ELSEVIER Agriculture, Ecosystems and Environment 63 (1997) 221-225

Agriculture Ecosystems & Enwronment

The landscape as an ecosystem

H. Doing +'1 Department of Vegetation Ecology, Plant Ecology and Weed Science Agricultural University, Wageningen, The Netherlands

Abstract

Landscape, in this paper, is defined as "a complex of geographically, functionally and historically interrelated ecosystems" (also: "organised land"). For its planning and management, mapping of geomorphological, hydrological, and climatic conditions is crucial to understand the ecological patterns. To warrant the landscape's sustainability, its ecosystems' multiple and interdependent functions should be carefully identified on macro-, meso- and micro-level. It is argued that, whereas a natural ecosystem is homogenous, the landscape ecosystem is heterogeneous, for example in a mosaic or zoned way.

Like evolution in organisms, succession in ecosystems tends do develop toward increasing independency from environmental fluctuations (increasing autonomy of the systems). On the contrary, landscape ecosystems have increasingly lost their regional autonomy over the last decades, as external input technologies became favoured. However, theories and practices of ecological (organic) agriculture, low external input oriented as they are, tend to re-enforce the local ecosystems' autonomy together with the regional identity. In the Netherlands intensive and widespread land reclamation (polders and floodplains) made hydro-ecology a major landscape-ecology determinant. Distribution patterns of floristic species are found to reflect the hydro-dynamic conditions in natural and semi-natural ecosystems. Provided that suitable knowledge on local conditions is available, they can be used as indicators of potential sites for nature regeneration and indicate landscape degradation as well. Even though potentially favouring agro-ecosystems diversity and regional autonomy, ecological types of agriculture, as currently defined by law, do only promote nature on the farm when the farmer dedicates special attention it as an additional objective of his (organic) farming. © 1997 Elsevier Science B.V.

Keywords: Regional autonomy; Agro-landscape; Landscape-ecosystem; Ecological agriculture; Species' distribution patterns

1. Introduction

At the first meeting concerning this Concerted Action in Wageningen (in 1993), I defined landscape as a complex of geographically, functionally and historically interrelated ecosystems, or, more briefly, as "organised land" (i.e. organised by nature and by

man). Although this definition differs from that adopted in the working group, they are not in con- flict with each other. In this contribution, this defini- tion is explained in more detail, with examples.

2. Mapping

* Corresponding address: J.D. Mansvelt, Fax: + 31 7484995. 1 Retired from Department of Vegetation Ecology, Plant Ecol-

ogy and Weed Science, Agricultural University, Wageningen, The Netherlands. No correspondence to Dr. Doing--Deceased.

For planning and management of landscapes on any scale, maps are indispensable tools. Useful for this purpose are land use maps, vegetation maps, soil maps, hydrological maps etc. In my survey of sand

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222 H. Doing/Agriculture, Ecosystems and Environment 63 (1997) 221-225

dune areas, my starting point was vegetation, and the result I have called "landscape maps on a phytosoci- ological basis".

In my opinion, however, units of the phytosocio- logical classification system in most cases are not suitable as mapping units. To begin with, local patches of vegetation often do not fit into these units. Other reasons are partly a matter of scale, partly of content. A landscape contains a complex of concrete vegetation patches, some of which may cover many hectares, others only a few m e. Vegetation classifica- tions are mainly based on species composition and structure of plant communities, dependent on present and past variation in environment, and showing ex- treme variation in minimal area of the (abstract) units, from a few dm 2 to 1000 m 2 or more. The smaller sized units cannot be neglected because they may be at least as important as the larger ones from an ecological or practical viewpoint e.g. because of the occurrence of good indicator species or species of conservational or economic importance (commun- ities of steep north slopes in the sand dunes, of small stream beds in a desert, of ditch banks in a polder). In contrast to this, mapping units are, by definition, geographical units, as such dependant on scale, and for this reason mostly containing more than one vegetation unit (except on very large scale maps, e.g. 1 : 1000).

In the second place, a mapping unit signifies much more than vegetation only. A part of the surface of a good topographical map or an aerial photograph mostly shows substrates which are not covered by vegetation: ploughed fields, open water, road surfaces and buildings, rocks etc., and in the case of deserts, beaches or glaciers these are even predominant. A prominent feature of a landscape is its geomorphology, even in flat countries. Vegetation patterns are almost always determined by geomor- phology, with its underlying soil diversity; the same holds for hydrological conditions. Patterns of soils, meso- and microclimate and animal communities are not so easily visible, but are also equally important landscape components.

