Vascular diversity patterns of forest ecosystem before and after a 43-year interval under changing climate conditions in the Changbaishan Nature Reserve, northeastern China

摘要

The Changbaishan Nature Reserve (CNR) is the largest protected temperate forest in the world. It was established in 1960 to protect the virgin Korean pine (Pinus koraiensis) mixed hardwood forest, a typical temperate forest of northeast China. Studies of vascular diversity patterns on the north slope of the CNR mountainside forest (800-1700 m a.s.l.) were conducted in 1963 and in 2006. The aim of this comparison was to assess the long-term effects of the protected status on plant biodiversity during the intervening 43 years. The research was carried out in three forest types: mixed coniferous and broad-leaved forest (MCBF), mixed coniferous forest (MCF), and sub-alpine coniferous forest (SCF), characterized by different dominant species. The alpha diversity indicted by species richness and the Shannon-Wiener index were found to differ for the same elevations and forest types after the 43-year interval, while the beta diversity indicated by the Cody index depicted the altitudinal patterns of plant species gain and loss. The floral compositional pattern and the diversity of vascular species were generally similar along altitudinal gradients before and after the 43-year interval, but some substantial changes were evident with the altitude gradient. In the tree layer, the dominant species in 2006 were similar to those of 1963, though diversity declined with altitude. The indices in the three forest types did not differ significantly between 1963 and 2006, and these values even increased in the MCBF and MCF. However, originally dominant species, such as Pinus koraiensis, tended to decline, the proportion of broad-leaved trees increased, and the species turnover in the succession layers showed a trend to shift to higher altitudes. The diversity pattern of the understory fluctuated along the altitudinal gradient due to micro-environmental variations. A comparison of the alpha diversity indices among the three forest types reveals that the diversity of the shrub and herb layer decreased, and some rare and medicinal species disappeared. Meteorological records show that climate has changed significantly in this 43-year intervening period, and information collected from another field survey found that the most severe human disturbances to the CNR forests stemmed from the exploitation of Ginseng roots and Korean pine nuts.