Impact of winter reed harvesting and burning on the nutrient economy of reed beds

Published source details Ostendorp W. (1995) Impact of winter reed harvesting and burning on the nutrient economy of reed beds. Wetlands Ecology and Management, 3, 233-248.
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Summary

This study was conducted to determine if winter reed Phragmites australis harvesting and burning is an effective strategy to reduce the nutrient input within reedbeds; it has been hypothesized that repeated treatment would cause the reed vegetation to become nutrient limited, and reduce reed vitality. Accordingly this might enhance growing conditions for endangered wetland plants. Over four years, reed harvesting and burning experiments were undertaken at Lake Constance-Untersee with the objective of reducing organic matter and nutrient content of the top layers of the sediment. Whether oxygen conditions in within-reedbed waterbodies improved was also investigated.

Study area: The experiment was undertaken in reedbeds around the western part of Lake Constance-Untersee (a shallow eutrophic lake), southwest Germany.

Mowing and burning: Mowing and burning experiments were conducted during winter months when the water level was low and the ground frozen, between 1979 and 1984. The mowing was done by various caterpillar-tracked machines with an interchangeable mowing and chaffing device, with resultant chaffed reed and litter removed by hand or machine. Where burnt, ash was left on the ground.

Monitoring: Six treated reed beds and three control beds over a period of up to 4 years were monitored by sampling along cross-shore transects extending from the reed front to the mixed Phragmites-Carex-Phalaris zone along the landward edge.

The sediment top layer (0 to 2.5 cm depth) below the Phragmites litter was sampled in winter and analyzed for organic matter, total nitrogen, and total phosphorus. The dry matter content of a sediment core of 4 cm diameter and 2.5 cm thickness was used to calculate bulk density (kg dry matter per m² in the 1 cm sediment surface layer). Water samples were taken from within reedbed waterbodies and analysed.

Over the 4 years of the experiment, the surface sediment/water system of the reed beds was found to be well buffered against the removal of the current year's dead Phragmites straw/litter, as only slight, and mostly insignificant, differences between treated and untreated reedbeds were detected.

There were no obvious differences in the bottom water layer (taken at 5 cm above the lake bed) between winter harvested and untreated reed beds and it seems that very local circumstances influence the hydrochemical properties more than the treatment.

As a result of these findings, the author concludes that (over the limited time period of the experiment at least) the benefit of winter reed harvesting/burning as a means to reduce nutrient levels within reedbeds remain dubious, and harvesting had little influence on water conditions.

Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at:

http://www.springerlink.com/content/q41651r307936114/fulltext.pdf