New Zealand climate in the Neogene and implications for global atmospheric circulation

New Zealand has a good Neogene plant fossil record. During the Miocene it was without high topography and it was highly maritime, meaning that its climate, and the resulting vegetation, would be controlled dominantly by zonal climate conditions. Its vegetation record during this time suggests the climate passed from an ever-wet and cool but frostless phase in the Early Miocene in which Nothofagus subgenus Brassospora was prominent. Then it became seasonally dry, with vegetation in which palms and Eucalyptus were prominent and fires were frequent, and in the mid-Miocene, it developed a dry-climate vegetation dominated by Casuarinaceae. These changes are reflected in a sedimentological change from acidic to alkaline chemistry and the appearance of regular charcoal in the record. The vegetation then changed again to include a prominent herb component including Chenopodiaceae and Asteraceae. Sphagnum became prominent, and Nothofagus returned, but mainly as the subgenus Fuscospora (presently restricted to temperate climates). This is interpreted as a return to a generally wet, but now cold climate, in which outbreaks of cold polar air and frost were frequent. The transient drying out of a small maritime island and the accompanying vegetation/climate sequence could be explained by a higher frequency of the Sub-Tropical High Pressure (STHP) cells (the descending limbs of the Hadley cells) over New Zealand during the Miocene. This may have resulted from an increased frequency of 'blocking', a synoptic situation which occurs in the region today. An alternative hypothesis, that the global STHP belt lay at a significantly higher latitude in the early Neogene (perhaps 55degreesS) than today (about 30degreesS), is considered less likely because of physical constraints on STHP belt latitude. In either case, the difference between the early Neogene and present situation may have been a response to an increased polar-equatorial temperature gradient. This contrasts with current climate models for the geological past in which the latitude of the High Pressure belt impact is held invariant though geological time. (C) 2003 Elsevier Science B.V. All rights reserved.

The characteristics of six species of living hollow-bearing trees and their importance for arboreal marsupials in the dry sclerophyll forests of southeast Queensland, Australia

Six species of trees located in the dry sclerophyll forests of southeast Queensland were studied to ascertain which was most suitable to be retained as hollow-bearing trees for nesting and denning by arboreal marsupials. Generally for all tree species, the number of entrances to hollows was positively correlated with the diameter at breast height (DBH) and the growth stage, and entrance diameters also increased in trees with a larger DBH. However, there were differences between the species; Corymbia citriodora had few hollows until the individuals were very large while Eucalyptus crebra had low numbers of hollows throughout its entire size range. It was concluded that a mixture of tree species provided a range of hollow sizes and positions that would be suitable for nesting and denning by arboreal marsupials in those forests. There were large differences between tree species in the relationship between tree size and estimated age. Five of the tree species took between 186 and 230 years to begin to produce hollows while E. crebra took up to 324 years. This suggests that tree species other than E. crebra may be the most preferred for retention in areas where hollow-bearing tree densities are lower than the prescribed level. Other data also suggests there are likely to be enough trees in larger size classes that would begin to form hollows within the next 50 years to compensate for an expected loss of hollow-bearing stags during that same period. In terms of forest operation, the retention of six hollow-bearing trees/ha would represent an estimated loss of 7.3-15% wood production. (C) 2003 Elsevier Science B.V. All rights reserved.

Yield responses to ethephon for unshaken and mechanically shaken macadamia

Ethephon promotes fruit abscission and accelerates harvest of macadamia, Macadamia integrifolia (Proteaceae), but has limited use due to concerns that associated abscission of inner-canopy leaves may reduce subsequent yield and nut quality. Yield and quality were monitored for 2 years following ethephon application to both unshaken and mechanically shaken trees of the late-abscising cultivar, A16. Nut quality was not adversely affected in subsequent seasons, but effects on yield varied. In 3 of 6 experiments, ethephon reduced yield in the year after application. However, in 4 of the 6 experiments, 2 years of ethephon application greatly elevated yield in the third year. This was not a compensating recovery from low second-year yield, as third-year yield of trees that received only 1 ethephon treatment did not differ from yield of control trees. Ethephon-assisted harvest remains feasible for macadamia, although further work is warranted given the potential risks and considerable benefits for subsequent yield. Inner canopy defoliation, resulting from ethephon use, could represent a canopy management technique for dense-canopy fruit trees.

Crystallisation and moisture sorption properties of selected Australian unifloral honeys

The sorption properties of yapunyah (Eucalyptus ochropholia) and yellow box (Eucalyptus melliodora) honeys (Australian unifloral honeys) were investigated in a controlled relative humidity (RH) environment at 30degreesC for 71 days. The original water activity of the honeys affected the sorption properties. These two honeys absorbed moisture at and above 67.9% RH and desorbed moisture at and below 51.4% RH. The crystallisation behaviour of tea tree (Melaleuca quinquenervia) and yapunyah honeys was studied during storage at 13 and 23 degreesC. The degree of crystallisation was monitored by measuring the absorbance at 660 and 665 nm using a spectrophotometer. The heat-treated honeys did not show any sign of crystallisation after S months, whereas a seeding with precrystallised honey induced crystallisation of the same honeys. This crystallisation was more rapid at 13 than at 23degreesC. (C) 2003 Society of Chemical Industry.