【作者】 张靖；

【导师】 胡克林； 李长生；

【作者基本信息】 中国农业大学 ， 土地利用与信息技术， 2016， 博士

【摘要】 土壤有机质是土壤肥力的重要指标之一,研究其时空演变规律对于保障粮食产量、提升土壤肥力具有重要的意义。本文基于华北平原衡水、昌平、辛集、郑州、曲周5个长期定位试验点的数据,对DNDC模型在该区域的适用性进行了评价,并分析了不同施肥、耕作和秸秆管理方式对作物产量和土壤有机碳(SOC)含量的影响。针对各试验点化肥配施有机肥(或秸秆)的特点,通过情景分析优化了各个试验点的有机无机配施比例。此外,结合RCP4.5情景下的未来气候数据,应用DNDC模型模拟了各试验点从当前到2099年的作物产量和SOC变化趋势。最后,利用京津冀平原区9个监测点的产量和SOC监测数据进行了区域校验,模拟了该区1980-2014年的作物产量和农田SOC的时空变化特征。全文主要结论如下：DNDC模型对5个长期定位试验点作物产量和SOC含量动态变化的模拟效果总体较好,除了衡水点A1B1处理冬小麦产量的模型效率系数EF值为-0.11,吕平点M处理的夏玉米产量EF值为-0.25以外,5个长期定位试验点冬小麦产量的模型模拟评价指数范围分别为：EF值为0.07-0.94,标准化均方根误差NRMSE值为8.8%-66.4%,一致性指数d值为0.66-0.98；夏玉米产量的模型模拟评价指数分别为：EF值为0.24-0.96,NRMSE值为2.6%-40.1%,d值为0.56-0.99；SOC含量的模型模拟评价指数分别为：EF值为0.09-0.98,NRMSE值为2.9%-24.2%,d值为0.45-0.98。各试验点冬小麦产量、夏玉米产量和表层SOC含量的模拟值与实测值的回归分析的决定系数R2分别为0.741-0.973、0.721-0.933和0.308-0.763,均达到了显著水平,说明该模型可用来模拟华北平原5个长期定位试验点不同耕作、施肥和秸秆还田情况下的作物产量和SOC含量的动态变化过程。总施氮量不变情况下,改变有机肥(或秸秆)替代氮肥比例的优化结果为：在衡水试验点,用玉米秸秆替代氮肥的最佳比例为40%,昌平用鸡粪替代氮肥的最佳比例为30%,辛集用堆肥替代氮肥的最佳比例为40%,郑州用饼肥替代氮肥的最佳比例为10%,曲周翻耕和免耕条件下用麦秸替代氮肥的最佳比例分别为40%和10%。氮肥施用量固定改变有机肥(或秸秆)配施量时,各试验点配比优化结果为：衡水氮肥与玉米秸秆供氮配施比例1：2(氮肥120 kg N hm-2和秸秆23762kg hm-2)为最佳配施比例；昌平化肥与鸡粪配供氮施比例为1：0.33的处理(氮肥150 kg N hm-2和鸡粪4000kg hm-2)为最佳；辛集化肥与堆肥供氮配施比例为1：1.33的处理(氮肥120 kg N hm-2和堆肥32000 kg hm-2)为最佳配施比例；在郑州化肥与饼肥供氮配施比例为1：1.67的处理(氮肥120kg N hm-2和饼肥2857 kg hm-2)为最佳配施比例；在曲周试验点,翻耕和免耕条件下,氮肥与麦秸供氮配施比例均为1：0.4(氮肥120 kg N hm-2和麦秸8727 kg hm-2)为适宜的配施比例。各试验点在RCP4.5和当前气候气候情景下从2000年左右到2099年作物产量的模拟结果表明,在衡水试验点,除不施肥的对照处理(CK)外,RCP4.5情景下各处理作物平均产量比当前气候情景下增加了1.2%-3.3%；昌平试验点RCP4.5情景下各处理作物平均产量比当前气候情景下增加了0.7%-15.6%；辛集试验点RCP4.5情景下各处理作物平均产量比当前气候情景下增加了0.4%-10.5；郑州试验点,除了处理CK,RCP4.5情景下各处理作物平均产量比当前气候情景下增加了4.2%-6.0%；曲周试验点,RCP4.5情景与当前气候情景相比,CK和单施化肥处理(F)平均产量减少了5.9%和5.6%,而单施有机肥处理(M)和化肥配施有机肥处理(FM)平均产量增加了3.7%和3.9%。由各试验点在RCP4.5和当前气候气候情景下到2099年的SOC含量变化模拟结果可知,不施肥(处理CK)条件下,到2099年期间,衡水、昌平的SOC含量在RCP4.5和当前气候情景下均呈现下降趋势；辛集的SOC含量在RCP4.5情景下呈现上升趋势,在Basline情景下呈现下降趋势；郑州、曲周的SOC含量在在RCP4.5和当前气候情景下均呈现上升趋势。在衡水、昌平、辛集和郑州,无论是RCP4.5还是当前气候情景下,化肥配施有机肥(FM处理)条件下SOC含量的年增长速率最高,且RCP4.5情景下的增长速率大于当前气候情景。1980-2014年的35年间,京津冀平原区SOC含量空间分布总体北部较高,南部较低,河北中部霸州地区SOC含量有逐渐降低的趋势,尤其是在2000年之后比较明显,且SOC含量较高的区域面积在逐渐缩减,而天津的武清地区SOC含量在逐渐上升,且SOC含量较高的区域面积在不断扩大。在没有秸秆还田的条件下,有10.7%的区域SOC含量35年来总体呈现下降趋势,位于河北中部地区；SOC增加量为0.4-0.8 gkg-1的区域所占比例最大,为60.3%,包括河北中部、中南部、东部地区以及北京东部和天津；SOC增加量最大(1.5-2 g kg-1)的区域位于河北省南端,仅占总面积的3.5%。而1999年10月开始秸秆还田条件下,35年来SOC含量增加量最大为5-8 gkg-1,最小为1.5-2 g kg-1,且没有SOC含量下降的区域可见秸秆还田对于提升京津冀平原区农田SOC含量效果显著。1980-2014年间,京津冀平原区作物产量总体呈现东北较高,西南较低的趋势,而作物产量较高的区域与SOC含量水平高的区域比较一致。更多还原

【Abstract】 Soil organic matter (SOM) is an important indicator of soil fertility, it is of great significance to study its temporal-spatial evolution in order to ensure stable or higher crop yields as well as improve soil fertility.Based on the data of five long-term experiment sites (Hengshui, Changping, Xinji, Zhengzhou and Quzhou) in the NCP, this thesis assesses the applicability of DNDC model and analyzes the impact of different fertilization regimes, tillage and straw management modes on crop yields and topsoil