Aboveground biomass allocation and water content relationships in Mediterranean trees and shrubs in two climatological regions in Israel

This study investigated the variation along basipetal gradients of the relationships between the foliage/wood allocation ratios of biomass and of water content, in Mediterranean trees and shrubs, at two different locations along a climatic gradient. Understanding of the biomass allocation and water relations in Mediterranean trees and shrubs provides useful information on growth patterns of these species, and on resource dynamics of these plant communities. Two experimental sites were selected along a climatological transect that runs from the foothills of the Judean Hills to the northern Negev desert in Israel. At each site, 16 quadrats of 10 x 10 m (eight on south-facing slopes and eight on north-facing slopes) were marked. The aboveground biomass of dominant tree and shrub species were estimated. Main branches of trees and shrubs were cut, their foliage and wood biomass were separately weighed, and their respective water contents were determined. The species studied included the evergreen sclerophylls, Quercus calliprinos, Phillyrea latifolia and Pistacia lentiscus, and the semi-deciduous species, Cistus creticus, Coridothymus capitatus and Sarcopoterium spinosum. The results indicated that the foliage/wood ratio decreased from the periphery of the crown to the interior of the trees and shrubs: foliage biomass and water were mainly limited to the top 30 cm of the crown in all studied species. Leaves had higher relative water contents than woody tissues in the upper part of the crown. However; when the whole tree or shrub was considered, the relative water content was found to be mostly allocated to the woody structures. The results are discussed in terms of biomass allocation in various life forms of the eastern-Mediterranean plant communities and how they are affected by slope aspect and climatic conditions.