J. P. Grime

A functional analysis of a limestone grassland community

We examine the potential of standardised data, mainly collected in the laboratory, to elucidate mechanisms of species coexistence, using a south-facing, infertile, species- rich limestone grassland at Millers Dale, Derbyshire, Eng- land as a model system. Standardised autecological data for 15 of the more important Millers Dale species were obtained from the Integrated Screening Programme (ISP), and their functional attributes were reviewed in the context of a larger database, broadly representative of the British flora. Ordina- tion of adult plant attributes demonstrated that the Millers Dale species are strategically relatively uniform; most are slow-growing, evergreen and tolerant of mineral nutrient defi- ciency. Ordination of seed attributes revealed more variety among the Millers Dale species; the main axis of variation was from species with large, transient seeds (mostly grasses) to species with small, persistent seeds (mostly dicots). From the ordination we derive the predictions that germination of the latter species will be more temporally opportunistic and more inhibited by the presence of vegetation than the former. These predictions are consistent with data collected in experi- mental studies of seed persistence and germination at the site. These data suggest that spatial and temporal variation in opportunities for regeneration is an important mechanism contributing to the high species richness of dry limestone grasslands.

Declining plant diversity: empty niches or functional shifts?

The evidence is compelling. The planet is losing plant species and populations at a rate too fast to allow a case by case evaluation of the consequences for ecosystem functioning and human need. With limited time and resources available how can we recognize the problems likely to arise from plant losses and then decide the priorities for action? Ecologists with very different skills and experience have been attracted to this field of enquiry and over the last decade the subject has become the focus of heated debate (Loreau et al. 2001). Sufficient time has now passed for the architecture of this debate to be revealed and my purpose here is to comment on its progress and to recommend a change in direction. I will focus on the effects of diversity on productivity because it is this aspect of the debate that has attracted most attention.

Does Gulf Stream position affect vegetation dynamics in Western Europe

It is widely accepted that the climate enjoyed by maritime western Europe is strongly affected by the warming influence of the North Atlantic Gulf Stream. Until recently, however, little account has been taken of the fact that the latitudinal position of the Gulf Stream varies continuously. In theory, such displacements could generate year-toyear variation in crop yields and in the productivity and relative abundance of component species in natural vegetation. Here we test this hypothesis by examining the productivity of above-ground vegetation, monitored annually in permanent plots at Bibury (Gloucestershire, southern England) over the period 1966-1993, in relation to changes in latitudinal position of the Gulf Stream. The long-term field experiment on the road verges at Bibury (Yemm and Willis 1962, Willis 1972, 1988) has recently provided an unforeseen opportunity to examine year-to-year variations in species composition in permanent plots experiencing a standardized management regime (late autumn mowing). We examined inter-annual variation in mean total shoot biomass in each of the main Bibury species in relation to a Gulf Stream northerliness index (see legend to Table 1). Total productivity of above-ground vegetation was positively correlated with Gulf Stream northerliness (Fig. la). Annual species were negatively correlated with northerliness during certain periods, biennials showed no clear relations, and perennial species were positively correlated. Shoot biomass was positively correlated with northward displacement of the Gulf Stream in 10 species, showed a negative relation in three other species, and had no consistent effect on the remaining 10. Different species showed significant correlations with Gulf Stream movements at different times of the year (e.g. Fig. lb), and some species showed correlations with movements in the preceding year or in the year before that. Table 1 classifies the Bibury species according to response to Gulf Stream northerliness, life history and ecology (ecological data from Grime et al. 1988). Species favoured by northerly tracks include robust, perennial grasses (Bromopsis erect, Dactylis glomerata, Elytrigia repens and Festuca rubra). At Bibury, and across Western Europe, these grow rapidly in early spring and are major contributors to community biomass. The similarly responsive dicotyledons (Achillea millefolium, Gahum verum, Knautia arvensis, Plantago lanceolata and Vicia sativa) have relatively later phenologies and fairly deep root systems. Species declining in biomass with Gulf Stream northerliness (Anisantha sterilis, Galium aparine and Urtica dioica) are more heterogeneous ecologically, but are either annuals and/or have field distributions associated with damp or shaded locations where water relations may be important (Grime et al. 1988). The circumstantial evidence is that variation in Gulf Stream position is associated with changes in the relative abundance of components of the vegetation. Because these differ in phenology and rooting depth, moisture supply appears to be implicated, though the precise mechanism is unclear. Large-scale changes in atmospheric circulation are known to affect both the position of the Gulf Stream and the weather in the United Kingdom. However, it has been suggested by Taylor and Stephens (1980) that displacement of the Gulf Stream may directly influence the movement of cyclones across the North Atlantic and hence affect the frequency of anticyclones to the west of the UK (Taylor 1995a). Clearly, both of these actors may affect rainfall patterns. To test this assertion, we examined relations between Bibury weather and Gulf Stream position (see legend to Fig. 1). The relation for local atmospheric pressure appears in Fig. lc, showing that high pressure is clearly related to northward displacement. Analyses also confirm, as expected, that high pressure is associated with higher mean temperatures, more sunshine hours, and lower rainfall. We conclude (a) that the overall productivity of Bibury vegetation and the performance of certain individual spe-

