Quantification winter wheat LAI with HJ-1CCD image features over multiple growing seasons

Remote sensing images are widely used to map leaf area index (LAI) continuously over landscape. The objective of this study is to explore the ideal image features from Chinese HJ-1 A/B CCD images for estimating winter wheat LAI in Beijing. Image features were extracted from such images over four seasons of winter wheat growth, including five vegetation indices (VIs), principal components (PC), tasseled cap transformations (TCT) and texture parameters. The LAI was significantly correlated with the near-infrared reflectance band, five VIs [normalized difference vegetation index, enhanced vegetation index (EVI), modified nonlinear vegetation index (MNLI), optimization of soil-adjusted vegetation index, and ratio vegetation index], the first principal component (PC1) and the second TCT component (TCT2). However, these image features cannot significantly improve the estimation accuracy of winter wheat LAI in conjunction with eight texture measures. To determine the few ideal features with the best estimation accuracy, partial least squares regression (PLSR) and variable importance in projection (VIP) were applied to predict LAI values. Four remote sensing features (TCT2, PC1, MNLI and EVI) were chosen based on VIP values. The result of leave-one-out cross-validation demonstrated that the PLSR model based on these four features produced better result than the ten features’ model, throughout the whole growing season. The results of this study suggest that selecting a few ideal image features is sufficient for LAI estimation.     

二氧化碳浓度增加对冬小麦生长发育影响的数值模拟

根据国内外小麦生长模拟研究成果,借鉴荷兰学者的模拟思路,从作物生长的主要生理过程人手,综合考虑气候变暖与大气中CO2浓度增加等因素对作物生长发育和产量形成的影响,修正了在一级生产水平下冬小麦生长模拟模式,使得模式能够对CO2浓度的变化做出相应的反应。经资料检验,在当前CO2浓度下,冬小麦总干重和穗干重的模拟平均相对误差小于10％,其它器官干重及叶面积指数的模拟也取得了较好的结果。运用改进后的模式模拟试验了未来气候变暖和CO2倍增对冬小麦生长发育的可能影响。     

冬小麦光合生产潜力数值模拟*

利用中国小麦生态实验资料建立了黄淮海地区冬小麦发育阶段模式和光合作用、呼吸作用等模式,由这些子模式连结成为一个可以模拟瞬时光合作用的,充分考虑了叶片空间分布特征的冬小麦光合生产潜力模式。运用该模式研究结果证明冬小麦光合生产潜力与抽穗前10天至成熟期辐射量相关性最大。黄淮海地区冬小麦光合生产潜力可达到800kg/亩～1000kg/亩,与牛文元计算结果相近。功率谱分析结果表明北京地区光合生产潜力存在3年～4年和9年～10年的变化周期。此外,文中还给出了CO₂升高后冬小麦光合生产潜力的可能变化情况。     

河西绿洲区春小麦蒸腾蒸散的变化研究

在甘肃张掖绿洲区利用浮力称重式蒸散仪对春小麦蒸散量进行了测定,对蒸散量的日变化和季节变化特征进行了论述。研究结果表明:小麦田的日蒸散量在白天12:00~16:00达到最大,夜间20:00~08:00最小甚至呈负值。灌溉前后蒸腾强度出现峰值的时间有所变化。但灌溉以后,蒸腾与蒸散量均呈增大趋势。日蒸散量随着净辐射的增加而加大。在小麦不同的生育阶段,蒸散量有所不同,小麦拔节以前较小,拔节以后开始增大,灌浆期达到最大,接近成熟时逐渐降低。     

河北平原冬小麦播种面积收缩对农业水资源消耗的影响(英文)

This study firstly analyzed the shrinkage of winter wheat and the changes of cropping systems in the Hebei Plain from 1998 to 2010 based on the agricultural statistic data of 11 cities and meteorological data, including daily temperature, precipitation, water vapor, wind speed and minimum relative humidity data from 22 meteorological stations, and then calculated the water deficit and irrigation water resources required by different cropping systems, as well as the irrigation water resources conserved as a result of cropping system changes, using crop coefficient method and every ten-day effective precipitation estimation method. The results are as follows. 1) The sown areas of winter wheat in the 11 cities in the Hebei Plain all shrunk during the study period. The shrinkage rate was 16.07% and the total shrinkage area amounted to 49.62×104ha. The shrinkage was most serious in the Beijing-Tianjin-Tangshan metropolitan agglomerate, with a shrinkage rate of 47.23%. 2) The precipitation fill rate of winter wheat was only 20%–30%, while those of spring maize and summer maize both exceeded 50%. The irrigation water resources demanded by the winter wheat-summer maize double cropping system ranged from 400 mm to 530 mm, while those demanded by the spring maize single cropping system ranged only from 160 mm to 210 mm. 3) The water resources conserved as a result of the winter wheat sown area shrinkage during the study period were about 15.96×108m3/a, accounting for 27.85% of those provided for Beijing, Tianjin and Hebei by the first phase of the Mid-Route of the South-to-North Water Diversion Project.     

