In our last blog we discussed a forest fire that had recently burned in the DAEMONS catchment. Last week Filip and Sara went hunting for the burned area but, after 3.5 hrs roaming the woods of Svartedalen nature reserve in the rain, gave up without any success. Subsequent inquiries with the fire brigade shed light on the problem: all media reports had placed the fire in the wrong place! The fire didn’t burn near Måkevatten, but occurred approximately 1.5 km away on the northern shores of Stora Holmevatten. Armed with this new information, Filip and Sara ventured out again and successfully found the fire area.
On the ground the fire burned an area of 300 m x 100 m, running right down to the lake shore. Small trees and shrubs have gone, but the larger pines look set to survive. A cursory investigation suggests that the fire didn’t penetrate too deeply into the soil; Filip and Sara reported that under a few centimeters of burned material was a normal looking FH horizon. They collected several samples from the lake and headwater streams which will be analysed for water chemistry to determine the local impact of the fire. The revised location of the fire means that the only DAEMONS sample sites that could possibly be affected will be the outflows of the Rördalsån and the Anråse. However, considering the small size of the fire, and the large size of the catchment, it seems extremely unlikely that any signal will be detected in the water chemistry. On 4th June a forest fire was reported in Svartedalen nature reserve. The fire was brought under control, but at its peak was several hundred metres wide. This nature reserve is approximately 2km south of the Gårdsjön catchment where several DAEMONS sampling sites are located. It seems likely that these sampling sites will be unaffected, but we plan to visit the area for a closer look during the July sampling round.
The Svartedalen nature reserve lies across a watershed; some of its streams drain east into the Göta älv, but some also drain west into the Rördalsån, one of the three main subcatchments that DAEMONS is studying. The affected area appears to be near the lake of Måkevatten, which drains into the Rördalsån. It is therefore feasible that two DAEMONS sampling sites will be affected: the outflows of the Rördalsån and the Anråse, with possible fire-induced changes in the concentrations of C, N and P. Likely responses into the aquatic system will be a large spike in nitrate concentration, and a lesser spike in phosphorus concentration, coupled with increased sediment release and a possible pulse of sulphate and acidity. Considering the legacy of acid deposition in the area this could have negative effects on lake and stream ecosystems, including fish populations. These aquatic biogeochemical effects will likely began when the first significant precipitation occurs. Members of the DAEMONS team have an interest in wildfire and so we will be keeping a keen eye on the project data and the Svartedalen nature reserve over the next few months. |
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