soil organic carbon (SOC). For the modes of combining fertilizers with manures or straw at each site, scenario analysis was conducted to optimize the combining ratios. Besides, we simulated the future trends of crop yields and SOC from present to 2099, based on the future climate datasets under the RCP4.5 and present climate scenario. Moreover, we conducted the regional calibration and validation by utilizing the data of 9 monitoring sites in the Beijing-Tianjin-Hebei Plain (BTH), and then simulated the temporal and spatial variation of SOC and crop yields during 1980-2014 at regional scale. The main results of our study were as follows:Performance of DNDC model in simulating crop yields and topsoil SOC were overally good except that it performed relatively poorly in simulating winter wheat yield of treatment A1B1 in Hengshui site with EF being-0.11 and summer maize yield of treatment M in Changping site with EF of-0.25. And the evaluation statistical indices for winter wheat yields of 5 experiment sites were: modeling efficiency (EF) ranging 0.07-0.94, normalized root mean square error (NRMSE) ranging 8.8%-66.4% and index of agreement (d) ranging 0.66-0.98; and the evaluation statistical indices for summer maize yields were EF ranging 0.24-0.96, NRMSE ranging 2.6%-40.1% and d ranging 0.56-0.99; three valuation statistics for SOC were EF within 0.09-0.98, NRMSE within 2.9%-24.2% and d within 0.45-0.98. The determination coefficients (R2) between simulated and measured values of the winter wheat yields, summer maize yields and SOC contents were 0.741-0.973,0.721-0.973 and 0.308-0.763 respectively (P<0.05) and reached a significant level.In Hengshui, the optimal ratio of maize straw surrogating fertilizer was 40% when the total fertilizer rate was 180 kg N ha-1; in Changping, the optimal ratio of chicken manure surrogating fertilizer was 30% with total fertilizer rate being 270 kg N ha-1; in Xinji, the optimal ratio of compost surrogating fertilizer was 40% with total fertilizer rate being 180 kg N ha-1; Zhengzhou, the optimal ratio of bean cake surrogating fertilizer was 10% with total fertilizer rate being 150 kg N ha-1; in Quzhou, under conventional tillage and no-tillage practice, the optimal ratios of wheat straw surrogating fertilizer were 40% and 10% with total fertilizer rate being 150 kg N ha-1. And the results of scenario analysis of changing manure(or straw) ratio with fixed fertilizer rates were as follows:the ratio between fertilizer and maize straw was 1:2 (120 kg N ha-1 with 23726 kg straw ha-1) in Hengshui; the ratio between fertilizer and chicken manure was 1:0.33 (150 kg N ha-1 with 4000 kg ha-1) in Changping; the ratio between fertilizer and compost was 1:1.33 (120 kg N ha-1 with 32000 kg ha-1) in Xinji; the ratio between fertilizer and bean cake was 1:1.67 (120 kg N ha-1 with 2587 kg ha-1) in Zhengzhou; the ratio between fertilizer and wheat straw was 1:0.4(120 kg N ha-1 with 8727 kg