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Borchard N.,University of Bonn | Borchard N.,Julich Research Center | Siemens J.,University of Bonn | Ladd B.,University of Bonn | And 5 more authors.
Soil and Tillage Research | Year: 2014

Adding biochar to tropical soils is a strategy for improving crop yield and mitigating climate change, but how various biochar types affect crop yield and the properties of temperate soils is still in dispute. Here, we evaluated how slow-pyrolysis charcoal and two biochars derived from energy production (gasification coke and flash-pyrolysis char) affected the growth of Zea mays L. and the related properties of sandy and silty soils within a 3-year mesocosm experiment. Fertilization was performed to optimize plant growth as would be done under common agricultural practice. Analyses included the monitoring of yield, plant and soil nutrients, aggregate stability, cation exchange and water holding capacity, and black carbon content. The results showed that the added biochars did not affect crop yield at an application rate of 15gbiocharkg-1 of soil. Increasing the application rate of slow-pyrolysis charcoal to 100gkg-1 resulted in decreased plant biomass in the second and third year of the experiment, likely as a result of nutrient imbalances and N-immobilization. We did not detect any degradation of the added black carbon; however, beneficial effects on plants were limited by the small and transient effect of these biochars on the physical and chemical properties of soil. Overall, our results indicate that the added carbon from biochars is stored in soil, but all treatments tested failed to improve plant yield for the studied temperate soils under the given application rates and common agricultural practice. © 2014 Elsevier B.V. Source

Edwards W.,James Cook University | Moles A.T.,Evolution and Ecology Research Center | Chong C.,James Cook University | Chong C.,Australian National University
PLoS ONE | Year: 2015

Among co-occurring species, values for functionally important plant traits span orders of magnitude, are uni-modal, and generally positively skewed. Such data are usually logtransformed "for normality" but no convincing mechanistic explanation for a log-normal expectation exists. Here we propose a hypothesis for the distribution of seed masses based on generalised extreme value distributions (GEVs), a class of probability distributions used in climatology to characterise the impact of event magnitudes and frequencies; events that impose strong directional selection on biological traits. In tests involving datasets from 34 locations across the globe, GEVs described log10 seed mass distributions as well or better than conventional normalising statistics in 79% of cases, and revealed a systematic tendency for an overabundance of small seed sizes associated with low latitudes. GEVs characterise disturbance events experienced in a location to which individual species' life histories could respond, providing a natural, biological explanation for trait expression that is lacking from all previous hypotheses attempting to describe trait distributions in multispecies assemblages. We suggest that GEVs could provide a mechanistic explanation for plant trait distributions and potentially link biology and climatology under a single paradigm. © 2015 Edwards et al. Source

Letten A.D.,Center for Ecosystem Science | Cornwell W.K.,Evolution and Ecology Research Center
Methods in Ecology and Evolution | Year: 2015

An increasingly popular practice in community ecology is to use the evolutionary distance among interacting species as a proxy for their overall functional similarity. At the core of this approach is the implicit, yet poorly recognized, assumption that trait dissimilarity increases linearly with divergence time, that is all evolutionary time is considered equal. However, given a classic Brownian model of trait evolution, we show that the expected functional displacement of any two taxa is more appropriately represented as a linear function of time's square root. In light of this mismatch between theory and methodology, we argue that current methods at the interface of ecology and evolutionary biology often greatly overweight deep time relative to recent time. An easy solution to this weighting problem is a square root transformation of the phylogenetic distance matrix. Using simulated models of trait evolution and community assembly, we show that this transformation yields considerably higher statistical power, with improvements in 92% of trials. This methodological update is likely to improve our understanding of the connection between evolutionary relatedness and contemporary ecological processes. © 2014 British Ecological Society. Source

Ladd B.,Scientific University of the South | Ladd B.,Evolution and Ecology Research Center | Peri P.L.,CONICET | Pepper D.A.,University of New South Wales | And 14 more authors.
Journal of Ecology | Year: 2014

1. 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 (δ13CSOM) provides a time-integrated, productivity-weighted measure of physiological and stand-level processes, reflecting biomass deposition from seasonal to decadal time scales. 2. Our primary aim was to explore how well LAI correlates with δ13CSOM across biomes. 3. 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 δ13CSOM; we also assess climatic variables derived from the WorldClim database. 4. We found that LAI was strongly correlated with δ13CSOM, but was also correlated with Mean Temperature of the Wettest Quarter, Mean Precipitation of Warmest Quarter and Annual Solar Radiation across and within biomes. 5. Synthesis. Our results demonstrate that δ13CSOM values can provide spatially explicit estimates of leaf area index (LAI) and could therefore serve as a surrogate for productivity and water use. While δ13CSOM 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, δ13CSOM can provide additional insights. The fact that LAI is strongly correlated to δ13CSOM may allow for a more nuanced interpretation of ecosystem properties of palaeoecosystems based on palaeosol 13C values. © 2014 The Authors. Source

Forster M.A.,Edaphic Scientific Pty Ltd | Forster M.A.,University of Queensland | Dalrymple R.L.,Evolution and Ecology Research Center | Bonser S.P.,Evolution and Ecology Research Center
Trees - Structure and Function | Year: 2016

Key message: TheAcaciaphyllode leaf form is hypothesised to be an adaptation to drought. However, in this experiment, the timing of phyllode development was not related to a low water treatment.Abstract: Acacia species have markedly different leaf forms known as compound leaves, transitional leaves, and phyllodes, also known as heteroblastic development. The different leaf types are thought to confer an advantage under varying moisture regimes, with phyllodes favoured in drier conditions. The hypothesis that phyllodes develop earlier under low water treatment was tested in this experiment. Three watering level treatments (100, 50, and 25 %) were imposed on seedlings of A. implexa to assess developmental traits (leaf emergence, initial onset of transitional leaves, and phyllodes), biomass allocation patterns (root, stem, compound leaf area/mass, transitional leaf area/mass, and phyllode area/mass), and leaf anatomy traits (epidermis, palisade and spongy mesophyll, and stomatal density). Across watering treatments, there was no difference in the developmental onset of transitional leaves or phyllodes (produced at the 6th and 9th nodes, respectively). Under low watering treatment, there was a decrease in stem height per unit stem diameter, shorter internodes, and greater allocation of biomass to roots. There was no significant difference in leaf anatomy traits. Under the low watering treatment, there was less compound leaf area and mass due to leaf shedding. In this experiment, the low watering treatment did not favour phyllode development at the expense of compound leaf development. Rather, it was found that A. implexa responds to a low water treatment similarly to many other plant species: increased allocation to roots, increased stem area per unit stem height, decrease in leaf area through senescence of older leaves, and lower relative growth rates. © 2016 Springer-Verlag Berlin Heidelberg Source

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