118 



PLANT SUriOLOdY 



Schroter (1926) has discussed the autecological effects of snow and 

 given a careful survey of the literature. Extensive accounts have also 

 been given by Fries (1913), Braun-Blanquet (1913), and Nordhagen 

 (1928). Schroter groups the effects of snow according to its benefits 

 and its harm to vegetation. 



He recognizes as beneficial the protection from drought, from cold, 

 and from early sprouting; the retention of heat in the soil favoring the 

 spring flora; the increase of the sun's heat by reflection; the promotion 



Fig. 65. — Disintegration of the Rosmarinus-LUhospermum frutUoii. >! . 



Heavy rains have exposed the root system of Rosmarinus, Genista scorpim;, and Lacan- 

 dida latifolia. (Photo by Braun-Blanquet and Keller.) 



of fertility by collecting and retaining dust; the regulation of the water 

 supply by gradually melting; and the providing of smooth surfaces for 

 the distribution of seeds by the wind. 



Injurious effects are the abrasive action of particles driven by the 

 wind; the formation of a cold danger zone on the surface of the snow; 

 the shortening of the vegetative period due to the snow cover; mechan- 

 ical injury due to weight and sliding; and the favoring of soil washing 

 and soil sliding. 



To these harmful effects should be added the deformation of woody 

 plants by snow pressure and breakage as well as physiological injury, 

 reducing vitality, especially of the taller woody plants. 



