Long-Term Ecological Research

Ecosystems are dynamic entities. Triggered by external and internal factors, ecosystems change on a multitude of spatial and temporal scales. Nevertheless, in the past, the analysis of ecosystem dynamics has had top priority with reference to short time spans. The exploration of ecological interrelations usually has been carried out within a time period of 3 years, due to the typical funding and qualification duration of environmental research projects. As a consequence, to a great extent, the impacts of changes in the long-term have been neglected. This tendency has provoked a lack of information and methodological know how in this area. That strategy of course is not consistent with the long-term, precautionary way of thinking and acting expressed in political manifestations like the 2010 biodiversity target of the CBD or the EU Habitats Directive, which is an essential component of the sustainability principle. Additionally, real life has demonstrated the general significance of long-term processes: global climate change with its multiple consequences has fostered the awareness that there is an essential lack of scientific knowledge to build the ground for answers to the urgent long-term problems of mankind and the biosphere per se arising from these issues.

Long-term ecological studies are required to understand ecosystem complexity, to develop integrated dynamic models, and to explore appropriate measures for the assessment and control of ecosystem behaviour. The knowledge derived from long-term ecological studies should be a prerequisite to formulate ecosystem management plans, i.e. with reference to recent environmental processes. Long-term problems are especially interesting elements of ecosystem theory. Many hypotheses only can be tested for validity from a long-term aspect, and many generalized ideas about ecosystem development could not be verified satisfactory up to now due to a lack of long-term data sets. In this introductory statement chapter, some theoretical aspects of ecosystem dynamics are sketched. These outlines are used to derive demands and questions from ecosystem theory towards long-term ecological studies. The queries are posed referring to six main objectives of long-term research: (i) understanding large-scale variabilities, (ii) understanding the interactions of short-term and long-term fluctuations, (iii) understanding self-organization, (iv) understanding rare events and disturbances, (v) better understanding the impacts of anthropogenic use of landscape resources on ecosystem functions, and (vi) generation of knowledge and data for the development and evaluation of new generations of ecosystem models for resource management. These items can be taken to demonstrate the enormous research demands referring to long-term environmental dynamics and to develop and apply techniques of ecological statistics, data management, and ecosystem modelling.

The question of ecosystem dynamics is important because when studying ecosystems, particularly over the long term, one must expect that natural endogenous changes will occur. In other words, observed changes may not be solely reflective of human-induced or other exogenous perturbations, but rather represent the natural long-term dynamic which the system experiences. Therefore, ecosystem management must account for these expectations, such that the goal might not be to preserve a system in its current state, but to allow the range of natural dynamics to occur, to allow the system to follow its self-organizing trajectory. The challenge for ecosystem theory and long-term ecological research is to identify this trajectory or direction in which ecosystems change. We can for instance look at some of the main system characteristics such as species composition, functional integrity, or biodiversity, and also look at changes in the thermodynamic patterns of organization in the ecosystem. In this chapter, we review some of the standard concepts on ecosystem growth and development and discuss the use of holistic orientors and indicators as a means to understand long-term ecosystem dynamics. We also try to demonstrate some respective linkages for the analysis of human–environmental systems and derive some suggestions for environmental management.

Over time environmental monitoring has produced an immense amount of data that was collected in order to assess environmental pollution impacts but also for ecological research. Although this research produced revelatory, valuable data and information on the structures and functions of ecosystems, amazingly few studies have focussed on the theoretical aspects of ecosystem evolution. This obviously is counter to the progress in the field of ecosystem theory and the provision of integrated concepts in relation to indicators of ecosystem performance. In this regard, the major intention and challenge of LTER (Long-Term Ecosystem Research) is to combine the theoretical background with the ecological knowledge already available in order to extrapolate monitoring information about environmental problems and to find solutions in line with recent progress at the global scale. With a view of ecosystem evolution in a long-term perspective and to support applied ecology with respective monitoring information, special methodical diligence has to be lenient towards temporal and spatial extrapolations. This focuses on problems of representativity and reference. The aim of this chapter is to inform the reader how information on ecosystems can be derived and the potentials and limitations of using available databases from monitoring in networks and results produced by integrated data evaluations in ecosystem research. Ideas on further optimisation of monitoring activities are also presented. Two environmental initiatives are presented as case studies including protection of forest ecosystems against the effects of atmospheric deposition (ICP-forests) and the definition of properties that define a good ecological state of aquatic ecosystems (European Water Directive); critical load indications and success control measures are respectively used and the benefits to environmental protection are discussed.

