THE GROWTH OF SPHAGNUM: EXPERIMENTS ON, AND SIMULATION OF, SOME EFFECTS OF LIGHT FLUX AND WATER-TABLE DEPTH

(1) Experiments were made to determine the effects of both shading and of water-table depth on the growth of three species of Sphagnum. The species (and their usual habitats) depth on the growth of three species of Sphagnum. The species (and their usual habitats) were: S. capillifolium (hummocks); S. paillosum (lawns); and S. recurvum (pools and flushed lawns). 

(2) Water-table depth had little effect on growth measured as increase of dry matter; shading reduced growth and there were specific differences associated with plant size. There were no significant interactions between water-table depth and shading. 

(3) For growth measured as growth in length, there were highly significant interactions, individual species behaving differently in response to shade and, to a lesser extent, in response to water-table depth. 

(4) In Sphagnum lawns in two natural habitats there was a negative correlation between depth of the water-table and surface-roughness. In experimental conditions surface-roughness increased both as the water-table was raised and as shade increased. 

(5) A computer simulation of growth of Sphagnum in a lwan was able to reproduce the observed variations in surface roughness. In mixed lawns of two species, the one in its 'natural' habitat out-grew the other.