华北低山丘陵区刺槐林土壤甲烷通量变化特征及其影响机制

发布时间：2017-12-31 10:30

本文关键词：华北低山丘陵区刺槐林土壤甲烷通量变化特征及其影响机制　出处：《中国林业科学研究院》2016年博士论文　论文类型：学位论文

【摘要】：研究我国森林土壤甲烷通量的变化特征、源汇转换过程及其影响机制,对定量评价森林土壤甲烷累积通量及其增温潜势具有重要的科学意义,还可为指导林业应对气候变化行动提供理论依据。本文于2014年—2015年期间,以河南省济源市黄河小浪底森林生态系统定位研究站区内47年生刺槐人工林为研究对象,在确定箱式—激光法测算土壤甲烷通量的合适密闭时间以及代表性时段的基础上,采用该方法,观测分析脉冲降水对土壤甲烷通量的影响,捕捉其源汇转换过程;并基于时空尺度,研究揭示在不同时期土壤甲烷通量的变化特征及其影响森林土壤甲烷通量的主控因子;运用温室气体的增温潜势原理,探讨该区土壤甲烷累积通量及其相对温室潜势。以期深入揭示华北低山丘陵区刺槐人工林土壤甲烷的变化特征及其影响机制。主要结果如下:(1)分析箱式—激光法的密闭时间对土壤甲烷通量影响作用,结果表明,采用该体积大小的箱式-激光法时,在0—30 min的密闭时间范围内,气室内的温度、气压的和水汽浓度波动明显,均在密闭5 min时达到最大;根据线性方程的计算方法可知,R2最大值出现在10 min(R2=0.85),而且在5—10 min时土壤甲烷通量波动较小,由此可知,采用该体积大小时,密闭时间应控制在10 min以内。通过分析测定土壤甲烷通量的代表性时段,结果表明,研究区在生长季(2015年5月—2015年10月)和非生长季(2014年11月—2015年4月)分别选取8:00—9:00和9:00—10:00作为其代表性时段;并对各月代表性时段土壤甲烷通量的平均值与日平均值进行拟合,结果表明,各月代表性时段土壤甲烷通量平均值与24 h日平均值数据差异最小出现在9月,最大出现在7月;对各月代表性时段土壤甲烷通量的平均值与日平均值进在年尺度上的有效性进行检验评估,结果表明,本研究选取的代表性时段可代表研究区的全年土壤甲烷通量(R2=0.89,P0.001)。(2)通过对刺槐人工林土壤甲烷通量的变化特征及其影响因素进行分析,结果表明,大气温度呈单峰型表现趋势,最高温度出现在8月,最低湿度出现在1月底—2月初。林内降水截留作用明显,使林内降水量低于林外。林内相对湿度明显高于林外,而光合辐射则与相对湿度相反。0—10 cm土层的土壤容重和最大持水量均与10—20 cm和20—30cm存在显著性差异(p0.05,p0.05);有机质在不同季节间的土层间差异性显著,而ph值除冬季外,其余季节的各土层间的差异性不显著(p0.05);在春、夏季节,随着土壤深度的增加,土壤温度总体呈现出下降的趋势,而在秋、冬季节,随土壤深度的增加,土壤温度总体表现为上升的变化趋势;土壤含水量在旱季深层高于浅层,而雨季则与旱季相反;各土层土壤甲烷氧化菌pmoa基因在春季、夏季和秋季,它们之间差异性不显著(p0.05),而在冬季各土层间差异性显著(p0.05)。本研究中刺槐人工林土壤表现为较强的甲烷吸收汇,呈现出昼高夜低的日变化特征,在中午12:00—13:00时刻出现最低值(除12—1月外);土壤甲烷通量的季节变化呈单峰型,最高值出现在7月,最低值出现在4月。本研究中土壤甲烷通量与影响因子的相关性分析表明,0—10cm深处的土壤温度、大气温度和相对湿度与土壤甲烷通量呈极显著正相关;主成分分析表明,土壤温度和大气温度为第一主成分,0—10cm深处土壤含水量为第二主成分,土壤有机质和土壤ph值为第三主成分,nh4+-n含量为第四主成分,四个主成分方差贡献率分别为41.61%、22.16%、16.88%和13.45%,其累积贡献率高达94.11%。由此可知,土壤温度和含水量的交互作用是影响土壤甲烷通量的重要影响因素。(3)分析脉冲降水对土壤甲烷通量的影响作用,结果表明,脉冲降水的产生明显降低了刺槐林地土壤氧化大气甲烷的能力;在降水前期、影响期、滞后期、恢复前期和恢复后期这5个阶段中,各气象要素之间均呈显著性差异。在2014年10月降水量较小时,0—10cm深处土壤含水量波动小,空气温度、相对湿度和太阳辐射等因素易受雨水影响,而且由于大气温度和太阳辐射等因素的影响,使其在生长季末期的变化幅度小,使相对湿度成为影响土壤甲烷通量的主要因素。在2015年4月,由于较高的降水量,土壤水分入渗通常会出现在大雨之后一段时间内,并可能持续数小时或数天,并且由于生长季初期大气温度开始恢复,使相对湿度以及太阳辐射恢复较快,从而使太阳辐射是影响土壤甲烷通量的主要因素。(4)通过计算研究区土壤甲烷通量的季节累积通量和相对温室潜势,结果表明,本研究中春、夏、秋、冬四个季节的土壤甲烷累积通量分别为-0.87kg·hm-2、-0.79kg·hm-2、-0.95kg·hm-2和-0.77kg·hm-2,占全年的比例分别为23.61%、21.53%、25.86%和20.83%。春、夏、秋、冬四个季节的土壤甲烷增温潜势分别为-21.75kg·co2·hm-2、-19.75 kg·CO2·hm-2、-23.75 kg·CO2·hm-2和-19.25 kg·CO2·hm-2。通过累积计算研究区的年累积通量及相对温室潜势,结果表明,该区土壤甲烷年累积通量为-3.38 kg·hm-2·a-1,相对温室潜势为-84.5 kg·CO2·hm-2。
[Abstract]:Study on the variation characteristics of China's forest soil CH4 fluxes, source conversion process and the influence mechanism of quantitative evaluation on forest soil accumulative methane flux and its warming potential has important scientific significance, but also provide a theoretical basis for guiding forestry action to tackle climate change. This paper in 2014 to 2015, to study the forest ecological station location the Yellow River Xiaolangdi Dam in Jiyuan city in Henan province in 47 years of Robinia pseudoacacia plantation as the research object, in determining the type of laser method to measure soil CH4 fluxes in the appropriate time and closed representative periods on the basis of using the method, observation and analysis of pulse effect of precipitation on Soil CH4 fluxes, the capture source conversion process; and based on time and space the research revealed that