The U.S. Long Term Ecological Research (US-LTER) program consists of 26 research sites involving a wide range of ecosystem types and concentrates on the interactions of multiple ecosystem processes that play out at time scales spanning decades to centuries. Long-term data sets from programs such as US-LTER provide a context to evaluate the pace of ecological change, to interpret its effects, and to forecast the range of future biological responses to change.

The primary challenges for LTER type research during its history involved sustaining funding, partnership development to sustain growth, maintaining continuity in objectives, and linking scientists and data through communication and cooperation. These challenges have been successfully addressed over the decades of the US-LTER program through close cooperation and coordination of the scientific community and the funding agencies for these programs.

The scientific community benefits much from working with colleagues around the world that have other experiences, social cultures, and knowledge bases. Ultimately, the mission of LTER and the International LTER Network is to incorporate understanding of the role of humans in the environment to inform policy makers and translate understanding into action.

LTER-Europe is the umbrella network for Long-Term Ecosystem Research (LTER) and Long-Term Socio-Ecological Research (LTSER) in Europe. It forms part of the global LTER network (ILTER). Comprising 18 formal national member networks and five emerging ones LTER-Europe represents more than 400 LTER sites and 23 LTSER platforms. Besides this in-situ component LTER-Europe stands for a network of scientists, disciplines, institutions, data and metadata, and research projects. The Network of Excellence ALTER-Net (FP6) provided the frame for meeting the objective to integrate the highly fragmented European infrastructure with LTER potential across national and disciplinary boarders. LTER-Europe has become the terrestrial and aquatic component in the network of networks, currently organised by the ESFRI preparatory project LifeWatch. The interdisciplinary expertise represented by the ALTER-Net consortium allowed further development of the LTSER concept. LTSER platforms have been developed as multi-scale and multi-level infrastructure for investigating interactions of human and natural systems on the regional or sub-regional level. These hot spots of interdisciplinary research (IDR) and data sets are now complementing the first pillar of LTER-Europe’s network, the network of LTER sites. The character and functional niche of LTER-Europe is best described by four core characteristics, namely “in-situ, long-term, system and process”: LTER-Europe’s research is generating or using data gathered together with a maximum of other sources of knowledge at concrete locations in the long term. This allows for the detection and quantification of processes of ecosystems and socio-ecological systems, which determine the sustainable provision of ecosystem services. Summarising, LTER-Europe is a multi-functional network, but also a process structuring and optimising a distributed research infrastructure, catalysing the development of research projects meeting societal needs and helping to streamline and harmonise the entire sector on the institutional, national, European and global level.

Analysis, control, and management of ecosystems are complex tasks which have to cover broad ranges of operating environmental states and decision making. Current approaches to ecosystems modelling and simulation are mostly based on information theory, thermodynamics, topology, or balances of biological and chemical components. Ecosystems are considered from the point of view of information theory as complex dynamic communication networks with living and non-living components and their interrelationships. State space approaches are used for ecosystem management. But these models give no answer to structural ecosystem changes. The relational ecology approach covers more the structural problems of ecosystem modelling. The relationships are given qualitatively but cannot be quantified easily. The network approach seems to be the most appropriate approach to include behavioural and structural changes of ecosystems in models.

