302 WHITTAKER AND LIKENS 



substitution of an immature for a mature stand can increase the net annual 

 productivity of the biomass. 



Whittaker: There are circumstances in which it is true that the unstable 

 stand has the higher production than the stable and some circumstances in which 

 it is not true. 



Woodwell: Could the flux of net primary production into humus balance 

 the loss of standing crop of biota? 



Whittaker: It might, but I expect the humus to be in some kind of steady 

 state governed not so much by the biomass of the forest as by the input of 

 foliage and branch litter as opposed to decay rates. I do not think that the 

 reduction of forest biomass could be compensated for by an equivalent increase 

 in litter biomass. 



Reiners: Forests grow in most years — there is always a true increment, as 

 Rodin and Basilevich have expressed it, so that biomass increases in a logistic 

 curve. However, harvesting in forests is very often catastrophic even in 

 nonhuman situations, and, although there will always be a true increment, every 

 200 or 300 years it is all going to go back down again. So, when productivity in 

 forests is measured on a year-by-year basis, forests seem to be continually 

 growing. The impression is misleading unless one takes into account that trees 

 are blown down, burned, or cut. 



