International audienceThe main objective of this paper is to provide researchers that investigate fossil phytolith assemblages and model/data comparisons a new tool for estimating C(3)/C(4) grass composition over time. We tested the reliability of modem soil phytolith assemblages and phytolith indices for tracing the dominance of different grass subfamilies and tree cover density. We analyzed modem soil phytolith assemblages from sites over elevation gradients on Mount Kenya (Kenya), Mount Rungwe and around Lake Masoko (southern Tanzania). These data were compared with available botanical data. A phytolith index named Ic, proved to be an effective proxy of the proportions of Pooideae, Arundinoideae and Bambusoideae grasses (mainly C(3) grasses) versus Panicoideae grasses (mainly C(4) grasses), increasing with elevation in East-Africa. When tropical mountains are covered by open habitats (e.g. grasses and shrublands), Ic should be a reliable proxy of the C(3)/C(4) grass composition. These results highlight the value of the phytolith index Ic, when interpreting paleo-environmental records from tropical mountains, to: 1) better understand past local and regional C(3)/C(4) grass distributions and associated climatic changes and 2) increase the Set Of C(3)/C(4) data available for model/data comparisons. (c) 2007 Elsevier B.V. All rights reserved

3-OH FAs containing 10 to 18 C and a hydroxyl group in third position are characteristic components of Gram-negative bacteria. These compounds were previously used to detect and quantify Gram-negative bacterial communities in various types of samples, from terrestrial, aquatic and atmospheric environments. The relative abundance of 3-OH FAs in soils was recently shown to vary with mean annual air temperature (MAAT) and pH in soils from Mt. Shennongjia (China). In the current study, the concentrations and abundances of 3-OH FAs were determined in soils from altitudinal transects under tropical and temperate climates-Mt. Rungwe (SW Tanzania) and Mt. Majella (Central Italy), respectively. The aim was to (i) examine and compare the distributions of 3-OH FAs in soils from different climatic zones and to (ii) investigate the potential of 3-OH FAs as temperature and pH proxies. When combined with previously published data, a moderate correlation (R 2 0.62) between the summed iso and anteiso to the total amount of normal 3-OH FAs (RIAN index) and pH is obtained. We show

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