British National Vegetation Classification Research Articles

Datailed surveying and mapping of plant communities on featureless terrain

AbstractA system of detailed vegetation mapping has been developed for use on undulating terrain where there is a complex mosaic of soil types, drainage characteristics and plant communities and where topography is such that it is impossible to locate a position by reference solely to a map grid reference point, for example hill/moorland grazings, sand dunes and mud flats. The system involved using electronic surveying equipment to locate accurately, in terms of National Grid coordinates and altitude, a large number of points over the area to be surveyed for which vegetation types were identified and recorded. The merged location and vegetation data set for individual points were imported into a geographic information system (GIS) to map ‘point’ vegetation data accurately. The GIS was then used to create regions around points (voronoi) using Delaunay triangulation to produce a vegetation map. Altitude information was used within the GIS to produce a contour map of the surveyed area.Vegetation was classified into communities of the British National Vegetation Classification and, although it does not describe all the variants within communities/sub‐communities fully, extra information for individual point locations was stored in tables within the GIS. This information was readily accessed by using the mouse cursor to highlight a point and reveal a window containing all the tabulated information for that point.This methodology was used to produce a reliable map that accurately positioned and mapped previously unmarked landscape features, new boundaries/fences, vegetation types and contours. This facility could be used for a variety of experimental, planning and consultancy applications including botanical survey work, grazing behaviour studies, conservation, land use planning and management.

Re‐creating Semi‐natural Communities: Effect of Sowing Rate on Establishment of Calcareous Grassland

AbstractRestoration ecologists are increasingly aware of the potential to re‐create chalk grassland on abandoned farmland. Success is often hampered by lack of desirable species in the seed bank and by poor dispersal from nearby sites. In certain schemes, the input of seed may be essential. Locally collected seed is desirable but availability is limited. We examined whether lower sowing rates than currently recommended may be successfully utilized, facilitating more‐efficient use of available seed. Experimental plots on former agricultural land were sown at different rates in a randomized complete block, and the vegetation was surveyed for two years. We compared species richness and cover for chalk grassland plants and weeds ‐ species not associated with chalk grassland communities. Values for cover and abundance were matched with data for communities of the British National Vegetation Classification (NVC). Species richness for chalk grassland plants increased with sowing rate and with time, although after two years there was no significant difference between the treatments sown at 0.4, 1.0, and 4.0 grams of seed per square meter. Weed species decreased with increasing rate and time. After two seasons, the vegetation on all treatment plots was similar to that of recognized NVC chalk grassland communities, while the controls were dominated by weeds and showed signs of developing into species‐poor grassland. Higher rates rapidly eliminated weeds, but even a small inoculum of seed seemed to significantly enhance establishment of desirable plants and to reduce weed cover. We conclude that lower sowing rates would enable the desired vegetation to become established successfully, under appropriate conditions and management regimes. Lower rates allow for the re‐creation of sizable areas using local seed, and they minimize damage to donor sites.

Effects of afforestation on upland plant communities and implications for vegetation management

The British National Vegetation Classification (NVC) was used to describe the vegetation of Kielder Forest, an upland forest in NE England. Eighteen NVC units were recognised in the forest, of which nine accounted for the majority of the unplanted area. Under the crop, only five communities were recognised; 17% of stands had no ground vegetation whilst a further 40% had too little ground vegetation to allow for a satisfactory fit to any recognisable unit. Comparison with vegetation surveys carried out in southern Scotland showed acid grasslands to be much more prevalent there while wet and dry heath were less frequent than in Kielder. A sequence of vegetation changes was identified in the early development stages of second rotation crops. With recognised vegetation unit, through a flora similar to the pre-afforested vegetation of the area, to a vegetation with closer affinities to native Oak-Birch woodland. This development is halted at canopy closure when the ground vegetation is shaded out. Plantation stands fitting closest to native oak-birch woodland are characterised more by the species they lack than by the species which are common to both. Variation in the floristic composition of stands within forests are related to both natural variability, as related to soil and altitude, and to forestry induced changes including changes in landuse, drainage and ploughing and shading by the trees. The natural and management induced changes in the vegetation communities recognised in the forests are summarised and the identity of forest variants of native woodland associations are proposed in which groups of species are consistently over- or under-represented. The value of vegetation classification in conservation management planning is considered through the development of a series of management units based on the broad vegetation types and physiographic features of Kielder Forest before broadening the discussion to consider a wide range of possible management objectives and factors which may influence their successful implementation.

