Current and emerging threats to trees and forest ecosystems require a re-evaluation of the
way forest genetic resources are managed. Governments in the United Kingdom and
elsewhere are committed to the restoration, expansion and creation of new woodlands. Tree
populations are often adaptively differentiated from one another, so a key question
underpinning the success of planting schemes is the choice of seed origin. A long held
understanding is that locally sourced seeds will have the best opportunity to tolerate
conditions of the planting site (local provenancing). However, the rate at which the
environment is changing introduces a great deal of uncertainty into decision making and
there is concern that climate change is proceeding at rates faster than those with which
locally adapted trees would be able to cope. As such, there are suggestions that seed
collected from areas already experiencing the anticipated future conditions will improve the
adaptability of forests (predictive provenancing). This thesis investigated outstanding
questions relating to the merits of the local provenancing and predictive provenancing
approaches, and the practical implementation of seed sourcing policy in British forestry.
The validity of existing seed zone boundaries used under local provenancing was analysed
for ancient semi-natural Scots pine Pinus sylvestris L. forests of Scotland. Vegetation description and analyses of climatic covariates revealed that the existing series of seed zones
used to guide selection of planting stock for restoration do not necessarily environmentally
match seed sources to planting sites under current conditions. Additional disparity is
introduced when edaphic variation (or proxies for this) is considered.
To determine whether future adaptation under local provenancing may be restricted by
limited pollen flow among populations of native Scots pine in Scotland, the timing of pollen
production in five populations was estimated by repeatedly measuring strobilus development
on a series of twenty trees over three consecutive springs. Differences in the mean predicted
date of pollen production were found, with populations in the warmer west shedding pollen
earliest each year, although the timing and differences in timing among populations varied
from year to year, with shedding taking place earliest in the warmest of the three years and
latest in the coolest year.
A theoretical multi-patch, ecological genetic individual-based model (IBM) was developed
to investigate the utility of different seed sourcing strategies (local versus non local
provenance) and their capacity to help populations adapt to directional climate change. As
well as being adapted to climate, which varied in a clinal pattern, individuals also had to be
well adapted to the habitat conditions of the planting site in order to survive hard selection at
the seedling stage. The model showed that population size of a new planting was reduced
when planting stock adapted to the future conditions but not to current conditions was
deployed. The differences were most severe when selection acted simultaneously on both the
climate-related and the habitat-related phenotype.
Finally, a series of in-depth qualitative surveys conducted with members of the domestic
forest nursery and seed supply sector in Great Britain found that there are many difficulties
associated with seed sourcing and the supply of trees. These problems arise due to a very
limited ability to predict demand at the time of seed sowing, and lead to waste when demand
is overestimated and importation of planting stock when demand is underestimated.
Confidence and competitiveness in the domestic sector could be greatly improved by
updating seed sourcing guidelines and by simplifying certain aspects of the process by which
forest planting projects are funded