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Modern pollen precipitation from an elevational transect in central Jordan and its relationship to vegetation
Author(s) -
Davies Caroline P.,
Fall Patricia L.
Publication year - 2001
Publication title -
journal of biogeography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 158
eISSN - 1365-2699
pISSN - 0305-0270
DOI - 10.1046/j.1365-2699.2001.00630.x
Subject(s) - steppe , shrub , vegetation (pathology) , pollen , deserts and xeric shrublands , woodland , ecology , artemisia , geography , biology , habitat , medicine , pathology
Aim To explore the relationship between modern pollen precipitation and vegetation patterns in an arid region of the Middle East. Location Data come from the central Jordan Rift from 1700 m elevation in the highlands to 300 m below sea level in the Dead Sea basin. Methods Modern pollen samples and descriptive vegetation data were collected from twenty‐one locations at 100 m elevational intervals from the highest elevations on the eastern side of the rift valley, where woodlands grow, to the lowest elevation desert on earth, characterized by drought and salt tolerant plants. Pollen percentage data from each vegetation zone are compared descriptively and numerically using cluster and Principal Components Analyses (PCA). Results Three major vegetation zones: woodland, shrub steppe, and desert scrub, are identified by their dominant plant species. The widely spaced tree, Quercus calliprinos Webb, defines the Quercus L. woodland that grows above 1500 m elevation. The shrub steppe can be divided into two subzones found between about 1500 and 900 m elevation: Artemisia herba‐alba Asso shrub steppe and Artemisia L. shrub steppe with Juniperus phoenica L. Desert scrub dominates the lower elevation landscape with Hammada salicornia (Moq.) Iljin the dominant shrub between 900 and 200 m and Haloxylon persicum Bge. found below 200 m elevation. Pollen spectra reflect the elevational vegetation zones. In particular, Quercus L. , Juniperus L. and Tamarix L. pollen are abundant where the trees grow. Highly variable amounts of non‐arboreal pollen taxa – primarily Artemisia L. and Chenopodiaceae Vent. – differentiate shrub steppe from desert scrub vegetation. Cluster and PCA of pollen data support the qualitative vegetation zonation. Main conclusions The main vegetation zones along the Jordan Rift from 1700 to –300 m elevation can be distinguished by their modern pollen precipitation. Open vegetation types, in particular, can be recognized by their pollen spectra. High amounts of Artemisia L. pollen distinguish the moister upper elevations where Artemisia L. steppe grows. In contrast, greater amounts of Chenopodiaceae Vent. pollen characterize the drier, lower elevation deserts.