ha-1) in Quzhou.Except treatment CK, future crop yields (2011-2099) of other fertilization regimes in Hengshui under RCP4.5 scenario was 1.2%-3.3% higher than those under present scenario. In Changping, future crop yields (2000-2099) under RCP4.5 scenario was 0.7%-15.6% higher than those under present scenario. The increasing rate under scenario 4.5 in Xinji was 0.4%-10.5%; and in Zhengzhou, the crop yields under scenario RCP4.5 were 4.2%-6.0% higher than those under present scenario; while in Quzhou, future crop yields of treatments CK and F under scenario RCP4.5 decreased compared with those under present Scenario, yet those of treatments M and FM increased by 3.7% and 3.9% respectively. In terms of the future trend of SOC, for treatment CK without fertilization, SOC contents in Hengshui and Changping showed a decreasing trend under both RCP4.5 and present scenarios while SOC contents in Zhengzhou and Quzhou showed an increasing trend under both scenarios, moreover, SOC content in Xinji showed a rising trend under RCP4.5 yet a declining trend under present scenario. And both under RCP4.5 and present scenarios, the highest annual increasing rate of SOC contents occurred in treatments combining fertilizers with manure (or straw), i.e., treatment FM, exceptionally in Quzhou the highest increasing rate occurred in treatment F which was due to the no-tillage practice. In addition, in the 5 experiment sites, the increasing rate of SOC contents under RCP4.5 were higher than that under present scenario.During 35 years(1980-2014), overally SOC content in the BTH plain was higher in the north part and lower in the southern part. And SOC content in the middle of Hebei province (e.g. Bazhou city) showed a gradual decreasing trend which became more evident after 2000, in addition, the area with higher SOC content in this region decreased. However, the SOC content of Wuqing in Tianjin gradually increased and the area with higher SOC content also expanded. Without straw retention, area with declining SOC content accounted for 10.7% of the BTH plain, which is located in the middle of Hebei. Besides, area with SOC increase of 0.4-0.8 g kg-1 accounted the largest area (60.3%) including the central, south-central and eastern part of Hebei province, Tianjin and eastern part of Beijing. The highest SOC increase (1.5-2 g kg-1) occurred in the southernmost part of Hebei which only accounting for 3.5% of the total area. However, under straw retention since 1999, the greatest SOC increase during 35 years was 5-8 g kg-1 and the least increase was 1.5-2 g kg-1, which was higher than that without straw retention, indicating that straw retention can significantly increase SOC content. During 1980-2014, crop yields in the BHT plain presented a trend of higher in the northeastern part and lower in the southwestern part, and the area with higher crop yields was basically consistent with area with relatively higher SOC content.更多还原