The wide-precision planting pattern has become widely used in the North China Plain as a practice for increasing wheat yield.However,the effects of tilled ng developme nt and light tran smissi on within can opy on whe...The wide-precision planting pattern has become widely used in the North China Plain as a practice for increasing wheat yield.However,the effects of tilled ng developme nt and light tran smissi on within can opy on wheat yield un der differe nt sowi ng widths have not bee n clearly described.Therefore,a two-year experime nt was con ducted,in cludi ng four different seeding widths(6 cm,W6;8 cm,W8;10 cm,W10;12 cm,W12)and the traditional planting pattern with seeding width of 4 cm(W4).The results indicated mainly positive effects by the reduced intraspecific competition,specifically all three yield components of W6 and W8 were higher than those for W4.The configurations with more than 10-cm seeding width were mainly affected by the negative effect of a relative homogeneous canopy,leading to the weakened light transmission,leaf senescence,and reduced grain number per spike.Finally,the yields of W6 and W8 were significantly higher than that of W4,whereas the yield in W12 was lower(though not significantly)than W4.In wheat production,therefore,the appropriate seeding width of 6-8 cm is recommended for farmers,whereas the too wide seeding width,with more than 10 cm,should be avoided.展开更多
The National Natural Science Awards, issued by the Ministry of Science and Technology, are the top awards in this country for natural sciences. Among the 51 projects that won the awards in 1997, one earned a first pri...The National Natural Science Awards, issued by the Ministry of Science and Technology, are the top awards in this country for natural sciences. Among the 51 projects that won the awards in 1997, one earned a first prize, eight a second prize, 30 a third prize. The following are some prize-winning projects conductedby, orwith, CAS scientists.展开更多
叶面积指数(Leaf Area Index,LAI)是反映作物生长状态的重要指标,常用植被指数来反演。传统的反演模型大都是基于多变量的多元回归模型,而基于双变量的多元回归模型在LAI反演中的潜力还未被充分发掘。通过提取卫星影像的光谱特征和纹理...叶面积指数(Leaf Area Index,LAI)是反映作物生长状态的重要指标,常用植被指数来反演。传统的反演模型大都是基于多变量的多元回归模型,而基于双变量的多元回归模型在LAI反演中的潜力还未被充分发掘。通过提取卫星影像的光谱特征和纹理特征,基于皮尔逊相关系数分析各个遥感特征与冬小麦LAI之间的相关性,利用简单回归模型(Simple Regression,SR)、多元线性回归模型(Multiple Linear Regression,MLR)和随机森林回归模型(Random Forest Regression,RFR)开展遥感特征与冬小麦LAI之间的关系模型构建反演研究,并结合精度指标(决定系数R2,均方根误差RMSE,相对均方根误差rRMSE)判定各反演模型的反演精度,以提出最优的反演模型。研究表明:①所有植被指数和部分纹理指数在反演LAI中取得了较好的反演效果(R2>0.6)。其中,通用归一化植被指数(Universal Normalized Vegetation Index,UNVI)在各植被指数中表现最好(R2=0.754,RMSE=0.606,rRMSE=12.99%)。除了部分波段的均值特征反演精度与植被指数相当外,大多数纹理特征反演冬小麦LAI的精度欠佳;②通过两两变量组合,得到了冬小麦LAI反演精度最高的双变量多元线性回归模型(R2=0.780,RMSE=0.573,rRMSE=12.29%);③在有多个输入变量(至少3种特征变量)的情况下,RFR的反演效果优于MLR。相较于纹理特征,纹理指数的反演性能更佳。研究结果可为后续基于卫星影像的大规模农作物LAI的监测工作提供一种新的思路与方法。展开更多
基金This work was supported by the Special Fund for Agroscientific Research in the Public Interest,China(201503130).
文摘The wide-precision planting pattern has become widely used in the North China Plain as a practice for increasing wheat yield.However,the effects of tilled ng developme nt and light tran smissi on within can opy on wheat yield un der differe nt sowi ng widths have not bee n clearly described.Therefore,a two-year experime nt was con ducted,in cludi ng four different seeding widths(6 cm,W6;8 cm,W8;10 cm,W10;12 cm,W12)and the traditional planting pattern with seeding width of 4 cm(W4).The results indicated mainly positive effects by the reduced intraspecific competition,specifically all three yield components of W6 and W8 were higher than those for W4.The configurations with more than 10-cm seeding width were mainly affected by the negative effect of a relative homogeneous canopy,leading to the weakened light transmission,leaf senescence,and reduced grain number per spike.Finally,the yields of W6 and W8 were significantly higher than that of W4,whereas the yield in W12 was lower(though not significantly)than W4.In wheat production,therefore,the appropriate seeding width of 6-8 cm is recommended for farmers,whereas the too wide seeding width,with more than 10 cm,should be avoided.
文摘The National Natural Science Awards, issued by the Ministry of Science and Technology, are the top awards in this country for natural sciences. Among the 51 projects that won the awards in 1997, one earned a first prize, eight a second prize, 30 a third prize. The following are some prize-winning projects conductedby, orwith, CAS scientists.
