Long-term Monitoring Sites Research Articles

The Greater Yellowstone Ecosystem: Challenges for Regional Ecosystem Management

An adaptive management approach is necessary but not sufficient to address the long-term challenges of the Greater Yellowstone Ecosystem (GYE). Adaptive management, in turn, has its own particular challenges, of which we focus on two: science input, and stakeholder engagement. In order to frame our discussion and subsequent recommendations, we place the current management difficulties into their historical context, with special emphasis on the 1990 Vision document, which attempted a broad synthesis of management goals for the ecosystem. After examining these two key challenges in the context of the GYE, we make several recommendations that would allow for more effective ecosystem management in the long term. First, we recommend adoption of the GYE as a site for long-term science research and monitoring with an emphasis on integrative research, long-term federal funding, and public dissemination of data. Second, we conclude that a clearer prioritization of legislative mandates would allow for more flexible ecosystem management in the GYE, a region where conflicting mandates have historically led to litigation antithetical to effective ecosystem management. Finally, we recommend a renewed attempt at an updated Vision for the Future that engages stakeholders (including local landholders) substantively from the outset.

Évolution récente des récifs coralliens des îles de la Guadeloupe et de Saint-Barthélemy

Recent evolution of the coral reefs of Guadeloupe and Saint-Barthélemy Islands.– The Guadeloupe Archipelago (with Guadeloupe, La Désirade, Marie-Galante, Les Saintes and Petite-Terre Islands), St. Barthélemy and St. Martin are located in the Lesser Antilles between 15° 50’ and 18° 00’ N. Guadeloupe possesses a barrier reef on its northern part, fringing reefs on the windward coast and highly diversifi ed non-reef building coral communities on the leeward coast. The other islands shelter fringing reefs and non-reef building coral communities. The coral reefs of the French West Indies are faced with a common set of threats : high rate of sedimentation, due to deforestation and bad land management, and algal proliferation due to an overload of nutrients in the coastal waters coming from excessive use of fertilizers and poor waste waters treatment. Their coral communities have exhibited a low progressive decline since the beginning of the eighties. Long-term monitoring sites have been implemented in Guadeloupe and St. Barthélemy since 2001. Results indicated the existence of a signifi cant tendency of the coral community to degrade over the study period. Moreover, a severe bleaching event appeared in 2005, when the sea temperature overshoot 29° C from mid May to mid November, with maximum values reaching 31° C. In 2006, in spite of normal seawater temperature conditions, an important delayed mortality affected the corals previously weakened by bleaching. As a fi nal result of the 2005 bleaching event, coral coverage on the reefs of Guadeloupe and St. Barthélemy dropped from 30 to 50 % according to the sites. Fish communities did not exhibit immediate impact of the bleaching event.

Biomarkers: a strategic tool in the assessment of environmental quality of coastal waters

Ecosystems are under the pressure of complex mixtures of contaminants whose effects are not always simple to assess. Biomarkers, acting as early warning signals of the presence of potentially toxic xenobiotics, are useful tools for assessing either exposure to, or the effects of these compounds providing information about the toxicant bioavailability. In fact, it has been argued that a full understanding of ecotoxicological processes must consider an integrated multi-level approach, in which molecular impact is related with higher-order biological consequences at the individual, population and community levels. Monitoring programs should make use of this tool to link contaminants and ecological responses fulfilling strategies like those launched by OSPAR (Commissions of Oslo and Paris) Convention on the protection of the marine environment of the North-East Atlantic and the International Council for the Exploration of the Sea (ICES). An overview of the work done in the past few years using biomarkers as in situ tools for pollution assessment in Portuguese coastal waters is presented as a contribution to the set up of a biomonitoring program for the Portuguese coastal zone. Considering the data set available the biomonitoring proposal should include the analysis of biomarkers and effects at individual levels. The aim of the program will include a spatial and temporal characterization of the biomarkers acetyl-cholinesterase, metallothioneins, DNA damage, adenylate energy charge and scope-for-growth levels. The investigation of the spatial variation of biomarkers is crucial to define sites for long term monitoring, which will be integrated with a chemical monitoring program. This framework will be a major contribution to the implementation of a national database for the use of biomarkers along the Portuguese coast.

