Document: TER-3-99-119

Variation in nitrogen mineralization across forb and graminoid zones of a New England salt marsh.

THEODOSE, T.A.* and J.L.MARTIN

University of Southern Maine, Portland, ME 04104 USA ¹

Abstract:
New England high salt marsh primary productivity is N limited, but variation in plant N availability across salt marsh vegetation zones has not been quantified. In order to investigate this, we measured net N mineralization rates in three zones of a Maine high salt marsh, Juncus gerardii, Spartina patens, and mixed perennial forb. Measurements were made of both in situ net N mineralization, conducted in the field throughout the growing season, and potential N mineralization, conducted under anaerobic conditions in the laboratory holding environmental conditions constant. We also measured microclimatic factors and substrate quality, to see if either related to differences in net N mineralization. Both in situ net N mineralization rates and potential net N mineralization rates were significantly higher in the forb zone than in graminoid zones. However, substrate quality differences among zones were unclear. Although both total nitrogen and carbon were higher in the forb zone than in graminoid zones, C:N ratios did not vary significantly across zones. In contrast, large differences in microclimatic factors occurred among zones, with soil temperatures and moistures highest in the forb zone relative to graminoid zones. Thus microclimatic factors may be more important than substrate quality in determining the high rates of net N mineralization in the forb zone relative to the graminoid zones of this high salt marsh.

Keywords: Juncus gerardii,Spartina patens

This abstract is being presented at: 10:30 AM in session:
SALT MARSHES