John E. D. Fox

Leaf litter decomposition of canopy trees, bamboo and moss in a montane moist evergreen broad-leaved forest on Ailao Mountain, Yunnan, south-west China

Litter decomposition and nutrient release of selected dominant synusiae in an old-growth, evergreen, broad-leaved mossy forest on Ailao Mountain, Yunnan, south-west China, were studied over a 22-month period. The species studied were three dominant tall tree species, Lithocarpus xylocarpus Markg., Lithocarpus chintungensis Hsu et Qian and Castanopsis wattii A. Camus; one dominant understory species (the bamboo Sinarundinaria nitida Nakai); and a mixture of dominant mosses (including Homaliodendron scalpellifolium Fleisch, Symphyodon perrottetti Mont., Herberta longifolissa Steph. and Bazzania albicans Horik.). Fast initial litter decomposition was followed by lower rates. Decomposition rates of canopy species and bamboo leaf litter appear to be controlled by the initial concentration of lignin, nitrogen (N) and phosphorus (P) more than by morphological features of the leaves. The decay rate of moss litter was less correlated with nutrient composition and lignin concentration in initial mass. The order of decomposition rates was Castanopsis wattii > L. xylocarpus > L. chintungensis > bamboo > moss. The decomposition rate constants (k) of the leaf litter for the canopy species L. xylocarpus, L. chintungensis and Castanopsis wattii were 0.62, 0.50 and 0.64, respectively, and 0.40 and 0.22 for bamboo and moss, respectively. Turnover time (1/k) for the three canopy species was 1.61 years, 2.0 years and 1.55 years, respectively, and 2.50 years and 4.55 years for bamboo and moss, respectively. The N and P concentration in the decomposing leaf litter increased in the first 6 months and then decreased over the remaining period. There was a relatively rapid initial loss of potassium (K), followed by a slight increase. Each of calcium (Ca) and magnesium (Mg) decreased with time whereas iron (Fe) and manganese (Mn) increased with time to some extent. Nutrient release from decomposing leaf litter was in the order of K > Mg > Ca > N > P > Mn > Fe, except for bamboo (Sinarundinaria nitida) K > Ca > P > N > Mg > Mn > Fe.

Nutrient fluxes in bulk precipitation, throughfall and stemflow in montane subtropical moist forest on Ailao Mountains in Yunnan, south-west China

A study of nutrient movement through rainfall, throughfall and stemflow, as well as epiphytic bryophyte (moss and liverwort) biomass and its effect on nutrient composition of stemflow, was conducted for 2 y in subtropical montane moist forest (Lithocarpus-Castanopsis association) at Xujiaba, Ailao Mountain National Nature Reserve, Yunnan, south-west China. Base cation and fluxes were increased in throughfall, while NH 4 + -N and NO 3 - -N were reduced relative to precipitation. Annual throughfall inputs of N, P, Ca and S were mainly from precipitation, while most K and two-thirds of Mg throughfall input was due to canopy leaching. Input of Na in the precipitation and throughfall was low in this forest. Net flux (throughfall flux minus bulk precipitation) and deposition ratios (ratio of throughfall flux to bulk precipitation flux) were in the low part of the range reported for other tropical montane rain forests. The throughfall data for this forest reveal generally low cycling rates for mineral elements. Abundant epiphytic bryophytes on bole bark affected the chemical composition of stemflow by selective uptake or release of elements. Relative to trees without epiphytic bryophytes, the annual amounts of total N, NH 4 +-N, Mg, Na and SO 4 2- -S were enhanced, while NO 3 - -N, K, P and Ca were depleted in stemflow. Contributions of N from nitrogen-fixing organisms are likely to be constrained by low temperatures.