气候变化对海河流域主要作物物候和产量影响

基于海河流域30 个气象站点1960-2009年的实测资料,分析该流域1960年以来农业气象指标的变化趋势,并利用VIP模型模拟分析大气CO₂浓度增加、温度、降雨和日照时数变化对作物产量的影响。结果显示：冬季温度的显著上升使冬小麦种植北界在50年间向北移动大约70 km;在品种和灌溉条件不变的前提下,小麦产量平均每10年上升0.2%~3.4%,其中CO₂浓度增加、温度、降雨及日照时数变化对其产量的影响分别为11.0%、0.7%、-0.2%和-6.5%;大气CO₂浓度增加的产量正效应大于日照时数减少的负效应。气候变化使夏玉米产量呈下降趋势（0.6%~3.8%/10年）,其中大气CO₂浓度增加、温度、降雨及日照时数变化对其产量的影响分别为0.7%、-3.6%、-1.0%和-6.8%,温度上升和辐射下降是玉米产量下降的主要原因。研究结果可为气候变化影响的评估和适应性对策制定提供科学依据。     

畜禽粪便农用区土壤-小麦系统中重金属污染及迁移

畜禽粪便农用导致农产品中重金属含量超标,通过生物链传递,最终会影响人体健康。以山东禹城典型畜禽粪便农用区为例,研究了不同畜禽粪便农用区土壤—小麦系统中重金属的污染及迁移累积情况。结果显示:某些区域存在着一定的重金属污染,鸡粪农用区、猪粪农用区污染较高,综合污染指数均值分别为0.83、0.78,都达到了警戒级,其中某些点的污染指数超过了1和2,达到了轻污染或中污染级;牛粪农用区污染较轻,综合污染指数为安全级。不同畜禽粪便农用区小麦中的Cr、Ni、Cd、As均存在不同程度超标情况,其中鸡粪农用区Cr的超标率达66.67%,Ni、Pb超标率都为16.67%;牛粪农用区小麦中Cr、Ni超标,Cr超标率达91.67%;猪粪农用区小麦中只有Cr超标,超标率为41.67%。研究区小麦显示出不同的重金属富集能力,小麦对Cd、Zn、Cu几种元素的富集情况较高,而对Pb、As的富集能力则较低。除Zn外,小麦茎叶对同一种重金属的富集能力要大于小麦的种子。     

生物工程处理草浆造纸废水系统的特点

文章通过对许昌造纸厂废水处理系统的论述 ,介绍了以生化为主的碱法草浆造纸废水治理成套技术的概况、工艺流程、投资概算和运行成本等 ,并进一步阐明了这套技术的科学性、实用性和先进性     

基于高光谱数据的小麦叶绿素含量反演

近年来,遥感高光谱技术为获取农作物的某些生理化参数提供了丰富的数据来源。该文使用北京小汤山地区实验获取的小麦高光谱数据,应用偏最小二乘回归方法,建立了冬小麦冠层波谱与叶绿素含量的回归反演计算模型。研究结果显示:模型在350～1060nm波段具有较高的反演精度。本研究为应用高光谱数据反演冬小麦叶绿素含量提供了有效途径。     

长江三角洲地区小麦植株的重金属分布及其相关性——以昆山市为例

以苏州昆山市为典型区,测定该地区小麦植株根、茎、叶、籽粒及对应点位土壤中Hg、As、Cr、Cu、Ni、Pb、Zn、Cd这8种重金属含量,探究长江三角洲地区小麦植株各器官重金属的吸收状况及其关联分析。结果显示,小麦根对各种重金属的吸收能力最强,各器官以及小麦全植株对Cd的吸收系数最大而对Cr的最小;小麦籽粒重金属含量与根、茎、叶中重金属含量存在一定的相关性,但没有确定的规律;Hg、Zn、Cd这3种重金属的潜在生态风险都达到中等以上级别,8种重金属的综合潜在生态风险达到较高级别。