Soil carbon content along a rainfall gradient and inhibition of germination: a potential mechanism for regulating distribution of Plantago coronopus

The distribution of plant species in desert landscapes may be affected by i nhibition of seed germination by factors in the soil. We tested the inhibit ion of Plantago coronopus seed germination on cyanobacterial soil crusts un der laboratory conditions. Samples were collected from 10 locations along a rainfall gradient in the Negev Desert, Israel and soil crust and soil samp les were collected from porcupine diggings in one location. We hypothesized that germination inhibition varies along this gradient as well as at a par ticular location mainly due to soil carbon content. We tested the hypothesi s that soil carbon content has the same inhibition effect at both local and regional scales. There were strong negative relationships between germinat ion and soil carbon content suggesting that this variable is at least a str ong predictor of germination success for P. coronopus in Negev landscapes. Germination inhibition and its control by soil carbon content, may be an im portant influence on the distribution and dominance of plant species in thi s region. (C) 1999 Elsevier Science Ltd. All rights reserved.