Boudewijn Beltman

Wetlands: Functioning, Biodiversity Conservation, and Restoration

1 Introduction: Wetland Functioning in Relation to Biodiversity Conservation and Restoration R. Bobbink, D.F. Whigham, B. Beltman, and J.T.A. Verhoeven Section I: Functioning of Plants and Animals in Wetlands. 2 Plant Survival in Wet Environments: Resilience and Escape Mediated by Shoot Systems M.B. Jackson 2.1 Introduction 2.2 How Excess Water Threatens Plant Life 2.2.1 Excluding and Trapping Effects of Water 2.2.3 The Energy Crisis 2.3 Resilience 2.3.1 Oxygen Shortage 2.3.2 Shortage of Carbon Dioxide 2.4 Escape 2.4.1 Aerobic Shoot Extension (the Aerobic Escape) 2.4.2 Anaerobic Shoot Extension (the Anaerobic Escape) 2.5 Conclusions and Summary References 3 Center Stage: The Crucial Role of Macrophytes in Regulating Trophic Interactions in Shallow Lake Wetlands R.L. Burks, G. Mulderij, E. Gross, I. Jones, L. Jacobsen, E. Jeppesen, and E. van Donk 3.1 Introduction 3.2 Central Position of Aquatic Vegetation 3.2.1 Central Themes: Zooplankton Depend on Macrophytes as Habitats 3.2.2 Central Themes: Chemical Ecology Spans Trophic Levels 3.2.3 Central Themes: Impacts of Grazer--Epiphyton Interactions with Macrophytes 3.2.4 Central Themes: Prevalance of Fish Influence in Shallow Lakes 3.3 In the Wings: Research Areas Worthy of Attention 3.3.1 Predictability of Macrophyte Function in Trophic Interactions Across a Climatic Gradient 3.3.2 Relative Importance of Chemical Ecology Across Trophic Levels 3.3.3 Disproportional Impacts of Certain Invertebrates and Exotic Species 3.4 Returning to Center Stage: Macrophytes are Common Players in Trophic Interactions References 4 Biological Invasions: Concepts to Understand and Predict a Global Threat G. van der Velde, S. Rajagopal, M. Kuyper-Kollenaar, A.bij de Vaate, D.W. Thieltges, and H.J. MacIsaac 4.1 Introduction 4.2 What is a Biological Invasion? 4.3 Impacts of Biological Invasions 4.3.1 Ecological Impacts 4.3.2 Evolutionary Impacts 4.3.3 Economic Impacts 4.3.4 Human Health Impacts 4.3.5 Measuring Impacts 4.4 Examples of Biological Invasions 4.5 Understanding and Predicting Biological Invasions 4.5.1 Invading Species Approach Propagule Pressure 4.5.2 Invaded Ecosystem Approach 4.5.3 Relationship Between Invader and Invaded Ecosystem (Key-Lock Approach) 4.5.4 Invasion Processes Differentiated in Time 4.5.5 Comparative Historical Approach 4.6 Shadows on the Prospects of Prediction 4.7 Conclusion References Section II: Conservation and management of wetlands 5 Wetland Conservation and Management: Questions for Science and Society in Applying the Ecosystem Approach E. Maltby 5.1 Introduction 5.2 Wetlands at the Interface 5.3 Recognising a New Paradigm in Ecosystem Management 5.4 The Ecosystem Approach 5.4.1 Principle 1: The Management of Land, Water and Living Resources is a Question of Societal Choice 5.4.2 Principle 3: Ecosystem Managers Should Consider the Effects of Their Activities on Adjacent and Other Ecosystems and Principle 7: The Ecosystem Approach Should be Undertaken at the Appropriate Scale 5.4.3 Principle 4: There is a Need to Understand the Ecosystem in an Economic Context 5.4.4 Principle 9: Management must Recognise that Change is Inevitable 5.4.5 Principle 10: The Ecosystem Approach Should Seek the Appropriate Balance Between Conservation and Use of Biological Diversity 5.5 Conclusion References 6 Wetlands in the Tidal Freshwater Zone A. Barendregt, D.F. Whigham, P. Meire, A.H. Baldwin, and S. Van Damme<