Linking plant strategies and plant traits derived by radiative transfer modelling

Question Do spatial gradients of plant strategies correspond to patterns of plant traits obtained from a physically based model and hyperspectral imagery? It has been shown before that reflectance can be used to map plant strategies according to the established CSR scheme. So far, these approaches were based on empirical links and lacked transferability. Therefore, we test if physically-based derivations of plant traits may help in finding gradients in traits that are linked to strategies. Location A raised bog and minerotrophic fen complex, Murnauer Moos, Germany. Methods Spatial distributions of plant traits were modelled by adopting an inversion of the PROSAIL radiative transfer model on airborne hyperspectral imagery. The traits are derived from reflectance without making use of field data but only of known links between reflectance and traits. We tested whether previously found patterns in CSR plant strategies were related to the modelled traits. Results The results confirm close relationships between modelled plant traits and C, S and R strategies that were previously found in the field. The modelled plant traits explained different dimensions of the CSR-space. Leaf Area Index (LAI) and the reciprocal of Specific Leaf Area appeared to be good candidates for reproducing CSR scores as community traits using remote sensing. LAI has not been used in previous studies to allocate plant strategies. Conclusions Combining RTMs and the CSR model is a promising approach for establishing a robust link between airborne or spaceborne imagery and plant functioning. The demonstrated potential to map traits with close relation to CSR gradients using only our understanding of the relation between traits and reflectance is a step forward towards an operational use of the CSR model in remote sensing. This article is protected by copyright. All rights reserved.

First Group: Ecological Attributes

For most species only one set of data is given. However, in the case of individual trees and shrubs ecological attributes are, wherever possible, presented separately for seedlings and small saplings, juveniles, and for the more mature individuals which contribute to the canopy.

Explanation of Tables

Nomenclature follows that of A. R. Clapham, T. G. Tutin and E. F. Warburg’s Excursion Flora of the British Isles (3rd. edn), published by Cambridge University Press in 1981, except for the following species groupings: Betula spp. (includes B. pendula, B. pubescens and their hybrid), Festuca ovina (also includes F. tenuifolia), Festuca rubra (also includes F. nigrescens), Lolium perenne (refers only to ssp. perenne; the monocarpic, and introduced, ssp. multiflorum (Lam.) Husnot is a non-persistent escapee from cultivation), Medicago sativa (excludes ssp. falcata (L.) Arcangeli which is native in East Anglia), Nasturtium officinale agg. (N. microphyllum, N. officinale and their hybrid), Poa pratensis agg. (P. angustifolia, P. pratensis sensu stricto and P. subcaerulea), Quercus agg. (Q. petraea, Q. robur and their hybrid), Rosa spp. (R. canina group, R. rubiginosa group and R. tomentosa group), Salix cinerea agg. (S. aurita L., S. caprea, S. cinerea and hybrids), Salix fragilis agg. (S. alba L., S. fragilis L. and related hybrids) and Taraxacum agg. (Section Erythrosperma, Section Obliqua, Section Palustria, Section Spectabilia and Section Taraxacum).