Fjölrit RALA - 05.12.1999, Page 136

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BIOMASS AND SOIL NUTRIENT POOLS IN NEWZEALAND
whereas the mean values for dead material and for roots are similar. Differences in
technique of measurement, especiallv of the above-ground live material, between the
Canterbury and Otago studies may have affected the relative proportions of the three
biomass compartments.
Species differences are not consistent in total biomass or in compartments. Despite
smaller stature, C. macra grasslands are not consistently lower in above-ground bio-
mass than those of other tall tussocks. Although all these sites had been selected as
least-disturbed examples of tall tussock grasslands at these four locations, they show
large range in dead above-ground biomass, with variation not closely related to live
biomass, suggesting differences in rates of decay or of litter incorporation. Such
variations in decomposition rate, including some of the present Otago studies, have
been related by Molloy et al (1978ab) to various environmental factors. Differences in
lapse of time since a litter-consuming fire might have had some influence on the mass
of dead material, but the knowledge that at no site had fire occurred within, at the very
least, 15 years does not help resolve the issue, as no information is available on fire
severity.
Nitrogen, phosphorus, potassium and calcium in tall tussock biomass
Nitrogen, phosphorus, potassium and calcium have been selected as common íforn
among seven nutrients analysed in different studies, to indicate the range in quantities
in live, above-ground biomass among tall tussock grasslands of different species of
Chionochloa. Table 2 demonstrates the substantial variation in nutrient contents in
live above-ground biomass, only K showing lower coefficient of variation than that
shown in Table 1 by biomass itself.
Table 2. Weights of N, P, K, Ca (kg ha-1) in above-ground live biomass pools (shoots) in relation
to weights of total N and P and of exchangeable K and Ca in 0-200 mm soil layer (kg ha_1), for
nine tall tussock grasslands in South Island high country. Pearson correlation coefficients for the
relationship between shoot and root of each of the four elements are shown.
Location Shoot N Soil Shoot P Soil Shoot K Soil Shoot Ca Soil
Craigieburn Mountains
la. Chionochloa pallens 118 4220 12 952 205 211 35 722
1 b. C. macra 75 4581 10 1724 88 348 22 353
lc.C. rubrcC 87 4940 10 1537 137 492 12 1314
Hakatere Basin
2a. C. macra 29 3765 7 720 39 101 5 176
2b. C. rigida 61 6324 15 1821 107 162 13 486
Tekapo, Mackenzie Basin
3. C. rubra 63 4842 9 1444 100 696 19 1708
Old Man Range, Otago
4a. C. macra 128 5477 17 1256 158 301 17 305
4b. C. macratC. rigida 43 3304 7 1037 160 191 14 103
4c. C. rigida 117 3826 30 1211 177 146 26 264
CV’s 43.7 20.4 55.5 28.1 39.4 65.6 48.5 91.8
Choot, soil 0.21 0.11 -0.11 0.09
a) Values from duplicate samples only.