Population persistence of a Tertiary relict tree Tetracentron sinense on the Ailao Mountains, Yunnan, China.

The persistence of the Tertiary relict tree Tetracentron sinense Oliv. on the eastern slope of the Ailao Mountains, Yunnan, SW China, was here studied in terms of population structure (size, age) and regeneration patterns. T. sinense occurred in unstable habitats by stream banks, on steep slopes, on scree slopes, or on roadsides near streams in narrow valleys, all places subject to frequent natural disturbances, whereas none were found on stable gentle slopes free of major disturbances at similar altitudes. Further, no established saplings of T. sinense were found in forests having high bamboo (Yushania crassicollis Yi) coverage in their understory. The size and age structure of T. sinense were multimodal. The reproduction of the tree was either by means of abundant minute wind-dispersed seeds or by resprouts in unstable habitats. These populations depended on disturbance or gap regeneration to survive. T. sinense, along with other tree life-forms including evergreen broad-leaved species and conifers, dominated in the forest canopy layer, even reaching the emergent layer in places. Results of the study provide insight into the ecological characteristics and survival mechanisms of this East Asian paleoendemic tree species. The study will provide a scientific basis for recommendations for the conservation of this species and for other Tertiary relict plants having similar regeneration dynamics.

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.

Potential effects of climate change on geographic distribution of the Tertiary relict tree species Davidia involucrata in China.

This study, using species distribution modeling (involving a new approach that allows for uncertainty), predicts the distribution of climatically suitable areas prevailing during the mid-Holocene, the Last Glacial Maximum (LGM), and at present, and estimates the potential formation of new habitats in 2070 of the endangered and rare Tertiary relict tree Davidia involucrata Baill. The results regarding the mid-Holocene and the LGM demonstrate that south-central and southwestern China have been long-term stable refugia, and that the current distribution is limited to the prehistoric refugia. Given future distribution under six possible climate scenarios, only some parts of the current range of D. involucrata in the mid-high mountains of south-central and southwestern China would be maintained, while some shift west into higher mountains would occur. Our results show that the predicted suitable area offering high probability (0.5‒1) accounts for an average of only 29.2% among the models predicted for the future (2070), making D. involucrata highly vulnerable. We assess and propose priority protected areas in light of climate change. The information provided will also be relevant in planning conservation of other paleoendemic species having ecological traits and distribution ranges comparable to those of D. involucrata.

Community Structure and Survival of Tertiary Relict Thuja sutchuenensis (Cupressaceae) in the Subtropical Daba Mountains, Southwestern China.

A rare coniferous Tertiary relict tree species, Thuja sutchuenensis Franch, has survived in the Daba Mountains of southwestern China. It was almost eliminated by logging during the past century. We measured size and age structures and interpreted regeneration dynamics of stands of the species in a variety of topographic contexts and community associations. Forest communities containing T. sutchuenensis were of three types: (1) the Thuja community dominated by T. sutchuenensis, growing on cliffs; (2) the Thuja-Quercus-Cyclobalanopsis community dominated by T. sutchuenensis, Quercus engleriana and Cyclobalanopsis oxyodon, along with Fagus engleriana and Carpinus fargesiana, on steep slopes; (3) the Thuja-Tsuga-Quercus community dominated by T. sutchuenensis, Tsuga chinensis, and Quercus spinosa, on crest ridges. The established seedlings/saplings were found in limestone crevices, on scarred cliff-faces, cliff-edges, fallen logs, canopy gaps and forest margins. The radial growth rate was 0.5-1.1 mm per year. Its growth forms were distorted. It had strong sprouting ability after disturbances. The T. sutchuenensis population thrives on cliffs where there is little competition from other species because of harsh conditions and rockslide disturbances. It is shade-intolerant but stress-tolerant. Its regeneration has depended on natural disturbances.