On the Ecology of Mountainous Forests in a Changing Climate: A ...

148 Chapter 5
W U Michigan
(E/P)
250
Ulmus spp.
200
Tsuga canadensis
Thuja, Juniperus, Larix
Biomass (t/ha)
150
100
Quercus spp. (N)
Populus spp.
Pinus strobus
Pinus spp.
Picea mariana/rubens
Picea glauca
50
Fagus grandifolia
Betula spp.
Acer spp.
0
0
400
Year
800
1200
Abies spp.
Fig. 5.11: Simulation results from FORCLIM for Western Upper Division, Michigan.
grandifolia, which in reality is subject to considerable drought stress here, and Quercus
macrocarpa (making up most of the northern oaks in Fig. 5.11), a very fire resistant and
relatively shade intolerant species which is more typical of the oak savanna towards the
prairie-forest border of Minnesota and Wisconsin.
The increase of both species diversity and total above-ground biomass simulated by
FORCLIM appears to be realistic (DeAngelis et al. 1981), and the species composition
simulated by this model agrees more with the descriptions of near-natural forests of the
area (Rowe 1972, Küchler 1975, Frelich & Lorimer 1991) than the FORENA simulations
(Solomon 1986).
NORTHERN AND SOUTHWESTERN DECIDUOUS FOREST
Fig. 5.12 gives an overview of the steady-state species composition along a gradient
from the northern to the southwestern deciduous forests; the climate is characterized by
strongly increasing temperature and precipitation, but at the same time also increasing
drought stress. The forest simulated at Central Lower Michigan (Fig. 5.12) is in the
transition zone from the sugar maple-eastern hemlock forests typical of locations in the
north (Fig. 5.11) to the oak-hickory forests characteristic of locations further south
(Fig. 5.12 & 5.13). Comparing these results to the ones from Western Upper Michigan