【作者】 谢慧慧；

【导师】 郝明德； 樊军；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2010， 硕士

【摘要】 水蚀风蚀交错区是黄土高原水土流失最严重的区域。实行退耕还林(草)以来,该区的土地利用方式发生了一定变化。在植被类型转变过程中,土壤呼吸的季节变化特征、影响机制等急需进一步研究明确。因此,本研究选取几种典型植被,研究土壤呼吸的季节变化特点及环境因子和土壤养分对土壤呼吸的影响。同时探讨了不同覆盖措施对人工草地水分利用的影响。本研究主要结论如下:(1)土壤呼吸表现出明显的季节变化。温度和土壤呼吸之间关系密切,指数模型能够较好地揭示各样地土壤呼吸对温度变化的响应,但低温时模型的拟合效果更好。各群落土壤呼吸的季节动态与温度变化不完全同步,表明温度并不是影响土壤呼吸的唯一因子。土壤呼吸的温度敏感性在各土地利用方式之间存在着一定的差异。(2)水分对各群落的土壤呼吸也有较大影响,但其影响程度有一定的季节差异。土壤呼吸和土壤水分季节动态的总趋势相近,其最大值都是出现在7~9月份。采用线性模型对土壤呼吸与水分的关系进行回归分析可知,不同土地利用类型间土壤呼吸与水分的关系不尽一致。消除温度的影响后,土壤呼吸与水分之间的线性关系显著增强。(3)采用4种模型对土壤呼吸与土壤温度和水分的复合关系进行分析,结果表明,幂指混合型函数RS = a·e bTs·WS c能够更好地模拟土壤呼吸与土壤温度和水分的关系,二者共同解释了土壤呼吸季节变化的59%~83%。(4)土壤呼吸与土壤有机碳含量存在显著正相关关系,与速效K含量呈极显著正相关关系,与全N也有一定的正相关关系,但未达显著水平。土壤的铵态氮含量除雨季之外和土壤呼吸之间有显著甚至极显著的负相关关系。土壤碳酸钙含量与土壤呼吸的关系未达到显著水平,但在雨季有较高的负相关关系,而磷素和硝态氮含量对土壤呼吸没有显著影响。容重对土壤呼吸也没有显著影响。(5)对4种土地利用方式下土壤呼吸与植被生物量进行线性回归分析可知,土壤呼吸与植被地上生物量呈负相关关系,与地下生物量和总生物量呈正相关关系,但均未达显著水平。综合研究结果,在本研究区域内,土壤呼吸速率的季节变化与植被生物量之间没有相关关系。对4种土地利用方式进行碳平衡估算可知,净生态系统生产力仅有长芒草地为负值,表现为碳源,其余均为正值,表现为碳汇。(6)覆盖试验可知,无覆盖处理土壤浅层温度比碳酸钙结核覆盖和玉米秸秆覆盖高。方差分析结果表明,无覆盖处理和秸秆覆盖处理间有极显著的差异(P<0.01),而无覆盖处理与结核覆盖、结核覆盖与秸秆覆盖处理间差异不显著(P>0.05)。玉米秸秆覆盖下的土壤表层含水量较无覆盖和碳酸钙结核覆盖下的都高,但3种覆盖方式间差异均不显著(P>0.05)。3个处理下苜蓿的干草产量、总耗水量及水分利用效率均存在一定差异,虽然没有达到统计显著水平(P>0.05),但覆盖在一定程度上提高了苜蓿的产量和水分利用效率。更多还原

【Abstract】 Water-wind erosion crisscross area is located in the north of the Loess Plateau, which is one of the most serious soil erosion areas in the Loess Plateau. Since Grain to Green project has conducted many years, the land use patterns in this region have changed in some extent. Seasonal characteristics and affecting mechanism of soil respiration need to be cleared in the changing of the vegetation type. For that reason, this research had chosen some typical land use patterns to study seasonal characteristics of soil respiration, as well as the influence of environmental factors and soil nutrients on soil respiration. Besides, the study explored the influence of different mulching measures on water use condition of artificial grassland. The main results obtained from this study are as follows:Seasonal variation in soil respiration was observed in the study area. Significant relationships had been found between soil respiration rate and soil temperature for the different land use patterns, which could be best described by exponential equations. The influence of temperature was more significant at lower temperature than at higher temperature. Accordingly, the seasonal variations of soil respiration were not in complete accordance with variation of temperature, it means that the temperature is not the only factors that influence soil respiration. Differences in the temperature sensitivity of soil respiration existed between different land use patterns.Soil moisture had great influence on soil respiration, but the degree varied during the growing season. The general trend of soil respiration and soil moisture was similar. The higher value of soil respiration appeared from July to September. Adopting the linear model, after the regression analysis between soil respiration and soil moisture, we know that the relationship between them was incompletely same. After deleting the confounded effect of temperature, the linear relationships were more significant than above in all land use patterns.Composite relationships between soil respiration and soil temperature and soil moisture were analyzed with four models. The results indicated that the mixed function could simulate their relationships best. Soil temperature and soil moisture could explain 59%~83% variation of soil respiration. Soil respiration and soil bulk density had no significant associative relationship, but had significant relationship with soil organic carbon content, also had extremely significant relationship with soil available K content. Soil respiration and total N also had positive correlation, but not significant. In addition to the rainy season, soil ammonium nitrogen content and soil respiration had significant or extremely significant negative correlation. The relationship between soil calcium carbonate content and soil respirations did not reach significant level, but in the rainy season there was a high negative correlation. But P and nitrate nitrogen content no significant effect on soil respiration.Analyzed the linear relationship between soil respiration and vegetation biomass, soil respiration and vegetation above ground biomass was not correlation. Correlation between soil respiration and vegetation underground biomass was not significant, total biomass also. To sum up, there were not significabt correlation between soil respiration and vegetation biomass. Among four land use patterns, only Stipa bungeana NEP was the negative value, which showed carbon source. Others were opposite with Stipa bungeana.From the mulching trial, soil surface temperature of the contrast was higher than mulching. Variance analysis showed than there was an extremely significant difference between the contrast and straw mulching. Difference between the contrast and tuberculoid calcium carbonate mulching was not significant, so did straw mulching and tuberculoid calcium carbonate mulching.Soil surface moisture of straw mulching was higher than the contrast and tuberculoid calcium carbonate mulching, but three treatments had no difference. Alfalfa biomass and total water consumption and water use efficiency had same difference. Although did not reach the significant difference, Straw mulching and tuberculoid calcium carbonate mulching could improve alfalfa yield and water use efficiency according the observed results.更多还原