised approach to wetland valuation that recognizes the services that accrue from sustained or enhanced functions in these "working wetlands."

Evaluating the performance of multiple remote sensing indices to predict the spatial variability of ecosystem structure and functioning in Patagonian steppes

Assessing the spatial variability of ecosystem structure and functioning is an important step towards developing monitoring systems to detect changes in ecosystem attributes that could be linked to desertification processes in drylands. Methods based on ground-collected soil and plant indicators are being increasingly used for this aim, but they have limitations regarding the extent of the area that can be measured using them. Approaches based on remote sensing data can successfully assess large areas, but it is largely unknown how the different indices that can be derived from such data relate to ground-based indicators of ecosystem health. We tested whether we can predict ecosystem structure and functioning, as measured with a field methodology based on indicators of ecosystem functioning (the landscape function analysis, LFA), over a large area using spectral vegetation indices (VIs), and evaluated which VIs are the best predictors of these ecosystem attributes. For doing this, we assessed the relationship between vegetation attributes (cover and species richness), LFA indices (stability, infiltration and nutrient cycling) and nine VIs obtained from satellite images of the MODIS sensor in 194 sites located across the Patagonian steppe. We found that NDVI was the VI best predictor of ecosystem attributes. This VI showed a significant positive linear relationship with both vegetation basal cover (R2=0.39) and plant species richness (R2=0.31). NDVI was also significantly and linearly related to the infiltration and nutrient cycling indices (R2=0.36 and 0.49, respectively), but the relationship with the stability index was weak (R2=0.13). Our results indicate that VIs obtained from MODIS, and NDVI in particular, are a suitable tool for estimate the spatial variability of functional and structural ecosystem attributes in the Patagonian steppe at the regional scale.

Marine Ecosystem Connections: essential indicators of healthy, productive and biologically diverse seas

Welcome to this Special Issue of Biogeochemistry, which highlights the key research findings from a fiveyear study entitled ‘‘Marine Ecosystem Connections: essential indicators of healthy, productive and biologically diverse seas’’. The overall aims of the programme were to improve our scientific understanding of the functioning of shelf seas, develop tools for predicting the impact of human activity on ecosystem structure and function, and contribute to the development of indicators for assessments of ecosystem health and environmental status. Key to these studies was the focus on linkages between benthic and pelagic food webs, in response to environmental drivers (Fig. 1), and an underpinning requirement to link the research on biogeochemical cycling to the development of tools and approaches for improved management of marine resources. Around the world, in countries such as Australia, Canada, China, North America and South Africa, recent policy and legislative drivers require integrated, ecosystem-based assessments of the impacts of human activities (see Borja et al. 2008; Elliott 2011). In Europe, for example, the Marine Strategy Framework Directive (MSFD, CEC 2008) aims to achieve Good Environmental Status (GES) in all water bodies by 2020, and requires that ‘‘the structure, functions and processes of the constituent marine ecosystems’’ allow them ‘‘to function fully and to maintain their resilience to human-induced environmental change’’, taking account of ‘‘associated physiographic, geographic, geological and climatic factors’’. A number of coastal and marine regions, including the North Sea, have therefore become the focus of ongoing research on ecosystem structure and function, and the development of indicators for assessing environmental status (see COM 2010). Studies carried out during ‘Marine Ecosystem Connections’ (MEC) are part of this effort. A combined fieldwork and modelling approach was used to quantify carbon and nitrogen fluxes through pelagic and benthic food webs in the temperate North Sea, to predict the impacts of climate change and demersal trawling on these fluxes (van der Molen et al. 2012), and to select and evaluate indicators of ecosystem functioning in terms of their suitability for assessing and managing the impacts of climate change and demersal trawling (Painting et al. 2012). For the pelagic food web, only lower trophic levels (up to zooplankton) were considered, as they have fast turnover rates and are useful as early warning indicators of environmental change. For the benthic food web, the main functional groups of the faunal communities were considered. Coupled physical-biogeochemical models (GOTM-ERSEM-BFM) were developed to improve their suitability for temperate shelf seas (see van der Molen et al. 2012), e.g. through parameterisation to allow growth of diatoms S. J. Painting (&) R. M. Forster Centre for Environment, Fisheries and Aquaculture Science (Cefas), Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK e-mail: suzanne.painting@cefas.co.uk

