How robust are community-based plant bioindicators? Empirical testing of the relationship between Ellenberg values and direct environmental measures in woodland communities

There are several community-based bioindicator systems that use species presence or abundance data as proxies for environmental variables. One example is the Ellenberg system, whereby vegetation data are used to estimate environmental soil conditions. Despite widespread use of Ellenberg values in ecological research, the correlation between bioindicated values and actual values is often an implicit assumption rather than based on empirical evidence. Here, we correlate unadjusted and UK-adjusted Ellenberg values for soil moisture, pH, and nitrate in relation to direct environmental measures for 50 woodland sites in the UK, which were subject to repeat sampling. Our results show the accuracy of Ellenberg values is parameter specific; pH values were a good proxy for direct environmental measures but this was not true for soil moisture, when relationships were weak and non-significant. For nitrates, there were important seasonal differences, with a strong positive logarithmic relationship in the spring but a non-significant (and negative) correlation in summer. The UK-adjusted values were better than, or equivalent to, Ellenberg’s original ones, which had been quantified originally for Central Europe, in all cases. Somewhat surprisingly, unweighted values correlated with direct environmental measures better than did abundance-weighted ones. This suggests that the presence of rare plants can be highly important in accurate quantification of soil parameters and we recommend using an unweighted approach. However, site profiles created only using rare plants were inferior to profiles based on the whole plant community and thus cannot be used in isolation. We conclude that, for pH and nitrates, the Ellenberg system provides a useful estimate of actual conditions, but recalibration of moisture values should be considered along with the effect of seasonality on the efficacy of the system

Ecohydrology and groundwater dependent terrestrial ecosystems

Throughout the world ecohydrology has lately been discovered, and tightly embraced, as a new scientific discipline. Several authors have stressed its importance to the progress of hydrology and ecology but there appears to be a wide range of ideas on the topics ecohydrology is supposed to include. Elements of the history of ecohydrology are described here and different ecohydrologic schools are distinguished. One of the roots of ecohydrology is based on the dependence of phreatophytic plant species on groundwater. In the first half of the 20th century plants were regularly used as indicators in groundwater investigations by hydrologists. More recent the interest in phreatophytes in general revived again, following the interest in groundwater dependent ecosystems. A case study is used to show the benefit of use of phreatophytes in hydrological studies. It is argued that a well balanced use of ‘soft’ phreatophytic information can be complementary to ‘hard’ groundwater data and analysis techniques and help to understand more profoundly groundwater dependent ecosystems.status: publishe

Ecohydrology, phreatophytes and groundwater dependent ecosystems

Ecohydrology has been discovered, and embraced, as a new scientific discipline throughout the world. Several authors have stressed its importance to the progress of hydrology and ecology. However, there appears to be a wide range of ideas on which topics ecohydrology should include. We describe the history of ecohydrology and distinguish the different ecohydrologic schools. One of the roots of ecohydrology is based on the dependence of certain plants on groundwater, as was already recognized by Henry Philibert Gaspard Darcy. Oscar Edward Meinzer introduced the term ‘phreatophyte’ (Meinzer, 1923). He defined it as a plant that habitually obtains its water supply from the zone of saturation, either directly or through the capillary fringe. In the first half of the 20th century plants hydrologists regularly used plants as indicators in groundwater investigations, especially in the semi-arid regions of the U.S.A. Here the relation between vegetation and groundwater availability is obvious. After the first half of the 20th century hydrogeologists seemed to lose their interest in the use of phreatophytes in groundwater studies, but ecologists continued the study of their habitat requirements (Londo, 1988; Ellenberg, 1991). Recently the interest in phreatophytes in general was revived, following the interest in groundwater dependent ecosystems. In this paper, the ecohydrological schools are reviewed as well as the role of phreatophytes in ecohydrology and in assessment of groundwater dependent ecosystems. Case studies are used to demonstrate the benefits, limitations and complications of using phreatophytes in hydrological studies. Groundwater and particle tracking models, hydrochemistry and remote sensing are used to understand the distribution of plants and the composition of vegetation. These all contribute in understanding biodiversity and the functioning of groundwater dependent wetlands. In addition, phreatophytes may be helpful when designing groundwater models. In stable conditions, they reflect average long term hydrologic conditions, which can be assessed quite easily. It is argued that the well balanced use of ‘soft’ phreatophytic information can be complementary to ‘hard’ groundwater data and analysis techniques. This will result in a better understanding of groundwater dependent ecosystems.status: publishe

