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Many studies have reported that hydraulic properties vary considerably between tree species, but little is known about their intraspecific variation and, therefore, their capacity to adapt to a warmer and drier climate. Here, we quantify phenotypic divergence and clinal variation for embolism resistance, hydraulic conductivity and branch growth, in four tree species, two angiosperms (Betula pendula, Populus tremula) and two conifers (Picea abies, Pinus sylvestris), across their latitudinal distribution in Europe. Growth and hydraulic efficiency varied widely within species and between populations. The variability of embolism resistance was in general weaker than that of growth and hydraulic efficiency, and very low for all species but Populus tremula. In addition, no and weak support for a safety vs. efficiency trade-off was observed for the angiosperm and conifer species, respectively. The limited variability of embolism resistance observed here for all species except Populus tremula, suggests that forest populations will unlikely be able to adapt hydraulically to drier conditions through the evolution of embolism resistance. [ABSTRACT FROM AUTHOR]

Iron-related P forms directly influence the amount of phosphate released from soils and sediments, particularly when subjected to reduction. In this work, we examined such P forms in 12 overfertilized, widely different European soils by using various single and sequential extraction techniques, including the use of a mild and a strong reductant (ascorbate and dithionite, respectively). Reductant-soluble P (defined as the amount of P released by the specific action of a strong reductant) ranged from 2 to 63% of the total amount of P extracted by the sequential extraction procedure of Olsen and Sommers. More than 50% of reductant-soluble P was released by the specific effect of ascorbate in most of the soils studied. The results of the sequential extractions suggest that, on average, about one-half of the reductant-soluble P was occluded in Fe oxides. Poorly crystalline and crystallineFe oxides generally contained similar amounts of occluded P in absolute terms. However, Me mole ratios were higher in poorly crystalline than in crystalline Fe oxides (X = 5.9 and 1.7 x 10-2, respectively). We suggest that fertilizer P may have been occluded in Feoxides, particularly in the poorly crystalline forms. The contribution of the parent material, pedogenesis, and fertilization to occludedP build-up is difficult to assess. Though obtained in vitro, our results suggest that reduction of overfertifized soil materials in aquatic environments can release significant amounts of P; these in turn increase saturation of reduction-resistant P-adsorbing surfaces and thus help increase the P equilibrium concentration in solution. [ABSTRACT FROM AUTHOR]