Litterfall and nutrient dynamics in a montane moist evergreen broad-leaved forest in Ailao Mountains, SW China

Montane moist evergreen broad-leaved forest, dominated byLithocarpus and Castanopsis species,is the most extensive stand of subtropical mountain in Yunnan Province, SWChina. Litter production, standing crop of litter on forest floor and nutrientreturn patterns were studied over nine years (1991–1999) in a stand ofprimary evergreen broad-leaved forest in northern crest of the Ailao MountainRange. There were significant yearly variations in litter production, which ismainly related with the masting year of canopy species, and exceptionalphysicalevents (strong winds and snow) in the natural forest. The mean annual smalllitterfall is 7.12 t ha−1 yr−1ofwhich leaf litter account for 65% of the total litterfall. The seasonality ofsmall litterfall was bia-modal, with the main one in the late dry season(April–May) and a lesser one in early winter (October–November).Decomposition quotient value was relatively low with 0.58 for total smalllitterfall. Mean large-wood (≥ 2.5 cm in diameter) ranged from0.21 to 1.41 t ha−1 yr−1 with amean of 0.52 t ha−1 yr−1.Concentrations of most elements in leaf and twig were slightly greater in wetmonths than dry months, except for C and K. Woody litter had low N and Pconcentrations compared with the leaf and reproductive parts. Nutrient returntothe soil through small litterfall decrease in the orderC>N>Ca>K>Mg>Mn>Al>P>Fe, while nutrient reserve inlitteron the forest floor was in the declining sequenceC>N>Ca>K>Mg>P>Fe>Al>Mn.

Competition between Eucalyptus victrix seedlings and grass species

Competition in a natural system may be interspecific or intraspecific. In semiarid ecosystems, competition for resources between established neighboring grass species and newly recruited seedlings is very high. To examine the effects of grass species density, growing space and time of establishment on Eucalyptus victrix seedlings (interspecific competition), and the effect of density and growing space within E. victrix (intraspecific competition) we conducted an experiment under controlled conditions. We tested four hypotheses (i) E. victrix seedling growth is not affected by grass density; (ii) there is no difference in E. victrix survival and growth between early and later grass establishment; (iii) interspecific competition is not more intense than intraspecific competition in E. victrix; and (iv) growth of E. victrix seedlings is not dependent on available growing space. In a monoculture of E. victrix, seedling mortality was higher (10%) in large pots. In mixed culture pots, where E. victrix seedlings and grass seedlings were planted on the same day, E. victrix seedlings survived for up to 4 weeks, but started to die after week five in the smallest pots. However, mortalities occurred in pots of all sizes when grass was established before E. victrix seedlings. Results also indicated that the resources necessary for the growth of individual E. victrix seedlings were more limiting under conditions of increased density of neighboring grass species rather than intraspecific competition. In particular, photosynthetic area of E. victrix seedlings was drastically reduced in mixed cultures. Although density, pot size and time of planting had impacts on E. victrix seedlings, the patterns of these impacts were variable.

Separation and identification of ximenynic acid isomers in the seed oil ofSantalum spicatum R.Br. as their 4,4-dimethyloxazoline derivatives

The seed oil ofSantalum spicatum contains a significant amount of ximenynic acid,trans-11-octadecen-9-ynoic acid, a long-chain acetylenic fatty acid, as a major component (34%). The identity oftrans-ximenynic acid was confirmed after isolation by ultraviolet, infrared, and nuclear magnetic resonance (NMR) (1H- and13C-) spectroscopy and by gas chromatography/mass spectrometry (GC/MS). Thecis isomer of ximenynic acid was also found (<1%) in some samples. Thecis andtrans isomers were characterized by GC/MS comparison of their methyl esters and 4,4-dimethyloxazoline derivatives.

