ABSENCE OF TREE SEEDS IMPEDES SHRUBLAND SUCCESSION IN SOUTHERN CHINA

Abstract

Wang J, Zou C, Ren H & Duan Wj. 2009. Absence of tree seeds impedes shrubland succession in southern
China. Change in landuse in southern China has resulted in the abandonment of over 40 million ha of
degraded grazing pasture and cultivated farmland, which have consequently converted to shrubland.
Shrubland has low economic value and provides limited ecosystem services but is now the dominant
vegetation in three provinces of southern China. Effective management of such shrubland ecosystem requires
improved understanding of many ecological factors, including sources of viable seeds in the soil seed bank
and the interaction between the seed bank and the current vegetation. We investigated the soil seed bank
in a shrubland using a seedling germination assay, and compared the species composition in the seed bank
with vegetation community using Sorensen’s coefficient. While total seed bank density in the shrubland was
high, the Sorensen’s coefficient and species richness in the soil seed bank were low. The soil seed bank was
mainly dominated by grass and shrub species; no pine or other indigenous tree seeds were detected. Our
findings suggest that the limited seed source of tree species is one of the primary factors slowing or stopping
secondary succession in southern China. Direct planting of tree seedlings may facilitate secondary succession
in the severely degraded shrublands.