Sustainable management of natural resources requires a good understanding of ecosystems components and their interrelationships. Statistics is essential for understanding the structure and behaviour of ecological processes and provides the basis of predictive modelling. Mostly, physical, chemical, and biological variables are recorded across time and space. They serve as indicators, giving information concerning the state and changes of ecosystems. Most of monitored ecological indicators are non-stationary in time structure. The classical static statistical methods revealed the presence of trends and long memories in these data sets. On the other hand, modern dynamic statistical methods indicate the presence of long-term cycling processes. The Fourier polynomial is a technique for approximating periodic functions by sums of cosine and sine periodic functions, shifted and scaled. Therefore, it may be suitable for approximating cycling processes with a fixed frequency as portrayed by some ecological indicators. Wavelet analysis can be used to investigate the timescale behaviour of ecological processes. This analysis reveals the long-term evolution of an ecological indicator at different resolutions, the dominant scale of variability in the data set, and its correlation and cross-correlation with other ecological indicators on a scale by scale basis.

All Long-Term Ecological Research (LTER) asks for spatially explicit information. Remote sensing-based data and related analysis products are major sources of such information. This chapter expands on general concepts of remote sensing and most important methodologies in relation to LTER. Examples from US-LTER sites exemplify opportunities related to remote sensing.

The Wadden Sea is a shallow coastal region in the south eastern North Sea. Karl Möbius started ecological research in the northern Wadden Sea about 150 years ago studying the extensive oyster beds. With the foundation of a field station of the Biologische Anstalt Helgoland in List/Sylt in 1924 biological research in the Wadden Sea was continued to date. Several time series were initiated between the 1970s and the 1990s including a bi-weekly phytoplankton and zooplankton program and an observation program on macrobenthos. Three factors dominating the changes observed during the past decades are a rise in temperature, decreasing nutrients, and increasing invasions of non-native species. Phytoplankton blooms gradually decrease due to the combined effect of decreasing nutrient loads and increasing winter temperatures. Mean annual zooplankton abundance is stimulated by higher winter temperatures. Recently, invading species are increasingly dominating native mussel beds. For several invaders, a positive effect of temperature was shown. We expect that major pressures of change during the next years will be further species introductions, temperature increase, and reduced nutrient loads. On the long run (21st century), we expect sea level rise to be the key factor of coastal change through a loss of habitats with fine-grained sediments and intertidal sediments in general. A major challenge for coastal research will be to disentangle the interactive effects of these pressures on the long-term development of the Wadden Sea.

A case study is presented to demonstrate the added value which can be gained from combining long-term biological observations with model-based hind casts of physical environmental conditions. The study utilizes numerically simulated high-resolution fields of currents and water levels in the North Sea to investigate the relevance of hydrodynamic conditions for the occurrence of phytoplankton blooms, as observed at Helgoland Roads in the inner German Bight. Inter-annual variations as well as a possible regime shift are discussed with regard to the spring mean diatom day. The long-term high-resolution simulations of the North Sea circulation are taken from the data base ‘coastDat’.

Variability and complexity in brackish systems require long-term measurements in order to define base conditions, from which deviations can be ascertained. Long-term observations in three systems, lagoons, the Baltic Sea, and the Chesapeake Bay, are examined to identify system changes, unlikely detectable with sampling in single years or in temporally and spatially heterogeneous sampling. One basic condition in brackish systems is the gradient in salinity, which may be large-scale and rather stable stretching over the entire sea (marine gradient), or meso-scale and highly variable such as those in river plumes (estuarine gradient), and upwelling cells (upwelling gradient). For the first two gradients, and in some cases the third, distinct boundaries separate stenohaline taxa from more eurytopic taxa resulting in spatially explicit distributions of plankton, nutrients, and food web characteristics. The natural variability has to be ascertained through repeated long-term sampling in order to fix a baseline for shifts and trends in the ecosystem. A general trend during the last decades is cultural eutrophication, leading to increased phytoplankton biomass and sedimentation, and hypoxia in bottom water. In some areas, eutrophication was repressed in the 1990s, e.g., stabilization of chlorophyll concentrations in the Baltic Proper, recovery of macrophytes in the Darss-Zingst Bodden Chain (DZBC). In the coming years, the effects of declining nutrient loads are expected to cause a return to mesotrophic conditions in the DZBC, resulting in a return of nutrient limitation. Further monitoring will be performed to follow this unique event. It is therefore imperative that the community support long-term observations in these complex systems particularly as increasing human populations exacerbate impacts of global climate change that slowly warms waters, changes intensities and frequencies of meteorological events and responsive hydrologies, and shifts biogeographic ranges of many cosmopolitan taxa.

