The effects of sewage sludge application and the additional effects of clearfelling on nutrient cycling have been assessed in a mature Scots pine stand, north-east Scotland. The forest site was situated in a low rainfall area with high evapotranspiration and low leaching losses. The ground vegetation formed an important sink for N and P following sludge addition and clearfelling. Sludge application caused a foliar N response, increased foliar needle weight, and litterfall showed a significant and rapid potential to immobilize NH<sub>4</sub>-N and PO<sub>4</sub>-P added in sludge. The soil availability of NH<sub>4</sub>-N and PO<sub>4</sub>-P together with rates of mineralization of N and P and nitrification in sludge-treated areas were significantly increased compared with that of the control. Concentrations of NH<sub>4</sub>-N, NO<sub>3</sub>-N, PO<sub>4</sub>-P and organic P were increased significantly following sludge addition and fluxes were an order of magnitude greater than that of the control. Peaks in concentrations of NH<sub>3</sub>-N in sludge-treated areas exceeded the EC limit of 11.3 mg 1<sup>-1</sup> on several occasions. Of the total N and P applied to the sludge, throughfall and litterfall over a 17 month period, 2.4 % and 0.72 % were measured in the B<sub>s</sub> soil horizon flux. After clearfelling, initial increases in soil availability of NH<sub>4</sub>-N, NO<sub>3</sub>-N andPO<sub>4</sub>-P were measured. Felling increased nitrification rates, although increases were significant only in areas previously treated with sludge. Fluxes of NO<sub>3</sub>-N, NH<sub>4</sub>-N and PO<sub>4</sub>-P and organic P were increased at least an order of magnitude greater in felled areas than those of the control. Immobilization of N and P was greater in green and abscised litters placed in previously sludge-treated areas than compared with those placed in control areas.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:388601 |
| Date | January 1996 |
| Creators | Mitchell, Diane |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=115972 |
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