PARENT SESSION
Oral Session #29: Spatial Ecology and Disturbance Ecology.
Presiding: J. Ludwig
Tuesday, August 6. 8:00 AM to 11:30 AM. Coconino Meeting Room, TCC.
The significance of spatial and temporal patterns of algal mat deposition in structuring salt-marsh vegetation.
Van Hulzen, J. (Han)*,1, Bouma, Tjeerd1, 1 Netherlands Institute of Ecology, Yerseke, Netherlands
ABSTRACT- The importance of disturbance as a mechanism for less competitive species to survive next to a better competitor has been well established. Accordingly, we expect the spatial and temporal distribution of such disturbance to be an important factor in determining vegetation pattern at a landscape level. Salt marshes offer an ideal model-system to study disturbance dynamics because of its low overall number of species and its clear zonation pattern along an elevation gradient with a patchy vegetation structure found superimposed on that zonation. This patchy vegetation structure does often not correspond with the potential performance of species. At marshes in the southwest Netherlands macroalgal mat deposition is a common source of disturbance. In this study we addressed the following questions: (i) are there hotspots of mat deposition in space as well as in time, (ii) how does timing of mat deposition affect vegetation growth and die-back through a carry-over effect with respect to carbon reseves, (iii) are hot spots and timing of mat deposition relatively important in creating habitat for less competitive species? During two succesive growing seasons monthly measurements across a 1.5-kilometer wide marsh revealed places of high and low deposition rates. Especially at the vegetation border at the low marsh deposition was high over both growing seasons. Fine scale monitoring (m2) at ten locations at the low marsh showed significant negative effects of mat cover on growth and spread of the dominant perennial Spartina anglica and increased establishment of less competitive annuals. A strong relation between plant performance and severity of mat cover was found. Mat cover at the end of the growing season made plants more vulnarable to mat cover during the following season due to lower carbohydrate recources, resulting in an increase in Salicornia patches relative to Spartina anglica
KEY WORDS: vegetation patterns, macroalgal mat deposition, spatial and temporal disturbance dynamics, salt marsh