Long-term changes of freshwater ecosystems are mainly caused by immissions from drainage basin and atmosphere (nutrients, acid substances, etc.) and by changing climatic conditions. Freshwater ecosystems often react in non-linear ways to these external forces. Beyond a certain threshold, gradual shifts may cause catastrophic switches to another state. The way back to the previous state rarely corresponds to the past changes because of memory effects of the system. Long-term studies are necessary, but they do not allow for a simple extrapolation of past observations into the future.

Freshwater systems are also influenced by rare events like invasion of new species, spates or droughts. Effects of perturbations should be studied until the system establishes a new equilibrium.

The analysis of long-term processes needs sound knowledge about natural oscillations or gradual changes of the baseline. Monitoring programmes of German lakes and reservoirs rarely last longer than 30 years. They usually started after serious environmental problems had emerged; they do not cover periods without human impacts (baseline conditions). Therefore, long-term monitoring should be accompanied and extended by palaeolimnological approaches.

Since 1970 long-term ecological research has been established in several running waters in Bavaria. An emphasis was laid on the record of the macrophytic vegetation. In this chapter we present long-term records from three rivers. The Moosach is situated in the calcareous-rich gravel plains north of Munich. The two soft-water rivers, the Pfreimd and the adjacent Naab, run out from the siliceous bedrock of the ‘Upper Palatinate Forest.’ Vegetation changes could be interpreted according to water quality changes and confirmed the suitability of macrophytes as water quality indicators, which recently obtained its official acceptance in the new Water Frame Directive of the European Union. The results show that there is a unification of the vegetation losing the extremes especially in the oligotrophic part. However, the regeneration potential of macrophytes is mainly low although in many species it is not yet understood. It is therefore concluded to lay an emphasis on the protection of still oligotrophic sections of a river to maintain the total species pool.

General problems connected with planning, sampling, and data processing of long-term research of soil mesofauna are discussed, based on two case studies: (i) the Bremen study of predatory mites (Gamasina) covering 20 years of secondary succession on a ruderal site in northern Germany and (ii) the Mazsalaca study of the effects of climate warming on Collembola of coniferous stands in the North Vidzeme Biosphere Reserve, Latvia, covering 11 years. The findings from both sites are embedded in an array of environmental data. The results from Bremen document the asynchrony of different biota in successional dynamics. The long-lasting increase of the species numbers of soil predatory mites (Gamasina) is contrasted by a decrease in plant species numbers. In the Baltic forests, climate change is indicated by the dynamics of collembolan community. Gradual decline in species richness has been observed from 1992 to 2002 attributed to global warming. The ‘temporal window’ or time unit to discern changes in soil mesofauna communities seems to span approx. 5 years, highlighting the necessity of long-term observations.

Since the 1980s a variety of biogeochemical catchment studies have been set up to investigate the cycling of water and solutes. Groundwater and streams have been sampled to investigate the dominant processes of solute turnover in the subsoil and to monitor their long-term changes. Usually a variety of processes interact partly in a highly non-linear manner. Consequently, identifying the dominant processes is not an easy task. In this study, a non-linear variant of the principal component analysis was used to identify the dominant processes in groundwater and streamwater of two forested catchments in the East Bavarian–West Bohemian crystalline basement. The catchments are approximately 60 km apart, but exhibit similar bedrock, soils, climate, land use, and atmospheric deposition history. Both have been monitored since the end of the 1980s until today, that is, during a period of dramatic decrease of atmospheric deposition of sulfur and accompanying base cations. Time series of component scores at different sites were investigated. Non-linear long-term trends were determined using a low-pass filter based on a Lomb–Scargle spectrum analysis.

