Does soil pyrogenic carbon determine plant functional traits in Amazon Basin forests?

Amazon forests are fire-sensitive ecosystems and consequently fires affect forest structure and composition. For instance, the legacy of past fire regimes may persist through some species and traits that are found due to past fires. In this study, we tested for relationships between functional traits that are classically presented as the main components of plant ecological strategies and environmental filters related to climate and historical fires among permanent mature forest plots across the range of local and regional environmental gradients that occur in Amazonia. We used percentage surface soil pyrogenic carbon (PyC), a recalcitrant form of carbon that can persist for millennia in soils, as a novel indicator of historical fire in old-growth forests. Five out of the nine functional traits evaluated across all 378 species were correlated with some environmental variables. Although there is more PyC in Amazonian soils than previously reported, the percentage soil PyC indicated no detectable legacy effect of past fires on contemporary functional composition. More species with dry diaspores were found in drier and hotter environments. We also found higher wood density in trees from higher temperature sites. If Amazon forest past burnings were local and without distinguishable attributes of a widespread fire regime, then impacts on biodiversity would have been small and heterogeneous. Alternatively, sufficient time may have passed since the last fire to allow for species replacement. Regardless, as we failed to detect any impact of past fire on present forest functional composition, if our plots are representative then it suggests that mature Amazon forests lack a compositional legacy of past fire

Proton acceleration using 50 fs, high intensity ASTRA-Gemini laser pulses

We report on experimental investigations of proton acceleration from thin foil targets irradiated with ultra-short (similar to 50 fs), high contrast (similar to 10(10)) and ultra-intense (up to 10(21) W/cm(2)) laser pulses. These measurements provided for the first time the opportunity to extend the scaling laws for the acceleration process in the ultra-short regime beyond the 10(20) W/cm(2) threshold. The scaling of accelerated proton energies was investigated by varying the thickness of Al targets (down to 50 nm) under 35 angle of laser incidence and with p-polarised light

Fast ion acceleration from thin foils irradiated by ultra-high intensity, ultra-high contrast laser pulses

Ion acceleration resulting from the interaction of ultra-high intensity (2 x 10(20) W/cm(2)) and ultra-high contrast (similar to 10(10)) laser pulses with 0.05-10 mu m thick Al foils at normal (0 degrees) and 35 degrees laser incidence is investigated. When decreasing the target thickness from 10 mu m down to 0.05 mu m, the accelerated ions become less divergent and the ion flux increases, particularly at normal (0 degrees) laser incidence on the target. A laser energy conversion into protons of,similar to 6.5% is estimated at 35 degrees laser incidence. Experimental results are in reasonable agreement with theoretical estimates and can be a benchmark for further theoretical and computational work