Ecological Archives M071-008-A6

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 F. Mortality.


The total mortality of plants is calculated as the sum of two terms

$\displaystyle \mu({\bf z},{\bf x},{\bf r},t)= \mu_{DI}+\mu_{DD}$     (F.1)

The first component is an individual's density-independent mortality rate $\mu_{DI}$ (yr$^{-1}$) which is a linear function of it's wood density

$\displaystyle \mu_{DI}=0.014 + 0.15(1-\frac{\rho({\bf x})}{\rho({\bf x}_{LS})}),$     (F.2)

where $\rho({\bf x}_{LS}) =0.9$ is the wood density of the late successional functional type. This function gives longevities consistent with empirical estimates, ranging from 15 years for the early successional tree type (Uhl and Jordan 1984) to 75 years for the late successional tree type (Lugo and Scatena 1996; Swaine et al. 1987). In the PDEs, we partition the $\mu_{DI}$ term into two pieces. The disturbance portion is

$\displaystyle \lambda_{DI}(a,t) = 0.014$     (F.3)

and the density independent mortality portion is:

$\displaystyle \mu_{DI}({\bf z},{\bf x},\bar{{\bf r}},t)=0.15(1-\frac{\rho({\bf x})}{\rho({\bf x}_{LS})}).$     (F.4)

The second mortality component is an individual's density-dependent mortality rate, which depends on the plant's current net carbon production ( $\mbox{Prod}_{}$ from the previous section) relative to what it would be in full sun ( $\mbox{Prod}_{FS}$):

$\displaystyle \mu_{DD}=\frac{m_1}{1+e^{(m_2 \frac{\mbox{Prod}_{}}{\mbox{Prod}_{FS}})}}$     (F.5)

where $m_1=5.0$ and $m_2=10$.


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