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The influence of abiotic conditions on Avena sterilis plant litter decomposition was studied at three sites along a topoclimatic gradient in the Judean Desert, Israel. Decomposition of A. sterilis plant litter followed a two-phase pattern: early and rapid mass loss during the winter season followed by a long period of low mass loss during the remaining seasons. Differences in decomposition rates were found between winter and summer, and between material on the soil surface and buried in the soil. There were significant differences in decomposition rates attributable to topoclimatic location, to which the short rainy-winter season contributed significantly. Lignin concentration was found to increase significantly during the rapid phase of decomposition, however a decrease in this value occurred during the remaining dry seasons. Litter nitrogen content oscillated during the study period such that in the buried litter a bi-phasic pattern similar to the litter decomposition in the above-ground litter was obtained. These results suggest that litter decomposition is not affected by climate but by litter lignin content, since an inverse relationship was found between lignin content and the decomposition rate. (C) 2000 Academic Press.