-->Special Subject of Karst Plants (1)

Photosynthetic physiological response of three plant species to different slope environments in karst forest of Guizhou, China

2016/10/30 0:00:00

In order to gain a better understanding on the different adaptive characteristics of karst plants and to develop reasonable vegetation we studied the carbonic anhydrase(CA)activity, diurnal variation of photosynthesis, response curves of net photosynthetic rate of CO₂ concentration and light intensity, chlorophyll a fluorescence parameters and stable carbon isotope composition of Broussonetia papyrifera, Celtis sinensis and Rubus tsangii which grew in the middle and lower slopes of the karst forest in Puding County, Guizhou Province. Their different photosynthetic physiological response of the three species were also analyzed. The results indicated that in the photosynthesis, B. papyrifera could utilize the atmospheric CO₂ and the intracellular HCO₃^- through the catalysis conversion by CA when the stomatal conductance decreased. With higher activity of CA, B. papyrifera growing in the lower slope had higher HCO₃^-utilization efficiency. Besides, B. papyrifera growing in the lower slope exhibited higher light utilization efficiency under low light intensity, which might be attributed to its higher CA activity in the lower slope. B. papyrifera showed better adaptability to lower slope compared to middle slope. The photosynthetic inorganic carbon assimilation efficiency of C. sinensis was the lowest, which only used the atmospheric CO₂ as inorganic carbon resource for the photosynthesis. Since the growth rate of C. sinensis was very slow, the requirement for inorganic carbon was the lowest, and it could maintain the stable inorganic carbon assimilation rate. C. sinensis growing in the middle slope exhibited higher net photosynthetic rate and light utilization efficiency, and it showed better adaptability to the middle slope compared to lower slope. R. tsangii mainly utilized the atmospheric CO₂ in the photosynthesis process. The light utilization efficiency and net photosynthetic rate of R. tsangii in the middle slope were higher. R. tsangii exhibited better adaptability to middle slope. The results provide a scienti-fic basis for reasonably selecting and designing plant species during the revegetation process in the karst ecologically vulnerable forest region.

Species composition of woody plants in evergreen-deciduous broad-leaved karst forests, Southwest China

2016/10/30 0:00:00

Evergreen and deciduous broad-leaved mixed karst forest(EDBLKF for short), locating in the southwestern region of subtropical limestone karst region, China, is one of the most unique types of karst forests in the world. The limestone karst forests in this region display different characteristics such as various community structures, high species richness, abundant endemic biological species, etc. owing to the special limestone soils of abundant Ca and higher pH value, the various heterogeneous habitats. The permanent plot-based approach to community analysis is fundamentally important for revealing mechanisms of biodiversity maintenance. In this study, community structure and species composition were investigated and analyzed using a 25 hm² permanent plot in Mulun National Nature Reserve, Guangxi Zhuang Autonomous Region. Based on the standard field protocol of the Center for Tropical Forest Sciences(CTFS), all free-standing individuals with DBH(diameter at breast height)≥1 cm were tagged, mapped and identified to species in this plot. The results were as follows:(1)A total of 110 370 individual trees(144 679 individuals with branches), belonging to 254 species,161 genera and 64 families were recorded in the plot.(2)The top 15 species with most individuals accounted for 78.46% of the total individuals in the plot. One hundred species were considered to be rare species representing by no more than one tree per hectare, they accounted for 39.37% of the total species.(3)The DBH size-class structure of all species in the plot exhibited a reverse J-shaped pattern, indicating good regeneration across the community.(4)There were 26 species with important value ≥1, which accounted for 10.24% of the total individuals in the plot. The three most dominant species were Cryptocarya microcarpa, Itoa orientalis and Lindera communis.(5)There were total 34 309 woody plants of 204 sprouting species, belonging to 127 genera and 51 families in the plot, accounting for 80.32%, 14.42%, 78.88% and 79.69% of the total number of individuals, species, genera and families, respectively. In conclusion, with rich species composition and a mature community structure, the EDBLKF in Mulun region is typical characteristic of this vegetation type.

Species composition and diversity of different shrub communities in West Guangxi

2016/10/30 0:00:00

Ten different shrub communities distributed in nine counties of West Guangxi were investigated through field survey. The analysis of their importance values(IV), species compositions, biomass and diversity showed that diverse shrubs were widespread in the areas with 87 shrub species belong to 78 genera and 47 families, and 56 kinds of herbs belong to 48 genera and 31 families, being recorded. Species from Eup horbiaceae, Rosaceae, Verbenaceae dominated the communities. The communities mainly contained shrub and herb layers. The shrub layer coverage ranged from 30% to 70%, average height 0.75 to 3.25 m, few outliers with height > 5 m. The herb layer coverage was 3% to 90%, average height 0.4 to 1.3 m, often below 1 m. Dominant species' important value, diversity and grass growth varied among different shrub populations, and monodominant communities generally had higher dominant species' important value than polydominant communities, while the latter had higher diversity index, more species, representing even distribution and complex stable structures. Species' richness, shannon indices, dominance indices and evenness indices were positively and significantly correlated. Community No. 9(Quercus fabri + Coriaria nepalens + Pyracantha fortuneana)and No. 10(Vitex negundo + Cipadessa baccifera)had higher species richness and diversity. This provides the information for shrub resoruce conservation in West Guangxi.

