The Phenology, Growth and Ecosystem Dynamics of Erythronium americanum in the Northern Hardwood Forest

In the northern hardwood forest, growth of vernal photosynthetic herbs is temporally restricted to the period between spring snowmelt and summer canopy development. This characteristic suggests that several unique adaptations exist which allow the species to complete their life cycles, and that temporal separation of production in the herbaceous layer may add to structural and functional complexity of the ecosystem. Erythronium americanum Ker. (Liliaceae) was examined in central New Hampshire with respect to its natural history, growth characteristics and influence on energy flow and mineral cycling in the deciduous forest ecosystem. Growth leading to the early spring development of photosynthetic tissue begins with fall root growth and continues through a long winter phase during which the shoot elongates from the perennating organ, through the soil and into the snowpack. Following snowmelt, the shoots begin rapid unfurling and maturation of the photosynthetic tissue. The length of the mature leaf phase is controlled by the timing of snowmelt and canopy development, and may be quite variable between successive years. During the short period of production, total biomass increased by 190% in 1972 and 338% in 1973; however, plant weight at the end of the winter period in 1973 had decreased to 28% of the spring 1972 maximum. In the annual energy cycle, biomass losses during the nonphotosynthetic period may amount to more than production during the preceding spring. In comparison with summer green herbs, Erythronium shoot tissue contained significantly higher concentrations of N but lower levels of K, Mg and Ca, suggesting that the spring adaptation may be oriented toward higher N levels of the soil during the spring period as well as higher light levels at the forest floor. Significant correlations of biomass of vernal photosynthetic herbs with summer green species imply that temporally separated species may utilize the same physical site and resources. This adds to the structural complexity and production of the herbaceous layer; however, the vernal photosynthetics account for only 0.5% of total aboveground primary production of the ecosystem. The temporal character of Erythronium's growth and its capacity for rapid biomass accumulation combine to make it a significant factor in nutrient dynamics in the deciduous forest. Uptake of N and K during spring flushing of nutrients from the ecosystem and later release through senescence of shoot tissue appear to reduce gross ecosystem losses of these elements.