De Levende Natuur nummer 6 van 2017 (English summary)

Knowledge of water systems as a basis for restoration of brook valleys

A.T.W. Eysink, R.J.J. van Dongen, M.A.P. Horsthuis & H. Smeenge

Although they mostly look pristine, brooks and brook valleys are most of the time influenced by humans. Prior to a brook restoration, it is important to have enough knowledge about historical ecological aspects, the long-term interrelationship between earth, natural and human processes and patterns. For the estate of Singraven in Northeast Twente (Province Overijssel), strictly local knowledge from the spatial patterns and processes that played a role over the centuries was used to explain the functioning of the system. Patterns in hydrology were explained and this helped visualizing opportunities for nature restoration in the estate. It shows that a system analysis becomes more valuable when cultural history is taken into account as well. For Singraven, it resulted in a good balance for the cultural heritage with agriculture, forestry and nature.

The landscape ecology of Teut-Ten Haagdoorn, a Flemish stream valley- and moorland

G. Sterckx, A.J.M. Jansen, K. Thijs, G. Beckers, L. Vanoppen, G. De Blust, J.J. Vogels & P. De Becker

The nature reserve Teut-Tenhaagdoorn is a hotspot for species of heathlands and oligotrofic and mesotrophic sloping fens in Flanders. Despite active nature management, many of the most critical species have declined or survived only in small relict populations. A landscape ecological system analysis was carried out to gain insight in the key processes that determine the occurrence of the protected habitats and species. It revealed that:

• active peat formation in sloping fens is the key-process for the major part of the wet habitats and, therefore, should be promoted in order to restore and preserve a robust ecosystem. However, this locally conflicts with the conservation of endangered species of oligotrophic waters, like Lobelia dortmanna, in the former fish ponds. The challenge is to choose the most suitable locations for the preservation of such species, and manage them accurately, within the framework of large scaled, process based nature management aiming at peat formation.
• there are unexpected and complex relations between reduced rain water infiltration and the desiccation of the upper course of the Hutte- and Laambeek on the one hand and the degradation of the brook and fen system of the Roosterbeek on the other hand;
• the ground- and surface water are relatively base-poor and weakly buffered. Differences in iron concentration of the surface water determine the major vegetation zonation along the altitudinal gradient of the brook valleys;
• nowadays, sites with known historical extensive agricultural use within the heathland landscape are important refuge sites for critical heathland plant and animal species, thanks to their higher concentrations of cations and moderately high phosphate levels. In the long term, active measures against acidification will be necessary to maintain these valuable conditions;
• due to fundamental differences in soil formation processes, sod cutting should be primarily performed in former drift-sand and psammophilic heathlands on sand dunes, whereas sod cutting in stable, acidic dry heathland situations should be avoided.

Regime shift in forests on sandy soils

B.J.M. Nyssen, R.F. van der Burg & E. Desie

The original lime-oak forests on poor sandy soils in The Netherlands have degraded to nutrient poor heathlands as a consequence of changes in land use. Reforestation of these soils in the 19 th and 20 th century with tree species characterised by poor quality litter, mostly Scots pine, was insufficient to fully restore the degraded forest soils. Partial replacement of the pines by species with more easy degradable litter (‘rich-litter’) such as Winter lime, Sycamore maple and Common hazel is expected to cause a belowground regime shift from the current Al/Fe process domain to the Base process domain. This regime shift will restore the current forest beyond its spontaneous succession and hence result in higher biodiversity and resilience of forests on poor sandy soils.

Casus; Ecosystem approach on the forested area Groote Heide, The Netherlands

R.F. van der Burg, M. Bartels & B.J.M. Nyssen

‘Groote Heide’ is a species poor forested area of about 350 ha on former heathland that consists of mainly coniferous forests and several degraded fens. A so-called ‘Eco-hydrological System Analysis’ was carried out in order to define measures for restoration of the fens and habitats of different forest types. The analysis led to a range of hydrological measures, aimed at a complete restoration of the whole area and the fens specifically. In addition, native tree species with rich litter were planted in selected areas. The flora and fauna of the fens reacted spectacular and various endangered species, like Eleogiton fluitans, Apium inundatum and Ranunculus ololeucos, returned. In the forests, results were also positive though less visible.