Spatial Variability of Stable Isotope Ratios in Oysters (Crassostrea gigas) and Primary Producers Along an Estuarine Gradient (Bay of Brest, France)

This study aimed at characterizing the diet of the oyster Crassostrea gigas along an estuarine gradient in the Bay of Brest (France), through stable isotope (δ13C and δ15N) measurements in primary producers and wild oysters. The contribution of different potential food sources to the diet of C. gigas was estimated at high spatial resolution (over a gradient of 40 km with samplings every 2 km) to identify ecological transition zones and highlighted the dominance of resuspended biofilm in oysters diet. Although the different primary producers did not display any obvious pattern along the estuarine gradient, the stable isotope signatures of C. gigas differed among estuarine, inner Bay, and open sea sites. In particular, a striking 15N depletion pattern was found along the gradient which allowed to identify seven homogeneous groups. Moreover, some unexpected values found at two stations within the estuary revealed localized anthropogenic disturbances. Overall, our results suggest that suspension feeders might be better indicators of ecosystem functioning than primary producers and reflect the different ecological processes occurring along estuarine gradients, including localized anthropogenic inputs. We suggest that the usefulness of suspension feeders as indicators of ecosystem functional typology lies in the dominance of benthic material in their diet, which results in locally occurring processes being reflected in oysters’ stable isotope ratios.

Describing avifaunal richness with functional and structural bioindicators derived from advanced airborne remotely sensed data

We investigate whether the richness of distinct avian guilds (species grouped together based on similar exploitation of environmental resources) can be described using indicators of ecosystem function and tree species diversity derived from hyperspectral data and/or aspects of vegetation structure derived from lidar. Bird surveys facilitated discriminant analyses to establish which variables best differentiated between guilds. Akaike's Information Criterion (AIC) and generalized linear models (GLMs) were then utilized to develop predictive models. Bioindicators representing foliar water content and tree species diversity were the most useful hyperspectrally derived variables for differentiating between guilds (p < 0.01) and were most often selected for describing richness. Using ecosystem function bioindicators alone, the adjusted coefficient of determination (R 2 adj) of GLMs ranged from 0.32 (generalist) to 0.58 (forest). In contrast, mean under-, mid-, and overstorey cover and mean surface elevation were the most useful structural bioindicators for guild differentiation (p < 0.05) and were most often selected for describing richness. R 2 adj of GLMs built from structural bioindicators alone ranged from 0.19 (generalist) to 0.64 (forest). Overall, structural bioindicators described more variance for open country and forest guilds, whereas functional bioindicators explained more variance for generalist bird species and all guilds considered concurrently. Simultaneously considering functional and structural bioindicators accounted for the most variance in richness (59%) for open country birds; however, combining bioindicator types did not improve upon the best models for generalist and/or forest guilds.

Landscape effects of disturbance, habitat heterogeneity and spatial autocorrelation for a ground beetle (Carabidae) assemblage in mature boreal forest

Ground beetle (Carabidae) assemblages are speciose and frequently employed as indicators of ecosystem function. It is thus important to understand the factors that affect their spatial distributions so as to better interpret how ecosystem variation influences the structure of their assemblages. We evaluated how anthropogenic disturbances, habitat heterogeneity, and spatial autocorrelation (unmeasured spatially structured habitat variables and/or dispersal limitation) influence the distribution of carabids on a mature boreal forest landscape. We worked with a large sample of carabids from 194 sites from a near‐regular grid covering 70 km2. Data about forest floor cover, vegetation structure, soil drainage, and topography were associated with each site. We modelled the structure of carabid assemblages using these variables together with Moran’s eigenvector maps (MEM) as spatial constraints. Overall, our model explained about half of the variation in ground beetle assemblages. Forest floor cover, soil drainage, and vegetation structure were the principal factors useful for explaining carabid assemblages. The spatial patterns described by the MEMs for the ground beetle assemblages seem to result from spatial autocorrelation in soil drainage, floor cover, topography, and vegetation structure; however, this spatial autocorrelation independently and uniquely explained only 1.4% of the variation in assemblages. This was much less important than the explanatory power of the environmental variables considered; e.g. ground cover descriptors and vegetation structure by themselves accounted, respectively, for 12.1 and 4.5% of the variation in the carabid data. The spatial distribution of ground beetles in undisturbed forest was only mildly affected by surrounding anthropogenic disturbances, but clearly small patches were invaded by species characteristic of open habitat. We conclude that to help conserve ground beetle diversity at the landscape scale in boreal forests, mature forest patches should be large and connected to other patches and the surrounding forest.

