Correlates of tree species sorting along a temperature gradient in New Zealand rain forests: seedling functional traits, growth and shade tolerance

Abstract

Summary 1.It is widely believed that species sorting on environmental gradients reflects trade-offs between competitive ability and physiological tolerance of stresses such as frost and desiccation. One specific expression of this general idea is the hypothesis that tree species sorting on temperature gradients in temperate regions involves a trade-off between growth rate and frost resistance, because adaptations to frost reduce light interception and carbon gain potential. 2. We measured seedling growth of 17 New Zealand rain forest angiosperm trees in a glasshouse, as well as biomass partitioning, gas exchange and hydraulic traits. We then related these variables to the mean July (winter) minimum temperatures most frequently experienced throughout the range of each species. 3. Species associated with mild winters on average had wider vessels and more conductive stems and were leafier (i.e. developed more foliage area per unit sapwood area) than species from frostier sites. Species' positions on the temperature gradient were not significantly correlated with relative growth rates of seedlings; they were, however, negatively correlated with two measures of species light requirements in the field: the light compensation point for growth, and low-light mortality rates obtained from the literature. 4. Synthesis. Although seedling growth rates of warm-and cool-temperate New Zealand angiosperm trees were similar on average, the former are more shade tolerant. Competitive hierarchies associated with tree species sorting on temperature gradients thus probably involve a shift in the relationship between shade tolerance and growth rate, rather than a simple trade-off of growth with cold tolerance. This shift is associated with variation in light interception potential per unit of seedling biomass, possibly reflecting a trade-off between stem conductivity and resistance to freeze-thaw embolism.

Temperature is better than precipitation as a predictor of plant community assembly across a dryland region

“…; Lusk et al. ) and facilitated in others (Michalet et al. ), while relatively stress‐tolerant species may competitively reduce intolerant species in other scenarios (Tilman ; Goldberg & Novoplansky ).…”

Native woody plant recruitment in lowland forests invaded by non-native ground cover weeds and mammals

“…Other factors, such as differences in shade tolerance (Standish 2002;Grubb et al 2013), may be playing a role. For example, the lesser shade tolerance of K. excelsa could be a reason for its low seedling survival in the current study, particularly at the three sites where mean canopy openness was below 10%, the suggested threshold at which a species that benefits from canopy openness might be disadvantaged compared with a shade-tolerant species (Lusk et al 2013(Lusk et al , 2015.…”

Palynology and the Ecology of the New Zealand Conifers

“…While overlapping to a large extent with conifers in their environmental tolerances (Figure 11), and thus co-existing over wide areas, Nothofagaceae are mostly absent from the warmest locations-mainly the north of the North Island and southern North Island lowlands. Like conifers, they are vulnerable to having their regeneration supressed by fastgrowing broadleaves under warm, moist climates but lack the slow-growing emergent strategy that permits conifers to persist in dense broadleaved forests (Lusk et al, 2013). They are also largely absent from the drier, more drought-prone, frostier regions where several tall conifer trees (most notably Podocarpus laetus and Prumnopitys taxifolia) are abundant.…”