Hypericumliboense (Hypericaceae), a new species from Guizhou, China.

Hypericumliboense M.T.An & T.R.Wu, sp. nov. (Hypericaceae) is a newly described species found in the Maolan National Nature Reserve of Guizhou Province, where it grows in rocky habitats without soil on karst mountain tops. In this study, key morphological characters were compared between the new species and the other known Hypericum species of Hypericaceae. DNA sequences were extracted from the leaves of the new species, with nuclear gene sequences (ITS) generated to reconstruct phylogenetic trees and describe its phylogenetic position in relation to other species of Hypericum. Our results show that the proposed new species has the typical characteristics of the genus Hypericum in morphology being similar to Hypericummonogynum, but differing in its sessile and semi-clasped leaves, long elliptical to long circular leaf blades, thickly papery to thinly leathery, with entire and wavy leaf margins. The abaxial side of the leaves is covered with white powder, giving them a grey-white appearance. The main lateral veins of the leaves are 8-15-paired, and the midvein on both sides is convex. The main lateral veins and midvein branch are conspicuous, with tertiary venation forming a network on the leaf surface and appearing prominently sunken. The inflorescences are 1-3-flowered, with a large calyx and conspicuous veins. The molecular phylogenetic analysis (PP = 1.00) provided substantial evidence for the proposition of H.liboense as a new species within Hypericum. Morphological and molecular evidence is presented, corroborating the proposition of the new species, including a comprehensive account of the distinctive morphological attributes of H.liboense, along with its key distinguishing features from similar species.

[Evaluation on degradation of Karst forest community and human disturbance].

Fire, reclamation, herd, and cut led to degradation of Karst forest in Guizhou Province. Five indexes as height, dominance, percentage of asexual individual, biomass, and percentage of shade-tolerant for evaluating community degradation were selected. Degraded communities were divided into six degraded grades (A-F). Community structure and function fluctuated normally in climax (A) under nature force or light human disturbance. While effect of disturbance was preponderated over the range of community fluctuation, climax community degraded evidently, and degraded degree of communities increased gradually. Degraded grades of communities were consistent to succession stages of degraded community. In degraded process, the key factor was decrease of biomass and shade-tolerant species. Degraded communities due to fire, herd, and reclamation were distributed in grades C-F, and degraded community due to cut was in grades B-C. Amount of asexual individual was influenced by disturbance type, and the amount in degraded communities due to fire and cut was more than that due to reclamation and herd. Degraded degree of different disturbed community was in order of cut community < cleared community < herded community < fired community.