-->Special Column： Karst Plants Research

Structural and functional diversity of rhizosphere microbial community of Heteroplex

2018/2/6 10:48:16

Heteroplex is a typical endemic genus of karst rocky mountainous area in Guangxi, and rhizosphere microorganism is one of the most direct representations of its ability to absorb and utilize soil nutrients and adapt to the harsh soil environment. In this study, DGGE and Biolog methods were used to study the rhizosphere and non-rhizosphere microbial diversity of Heteroplex. The results showed that the values of pH and alkali nitrogen content in the rhizosphere were hi-gher than those in the non-rhizosphere. The results of DGGE showed that two common bacterial groups were same in the rhizosphere and non-rhizosphere of Heteroplex, but the numbers were different. The bands in DGGE profile of the three species were less than non-rhizosphere. Rhizosphere and non-rhizosphere microbial community of each species were similar. The results of Biolog showed that the rhizosphere microorganisms of H. sericophylla had the strongest ability to use carbon source, and the non-rhizosphere of H. impressinervia was the weakest, and the ability of utilize carbon source of other rhizosphere and non-rhizosphere microbial community was close. The microbial diversity index of rhizosphere microorganisms was higher than that of non-rhizosphere, and the dominance index was the same as that of non-rhizosphere, the richness and evenness index are similar to the dominance index. The carbon sources used in non-rhizosphere microbes were mainly sugars, carboxylic acids and amino acids. The ability of utilize carbon source of four rhizosphere microorganisms were higher than non-rhizosphere. Cation exchange capacity, clay content and alkali nitrogen were the most important factors affecting the microbial carbon source utilization model of rhizosphere microorganisms. In general, the soil physical and chemical properties have an important effect on rhizosphere microbial community diversity of Heteroplex, and the activity of the rhizosphere microorganisms and fertility level were improved by secreting compounds such as carboxylic acid and sugar.

Temporal-spatial dynamics for plant community structure and species diversity of rocky desertification ecosystem in karst plateau basin, southwest China

2018/2/6 10:48:16

Karst rocky desertification has become a very serious eco-environment issue in southwest China, severely hindering the local sustainable development of economy and society. Vegetation restoration is key to the rehabilitation of karst rocky desertification and a series of comprehensive controls for rocky desertification have been carried out in karst areas. But there are very short of the studies on plant community structure and species diversity of karst plateau basin ecosystem in southwest China. And the responses of plant community structure and species diversity to the succession of rocky desertification are still unclear. All these seriously hinder the control of rocky desertification. In the present study, a typical rocky desertification ecosystem of karst plateau basin, Boluo small watershed in Qingzhen City of Guizhou Province, was selected as experiment site. And five sample plots were set up for each degree of karst rocky desertification, namely, nil, potential, slight, and moderate. Then, the plant community structure and species diversity were investigated by ecological survey method from 2013 to 2015. The results showed that the plant community structure of rocky desertification ecosystem was very simple, only 58 plant species including 28 herbaceous species(belonging to 18 families, 24 genera)and 30 shrub species(belonging to 17 families, 25 genera)were recorded, and 82.36% of them belong to monotypic genus. There are obvious differences of plant community structure between different degrees of rocky desertification, and the plant population density among different degrees of rocky desertification also varies obviously, with the order of slight > moderate > potential > nil. The indices of plant diversity, evenness, richness and dominance all are low, and each of them has no coupling relationship with the rocky desertification. Along with the increase of the years, the plant community height, ground diameter, population density, and shrub biomass show an increasing trend, but there are not significant differences between adjacent years. The human disturbances on the ecosystem in study area getting weaker, the importance of dominant species tends to decrease, and the vegetation shows a trend of positive succession. The results have important values for the restoration of rocky desertification in karst plateau basin, southwest China.

Seasonal change of soil nitrogen content in reed vegetation of Huixian Karst Wetland,Guilin,China