Understory plant community responses to hazardous fuels reduction treatments in pinyon-juniper woodlands of Arizona, USA

Although hazardous fuels reduction projects are being implemented widely in dry forests of the western United States, information concerning ecological responses of pinyon-juniper woodlands to fuels treatments is minimal. In this study we used a randomized block experimental design to investigate effects of fuels treatments on understory responses at a pinyon-juniper woodland site in northern Arizona. Treatment alternatives replicated (n=12) on 1-ha units across the 760-ha site were thinning from below (Thin), prescribed burning, (Burn), thinning followed by prescribed burning (Thin+Burn), and untreated controls (Control). We measured cover of vascular plant species, biological soil crust, and forest floor substrate prior to treatment and one year, 2years, and five years post-treatment. After five years, Thin and Thin+Burn plots showed statistically similar total plant cover but both showed significantly greater cover than Burn and Control plots. Cover increases on Thin+Burn plots were driven mainly by annual forb and nonnative species groups. Graminoid species with the C4 photosynthetic pathway showed significantly greater cover in all treatment groups compared with Control plots. Burning alone tended to reduce shrub cover whereas thinning alone tended to increase shrub cover. We found no significant effects of treatment on cover of biological soil crust or bare soil. Regression analysis showed significant negative relationships between total understory plant cover and overstory canopy cover on burned and unburned plots. We found no significant effect of treatment on species richness over the measurement period. We observed 124 taxa in total, and mean richness ranged from 31.8 to 36.8 species per 500m2 in 2011. Similar to results for plant cover, we found significantly greater numbers of annual forb species in Thin+Burn compared with Control plots and significantly greater numbers of nonnative species in Thin+Burn compared with all other treatment groups. Permutational multivariate analysis of variance showed no significant differences in overall plant community composition among treatments. These results indicate that fuel reduction treatments on woodland sites may not dramatically affect understory abundance or composition within five years. Although treatments did not significantly differ in cover of biological soil crust or bare soil – indicators of ecosystem function – our results showed that thinning treatments followed by prescribed fire led to increases in cover of nonnative plant species.

Detecting shifts in ecosystem functioning: The decoupling of fundamental relationships with increased pollutant stress on sandflats

In this study, we investigated the influence of low level contamination by copper, lead and zinc on the functioning of estuarine sandflat ecosystems by comparing the strength and variability of relationships between benthic macrofauna and fluxes (oxygen and nutrients) at three clean and three mildly contaminated sites. Specifically, as indicators of ecosystem functioning, we examined relationships between bivalve biomass, total benthic respiration and ammonium release, and ammonium uptake and benthic primary production. Furthermore, a small amount of organic matter was added to experimental plots at all sites (35g/0.2m2) to evaluate stress-on-stress responses relative to controls. Relationships were strongest at the clean sites (steepest slopes, highest r2 values, lowest p-values) and weakest at the mildly contaminated sites and in organically enriched plots. Our results suggest that changes in ecosystem functioning may be occurring at mild (<ERL) levels of pollution that are unlikely to cause widespread mortality of macrofauna.