Documentation of Uncertainties and Biases Associated with Surface Temperature Measurement Sites for Climate Change Assessment

The objective of this research is to determine whether poorly sited long-term surface temperature monitoring sites have been adjusted in order to provide spatially representative independent data for use in regional and global surface temperature analyses. We present detailed analyses that demonstrate the lack of independence of the poorly sited data when they are adjusted using the homogenization procedures employed in past studies, as well as discuss the uncertainties associated with undocumented station moves. We use simulation and mathematics to determine the effect of trend on station adjustments and the associated effect of trend in the reference series on the trend of the adjusted station. We also compare data before and after adjustment to the reanalysis data, and we discuss the effect of land use changes on the uncertainty of measurement. A major conclusion of our analysis is that there are large uncertainties associated with the surface temperature trends from the poorly sited stations. Moreover, rather than providing additional independent information, the use of the data from poorly sited stations provides a false sense of confidence in the robustness of the surface temperature trend assessments.

Root parameters of forest trees as sensitive indicators of acidifying pollutants: a review of research of Japanese forest trees

The root parameters of forest trees can be indicators of a changing environment. We summarize the results of root studies with regard to the effects of acidifying pollutants, especially soil acidification and aluminum toxicity, on various root parameters of Japanese forest trees under experimentally controlled conditions. All root parameters such as biomass, morphology, nutritional status, and physiology can be regarded as indicators, because, under laboratory conditions, root responses occur prior to the responses in the aboveground parts. However, considering the conditions of forest sites, the nutritional status and physiological changes are better indicators of soil acidification and Al stress than the biomass and morphological response. The currently available data suggest that the most important indicator is the Ca/Al molar ratio in roots of Japanese tree species. In order to predict and detect the initial effects of soil acidification, we postulate that the specific root response to the Ca/Al molar ratio of tree roots should be considered as a parameter for use in long-term forest monitoring sites.

DEMOGRAPHIC MODELS INFORM SELECTION OF BIOCONTROL AGENTS FOR GARLIC MUSTARD (ALLIARIA PETIOLATA)

Nonindigenous invasive plants pose a major threat to natural communities worldwide. Biological control of weeds via selected introduction of their natural enemies can affect control over large spatial areas but also risk nontarget effects. To maximize effectiveness while minimizing risk, weed biocontrol programs should introduce the minimum number of host-specific natural enemies necessary to control an invasive nonindigenous plant. We used elasticity analysis of a matrix model to help inform biocontrol agent selection for garlic mustard (Alliaria petiolata (M. Bieb.) Cavara and Grande). The Eurasian biennial A. petiolata is considered one of the most problematic invaders of temperate forests in North America. Four weevil species in the genus Ceutorhynchus (Coleoptera: Curculionidae) are currently considered potential biocontrol agents. These species attack rosettes (C. scrobicollis), stems (C. roberti, C. alliariae), and seeds (C. constrictus) of A. petiolata. Elasticity analyses using A. petiolata demographic parameters from North America indicated that changes in the rosette-to-flowering-plant transition and changes in fecundity consistently had the greatest impact on population growth rate. These results suggest that attack by the rosette-feeder C. scrobicollis, which reduces overwintering survival, and seed or stem feeders that reduce seed output should be particularly effective. Model outcomes differed greatly as A. petiolata demographic parameters were varied within ranges observed in North America, indicating that successful control of A. petiolata populations may occur under some, but not all, conditions. Using these a priori analyses we predict: (1) rosette mortality and reduction of seed output will be the most important factors determining A. petiolata demography; (2) the root-crown feeder C. scrobicollis will have the most significant impact on A. petiolata demography; (3) releases of single control agents are unlikely to control A. petiolata across its full range of demographic variability; (4) combinations of agents that simultaneously reduce rosette survival and seed production will be required to suppress the most vigorous A. petiolata populations. These predictions can be tested using established long-term monitoring sites coupled with a designed release program. If demographic models can successfully predict biocontrol agent impact on invasive plant populations, a continued dialogue and collaboration between empirical and theoretical approaches may be the key to the development of successful biocontrol tactics for plant invaders in the future.