3. F u n c t i o n a l r e l a t i o n s h i p s

If a landscape map is to be used for planning or management, i.e. to be more than a nice coloured

abstract picture, it must be based on functional rela- tionships between all landscape attributes. These re- lationships are the basis of the ecosystem concept. Vegetation and soil are so closely interwoven and interdependent, that no clear line can be drawn be- tween them. Roots are constantly absorbing matter from the soil, dying roots and litter are constantly adding matter to the soil. Similar spacial and func- tional relationships exist between vegetation and the atmosphere, vegetation and fauna, soil and ground- water, soil and micro-organisms etc. Vegetation is dependent on soil and atmospheric conditions, mi- croclimate is determined by vegetation structure, my- corrhizae and insect larvae are found inside plant bodies. A raindrop is part of the atmosphere at one moment, part of the soil the next moment, and part of the vegetation a little later. Distinctions between these components of the system are only for human convenience. Within the systems, co-evolution of plant and animal species (e.g. flowers and pollinating insects) has been going on for many millions of years.

If we want to understand or manipulate nature, we must think in terms of systems: biomass, nutrient cycles, energy levels and pathways, trophic levels (e.g. primary and secondary producers), relationships between diversity and stability. The importance of this approach for agriculture, forestry and conserva- tion is self-evident. The difference between conven- tional and ecological agriculture may be described as a much increased emphasis on the ecosystem point of view. Therefore, the concept of landscapes as ecosystems should, I think, be welcome in this cir- cle.

Systems exist on many levels, from atom to uni- verse. This has created much confusion, so we must be careful with our language. It depends on our purpose, which level to choose as a focal point. Ecosystems are all systems which contain biotic and abiotic components, which are interdependent. A single ecosystem is homogeneous in the character- istics just mentioned. Land use, vegetation structure, species composition, soil development and ground- water conditions should at the least be homogeneous. A complete ecosystem needs a minimum area, which is e.g. determined by the space needed for the func- tioning of nutrient cycles and of all groups of organ- isms, belonging to it.

H. Doing/Agriculture, Ecosystems and Environment 63 (199Z~ 221-225 223

A landscape is heterogeneous in this respect: it involves a mosaic or zonation of homogeneous ecosystems. It may contain pioneer and climax com- munities, rock outcrops, dune ridges and slacks etc. Functional relationships between the single ecosys- tems may exist via erosional and depositional pro- cesses, influence on atmospheric and groundwater conditions, movement of seeds and litter and via animals which move between various ecosystems (e.g. birds with different biotopes for breeding and for feeding).

In our (Wageningen) landscape studies of Dutch coastal areas we have created a system of landscape units, mainly on the basis of vegetation + soil com- plexes and geomorphology. These units could be distinguished in the field and on aerial photographs. Studies of geological and land use history have shown, that our units are indicative of these histori- cal processes and origins. In this case, we have studied natural and semi-natural landscapes (Doing and Westhoff, 1976). The question is whether this approach is also suitable for cultural landscapes. In my contribution on a Swiss mountain village (Doing, 1994), I have already made a step in this direction. I shall indicate some further steps in the following remarks.

4. Man as a master factor in the functioning of landscapes

Just as in the evolution of organisms, succession of ecosystems shows a tendency towards lesser de- pendence from the environment, reaching a greater resistance towards environmental fluctuations. In other words: to create an own environment, and become more stable, more self-supporting. E.g.: mi- croclimate and soil moisture show much smaller fluctuations in a forest than in a pioneer ecosystem. Human influence on landscapes results in more "openness" of landscapes as ecosystems, and rela- tively greater dependence on abiotic conditions. A natural landscape, including top-predators (wolf, lynx) shows a maximum of cyclic processes, involv- ing organisms (from seeds or eggs to destruction and mineralisation of bodies), nutrients, water and en- ergy. Human impacts, in the history toward nowa- days "modern" (conventional) agriculture, can

mostly be described as increasing in- and outputs. Seeds, plants, animals (mostly of non-native species), fertilisers, fodder etc. are imported from elsewhere, often even from other continents; biomass is re- moved from the land (harvested), creating pioneer- like communities. The role of predators is taken over by man (who can no longer be viewed as part of the landscape). Erosion and run-off of rainwater is in- creased, atmospheric deposition is world-wide im- ported from areas with industry and bio-industry. There are less and less local or regional ecosystems: this is part of the so-called enlargement of scales. Many of the ideas and principles of ecological agri- culture are directed towards the re-enforcement of the functioning of local ecosystems and small-scale landscapes, reducing in- and outputs in quantity, improving it in quality for use by man, saving en- ergy.