Dose Effect Model for terrestrial Nature; conceptual description of DENMAT-2

Abstract niet beschikbaarThe model DEMNAT-2 is designed to predict the impact of water management scenarios on groundwater-dependent ecosystems. The model can be applied to national and regional studies, provided there is enough ecological data available for this purpose. Input to DEMNAT is formed by hydrological changes, for example changes in seepage intensity and spring groundwater level, which can be predicted with existing hydrological models. Output is formed by changes in the completeness of 15 ecosystem types and in resulting values for nature conservation. Three modules of DEMNAT can be distinguished: geographical schematisation of a lot of hydrological and ecological data, dose-effect functions for calculation and valuation of effects. This report ends with a chapter discussing DEMNATs usefulness: its main shortcomings are shown and possible improvements mentioned.VW/RIZ

The eco-hydrological prediction model DEMNAT-2; analysis of scenario results

Eind 1990 besloten RIVM en RIZA gezamenlijk de ontwikkeling van een nieuwe versie van het Dosis-EffectModel NAtuur Terrestrisch (DEMNAT) ter hand te nemen. DEMNAT is een landelijk toepasbaar voorspellingsmodel voor de effecten van ingrepen in de waterhuishouding op de vegetatie. Voor een scenario-analyse met DEMNAT wordt alle informatie over vegetatie (ecotoopgroepen), bodem en grondwater (ecoseries) en hydrologische doses bijeengebracht. Er vindt een geografische schematisatie plaats naar ecoplots. Dat zijn ruimtelijke eenheden die homogeen zijn voor hydrologische eenheid, ecoserie en ecotoopgroep. De berekeningen vinden vervolgens plaats per ecoplot. De effecten kunnen per ecotoopgroep worden uitgedrukt als verandering van volledigheid. De effecten kunnen ook worden uitgedrukt als een verandering in natuurwaarde. Dit geeft de mogelijkheid om de veranderingen per afzonderlijke ecotoopgroep te combineren, rekening houdend met het relatieve belang uit oogpunt van natuurbehoud, dat aan de verschillende ecotoopgroepen wordt toegekend. Met DEMNAT kunnen berekeningen worden uitgevoerd voor vier typen ingrepen in de waterhuishouding, namelijk verandering van de Gemiddelde VoorjaarsGrondwaterstand (GVG), verandering in de hoeveelheid kwel, verandering in oppervlaktewaterpeil en verandering in het percentage systeemvreemd oppervlaktewater. Met DEMNAT kunnen zowel schade als herstel als gevolg van ingrepen in de waterhuishouding worden berekend. Voor schade en herstel worden afzonderlijke dosis-effectfuncties gebruikt. De reden daarvoor is dat voor veel combinaties van ecotoopgroepen, ecoseries en hydrologische veranderingen aanwijzingen bestaan dat herstel minder snel of minder volledig optreedt dan schade. Voor het Beleidsplan Drink-en Industriewatervoorziening en bijbehorend MER zijn 8 basisscenario's doorgerekend met DEMNAT. In een scenario wordt uitgegaan van een verandering in gewonnen hoeveelheid grondwater voor een bepaalde toepassing (o.a. drinkwatervoorziening) op een bepaalde wijze (o.a. freatische winning). Aangezien er vrij veel grondwater wordt gewonnen rond verschillende stuwwallen, zijn vooral langs de randen van stuwwallen aanzienlijke effecten gelocaliseerd.Ecotoopgroepen waarvoor in de meeste scenario's relatief grote veranderingen optreden, zijn degene op voedselarme, zwak zure bodem (ecotoopgroepen K22, H22, K42, H42, A12). Relatief kleine veranderingen treden op voor het grotendeels buiten het modelgebied gelegen K23 (kruidvegetaties op natte voedselarme basische bodem), en voor de meest algemene in beschouwing genomen ecotoopgroep A18 (aquatische vegetaties in zeer voedselrijk water). Uit de resultaten blijkt ook dat ten opzichte van de referentiesituatie verschillende scenario's een duidelijke bijdrage leveren aan het herstel van grondwatergebonden ecosystemen. Toch blijft herstel van de natuurwaarden zelfs bij een volledige beeindiging van de beschouwde grondwaterwinningen, nog beperkt tot minder dan een kwart van het verschil tussen de actuele situatie en de referentie. Andere ingrepen in de waterhuishouding zijn daarvoor van groot belang.The Dose-Effect Model for terrestrial NATure (DEMNAT) is a model for the nationwide prediction of effects of water management measures on vegetation. For scenario analyses with DEMNAT geographical data on vegetation (ecotope groups), soil and groundwater (ecoseries) and hydrological doses are combined. Effects can either be expressed as changes in the completeness (or relative species richness) of ecotope groups, or as changes in nature value. This allows combining changes in various ecotope groups, weighed relative to their significance for nature conservation. With DEMNAT both damage and recovery due to water management measures can be calculated. To this end, seperate dosis-effect functions for damage and recovery were defined, as recovery is often less rapid or incomplete. For the National Policy Plan on Drinking Water and Industrial Water Supply wich was to be accompanied by an Environmental Impact Assessment eight basic scenarios were evaluated. A scenario is defined by a percentual change in the amount of groundwater withdrawn in a certain way (e.g. from phreatic groundwater) and for a pre-defined application. As subsstantial amounts of groundwater are withdrawn from ice-pushed ridges, the largest effects occur around the ridges. Smaller effects occur over larger surfaces, especially at the Holocene alluvial plains along the boundary of the elevated Pleistocene parts of the Netherlands. Ecotope groups of nutrient-poor, weakly acid sites are the most severely influenced by most scenarios. A comparison of the results of each scenario with the reference situation shows that various scenarios may add substantially to the recovery of wet and moist ecotope groups.DGM/DW

