Carbon dioxide and submersed macrophytes in lakes: linking functional ecology to community composition.

Evaluating plant community response to atmospheric CO rise is critical to predicting ecosystem level change. Freshwater lakes offer a model system for examining CO effects as submersed macrophyte species differ greatly in their growth responses to CO enrichment, and free CO concentrations among these habitats show a wide range of natural, spatial variation. We determined free CO concentrations in the water column and sediment porewater in littoral zones with pH < 6.

Positive feedback favors invasion by a submersed freshwater plant.

The submersed macrophyte Utricularia inflata has invaded lakes in northern New York State, thereby threatening native isoetids such as Eriocaulon aquaticum. Isoetids often dominate and modify softwater lakes due to their capacity to oxidize sediment and thus influence solute mobilization. Greenhouse experiments tested the hypotheses that U.

An invasive macrophyte alters sediment chemistry due to suppression of a native isoetid.

The submersed macrophyte Utricularia inflata (inflated bladderwort) is a recent invader of Adirondack Mountain lakes (NY, USA). A 15-week greenhouse experiment and a 7-week field experiment were conducted to test the hypothesis that this rootless species fundamentally changes sediment chemistry through its suppression of the native short-statured species, Eriocaulon aquaticum. E.

Physical site characteristics limit pollination and fruit set in the dioecious hydrophilous species, Vallisneria americana.

Experimental and observational studies of the submersed, freshwater macrophyte Vallisneria americana Michx. revealed that depth, wind and wave exposure, and current velocity may all influence fruit set. In this dioecious species, long-pedunculate female flowers are pollinated by free-floating male flowers at the water surface.

Submersed macrophyte growth at low pH : II. CO × sediment interactions.

The submersed macrophyte Vallisneria americana was grown for seven weeks in a greenhouse to test for differences in the ability of three different sediments to support growth stimulation in response to CO enrichment at low pH. Plants accumulated 21- to 24-fold greater biomass at 10 × ambient CO concentrations than at ambient CO on all sediments. At both CO levels, plants grown on sediment from an acidified lake accumulated ca.

Submersed macrophyte growth at low pH : I. CO enrichment effects with fertile sediment.

Vallisneria americana was grown for six weeks in a greenhouse on relatively fertile sediment to test for factors other than nutrient limitation which may slow growth of this submersed macrophyte at pH 5. On the basis of dry mass accumulated, (1) low pH significantly depressed Vallisneria growth at constant free CO levels; (2) free CO enrichment, however, greatly stimulated Vallisneria growth at pH 5, by 2.8-fold and 10-fold at 3.

Comparative desiccation tolerance of two Sphagnum mosses.

Sphagnum fallax (Klinggr.) Klinggr., a moss growing in hollows close to the water table, is more desiccation tolerant than S.

Neighbor influences and seasonal growth patterns for Vallisneria americana in a mesotrophic lake.

Biomass of the submersed macrophyte Vallisneria americana rose steadily from early June to 50 g dry wt·m in ealry August. Leaves dominated the biomass of this perennial from mid-June through August, after which plants senesced to leave only winter buds as perennating organs. Only 24% of plants sampled flowered during the 1978 growing season, yielding a population mean of less than 0.

Coexistence and the comparative light relations of the submersed macrophytes Myriophyllum spicatum L. and Vallisneria americana Michx.

The Eurasian watermilfoil (Myriophyllum spicatum L.) has partially replaced wild celery (Vallisneria americana Michx.) as a community dominant in the littoral zones of lakes of Madison, Wisconsin.