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PREMISE OF THE STUDY: In fire-prone ecosystems, variation in bark thickness among species and communities has been explained by fire frequency; thick bark is necessary to protect cambium from lethal temperatures. Elsewhere this investment is deemed unnecessary, and thin bark is thought to prevail. Flowever, in rain forest ecosystems where fire is rare, bark thickness varies widely among species and communities, and the causes of this variation remain enigmatic. We tested for functional explanations of bark thickness variation in temperate rain forest species and communities. METHODS: We measured bark thickness in 82 tree species throughout New Zealand temperate rain forests that historically have experienced little fire and applied two complementary analyses. First, we examined correlations between bark traits and leaf habit, and leaf and stem traits. Second, we calculated community-weighted mean (CWM) bark thickness for 272 plots distributed throughout New Zealand to identify the environments in which thicker-barked communities occur. KEY RESULTS: Conifers had higher size-independent bark thickness than evergreen angiosperms. Species w ith thicker bark or higher bark allocation coefficients were not associated with "slow economic" plant traits. Across 272 forest plots, communities with thicker bark occurred on infertile soils, and communities with thicker bark and higher bark allocation coefficients occurred in cooler, drier climates. CONCLUSIONS: In non-fire-prone temperate rain forest ecosystems, investment in bark is driven by soil resources, cool minimum temperatures, and seasonal moisture stress. The role of these factors in fire-prone ecosystems warrants testing. [ABSTRACT FROM AUTHOR]

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Highlights: [•] We examined the recovery of Afrotemperate forest from colonial logging. [•] Historically logged forests do not converge on the composition of primary forest. [•] Primary forests were dominated by two conifer species (Podocarpaceae). [•] Long-lived pioneer angiosperms dominated the canopies of secondary forest. [•] Above-ground carbon was 2 to 3-fold higher in primary forest. [Copyright &y& Elsevier]

Abstract: Indigenous forests are declining throughout southern Africa, partly because of exogenous disturbances such as harvesting of forest resources. We evaluate the influence of colonial logging and present-day harvesting of pole-size trees (2–15cmdbh), used for construction and fuelwood, on the structure and composition of iGxalingenwa forest in KwaZulu-Natal, South Africa. This forest has a distinctive physiognomy, with a thicket-like understorey and an emergent layer of primarily coniferous Podocarpus spp. These emergent trees represent individuals that were too small to be harvested during the colonial period. We argue that the dense angiosperm-dominated understorey arose in gaps created by logging, which allowed greater light levels at the forest floor. The understorey has since been intensively harvested (36% of available stems) for pole-sized stems, including canopy species, effectively suppressing the advanced regeneration as well as the replacement of the senescing canopy and emergent tree populations. The harvesting intensity of pole-sized stems is related to the species, size, and availability of trees. Few straight pole-sized stems are available among the understorey species and typically straight-stemmed canopy species are opportunistically harvested. Examination of community composition further suggests that, without management intervention, this forest will have a reduced stature, a thicket-like physiognomy, and be less diverse and less dominated by conifers. To rescue iGxalingenwa forest from this successional path requires a reduction in harvesting pressure on seedlings and saplings of species that normally dominate the canopy layer, many of which (Podocarpus falcatus, Ptaeroxylon obliquum and Calodendrum capense) appear to have declining populations. The effects of commercial logging a century ago still persist and are being compounded by subsistence harvesting with significant changes to forest physiognomy and composition and the possibility of arrested succession. [Copyright &y& Elsevier]

Regeneration of forest canopy trees can be inhibited by understory thickets. We hypothesized that Isoglossa woodii, a large-leaved herbaceous plant, limits tree recruitment in subtropical coastal dune forests by providing habitat to fruit and seedling consumers. Using uncaged and caged treatments in I. woodii gaps and thickets, we found that frugivore and herbivore behavior is not influenced by I. woodii. We conclude that direct effects of I. woodii on postemergence processes in seedlings contribute to tree recruitment limitation. [ABSTRACT FROM AUTHOR]