Forest characteristics, population structure and growth trends of threatened relict Pseudotsuga forrestii in China.

Pseudotsuga forrestii is a relict evergreen coniferous tree species in Pinaceae endemic to China. P. forrestii tree numbers have greatly decreased due to deforestation, over-utilization and habitat degradation. Here we clarify P. forrestii community types, structure, species diversity, seedling recruitments and growth trends. We identified four P. forrestii community types: (1) Pseudotsuga forrestii - Quercus guyavifolia - Acer davidii evergreen coniferous and broad-leaved mixed forest; (2) Pseudotsuga forrestii - Pinus yunnanensis - Quercus guyavifolia evergreen coniferous and broad-leaved mixed forest; (3) Pseudotsuga forrestii evergreen coniferous forest; (4) Pseudotsuga forrestii - Abies georgei var. smithii evergreen coniferous forest. P. forrestii forests are characterized by both warm temperate and temperate affinities. Simpson diversity, Pielou evenness, Shannon-Wiener diversity indices ranged from 0.75 to 0.76, 0.74-0.81, and 1.62-1.93, respectively, with no significant differences among the four forest types. The forest stratification was multilayered. The canopy layer was generally 10-25 m tall, with the emergent layer reached 25-42 m. DBH and age structures of P. forrestii showed multimodal distributions. Its maximum age P. forrestii was 570 years with a DBH of 143 cm. The growth of annual ring width of P. forrestii was slow, and generally decreased with age, whereas the basal area at the breast height increased with age. Established seedlings/saplings were mainly found in unstable micro-habitats. Regeneration of P. forrestii depends on moderate natural disturbances. Finally, we provide recommendations for P. forrestii conservation.

Forest characteristics and population structure of Glyptostrobus pensilis, a globally endangered relict species of southeastern China.

The Chinese water pine Glyptostrobus pensilis is the sole surviving species of the genus Glyptostrobus. It is endemic to southern China, central Vietnam, and eastern Laos, and today it is nearly extinct in the wild. Forest community characteristics and population structure of G. pensilis in China have remained unknown up to now. We investigated six swamp forest stands and analyzed their forest community characteristics (i.e. vertical stratification, species composition, and diversity) and population structure, including the frequency distribution of DBH (diameter at breast height) and age-classes as found in Fujian Province, southeastern China. The vertical stratifications of all the forest stands were rather simple. The remaining wild specimens ranged from roughly 15 to some 357 years for an average of ca. 85 years, with only a few individuals less than 20 years old. Compared with the stands and populations of G. pensilis in Vietnam, the taxonomic compositions of the stands in the two regions were different, except for the dominant species-G. pensilis. The Shannon-Wiener index showed the overstory of each stand had much lower diversity (0.26 on average) in Fujian Province than that (1.97 on average) in Vietnam, whereas the diversity indices were about the same (around 2.41) for the understories in the two regions. Furthermore, we discovered 18 G. pensilis seedlings at the study sites in Fujian Province. This discovery demonstrates that G. pensilis regeneration is extremely poor and its populations are declining, although these populations are relatively healthier than those in Vietnam.

Author Correction: Identifying long-term stable refugia for relict plant species in East Asia.

In the original version of this Article, an incorrect sample size was provided for the number of relict species (443 instead of 442) and the number of relict forests (423 instead of 422). These errors have been corrected in both the PDF and HTML versions of the Article.

Identifying long-term stable refugia for relict plant species in East Asia.

Today East Asia harbors many "relict" plant species whose ranges were much larger during the Paleogene-Neogene and earlier. The ecological and climatic conditions suitable for these relict species have not been identified. Here, we map the abundance and distribution patterns of relict species, showing high abundance in the humid subtropical/warm-temperate forest regions. We further use Ecological Niche Modeling to show that these patterns align with maps of climate refugia, and we predict species' chances of persistence given the future climatic changes expected for East Asia. By 2070, potentially suitable areas with high richness of relict species will decrease, although the areas as a whole will probably expand. We identify areas in southwestern China and northern Vietnam as long-term climatically stable refugia likely to preserve ancient lineages, highlighting areas that could be prioritized for conservation of such species.