‡Present address: Department of Plant and Soil Sciences, University of Aberdeen, Aberdeen AB24 3UU, UK.
Competition between roots and soil micro-organisms for nutrients from nitrogen-rich patches of varying complexity
Article first published online: 24 DEC 2001
Journal of Ecology
Volume 88, Issue 1, pages 150–164, February 2000
How to Cite
Hodge, A., Stewart, J., Robinson, D., Griffiths, B. S. and Fitter, A. H. (2000), Competition between roots and soil micro-organisms for nutrients from nitrogen-rich patches of varying complexity. Journal of Ecology, 88: 150–164. doi: 10.1046/j.1365-2745.2000.00434.x
- Issue published online: 24 DEC 2001
- Article first published online: 24 DEC 2001
- C : N ratios;
- Lolium perenne;
- organic patches;
- microbial activity
1 We used Lolium perenne plants grown in microcosms to investigate the responses of root demography, plant N capture, soil fauna populations and microbial community profiles to five organic patches containing the same amount of N but differing in their chemical and physical complexity and C : N ratio. All patches were dual labelled with 15N/13C. Control patches contained the background sand : soil mix only.
2 There was rapid decomposition in, and plant N capture from, the patches of lowest C : N ratio. Early in the experiment 13C was detected in the soil atmosphere and 15N in the shoots. No 13C enrichment was detected in the plant material.
3 The rate of root production was slowest in the most complex patch (L. perenne shoot material) but accelerated when patches were simpler and had lower C : N ratios. There was no difference in root mortality between treatments.
4 Nitrogen concentrations of shoots and roots and shoot biomass were greater in the N-containing patches than controls, except for the most complex patch, while root biomass did not differ with treatments.
5 Total plant N capture was 45–54% of that initially added in patches that had a C : N ratio < 4. However, in the most complex patch (C : N ratio c. 21 : 1) plants captured only 11% of the N added.
6 Biomass of microbial-feeding protozoa was related to soil NO3–-N concentration in the patch but not to numbers of microbial-feeding nematodes. Patches of greater complexity increased the metabolic diversity of the microbial community (i.e. the number of substrates used in a Biolog GN plate) and altered the pattern of substrate utilization.
7 At harvest, the amount of patch-derived N estimated to be in the microbial biomass was much smaller (i.e. 7–13%) than in the plant tissues. Thus, plants were highly effective competitors with micro-organisms when capturing N supplied in patches with a low C : N ratio.