Chances of restoring a complete bog landscape

J.H. Bouwman, G.J. van Duinen, R. Veeneklaas & A.J.M. Jansen

In the past decades, nationally and internationally, there has been greatly invested in restoration of raised bogs. The focus of these restoration measures is on rainwater retention and maintaining a constant high water level in the bog remnants. The restoration projects are successful, however it appears to be difficult to restore the distinctive bog gradients. These gradients from the nutrient poor, acid bog massif to the nutrient richer and more buffered surrounding lagg are essential for many species of bog ecosystems. In The Netherlands, the presence of their habitats is strongly diminished. Therefore, in restoration projects it is important to try to restore the whole bog system, including the gradients to the surrounding landscape. We distinguish three types of bogs in The Netherlands. All three have different threats and possibilities for the restoration of laggs. Conducting an ecohydrological landscape analysis of a bog remnant gives insight into the current and historical landscape processes, such as hydrology and land use. This knowledge is essential for successful restoration on the landscape scale. The analysis will help to determine which restoration measures can be applied to restore the typical bog gradients and concurrent biodiversity.

Dry lowland heathland landscapes in the 21th century: focus on mineralogy and historic land use

J.J. Vogels, R. Bobbink, M.J. Weijters & H.L.T. Bergsma

The biodiversity of lowland dry heathland landscapes has deteriorated markedly. In order to restore and protect the characteristic biodiversity of these systems on the landscape scale, the authors make a plea to restore regional and local differences in soil buffer capacity and soil mineralogy, and to re-instate extensive heathland farming practices where possible.

Even in a small country such as The Netherlands, remarkable regional differences in soil mineral composition exist, explaining differences in historic and present species composition, as well as past and current soil acid neutralizing capacity. Due to increased acidification, these differences are in the process of being leveled out, resulting in the observed biodiversity loss. Since both base saturation and remaining soil mineral budgets have deteriorated markedly, addition of base cations by means of liming or rock flour addition as restoration measures should be considered. Re-instating small scaled farming practices in heathlands will also prove to be beneficial in the protection of many heathland characteristic species, including many, rapidly declining farmland birds. In order to do justice to regional differences in soil characteristics and its associated biodiversity, the implementation of these measures should be based on site specific conditions, and require a deep understanding of local site characteristics such as soil mineralogy, soil types and historical land use patterns.

Manipulating ecosystems as an alternative method to control non-native invasive species

H.H. van Kleef, J.M.M. van der Loop, B.J.M. Nyssen & E. Brouwer

The number of non-native species with adverse ecological consequences is increasing. Many of these species are difficult to eradicate because they are hard to locate, able to regrow or have a formidable dispersal capacity. Here we use theory and practice to propose a different method to manage non-native invasive species.

Invasion theory shows us, that invasibility of ecosystems is determined by availability of free niches. These may appear due to large scale disturbances and changing environmental conditions, resulting in opportunities for newly arriving species. Landscape ecological analyses help us identify key changes in ecosystems responsible for invasions of non-native species. For two invaded ecosystems we analysed the historical changes in the native community and men’s role therein, in order to identify key factors facilitating the invasion of Pumpkinseed sunfish (Lepomis gibbosus) and Black cherry (Prunus serotina). Both species appear to profit from human actions: acidification and nature management in the case of Pumpkinseed sunfish and economical afforestation and harvesting in the case of Black cherry. The resulting species in poor environments are devoid of predators and competitors allowing these non-native species to thrive. The solution is simple: Pumpkinseed sunfish can be controlled by introducing a native piscivorous predator, the Eurasian pike (Esox lucius), whereas Black cherry can be controlled by introducing suitable competing tree species.

The increasing number of problematic non-native species forces us to develop new approaches for minimizing their ecological impact. Minimizing free niches by manipulating ecosystems prone to invasions is a new and promising approach.

Processes and coherence in the landscape

P.C. Schipper

Landscape ecology is a fairly young scientific discipline, of great importance in the safeguarding nature reserves. Understanding processes and features in the landscape, known as Genus locus, is essential in planning of the management of these reserves. Local knowledge is essential to explain the functioning of landscape units and thus revealing opportunities for nature restoration. Scale is an important aspect in analysing the reserve and understanding the importance of the changes in land use of the surroundings. Also animals use scale and are dependent on a variety of habitats, thus this variety of habitats should be included. Keystone species as Winter lime need special attention as they can enhance a regime shift in order to improve resilience of the ecosystem. To understand these processes in the landscape an interdisciplinary approach in required. This approach is gradually becoming practice, but is certainly not used everywhere. The planning of the N2000 network for instance is not based on this approach.