| The karst area in southern China has a wide distribution area.It is the most typical karst development area in the world and the most concentrated and continuous area.At the same time,it is also a typical ecologically fragile area in the world.Due to unreasonable human activities in the area,special above-ground and underground dual hydrological structures and rich joint fractures in carbonate rocks,the soil erosion in this area is serious,the degree of rocky desertification is deepened,the soil water leakage is intensified,and the surface is dry and lacks water,temporary droughts and seasonal droughts occur alternately and frequently,causing plants in this area to suffer drought stress and affecting plant growth and quality.Based on the basic principles of geography,botany,biochemistry,agronomy,and nutrition,combined with water stress theory,ecosystem theory,agricultural plant cultivation theory and plant nutrition theory,in the mountainous area of Guizhou Plateau,which represents the overall structure of karst ecological environment in southern China.Choose Bijie Saraxi Research Area,Guanling-Zhenfeng Huajiang Research Area and Shibing Karst Research Area.Through research methods such as literature analysis method,indoor simulation experiment method,field test method,analysis of variance,correlation analysis method,principal component analysis method,multiple stepwise regression analysis method,redundancy analysis method,membershipfunction method,etc.,based on the background survey in 2017-2020.In the Bijie Salaxi Research Area,which is dominated by the karst plateau,plants such as Trifolium repens and Morus alba were selected,and Medicago sativa and Broussonetia papyrifera were selected in the Guanling-Zhenfeng Huajiang Research Area dominated by the karst plateau canyon and Lolium perenne and Miscanthus sinensis were selected in the Shibing karst research area were tested in pots to simulate drought stress.In the experiment of drought stress,four gradients of control check(CK),light drought stress(LS),moderate drought stress(MS)and severe drought stress(SS)were set up to measure the morphological growth and physiological and biochemical indexes of the grass and shrub plants,and these indexes were used for comprehensive evaluation of drought resistance to select the plants with strong drought resistance.At the same time,field experiments were conducted to explore the relationship between plant nutritional value and drought stress,and to verify indoor results based on field experiments.From 2017 to 2020,13 consecutive observations and data collections were conducted in 6 sample plots in three research areas,and 55 indexes of 456 samples were analyzed experimentally.The whole chain design,integrated deployment and sub module promotion research work are closely focused on the basic frontier research,common key technology research and development,application demonstration and industrialization promotion of droughtadaptation and quality improvement of grass irrigation in rocky desertification.In order to provide theoretical basis and decision-making reference for ecological environment protection,vegetation restoration and plant selection and breeding in karst area,systematic research should be carried out from the aspects of drought stress adaptation of rock desertification grass and shrub and its interaction with quality,technology research and development and application demonstration verification of rock desertification grass and shrub cultivation and quality improvement,etc.(1)The response mechanism of plant height,specific leaf area(SLA),leaf area(LA),chlorophyll,leaf nitrogen content,leaf relative water content(LRWC)?net photosynthetic rate(Pn)?transpiration rate(Tr)?stomatal conductance(Gs)?cellular CO2 concentration(Ci)?maximum net photosynthetic rate(Pn max)? dark respiration rate(Rd)? light compensation point(LCP)?apparent quantum efficiency(AQY)and light saturation point(LSP)decreased with the increase of drought degree,showing a negative correlation,while leaf dry matter content(LDMC)?leaf thickness(LT)?water use efficiency(WUE),relative conductivity and malonaldehyde(MDA)increased with the increase of drought degree,showing a positive correlation;Under severe stress,the highest LRWC was Broussonetia papyrifera,followed by Morus alba and Miscanthus sinensis.The relative conductivity value of Lolium perenne>Broussonetia papyrifera > Morus alba > Trifolium repens >Miscanthus sinensis> Medicago sativa)showed that the membrane system of awn and alfalfa leaves had strong tolerance and drought resistance.However,the damage of cell membrane permeability system of Lolium perenne and Broussonetia papyriferaleaves was the most serious after drought stress,and the membrane permeability was enhanced,and the drought resistance ability was weak;MDA content in leaves was Miscanthus sinensis >Medicago sativa> Morus alba >Broussonetia papyrifera> Trifolium repens> Lolium perenne.(2)Through the method of membership function,the comprehensive evaluation results of drought resistance of 6 kinds of grass irrigation were as follows: the drought resistance of 6 species of grass and shrub plants in three research areas was evaluated comprehensively by the weighted average value of membership function of 6 morphological growth and physiological indexes: the order of drought resistance ability from large to small:Broussonetia papyrifera > Trifolium repens > Morus alba >Morus alba>Miscanthus sinensis > Medicago sativa,in which the weighted average value of membership function of Broussonetia papyrifera was 0.828,which was the plant with strong drought resistance characteristics;the second was Trifolium repens,whose membership function value is 0.620,which belongs to drought resistant plants;the weighted average value of membership function of Morus alba,Loliumperenne and Miscanthus sinensis was 0.550,0.492 and 0.370,respectively.The comprehensive evaluation value was between 0.3-0.6,which belongs to medium resistance;the weighted average value of membership function of Medicago sativa was only 0.167,which was weak in drought resistance.It showed that Broussonetia papyrifera,Trifolium repens and Morus alba had strong comprehensive drought resistance ability.Therefore,planting Broussonetia papyrifera,Trifolium repens and Morus alba in arid areas can better adapt to the environment of drought and water shortage,promote vegetation restoration and reduce the loss of yield reduction due to drought.Therefore,Broussonetia papyrifera,Trifolium repens and Morus albawith high drought resistance can be popularized and planted on a large scale in arid and water deficient areas.