过去20年中国耕地生产力区域差异变化研究

依据县域农业统计数据,以单位耕地面积的粮食产量作为衡量耕地基本生产力的指标,对比分析了1985~1987和 2002~2004两个时段的耕地生产力空间变化情况。结果表明:① 过去20年全国大部分地区耕地生产力普遍提高,在农牧交错带及其以西地区耕地生产力增加幅度尤为显著,这些地区耕地生产力的提高对全国粮食总产量增加具有重要意义;② 受中国降水空间分异影响,耕地生产力的东西差异依然显著,农牧交错带耕地生产力最低;农牧交错带以东,自西北向东南耕地生产力逐渐增高,耕地生产力区内差异在2002~2004年已表现得不明显;农牧交错带以西,耕地生产力相对增长速度明显快于东侧和农牧交错带;东部地区,由于北方耕地生产力增幅明显,以温度为主导的南北差异已经缩小。     

Erosion effect on the productivity of black soil in Northeast China

Continuous soil erosion has caused serious land degradation in the black soil area of Northeast China. The primary objective of this study was to determine the effects of accelerated erosion on soil productivity, as measured by soybean (Glycine max L. Merr.) yields. Eight erosion levels, 0, 10, 20, 30, 40, 50, 60, and 70 cm, were simulated by imitating the integrated process of natural erosion and tillage activity. Each erosion level had two sub-treatments: conventional fertilization and no fertilization. Soil erosion was found to affect survival probability and to cause remarkable reductions in the Leaf Area Index (LAI), plant height, pod number, biomass, and yield. Soybean yield was exponentially decreased with the increase of soil erosion depth. Compared to erosion depth of 0 cm, erosion levels of 10, 20, 30, 40, 50, 60, and 70 cm experienced reductions in soybean yield by 28.8%, 37.8%, 43.5%, 52.6%, 53.1%, 52.9%, and 64.1% respectively when fertilized whereas the reductions at those levels were 32.6%, 42.2%, 53.0%, 54.0%, 65.8%, 69.7%, and 72.6%, respectively, when unfertilized. At the erosion depths of 10, 20, 30, 40, 50, 60, and 70 cm, the yield reductions per 10 cm of soil eroded when fertilized were 28.8%, 18.9%, 14.5%, 13.2%, 10.6%, 8.8%, and 9.2%, averaged 14.9%, but when unfertilized they were 32.6%, 21.1%, 17.7%, 13.5%, 13.2%, 11.6%, and 10.4%, averaged 17.1%. The results also showed that chemical fertilizers could enhance the yields of eroded soil, but could not recover the yields to the pre-erosion level. Additionally, the results indicated that the primary reason for the decrease in soybean yield with increasing erosion depth was the loss of soil organic matter, soil N and P. These results may aid in selecting effective soil erosion control strategy, forecasting land degradation, establishing soil erosion tolerance, and evaluating the economic cost of soil erosion in the black soil region in Northeast China Supported by National Natural Science Foundation of China (Grant No. 40471082) and National Basic Research Program of China (Grant No. 2007CB407204)     

The Monsoon in the Arabian Sea: Implications From Radiolarian Fluxes to the Deep Sea

THE MONSOON IN THE ARABIAN SEA:IMPLICATIONS FROM RADIOLARIAN FLUXES TO THE DEEP SEA     

西双版纳近40年气候变化对自然植被净第一性生产力的影响

从西双版纳地区近 4 0年自然植被净第一性生产力 (NPP)的时空变化 ,讨论了“暖湿型”、“暖干型”气候变化对植被NPP的影响。结果表明 ,西双版纳地区近 4 0年NPP平均为 1 7.589t/hm2 ·a-1,呈略为下降的趋势 ;当年均温升高 2℃、降水量增多 2 0 %时 ,NPP呈升高趋势 ;当年均温升高 2℃、降水量减少 2 0 %时 ,全区大部分地区NPP呈降低趋势 ,部分地区略有升高     

黄河三角洲新垦耕地年龄及其生产能力指数的遥感监测

黄河三角洲是我国重要的土地后备资源集中分布区,对黄河河口滩地的开垦成为了保持山东省乃至全国耕地动态平衡的关键。本文以东营市、垦利县、河口区和利津县作为研究区,利用6期(1984、1995、2000、2004、2008和2010年)TM影像,对黄河三角洲地区的耕地资源动态变化和耕地年龄进行了遥感监测和推定,并利用熵权法以植被指数(EVI和MSAVI)、植被覆盖度(Fv)和温度植被干燥指数(TVDI)为指标因子的耕地生产能力指数构建了评价模型。研究结果表明:在1984-2010年的26年时间里,研究区的耕地动态变化显著,新垦耕地面积达到77 362.33hm2,大部分来源于草地的开垦。其中,耕地年龄在8-12年期间的新垦耕地面积最多,占了新垦耕地面积的34.47%;研究区新垦耕地的生产能力指数呈现随着耕作时间的增加而增加的趋势,耕作时间在2-4年之内的新垦耕地平均生产能力指数,仅有传统耕地平均指数的67.66%;研究区传统耕地的生产能力指数大体上也在随着耕作时间的增加而提高,传统耕地在2010年的平均生产能力指数比1984年提高了76.51%。     

