Causes of increased nutrient concentrations in post-fire regrowth in an East African savanna |
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Authors: | Van de Vijver C A D M Poot P Prins H H T |
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Institution: | (1) Dept. of Environmental Sciences; Tropical Nature Conservation and Vertebrate Ecology Group, Wageningen Agricultural University, Bornsesteeg 69, 6708 PD Wageningen, The Netherlands;(2) Plant Sciences, Faculty of Agriculture, The University of Western Australia, Nedlands, WA, 6907, Australia |
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Abstract: | The aim of the present study was to investigate the causes of increased macronutrient concentrations in above-ground post-fire
regrowth in an East African savanna (Northern Tanzania). Experiments were set up to discriminate between the following possible
causes: (1) increased soil nutrient supply after fire, (2) relocation of nutrients from the roots to the new shoots, (3) rejuvenation
and related changes in plant tissue composition and (4) changes in nutrient uptake in relation to above-ground carbon gains.
N, P, K, Ca and Mg concentrations in post-burn graminoid vegetation were compared with clipped and with unburned, control
vegetation during the post-burn growth season. One month after burning and clipping, nutrient concentrations in live grass
shoots in the burned and clipped treatments were significantly higher than in the control. This effect, however, declined
in the course of the season and, except for Ca, disappeared three months after onset of the treatments. There were no significant
differences in live grass shoot nutrient concentrations between burned and clipped treatments which suggests that the increased
nutrient concentration in post-fire regrowth is not due to increased soil nutrient supply via ash deposition. The relatively
low input of nutrients through ash deposition, compared to the amount of nutrients released through mineralisation during
the first month after burning and to the total nutrient pools, supports this suggestion. There was no difference between burned
and unburned vegetation in total root biomass and root nutrient concentrations. Relocation of nutrients from the roots to
the new shoots did not, therefore, appear to be a cause of higher post-fire shoot nutrient concentrations. The present study
shows that in this relatively nutrient-rich savanna, the increased nutrient concentration in above-ground post-fire regrowth
is primarily due to increased leaf:stem ratios, rejuvenation of plant material and the distribution of a similar amount of
nutrients over less above-ground biomass.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | East Africa fire plant nutrient concentration savanna soil |
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