Chemical contamination of the Hudson-Raritan Estuary as a result of the attack on the World Trade Center: Analysis of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in mussels and sediment

The September 11, 2001 attack on the World Trade Center (WTC) resulted in a massive plume of dust and smoke that blanketed lower Manhattan and part of the Hudson-Raritan Estuary (HRE). The NOAA National Status and Trends Mussel Watch Program has long-term monitoring sites in the area and thus had an opportunity to assess the effect of the WTC attack on PAH and PCB contamination of the surrounding estuary. Seven additional sites were added in the Upper HRE to attain higher sampling resolution for comparison with regularly sampled Mussel Watch Project HRE sites. Elevated background levels of PCBs and PAHs in mussel tissue and sediments were high enough before the WTC attack that concentrations were not measurably changed by WTC derived contaminant input.

Key Findings, Science Gaps and Policy Recommendations

In general, changes in climate and UV in the Arctic will have far-reaching impacts, affecting aquatic species of varying trophic levels, the physical environment that makes up their habitat and the chemical properties of that environment, and the processes that act on and within freshwater ecosystems. Interactions of climatic variables such as temperature and precipitation with freshwater ecosystems are highly complex and can be propagated through the ecosystem in ways that are not readily projectable. This reduces our ability to accurately forecast specific effects of climate and ultraviolet-radiation change upon freshwater systems. This is particularly the case when dealing with threshold responses, i.e., those that produce step-wise and/or non-linear effects. Our ability is further hampered simply by our poor understanding of Arctic freshwater systems and their basic interrelationships with climatic and other environmental variables, as well as by a paucity of long-term freshwater monitoring sites and integrated hydroecological research programs in the Arctic. A significant amount of the understanding of potential impacts is based on historical analogues (i.e., historical evidence from past periods of climate change), as well as from a limited number of more recent studies of ecosystem response to environmental variability. Paleoreconstructions indicate that during the most recent period of climatic warming, which followed the Little Ice Age, the Arctic reached its highest average annual temperatures observed in the past 400 years, resulting in glacier retreat, permafrost thaw, and major shifts in freshwater ecosystems. Examples of ecosystem effects included altered water chemistry, changes in species assemblages, altered productivity, and an extended growing-season length. Importantly, however, past natural change in the Arctic occurred at a rate much slower than that projected for anthropogenic climate change over the next 100 years. In the past, organisms had considerable time to adapt; their responses may therefore not provide good historical analogues for what will result under much more rapid climate change. In many cases, the adaptability (i.e., adaptation, acclimation, or migration) of organisms under rapidly changing climate conditions is largely unknown. Unfortunately, no largescale attempts have been made to study the effects of rapid climate change on aquatic ecosystems using controlled experiments, as have been attempted for terrestrial systems (e.g., see International Tundra Experiment studies of tundra plant response in (1). However, field studies in areas that have recently experienced rapid changes in climate have provided important knowledge. Information about ongoing climate change impacts is provided by results from long-term environmental monitoring and research sites in the Arctic, including the case studies used in this assessment (i.e., Northern Quebec and Labrador, Canada (see 2), Toolik Lake, Alaska and Lake Saanajarvi, Finnish Lapland (see 3), and the Zackenberg Valley in northeastern Greenland (see 4).

