Demographic Patterns of Seedling Establishment and Growth of Native Graminoids in an Alaskan Tundra Disturbance

Publisher Website
Google Scholar
Abstract
The presence or absence of buried seed was the major factor governing natural revegetation of a bulldozed disturbance in Alaskan tussock tundra. The viable buried seed pool contained 97% Eriophorum vaginatum and Carex bigelowii seed and was restricted to organic soil horizons. Consequently, disturbed organic soils reached a final seedling density of 250 seedlings m-2 (primarily Carex and Eriophorum) 4 yr after disturbance; mineral soils which were colonized by current seed deposition had only 30 seedlings m-2, including many grasses. Fertiliztion enhanced the growth of grass and 2.sbd.4-yr-old Carex seedlings 4- to 10-fold but had no significant effect upon Eriophorum seedling growth. Growth was not significantly affected by presence of already established seedlings and did not differ between substrates, except for grasses which grew more rapidly on mineral than organic soils. Seedling mortality during the first 2 yr after germination was low (43% in Eriophorum, 27% in grass and 13% in Carex) and did not differ between organic and mineral substrates. Mortality of 1- and 2-yr-old seedlings was concentrated during the growing season, but mortality of larger seedlings was primarily a consequence of winter grazing. Mortality was increased by fertilization. The greater vascular plant biomass and cover on organic than mineral soils was due primarily to recruitment from the buried seed pool. The increase in biomass and cover with fertilization was a consequence of a stimulation of growth by grass and Carex. Stockpiling and re-using soil organic matter are recommended, supplemented under certain conditions by fertilzation and sowing of seeds, as a mechanism of enhancing natural community restoration of arctic tussock tundra following man-made disturbances.