Assessment of groundwater status in accordance with the Water Framework Directive

Dit rapport bevat een erratum d.d. 9 januari 2008 op de laatste paginaDe Europese Kaderrichtlijn Water (KRW) moet ervoor zorgen dat de kwaliteit van het oppervlakte- en grondwater in Europa in 2015 op orde komt. Het grondwater moet daarbij niet alleen aan zijn eigen doelstellingen voldoen, voldoende water van goede kwaliteit, maar ook aan de doelstellingen van de ecosystemen die door kwellend grondwater worden beinvloed. Het grondwater mag geen negatieve invloed hebben op de bijbehorende oppervlaktewateren en grondwaterafhankelijke terrestrische ecosystemen. In dit rapport wordt een beoordelingsmethode voorgesteld om vast te stellen wanneer de toestand van het grondwater niet voldoet aan de doelstellingen van de bijbehorende aquatische en terrestrische ecosystemen. Deze beoordeling gaat enerzijds uit van de doelstellingen voor de bijbehorende oppervlaktewateren en de grondwaterafhankelijke terrestrische ecosystemen en anderzijds van de beschikbare meetgegevens over de toestand van het oppervlaktewater, het terrestrisch systeem en het grondwater. Waarschijnlijk zal de grondwatertoestand door verdroging en de uitspoeling van bijvoorbeeld nutrienten, bestrijdingsmiddelen en zware metalen in een aantal gebieden niet voldoen aan de doelstellingen voor het oppervlaktewater en de terrestrische ecosystemen. Het al in gang gezette mestbeleid, verdrogingbeleid en de KRW zelf zullen een deel van de problemen oplossen. Daarnaast geeft het rapport voor een groot aantal landschaptypen met een grote natuurbehoudswaarde een overzicht van de ecohydrologische relaties en potentiele bedreigingen door aantasting van het grondwaterlichaam.The European Water Framework Directive (WFD) requires that all inland and coastal waters must reach a good chemical and ecological status by 2015. According to Annex V of the WFD, groundwater should not only meet its own environmental objectives, ensuring "sufficient water of good quality", but also the objectives for the ecosystems affected by groundwater seepage. Groundwater may not have a negative influence on associated surface waters and groundwater-dependent terrestrial ecosystems. This report presents an assessment system to determine when the status of the groundwater fails to meet the WFD objectives for the surface waters and terrestrial ecosystems which are directly associated with the groundwater body. In the assessment, the monitoring data available on the status of the groundwater and the associated surface water and terrestrial ecosystems are compared to the objectives which have been achieved for these systems. The environmental objectives for surface water and terrestrial ecosystems in a number of regions will most likely not be met due to groundwater drawdown and the drainage of, for example, nutrients, pesticides and heavy metals. Current polices on manure and fertilizer application, water drawdown and sanitation, including those of WFD, will improve the present groundwater situation. This report also presents an overview of the eco-hydrological relations of a large number of ecologically valuable Dutch landscapes as well as the potential threats to these landscapes when the groundwater system is adversely affected. This information is essential for the management of nature reserves in the Netherlands.VROM-DG