Climate Impacts on Arctic Freshwater Ecosystems and Fisheries: Background, Rationale and Approach of the Arctic Climate Impact Assessment (ACIA)

Changes in climate and ultraviolet radiation levels in the Arctic will have far-reaching impacts, affecting aquatic species at various trophic levels, the physical and chemical environment that makes up their habitat, and the processes that act on and within freshwater ecosystems. Interactions of climatic variables, such as temperature and precipitation, with freshwater ecosystems are highly complex and can propagate through the ecosystem in ways that are difficult to project. This is partly due to a poor understanding of arctic freshwater systems and their basic interrelationships with climate and other environmental variables, and partly due to a paucity of long-term freshwater monitoring sites and integrated hydro-ecological research programs in the Arctic. The papers in this special issue are an abstraction of the analyses performed by 25 international experts and their associated networks on Arctic freshwater hydrology and related aquatic ecosystems that was initially published by the Arctic Climate Impact Assessment (ACIA) in 2005 as "Chapter 8--Freshwater Ecosystems and Fisheries". The papers provide a broad overview of the general hydrological and ecological features of the various freshwater ecosystems in the Arctic, including descriptions of each ACIA region, followed by a review of historical changes in freshwater systems during the Holocene. This is followed by an assessment of the effects of climate change on broad-scale hydro-ecology; aquatic biota and ecosystem structure and function; and arctic fish and fisheries. Potential synergistic and cumulative effects are also discussed, as are the roles of ultraviolet radiation and contaminants. The nature and complexity of many of the effects are illustrated using case studies from around the circumpolar north, together with a discussion of important threshold responses (i.e., those that produce stepwise and/or nonlinear effects). The issue concludes with summary the key findings, a list of gaps in scientific understanding, and policy-related recommendations.

Predictability of Annual Sediment Loads Based on Flood Events

Water resources managers always are searching for cost-effective monitoring programs that provide maximum information for minimum cost. Monitoring of sediment discharges from streams and rivers is one of the expensive efforts that is always reduced or cut when financial resources are limited. This has resulted in a very limited number of long-term sediment monitoring sites in the United States. Instead of long-term continuous monitoring programs, alternative monitoring approaches could potentially provide reliable estimates of sediment loads at reduced cost. One of those approaches is monitoring sediment loads during flood events and then using that information to estimate annual sediment loads. To test this approach, annual suspended sediment loads calculated based on continuous sediment monitoring were compared with the loads calculated based on monitoring the major floods only. Streams transport large percentages of the annual sediment loads from a watershed during a small number of floods that occur o...

Hydrodynamic response of subduction zones to seismic activity: A case study for the Costa Rica margin

Thermal anomalies in tectonically active areas are often attributed to sub-seafloor fluid circulation and faulting mechanisms, particularly in subduction zones where the largest thrust earthquakes occur. Postseismic fluid flow is enabled by the poroelastic response of the fault system to the earthquake's strain field, as well as by the rupturing of permeability barriers in the vicinity of the fault zone. We investigated the relative importance of these mechanisms on postseismic pore-pressure diffusion and advective heat transport in the subduction zone setting. A two-dimensional numerical fluid flow and heat transport model was developed for the Costa Rica subduction zone offshore of the Nicoya Peninsula. The flow and transport model was coupled with an earthquake strain model to quantify the effects of coseismic strain and permeability enhancement on fluid pressures and temperatures within the Costa Rica margin. Coseismic changes in pore pressure and postseismic pore-pressure diffusion were found to be sensitive to the compressibility of the porous medium, and patterns of pore-pressure recovery were more complex than that predicted by theoretical faulting models. Coseismic contraction and extension of the crust produced high fluid pressures close to the fault, while the inflow of fluid from depth increased fluid pressures several years following the simulated fault slip. Crustal deformation alone was not observed to perturb the temperature field. Laterally extensive permeability increases of two orders of magnitude along the décollement were required to produce small changes in heat flow. Local permeability changes in the upper slope region of least five orders of magnitude were necessary to noticeably affect heat flow. The results of the numerical simulations may help to refine conceptual faulting models and provide guidance for locating long-term hydrologic monitoring sites at Costa Rica and other subduction zones.