Development of indicators of ecosystem functioning in a temperate shelf sea: a combined fieldwork and modelling approach

A conceptual model of the main carbon and nitrogen flows through pelagic and benthic food webs was used to identify the key biogeochemical processes representing ecosystem functioning, and to select indicators of each of these processes. A combined fieldwork and modelling approach was used to provide the data required to evaluate the indicators in terms of their suitability for assessing and managing the impacts of climate change and demersal trawling. Four of our 16 proposed indicators (phytoplankton production and productivity, near-bed oxygen concentrations and oxygen penetration of the seabed) met the majority of criteria we used for evaluating indicators. Five indicators (depth of anoxic sediment, zoobenthos biomass, production, productivity and bioturbation potential) did not comply with sufficient criteria to be considered as good indicators. Six of our proposed indicators (zooplankton biomass, size structure, production and productivity; ecosystem productivity; ecosystem balance) could not be assessed for sensitivity and specificity using our models, and therefore need to be addressed in future work aimed at improving both the models and the fieldwork. Our results indicate that evaluation of indicators is difficult, because of the number and variety of human pressures which need to be considered in reality, and the interactions between these pressures and the ecosystem components which they affect. The challenge will be to establish if there are indeed any indicators which are able to meet the majority of criteria for good indicators in holistic ecosystem-based assessments.

Persistent Metal Contamination Limits Lotic Ecosystem Heterotrophic Metabolism after More Than 100 Years of Exposure: A Novel Application of the Resazurin Resorufin Smart Tracer

Persistent stress from anthropogenic metal deposition in lotic ecosystems is a global concern. This long-term selective pressure shapes hyporheic microbial assemblages and influences ecosystem functional integrity. We hypothesized that, even after 100 years of adaptation opportunity, ecosystem function remains inhibited by sediment-associated metal stress and that the Resazurin Resorufin Smart Tracer can be used to quantify this impact. The Resazurin Resorufin Smart Tracer system is applied here in a novel capacity as an indicator of ecosystem function by quantifying ecosystem respiration of microbial communities. Hyporheic microbial communities exposed to differing magnitudes of chronic metal stress were compared to pristine reference sites in controlled column experiments. A Markov chain Monte Carlo technique was developed to solve the inverse smart tracer transport equation to derive community respiration data. Results suggest metals inhibit respiration by 13-30% relative to reference sites and this inhibition is directly related to the level of in situ metal stress. We demonstrate the first application of a hydrologic smart tracer as a functional indicator of ecological integrity within anthropogenically influenced flowing water systems and provide data suggesting resilience is limited in hyporheic ecosystems even after more than a century of microbial adaption to chronic pollutants.

Epiphytic lichens as indicator of land-use pattern and forest harvesting in a community forest in west Nepal

Human inhabitance and agriculture have fundamentally altered global pattern of biodiversity and ecosystem processes. Therefore, integration of community-based approach is an effective conservation strategy. Community forestry is an important community-based approach, which can help in conserving local ecological assets in a sustainable manner. Lichens are known to be more sensitive indicators of ecosystem functions and disturbances than any other cryptogam and vascular plant community. Present study reports a preliminary assessment of epiphytic lichens in a community forest in Dadeldhura district, west Nepal, in order to identify potential indicator of forest health and land-use pattern. Epiphytic (corticolous) lichens were sampled from ten land-use units (LUU), using narrow frequency grids of 10 cm × 50 cm, each divided into five sampling units of 10 cm × 10 cm, on the bark of selected tree species. Quercus leucotrichophora was the dominant phorophyte followed by Pinus roxburghii, Rhododendron arboreum and Myrica esculenta. Foliose parmeloid (Parmotrema spp., Heterodermia spp., Hypotrachyna spp., Bulbothrix spp., Canoparmelia spp., Canomaculina spp.) was the most abundant lichen group, found inhabiting all the phorophytes followed by crustose, fruticose and dimorphic growth forms. Maximum diversity of parmeloid lichens was recorded on older stand of Quercus while younger stands usually harbored crustose lichens (e.g., Lecanora spp., Basidia spp.). Though the lichen diversity increased from outer fringes of the forest to the core, the vegetation stand age was not distributed in any consistent pattern suggesting unconstrained harvesting of the forest. Lichen diversity was found constrained by phorophyte determinants (stand age, aspect, and bark properties) and community harvesting of the forest.doi: http://dx.doi.org/10.3126/botor.v8i0.5555 Botanica Orientalis – Journal of Plant Science (2011) 8: 24-32

Terricolous lichens as indicator of anthropogenic disturbances in a high altitude grassland in Garhwal (Western Himalaya), India

