| Karst area of southwest China is the international recognized ecology fragile district about 540000 km2.Karst topography strongly development, underground river buried deeply, add to the impact of human factors, soil erosion and rocky desertification is seriously, karst area is one of the most serious ecological debt area in China and is also a national key poverty area, become the difficulty of building a well-off society. Around the comprehensive treatment of desertification of country strategic needs and the national goal response to global climate change, global climate resulting in frequently extreme weather of region, so forest-grass species selection and cultivation technology must be adjusted, and establish new technical system answer to extreme low temperature problems of karst area. Used artificial climate box to deal with 5 forest-grass species(Festuca elat; Cichorium intybus; Rosa roxbunghii; Zanthoxylum bungeanum; Broussonetia papyrifera) under different temperature gradient(4℃,6℃and 8℃), the processing time was 0h, 24 h, 48 h and 72 h, contrasted the variation characteristics of physiological indexes(leaf water content, proline content, relative conductivity, chlorophyll content, photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency) of them, selected strong cold resistance species in November and December of 2014. Monitored the vegetation features and soil physical-chemical properties and microclimate of three demonstration plots(Karst plateau mountain demonstration, Karst plateau basin demonstration and Karst plateau gorge demonstration) every 4 months, evaluated different technical measures on cold resistance. Built optimal allocation model of community according to plant ecological-physiological characteristics, demonstration and popularization had been carried out. Technical system, theoretical support and demonstration modal had been provided for large-scale treatment of karst rocky desertification in Guizhou as the center of southwest 8 provinces(area, city). The main conclusions are as follows:(1) Leaf water content was decreased under different temperature treatment(4℃,6℃ and 8℃) compared with CK; Leaf water content of Festuca elata and Rosa roxbunghii was decreased under 8℃ with the extension of stress time, leaf water content of Cichorium intybus rose after the first drop; Leaf water content of Festuca elata and Rosa roxbunghii consecutive decline with the extension of stress time under 6℃ and 8℃, there was no significant change of Cichorium intybus; On the whole, leaf water content of Festuca elata and Rosa roxbunghii were decreased significantly(p<0.05) compared with CK after 24 h, 48 h and 72 h treatment, there was no significant change of Cichorium intybus. Leaf water content of Zanthoxylum bungeanum was decreased significantly compared with CK after 48 h and 72 h treatment; Leaf water content of Broussonetia papyrifera was decreased significantly compared with CK after 24 h, 48 h and 72 h treatment. On the whole, leaf water content decline extent of Zanthoxylum bungeanum and Broussonetia papyrifera were comparatively.The chlorophyll content of Festuca elata, Cichorium intybus and Rosa roxbunghii rose after the first drop under 8℃ and 6℃. The chlorophyll content of Festuca elata, Cichorium intybus and Rosa roxbunghii consecutive decline with the extension of stress time under 4℃, and the decline extent: Rosa roxbunghii>Cichorium intybus>Festuca elata, cold resistance conversely. Chlorophyll content of Broussonetia papyrifera was decreased significantly compared with CK after 48 h and 72 h treatment(p<0.05), and there was no significant change of Zanthoxylum bungeanum.(2) The photosynthetic rate of Festuca elata, Cichorium intybus and Rosa roxbunghii was decreased under 8℃ treatment with the extension of stress time(p<0.05), and the decline extent: Festuca elata>Cichorium intybus>Rosa roxbunghii; The photosynthetic rate of Festuca elata, Cichorium intybus and Rosa roxbunghii was decreased under 6℃ and 4℃ treatment with the extension of stress time(p<0.05), and the decline extent: Rosa roxbunghii>Cichorium intybus>Festuca elata; The photosynthetic rate of Zanthoxylum bungeanum and Broussonetia papyrifera were decreased and the decline extent: Broussonetia papyrifera > Zanthoxylum bungeanum, showed that Zanthoxylum bungeanum had better cold resistance under 4℃ and 6℃. Seeding stomatal conductance of Rosa roxbunghii was decreased remarkably compared with CK after 0h, 24 h, 48 h and 72 h treatment(p<0.05), there were no significant change of Festuca elata and Cichorium intybus. Stomatal conductance of Zanthoxylum bungeanum and Broussonetia papyrifera were decreased with the extension of stress time, and the decline extent roughly the same, showed that Zanthoxylum bungeanum and Broussonetia papyrifera were greatly inhibited under 4-8℃ low temperature range. Transpiration rate of Festuca elata, Cichorium intybus and Rosa roxbunghii were decreased remarkably compared with CK under 4℃, 6℃and 8℃ low temperature treatment(p<0.05), the transpiration rate of 3 species seedlings showed a continuous downward trend with the extension of stress time, and the decline extent: Rosa roxbunghii>Cichorium intybus>Festuca elata; Showed that Rosa roxbunghii and Cichorium intybus cold resistance better than Rosa roxbunghii. Transpiration rate of Zanthoxylum bungeanum and Broussonetia papyrifera were decreased remarkably compared with CK under 4℃,6℃and 8℃ low temperature treatment, and the decline extent: Broussonetia papyrifera > Zanthoxylum bungeanum, showed that cold resistance of Zanthoxylum bungeanum seeding was better than Broussonetia papyrifera.