PLANT COMMUNITY MEDIATED VS. NUTRITIONAL CONTROLS ON LITTER DECOMPOSITION RATES IN GRASSLANDS

Grasslands are one of the major biomes on earth and can serve as important soil carbon sinks. Nutrient enrichment of these grasslands can have a significant impact on carbon losses through the decomposition process. We investigated the effects of long-term (12-yr) experimentally increased N and/or P supply on litter production and on the chemistry and decomposition of bulk litter from two grasslands differing in soil nutrient status. Potential aboveground litter production in the controls of a P-rich low-productivity riparian grassland was lower than that in a N-rich high-productivity peat grassland and increased with enhanced N supply. Nutrient treatments did not enhance litter production in the high-productivity peat grassland. The concentrations of phenolics in bulk litter from the peat grassland, dominated by sedges, were 2-3 times higher than those in the riparian grassland that was dominated by herbs and grasses. At both sites increased nutrient supply had no detectable effect on phenolics concentrations. All P-related litter chemistry param- eters reflected the higher soil P status of the riparian grassland. P fertilization had a greater effect on litter chemistry in the P-deficient peat grassland than in the P-rich riparian grass- land. At both sites, there was no change in overall litter chemistry in response to N fer- tilization, except for higher lignin concentrations in the peat grassland litter. Both short- term (8 wk) litter incubations in the laboratory and a 3-yr litter bag study in the field showed that riparian grassland litter decomposed faster than litter from the peat grassland. The long-term nutrient additions had no significant effects on the decomposition of the bulk litter of each grassland type. Regression analysis on the combined data of the two sites showed that phenolics, and to a lesser extent, P-related litter chemistry parameters, exerted a strong control on both litter respiration and litter mass loss. Our study shows that long-term experimental nutrient additions do not lead to increased decomposition rates in grasslands and that the initial plant community litter quality is the main determinant of carbon losses through the decomposition process. The results of this study suggest that nutrient enrichment will likely affect ecosystem carbon balance more by affecting litter production than by affecting litter decomposition rates.

Evapotranspiration from fens in relation to Penman's potential free water evaporation (EO) and pan evaporation

Evapotranspiration from three Dutch quaking fens with different vegetation was studied during the growing season of 1986 (April–October). Evapotranspiration from lysimeters filled with peat and vegetation was compared with evaporation from lysimeters filled with water, and with Penmans potential free water evaporation (Eo) determined at a nearby weather station. Evapotranspiration from vegetated lysimeters exceeded evaporation from water-filled lysimeters by a factor of 1.7–1.9 and was 0.7–0.8 times less than Penmans Eo. Although the structure of the vegetation proved to have an influence on evapotranspiration rates, differences among sites in total evapotranspiration over the entire growing season were only small. Thus, a single equation was developed that describes evapotranspiration from fens (E, mm day−1) as a function of Penmans Eo (mm day−1) on a monthly basis: E = 0.73 Eo + 0.16 (r = 0.97). This equation appears to be fairly accurate, except during prolonged periods of high evaporative demand. Though this equation primarily serves the determination of the evapotranspiration term in the water budget of fens in the study area, it may also apply to other peatlands with high water tables in the temperate region.