非均质各向异性油藏水平井流入动态

为分析渗透率非均质性对水平井流入动态的影响,根据质量和动量守恒定律,建立全耦合的非均质各向异性盒式油藏渗流与水平井筒变质量流的耦合模型;通过坐标变换建立各向异性油藏水平井非均质表皮计算模型,将非均质渗透率场转化为等效均质渗透率场和沿井筒变化的非均质表皮;应用源函数法和势的叠加原理得到油藏渗流模型的解,给出基于模型离散的顺序迭代解耦方法.结果表明:渗透率非均质性对水平井流量剖面和采油指数影响较大.水平井流量分布规律与近井渗透率变化规律基本相同;高渗区流量大,低渗区流量小;在等效渗透率相同的情况下,随着近井非均质性的增强,水平井平均采油指数逐渐降低,平均流量分布不均衡因数逐渐增大.该研究为非均质各向异性油藏水平井产能预测和完井参数优化提供了依据.     

普光气藏长井段合采产能方程异常特征及消除方法

针对普光气藏储层普遍具有储层厚度大、层间非均质性强、生产井段长、产量高、生产压差小特点,导致二项式产能分析的直线段斜率对井底流压非常敏感,巨厚气藏的井底流压的取值深度不再能简单地选取地层的中部深度,产能试井解释出现异常(负斜率),综合考虑储层的巨厚、非均质性对井筒压力分布影响,利用数值模拟,分析井底压力计位置对产能方程影响,给出长井段合采产能方程出现异常(负斜率)原因,建立考虑地层系数影响的消除长井段合采产能方程异常的方法,即将压力计放在地层系数为总地层系数1/2的位置.该方法能有效避免二项式产能分析过程中出现负斜率的现象.     

DB气田非均质储层级别划分及常规测井识别方法

DB气田以裂缝-孔隙型、孔隙型岩屑砂岩储层为主,非均质性强,裂缝发育程度是决定产能高低的关键因素之一.立足于储层的录井、岩心分析和测井资料,开发了储层级别划分和常规测井识别储层级别的方法.首先,定义了每米产能指数作为标准化的产能参数;其次,基于产能参数与储层物性参数关系的考察,筛选综合物性参数(孔隙度和总渗透率的乘积)作为储层级别划分的评价指标,将DB气田储层分成了2个级别,给出了分级的物性标准;最后,应用主成分分析法计算了综合主成分,基于综合主成分与每米产能指数交会图给出了应用常规测井资料识别储层级别的标准.2口井的应用效果表明,依据上述方法划分及识别的储层级别与生产情况吻合得较好.     

Exploring socio-hydrological determinants of crop yield in under-performing irrigation schemes: pathways for sustainable intensification

ABSTRACT

Understanding the human–water–food–climate nexus is central to achieving sustainable intensification (SI) in agriculture. This research uses a socio-hydrological approach to understand the underpinning for implementing SI in the Gezira Irrigation Scheme, Sudan, by integrating vegetation indices derived from remote sensing, ancillary, gridded soil and precipitation data, supplemented by interviews with 393 farmers. The productivity gap was estimated as the difference between the potential and actual productivities. Based upon data on farmers’ socio-economic status and field practices, a regression tree model was built to determine the factors that control the sorghum yield. The model revealed that the financial status of farmers and access to water are the most influential factors on sorghum yield. A conceptual framework that elucidates SI and its bi-directional feedback to the environment, society and the economy is proposed. Implementing SI in the scheme has implications on water and food security in Sudan and beyond its borders.     

海南省耕地地力水平分布及影响因素——以澄迈和陵水县为例

以澄迈和陵水黎族自治县为研究区,在构建包含土壤理化性质、土壤养分、立地条件和土壤管理在内的4个子目标、11个具体指标的耕地地力评价指标体系的基础上,采用模糊数学理论确定指标隶属度,结合层次分析法进行加权求和,对澄迈和陵水进行耕地地力水平综合评价,阐明其耕地地力水平的分布特征和影响因素。结果表明：1）澄迈和陵水的耕地地力为中等水平,且澄迈的耕地地力相对较高,母质和地形因素是两县耕地地力水平差异的主导因素;2）耕地地力水平分布格局与地形和水系分布关系较为紧密,谷底平原、平原和山麓平原地区耕地地力水平较高,降雨和地形因素是导致区内耕地地力分布不均的主要因素。