Calculation of initial biomass in Biomass Succession extension

[jiangt...@gmail.com]

Hi,

I'm using LANDIS-II Biomass Succession to simulating middle-old temperate forest.

I basically understand one species' biomass in a cell is based on the relationship between age and maxbiomass, shade, morality rates and so on. I have a question about how to calculation of initial biomass in Biomass  Succession extesnion. For example,  if one speices in a cell (or mapcode) have three age-cohort (e.g, 10, 70, 120), because there is no tree numbers of each age-cohort, I want to know whether biomass calculated of this species in this cell  is averagely allocated to each age-cohort. If it's not, how the biomass caluculated of this species is allocated to each age-cohort. In other words, how much biomass of each age-cohort is occpied to the total biomass of this species in this cell?

Thank you for your help,
Cheers

Jiangtao Xiao

[Robert Scheller]

Jiangtao,

Each cohort is 'planted' and grown for the duration of their age during Biomass Succession spin-up.  So, in your example, the 120 year old cohort is established first and grows without competition for 50 years until the 70 year old cohort is added.  Next they compete for growing space for 60 years until the 10 year old cohort is added.  And finally all three cohorts compete for growing space for the final 10 years.  Therefore, even if all cohorts are of the same species, they are still competing for growing space.  The larger and older cohort will have an advantage for a time up until it starts to decline due to age-related mortality.

Cheers,

Rob

[Robert Scheller]

A user asked:

'However, there is still some questions bothering me. In the example mentioned, because there is no stand denstiy information about each age-cohort (e.g, 10, 70, 120), so I have an question that whether there is an assumption that stand density of each age-cohort is same in a cell or mapcode in Biomass Succession extension. Further, I want to know how the percentage of biomass of different age-cohort in a cell is determined.'

Indeed, there is absolutely no stand density information provided or inferred. Biomass Succession does not calculate or use stand density in any way shape or form.  And so there are no assumptions regarding stand density either.

During spin-up, each cell is run - without disturbance - for a duration equal to the age of the oldest cohort .  And so the biomass of each cohort at time zero reflects simulated succession and is therefore determined by cohort age, potential growth rate, and competition.  

Rob