Thirty Years of Change in the Vegetation Communities of Three Valley Mires in Suffolk, England

Detailed floristic records from 12 mires on three Suffolk fens were gathered in 1959 and 1991. The data were analysed using tabulation and ordination to elucidate change at the plant community and individual species levels. Substantial changes at both levels were observed. The respective roles of three factors, namely lack of traditional management, changes in water regime and increased fertility, in accounting for these changes, have been explored. At community level, those mires which showed the greatest alteration were those subject to hydrological disturbance combined with dereliction. In terms of the British National Vegetation Classification they changed from short sedge mires allied to M13 Schoeno-Juncetum towards highly fertile tall herb fens with many ruderals and allied to S26 Phragmites australis-Urtica dioica fen. Partial dewatering led to M27 Filipendula ulmaria-Angelica sylvestris tall herb fen with few non-fen ruderals. Mires where ground water influx was reduced or eliminated but where traditional management was sustained showed less community change, with more of the principle community dominants being maintained. Here M13 Scheono-Juncetum mires developed into dry variants of M24 Molinia caerulea-Cirsium dissectum fen meadows. Mires with undisturbed hydrology but which became derelict were transformed from M13 Schoeno-Juncetum into hydrophytic Cladium-dominated communities of the S25 Phragmites australis-Eupatorium cannabinum tall herb fens. Many fen species were retained or recruited, while the colonization of ruderals, scrub and non-fen species that was noted in the dewatered mires did not occur. The dewatered mires showed the greatest alteration at species level. In unmanaged areas, all of the fen associates and bryophytes were lost and replaced by non-fen species and ruderal tall herbs. Where traditional management was maintained, most of the small species characteristic of wet fens and semi-aquatic conditions were still lost, although recruitment of ruderals and non-fen plants was less evident, being restricted to species of mesotrophic meadows. Retained species tended to be common fen plants or non-fen species. Mires which were derelict, but where the natural hydrology persisted, showed the least change in associated flora. Nevertheless, many of the smaller herbs were still eliminated by competition in the now dense tall-herb fen, indicating that traditional management was required as well as hydrological integrity for the survival of most wet-fen species. However, some wet-fen species were retained or recruited, indicating management to be subordinate to hydrology in their maintenance. They include Caltha palustris, Valeriana dioica, Lotus uliginosus and the bryophytes Campylium stellatum, Aneura pinguis, Sphagnum subnitens and Riccardia multifida. All mires showed a decline in conservation importance as measured by indices of botanical 'quality'. The mires which showed least decline (15-64% reduction in Rarity Weighted Principal Fen Species Score) were those which retained their hydrological integrity, regardless of management status. One mire, only partially dewatered but still managed, declined by nearly 70%. Although there were problems with the data, tentative comments are made on the relative importance of the three environmental factors to the maintenance of mire systems. It is concluded that maintenance of stable hydrologies is more important than extensive management in the long-term conservation of these sites.

VEMM: predicting the effects of agricultural management and environmental conditions on semi-natural vegetation

Abstract The Vegetation Environment Management Model (VEMM) is a decision support tool to assist field managers and landscape planners with the practical management of semi-natural vegetation. It is designed to allow the user to assess the impacts on vegetation of various agricultural management scenarios, such as grazing, cutting or fertiliser regimes, under different sets of environmental conditions. Predictions of the suitability of each scenario for particular assemblages of plants, within the framework of the British National Vegetation Classification, can be made, in addition to prediction of the abundance of individual plant species. The VEMM is implemented on a PC running Microsoft Windows.

A preliminary method of predicting plant species distributions using the British National Vegetation Classification

1. The British National Vegetation Classification (NVC) was used to develop a modelling system to predict the habitat suitability for plant species on the basis of environment and management information. 2. The model was developed for a subset of 27 plant communities (containing 534 species) in the area of the catchment of the River Tyne in north-east England. Environmental inputs into the model included climate and soil data, whilst management inputs included sheep stocking rates, fertilizer applications and cutting regimes. 3. The model was validated by comparing the predicted plant communities and species with those observed at two sites of contrasting scales: at a farm scale on 96 ha of moorland on a Northumberland farm, and at a landscape scale on 15 km 2 of upland moor in Northumberland. 4. The accuracy of the model predictions for plant communities appeared to be related to their spatial scale, whilst the accuracy of species predictions was dependant on their constancy within communities. Predictions were more accurate for species than for communities. 5. The potential use of this modelling approach, and possible extensions to the methodology, are discussed in relation to land management.

Application of the British national vegetation classification to the communities of the park grass experiment through time

The Park Grass Experiment at Rothamsted consists of a series of fertilizer treatments which have been applied to a species-rich hay meadow annually since 1856. Detailed botanical analyses of the plots between 1862 and 1992 were classified to one of the National Vegetation Classification (NVC) communities using the similarity measured by Czekanowski coefficient using computer program MATCH. Results indicated that “control” unfertilized plots were a relatively stableCynosurus cristatus-Centaurea nigra dicotyledon-rich grassland. However mineral fertilized plots moved towards a species-richArrhenatherum elatius grassland MG1e after 50–80 years and remained there. Plots receiving nitrogen fertilizer moved first to MG1e then on to aLolium perenne-Alopecurus pratensis grassland MG7D. Perhaps the most interesting plot was one which received a low rate of the soil acidifying ammonium sulphate fertilizer; the species composition changed towards a MG7D (Lolium perenne-Alopecurus pratensis) community between 1856 and 1903 but since then a liming treatment has been applied to part of the plot and the species composition on that part has recovered to a MG5 community resembling the control plots, taking 70–90 years to do so.