The first four components accounted for 94% of the variance of the data set. The component scores could be interpreted as quantitative measures of biogeochemical processes. Among these, redox processes played a dominant role even in apparently oxic parts of the aquifers. Low-pass filtered time series of the component scores showed consistent, although mostly, non-linear trends in both catchments.

Long-term soil hydrological measurements were used to quantify deep seepage and nitrate leaching in situ under undisturbed soil conditions. Deep seepage rates and nitrate losses from arable land managed under various farming regimes (integrated, integrated with irrigation, ecologic and low input) and tillage systems (plough and no-till) were quantified in the Pleistocene region of Northeast Germany from 1994 to 2005. Soil water content and tension measurements down to 3 m depth and soil water sampling were used to determine deep seepage dynamics and loss of nitrogen by leaching. As dependent on the management system, the nitrate concentration varied between 40 and 150 mg l⁻¹. In connection with annual deep seepage rates between 100 and 200 mm during the study period, the annual nitrogen loss varied between 14 and 41 kg ha⁻¹. Differences in nitrogen loss observed between the farming systems were low, but yields increased and nitrogen losses decreased as a result of irrigation throughout the variants. No-till treatment resulted in reduced nitrate leaching (18 kg ha⁻¹) as compared with the tillage system with plough and tooth cultivator (27 kg ha⁻¹). The method of quantifying deep seepage rates based on soil hydrological measurements was tested in comparison with lysimeter discharge measurements. Willmott’s index of agreement was d = 0.97 revealing the validity of this simplified approach. Results underline the hypothesis of the well balanced, slow and continuous progression of the soil water content below the root zone. The suitability of long-term soil hydrological in situ measurements for quantifying arable management effects on ecological processes – deep seepage dynamics and solute leaching – was confirmed.

In Central Europe, damage of forests has been clearly identified to be caused by atmospheric deposition of acidifying air pollutants and eutrophicating amounts of nitrogen. The rapidly growing public concern about this phenomenon induced numerous studies particularly in Germany already in the 1970s and 1980s, which produced an impressive number of pertinent botanical, parasitological, pedological and geographical information. In general, however, focus was on specific aspects of forest decline, which not infrequently led to monocausal explanations.

The concept of the interdisciplinary and transdisciplinary Bornhöved ecosystem research programme reflects basic principles of scientifically based programmes of environmental observation. The general aim of the Bornhöved Project was to study ecosystem structure and evolution in a highly complex landscape of the North German Plain. Twenty years of high-resolution time-series of pertinent meteorological, hydrological, biological and pedological data on the energy and material fluxes of the Bornhöved beech stands are available for both monitoring purposes and as a basis for ecosystem theory building. Atmospheric deposition and element behaviour in the soil solution exhibit distinct trends and periodicities in biogeochemical transfer processes in relation to the water use of the ecosystems. Efficiency measures such as the transpiration/evapotranspiration ratio, element fluxes or budgets and the stoichiometric definition of elemental imbalances have proved to be commendable indicators.

Landscape monitoring is highly topical as we are faced again and again with challenges in the balance of nature and its utilisation. Knowing of this importance for the European Landscape Convention calls to support the landscape analyses for which suitable methods of international scale have to be developed. Landscape-related monitoring means, according to the authors, a trans-scale spatially nested and complex monitoring and evaluation of landscape change. Suitable methods were developed for the purpose and presented. The framework introduced has been tested successfully in three federal states of Germany since 1999 and may now be defined as being mature for application. As drawn up there are hypotheses, functions, indicators, and data to adapt to the spatial conception and the given conditions. The implementation of the various natural science and social science programmes which would require a high degree of compatibility for reason of their integrative properties represents a problem. They have to be implemented for entire project periods lasting for decades and implemented in continuous monitoring, the methodical consistency has to be assured, and a professional interpretation even of heterogeneous data and a reasonable, model-based forecast of the change of landscape have to be given.