2018/2/6 10:48:16

In order to investigate the dynamic variation characteristics of soil nitrogen content in soils of reed community in Huixian Karst Wetland, the different levels of soil samples(0-10 cm, 10-20 cm and 20-30 cm)were analyzed in laboratory. The results showed that organic nitrogen played a dominant role in the content of total nitrogen. The seasonal changes characteristics of total nitrogen in 0-10 cm soil layer were consistent with that of available nitrogen content in 0-20 cm soil layer, which had higher content in summer, followed by autumn and spring, with the lowest contents in winter. The order for seasonal variation of total nitrogen in 10-20 cm and 20-30 cm soil layers was spring, summer, autumn and winter, the same as organic nitrogen content. The trend for seasonal changes of organic nitrogen content in 0-10 cm soil layer was similar to available nitrogen in 10-20 cm soil layer, which showed that the content was higher in autumn, followed by summer and spring, with the lowest contents in winter. The variation of soil nitrate nitrogen showed a single peak curve during growing season, increased first and then decreased, which was the same to ammonium nitrogen content in 0-20 cm soil layer. The seasonal variation of ammonium nitrogen in 20-30 cm soil layer was consistent with microbial biomass nitrogen content in 0-20 cm soil layer, which showed that the contents were the highest in sping, lower in both autumn and summer, and the lowest in winter. The content of ammonium nitrogen was higher apparently than that of nitrate nitrogen, the changing trends of ammonium nitrogen in each soil layer appeared in an anomalous “M” shape. The seasonal difference of microbial biomass nitrogen in 10-20 cm soil was evident, and decreasing amplitude in season was autumn, spring, summer and winter in turn. The characteristics of various nitrogen forms in soils of reed community in Huixian Karst Wetland showed distinct differences with seasons, and the lowest in winter. Soil nitrogen content are important indicators for reflecting the status of soil nutrients and quality. In general, the contents and distributions of total nitrogen, ammonium nitrogen, nitrate nitrogen, available nitrogen, organic nitrogen, microbial biomass nitrogen in soils of reed community in Huixian Karst Wetland were maily influenced by multiple factors, such as plant absorption at different growth periods, soil organic carbon, the nutrient return of the plant litters, average monthly temperature, water conditions, soil organic nitrogen mineralization and so on. This study provides scientific reference for recovery of ecological fumtions and sustainable development and utilization of Huixian Karst Wetland Park.

Photosynthetic physiology characteristics of three afforestation tree species in Guizhou Yushe National Forest Park

2018/2/6 10:48:16

Karst is widely distributed in our country, its ecological environment is fragile, and vegetation restoration is an effective way to repair and reconstruct the karst fragile ecological environment, but the key to vegetation restoration is to screen suitable plant that can adapt to karst fragile environmental conditions. To study the photosynthetic physiology and ecology of afforestation plant species in karst area, so as to provide scientific basis for the protection and exploitation of mountain forest resources. In this study, three afforestation plant species, Sorbus alnifolia, Litsea elongata var. subverticillata and Populus davidiana, were collected from Yushu National Forest Park of Guizhou Province. Plant photosynthesis and chlorophyll fluorescence, leaf carbonic anhydrase activity and chlorophyll content and stable carbon isotopic composition, and the soil physical and chemical properties of plant growth location were determined, and the karst ecological adaptability of three plant species was comprehensively analyzed. The results showed that the net photosynthetic rates of Sorbus alnifolia and Populus davidiana were significantly higher than that of Litsea elongata var. subverticillata, which were related to its higher stomatal conductance and photochemical efficiency. Populus davidiana had higher activity of carbonic anhydrase and chlorophyll content, showing a higher water use efficiency. Sorbus alnifolia and Populus davidiana, dominated by the photosynthetic activity, and are limited by light intensity and temperature, as the fast-growing plants can be selected to large-scale grown in good light conditions to increase economic income and improve the fragile habitats in karst areas. However, the photosynthetic rate of Litsea elongata var. subverticillata was lower than that of other two plant species, combined with its highest photosynthetic capacity under low photosynthetic active radiation, this medical plants can be as the shade plant to raise the vegetation coverage and increase local economic income. The results provide a scientific basis for the protection and exploitation of mountain forest resources.

Population structure and distribution pattern of Cyclobalanopsis glauca at different topographic sites in Maolan karst forest

2018/2/6 10:48:16

Cyclobalanopsis glauca is one of the constructive species and dominant species in subtropical evergreen broad-leaved forest. C. glauca is also the dominant species in karst forest of Maolan National Reserve and plays an important role in the ecosystem. In order to reveal population dynamics of C. glauca, different topography sites(funnel, hillside, valley)in Maolan National Reserve were selected as the objects of research. The population structure was studied by the method of tree class structure instead of age structure, and survival curves of C. glauca was drawn. The distribution patterns of the population were measured by applying aggregate indices, including variance/mean ration(deviation index C_X), negative binomial parameter(K), clumping index(I), mean crowding index(m^*), patchiness index(PAI)and aggregation index(C_a). The population structure and renewal potential of C. glauca in Maolan National Reserve was evaluate. The results showed that Class Ⅱ saplings of C. glauca were absolute predominance, the seedlings were the second, and there were some adult individuals, the population had strong self-renewal capacity, characterized by a growing population. The survival curve tended to be type Deevey Ⅲ. Among three topography sites, there was complete diameter class structure of C. glauca in valley, but the diameter class structures were not complete in hillside and funnel. It showed that the number of seedlings were less than saplings, the number of saplings was the largest, the number of middle and large trees were the least, the diameter structure of C. glauca was high in the middle and low in both ends. The distribution pattern of C. glauca population showed random distribution at different topography sites, and changed from clump to random with the development of the population. It showed that seedlings and saplings were clump distribution, but middle size and large trees were random distribution. The population structure and distribution pattern of C. glauca among three topography sites are different. This study will provide scientific support for C. glauca protection and management in Maolan karst forest.