Coral Reef Benthic Video Surveys Facilitate Long-Term Monitoring in the Commonwealth of the Northern Mariana Islands: Toward an Optimal Sampling Strategy

This study describes a step-by-step process used to design an effective benthic video survey component of the Commonwealth of the Northern Mariana Islands long-term monitoring program. Documenting abundance of major benthic groups at relatively large spatial scales, at the appropriate localities, can empower monitoring programs with the capacity to detect changes over time and assess whether management practices are working. Most pertinent to any long-term monitoring program is the overriding question: do we have enough information, or statistical power, to detect changes if changes occur? To assess the power of our benthic video surveys to detect change in coral cover and diversity we varied (1) transect lengths, (2) number of transects, (3) number of frames per transect, and (4) number of data points per frame. Five replicated 50-m transects yielded the most consistent estimates with the highest statistical power, compared with more numerous replicates of shorter (35-m and 15-m) transects. Increasing the number of frames analyzed per 50-m transect yielded greater power than increasing the number of data points per frame, but increasing the number of data points was more effective at estimating species richness. The greatest power of detecting a change in the benthos at each site, within a feasible sampling period, was evident using 5 by 50 m random transects, extracting 60 frames per transect, and analyzing five data points on each frame. This optimal sampling strategy was tested at 23 other long-term monitoring sites and yielded 90% power to detect a 20–30% relative change in dominant benthos abundance estimates (benthos >20% coverage). Our study addresses the sampling unit, accuracy, and ways to improve estimates, but this does not remove the onus of concisely stated questions for monitoring programs pertaining to management.

Biodiversity, ecosystem function and plant traits in mature and immature plant communities

Several studies of synthesized herbaceous plant communities have reported a positive relationship between vascular plant diversity and biomass production (Naeem et al. 1994; Tilman et al. 2001), and the European BIODEPTH experiment has been one of the most influential in this regard (Hector et al. 1999). Much, though not all, of the evidence for this relationship has come from experimental communities established from seed and harvested after only a year or two. It is not clear that such immature plant communities would be expected to provide reliable evidence of the relationship between diversity and ecosystem properties. Here we compare the relationship between diversity and biomass in BIODEPTH with that at the long-term monitoring site at Bibury in Gloucestershire, UK (Dunnett et al. 1998), a natural plant community that has much in common with BIODEPTH. The Bibury site offers a rare opportunity to address questions similar to those tackled by BIODEPTH, while avoiding some of the limitations of short-term experiments. If a positive relationship between vascular plant diversity and biomass production is an important phenomenon, one could argue that it should be detectable in natural vegetation. Previous attempts to explore the relationship between biodiversity and productivity in natural plant communities have been criticized on the grounds that both variables are frequently affected by additional (usually abiotic) variables (Lawton et al. 1998). For example, over a wide range of moderate-to-high biomass values, there is a well known negative relationship between biomass and species richness, driven by increasing competitive exclusion at higher productivity (Grime 1973; Grace 1999; Stevens et al. 2004). In experiments such as BIODEPTH, one aim is to exclude such natural sources of variation and create synthesized plant assemblages that vary only in artificially imposed levels of species richness. Of course, random environmental heterogeneity cannot be completely excluded, and Huston & McBride (2002) have shown how such heterogeneity can give rise to spurious diversity-function relationships. However, synthesized communities may also exhibit systematic variation in productivity equalling or exceeding that occurring in natural habitats, arising from the higher nitrogen availability in communities sown with N-fixing legumes. In BIODEPTH, addition of TriJolium pratense (nomenclature follows Stace 1997) increased biomass, on average, by 360 g m (Hector et al. 1999). As this increase was much larger than the effect of any other species, it is reasonable to attribute this effect to a direct result of the extra N fixed by Trifolium. The increase was also much larger than the effect of a change in diversity itself; doubling species richness increased biomass, on average, by only 80 g m-. The Bibury road verge lies on the north side of Akeman Street, originally a Roman road, in Gloucestershire, UK (National Grid reference SP 119048). The 700 m length of experimental verge was originally chosen

