Current Vegetation Changes in Western Europe

In a comparative discriminant analysis of the functional traits of increasing and decreasing species in the vascular plant floras of the British Isles, The Netherlands, and West Germany (Thompson, 1994), three main conclusions have been drawn:

1. A key measure discriminating between increasing and decreasing species is S radius. 5 radius is a measure of proximity to the stress-tolerant corner of a CSR strategic triangle of plant functional types (Grime, 1974; Grime et al., 1988); a large S radius is correlated with low growth rate, low rates of tissue turnover, and low mineral nutrient requirements. In densely populated England, the Netherlands, and to a lesser extent, West Germany, decreasing species are stress-tolerators (large Sradius), whereas increasing species are fast-growing and typical of eutrophic, disturbed habitats.

2. In the sparsely populated northern and western regions of the British Isles differences between "winners" and "losers" are very slight.

3. Surprisingly, regenerative attributes (seed weight, seed persistence in soil, wind dispersal) are very poor predictors of success and failure in the modern northwest European landscape.

The same sources are used in Fig. 1 to plot the mean S radius of increasing and decreasing species against human population density in seven European countries. Thompson's (1994) interpretation of these results accords with an earlier hypothesis of Hodgson (1986a,b) in suggesting that in the densely populated countries of Western Europe, land use is increasingly polarizing the flora into two parts. The successful, fast-growing part is tolerant of human activities and is ecologically attuned to intensively managed grassland, arable fields, road verges, gardens, spoil, and urban waste-

S radius of increasing and decreasing 2.5 species

10 100 1000 Human population density (per sq. km)

Figure 1 Relationship between mean S radius of increasing and decreasing species and human population density in seven European countries. S radius of the two groups is not significantly different in Scodand, N. Ireland, or Wales. The two groups are significantly different in Republic of Ireland (P = 0.049), England, western Germany, and The Netherlands (all P< 0.001).

i Decreasing species . Increasing species land. Because these habitats are common, and because soils, seeds, and plant fragments are moved freely between them by human agencies, these plants are highly mobile, rapidly colonizing new sites as they become available. Species of this type will have little difficulty in migrating in response to land use change. In contrast, the slow-growing, stress-tolerant part of the flora, typical of unimproved grassland, lowland heath and old woodland, is increasingly excluded from the wider landscape.

How will rising C02 influence these vegetation changes resulting from land use? Has responsiveness to C02 concentration already played a significant role in the promotion of fast-growing, resource-demanding species in intensively developed landscapes? To address these questions it is necessary to consider our present understanding of how different types of plants respond to elevated C02.

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  • tyler
    What is europe's main vegetation changes?
    7 years ago

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