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Foliar nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) concentrations of 5 Symphyomyrtus ( E. botryoides, E. cladocalyx, E. microcorys, E. nitens, E. saligna) and 7 Monocalyptus ( E. agglomerata, E. baxteri, E. globoidea, E. muelleriana, E. obliqua, E. pilularis, E. regnans) species were determined for each of four hill country microsites; upper shady, lower shady, upper sunny and lower sunny slopes. ANOVA and correlation analysis were used to identify species and microsite effects, and nutrient associations. Significant ( P ≤ 0.0014) species differences were identified for all nutrients, E. botryoides and E. saligna generally had high nutrient concentrations while stringybark species were low, particularly for N and K. Subgeneric contrasts revealed that Symphyomyrtus species had significantly higher concentrations of P ( P = 0.05) N, K and Ca ( P < 0.0001) but lower Mg ( P < 0.0001) than Monocalyptus. Microsite had less influence on nutrient concentrations than species. N was strongly positively correlated with P and K in most Symphyomyrtus species but was not correlated with P in Monocalyptus. Mg was positively correlated with Ca but negatively correlated with K in most species. The results indicate that Monocalyptus and Symphyomyrtus species differ in ability to accumulate key macronutrients. [ABSTRACT FROM AUTHOR]

The seasonal growth (height and diameter) of 12 Eucalyptus species ( E. agglomerata, E. baxteri, E. botryoides, E. cladocalyx, E. globoidea, E. microcorys, E. muelleriana, E. nitens, E. obliqua, E. pilularis, E. regnans, E. saligna) was measured on trees between 2 and 4 years of age on four hill country microsites; upper shady, lower shady, upper sunny and lower sunny slopes. Additionally, seasonal mean daily solar radiation and temperature were recorded on each aspect over the same time period. Height and diameter growth were both strongly seasonal; mean diameter growth was highest in the spring (0.91 cm) while height growth was greatest in the summer (0.57 m). Conversely, diameter and height growth were least in the winter (0.38 cm and 0.09 m respectively). There was a significant interaction between season and aspect for height ( P = 0.01) and diameter ( P = 0.02). Diameter and height growth on the shady face was similar to that on the sunny slopes during summer, but, in winter growth on the shady face was typically lower than the sunny. Slope position also influenced height growth ( P = 0.001), particularly in the winter, growth on the lower slope being less than on the upper. There was a strong linear relationship between seasonal height growth and solar radiation but a curvilinear relationship between seasonal diameter growth and radiation. Consideration of the influence of topography on solar radiation and other environmental factors may allow more reliable assessment of potential forest production on a micro scale. [ABSTRACT FROM AUTHOR]

1 Angiosperm trees often dominate forests growing in resource-rich habitats, whereas conifers are generally restricted to less productive habitats. It has been suggested that conifers may be displaced by angiosperms except where competition is less intense, because conifer seedlings are inherently slow growing, and are outpaced by faster-growing angiosperm species. Here we investigate whether competition with ferns and deeply shading trees also contributes to a failure of conifers to regenerate in resource-rich habitats. 2 We examined how changes in soil nutrient availability and drainage affected vegetation along the retrogressive stages of a soil chronosequence in southern New Zealand. Vegetation composition shifted from angiosperm-tree dominance on ‘recent’ alluvial terraces (< 24 ky), via coniferous-tree dominance on older marine terraces (79–121 ky), to coniferous-shrub dominance on the oldest marine terraces (291 ky). Soil drainage deteriorated along the sequence, and N : Pleaves and N : Psoil indicate increasing P-limitation. Conifer species appear to be adapted to persistence on infertile and poorly drained soils. 3 The floor of the relatively fertile alluvial forests was deeply shaded (∼1% light transmission) by dense groves of tree-ferns and ground-ferns, and by large-leaved subcanopy trees. Few seedlings of any type were found on the forest floor, even in tree-fall gaps, and establishment was restricted to rotting logs and tree-fern trunks. Angiosperms were particularly successful at colonizing these raised surfaces. 4 Less shade was cast by the conifer-dominated forests on infertile marine terraces (∼5% light transmission), which lacked tall ferns. There were many opportunities for conifer establishment, with high seedling densities recorded on the forest floor and on logs. By contrast, angiosperm seedlings were mainly restricted to logs. 5 Our results suggest that several mechanisms act in concert to reduce regeneration opportunities for conifers in productive habitats. In particular, we suggest that tall ferns and deep shade are responsible for a restriction of regeneration opportunities in relatively productive forests in New Zealand, diminishing the opportunities for conifers to escape the competitive effects of fast-growing angiosperms. Thus ‘crocodiles’ may alter the outcome of the race between ‘hares’ and ‘tortoises’. [ABSTRACT FROM AUTHOR]

The effect of microsite on juvenile forest plantation yield is rarely explored. This is because juvenile plantation growth is considered to be reasonably homogenous due to a lack of resource competition between trees prior to canopy closure. However, models of juvenile plantation height growth and survival that are sensitive to microsite variation could aid decisions relating to site preparation, plantation establishment and early silvicultural treatments. In this study, juvenile Eucalyptus bosistoana and E. globoidea height growth and survival proportion were modelled against topographic and environmental microsite characteristics as independent variables. The experiment included three different sites situated in a sub-humid region of New Zealand. A total of 540 plots were planted with 18,540 trees in regular rows and columns. Micro-topographical variables significantly influenced height growth and survival proportion of both E. bosistoana and E. globoidea, but species differed in their responses. More sheltered microsites yielded greater height growth and survival for both species. The height of both species was influenced by wind exposure, morphometric protection, and distance from the nearest ridge. E. bosistoana height was also influenced by topographic position and surface plan curvature. Survival was affected by surface profile curvature for both species, while E. globoidea survival was also impacted by surface plan curvature and distance from the top ridge. This study identified microsite factors influencing juvenile height and survival of two Eucalyptus species. [ABSTRACT FROM AUTHOR]