Lichens are known to be more sensitive indicators of ecosystem functioning and disturbances than any other cryptogams and vascular plant communities. Himalayan habitats, despite their stressed climates, harbor some of the unique biodiversity of the region, vital for overall ecosystem functioning and stability. Lichens, due to their desiccation tolerance, are able to survive in high altitude habitats and evolved into diverse categories and functional groups. Present study examines the terricolous lichen community in Chopta-Tungnath temperate-alpine grassland of Garhwal Himalaya, in order to identify potential elements (species/growth form) as indicator of anthropogenic disturbances. Terricolous lichens were sampled from twelve sites distributed in three stratified macrohabitats, along increasing altitudinal gradient. A total of twenty soil lichen species belonging to ten genera, six families and four morphological groups (i.e. leprose, foliose, dimorphic and fruticose) were identified. Terricolous lichen diversity was negatively correlated (r = 0.70; p&lt;0.05) with altitude. Among the four growth forms, fruticose growth form was indicator of grazing disturbance, distinguishing low grazed high altitude (3400-4001 m asl) areas with highly grazed low altitude (2700-3000 m asl) to mid altitude (3000-3400 m asl) areas. Terricolous lichen diversity in the study area was found constrained by vascular plants at lower altitudes, human-related impacts (tourism and livestock grazing induced trampling) at mid-altitudes and habitat characteristics (low soil cover) at higher altitudes.doi: http://dx.doi.org/10.3126/botor.v8i0.5554 Botanica Orientalis – Journal of Plant Science (2011) 8: 16-23

Functional diversity indices reveal the impacts of land use intensification on plant community assembly

1. Functional diversity has been suggested as an important descriptor of an assemblage and as an indicator of ecosystem function. However, there has been little testing of recent functional diversity measures on field data and across environmental gradients of disturbance and productivity. This study tested how three recently developed measures of functional diversity behave in practice and what could be deduced about assembly rules operating in the systems studied. 2. Data from 30 plant communities in a small area, comprising arable fields, mown and grazed grasslands, moorland and woodland, were analysed in terms of these diversity indices. Functional Divergence, Evenness and Richness were independent of each other, but Richness correlated to species diversity through the sampling effect. 3. As evidenced by reduced Functional Richness, habitat filtering operated at a significant proportion of the sites sampled. Functional Richness was also reduced against expectations at high levels of both productivity and disturbance. Functional Divergence showed no clear patterns, but Functional Evenness showed a clear promotion by disturbance and a reduction at high standing biomass. 4. Synthesis. Knowledge of how functional diversity is related to the environment provides indications of the processes governing community assembly, and the possibility of developing them as measures of ecosystem function.

Remote sensing data predict indicators of soil functioning in semi-arid steppes, central Spain

A substantial part of current research efforts on desertification are devoted to establish monitoring systems to evaluate the status of natural resources and the onset of desertification processes. Methodologies based on ground-collected soil and plant indicators are being increasingly used for this aim because they are affordable yet do not compromise accuracy. Despite their inherent value, these methods have limitations regarding the extent of the area that can be monitored using them. Such limitations can be overcome combining field-based approaches with remote sensing data, which allow the establishment of monitoring programs over large areas. In this article we tested the relationship between a field methodology based on indicators of ecosystem functioning, the landscape function analysis (LFA), and a vegetation index (NDVI) obtained from satellite images of the ASTER sensor using data gathered in Stipa tenacissima steppes from central Spain. LFA uses soil surface indicators to assess the condition of a given ecosystem by producing three numerical indices (stability, infiltration and nutrient cycling) reflecting the status of basic soil functions. We found a significant positive linear relationship between the NDVI, the three LFA indices and some key structural attributes of vegetation related to the cover of perennial plants. Our results indicate that NDVI can be used as a surrogate of ecosystem functioning in semi-arid Mediterranean steppes, and thus can be a helpful index to monitor the functional status of large areas in these ecosystems, and the possible onset of desertification processes.

