Accurate ground-based estimation of the carbon stored in terrestrial ecosystems is critical to quantifying the global carbon budget. Allometric models provide cost-effective methods for biomass prediction. But do such models vary with ecoregion or plant functional type? We compiled 15 054 measurements of individual tree or shrub biomass from across Australia to examine the generality of allometric models for above-ground biomass prediction. This provided a robust case study because Australia includes ecoregions ranging from arid shrublands to tropical rainforests, and has a rich history of biomass research, particularly in planted forests. Regardless of ecoregion, for five broad categories of plant functional type (shrubs; multistemmed trees; trees of the genus Eucalyptus and closely related genera; other trees of high wood density; and other trees of low wood density), relationships between biomass and stem diameter were generic. Simple power-law models explained 84-95% of the variation in biomass, with little improvement in model performance when other plant variables (height, bole wood density), or site characteristics (climate, age, management) were included. Predictions of stand-based biomass from allometric models of varying levels of generalization (species-specific, plant functional type) were validated using whole-plot harvest data from 17 contrasting stands (range: 9-356 Mg ha(-1) ). Losses in efficiency of prediction were <1% if generalized models were used in place of species-specific models. Furthermore, application of generalized multispecies models did not introduce significant bias in biomass prediction in 92% of the 53 species tested. Further, overall efficiency of stand-level biomass prediction was 99%, with a mean absolute prediction error of only 13%. Hence, for cost-effective prediction of biomass across a wide range of stands, we recommend use of generic allometric models based on plant functional types. Development of new species-specific models is only warranted when gains in accuracy of stand-based predictions are relatively high (e.g. high-value monocultures).

SUMMARYGrowth and phosphorus acquisition of pot-grown seedlings of karri (Eticalyptus diversicolor F. Muell.) were examined following inoculation with four ectomycorrhizal fungi -Descolea maculata Bougher (two isolates), Pisolithus tinctorius (Pers.) Coker & Couch, and Laccaria laccata (Scop, ex Fr.) Berk. & Br. Seedlings were raised in steam-sterilized sand to which 13 rates of phosphorus (0-100 mg P kg"' soil) were applied.All fungi except P. tinctorius produced a plant growth response. L. laccata produced the largest growth response. Responses were greatest at low rates of application of P to soil. There was no effect of the fungi on growth at levels of P application above 28 mg P kg'' soil. A threshold efFect (no increase in growth with increasing additions of P) characteristic of non-mycorrhizal seedlings was eliminated by mycorrhizal infection.Mycorrhizal inoculation increased P content of plant tissues at sub-optimal levels of P supply. The effect of mycorrhizas on seedling P status diminished with increasing soil P. One isolate of D. maculata often had greater rates of P accumulation and produced higher concentrations of P in plant tissues than L. laccata, but did not produce greater plant biomass.Frequency of infection for all fungi was low in soils with no additional P, and greatest with the addition of 2 mg P kg-' soil (L. laccata and D. maculata isolate A), or 4 mg P kg"' soil (D. mactdata isolate B). Infection was reduced with increasing soil P, and not evident at 36 mg P kg"' soil or higher levels of soil P. L. laccata had higher infection frequency and mycorrhizal root length at all levels of soil P than the D. maculata isolates.Two fungi produced basidiomes. This occurred at levels of soil P application ranging from 4 to 20 mg P kg"' soil for D. macidata (isolate B), and at 4 to 28 mg P kg"' soil for L. laccata.

SUMMARYExperiments were carried out to investigate the possibility that vesicular arbuscular (VA) mycorrhizal infection of grass {Lolium perenne L.) and clover {Trifolium repens L.) roots can enhance the exchange of nitrogen between the root systems of nitrogen-Hxing pasture legumes and associated grasses.The results showed higher rates of transfer of '''N applied as ('-'•NH,),,SO,, to the clover plants to companion grass plants when the roots were mycorrhizal. In some cases but not all the grass grew better in the mycorrhizal treatments.An experiment in which the clover and grass roots were separated by a 60/

No abstract

Abstnd-Ureilites containing homogeneous F076 olivine cores in intimate co-existence with graphite must have recrystallized at pressures of at least -100 bars to suppress smelting of the fayalite component of the olivine to Fe metal. Smelting of olivine and pyroxene-saturated magmatic liquids produces orthopyrollene-without-olivine crystalline derivatives unlike those in ureilites. Thus the Mg# compositional variation within the ureilite suite, which is commonly attnbuted to partial smelting. cannot plausibly be produced by assemblages rich in liquid. In situsmelting of graphitic olivine + pigeonite crystal mushes can produce the correct crystal assemblage, but fails to~de a plaUSIble account for the removal of metal from ureilites or for the correlation of Mg# with .1 17 0 . Even if Mg# and .1 17 0 variations are established in the nebula, ureilite recrystallization with graphite must have occurred at pressures greater than the minima we have experimentally established, corresponding to parent objects not less than -100 km in radius.