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Northwest A&F University (2009)

Formation and Environmental Factors of Soil Algae Crust in the Loess Plateau


Titre : Formation and Environmental Factors of Soil Algae Crust in the Loess Plateau

Auteur : 吕建亮;

Grade : Master’s Theses 2009

Université : Northwest A&F University

The Loess Plateau Hilly and Gully Regions is one of the most serious soil erosion areas in the world. Soil algae which is grows in the Loess Highlands semi-arid region can not only endure the drought and barren conditions, but also can alter the environment. Presently, the research which is focus on the environment factors how to effect the algae’s formation and growth are few. Therefore, study on the effect of environmental factors in algae’s formation and growth have great meanings.This paper determinate the environment factors through the methods of the indoor rising and the open country investigation, to appraise the adaptive ability which algae mantle effect environmental. The indoor raising utilized the single factor experiment and the complete combination experiment, analyzed the constant element, the nutritional conditions, the moisture content, the temperature, the illumination, how to influence the growth of the soil-dwelling algae, and determined the soil algae’s optimism nutritional condition and the environmental condition. The purpose of research is for promulgating the environmental factor how to influence the algae mantle forming process, thus providing the scientific basis for soil loss control. The main conclusion was following:1. The different vegetation structures present the different regularity to the algae mantle’s degree of cover and thickness. When the vegetation structure was different, the algae mantle degree of cover was different. The soil aglae’s coverage under different vegetation structures ranked in order of barren slopes> Mongolian pine forest> Chinese pine forest. But the mantle thickness displaied the opposite characteristic, ranked in order of Chinese pine forest > Mongolian pine forest > barren slopes.2. The effect of different slopes on soil algae crust distribution were extremely obvious, the coverage and thickness of soil algae crust in the shady slope were bigger than that in the sunny slope ; The different slope was not remarkable to soil algae crust’s distribution. The degree of disturbance had extremely obvious effection to the algae mantle degree of cover, the degree of disturbance was weak, the algae mantle degree of cover was bigger, otherwise was small.3. Parts of different landforms crust of algae had a significant effect on the distribution, in the woodland, the crust cover the performance of the Department for the slope> slope central> lower slope. Crust thickness had no significant difference. In the slopes, the upper, middle and downhill algae crust cover and thickness difference.4. Under different moisture content, the 100% water supply’s algae degree of cover was the biggest, achieves 40.7%, next was the 80% water supply, 60% water supply, 40% water supply. 20% water supply under the serious moisture content owes lacks, the algae did not grow. Under different moisture content condition, the 60% water supply was bigger 70.2% than 40% water supply degree of cover, the 80% water supply was bigger 87.5% than 60% degree of cover, and the 100% water supply was bigger 33.3% than 80% water supply.5. The soil-dwelling algae growth most well in 25℃, at 15℃, the growth suppresses of the soil-dwelling algae was inhibited. Moreover, the soil-dwelling algae dies basically at 50℃. Look from the long growth tendency, soil-dwelling algae growth speed was very quick at 35℃, the 30d raising had achieved the growth peak, but at 15℃the growth was slow, but if the time was prolong, its biomass could increase. Under the different illumination condition under the 7000lx strength of illumination and the 18h/d illumination time, soil-dwelling algae growth very well.6. The nitrogen level influence the soil algae’s growth remarkably, when took the CO(NH2)2 as the nitrogen source, the degree of cover, the density and plant height was most high, respectively was 55%, 36 /cm2 and 4.2mm. Under the different density of raising condition, when the NaNO3 density strengthened, the nitrogen assimilation also strengthened, the growth rate increases strengthened gradually, increase the density of nitrogen source can promoted the soil-dwelling algae’s growth.7. Temperature, pH, nitrogen and phosphorus levels of three different combination of factors under the condition of orthogonal experiment, soil algae growth conditions at the time of maximum temperature 25℃, nitrogen and phosphorus than 16:1, the initial pH value was set to 8.2

Mots clés : the Loess Plateau; soil algae crusts; distribution laws; culture; environmental factors;

Présentation (CNKI)

Page publiée le 25 mars 2018