Analysis of historic changes in regional ecosystem service provisioning using land use data

Land use change has a major impact on goods and services that our environment supplies for society. While detailed ecological or biophysical field studies are needed to quantify the exact amount of ecosystem service supply at local scales, such a monitoring might be unfeasible at the regional scale. Since field scale monitoring schemes for ecosystem services or ecosystem functioning are missing, proxy based indicators can help to assess the historic development of ecosystem services or ecosystem functioning at the regional scale. We show at the example of the historic development (1964–2004) in the district of Leipzig/Germany how land use/land cover data can be used to derive regional scale indicators for ecosystem functions. We focus thereby on two hypotheses: (1) the ecosystem functioning has degraded over time and (2) changes in land use configuration play an important role in this degradation. The study focuses on indicators for ecosystem functions related to (i) water purification by riparian buffer strips, (ii) pollination, (iii) food production and (iv) outdoor recreation. Each indicator builds on the analysis of land use configuration and land use composition information and is tested on sensitivity/robustness with respect to parameters which had to be estimated based on expert knowledge. We show that land use composition is an important aspect in our ecosystem service assessment. Although our study region is faced with a maximum land use change of 11% in the major land use classes between 1964 and 2004, we see a decrease of ecosystem function indicators up to 23%. The regional assessment shows an overall trend for degradation of ecosystem functioning from 1964 to 1984. This trend is reversed between 1984 and 1994 but the process slowed down until 2004 without reaching the level of 1964.

Biodiversity and multiple ecosystem functions in an organic farmscape

To increase ecosystem services provided by their lands, farmers in the United States are managing non-production areas to create a more biodiverse set of habitats and greater landscape heterogeneity. Relatively little is known, however, of the actual environmental outcomes of this practice, termed ‘farmscaping’. We inventoried communities of plant and soil organisms and monitored indicators of ecosystem functions in six distinct habitats of an organic farm in California's Central Valley to better understand the ecological costs and benefits of farmscaping. A riparian corridor, hedgerows, a system of drainage ditches, and tailwater ponds supported different plant life history/functional groups and greater native plant diversity than the two production fields. Differences were less pronounced for belowground organisms, i.e., nematode functional groups, microbial communities (based on phospholipid fatty acid (PLFA) analysis) and earthworm taxa. Partial ordination analysis showed that environmental variables, rather than spatial location, explained much of the distribution of soil and plant taxa across the farmscape. Riparian and hedgerow habitats with woody vegetation stored 18% of the farmscape's total carbon (C), despite occupying only 6% of the total area. Infiltration rates in the riparian corridor were >230% higher than those observed in the production fields, and concentrations of dissolved organic carbon (DOC) in soil solution were as much as 65% higher. The tailwater pond reduced total suspended solids in irrigation runoff by 97%. Drainage ditches had the highest N 2O-N emissions (mean values of 16.7 μg m −2 h −1) and nitrate (NO 3 −-N) leaching (12.1 g m −2 year −1 at 75 cm depth). Emissions of N 2O-N and leaching of NO 3 −-N were, however, quite low for all the habitats. Non-production habitats increased biodiversity (particularly plants) and specific ecosystem functions (e.g. water regulation and carbon storage). Extrapolating relative tradeoffs to the entire farmscape showed that greater habitat enhancement through farmscaping could increase both biodiversity and multiple ecosystem functions of agricultural lands with minor loss of production area.

Biodiversity is associated with indicators of soil ecosystem functions over a landscape gradient of agricultural intensification

Agricultural intensification has led to dramatic losses in biodiversity over the past several decades. Many studies have shown the effects of intensification on vegetation or soil communities at field or local scales. However, the functional signif- icance of biodiversity may only appear at larger spatial and temporal scales, due to exchanges among local ecosystems throughout a landscape. To examine how patterns of biodiversity loss are reflected at larger spatial scales, plant and soil biodiversity and associated indicators of ecosystem functions were assessed in riparian areas over a 150 km 2 agricultural landscape in the Sacramento Valley of California. Publicly-available GIS data were first used to classify and select sites over the range of soils, topography and plant community types. Representative sites from the landscape were sampled for soil physiochemical properties, as well as microbial, nematode, and plant communities. Higher agricultural intensification, based on field and landscape indices, was negatively correlated with richness and diversity of plant and soil taxa, and was related to indicators of ecosystem functions, such as increased soil nitrate and phos- phorus loading, decreased riparian health ratings, and lower soil carbon, soil microbial biomass and soil food web structure. Both field- and landscape-scale factors played important roles in the measured losses. The study area was composed of a wide array of soils, vegetation, and land management, indicating that the observed trends transcended site-specific conditions.

