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International audience; Hydraulic redistribution (HR), the passive reallocation of water along plant structures following a water potential gradient, is an important mechanism for plant survival under drought. For example, trees with deeper roots reallocate water from deeper moist to shallower, drier soil layers sustaining their upper fine root system. The relevance of HR for temperate forest ecosystems is hardly investigated. Both environmental and tree internal factors limiting the capacity for HR, such as low water potential gradients or root anatomy, respectively, are not well understood. Here we investigate fine root anatomy and related capacity for reverse flow of water of six temperate tree species, i.e. Acer pseudoplatanus, Castanea sativa, Fagus sylvatica, Picea abies, Pseudotsuga menziesii and Quercus robur both in forward and reverse flow direction. Additionally, anatomy of primary and secondary roots was analyzed, to test the hypotheses that root anatomy is similar in primary and secondary roots (H1) and conductivity for forward and reverse flow of water in fine roots is identical (H2). In contrast to the two conifer species, most anatomical parameters, e.g. hydraulic conduit diameter and conduit density, were distinctly different between primary and secondary roots in the angiosperms. Therefore, H1 was not supported for angiosperm trees. The reverse flow of water in fine roots was reduced by approx. 40 % compared to the forward flow in angiosperms, while there was no difference in the conifers. Thus, H2 was confirmed for conifers while there was a significant difference for angiosperms. This reduction may be caused by vessel structure (e.g. tapering or secondary thickening elements), or perforation plate and pit architecture (e.g. width of aperture opening). Because of the reduced conductivity of reverse water flow, the ability of angiosperm trees to redistribute water along their root system might be lower than expected.

The current database is part of the FEM growth and yield database, a collection of growth and yield data from even-aged monocultures (douglas fir, common oak, poplar, Japanese Larch, Norway spruce, Scots pine, Corsican pine, Austrian pine, red oak and several other species, with only a few plots, even-aged mixed species forest plots, uneven-aged natural forest, uneven-aged selection forest and roadside plantattions of poplar. The FEM growth and yield data base is currently supervised by Jan den Ouden and Frits Mohren.

Pitomi kesten (Castanea sativa) vrsta je šumskog drveća koja je u posljednjih 50 godina iskusila velike i snažne napade biotičkih čimbenika na području europskoga kontinenta. Ponajprije se to odnosi na rak kore pitomoga kestena (Cryphonectria parasitica) koji je nanio velike štete sastojinama pitomoga kestena i umanjio gospodarsku važnost te vrste. Novi štetnik koji prijeti sastojinama pitomoga kestena jest kestenova osa šiškarica (Dryocosmus kuriphilus), koja se prvi put u Europi pojavila 2002. godine, a u Hrvatskoj je prvi put zabilježena 2010. godine. Međusobnu povezanost ova dva biotička čimbenika, ujedno i novu opasnost za proširenje raka kore pitomoga kestena zbog napada kestenove ose šiškarice istraživali su Prospero i Forster 2011. godine u Švicarskoj. Njihovim istraživanjem otkriveno je da su moguće novo mjesto ulaska spora raka kestenove kore napuštene šiške kestenove ose šiškarice, koje gljiva može saprofitski naseliti, što može dovesti do proširenja infekcije na susjedne grane i do stvaranja rakastih tvorevina. S obzirom na te nove spoznaje potrebno je provesti istraživanja da bi se utvrdilo postoji li opasnost za taj tip širenja zaraze i u sastojinama pitomoga kestena u Hrvatskoj., Sweet chestnut (Castanea sativa) is a species of forest trees which has in the last 50 years experienced considerable and strong attacks from biotic factors in Europe. Primarily this applies to chestnut blight (Cryphonectria parasitica). Chestnut blight has caused great harm to stands of sweet chestnut and diminished the economic importance of this species. A new pest which threatens stands of sweet chestnut is the oriental chestnut gall wasp (Dryocosmus kuriphilus), which appeared in Europe for the first time in 2002., and in Croatia was first recorded in 2010. Interconnection between these two biotic factors and new possibility for growing intensity of chestnut blight caused by the attack of oriental chestnut gall wasp was investigated by Prospero and Forster in Switzerland, 2011. Their research revealed that the possible new entry points of chestnut blight spores are abandoned galls of oriental chestnut gall wasp, which the fungus can saprophyticly populate and can lead to expansion on adjacent branches and formation of cankers. In view of this new information research is necessary in order to determine whether there ise a danger of spreading of this type of infection in stands of sweet chestnut in Croatia.