Fruit yield and characters of wild Malania oleifera, a rare plant species in southwest China

2018/2/6 10:48:17

Malania oleifera, an endemic plant species, is naturally distributed in karst region of southeast Yunnan and west Guangxi, China. This plant is a potential species with high economic value as its seed oil contains rich nervonic acid, and is also an excellent tree for the restoration and reconstruction of vegetation in karst region. Much attention has been paid to exploitation and utilization of this species in recent years. In order to understand fruiting characters of wild trees, we analyzed the fruit yield of wild trees, fruit and pit characteristics from six sites. The results were as follows:(1)Fruit yield was significantly different among wild trees. The coefficient of variation(CV)was 136.38%. There was positive correlation between fruit yield and tree crown.(2)The mean size of fruit was 37.10-40.36 mm in longitudinal diameter, and 41.15-45.03 mm in transverse diameter of CV ranged from 7.28% to 9.31%. The mean fruit weight was 35.77-47.29 g with a range in CV from 18.99% to 21.44%.(3)The mean size of pit was 27.50-31.69 mm and 30.94-34.16 mm respectively in longitudinal and transverse diameter. CV was from 6.47% to 10.99%. The mean pit weight was 14.03-18.77 g, and CV was from 17.37% to 22.68%.(4)The mean longitudinal thickness of pericarp was 4.33-4.80 mm, and transverse thickness was 5.10-5.44 mm. Their CV was 12.92%-26.91%. The mean weight of pericarp was 21.62-28.51 g, and CV was 20.01%-24.12%. These results indicate that the yield, size and weight of fruits of wild Malania oleifera have abundant phenotypic diversity, which can provide various source of excellent character selection for oriented cultivation and exploitation.

Effects of Fortunella margarita inoculated with AMF on rhizospheric bacterial community diversity based on DGGE

2018/2/6 10:48:17

To overcome the soil infertility and poor crop output problem of karst region, we chose Funneliformis mosseae(F.m)and Claroideoglomus etunicatum(C.e)as AMF inoculants and two types of soil in karst region as potted matrix, the bacterial community diversity and growth of Fortunella margarita were investigated by PCR-DGGE(denaturing gradient gel electrophoresis)technique and other conventional approaches. The results were as follows: Comparing to no AM fungi treatment, the colonization rate of root system of F. margarita such as F, m, v inoculated with either C.e or F.m treatment increase significantly. No matter in either type of soil, C.e treatment are the highest. In addition, rhizospheric soil enzyme activities including invertase, phosphatase, protease and urease with either C.e or F.m treatment increase significantly. Among them, activities of protease and urease are the highest in lime soil(LS), and that of invertase and phosphatase in acid soil(AS)are higher than that in LS, the differences are significant with each other(P<0.05). Either in AS or LS, the four kinds of soil enzyme activities with C.e are the highest. In terms of bacterial diversity, the bands number of bacterial DNA with AMF of DGGE profile enriched, and the index of richness(R), diversity(H)and evenness(E)with AMF are higher than no AMF treatment. No matter in either type of soil, value of R, H and E with C.e are the highest. Additionally, based on the results of sequence analysis to DNA dominant bands of DGGE profile, all dominant bacterial strains are phylogenetically closen to uncultured microbes, including Acidobacterium, Proteus, Rhizobium and Actinomyce, the similarity of each is above 97%. Moreover, comparing to no AM fungi treatment, biomass of Fortunella margarita inoculated with either C.e or F.m treatment increases significantly, C.e treatment are the highest in AS. In conclusion, comparing to F.m, C.e represents better efficiency for F. margarita in karst region. AMF can enhance activities of four rhizospheric soil enzyme, stimulated diversities of soil bacteria population. As the result, plant biomass increase. It provides the information for improving growth of F. margarita by facilitating the conversion and dynamics of nutrients such as C, N, P and others.