Phenology of Selected Bryophytes in Southern Illinois

Abstract

Maturity indices of Atrichum angustatum (Brid.) B.S.G., Diphys- cium foliosum (Hedw.) Mohr, Trichocolea tomentella (Ehrh.) Dum., Nowellia curvifolia (Dicks.) Mitt. and Lophocolea heterophylla (Schrad.) Dum. popu- lations in southern Illinois are discussed. Indices are based on biweekly ob- servations made over a period of a year and are correlated with vapor pressure deficit, temperature, light quality and quantity and daylength. Depending upon the species, these microenvironmental factors variously affect the veg- etative growth, gametangial formation, fertilization and subsequent growth of the sporophytes. Moisture conditions seem most critical to vegetative growth and survival, and photoperiodism seems to be the dominant factor in gametangia formation. Lophocolea is apparently a day neutral plant in ref- erence to gametangia formation while Diphyscium, Atrichum and Trichocolea are long day plants. Gametangia in Nowellia are also formed under long day conditions but their formation, once initiated, is continuous until dessication of the population. Environment can explain only in part a plant's occurrence in a particular habitat. How a plant responds, both vegetatively and sexually, to climatic and edaphic con- ditions may be as important. Since many bryophytes become dormant during part of the year, their microclimates can reflect both growing and dormancy conditions. Tim- ing of sex organ maturation and spore or gemma release also regulates a species introduction and survival at a particular site. The importance of such growth and reproductive responses to the distribution, radiation potential and evolution of bry- ophyte species necessitates understanding the relationship between phenology and seasonal microclimatic variability. Unfortunately, few such studies exist. Greene (1960) presented an account of gametangial and capsular cycles in six mosses. While pointing out some of the difficulties one may encounter in phenological studies, he also demonstrated the presence of three different sporophyte maturation stages in mosses. Forman (1965), utilizing 103 species from a single Wisconsin loca- tion, presented another system for studying moss phenology which is more simplified than Greene's. Other recent phenological studies of mosses include those by Johnsen (1969) on Orthotrichum anomalum Hedw., Clarke and Greene (1970) on Pohlia nu- tans (Hedw.) Lindb. and P. cruda (Hedw.) Lindb. and Hancock and Brassard (1974) on Buxbaumia aphylla Hedw.