Principal factors influencing the biomass allocation of Phyllostachys glauca, a dominant species in the limestone mountain

2016/10/30 0:00:00

To clarify the effects of density and soil environmental factors on the biomass allocation of Phyllostachys glauca in limestone mountain, nine plots were set in Ruichang City, Jiangxi Province, China. The structural component biomass and the ramet biomass as well as the density of P. glauca forest were measured. Meanwhile, soil environmental factors including water content, soil depth, rock coverage, pH, electrical conductivity, total nitrogen and total phosphorus were determined. The results of correlation and regression analysis were as follows:(1)The density of P. glauca forest was significantly associated with the stump mass fraction(S_uMF)and the correlation coefficient was 0.66(P<0.05), while it had no relevant relation with other indexes of biomass allocation, such as leaf mass fraction(LMF), branch mass fraction(BMF), stem mass fraction(S_eMF), rhizome mass fraction(R_hMF), root mass fraction(S_oMF)and root shoot ratio(RSR). The soil environmental factors were also significantly correlated with the biomass allocation indexes. Two principal components extracted from the seven soil environment factors were transformed to principal component variables Z1 and Z2. Z1 was significantly correlated with LMF, S_eMF and S_uMF(P<0.05), and Z2 was significantly correlated with R_hMF(P<0.05).(2)Considering the close correlation between the density and the soil environmental factors(P<0.05), the partial correlation analysis was employed. The results showed that the density and biomass allocation were not significantly correlated(P>0.05)when the soil environmental factors were controlled; while the soil environmental factors and the biomass allocation were significantly correlated(P<0.05)when the density was controlled. Moreover, stepwise regression analysis also showed the similar result that the density was excluded from the regression equation. It indicated that soil environmental factors including water content, soil depth and soil nutrient were the principal factors influencing the biomass allocation of P. glauca, while the influence of density on the biomass allocation was the indirect influence of soil environmental factors.

Anatomical structure and environmental adaptability of Cymbidium cyperifolium in karst area

2016/10/30 0:00:00

The leaf and root anatomical structures of Cymbidium cyperifolium in Yachang Orchids Nature Reserve of Northwest Guangxi were studied by using traditional paraffin section, and its adaptability to karst environment was also analyzed. The results were as follows:(1)The upper epidermal cells of C. cyperifolium were covered with thick cuticle. The stomata were distributed in lower epidermal cells and protruding on epidermal cells. All epidermal trait features had significance difference among different parts of leaf blade. The highest stoma density, stoma index and length of stoma were in the lower part of leaf blade, and maximum density of epidermal cells was in the upper part of leaf blade. The leaves of C. cyperifolium were equifacial leaf and the mesophyll was not differentiated into palisade and spongy tissues. The leaf vein was distinct parallel venation. Thick and thin veins were interactively distributed.(2)The root cross section was composed of root velamen, cortex and stelae. Root velamen cells lived and arranged closely. Cortex was composed by parenchyma cells. Root vascular bundle belonged to radial vascular bundle. The mycorrhiza was thick and had few root hairs. The symbiotic fungi mainly distributed in root velamen and cortex, and infection of mycelium was invaded through the parenchyma intercellular space and the passage cells of cortex by hyphae.(3)The leaf and root anatomical structures of C. cyperifolium not only had hygrophyte features, such as relatively thinner leaf blade, less and protruding stoma and higher ratio of shoot mass to root mass, but also had xerophytes features, such as thicker cuticle, developed mechanical tissue, tensely cell structure, having crystal cell, fleshy root had velamen, obviously thickening cell wall of inner and outer cortex. These structures of C. cyperifolium represent the adaptability to living environment with water deficit, obvious dry and wet seasons and understory gravel soil.

Chemical constituents from the branches and leaves of Croton euryphyllus

2016/10/30 0:00:00

Croton euryphyllus(Euphorbiaceae)is mainly distributed in the karst region of Southwest China and has been used as a folk medicine to cure traumatic injury and kill insects. In order to clarify the chemical constituents of C. euryphyllus, the ethanol extract was separated by the chromatography(silica gel, Sephadex LH-20 and HPLC)and sixteen compounds were isolated. Their structures were elucidated as: isocrotocaudin(1), jatrophoidin(2), teucvidin(3), isoteucvin(4), teucvin(5), labd-13E-ene-8β,15-diol(6), 7-oxo-β-sitosterol(7),(22E)-5α, 8β-epidioxyergosta-6, 22-dien-3β-ol(8), stigmast-4-en-6β-ol-3-one(9), olean-12-en-2α,3β-diol(10), scopoletin(11), vomifoliol(12), lyratol F(13), apocynol A(14), apigenin(15), aurantiamide acetate(16). All compounds were firstly isolated from this plant, and compounds 8-16 were isolated from the genus Croton for the first time.