The effect of roots and litter of Calamagrostis canadensis on root sucker regeneration of Populus tremuloides

Marsh reed grass (Calamagrostis canadensis (Michx.) Beauv.)is a common, highly competitive grass native to the boreal mixedwoodforest. This grass increases in abundance after clear-cut loggingbut little is known about its effects on trembling aspen (Populustremuloides Michx.) sucker regeneration. The effects of Calamagrostissod and its litter on aspen regeneration were studied in twoseparate greenhouse studies. Calamagrostis sod did not affectthe initiation of suckers, but resulted in 30 per cent fewersuckers emerging above the soil that were smaller and had 40per cent less leaf area. Calamagrostis litter had little effecton the initiation and number of emerged suckers; however, itdelayed emergence by 10 days. The physical barrier by rootsand litter of Calamagrostis reduced or delayed the expansionof suckers and therefore prolonged their dependence on rootreserves. By the time the suckers reached the surface, theyhad to compete for light with Calamagrostis shoots that hademerged a week earlier. This, coupled with low soil temperaturesassociated with Calamagrostis in other experiments, will significantlyreduce the number and growth of suckers. Any reduction and delayin sucker emergence will decrease aspen regeneration and productivitysince the growing season in the boreal forest region is short.