Who makes the assembly rules?

I asked whether there was any evidence that plant communities exist, in sense of assemblages in which co-occurrence of plant species is restricted by generalized assembly rules (Wilson 1991). I gave examples of possible assembly rules; it was not intended to be an exhaustive list. However, I would not like in advance to agree on a list of n properties a system must have, as Keddy (1993) advocates. It's like hunting for Yeti (Wilson 1991). We can have various guesses what it would be like, and look for that kind of beast, but we have to keep an open mind until/unless we find it. Similarly with plant communities, we can have various guesses what assembly rules might be, but real question is which rules we can find evidence for in nature. The plants make assembly rules, we have to find them. The question of whether plant assemblages exist, in which co-occurrence of species is limited by generalized assembly rules, is a basic question of plant community ecology. In fact, question. It must be answered by careful examination of plant communities. We have to: formulate hypotheses on what generalized assembly rules might exist, find ecological situations where we can test those hypotheses, see whether there is any evidence for rules, subject to usual statistical tests to ensure that patterns are not due to chance. M.B. Dale (1994) seems to be advocating something very similar to this. However, I have always sought simple, summary rules. As Dale implies, there is a limit to depth of insight we can obtain about a community by examining its static structure. Obtaining a complete set of assembly rules, as Dale suggests, would be difficult in practice. The question I asked (Wilson 1991) can be phrased in various ways: Do plant communities exist in any more meaningful sense, as integrated, discrete entities?; Are there phytosociological limitations on occurrence or abundance of plant species?; Are there 'Assembly' rules ... ? . Of course, it is possible to change definitions of terms in these questions, so intended meaning is removed and questions become tautologies. Palmer & White (1994) suggest doing this with term 'community'. This would indeed put debate about their existence behind us (Palmer & White 1994), but by sweeping it under carpet. I fail to see how not answering question advances science. There is a fatalistic thread running through some of these Forum contributions. Keddy (1993) implies that such questions about assembly rules are 'untractable'. Palmer & White (1994) believe that: 'Vegetation science has no hope of discovering such a force'. Dale (1994) questions whether: the effort expended on finding them is worth gain. I do not believe we should give up. Assembly rules can be found. I cited (Wilson 1991) examples of apparent assembly rules. Since then, I have found evidence for limitation to species coexistence at a fine scale (Watkins & Wilson 1992; Wilson et al. 1992a), and for community structuring by guilds (Wilson & Roxburgh 1994; Wilson & Lee in press). Not only can it be done, it has been done. The problem, as I see it, is that if there are no assembly rules there to discover, then vegetation science is reduced to stamp-collecting. Take, for example, British National Vegetation Classification (Rodwell 1991, etc.). This is a monumental work, widely admired

The Effects of Afforestation on Upland Plant Communities: An Application of the British National Vegetation Classification

The Effects of Afforestation on Upland Plant Communities: An Application of the British National Vegetation Classification

Computerized matching of relev�s and association tables, with an application to the British National Vegetation Classification

Computerized matching of relev�s and association tables, with an application to the British National Vegetation Classification

Continuous, R-F induction selective hardening equipment

Restoration of diverse semi-natural grasslands is potentially limited by high availability of soil phosphorus (P). Successful targeting of restoration effort requires a knowledge of plant community tolerances to soil P availability. Many extraction methods for P availability have been developed but most are calibrated against the growth and P uptake of crop species grown in monoculture.To test which methods are most suitable for measuring available P in soils of mesotrophic grasslands, a bioassay experiment was undertaken to compare seven extraction methods with the growth and P uptake of grassland species. Five species were grown together on a soil treated to create a range of conditions of pH, mycorrhizal infection and P availability.Olsen P and Bray P were found to be significantly correlated with P uptake in plant growth across the range of soil treatments whilst ion exchange membrane P and resin P were significantly correlated with P uptake in plant growth in all but the calcareous soils. The acid extractions of Truog, acetic acid and EDTA–ammonium acetate were found to be less correlated with P uptake in plant growth. All extraction methods correlated more strongly with P uptake in the sterilised treatments than in those inoculated with mycorrhizal spores.The method of Olsen was therefore selected to analyse P availability in soils supporting a range of mesotrophic grassland communities from eleven sites across England. At each sampling location, the species composition of the vegetation was assessed and classified using the British National Vegetation Classification (NVC). Species-rich hay meadows across a range of alliances were found to occur on soils with low phosphorus availability. Species-poor communities, such as inundation grassland, were found to occur on soils with higher phosphorus availability. Pasture communities, of intermediate species richness, tended to occur on soils of intermediate phosphorus availability.Olsen’s method of P extraction is recommended for analysing soils of areas identified for habitat creation; values of less than 10 mg kg−1 will give the greatest potential for the restoration of species-rich mesotrophic grassland.