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Increased phosphorus retention in Tasmanian headwater streams modified by clearfell, burn and sow forestry - ASL Congress

50th ASL Congress & 43rd NZFSS Congress 2011

27-29 September 2011

Brisbane, Australia

Oral presentation

Ryan Burrows1,2,4
J Fellman3
R Magierowski1
L Barmuta1,2

1 School of Zoology, University of Tasmania
2 CRC for Forestry, Private Bag 12, Hobart, Tasmania 7001
3 School of Plant Biology, UWA
4 Presenting author

Abstract

In southern Tasmania clearfell, burn and sow (CBS) silvicultural operations can potentially alter the environment of headwater streams. Our objective was to investigate whether the large, short-term environmental differences (e.g., sediment chemistry, woody debris) between CBS-affected and old-growth stream reaches lead to measurable differences in their nutrient uptake metrics. To do this, we measured stream environmental variables and used nutrient addition experiments to measure the uptake length, uptake velocity and uptake rate of phosphorus (PO43--P) and nitrogen (NH4+-N) in three old-growth and four CBS-affected headwater stream reaches. The abundacne and volume of fine woody debris, light availability, sediment nutrients, and sediment organic matter were all greater within CBS-affected reaches. Uptake length for both CBS-affected and old growth stream reaches ranged from 85 – 312 m for NH4+-N and 88 – 1429 m for PO43--P. However, nutrient retention was greater (i.e. shorter uptake lengths and higher uptake velocities and rates) in CBS-affected reaches than in the old-growth reaches, particularly for PO43--P. Overall, our findings suggest that the same disturbance that may increase catchment nutrient flux may also facilitate the development of environmental conditions that increase the capacity for streams to retain nutrients, at least in the short-term (< 10 years after logging).


Biobuzz issue fifteen, December 2011