Mineralisation of carbon and plant uptake of phosphorus from microbially-derived organic matter in response to 19 years simulated nitrogen deposition
Here we test the hypotheses that 19 years of simulated pollutant N deposition increases both losses of carbon (C) and the ability of plants to access P from organic material in upland heathland. The grass, Dactylis glomerata, and the dwarf shrub, Calluna vulgaris, were grown in soil containing microbial-derived organic matter labelled with 14C and 33P. We found that both soil and root-surface phosphatase activity increased significantly in response to N deposition. We also found a significant positive relationship between root-surface phosphatase activity and 33P uptake for Calluna, but a negative relationship for Dactylis. Efflux of 14C from the microbial-derived organic matter was strongly dependent on an interaction among plant presence, plant species and N deposition. Our results show that mineralisation of C and P, and subsequent plant uptake of P from organic sources is decoupled. In our experimental conditions, stimulation of P turnover coupled with subsequent plant uptake through up-regulation of root phosphatases is little affected by N addition. However, our data indicate that root-surface phosphatases are likely to be more important for uptake of P derived from organic sources for Calluna than for Dactylis.
KeywordsPhosphatase Nitrogen deposition Heathland Carbon mineralisation Organic phosphorus 33P 14C
This work was supported by the Natural Environment Research Council. We thank Dr. S. J. M. Caporn for allowing us to sample from his experimental site, Dr C. J. Trinder for supplying Dactylis plants, J. Brodie for technical support, and two anonymous referees for their comments.
- Aerts R, Berendse F (1988) The effect of increased nutrient availability on vegetation dynamics in wet heathlands. Vegetatio 76:63–69Google Scholar
- Berendse F, Elberse WT (1989) Competition and nutrient losses from the plant. In: Lambers H, Cambridge ML, Konings H, Pons TL (eds) Causes and consequences of variation in growth rate and productivity of higher plants. SPB Academic, The Hague, pp 269–284Google Scholar
- Frank AB (1894) Die Bedeutung der Mykorrhiza-pilze für die gemeine Kiefer. Forstwissschaftliches Zentralblatt 16:1852–1890Google Scholar
- Gimingham CH (1972) Ecology of heathlands. Chapman and Hall, LondonGoogle Scholar
- Harrison AF (1987) Soil organic phosphorus: a review of world literature. CABI, Wallingford, UKGoogle Scholar