Comparison of oil concentration and oil quality from Santalum spicatum and S. album plantations, 8–25 years old, with those from mature S. spicatum natural stands

Summary During February to November 2004, core samples were taken from 41 trees growing in three Santalum spicatum plantations in the Wheatbelt (W–W3: age 8–11 y); one S. spicatum plantation (aged 20–25 y) from Curtin University; one Santalum album plantation (aged 15 y) also from Curtin University; and two mature natural stands of S. spicatum (aged >50 y). Each tree was cored at 150 mm and 700 mm above ground to compare heartwood percentage; oil concentration; and α-santalol, β-santalol and t, t-farnesol contents within the oil. Oils were extracted from the whole core samples (heartwood + sapwood) using ethanol, and the chemical composition was determined using a gas chromatography flame ionisation detector (GC-FID) and a mass-selective detector (GC-MS). Santalum spicatum from the three Wheatbelt plantations had significantly lower proportions of heartwood (28–48%) than those from Curtin University (61–69%) and the natural stands (64–79%), at 150 mm and 700 mm above the ground. Santalum album at age 15 y had 57–59% heartwood at both sampling heights. The mean total extractable oil concentrations from S. spicatum plantations growing at Curtin University. W1 and W2 (2.2–3.6%), were similar to those from mature natural stands (2.3–3.1%), at both 150 mm and 700 mm. The mean oil concentration from W3 (0.7–0.8%), however, was significantly less than the mean oil concentration from mature S. spicatum. The S. album plantation had a mean oil concentration of 1.3–2.3%. Within the oil, W1 and Curtin University plantations had α-santalol (5.5–27.3%) and β-santalol (2.1–10.5%) contents similar to or greater than those in the natural stands (3.1–8.0% α-santalol; 1.3–3.0% α-santalol), at both sampling heights. W2 had poor oil quality with only 0.1–2.4% α-santalol and 0–0.6% α-santalol. As expected, the S. album had significantly more α- and α-santalol within the oil than S. spicatum. Mean t, t-farnesol content within the oil from W2 and W3 (28.3–38.7%) was significantly greater than within the oil from the mature S. spicatum (10.0–16.2%), at both sampling heights. Santalum album had the lowest t, t-farnesol content of only 0.1%.

Assessment of Western Australian sandalwood seeds for seed oil production

Summary The Western Australian sandalwood (Santalum spicatum R.Br.) industry is transforming into an agro-forestry industry in which the seeds are being considered as a valuable secondary income—generating product. Oil extracted from the seeds has a potential use in the cosmetic industry. This study aimed to identify the quality parameters for seeds to obtain oil of better and consistent quality, and the effect of seed source, seed size and storage time. Different seed samples varied in oil content, moisture content and fatty acid profile. Larger seeds from plantation trees in the wheatbelt region of Western Australia are the most suitable source of seed oil thus far evaluated. The seed grading system currently used by the sandalwood industry was suitable for selecting seeds from plantations (but not from natural stands in arid regions—‘wild wood’) for seed oil production. Basic parameters for the selection of seeds for oil extraction were identified.

Vegetation – environment relationships of the Hamersley Ranges, a mountainous desert of north-west Australia

Understanding environment-vegetation relationships provides important ecological insights, and here we examined such relationships for the Hamersley Ranges of North West Australia. We were particularly interested to see if such relationships were similar to those of other mountainous deserts. We used direct gradient analyses of floristic and environmental variables (constrained ordination), supplemented by identification of environmental differences between plant communities, assessment of environment-vegetation associations and partitioning of the floristic variance between environmental, climatic and spatial variables. Most communities could be differentiated from others according to environmental variables, with slope, surface stone cover, topsoil phosphorus and pH particularly good at differentiating between plant communities. There was strong association between communities and classes of landform and/or geological substrate. Gradient analysis demonstrated the primary floristic gradient was linked to a complex of several topographic, edaphic and geomorphic variables. This was interpreted as floristic change along broad topo-sequences from mountain/ridge tops to valley floors over which gradients in key environmental variables occur. Gradient analyses of other mountainous deserts have reported similar findings. A key distinction in the complex gradient identified for the Hamersley Ranges is the inclusion of topsoil phosphorus (rather than nitrogen) and time since last fire. The second most important floristic gradient was linked to soil pH and conductivity, which reflects floristic variation due to differences in geological substrate throughout the study area.