Hi,

My experience shows that Rubus quickly appears as the trees are cut down. So the canopy cover or lite amount can be important but probably not all species. In some areas I have seen Rubus sp. in dark forest also, but usually there is no other species of understory with high abundance. So Species diversity in understory should be also important factor.

Hope this helps

cheers

All Rubus species are light demanding, and - except for R. caesius and some closely related hybrids - don't grow in water-logged substrates. So, in Alder forests, draining as well as opening of the canopy will promote the growth of Rubus (subgen. Rubus, as well as idaeus). A light level of only 5% (in comparison to the open field situation) will promote Rubus growth, but as long as the ground water level is high enough, Rubus will be surpressed.

Thank you very much for both answers... Rense, any idea on how to measure (without long-term monitoring) the height of the water table, and/or subtle differences in elevation tat may translate in a higher/lower waterlogging of the soil in certain periods of the year?

Well.... I'm not sure, not knowing the exact terrain conditions. But I think I would use pipes to check the water table. Of course this could be done automatically, but that is quite expensive, I guess.... I think ground water measurement pipes are the only accurate way to measure the ground water table, but I'm no expert at all....

Field researches in the temperate and alpine areas of Eastern Himalaya reveals that most common species under genus Rubus are R. elliptcus and R. niveus. These berries are light demanding species, with good amount of soil moisture and organic carbon. These thorny shrubs are known to creep up when the trees are felled down. Usually trees in these areas are felled and vegetation is burnt to bring more area under pasture as these areas have high dependence on livestock based economy. Being delicious berries they attract humans and ruminants alike and numerous seeds in each berry ensure their dispersal to distant lands.

I strongly disagree, Martina! The species of Rubus in Europe, except for the very few sexuals, don't hybridize at all.....

Hi Giorgio,

I am not an expert for hybridizing of Rubus species but as you know, I should know site conditions of European temperate forest very well. Let's have a discussion on that. also Czech forest data may be useful...cheers

Further to Rense. Widespread purposive lowering of the groundwater table by a meter or so of farmlands with patches and hedges of alder in the Netherlands and Germany have been followed  by dominance of Rubus spp. in the understory.  

A question for Martina. I have seen alder in the Mediterranean basin in montane- temperate climates, but not yet in a (Eu-)Mediterranean climate. Does alder occur also under lowland Mediterranean climate conditions beyond maybe a few relict stands?