Measurements from ground and balloons during APE-GAIA – A polar ozone library

Many long-term monitoring sites in Antarctic regions, which deploy ground-based stratospheric remote sensors and fly radiosondes or ozonesondes on balloons, supported the Airborne Polar Experiment in September and October 1999. Support consisted of supplying data to the campaign in real time, and in some cases by increasing the frequency of measurements during the campaign. The results will strengthen scientific conclusions from the airborne measurements. But results from these sites are allowing important scientific studies of new aspects of the ozone hole in their own right, because like the aircraft and its campaign, many sites traverse the vortex edge and are close to the largest source of lee waves, or measure infrequently observed trace gases such as HNO 3. Examples of such studies are the behaviour and value of NO 2 in midwinter, ozone filamentation with no apparent horizontal advection, the frequency and amplitude of gravity waves over the Antarctic Peninsula, mixing in the lowest stratosphere in Antarctic spring, the mechanism and frequency of HNO 3 enhancement above the ozone peak in midwinter, and trends in UV dose in southern South America.

Criteria to assess and select sites for long-term avian monitoring in an urbanizing landscape.

A methodology was developed to prioritize the suitability of sites for long-term monitoring of avian populations, including vulnerable species, both to enhance assessment of changes in ecological resources and to facilitate land-use planning at the regional scale. This paper argues that a successful monitoring program begins with a site prioritization procedure that integrates scores based on spatial controls with ecological and socio-economic indicators, particularly those dependent on community involvement. The evaluation strategy in this study combines 1) spatial controls such as land ownership and accessibility, with 2) biological and habitat indicators such as vulnerable species and habitat connectivity, and 3) community and agency variables such as volunteer commitment and agency priorities. In total, a set of ten indicators was identified. This strategy was applied to predominantly agricultural landscapes, which are experiencing increasing human pressures, in three sub-watersheds of the Credit River, Southern Ontario. Specifically, bird populations were recorded during the breeding seasons of 2000-2002 in nine land units or habitat types including marsh, deciduous forest, and grasslands as mapped by Credit Valley Conservation (CVC) following Ecological Land Classification (ELC) guidelines. CVC selected sites for long-term monitoring in 2002 and the relationships between the scored (or ranked) sites and the selected long-term monitoring sites are discussed.

Influence of weather extremes on the water levels of glaciated prairie wetlands

Abstract Orchid Meadows is a long-term wetland research and monitoring site on the Coteau des Prairie in extreme east-central South Dakota, USA. It is a 65-ha Waterfowl Production Area with numerous temporary, seasonal, and semi-permanent wetlands. Ground water and surface water have been monitored at the site from 1987 to 1989 and from 1993 to the present. Vegetation has been monitored since 1993. The monitoring record includes two nearly back-to-back weather extremes: a drought in the late 1980s and a deluge in the early- to mid-1990s. Wetlands differed sharply in water levels between 3-yr dry and wet periods. For example, the time of inundation ranged among semi-permanent wetlands from 13 to 71 percent during the dry years to 100 percent during the wet years, while for seasonal wetlands, it was 0–29 percent and 46–100 percent, respectively, during dry and wet periods. Temporary wetlands had no surface water during the dry period but had standing water 0–67 percent of the time during the deluge years. T...

Soil monitoring in Germany

Background Aim and Scope Soil monitoring in Germany should register the current soil condition, monitor its changes and provide a forecast for future development. In order to achieve these goals, the long-term soil monitoring sites in Germany (BDF -Bodendauerbeobachtungsflachen) have been established by the federal states. This has been done according to criteria worked out by soil monitoring experts. In this article a method for the examination of the suitability of Germany’s soil monitoring sites for soil conservation and protection purposes, as well as for environmental monitoring and reporting, is introduced. This method includes the landscape representativity of soil monitoring sites as well as the comparability and spatial validity of collected data.