in the scale factor change characteristic and its influence of main control forest soil CH4 fluxes in different periods of soil CH4 fluxes; use of greenhouse gases The warming potential principle, to explore the soil accumulative methane flux and relative greenhouse potential. In order to reveal the variation characteristics and influence mechanism of the North hilly area of Robinia pseudoacacia plantation soil methane. The main results are as follows: (1) analysis of box - laser method closed time on soil methane flux effect results show that the size of the box by laser method, in the closing time in the range of 0 - 30 min, the indoor air temperature, air pressure and water vapor concentration fluctuates obviously and reached the maximum in the closed 5 min; according to the linear equation calculation method, the maximum value of R2 appeared at 10 min (R2=0.85), and in 5 - 10 min soil methane flux fluctuation is small, therefore, the volume size, closed time should be controlled within 10 min. The representative soil CH4 fluxes through the analysis of the time, the results show that the study area in students Long season (May 2015 - October 2015) and non growth season (November 2014 - April 2015) were selected for 8:00 - 9:00 and 9:00 - 10:00 as the representative of the month period; and representative periods, soil CH4 fluxes and average daily average fitting results show that each month in representative periods, soil CH4 fluxes average with 24 h average data difference minimum appeared in September, the maximum appeared in July; the average value of each month at representative soil CH4 fluxes and average test evaluation, the effectiveness in the annual scale, the results show that the annual soil CH4 fluxes representative were selected in this study period can represent the study area the (R2=0.89, P0.001). (2) analysis, the variation characteristics and its influencing factors on soil CH4 fluxes of Robinia pseudoacacia plantation. The results showed that air temperature showed a single peak trend, the highest temperature in August , the lowest humidity appeared at the end of January - early February. The rainfall interception, forest precipitation was lower than that outside the forest. The relative humidity was higher than that outside the forest, and photosynthetic radiation and relative humidity in.0 - 10 cm soil bulk density and soil water holding capacity and 10 - 20 cm and 20 30cm there was a significant difference (P0.05, P0.05); organic matter in different seasons between the layers of a significant difference, but the pH value in winter, the difference between each layer of the rest of the season was not significant (P0.05); in the spring, the summer season, with the increase of soil depth, soil temperature showed an overall decline the trend, and in autumn, winter, with the increase of soil depth, soil temperature generally showed a trend of increase; soil moisture is higher than that of the shallow and deep in the dry season, rainy season and dry season is the opposite; the soil methane oxidizing bacteria pmoA gene in spring, summer and autumn, they Not significant difference between them (P0.05), and in winter the soil have