-->Special Column: Karst and Karst Tiankeng Plant Research

Research on flora of seed plants in Dashiwei Karst Tiankeng Group of Leye, Guangxi

2020/7/14 15:43:41

Dashiwei Karst Tiankeng Group, which lies in Leye County, Guangxi(Global GeoPark), is the most typical collapsing Tiankeng group. Many species survived in the relative isolated habitats in karst Tiankeng group. However, the flora of the area left insufficiently known because some of the karst Tiankeng groups are difficult to reach. Based on available data and further field surveys including transect lines and quadrats covering the whole area and interior of main karst Tiankengs, the characteristics of the flora of seed plants were analyzed. The result were as follows: Native seed plants in Dashiwei Karst Tainkeng Group was abundant and various, including 863 species belonging to 445 genera and 137 families. In terms of genus and family level, tropical element was the main floristic geographical components. Species endemic to China were rather poor. Either the ratio of tropical families to temperate families or the ratio of tropical genera to temperate genera was smaller in Dashiwei Karst Tiankeng Group than that of the whole Leye-Fengshan Global Geopark. The seed plant composition of Dashiwei Karst Tiankeng Group can better reflect the original composition of the past. Temperate floristic components used to be more abundant than they are today, which is a persuasive evidence of global warming. In light of 82 species of rare and endangered plants conserved(including 67 wild orchids belonging to 30 genera), Tiankeng group has become a “refuge”for the existing rare and endangered species.

Effects of vegetation restoration on soil aggregate associatedorganic carbon and carbon pool management index in karst trough valley region

2020/7/14 0:00:00

In order to understand the effects of vegetation restoration on soil structure, accumulation of soil organic carbon(SOC)and carbon pool management levels in karst trough valley region. Three land use patterns including abandoned farmland, woodland and grassland were chosen. Soil samples at 0-20 cm depth were collected and separated into aggregate size fractions. The aggregate amounts, SOC in whole soils and aggregates and easily oxidized organic carbon(EOC)contents were determined. The results were as follows:(1)Compared with abandoned farmland, the mean weight diameter(MWD), the mean geometric diameter(MGD)and 2-5 mm aggregate amounts significantly increased, but 0.5-1 mm and <0.25 mm aggregate amounts significantly decreased in woodland and grassland.(2)The SOC content in soil aggregates decreased as follows: woodland > grassland > abandoned farmland and generally increased with the increase in aggregate size class; The SOC content was mainly attributed by 2-5 mm aggregate associated organic carbon contents in woodland and grassland, but the contribution in abandoned farmland was dominated by <0.25 mm size fraction. The results suggested that SOC accumulation is mainly due to the increase of organic carbon in 2-5 mm aggregate and the conversion from smaller aggregates to larger aggregates.(3)The SOC, EOC contents and carbon pool management indexes(CPMI)in woodland and grassland were greatly improved relative to those of in abandoned farmland. The responses of EOC and CPMI were sensitive to land use changes; Soil EOC can be used as an effective indicator of early changes in SOC status brought about by vegetation changes, and soil CPMI is a good indicator to reflect the impact of vegetation changes on SOC and EOC.

Growth and nodule biomass characteristics of Alnus formosana in karst mountains

2020/7/14 15:43:41

Understanding the growth and nodule biomass characteristics of Alnus formosana on karst mountains is very important for vegetation restoration. Typical sample methods were used to investigate 4.5 year old populations of Alnus formosana, Zenia insignis and Acrocarpus fraxinifolius. The results were as follows: On average, Alnus formosana had DBH 8.39 cm, height 7.72 m, volume 0.027 1 m^3and crown width 3.18 m, significantly higher than those of Zenia insignis and Acrocarpus fraxinifolius(P<0.01). Mean crown width of A. formosana was up to 6.01 m, 106.53% or 70.25% more than that of Zenia insignis or Acrocarpus fraxinifolius. Alnus formosana proved to be a fast-growing species on karst mountain. The root nodule growth of A. formosana was analyzed and its mean nodule biomass was 52.77 g per tree. The nodules dispersed within the range of crown projection around tree trunk. Nodule biomass at place < 50 cm from tree trunk was similar to that 50 cm to 100 cm away from the tree trunk, and the outer circle( >100 cm from tree trunk to outer bound of crown projection)contained the most nodule biomass. The three segments on average contained 15.7%, 16.9% and 67.4% of the total nodule biomass, respectively, and large nodules(diameter ≥ 1 cm)always distributed in the outer circles. For nodule vertical distribution, they mainly dispersed in 0-20 cm soil layer, and few nodules occured in 20-40 cm soil layer. A. formosana showed good nodulation and nitrogen fixation characteristics on karst mountain. This result provides scientific basis for recommending A. formosana afforestation in karst mountains.

