Above- and belowground ecosystem biomass, carbon and nitrogen allocation in recently afforested grassland and adjacent intensively managed grassland
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- Peichl, M., Leava, N.A. & Kiely, G. Plant Soil (2012) 350: 281. doi:10.1007/s11104-011-0905-9
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Background and Aims
This study investigated initial land-use change effects on ecosystem biomass, carbon (C) and nitrogen (N) allocation and storage by comparing a recently afforested grassland with an adjacent intensively managed grassland in southern Ireland.
Soil C, N and fine root (<2 mm) stocks were determined from soil cores. Above ground biomass, C and N stocks were estimated from biomass clipping, inventory and allometric biomass equations developed for ash (Fraxinus excelsior L.) and black alder (Alnus glutinosa L.) in the 5-year-old forest plantation.
Five years after grassland afforestation, the mean fine root stock of 0.31 kg m−2 in the forest was about half that of 0.64 kg m−2 in the grassland. This decrease was offset by an additional gain of 0.36 kg m−2 in tree biomass since afforestation. The above- to below ground biomass ratio shifted from 0.20 in the grassland to 1.59 in the forest. From May to October, mean net N mineralization was significantly lower in the forest compared to the grassland. Soil C and N concentrations in the 0–10 cm soil layer were significantly higher in the forest (62 mg C g−1; 5.7 mg N g−1) compared to the grassland (45 mg C g−1; 3.6 mg N g−1). However, the bulk density in the upper forest soil layer was lower than in the grassland. As a result, no differences existed between the respective total (0–30 cm depth) soil C and N stocks. Total ecosystem C and N storage was also similar for the forest (9.5 kg C m−2; 0.75 kg N m−2) and the grassland (9.3 kg C m−2; 0.77 kg N m−2).
A significant change in total ecosystem C and N following afforestation of this intensively managed grassland was not observed. Nevertheless, this study highlights immediate implications from such land-use change activities on biomass, C and N reallocation among the above- and belowground ecosystem pools which may subsequently affect ecosystem biogeochemical cycles.