降水变化对鼎湖山季风常绿阔叶林土壤微生物群落的影响

发布时间：2018-09-07 19:04

【摘要】：随着全球气候的变化,全球降水格局发生了明显的变化。其中南亚热带区域降水强度和降水频率发生不同程度的改变,土壤湿度降低,这些变化影响森林土壤有机碳稳定性。土壤微生物群落能对土壤环境变化作出有效早期反映,因此本文以南亚热带季风常绿阔叶林赤红壤为对象,开展降水改变模拟实验,实验处理包括1)年降水总量不变下降水频率增加;2)年降水量减少50%;3)自然降水(对照组)。通过采集0~10cm和10~20cm土壤并结合磷脂脂肪酸方法(PLFA)和室内恒温培养实验,测定土壤微生物群落结构和有机碳矿化速率,进而分析降水处理下土壤微生物生物量、相对丰度和土壤有机碳矿化速率等的变化。土壤理化性质在降水处理下有不同的变化特征,土壤pH值存在季节差异性明显特征(P0.05),其它指标季节差异性不明显(P0.05)。在土壤层0~20cm中,土壤湿度、有机碳含量、氮总量、磷总量均随土壤加深呈减少趋势,但土壤酸性随着土壤深度增加呈减弱的趋势。在雨季和旱季,降水频率增加和年降水量减少50%处理均提高土壤有机碳含量。在降水频率增加和年降水量减少50%处理下,同一土壤层的土壤微生物生物总量、细菌生物量、真菌生物量、丛枝菌根真菌生物量与对照组之间差异不明显,而放线菌生物量在雨季差异不显著,在旱季差异显著(P0.05),具体表现为年降水量减少50%处理明显降低土层0~10cm的放线菌PLFAs量,这可能是因为在旱季,土壤有机碳含量与氮量抑制放线菌的生长。雨季时的土壤微生物PLFAs量与旱季差异不明显,同时在雨季年降水量减少50%处理可以促进土壤微生物的生长。土壤丛枝菌根真菌的相对丰度未受到降水处理的明显影响,而土壤细菌、革兰氏阳性菌、革兰氏阴性菌、真菌和放线菌均受到降水处理的不同程度的明显影响。降水处理的土壤真菌细菌比在雨季时差异不明显,在旱季时差异明显。土壤有机碳矿化速率先下降后上升再不稳定地下降,其累积速率趋向于线性上升。在森林土层0~20cm中,在降水频率增加处理样地,土壤有机碳矿化累积年均速率为1000.04±166.87mgCO_2·kg~(-1)·h~(-1),在年降水量减少50%处理样地,土壤有机碳矿化累积年均速率为967.26±97.60mg CO_2·kg~(-1)·h~(-1),对照组的土壤有机碳矿化累积年均速率为948.18±108.47mgCO_2·kg~(-1)·h~(-1),这表明降水频率增加处理可以提高土壤碳排放的速率。
[Abstract]:With the change of global climate, the global precipitation pattern has changed obviously. The intensity and frequency of precipitation in the subtropical region changed to some extent, and the soil moisture decreased, which affected the stability of forest soil organic carbon. Soil microbial communities can effectively reflect the changes of soil environment at an early stage. Therefore, in this paper, a simulated experiment of precipitation change was carried out on the subtropical monsoon evergreen broad-leaved lateritic red soil. The experimental treatment includes: 1) increasing the frequency of annual precipitation, increasing the frequency of decreasing water, 2) decreasing annual precipitation by 50% and 3) natural precipitation (control group). Soil microbial community structure and organic carbon mineralization rate were measured by collecting 0~10cm and 10~20cm soil, combining with phospholipid fatty acid (PLFA) method and indoor constant temperature culture experiment, and then soil microbial biomass was analyzed under precipitation treatment. Changes of relative abundance and mineralization rate of soil organic carbon. Soil physical and chemical properties have different characteristics under precipitation treatment, soil pH value has obvious seasonal differences (P0.05), other indicators have no significant seasonal differences (P0.05). In soil layer 0~20cm, soil moisture, organic carbon content, total nitrogen and phosphorus content decreased with the deepening of soil, but the acidity of soil decreased with the increase of soil depth. In the rainy season and dry season, the increase of precipitation frequency and the reduction of annual precipitation by 50% increased soil organic carbon content. When the precipitation frequency increased and the annual precipitation decreased by 50%, there was no significant difference between the soil microbial biomass, bacterial biomass, fungal biomass, arbuscular mycorrhizal fungi biomass of the same soil layer and the control group. But the biomass of actinomycetes had no significant difference in rainy season, but significant difference in dry season (P0.05), which showed that the amount of actinomycete PLFAs in soil layer was significantly decreased by 50% annual precipitation reduction, which may be due to the dry season. Soil organic carbon and nitrogen content inhibited the growth of actinomycetes. The amount of PLFAs of soil microorganism in rainy season was not significantly different from that in dry season, and the treatment of 50% decrease of annual precipitation in rainy season could promote the growth of soil microorganism. The relative abundance of soil arbuscular mycorrhizal fungi was not significantly affected by precipitation treatment, while soil bacteria, Gram-positive bacteria, Gram-negative bacteria, fungi and actinomycetes were significantly affected by precipitation treatment. There was no significant difference between soil fungi and bacteria in precipitation treatment during rainy season, but significant difference in dry season. The mineralization rate of soil organic carbon decreased firstly then increased and then unsteadily decreased. The accumulation rate of soil organic carbon tended to increase linearly. In 0~20cm of forest soil layer, the average annual rate of soil organic carbon mineralization was 1000.04 卤166.87mgCO_2 kg~ (-1) h ~ (-1) in the sample plots with increasing precipitation frequency, and the annual precipitation was reduced by 50% in the treatment plots, the average annual rate of soil organic carbon mineralization was 1000.04 卤166.87mgCO_2 kg~ (-1) h ~ (-1). The average annual rate of soil organic carbon mineralization accumulation was 967.26 卤97.60mg CO_2 kg~ (-1) h-1, and that of the control group was 948.18 卤108.47mgCO_2 kg~ (-1) h-1, which indicated that the increase of precipitation frequency could increase the rate of soil carbon emission.
【学位授予单位】：广州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S714.3

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