Intensification of agricultural land use during the last century, combined with an increasing level of agrochemicals, has resulted in a decline of both habitat diversity and quality and to simplification and homogenization of Central Europe landscapes. For three agricultural landscapes in Central Germany we investigated (1) the influence of historical and current land-use and landscape structure on plant species diversity patterns in semi-natural habitats as well as on arable fields and (2) the extent to which genetic variation within populations (H _e) of the common forest herb Geum urbanum is related to population properties and to present landscape structure. Historical and present floristic field data were analysed in relation to land-use and landscape structure characteristics of the same periods (1950s, 1970s and 2000/2002). Changes in plant species richness and composition during the past 50 years varied among landscapes according to their land-use history and environmental characteristics, but were mostly in favour of ruderal species. Plant species richness for semi-natural habitats was negatively affected by increases in mean patch size of meadows and by increases in phosphorus application. Moreover, the application of mineral fertilizer, especially phosphorus, led to many habitat specialists being replaced by generalist species. Species richness of ‘arable weeds’ was significantly affected at both landscape and regional level by the proportion of semi-natural habitats, habitat diversity and habitat isolation due to landscape homogenization. More intensive land use, and particularly increased nitrogen application, was associated with decreased richness of ‘arable weeds’.

The landscape genetic approach was extended to the same three landscapes and thus landscape-specific patterns could be disentangled from general relationships consistent across landscapes. Genetic variation of 70 populations was determined at eight microsatellite loci. Landscape structure was assessed in circular areas around populations and related to genetic variation within populations (H _e) by linear mixed-effects models. H _e was affected in an inverse manner by the size of Geum populations, by average patch size, by land-use diversity, by the area of woody habitat and by the area of roads. The study underlines the importance of habitat area and isolation as factors affecting genetic diversity, with both factors varying in a landscape-specific way.

These results suggest that regional and historical processes, as well as local environmental factors, influence local plant community and population structure. Therefore, long-term studies are of high importance to understand ecological processes. We conclude that for conserving biodiversity in agricultural landscapes it is as important to protect existing, historically developed habitat diversity as the protection of habitat quality.

In Germany, environmental monitoring data are collected at different locations and in different environmental components by several federal monitoring networks. According to the scientific and legal demands, these data should be made available by integrating them into a web-based geographical information system (WebGIS) and described by harmonised metadata. This enables a spatial and temporal assessment of long-term environmental impacts induced by climate change, for example, as being one issue of the holistic approach, achievable through research strategies of the ILTER (International Long-Term Ecological Research). This chapter on hand describes a WebGIS that was implemented by using Open Source software and filled with geodata and metadata on relevant long-term environmental networks in Germany (LTER-D). The latter were gathered by using an online questionnaire being answered for a total of nine different monitoring networks describing atmosphere, soils, groundwater, biota and marine ecosystems at around 300 monitoring sites. The questionnaire and the WebGIS itself were implemented by using Open Source software, solely. Feasibility and surplus of the WebGIS were demonstrated by investigating the spatiotemporal trends of the metal bioaccumulation in Germany’s ecoregions. The technological framework implemented for gathering and linking of environmental data from different monitoring networks proved to be an adequate and effective tool for an integrated investigation of long-term environmental changes. Hence, efforts should be improved to promote long-term ecosystem research in the LTER-D community and to accelerate integration of monitoring data and results into European and global long-term monitoring programmes.

In the broad field of monitoring, this chapter highlights two specific approaches: long-term ecosystem observation and success control. Different target settings in nature protection determine very strictly the concrete monitoring programmes as demonstrated by two topical examples. As the first example, the ‘Long-term observation of ecosystems in the biosphere reserves of Brandenburg’ is operating for more than 10 years now. It comprises a broad variety of areas while observing all components relevant to the respective ecosystem. The fundamental approach of this concept is introduced. Criteria used for the definition of ecosystem types in combination with utilization forms and for the selection of observation areas are described. A closer look at the aims and programmes of fens exemplifies the approach of the project. In order to outline the differences between long-term observations and success control, the second example depicts a success control programme for the rewetting of peatlands in forests.

