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Leaf area index ( LAI), a measure of canopy density, is a key variable for modelling and understanding primary productivity, and also water use and energy exchange in forest ecosystems. However, LAI varies considerably with phenology and disturbance patterns, so alternative approaches to quantifying stand-level processes should be considered. The carbon isotope composition of soil organic matter (δ13 CSOM) provides a time-integrated, productivity-weighted measure of physiological and stand-level processes, reflecting biomass deposition from seasonal to decadal time scales., Our primary aim was to explore how well LAI correlates with δ13 CSOM across biomes., Using a global data set spanning large environmental gradients in tropical, temperate and boreal forest and woodland, we assess the strength of the correlation between LAI and δ13 CSOM; we also assess climatic variables derived from the World Clim database., We found that LAI was strongly correlated with δ13 CSOM, but was also correlated with Mean Temperature of the Wettest Quarter, Mean Precipitation of Warmest Quarter and Annual Solar Radiation across and within biomes., Synthesis. Our results demonstrate that δ13 CSOM values can provide spatially explicit estimates of leaf area index ( LAI) and could therefore serve as a surrogate for productivity and water use. While δ13 CSOM has traditionally been used to reconstruct the relative abundance of C3 versus C4 species, the results of this study demonstrate that within stable C3- or C4-dominated biomes, δ13 CSOM can provide additional insights. The fact that LAI is strongly correlated to δ13 CSOM may allow for a more nuanced interpretation of ecosystem properties of palaeoecosystems based on palaeosol 13 C values. [ABSTRACT FROM AUTHOR]

1. Plant height is a central part of plant ecological strategy. It is strongly correlated with life span, seed mass and time to maturity, and is a major determinant of a species’ ability to compete for light. Plant height is also related to critical ecosystem variables such as animal diversity and carbon storage capacity. However, remarkably little is known about global patterns in plant height. Here, we use maximum height data for 7084 plant Species × Site combinations to provide the first global, cross-species quantification of the latitudinal gradient in plant height. 2. The mean maximum height of species growing within 15° of the equator (7.8 m) was 29 times greater than the height of species between 60° and 75° N (27 cm), and 31 times greater than the height of species between 45° and 60° S (25 cm). There was no evidence that the latitudinal gradient in plant height was different in the northern hemisphere than in the southern hemisphere ( P = 0.29). A 2.4-fold drop in plant height at the edge of the tropics ( P = 0.006) supports the idea that there might be a switch in plant strategy between temperate and tropical zones. 3. We investigated 22 environmental variables to determine which factors underlie the latitudinal gradient in plant height. We found that species with a wide range of height strategies were present in cold, dry, low productivity systems, but there was a noticeable lack of very short species in wetter, warmer, more productive sites. Variables that capture information about growing conditions during the harsh times of the year were relatively poor predictors of height. The best model for global patterns in plant height included only one term: precipitation in the wettest month ( R2 = 0.256). 4. Synthesis. We found a remarkably steep relationship between latitude and height, indicating a major difference in plant strategy between high and low latitude systems. We also provide new, surprising information about the correlations between plant height and environmental variables. [ABSTRACT FROM AUTHOR]

1. Our aim was to develop a quantitative proxy for environmental adversity (abiotic stress) in temperate Eucalyptus and Nothofagus forest and woodland ecosystems. 2. Samples and measurements were collected at 42 sites across a rainfall gradient in southern Australia, an elevation gradient in south-eastern Australia, and a longitudinal transect (temperature gradient) in Patagonia, Argentina. 3. We compared the ability of (a) abiotic variables (14 soil and 21 climatic variables) and (b) the stable carbon isotope (δ13C) values of soil organic matter (SOM), to predict variation in leaf area index (LAI; a forest productivity variable). 4. The δ13C of SOM (soil aggregates) explained more variation (57%) in LAI than multivariate statistical models that integrated information on many abiotic variables. W* (a climatic water balance model) was also a powerful predictor variable, explaining 37% of the variability in LAI. 5 Synthesis. The stable carbon isotopic signature of soil aggregates is a powerful explanatory variable that may help us to quantify environmental adversity (abiotic stress) in temperate forest and woodland ecosystems. [ABSTRACT FROM AUTHOR]