Leaf functional traits of Zanthoxylum planispinum var. dintanensis at different altitudes in dry-hot valley rocky desertification region

2020/7/14 15:43:41

In order to expound the law of altitude differentiation of leaf traits of Zanthoxylum planispinum var. dintanensis plantation, to explore the adaptation strategies in different altitude habitats. This study measured nine leaf traits such as leaf thickness, specific leaf area and leaf total nitrogen, and eight soil chemical indexes such as organic carbon, total nitrogen and total potassium that aim to analyze the correlation of leaf functional traits of Z. planispinum var. dintanensis and its differentiation with altitude. The results were as follows:(1)With the increase of altitude, the specific leaf area, leaf total phosphorus and leaf total potassium of Z. planispinum var. dintanensis increased first and then decreased while leaf dry matter content, leaf total nitrogen and leaf organic carbon decreased first and then increased gradually; and leaf thickness, leaf area and leaf water content increased gradually.(2)There was a significant correlation between the leaf functional traits of Z. planispinum var. dintanensis. Leaf total nitrogen had a significantly negative with total phosphorus in leaves, significant positively with leaf thickness. Leaf dry matter content has a significant inhibitory effect on specific leaf area and leaf water content.(3)The effect of soil factors on the leaves of Z. planispinum var. dintanensis was available nitrogen > available potassium > organic carbon, while other soil factors had less effect on it. This study indicates that Z. planispinum var. dintanensis mainly enhances the ability to acquire resources and resist external environmental stress by enhancing defense function traits and coordinating leaf nutrient content survival strategies. It has a strong dependence on soil nutrients, and its drought adaptation is drought avoidance. This study provides a scientific basis for the rejuvenation, high yield and stability of Z. planispinum var. dintanensis plantation and ecological restoration in karst rocky desertification area.

Differences of plant diversity and soil physicochemical properties in Maolan karst forest under different topographic conditions

2020/7/14 15:43:41

To explore the difference and relationship between plant diversity and soil physical and chemical properties in different topography of Maolan karst forest, and to provide scientific basis for the maintenance mechanism of species diversity in Maolan karst forest. The results were as follows:(1)There were differences in species composition of woody plants in different topographies. There were 78 species of woody plants belonging to 65 genera and 35 families in hillside, 89 species of woody plants belonging to 64 genera and 38 families in valley, and 84 species of funnel woody plants belonging to 61 genera and 35 families. Mean while, the magnitude of richness index, diversity index and evenness index was valley > funnel > hillside, while the magnitude of dominance index was hillside > funnel > valley.(2)There were significant differences in soil physical properties between different topographies(P < 0.05). Among them, soil bulk density and non-capillary porosity were hillside > valley > funnel, while natural water content, field water holding capacity, total porosity and capillary porosity were funnel > valley > hillside.(3)Except for total potassium(K), most soil nutrient indicators showed that funnel was significantly higher than valley and hillside, that is funnel > valley > hillside.(4)Redundancy analysis showed that plant diversity was correlated with soil physical and chemical properties, and plant diversity indexes in different topographies were significantly affected by soil physical and chemical properties. The results indicate that the complexity of topographic conditions and the difference of soil physical and chemical properties in Maolan karst forest are one of the reasons for the diversity of microhabitats and rich species composition in this area.

Biomass allocation and allometric analysis of Vetiveria zizanioides in different planting years on coal spoil-heaps

2020/7/14 15:43:41

Vetiveria zizanioides is a good ecological restoration species in mining wasteland. The study on relationship between biomass allocation and allometry will contribute to deepen understanding the survival strategy and ecological function of V. zizanioides in mining area. V. zizanioides planted on coal spoil-heaps of Dahe Coal Mine in Liupanshui City of Guizhou Province for 4, 5, 8, 15 a were used as research objects, the total biomass were obtained by using excavation and weight methods, and organ biomass, allocation ratios and the allometric relationships among the four different planting years were compared. The results were as follows:(1)The biomasses of roots, stems and leaves increased firstly and then decreased with the increase of planting years, and reached the maximum at 5 a of planting and the minimum at 15 a of planting.(2)Stem peaked in biomass distribution ratio in the 15 a of planting(37.3%), while leaf did in the 5 years of planting(36.1%), and the root did not change with the increase of planting years(30%).(3)In planting for 4, 5, 8 a, the total biomass of aboveground biomass was in allometric relationships with root and leaf biomasses. In planting for 5 a, the leaf area was in allometric relationships with root and leaf biomasses, and was in isometric growth relationship with stem biomass. There was no consistency between allocation pattern and allometric relationship in different planting years, but it reflected the characteristics of V. zizanioides biomass allocation on showed its special growth, and would provide theretical reference for ecological management of V. zizanioides on coal spoil-heaps.