significant difference (P0.05). The soil of Robinia pseudoacacia plantation showed strong methane sink in this study, showing the diurnal variation of daytime high and night low, the lowest value appeared at 12:00 13:00 time (except 12 January outside) seasonal variation; soil CH4 fluxes showed a single peak, the highest value in July, the lowest value appeared in April. Correlation analysis between soil CH4 fluxes and influencing factors in this study showed that the soil temperature of 0 - 10cm depth, air temperature and relative humidity and soil CH4 fluxes were positively correlated; principal component analysis soil temperature and atmospheric temperature, as the first principal component, 0 10cm deep soil moisture content for the second principal component, soil organic matter and soil pH value of third main components, nh4+-n content of fourth principal components, four principal components variance contribution rate was 41.61%. 22.16%, 16.88%, and 13.45%, the cumulative contribution rate of up to 94.11%., therefore, soil moisture and temperature interaction is an important factor influencing soil CH4 fluxes. (3) analysis of the pulse effect of precipitation on soil CH4 fluxes, the results show that the pulse generation of precipitation significantly reduced the ability of black locust forest soil oxidation atmospheric methane; in the early stage of precipitation, influence, lag, recovery and restoration of early late in the 5 period, there were significant differences between the various meteorological elements in October 2014. Precipitation is small, 0 10cm deep soil moisture fluctuation is small, air temperature, relative humidity and solar radiation and other factors affected by the impact of rain, and the influencing factors of atmospheric temperature and solar radiation, so that in the end of the growing season change period is small, the relative humidity becomes the main factors affecting the soil CH4 fluxes in April 2015. , due to the higher precipitation, soil water infiltration usually occur in the rain after a period of time, and may last for hours or days, and since the beginning of the growing season air temperature began to recover, the relative humidity and solar radiation and fast recovery, so that the solar radiation is the main factor affecting soil CH4 fluxes (. 4) through the calculation of soil CH4 fluxes and seasonal fluxes of greenhouse relative potential, this research results show that in spring, summer, autumn, winter four season soil CH4 fluxes were -0.87kg - hm-2, -0.79kg - hm-2, -0.95kg - hm-2 and -0.77kg - hm-2, the proportion of total annual respectively. 23.61%, 21.53%, 25.86% and 20.83%. in spring, summer, autumn, winter four season soil methane warming potential was -21.75kg CO2 hm-2, -19.75 kg CO2 hm-2 -23.75 kg, CO2 hm-2 and -19.25 kg CO2 hm-2. by cumulative research area The annual cumulative flux and relative greenhouse potential indicate that the annual cumulative flux of soil methane is -3.38 kg. Hm-2. A-1, and the relative potential of greenhouse is -84.5 kg, CO2. Hm-2..

【学位授予单位】：中国林业科学研究院
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S714

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