渭北旱塬苹果园土壤呼吸温度敏感性的变化特征

发布时间：2018-10-11 08:19

【摘要】：土壤呼吸是调控陆地生态系统土壤碳循环的重要生态过程,温度敏感性(Q10)在很大程度上决定着全球的气候变化与陆地碳循环之间的反馈关系。了解Q10的变化及其影响因素有助于正确估算气候变化条件下陆地土壤碳源、汇能力的变化。黄土高原地形破碎,局域尺度上形成了典型的高原沟壑和丘陵沟壑等复杂的地形地貌。20世纪80年代以来,随着退耕还林、还草和还果措施的实施,逐渐形成了小流域农-林-果-草复合生态格局。农田和林草地生态系统的土壤呼吸及其温度敏感性已有大量研究,但对果园生态系统土壤呼吸及其Q10的了解较少。不同于农田和林草地生态系统,果园内,植被具有固定株行距,生产活动干扰强烈,了解果园土壤呼吸和Q10的时空变化有助于准确估算黄土高原区陆地生态系统碳循环。以高原沟壑典型治理小流域(王东沟小流域)为地点,利用土壤碳通量测量系统LI-8100(Li-COR,Lincoln,NE,USA)于2011~2013年监测了塬面、坡地两种地形条件下果园、农田和林草地生态系统土壤呼吸季节与年际间变化、土壤温度、水分以及细根生物量等。研究了1)果园土壤呼吸合理的采样方法;2)果树冠幅下距树干不同距离处土壤呼吸及Q10的空间变化;3)果园土壤呼吸及Q10与农田、林草地的差异;4)对比分析了塬面和坡地果园土壤呼吸及Q10的变化特征,探讨了地形对果园土壤呼吸及Q10的影响。主要结果如下:(1)果园土壤呼吸速率时空变异显著。时间尺度上,在叶幕形成期间及降水频繁时,宜设置的样点个数较多。但在郁闭情况下空间样点数差异不大。(2)在果园内,土壤呼吸速率及其Q10随着距树干距离延长而变化。2011~2013年,距树干0.5 m处(D0.5)平均土壤呼吸速率较距树干2 m处(D2)土壤呼吸速率分别高出21%,35%和42%;Q10分别高出15%,30%和12%。细根生物量同样随着距树干距离延长而降低,D0.5处细根生物量高出D2处细根生物量64%(2011),108%(2012)和114%(2013)。果树细根密度差异可能是本研究中影响果园土壤呼吸和Q10空间变化的重要生物因素。(3)2011~2013年,不同生态系统间土壤呼吸速率呈现相似的季节动态变化,且草地[3.67μmol(m2 s)-1]农田[2.33μmol(m2 s)-1]果园[1.99μmol(m2 s)-1]休闲地[0.86μmol(m2 s)-1]。不同生态系统间Q10存在显著差异:存在农田(2.80)草地(1.82)果园(1.60)休闲地(1.53)的趋势。(4)地形显著影响果园土壤呼吸及Q10。塬面果园的土壤呼吸速率高于坡地果园土壤呼吸速率,2011~2013年土壤呼吸速率均值较坡地提高了25%;而Q10相反,坡地(2.22)较塬面(1.96)高出了13%。此外,对农田和草地生态系统的对比发现,塬面农田和草地生态系统内土壤呼吸分别较坡地提高了33%和96%;草地Q10变化趋势与果园相似,坡地高于塬面(2.10 vs.1.82),农田则相反,塬面高于坡地(2.80 vs.2.31)。Q10与SOC含量呈显著正线性关系,相似SOC含量下,坡地Q10高于塬面。
[Abstract]:Soil respiration is an important ecological process to regulate the soil carbon cycle in terrestrial ecosystems. Temperature sensitivity (Q10) largely determines the feedback relationship between global climate change and terrestrial carbon cycle. Understanding the change of Q10 and its influencing factors is helpful to estimate the change of carbon source and sink capacity of terrestrial soil under climate change. The terrain of the Loess Plateau is broken, and the typical plateau gully and hilly gully are formed on the local scale. Since the 1980s, with the implementation of the measures of returning farmland to forest, returning grass to forest and returning fruit to fruit, and so on, Gradually formed a small watershed of agroforestry-fruit-grass complex ecological pattern. Much research has been done on soil respiration and temperature sensitivity of farmland and forestland ecosystem, but little is known about soil respiration and its Q10 in orchard ecosystem. Different from farmland and forestland ecosystem, vegetation in orchard has fixed row spacing and strong interference of production activities. Understanding soil respiration in orchard and space-time change of Q10 is helpful to accurately estimate carbon cycle of terrestrial ecosystem in Loess Plateau. Based on the typical watershed of plateau gully (Wangdonggou small watershed), the orchard was monitored from 2011 to 2013 under two topographical conditions, I. E. soil carbon flux measurement system (LI-8100 (Li-COR,Lincoln,NE,USA). Soil respiration season and interannual variation, soil temperature, moisture and fine root biomass in farmland and forestland ecosystem. This paper studies the sampling method of soil respiration in orchard, the spatial changes of soil respiration and Q10 at different distances from tree trunk under crown width of fruit trees, and the relationship between soil respiration and Q10 in orchard and farmland. (4) the characteristics of soil respiration and Q _ (10) in orchards on plateau and slope were analyzed, and the effects of topography on soil respiration and Q _ (10) in orchards were discussed. The main results were as follows: (1) the spatial and temporal variation of soil respiration rate in orchard was significant. On the time scale, the number of samples should be more when the leaf curtain is formed and the precipitation is frequent. However, there was little difference in the number of spatial samples in closed canopy. (2) in orchard, soil respiration rate and Q10 changed with the extension of tree trunk distance from 2011 to 2013. The average soil respiration rate at 0.5 m (D 0.5) was higher than that at 2 m (D 2) by 21 35% and 42% Q10, 15% and 12 0% higher than that at 2 m, respectively. The fine root biomass also decreased with the extension of the distance from the trunk. The fine root biomass at D 0.5 was 64% (2011), 108% (2012) and 114% (2013) higher than that at D2. The difference of fine root density of fruit trees may be an important biological factor influencing soil respiration and Q10 spatial variation in orchard in this study. (3) from 2011 to 2013, soil respiration rate of different ecosystems showed similar seasonal dynamic changes. Grassland [3.67 渭 mol (m 2 s) -1] farmland [2.33 渭 mol (m 2 s) -1] Orchard [1.99 渭 mol (m 2 s) -1] Casual Land [0.86 渭 mol (m 2 s) -1]. There were significant differences in Q10 among different ecosystems: there was a tendency of cropland (2.80) grassland (1.82) orchard (1.60) leisure land (1.53). (4) topography significantly affected soil respiration and Q10 of orchard. The soil respiration rate of orchards was higher than that of sloping orchards, and the average of soil respiration rate from 2011 to 2013 was 25% higher than that of sloping fields, whereas Q10 was 13% higher than that of sloping land (2.22). In addition, compared with grassland ecosystem, soil respiration in farmland and grassland ecosystem was increased by 33% and 96%, respectively, and the change trend of grassland Q10 was similar to that of orchard, the slope land was higher than the plateau (2.10 vs.1.82), but the farmland was opposite. The relationship between Q10 and SOC content was significantly positive, and Q10 was higher than that on the plateau under similar SOC content.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S154.1

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