Environmental Engineering Reference
In-Depth Information
teaching on the calibration of yield tables. The yield table concept is the quantitative
basis of modern forestry.
One significant observation found in yield tables is that the rate of mortality of
trees in stands undergoing natural thinning is highest in stands with the highest site
indices. Faster growing trees suppress their competitors at a higher rate than slower
growing trees on low site-index locations. The trade-off between rapid tree growth
versus high mortality on good sites is the basis of the development of thinning
strategies for managed stands and for schemes to plant forest plantations at particu-
lar spacing of trees. Despite their elevated mortality, sites with high site indices are
more productive than low site-index locations.
Nachhaltigkeit was fueled by social unrest. It resulted in laws and regulation
based on scientific research and experimentation with inspiration stemming from
a shared political necessity to better manage the forests of Europe. Nachhaltigkeit
was also the origin of the initial use in English of the word, sustainability. Its
development into modern forestry practice was an ongoing process that continues
today. Modern forestry is significant in sustainability science as a first real-world
application. Modern forestry and its Nachhaltigkeit origins also represent a model
of Gleasonian approaches to forest dynamics into sustainability science. It focuses
on individual organisms and their relationships with one another and with their
environment. One of the significant implications is that quantitative ecology and in
particular, ecological models, likely could have a significant role in sustainability
science. Individual-based vegetation dynamics models have a logical intellectual
inheritance from forestry studies and are an example of tools for the application of
Gleasonian successional concepts. These are the topics of the next section.
Individual-Based Models: Computer Descendants
of Gleasonian Succession
Currently, several factors are simultaneously arising that challenge the application
of successional theory in sustainability science. Climate conditions are changing,
perhaps with a greater rate of change than seen in the past [
53
]. The carbon
dioxide composition of the atmosphere has been altered by human activities with
potential effects on plant processes particularly photosynthesis and the efficiencies
of plant water-use [
54
]. This issue was addressed several decades ago by foresters
who realized that the elaborate calibrations used to develop long-term data on
forest change were subject to less accurate predictions if selected genetic strains of
trees were used, if forests were fertilized or if there were significant variations in
climate.
Impressed by the power of computers and interested in developing
a methodology to use highly detailed computer models to simulate the spatial
relations among thinning of trees, tree growth, and spatial arrangement of trees,
foresters developed individual-based dynamic models of forests (mostly for