(3) Under the low temperature stress of 8 ℃, water utilization of Festuca elata, Cichorium intybus and Rosa roxbunghii seedling leaves with the extension of stress time showed a trend of first decreased and then increased, but the change was not evident. Under the low temperature stress of 6 ℃ and 4 ℃, with the extension of stress time, Festuca elata and Cichorium intybus seedling leaves’ water utilization kept a trend of first decreased and then increased, while Rosa roxbunghii showed a continuous downward trend and closed to 0 after 72 hours, which showed that the cold resistance of Festuca elata and Cichorium intybus were better than that of Rosa roxbunghii. Under different low temperatures(4 ℃, 6 ℃, 8 ℃), with the extension of stress time, the water utilization of Zanthoxylum bungeanum seedling leaves showed a changing characteristics of first decreased and then increased, and its water utilization was apparently higher than that of CK(P < 0.05) after 72 hours, while Broussonetia papyrifera showed a non-significant change which made its overall performance was not as well as Zanthoxylum bungeanum. Under different low temperatures(4 ℃, 6 ℃, 8 ℃), proline content of Festuca elata, Cichorium intybus and Rosa roxbunghii seedling leaves with the extension of stress time showed a continuous upward trend, and increased significantly after 72 hours compared with the CK(P < 0.05). On the whole, the proline accumulation in Festuca elata and Cichorium intybus were higher than that of Rosa roxbunghii, which showed that Festuca elata and Cichorium intybus have better adaptability to low temperature. As the stress temperature decreased and the stress time increased, relative conductivity of each species’ seedlings leaves showed an increasing trend. The conductivity of Festuca elata showed an unremarkable increase compared with the CK under different stress time(P > 0.05), however, Rosa roxbunghii and Cichorium intybus had a higher relative conductivity than that of the Contrast after 72 hours(P < 0.05), and Rosa roxbunghii had a bigger increase. With the decreasing temperature and the increasing of stress time, the relative conductivity of Zanthoxylum bungeanum and Broussonetia papyrifera seedlings leaves increased significantly.(4) The community diversity index and biomass of shrub will be the highest wherever be fertilized in Karst plateau mountain rocky desertification area, and the overwinter survival rate of community will be the biggest wherever be covered with grass. The soil nutrient elements(nitrogen, phosphorus, potassium) will be increased to maximum through fertilization treatment, and total porosity of soil will get the most significant increase by compact planting. The community microclimate had no significant difference by different treatment methods. The highest community diversity index of Karst plateau gorge rocky desertification area where was fertilized, showed that the fertilization treatment will significantly increase the amount of information and the complex degree of the community. The compact planting community possessed of the highest evenness index. It is thus clear that fertilization and compact planting treatment had the largest influence on the diversity of species in the community. Fertilization can significantly improve the total nitrogen content in soil(P < 0.05), and the four treatments significantly increased the content of total potassium in soil. The community microclimate had no significant difference by different treatment methods. The most useful method to increase the plant quantity index in Karst Plateau Basin desertification area was to promote the role of compact planting and water retaining agent + grass-cover treatment(P < 0.05). The average crown width and chlorophyll content of community were significantly increased under fertilization treatment, which showed fertilization had a great promotion to plant extension and supplement of mineral elements required by chlorophyll synthesis. While the most useful method to the growth of coniferous forest were water retaining agent + grass-cover treatment and water retaining agent treatment. |
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