Environmental Engineering Reference
In-Depth Information
and as intermediaries to facilitate idea generation and
negotiation of alternative solutions for management on
US National Forests.
for south-western Alaska and the Acadian Region are
currently being constructed.
23.5.2 TreeGrOSSandBWinPro
23.5 Example model
Forest-growth modelling in Europe also continues to
progress along parallel tracks. One well-used modelling
framework is TreeGrOSS, an open-source software
framework for developing forest-growth models (Tree-
GrOSS, 2011). One instance of the framework is the
silvicultural decision support system BWINP ro (Nagel
and Schmidt, 2006). Additional models and uses are
described in Hasenauer (2006).
23.5.1 Forest-vegetationsimulator (FVS)
The FVS grew out of the original PROGNAUS model of
Stage (1973) and is now available throughout the entire
US (FVS, 2011; Crookston and Dixon, 2005). Currently,
there over 20 different FVS variants and each is calibrated
to a specific geographic area of the US. The basic FVS
model structure has been used to develop growth models
in British Columbia (Temesgen and LeMay, 1999) and
Austria (Monserud et al ., 1997). All FVS variants are
empirical distance-independent, individual-tree growth-
and-yield models, but differ in the equation forms used
due to differences in regional data availability. The model
uses a temporal step of 5 to 10 years and can be used for
simulations that last for several hundred years. To predict
growth accurately, the FVS uses separate equations for
large (
23.6 Lessons and implications
23.6.1 Modelscanbeuseful
Models of various kinds have been very useful to forest
management for a long time. The most basic models
provide at least an estimate of how much timber is avail-
able and what it may be worth on the market, so that
managers can determine economic feasibility of timber
cutting. More sophisticated modelling techniques provide
better estimates of timber, include other forest charac-
teristics, and project likely developments into the future.
Reliability of empirical models tends to be restricted to the
current generation of trees, for which they are very good.
Other forest-growth models use ecological and
physiological principles to make projections of growth.
Theoretical, mechanistically based models tend to be
better for general pictures of forest characteristics in
a more distant future projection, but may be less
reliable for near-term forecasts. They tend to require
more data than managers are capable of collecting for
extensive tracts, and thus are often restricted to use in
scientific research contexts, rather than management
decisions directly. Still, such research-orientated models
are still very useful in the long term, as they help
increase understanding of the system and direct further
investigations. Hybrid models have attempted to bridge
the gap between mechanistic and empirical models.
With greater and greater computing power in recent
years, modelling techniques have expanded to include
spatially explicit models of landscape-level change. These
models now help provide the context in which a stand-
level forest-management decision is made, giving a man-
ager a better understanding of the implications one action
has on other areas. Positive effects are being seen in wildlife
127 mm DBH).
The diameter growth of large trees is driven by current
tree DBH, whereas growth of small trees is primarily a
function of their current height. Mortality is sensitive to
variant- and species-dependent estimates of maximum
stand density index (SDI). The model can simulate the
influence of a variety of forest management activities such
as harvesting, site preparation, thinning, and fertilization.
The model can handle planted regeneration, but some
variants do predict the amount of natural regeneration
(Robinson and Monserud, 2003). The model will self-
calibrate if tree-height or growth-measurement data are
available.
Several extensions to FVS exist (see Crookston and
Dixon, 2005). The extensions can represent the influence
various disturbance agents such as western spruce bud-
worm and mountain pine beetle. One of the widest used
extension is the Fire and Fuels Extension (Reinhardt and
Crookston, 2003), which is used to estimate tree-level
biomass and the influence of fire on growth and mor-
tality. Recently, a climate-sensitive variant of FVS was
developed to address the expected influence of climate
change on tree growth and mortality (Moscow Forestry
Sciences Laboratory, 2011; Crookston et al ., 2010). The
FVS interface is a Microsoft Windows-based program
that allows for batch runs and file-based inputs. The
model has been linked with external programs like SVS
and LMS, and continues to be developed as new variants
>
127 mm DBH) and small trees (
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