National parks are protected areas that have been excluded from human intervention and exploitation in order to safeguard the species inventory and natural processes in a way as ‘true to nature as possible’. As permanently protected ecosystems in a process of near-natural development, national parks serve as extremely attractive control areas for ecosystem research and, especially, for scientific, long-term monitoring. In the midst of Europe, in a landscape that has been utilised for millennia, the existence of extensive protected areas can provide answers to an abundance of basic questions that cover an enormously wide variety of themes.

National park research has several functions such as to develop the scientific foundation for the implementation of national park goals; monitor the efficiency of national park management; research the undisturbed development of the biocenoses; study the socio-economic and socio-ecological relationships between the national park, its visitors, and its periphery; and determine anthropogenic influences and their effects on the ecological communities.

Environmental monitoring in its broadest sense aims at determining the quality and extent of human influence on the environment and to record long-term changes (Kellermann & Riethmüller, 1998). It can provide a basis for political actions; however, the influence of monitoring on political decisions has been controversial (see, e.g., de Jong, 2006).

Using the protection of the National Park Schleswig-Holstein Wadden Sea as a best practice example, this chapter shows the strength of long-term monitoring data as a solid basis for conservation concepts. Along with an efficient organisational structure – i.e. in the frame of the trilateral cooperation between the Netherlands, Denmark and Germany for the protection of the Wadden Sea as a whole – monitoring is able to influence or even induce political decisions. A number of achievements of the trilateral cooperation are presented. Future challenges, which will arise from the implementation of EU directives and international conventions like the Convention on Biological Diversity (CBD), are discussed with a focus on the role of monitoring data within such processes.

Multi-scaled ecological monitoring networks offer significant potential to address a wide range of challenging environmental problems. Knowledge gained through these networks will be critical in understanding, detecting, and forecasting ecological changes that affect important ecological services upon which society depends. The networks will provide information necessary for societies to adapt to broad-scale changes such as those associated with land use, demographic, and climate change. Several new multi-tiered monitoring programs are being developed to evaluate ecological changes and associated drivers of change at a range of spatial and temporal scales. Additionally, existing ecological monitoring programs, such as the Long-Term Ecological Research (LTER) program, are attempting to improve their capacities to extrapolate results to larger spatial extents by developing a standard set of measures or indicators and by facilitating cooperation among scientists within and among the various monitoring networks. Despite these attempts, several issues remain in integrating existing monitoring programs. We discuss these issues and review existing programs within a multi-tiered monitoring framework that explicitly incorporates citizen-based monitoring. Direct involvement of the public is seen as a critical element in expanding and maintaining existing and new ecological monitoring networks. We provide examples of two emerging ecological monitoring networks, the Terrestrial Observatory Network (TERENO) and the USA National Phenology Network (USA-NPN), to convey some of the complexities and challenges confronting the design and implementation of multi-tiered ecological monitoring networks.

In order to support the emerging network of long-term ecological research (LTER) sites across Europe, the European Union has launched ALTER-Net, a network aiming at lasting integration of long-term socio-economic, ecological and biodiversity research. Due to its high population density and long history of human habitation, however, Europe’s ecosystems are generally intensively used. Social and natural drivers are so inextricably intertwined that the notion of ‘socio-ecological’ systems is appropriate. Traditional natural science-based approaches are insufficient to understand these integrated systems, as they cannot adequately capture their relevant socio-economic dimensions. This is particularly relevant because the EU launched ALTER-Net has an explicit aim to support sustainability, a goal that requires integration of socio-economic and ecological dimensions. As such, LTER is challenged to significantly expand its focus from ecological to socio-ecological systems, thus transforming itself from LTER to long-term socio-ecological research or LTSER. In order to support this transformation, this chapter explores several approaches for conceptualising socio-economic dimensions of LTSER. It discusses how the socio-economic metabolism approach can be combined with theories of complex adaptive systems to generate heuristic models of society–nature interaction which can then be used to integrate concepts from the social sciences. In particular, the chapter discusses possible contributions from the fields of ecological anthropology and ecological economics and shows how participatory approaches can be integrated with innovative agent-based modelling concepts to arrive at an integrated representation of socio-ecological systems that can help to support local communities to move towards sustainability.