Searching for effective indicators of ecosystem function in urban streams: assessing cellulose decomposition potential

Summary1. Urbanisation and landuse changes threaten the ecological integrity of rivers and streams globally. A major challenge in such impacted environments is to develop functional indicators for use by waterway managers. We first reviewed cellulose decomposition potential (CDP) as one such indicator, and here present current understanding and highlight the knowledge gaps which hinder its widespread incorporation into programmes monitoring stream health. In a field study, we also evaluated two differing cellulose materials (Shirley soil burial test material and unbleached calico) and measurement techniques.2. We also investigated the effects of urbanisation and riparian cover on CDP as a standardised indicator of ecosystem function. Cotton fabrics were deployed in paired open and closed reaches across six stream catchments varying in degree of urbanisation (in south‐eastern Australia). After 7, 14 and 21 days materials were retrieved and their decomposition assessed in conjunction with a number of physicochemical variables.3. We observed a strong positive relationship between the decomposition of Shirley and calico materials, thus indicating unbleached calico is an effective substitute for Shirley test cloth, which is no longer available.4. Across sites, CDP was positively correlated with ammonium concentrations and also, to a lesser extent, with filterable reactive phosphorus and sediment silt and clay content/carbon availability. Despite these relationships, cellulose decomposition was not correlated with urbanisation or riparian cover.5. Cellulose decomposition is a simple, rapid and sensitive functional indicator of water quality and associated anthropogenic landuse changes and is thus a valuable tool for monitoring stream health.

Do biotic interactions modulate ecosystem functioning along stress gradients? Insights from semi-arid plant and biological soil crust communities.

Climate change will exacerbate the degree of abiotic stress experienced by semi-arid ecosystems. While abiotic stress profoundly affects biotic interactions, their potential role as modulators of ecosystem responses to climate change is largely unknown. Using plants and biological soil crusts, we tested the relative importance of facilitative-competitive interactions and other community attributes (cover, species richness and species evenness) as drivers of ecosystem functioning along stress gradients in semi-arid Mediterranean ecosystems. Biotic interactions shifted from facilitation to competition along stress gradients driven by water availability and temperature. These changes were, however, dependent on the spatial scale and the community considered. We found little evidence to suggest that biotic interactions are a major direct influence upon indicators of ecosystem functioning (soil respiration, organic carbon, water-holding capacity, compaction and the activity of enzymes related to the carbon, nitrogen and phosphorus cycles) along stress gradients. However, attributes such as cover and species richness showed a direct effect on ecosystem functioning. Our results do not agree with predictions emphasizing that the importance of plant-plant interactions will be increased under climate change in dry environments, and indicate that reductions in the cover of plant and biological soil crust communities will negatively impact ecosystems under future climatic conditions.

Not all ski slopes are created equal: Disturbance intensity affects ecosystem properties

In mountain regions around the world, downhill ski areas represent a significant source of anthropogenic disturbance while also providing recreation and revenue. Ski-run creation always results in some level of disturbance, but disturbance intensity varies greatly with construction method. Ski runs may be established either by clearing (cutting and removing tall vegetation) or by clearing and then machine-grading (leveling the soil surface with heavy equipment). To quantify how these different intensities of initial disturbance affect ecosystem properties, we extensively surveyed vegetation, soils, and environmental characteristics on cleared ski runs, graded ski runs, and adjacent reference forests across seven large downhill ski resorts in the northern Sierra Nevada, USA. We found that the greater disturbance intensity associated with grading resulted in greater impacts on all ecosystem properties considered, including plant community composition and diversity, soil characteristics relating to processes of nutrient cycling and retention, and measures of erosion potential. We also found that cleared ski runs retained many ecological similarities to reference forests and might even offer some added benefits by possessing greater plant species and functional diversity than either forests or graded runs. Because grading is more damaging to multiple indicators of ecosystem function, clearing rather than grading should be used to create ski slopes wherever practical.