Flood events overrule fertiliser effects on biomass production and species richness in riverine grasslands

Abstract Question: Do severe winter flood events lift the nutrient limitation of biomass production in a river floodplain? How does this affect plant species richness? How long do the effects last? Location: Floodplain grassland on calcareous sandy loam near river Rhine in The Netherlands. Methods: Plots were fertilised with four treatments (control, N, P, N+P) for 21 years; plant species composition, vegetation biomass and tissue nutrient concentrations were determined every year between 1985 and 2005. Results: Fertilisation with N generally increased biomass production and reduced species richness, but these effects varied over time. During the first four years of the experiment, biomass production appeared to be co-limited by N and P, while N fertilisation dramatically reduced plant species richness; these effects became weaker subsequently. Following two extreme winter floods in 1993–94 and 1994–95 and a drought in spring 1996, the effects of fertilisation disappeared between 1998 and 2001 and then appeared again. Flooding caused an overall reduction in species richness (from c. 24 to 15 species m−2) and an increase in biomass production, which were only partly reversed after ten years. Conclusions: Long time series are necessary to understand vegetation dynamics and nutrient limitation in riverfloodplains, since they are influenced by occasional flood and drought events, whose effects may persist for more than ten years. A future increase in flooding frequency might be detrimental to species richness in floodplain grasslands. Nomenclature: van der Meijden (1996).

Dependency of local mesotrophic fens on a regional groundwater flow system in a poldered river plain in the Netherlands

The effect of regional, subregional and local groundwater flow systems on mesotrophic fen ecosystems was studied in the polders of the Vecht River plain that borders the Pleistocene ice-pushed moraine of Het Gooi. Variation in the vegetation and in the habitat factors (groundwater and peat soil) of fens depends whether or not the fens are connected to the outflow of the regional groundwater system.Changes in the regional groundwater flow system, caused by changes in the water management of the polders, are probably responsible for the deterioration of mesotrophic fens. Drastic measures will have to be taken to restore the hydrology on a regional scale if the mesotrophic fens are to be saved from extinction.Hydrological research that integrates the results of regional and local studies is essential if the ecology of fen ecosystems is to be understood.

Effects of restoration measures on nutrient availability in a formerly nutrient-poor floating fen after acidification and eutrophication

Abstract Acidification and eutrophication have caused great changes in fen ecosystems in The Netherlands. The main problems are the surplus of acid rainwater, forming a lens above the calcareous groundwater, and the blanket effect of the Sphagnum cover which results in a loss of rare species and species-rich plant communities. Research on effects of restoration measures was carried out in a floating fen with a vegetation type at present dominated by Sphagnum squarrosum, S. fallax and Polytrichum commune. The nutrient dynamics were compared in 64 experimental plots which received four different treatments: control, drainage, sod removal and combined drainage plus sod removal. The amounts of extractable and mineralisable N and P were significantly reduced after both sod removal treatments. There was a significant negative correlation (p 90% cover) in the plots that had only the sod removal: they remained dominant in the control and drainage treatments. In the drainage plus sod removal plots, however, these bryophytes were still absent and the coverage of many characteristic fen species had increased considerably. These conditions have persisted for a further three years (to 1995).

Restoration of lost aquatic plant communities: New habitats forChara

In the Netherlands peat was excavated for fuel until 1950. This gave rise to waterbodies (called turf ponds) which were then colonized by aquatic plants. Succession resulted in different aquatic plant communities and more terrestrialized stages such as floating fens. Nature conservation authorities started to excavate new turf ponds in 1990(ca. 2 ha y−1) with the aim to restore calcareous, mesotraphent ecosystems by totally setting back succession. A sequence of new species was revealed by mapping the aquatic vegetation from 1990 onwards.Chara spp. proved early colonizers, which was not expected because they have not been present in ditches and ponds in the area for the last 20 years. The denseChara vegetation prevents the resuspension of organic soil and contributes to keep the water column nutrient-poor and clear. ability of species such asStratiotes aloides to colonise the ponds from adjacent waterbodies is not possible because no open contact exists between a turf pond and a ditch. Management measures, such as re-introduction, have to be considered if the full-range of aquatic plant communities remains the goal.