In Europe and North America, long-term ecological research (LTER) networks are changing their treatment of human activity from exogenous ‘disturbances’ to endogenous behaviour. The engagement of social scientists in LTER networks currently takes forms ranging from nonexistent, to research in parallel with ecological research but with minimal interaction, to truly collaborative long-term socio-ecological research (LTSER). Successful collaboration of social and ecological scientists can be facilitated by a ‘jazz band’ approach that allows shifting multidisciplinary leadership along with disciplinary research solos. Socio-ecological simulation modelling can serve as a common tool for analysing complex dynamics of the interacting systems. The design criteria for an LTSER network should include socio-economic as well as ecological factors in order to ensure that findings can be extrapolated in both dimensions, an approach currently being followed in Europe. However, due to evolving societal needs, socio-ecological research should also be occurring outside the network of LTSER sites. New governmental initiatives on both sides of the Atlantic have the potential to enable more and better socio-ecological research than in the past.

Ecosystems are affected by anthopogenic activities at a global level and, thus, are manipulated world-wide. This chapter addresses the impacts of apparent and non-apparent manipulations and restoration by human activities in Europe with a focus on the temperate zone. Agricultural management practices induced evident site-specific modification of natural ecosystem structures and functions whereas forests and natural grasslands and also aquatic systems are considered as being less manipulated. Ecosystems such as mires, northern wetlands and the tundra, have received attention due to their vulnerability for conserving carbon and biodiversity and for identifying the role of non-apparent manipulations on ecosystem functioning. Drastic types of ecosystem manipulation include open-cast mining activities that occur worldwide and induce perturbation of large areas across landscapes. Such harsh human impacts create the need for remediation and restoration measures for mining regions that address classical food and fodder services and also nature conservation and novel social benefits. Recultivation therefore offers the opportunity to introduce new land-use types and to study processes of initial ecosystem development that are still poorly understood.

Current changes in biodiversity and their functional consequences for ecosystem processes matter for both fundamental and applied reasons. In most places the most important anthropogenic determinant of biodiversity is land use. The effects of type and intensity of land use are modulated by climate and atmospheric change, nutrient deposition and pollution and by feedback effects of changed biological processes. However, it is not known whether the genetic and species diversity of different taxa responds to land-use change in similar ways. Moreover, consequences of changing diversity for ecosystem processes have almost exclusively been studied in model experiments of limited scope. Clearly, there is an urgent scientific and societal demand to investigate the relationships between land use, biodiversity and ecosystem processes in many replicate study sites in the context of actual landscapes. Furthermore, these studies need to be set up in long-term frameworks. Moreover, because monitoring and comparative observation cannot unravel causal mechanisms they need to be complemented by manipulative experiments. In the ‘Exploratories for large-scale and long-term functional biodiversity research’ (see http://​www.​biodiversity-exploratories.​de), we provide a platform for such successful long-term biodiversity research. The biodiversity exploratories aim at contributing to a better understanding of causal relationships affecting diversity patterns and their change, developing applied measures in order to mitigate loss of diversity and functionality, integrating a strong research community to its full potential, training a new generation of biodiversity explorers, extending the integrated view of functional biodiversity research to society and stimulating long-term ecological research in Germany and globally. Our experience has several implications for long-term ecological research and the LTER network including the necessity of formulating common research questions, establishing a joint database, applying modern tools for meta-analysis or quantitative review and developing standardised experimental and measurement protocols for facilitating future data synthesis.

Long-Term Ecosystem Research has been successfully carried out for some decades now, but networking, tuning, and harmonization at least in Europe have just started. Several developmental targets have been obtained and very interesting results have been achieved. Regrettably, these milestones have been reached in a few regional cases only, and, i.e., due to the relatively short-term existence of long-term environmental investigations on the global scale, many urgent questions – with existential problems of mankind among them – could not be answered up to now. In spite of the comprehensive demands for future research including the global scale, some of the key queries may be discussed constructively. Therefore, as an attempt to summarize the complex information of the previous papers, we might refer to the questions which have been asked in the introduction of the book.