1.A plant's growth rate is seen as a central element of its ecological strategy, and as determined by its traits.Yet the literature is inconsistent about the empirical correlation between functional traits and growth, casting doubt on the capacity of some prominent traits to influence growth rate. 2.We propose that traits should influence growth in a way that depends on the size of individual plants. We outline mechanisms and hypotheses based on new theoretical work and test these predictions in tree species using a meta-analysis of 103 studies (> 500 correlations) for five traits (specific leaf area, wood density, maximum height, seed mass and maximum assimilation rate). We also recorded data for 14 other traits commonly used in the trait literature. To capture the effects of plant size, we tested for a shift in the direction of correlation between growth rates and each trait across three ontogenetic stages: seedling, sapling and adult.3. Results were consistent with predictions, although there were some limitations arising from unequal numbers of observation across ontogenetic stages. Specific leaf area was correlated with relative growth rate in seedlings but not in adult plants. Correlations of growth with wood density were not affected by ontogenetic stage. Seed mass, assimilation rate and maximum height were correlated with relative growth rate only in one ontogenetic stage category: seedlings, seedlings and adults, respectively. 4.Although we were able to confirm several of our theoretical predictions, major knowledge gaps still exist in the trait literature. For example, for one-third of the traits considered, the majority (> 75%) of reported correlations with growth came from the same ontogenetic stage. 5.Synthesis. We show for some traits, how trait-growth correlations change in a predictable way with plant size. Our understanding of plant strategies should shift away from describing species as having a fixed growth strategy throughout their life (on a continuous axis from slow to fast growth), in favour of a size-dependent growth trajectories.

Aim  At a regional scale, across southern Africa, woody thickening of savannas is becoming increasingly widespread. Using coupled vegetation and faunal responses (ants), we explore whether major changes in woody cover in savannas represent an increase in the density of savanna trees (C4 grass layer remains intact) or a ‘regime shift’ in system state from savanna to thicket (=dry forest) where broad‐leaved, forest‐associated trees shade out C4 grasses. Location  Hluhluwe Game Reserve, South Africa. Methods  We sampled paired open (low woody cover) and closed (high cover that have undergone an increase in tree density) sites. Vegetation was sampled using belt transects, and a combination of pitfall trapping and Winkler sampling was used for ants. Results  Closed habitats did not simply contain a higher density of woody savanna species, but differed significantly in structure, functional composition (high prevalence of broad‐leaved trees, discontinuous C4 grasses) and system properties (e.g. low flammability). Ant assemblage composition reflected this difference in habitat. The trophic structure of ant assemblages in the two habitats revealed a functional shift with much higher abundances of predatory species in the closed habitat. Main conclusions  The predominance of species with forest‐associated traits and concomitant reduction of C4 grasses in closed sites indicate that vegetation has undergone a shift in fundamental system state (to thicket), rather than simply savanna thickening. This biome shift has cascading functional consequences and implications for biodiversity conservation. The potential loss of many specialist savanna plant species is especially concerning, given the spatial extent and speed of this vegetation switch. Although it is not clear how easily the habitat switch can be reversed and how stable the thicket habitats are, it is likely in the not‐too‐distant future that conservation managers will be forced to make decisions on whether to actively maintain savannas.

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Woody plant encroachment into savannas is a globally prevalent phenomenon and impacts ecosystem goods and services such as biodiversity, carbon storage, nutrient cycling, grazing and hydrology. The direct ecological and economic consequences for rangelands have been fairly well studied, but, to our knowledge, the economic impact on conservation efforts has not been investigated. African savannas are important as conservation areas because they support large numbers of the world’s remaining megafauna. This study used visitor surveys and long-term mammal distribution data to investigate how an increase in tree density might affect the visibility of animals in a conservation area, which could reduce the satisfaction of visitors to the area. We found that apparent herd sizes and density of animals were much reduced in woody areas, suggesting that visibility is negatively impacted. Visitor surveys determined that a large fraction (almost half) of potential future visitors to the park may be lost if animals became more difficult to see and that the majority of these would be the higher-spending visitors. Responses differed depending on the origin of visitors, with international visitors being more interested in seeing animals, whilst local visitors were more content with just being away from the city. The results suggest that woody plant encroachment may have significant impacts on visitor numbers to savanna conservation areas, whilst animal numbers and densities may also be significantly impacted. Conservation implications: The results pointed to potentially significant economic consequences for conservation efforts as visitors become less satisfied with their experience. Perceptions of visitors are important for management decisions as park fees contribute significantly to conservation efforts. This could ultimately result in a reduced capacity for African conservation areas to conserve their biodiversity effectively. The results suggest that management may need to re-evaluate their approach to controlling woody plant encroachment