(3)The results of field verification of drought resistance of grass irrigation: by comparing the survival rate and plant height of plants between the dry shed and the control group,the survival rate of plants under the dry shed was obtained:Broussonetia papyrifera>Morus alba >Trifolium repens> Lolium perenne>Miscanthus sinensis>Medicago sativa.From the range of plant height decrease between the dry shed and the control group,Medicago sativa > Miscanthus sinensis > Lolium perenne > Morus alba> Broussonetia papyrifera > Trifolium repens,On the whole,the results of field drought test are basically consistent withthe comprehensive evaluation results of each index.The order of drought resistance was: Broussonetia papyrifera > Trifolium repens > Morus alba > Lolium perenne > Miscanthus sinensis > Medicago sativa.The results of field test were verified by indoor simulation experiment.(4)The change rule of nutritional value of six plant species under drought and control: through principal component analysis,the total nutritional index of six species in the control group was higher than that in the drought group,and the nutritional value ranks the top six:Broussonetia papyrifera in the control group > Trifolium repens in the control group > Morus alba in the control group > Broussonetia papyrifera in the drought group > Trifolium repensr in the drought group > Morus alba in the drought group.In general,the nutritional value of the plants in the control group was higher than that in the drought group,which indicated that the plants suffer from drought stress will lead to the reduction of nutritional quality.According to the comprehensive analysis of multiple indicators,the nutritional value was:Broussonetia papyrifera > Trifolium repens > Morus alba >Medicago sativa >Lolium perenne>Miscanthus sinensis,Trifolium repens and Morus alba can be widely planted in Salaxi Research Area in the mountainous area of Karst Plateau.Trifolium repens and Morus alba have high crude protein and high nutritional value.Planting Broussonetia papyrifera and Medicago sativa with higher nutritional value in the Huajiang Research Area canincrease income and promote the development of animal husbandry.In Shibing Research Area,the nutritional value of Lolium perenne and Miscanthus sinensis was relatively low,which can be improved by a series of measures.(5)Interaction between adaptability and quality of grass and shrub under drought stress in Rocky Desertification Area:Plants in Karst area adapt to drought stress through changes in morphological structure and physiological and biochemical structure.Through multiple stepwise regression analysis,the influence of environmental factors on photosynthetic physiological parameters of plants was discussed.It was found that atmospheric CO2 concentration(Ca)was the main environmental factor affecting Tr and Pn.Tr had a significant positive correlation with Pn and Gs,Gs had a significant positive correlation with Pn,vapor pressure difference in leaf gas saturation(Vpd)and Ca were the main environmental factors affecting Gs.RDA showed that soil bulk density(SBD)and total soil porosity(TSP)had significant effect on plant quality,SBD had significant effect on dry matter(DM),acid detergent fiber(ADF)and neutral detergent fiber(NDF),TSP had significant effect on calcium(Ca),relative feeding value(RFV),relative forage quality(RFQ)and non-fibrous carbohydrates(NFC),available phosphorus(AP),soil organic matter(SOM)and total potassium(TK)had significant effect on forage quality,available potassium(AK)had significant effect on DM,ADF and NDF,total phosphorus(TP)had significant effect on NFC,TK.It had significant effect on lignin,magnesium(Mg)and potassium(K),AP and SOM have significant effect on ether extract(EE).According to the comparison of physical and chemical properties of soil in arid environment and the control group,the single and interactive effects of physical and chemical properties of soil on the nutritional value of plants were compared.The effects of chemical properties of soil on the nutritional quality of plants were greater than that of physical properties of soil.(6)Key technology and demonstration of grass and shrub planting and quality improvement in Rocky Desertification Area: according to the particularity of karst rocky desertification area,based on the existing technology of rocky desertification,the paper puts forward the planting technology and quality improvement technology of grass and shrub plants suitable for the area,Trifolium repens and Morus alba were planted in the demonstration area of Salaxi in Bijie,a potential light rocky desertification area in the mountainous area of the Karst Plateau,Medicago sativa and Broussonetia papyriferawere planted in the Huajiang demonstration area of Zhenfeng,Guanling,and Lolium perenne and Miscanthus sinensis were planted in the Shibing demonstration area.According to the socio-economic status of the three demonstration areas of Bijie Salaxi,Guanling-Zhenfeng Huajiang and Shibing,grass irrigationplanting technology and quality improvement technology are applied in the three demonstration areas to increase the scientific cultivation of grass irrigation plants and improve nutrition value,increase people's income,improve local living standards,and can also improve the ecological environment,reduce soil erosion,and bring good ecological,economic and social benefits. |
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