Ecological Archives M071-008-A3

P. R. Moorcroft, G. C. Hurtt, and S. W. Pacala. 2001. A method for scaling vegetation dynamics: the ecosystem demography model (ED). Ecological Monographs 71:557-585.

Appendix C. Plant Functional Diversity.

The functional type vector ${\bf x}_{}$ defines the characteristics of each plant functional type. It is comprised of two elements $\left[x_1,x_2\right]$. The first $x_1$ is discrete, specifying C$_3$ or C$_4$ physiology. The second $x_2$ is continuous, denoting the leaf life-span (yrs) of the plant type. The other physiological characteristics of the plant type are specified from its leaf life-span using the relationships shown in Fig. A.1. We use the Reich et al. (1997) regressions shown in left-hand panels of Fig. A.1 to specify the relationship between leaf longevity $x_2$ of the plant functional type and its specific leaf area (m$^2$ kgC$^{-1}$): $l({\bf x}) = 16.0 x_2^{-0.46}$ and leaf carbon-to-nitrogen ratio (g g$^{-1}$): $\mbox{(C:N)}_a=27.8x_2^{0.34}$. In addition to these physiological relationships, we specify two further relationships also shown in the two right hand panels of Fig. A.1 that define two attributes of plant structure. The first is an association between leaf-longevity and the wood density of the plant functional type (g cm$^{-3}$) $\rho({\bf x})= \mbox{max}(0.5,0.5 + 0.2(x_2-1))$, the second is an association between leaf longevity and maximum height (m) $(x_2 < 1: h_{max}= 0.75, x_2 \ge 1: h_{max}= 35$.

Together with these relationships, the functional type vector ${\bf x}_{}$ specifies the physiological and life-history characteristics of a continuum of plant functional types. For the four functional types used in this paper, the values of the functional type vector ${\bf x}_{}$ are: C$_4$ grasses ($x_1=$C$_4,x_2=0.5$), early successional trees ($x_1=$C$_3,x_2=1.0$), mid-successional trees ($x_1=$C$_3$,$x_2=2.0$), and late successional trees ($x_1=$C$_3,x_2=3.0$).

a	b
c	d

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