Abstract
Predicting the effects of nature restoration requires the setting of targets. Recently a system of 'nature target types' (natuurdoeltypen) has been developed. This system is based on the ranges of important abiotic conditions in which at least 40% of the target plant species characteristic of each target type occurs. The abiotic conditions considered are soil humidity, nutrients (nitrogen) and pH. A few species make up the bulk of plant communities in terms of abundance or biomass, and their dynamics may be best described by resource partitioning (niche differentiation) mechanisms. Hence, their distribution may be predicted by ranges of the main resources moisture, nutrients and pH. Being dominant species, their dispersal is not likely to be a limiting factor for establishment in target areas, and therefore can be reliably predicted. AII other species however, making up the bulk of the biodiversity including many target species, are tar less abundant and depend largely on chance processes of dispersal, arrival and establishment. This makes prediction for establishment in target areas and hence for nature restoration difficult. Together the mechanisms of resource partitioning and species dispersal should define target communities and their characteristic target species. Coming from the species end, several trade-offs are reported to exist between life cycle traits in plants: e.g. the capacity of a seed to disperse to a certain extent negatively related to its capacity to survive in a dormant state which in its turn is negatively related to adult lifespan. Long adult lifespan usually is associated with lower colonization ability etc. Each of these traits has a distinct effect on the dynamics of plant species in spatially fragmented populations: Dispersal capacity determines the ability to colonize new sites, dormancy determines the capacity to recolonise the same site and longevity determines the capacity to keep a site occupied and to function as a seed source. Altogether this project aims at: 1) Improving our understanding of the dynamical relationship (in terms of succession and substitution) between local species composition and local abiotic state factors based on hierarchical national land unit and vegetation classification systems, by using over 300,000 spatially defined descriptions of plant communities. It will be examined separately for constantly present dominant and for infrequently present transient species. 2) Establishing the species pool in two specific regions by pooling the species in certain habitats/communities. This analysis will be based on the recently published vegetation tables on the nation al vegetation classification and on the coordinates of all the aforementioned vegetation descriptions. The thus assembled species pools refer to well defined target communities including target species for nature restoration. 3) Establishing the dynamics of target species by comparing pre-1976 vegetation descriptions (over 30,000) with later descriptions. This provides an estimation of the mobility of species. 4) Quantifying spatio-temporal dynamics of plant species from large, spatially defined unique databases compiled from vegetation surveys and 9,000,000 records of 1902-1999 on flora inventories. 5) Quantifying the trade-offs in the three life cycle traits (dispersal capacity, dormancy, adult longevity) from plant species data bases and from additional measurements, in a phylogenetically correct way. 6) Relating trait patterns (mobility strategies) to spatio-temporal dynamics.
Netherlands