Geochemistry and flooding as determining factors of plant species composition in Dutch winter-flooded riverine grasslands

Dutch water policy aims for more frequent, controlled flooding of river valley floodplains to avoid unwanted flooding elsewhere; in anticipation of increased flooding risks resulting from climate changes. Controlled flooding usually takes place in winter in parts of the valleys which had not been subject to flooding in the last decades. It may thus affect existing nature with its conservation values. The goal of this study was to clarify the geochemical and hydrological factors determining plant species composition of winter-flooded river valley grasslands. A correlative study was carried out in 43 sites in 13 Dutch river valley floodplains, with measurements of flooding regime, vegetation composition, soil nutrients and soil pH status. With the use of canonical correspondence analysis (CCA) the plant species composition was investigated in relation to the geochemical variables and the winter winter-flooding regime. We found that the distributions of target species and non-target species were clearly correlated with geochemical characteristics and flooding regime. Clustering of sites within the CCA plots has led us to distinguish between four types of winter flooding in our areas: floodplains with (a) accumulating rain water, (b) low groundwater levels flooded with river water, (c) discharging groundwater and (d) high groundwater levels flooded with river water. Our major conclusions are (1) the winter groundwater level of winter-flooded grasslands was important for evaluating the effects of winter flooding on the geochemistry and plant species composition, and (2) winter winter-flooding effects were largely determined by the nature of the flooding. A high frequency of flooding particularly favoured a small set of common plant species. In areas with groundwater seepage, winter flooding may provide geochemical conditions suitable for diverse vegetation types with rare species. Rainwater flooded sites appeared less suitable for most target species.

Changes in plant biomass in fens in the Vechtplassen area, as related to nutrient enrichment

Species-rich floating fen ecosystems in former turf ponds in the western part of The Netherlands are subject to nitrogen enrichment because of high atmospheric N deposition (50 kg ha−1,Y−1,). and supply of polluted river water in dry summer periods. Further, some fens have become more influenced by rain water because downward seepage to the groundwater has increased due to hydrological alterations. This paper describes changes in plant biomass production by comparing seasonal maximum biomass values for 15 fen sites determined with standard procedures in 1981 and 1988. Fen sites in different polders showed different species composition, which is related to differences in hydrology and history of fen management among the polders. The ‘mid-succession’ fens (type 1) which are characteristically N-limited have shown a biomass increase in spite of the annual mowing regime, which shows that these fens are becoming enriched with nitrogen. There are indications that the role of phosphorus as a limiting factor increases in these fens, and that a shift of N-limited towards P-limited phanerogam growth occurs. This may bring these fens eventually in the ‘late-succession’ stage, as presently found in Het Hol (type 2). The fens in this stage are P-limited and have a different species composition. It was concluded that the mesotrophic fens in the Vechtplassen area, characterized by a species-rich vegetation, can only persist in their eutrophicated environment if they are located in a groundwater discharge area and if they are annually harvested in the summer. If all fens in the area, will eventually become P-limited it is expected that the species composition will change to a more uniform ’late-succession’ vegetation type.

Measures to develop a rich-fen wetland landscape with a full range of successional stages☆

Abstract Species-rich plant communities characteristic for succession from mesotrophic open water to fen are very rare in The Netherlands. These vegetation types used to occur in turf ponds in the low lying peatland area, created by peat dredging and filled with water due to seepage of mesotrophic, well-buffered groundwater. One of the goals of the National Nature Policy Plan is to create new opportunities for the initial terrestrialization communities through ecological engineering, e.g., restoration and creation of open water habitats. Restoration of the abiotic conditions in acidified floating fen communities is only possible by a combined measure of removal of the Sphagnum -layer and superficial drainage of surplus rain water. New turfponds have been excavated. This study showed that the abiotic conditions (i.e., water depth and water chemistry) are favorable for the development of aquatic communities characteristic of mesotrophic conditions. The aquatic plant species found in the new ponds also point in this direction, e.g., Chara major and Ch. delicatula are very abundant as are seven Potamogeton species. It is concluded that a constant discharge of groundwater and a good connectivity between the ponds and the existing remnants of plant communities desired in the area are essential for the conservation and development of these species-rich plant communities.