5. Examples of landscapes

Our coastal sand dunes are strongly influenced by man, but natural processes have always predomi- nated. Therefore, the visual aspect is that of a largely unparcelled landscape. For plant and animal produc- tion, they have always been small-output and even smaller input areas. Except for small numbers of goats, of cattle and of isolated areas with potato fields or sown pastures in moist slacks, flora and fauna have always been spontaneous in most areas (including completely naturalised species like rab- bits). Only in special places these have been sup- ported by planting marram grass (Ammophila) and native shrubs and trees. Locally, parcelled landscape elements are present on a somewhat larger scale, mainly fields of cereals (now abandoned) and pine plantations (still present, but planting of conifers has been discontinued). The most drastic change, in- duced by man, is the extraction, later counteracted by infiltration, of water in large dune areas on the mainland, resulting in the disappearance or inunda- tion of moist slack ecosystems. Because plant com- munities are still highly diverse and dominated by natural factors (soil development, local climate, graz- ing by rabbits, history of blowouts), we could use them as the main basis for landscape classification.

In cultural landscapes, other landscape compo-

224 H. Doing//Agriculture, Ecosystems and Environment 63 (1997) 221-225

nents, e.g. soil profiles, will gain a relatively greater importance. In an intensively cultivated landscape most of the area now contains little of botanical interest: nowadays arable land, orchards and pastures are extremely poor in plant species. By far the most species are present in vegetation fragments in the form of line and point elements: road verges, mar- gins of arable land parcels, banks of ditches and other waters, hedgerows etc. Combined with geo- morphological, hydrological and pedological data, in most cases distinction of landscape types on a botan- ical basis is still possible, comparable with that of natural or semi-natural landscapes. Where swamps or lakes have been reclaimed man has acted as a geo- logical agent, and polders (areas with a controlled water regime) form the major landscape units. In river flood plains a similar control was gained by man with the help of dike systems. No wonder that eco-hydrology has become a major branch of land- scape ecology in our country.

A stream valley or catchment basin is a common example of a natural geomorphological as well as hydrological landscape, not only in the mountains but also in almost flat areas like the Drenthian plateau in the northeastern Netherlands. Everts and de Vries (1991) have carried out an intensive land- scape ecological study of this area. They distin- guished landscape zones which are mainly controlled by hydrological conditions. Water quality and move- ment is determined by natural factors as well as by land use and by nutrients added by man. Upstream, midstream and downstream zones with different soils and vegetation are the result. The authors have also tackled the problem of ecological studies of cultural landscapes on the basis of fragments or small areas of natural and semi-natural vegetation. This problem was solved with the help of the distribution of a selected number of (relatively common) species. These could be used as indicators of present condi- tions, but also of potential occurrence of more natu- ral vegetation, including rare species. I quote some sentences from the summary of their thesis.

"An analysis of distribution patterns of vegeta- tion types or individual plant species may lead to straightforward studies of landscape processes, since much information on master factors of a land system is embedded in the spacial sequence of plant com- munities and distribution patterns of their species. In

