The segetal plant communities of Palestine

Summary

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• 1. A phytosociological analysis of Palestine's weed vegetation of non-irrigated agriculture has revealed the existence of five plant associations well defined by floristic, ecological and phytogeographical characteristics.

• 2. These associations belong to four alliances which together constitute a particular suborder of the Secalinetalia Br. Bl.

• 3. A phytogeographical analysis of the weed flora has revealed the great proportion of East-Mediterranean and Irano-Turanian species among the segetals of Palestine.

• 4. A series of obligatory weeds occuring in Mediterranean Palestine recur as components of primary associations in the neighbouring steppes and deserts, whence they obviously came to the segetal habitat.

• 5. A series of other obligatory weeds endemic to Palestine or to Palestine and Syria have as yet not been found in primary habitats.

• 6. There is some evidence for the assumption that many widespread weeds at present not found in primary habitats are to be considered components of “new-land” associations, i.e. pioneer associations colonizing bare lands formed through denudation or spill etc. These plants have no doubt existed ever since and with the artificial formation of new land by man have occupied the segetal habitats as permanent sites.

• 7. While certain segetal associations (Prosopidetum, Eragrostis — Centaurea association) continue to exist on the spot long after cultivation has ceased and so to delay the return of primary vegetation, other associations (Ononis — Carthamus association, Achilleetum, Leopoldia — Lolium association) readily disappear from abandoned fields and clear the way for local climax vegetation or seral associations preceding the climax.