The influence of O 3, NO 2 and SO 2 on growth of Picea abies and Fagus sylvatica in the Carpathian Mountains

At 17 long-term pollution monitoring sites throughout the Carpathian Mountains, tree growth patterns and variation in growth rate were examined to determine relationship of tree growth to specific pollutants. Canopy dominant Picea abies and Fagus sylvatica were selected at each site. Basal area increment (BAI) values were calculated from raw ring widths and used as an estimate of tree growth. Across all sites, BAI chronologies were highly variable, therefore local conditions and forest structure accounted for considerable variation. Several significant relationships, however, implicated a role of pollutants on tree growth. Average levels (1997–1999) of NO 2 and SO 2 were inversely related to BAI means (1989–1999). Although average O 3 alone was not related to growth, the maximum O 3 value reported at the sites was negatively correlated with overall growth. A variable representing the combined effect of O 3, NO 2 and SO 2 was negatively correlated with both P. abies and F. sylvatica growth. Pollution data were used to categorize all sites into ‘high’ or ‘low’ pollution sites. Difference chronologies based on these categories indicated trends of decline in the ‘high’ pollution sites relative to ‘low’ pollution site. In the more heavily polluted sites, the BAI of Fagus sylvatica has declined approximately 50% and Picea abies has declined 20% over the past 45 years.

Native woodland expansion: soil chemical and microbiological indicators of change

The regeneration of native pine woodlands, a habitat of high biodiversity value, is being actively encouraged by conservation agencies as a positive future change in land use. A field study was carried out at Abernethy Forest, Scotland by sampling soil along three parallel transects running from open moorland, through an intermediate zone showing tree seedling colonization, into mature native pinewood forest with the aim of establishing a long-term monitoring site and providing baseline data. The specific objectives were to determine, first, which physical, chemical or microbiological properties in moorland soils would be affected by tree colonization and, secondly, what might be the implications of forest expansion on the soil carbon balance. Moving from moorland to forest, moisture and soil acidity decreased significantly and paralleled vegetation changes but there was little change in %C or %N. Microbial biomass, measured as the total carbon in the soil microflora, decreased markedly towards the forest while the metabolic quotient, a relative measure of microbial activity, showed a significant increase. None of the chemical or microbial indicators were able to detect changes due to seedling colonization at their present stage of development. However, microbial indicators appeared to be more sensitive than physico-chemical properties to the aboveground vegetation. Both the microbial biomass C and the metabolic quotient are likely to be good indicators of change as colonization develops. Estimation of the total sequestered soil carbon indicated more in the moorland (524 t C ha −1) than in the forest (288 t C ha −1), but this did not include the modest aboveground carbon stored in the tree biomass. At this particular site, forest expansion may result in some loss of soil C that would be partly offset by increases in aboveground C.

Recovery from acidification in European surface waters

Abstract. Water quality data for 56 long-term monitoring sites in eight European countries are used to assess freshwater responses to reductions in acid deposition at a large spatial scale. In a consistent analysis of trends from 1980 onwards, the majority of surface waters (38 of 56) showed significant (p ≤0.05) decreasing trends in pollution-derived sulphate. Only two sites showed a significant increase. Nitrate, on the other hand, had a much weaker and more varied pattern, with no significant trend at 35 of 56 sites, decreases at some sites in Scandinavia and Central Europe, and increases at some sites in Italy and the UK. The general reduction in surface water acid anion concentrations has led to increases in acid neutralising capacity (significant at 27 of 56 sites) but has also been offset in part by decreases in base cations, particularly calcium (significant at 26 of 56 sites), indicating that much of the improvement in runoff quality to date has been the result of decreasing ionic strength. Increases in acid neutralising capacity have been accompanied by increases in pH and decreases in aluminium, although fewer trends were significant (pH 19 of 56, aluminium 13 of 53). Increases in pH appear to have been limited in some areas by rising concentrations of organic acids. Within a general trend towards recovery, some inter-regional variation is evident, with recovery strongest in the Czech Republic and Slovakia, moderate in Scandinavia and the United Kingdom, and apparently weakest in Germany. Keywords: acidification, recovery, European trends, sulphate, nitrate, acid neutralising capacity