【摘要】：隨著全球氣候的變化,全球降水格局發(fā)生了明顯的變化。其中南亞熱帶區(qū)域降水強度和降水頻率發(fā)生不同程度的改變,土壤濕度降低,這些變化影響森林土壤有機碳穩(wěn)定性。土壤微生物群落能對土壤環(huán)境變化作出有效早期反映,因此本文以南亞熱帶季風(fēng)常綠闊葉林赤紅壤為對象,開展降水改變模擬實驗,實驗處理包括1)年降水總量不變下降水頻率增加;2)年降水量減少50%;3)自然降水(對照組)。通過采集0~10cm和10~20cm土壤并結(jié)合磷脂脂肪酸方法(PLFA)和室內(nèi)恒溫培養(yǎng)實驗,測定土壤微生物群落結(jié)構(gòu)和有機碳礦化速率,進(jìn)而分析降水處理下土壤微生物生物量、相對豐度和土壤有機碳礦化速率等的變化。土壤理化性質(zhì)在降水處理下有不同的變化特征,土壤pH值存在季節(jié)差異性明顯特征(P0.05),其它指標(biāo)季節(jié)差異性不明顯(P0.05)。在土壤層0~20cm中,土壤濕度、有機碳含量、氮總量、磷總量均隨土壤加深呈減少趨勢,但土壤酸性隨著土壤深度增加呈減弱的趨勢。在雨季和旱季,降水頻率增加和年降水量減少50%處理均提高土壤有機碳含量。在降水頻率增加和年降水量減少50%處理下,同一土壤層的土壤微生物生物總量、細(xì)菌生物量、真菌生物量、叢枝菌根真菌生物量與對照組之間差異不明顯,而放線菌生物量在雨季差異不顯著,在旱季差異顯著(P0.05),具體表現(xiàn)為年降水量減少50%處理明顯降低土層0~10cm的放線菌PLFAs量,這可能是因為在旱季,土壤有機碳含量與氮量抑制放線菌的生長。雨季時的土壤微生物PLFAs量與旱季差異不明顯,同時在雨季年降水量減少50%處理可以促進(jìn)土壤微生物的生長。土壤叢枝菌根真菌的相對豐度未受到降水處理的明顯影響,而土壤細(xì)菌、革蘭氏陽性菌、革蘭氏陰性菌、真菌和放線菌均受到降水處理的不同程度的明顯影響。降水處理的土壤真菌細(xì)菌比在雨季時差異不明顯,在旱季時差異明顯。土壤有機碳礦化速率先下降后上升再不穩(wěn)定地下降,其累積速率趨向于線性上升。在森林土層0~20cm中,在降水頻率增加處理樣地,土壤有機碳礦化累積年均速率為1000.04±166.87mgCO_2·kg~(-1)·h~(-1),在年降水量減少50%處理樣地,土壤有機碳礦化累積年均速率為967.26±97.60mg CO_2·kg~(-1)·h~(-1),對照組的土壤有機碳礦化累積年均速率為948.18±108.47mgCO_2·kg~(-1)·h~(-1),這表明降水頻率增加處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 鹵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 鹵166.87mgCO_2 kg~ (-1) h ~ (-1). The average annual rate of soil organic carbon mineralization accumulation was 967.26 鹵97.60mg CO_2 kg~ (-1) h-1, and that of the control group was 948.18 鹵108.47mgCO_2 kg~ (-1) h-1, which indicated that the increase of precipitation frequency could increase the rate of soil carbon emission.
【學(xué)位授予單位】：廣州大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S714.3

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