Tropical rain forest expansion and savanna woody vegetation thickening appear to be a global trend, but there remains uncertainty about whether there is a common set of global drivers. Using geographic information techniques, we analyzed aerial photography of five areas in the humid tropics of northeastern Queensland, Australia, taken in the 1950s and 2008, to determine if changes in rain forest extent match those reported for the Australian monsoon tropics using similar techniques. Mapping of the 1950s aerial photography showed that of the combined study area (64,430 ha), 63% was classified as eucalypt forests/woodland and 37% as rain forest. Our mapping revealed that although most boundaries remained stable, there was a net increase of 732 ha of the original rain forest area over the study period, and negligible conversion of rain forest to eucalypt forest/woodland. Statistical modeling, controlling for spatial autocorrelation, indicated distance from preexisting rain forest as the strongest determinant of rain forest expansion. Margin extension had a mean rate across the five sites of 0.6 m per decade. Expansion was greater in tall open forest types but also occurred in shorter, more flammable woodland vegetation types. No correlations were detected with other local variables (aspect, elevation, geology, topography, drainage). Using a geographically weighted mean rate of rain forest margin extension across the whole region, we predict that over 25% of tall open forest (a forest type of high conservation significance) would still remain after 2000 years of rain forest expansion. This slow replacement is due to the convoluted nature of the rain forest boundary and the irregular shape of the tall open forest patches. Our analyses point to the increased concentration of atmospheric CO2 as the most likely global driver of indiscriminate rain forest expansion occurring in northeastern Australia, by increasing tree growth and thereby overriding the effects of fire disturbance.

Although rain forest is characterized as pyrophobic, pyrophilic giant eucalypts grow as rain forest emergents in both temperate and tropical Australia. In temperate Australia, such eucalypts depend on extensive, infrequent fires to produce conditions suitable for seedling growth. Little is known, however, about constraints on seedlings of tropical giant eucalypts. We tested whether seedlings of Eucalyptus grandis experience edaphic constraints similar to their temperate counterparts. We hypothesized that phosphorous addition would alleviate edaphic constraints. We grew seedlings in a factorial experiment combining fumigation (to simulate nutrient release and soil pasteurization by fire), soil type (E. grandis forest versus rain forest soil) and phosphorus addition as factors. We found that phosphorus was the principal factor limiting E. grandis seedling survival and growth in rain forest soil, and that fumigation enhanced survival of seedlings in both E. grandis forest and rain forest soil. We conclude that similar to edaphic constraints on temperate giant eucalypts, mineral nutrient and biotic attributes of a tropical rain forest soil may hamper E. grandis seedling establishment. In rain forest soil, E. grandis seedlings benefited from conditions akin to a fire-generated ashbed (i.e., an “ashbed effect”).

Idiospermum australiense (Diels) S. T. Blake, is a rare species that produces very large diaspores (up to 225 g) comprising 2–6 cotyledons. Anecdotal evidence suggested that each cotyledon within the diaspore could develop an independent root/shoot axis in natural populations and under glasshouse conditions. To investigate this potential, 13 diaspores were collected. Six diaspores were kept intact and cotyledons in the remaining seven were separated, planted into soil and scored for germination. All shoots were allowed to grow for 12 weeks. To test for differences in growth response from seedlings emerging from intact diaspores and single cotyledons, plant height, shoot mass, stem mass, leaf mass and total leaf area were compared between groups using both absolute values and values standardized to initial reserve mass. To examine the effects of reserve mass in more detail, height to stem mass, leaf mass to stem mass and specific leaf area was also compared between groups. All intact cotyledons and 24 of the 27 single cotyledons produced a functional root/shoot system. Time to germination was not different between groups. Shoot mass, stem mass and leaf mass were significantly greater in intact diaspores than in single cotyledons, although no difference was found in any parameter when standardized to initial reserve mass. Shoots arising from individual cotyledons were significantly taller per gram initial weight, because of a significantly greater relationship between height and stem mass. Shoots arising from single cotyledons also had a significantly greater investment in leaf mass per unit stem mass, even though there was no difference in specific leaf area between groups. Thus, seedlings arising from individual cotyledons grew relatively taller and produced a greater area of leaf tissue relative to stem than those arising from intact diaspores.

MATERIALS AND METHODS The effects of 24 herbicides on soybean [G/vcine max (L.)Merr.] seed yield, weight, protein, nonprotein nitrogen, oil, and fatty acid composition were investigated for several cultivars in 1969, 1970, and 1971 at Urbana, Illinois. Significant, but very small alterations in the measured parameters were noted for some herbicides, applied alone or in combination. The greatest difference observed was a reduction in seed yield due to injury from excessive herbicide rates or competition from weeds not controlled. The practical importance of the apparent alterations in seed composition caused by the herbicides is considered inconsequential. Additional Index Words: pesticides, fatty acid composition of soybeans, herbicides, protein composition of soybeans, oil composition of soybeans.