黄土塬区农田生态系统水-碳通量特征及产量时程演变趋势

发布时间：2018-01-02 06:20

本文关键词：黄土塬区农田生态系统水-碳通量特征及产量时程演变趋势　出处：《中国科学院研究生院(教育部水土保持与生态环境研究中心)》2016年博士论文　论文类型：学位论文

【摘要】：黄土高原南部塬区属暖温带半湿润大陆性季风气候区,是黄土高原重要的旱作农业区。近三十年来,气候变化和农业生产结构的调整对区域干湿条件、碳收支状况及水循环过程造成显著影响。本文在田间观测的基础上,分析深剖面土壤水热要素的时空动态,探讨水-碳通量的变化特征及其耦合关系,评估气候变化对该区域冬小麦产量的影响,取得如下结果:(1)苜蓿草地(7年)、休闲地、高产农田和低产农田平均土壤含水量分别为15.1±0.5%、22.0±0.4%、19.6±0.5%和21.1±0.4%(0~15 m、年度平均值);干湿交替层季节性失水和蓄水分别出现在3~6月和7~10月,其深度范围分别为0~2 m、0~4.6 m、0~3 m和0~4.2 m。深层土壤水分具有较好的时间稳定性,其垂直分布受土地利用方式的影响,剖面土壤含水量最稳定土层分别为9.8 m、5.4 m、8 m和5.6 m,该层土壤水分接近剖面平均水平。观测年份内苜蓿耗水量呈逐年增加趋势,造成深层土壤的干燥化程度加大,2~10 m土层形成稳定土壤干层,阻断了降水补给地下水的途径;高产农田在冬小麦和春玉米季均出现土壤水分负平衡。四种土地利用方式浅层土壤温度呈现出明显的季节特征,8 m以下土层土壤温度季节和年际间的变化十分微弱。(2)针对不同土地利用方式,通过箱式法从地块尺度上分析了2013~2014年不同生态系统碳通量的时间动态特征,苜蓿草地、高产麦田、低产麦田、高产玉米、低产玉米WUEe分别为3.08、1.74、1.25、1.78和0.88 g C kg-1H2O,苜蓿为较强的碳汇,小麦和玉米表现为较弱碳汇,休闲地则一直为碳源;光合有效辐射(PAR)、气温(Ta)、土壤温度(Ts)和饱和水汽压差(VPD)是影响碳通量的主要因素,不同年份其贡献值有所不同。(3)基于涡度相关研究,麦田生态系统和农田-果园复合生态系统蒸散(ET)、碳通量(GPP)的变化与作物生长和物候关系密切,二者在年内和年际间均表现出较强的正相关关系,生态系统水分利用效率(WUEe)年均值分别为1.84和1.77 g C kg-1 H2O;麦田生态系统碳通量低于复合生态系统,仅对麦田尺度的观测可能对区域碳汇状况造成低估。PAR和VPD是影响水碳通量的主要因素,WUEe随二者增大而出现减小趋势。(4)1957~2013年间冬小麦产量总体表现为波动上升,但其气象产量呈下降趋势,速率为-76.3 kg ha-1 10a-1。气象要素在产量下降中的贡献占12.3%,气温的升高是导致冬小麦气象产量降低的主要因素,降水的减少亦对产量有一定的负面影响。
[Abstract]:The southern tableland of the Loess Plateau belongs to the warm temperate sub-humid continental monsoon climate area, which is an important dry-farming agricultural region on the Loess Plateau. In the last 30 years, climate change and the adjustment of agricultural production structure have affected the regional dry and wet conditions. On the basis of field observation, the spatiotemporal dynamics of soil water and heat elements in deep profile were analyzed, and the characteristics and coupling relationship of water-carbon flux were discussed. An assessment of the impact of climate change on winter wheat production in the region resulted in the following results: 1) Alfalfa grassland (7 years, casual land). The average soil water content in high yield farmland and low yield farmland was 15.1 卤0.5 and 22.0 卤0.4, 19.6 卤0.5% and 21.1 卤0.40.15 m, respectively. Annual average; Seasonal water loss and water storage occurred in the dry and wet alternate layers from 3 to June and from 7 to October, respectively, with a depth range of 0 ~ 2 m and 0 ~ 4. 6 m respectively. The vertical distribution of soil moisture was influenced by the land use pattern, and the soil moisture content of the profile was 9.8 m. The soil moisture of this layer was close to the average level of the profile, and the water consumption of alfalfa increased year by year during the observed year, which resulted in the dryness degree of deep soil increased. (2) stable soil dry layer formed in 10 m soil layer, which blocked the way of recharge of groundwater by precipitation; There was negative soil water balance in winter wheat and spring maize season in high-yield farmland, and the four land use patterns showed obvious seasonal characteristics of shallow soil temperature. The variation of soil temperature between seasons and years under 8 m is very weak. The temporal dynamic characteristics of carbon fluxes in different ecosystems from 2013 to 2014, alfalfa grassland, high yield wheat field, low yield wheat field and high yield corn were analyzed from plot scale by box method. The WUEe of low yield maize was 3.08C / kg ~ (-1) H _ 2O and 1.74C ~ (-1) H _ 2O, respectively. Alfalfa was a strong carbon sink, and wheat and maize were weak carbon sink. Leisure land has always been a carbon source; Photosynthetic available radiation (par), air temperature, soil temperature and saturated water vapor pressure difference (VPD) are the main factors affecting carbon fluxes. Based on the vorticity correlation study, the evapotranspiration of wheat field ecosystem and farm-orchard ecosystem was studied. The change of carbon flux (GPP) was closely related to crop growth and phenology, and there was a strong positive correlation between them during the year and between years. The annual mean water use efficiency (Wue) of ecosystem was 1.84 and 1.77g / kg-1 H _ 2O, respectively. The carbon flux of wheat field ecosystem is lower than that of composite ecosystem, only the observation of wheat field scale may cause underestimation of regional carbon sink. Par and VPD are the main factors influencing water carbon flux. The WUEe decreased with the increase of both. The winter wheat yield fluctuated and increased in 2013, but the meteorological yield showed a downward trend. The rate is -76.3 kg ha-1 10a-1.The contribution of meteorological elements to the yield decline is 12.3%, and the increase of temperature is the main factor leading to the decrease of meteorological yield of winter wheat. The decrease of precipitation also has a negative effect on yield.
【学位授予单位】：中国科学院研究生院(教育部水土保持与生态环境研究中心)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S181

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