Abstract:

As forests are destroyed, remaining habitats may have too little area to sustain viable populations as extinction follows forest loss or fragmentation. Thuja sutchuenensisis, a typical Wild Plant with Extremely Small Populations (WPESP), once been declared extinct in the wild, were rediscovered in 1999. However, recent deforestation is a major threat to T. sutchuenensisis survival. Few studies have explored community responses by T. sutchuenensisis to long-term logging. Here, we quantified the population size, population viability, and community composition of the remaining T. sutchuenensisis forests following illegal and severe logging, based on three surveyed datasets on the permanent plots in 2004, 2010 and 2016, respectively. The results show that remaining T. sutchuenensisis seedlings and saplings had increased by 85.71% after 13 years of illegal logging. The population survival rate of T. sutchuenensisis decreased by 25.43%, in contrast, the death density and extinction risk rate increased by 24.12% and 28.62%, respectively. Meanwhile the species richness and the Shannon-Wiener index of the community showed an increase with 96.43% and 33.35% after 13 years of logging. The results demonstrate that the population viability and the dominance of T. sutchuenensisis in the remaining community show strong decline, and the coniferous and broad-leaved mixed forest dominated by T. sutchuenensisis is likely to be replaced by broad-leaved forest. Our results also have important implications for small population conservation, given that the remaining forest may play a unique role in the persistence of T. sutchuenensisis.

Key words: deforestation, Thuja sutchuenensis, Wild Plant with Extremely Small Populations (WPESP), population viability, community structure dynamics