Life-history theory and management - Ecological Applications: Toward a Sustainable World - page 62

which species will do well. Let's consider examples of agricultural restoration where
the end-points are very different - species-rich grassland (Section 3.2.1) or forest
(Section 3.2.2).

3.2.1 Restoring
grassland plants - a
pastoral duty

Undisturbed native grasslands are actually quite rare, most having been converted
to an unnatural state by pastoral farming or agricultural development. Thus, the
restoration of native grasslands has become a priority.
The fi rst study of any ecological phenomenon provides just so much new informa-
tion that it is risky to derive general conclusions that go beyond the focal organisms
and sites. As science progresses, however, studies accumulate in the scientifi c litera-
ture until a more effective search for generalizations can be made using a 'meta-
analysis'. Pywell et al. (2003) assembled the results of 25 published experiments
dealing with the restoration of species-rich European grasslands from land that had
previously been 'improved' for pasture (ploughed, planted with pasture species and
fertilized) or used for arable farming. Restoration involved sowing a range of desir-
able species into areas where agricultural intensity had been reduced. The idea was
to relate the performance of different species to their life-history traits. On the basis
of the results of the fi rst 4 years of restoration, they calculated a performance index
for commonly sown grasses (13 species) and forbs (45 species; forbs are defi ned as
herbaceous plants that are not grass-like). The index, calculated for each of the 4
years, was simply the percentage of quadrats (0.4

0.4 m or larger) originally sown
with a species that still retained it. Their life-history analysis included 38 plant
traits, including longevity of seeds in the seed-bank, seed viability, seedling growth
rate, Grime's life-history strategies (C, S or R - Box 3.1), and the timing of life-cycle
events (germination, fl owering, seed dispersal).
The best performing grasses include Festuca rubra and Tr i se t u m fl avescens (per-
formance indexes averaged for the 4 years of 77%); and among the forbs, Leucanthe-
mum vulgare (50%) and Achillea mellefolium (4 0%) are particularly successful. In fact,
grass species in general do better than forbs in restoration attempts, but for grasses
only ruderality (R) is positively correlated with performance. With the forbs, on the
other hand, good establishment is linked to colonization ability, percentage germi-
nation of seeds, autumn germination, vegetative growth, seed-bank longevity and
habitat generalism. Interestingly, competitive ability and seedling growth rate
become increasingly linked with success as the intensity of competitive interactions
increased with time (Table 3.1). Stress tolerators, habitat specialists and species of
infertile habitats perform badly, partly refl ecting the high residual nutrient availabil-
ity in many restored grasslands.
Pywell's team notes that restoration effi ciency could be increased in future by
only sowing species with the identifi ed ecological traits. However, because this
would lead to uniformity among restored grasslands, they also suggest that desirable
but poorly performing species could be assisted by phased introduction several years
after restoration begins, when environmental conditions are more favorable for their
establishment.

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3.2.2 Restoring
tropical forest -
abandoned farmland
reclaimed for nature

Surprisingly large areas of the tropics now consist of abandoned agricultural land.
Close to the Panama Canal, for example, most of the biodiverse tropical forest had
been cut and burned to open up land for subsistence agriculture by the mid 1980s.
Small farms were quickly abandoned, however, probably because of low productiv-