order to understand such information, however, a good understanding of processes in land systems remains a prerequisite .... Landscape ecological prin- ciples have so far often applied to landscapes rela- tively weakly influenced by man, hence with natural or semi-natural vegetation series, such as peat form- ing systems, sedimentary areas of fluvial, marine or aeolic origin. The vegetation plays a major role in distinguishing the landscapes in those series. A simi- lar approach has been followed in this study, but this time in strongly human influenced small river valley landscapes, mainly dominated by semi-natural to purely cultural grasslands. The study was directed to the relationship between the vegetation and geo-hy- drology of the landscape. Therefore a hydro-ecologi- cal model is applied, with four different types of mutual relationships with the vegetation: operational, conditional, positional and sequential (according to Van Wirdum). The model emphasizes the regulating role of the hydrology in this set of relations....The distinguished land units purely reflect the hydrologi- cal feeding from different hydrological systems or at least from different aquifers .... Although in vegeta- tion science much effort has been aimed at measur- ing site factors (pH, base-saturation, water table etc.) in relation to species composition, little attention has been given to "translate" these measurements to hydrological influences and to the impact of human activities on these factors. In order to distinguish the latter influences we grouped all relevant vegetation units into four categories of human influences (hemerobic stages) .... The next step in our research was to use the variation in distribution patterns of species as a basis for landscape discrimination. The newly distinguished land units are now characterized by a specific combination of species distribution patterns reflecting differences in groundwater com- position, seepage intensity and flooding frequency .... The knowledge of long term vegetation dynamics in relation to hydrological processes may help in find- ing the most suitable sites for nature regeneration and diagnosing unwanted influences on vegetation development in a very early stage. It should, how- ever, be kept in mind that the process of regeneration will surely proceed differently than the process of degeneration .... The methods presented in this study are generally applicable to other landscape types, but adjustment to local conditions will always be neces-

H. Doing~Agriculture, Ecosystems and Environment 63 (1997) 221-225 225

sary, mainly because the obtained indicator values of hydrological features may differ from those obtained in other landscape systems."

I think the question whether the "Wageningen landscape approach" can be used to study cultural landscapes, has been answered quite satisfactorily in this study. In my opinion, a good phytosociological and floristic analysis is necessary in landscape stud- ies. This does not mean that a planner, agriculturist or landscape architect has to carry out these studies himself. In most European countries, sufficient ex- pertise is available from professional ecologists in order to obtain the necessary information.

important, and weed control takes place, by means of selection of seeds and by mechanical or flame weed- ers. There is less pressure on the environment, but it is just as effective ( = disastrous) for weeds and soil organisms. Promotion of nature is mainly successful when special attention is directed to it. Smeding (1994) has studied two dairy farms to evaluate the results. He found, that refraining from manuring field margins has a much greater beneficial effect on floristic diversity than integrated or biodynamic management of the fields themselves.

References

6. Influence of ecological agriculture

In areas with ecological or bio-dynamic agricul- ture, the situation for the development of more natu- ral elements is relatively favourable. Recently, in our country there is much discussion about the possible role of farmers in preserving existing or creating new natural landscape elements. Ditch banks and field margins (Joenje and Kleijn, 1994) play an important role in this. Ecological agriculture fits into this con- text. I may refer to some recent articles in "De Levende Natuur", journal for nature conservation and management.

According to Metman and Buitink (1994), ecolog- ical and biodynamic agriculture is characterised by a low input of fertilisers and herbicides, and therefore in principle provides possibilities for nature on the farm. However, this is not self-evident: also on this type of farm the nutritional value of the crop is

Doing, H., Westhoff, V., 1976. Begripsbepalingen ten behoeve van de pre-adviezen voor de Studiekringdag 1975 (Definitions of ecological concepts). Ned. Bosb. Tijdschr. 48 (3), 56-57.

Doing, H., 1994. Landscape mapping in a Swiss mountain village. In: D.J. Stobbelaar and J.D. van Mansvelt (Eds.), Proceedings of the First Plenary Meeting of the EU-concerted Action: the Landscape and Nature Production Capacity of Organic/Sus- tainable Types of Agriculture. Department of Ecological Agri- culture, Wageningen, pp. 137-142.

Everts, F.H., de Vries, N.P.J., 1991. De vegetatieontwikkeling van beekdalsystemen. Een landschapsoecologische studie van enkele Drentse beekdalen. Historische Uitgeverij, Groningen, 222 pp.

Joenje, W., Kleijn, D., 1994. Plant Distribution across Arable Field Ecotones in the Netherlands. BCPC Monograph, 58. Field margins: integrating agricultural conservation, 323-328.

Melman, Th.C.P., Buitink, H.E., 1994. Natuurbeheer door agrariErs: van stiefkind naar troeteldier? (Nature conservation by agriculture: from pariah to pet?'). De Levende Natuur 95 (6), 202-206.

Smeding, F.W., 1994. Ontwikkeling van flora en vegetatie op twee alternatieve melkveebedrijven (The development of the vegetation on two dairy farms on sandy soil). De Levende Natuur 95 (6), 207-210.