Impacts of Rice Field Winter Planting on Soil Organic Carbon and Carbon Management Index

To tackle with the problem of prevailing farmland abandonment in winter,5 treatments includes Chinese milk vetch-double cropping rice(CRR),rape-double cropping rice(RRR),garlic-double cropping rice(GRR),winter crop multiple cropping rotation(ROT),winter fallow control(WRR)were set up.By measuring soil total organic carbon,active organic carbon and its components and calculating the soil carbon pool management index in 0~15 cm and 15~30 cm soil layers in the early and late rice ripening stage.The effects of different winter planting patterns on the changes of soil organic carbon and carbon pool management index were discussed.In order to provide theoretical basis for the optimization and adjustment of winter planting pattern of double cropping rice field in the middle reaches of Yangtze River.The results showed that soil total organic carbon,active organic carbon and its components in different winter cropping patterns were increased,and ROT and CRR treatments were more beneficial to the accumulation of soil total organic carbon,active organic carbon and its components as well as the improvement of soil carbon pool management index,which should be preferred in the adjustment of cropping patterns.

The Possible Effect of Climate Warming on Northern Limits of Cropping System and Crop Yield in China

Significantly increasing temperature since the 1980s in China has become a consensus under the background of global climate change and how climate change affects agriculture or even cropping systems has attracted more and more attention from Chinese government and scientists. In this study, the possible effects of climate warming on the national northern limits of cropping systems, the northern limits of winter wheat and double rice, and the stable-yield northern limits of rainfed winter wheat-summer maize rotation in China from 1981 to 2007 were analyzed. Also, the possible change of crop yield caused by planting limits displacement during the periods 1950s-1981 and 1981-2007 was compared and discussed. The recognized calculation methods of agricultural climatic indices were employed. According to the indices of climatic regionalization for cropping systems, the national northern limits of cropping systems, winter wheat and double rice, and the stable-yield northern limits of rainfed winter wheat-summer maize rotation during two periods, including the 1950s-1980 and 1981-2007, were drawn with ArcGIS software. Compared with the situation during the 1950s- 1980, the northern limits of double cropping system during 1981-2007 showed significant spatial displacement in Shaanxi, Shanxi, Hebei, and Liaoning provinces and Beijing municipality, China. The northern limits of triple cropping system showed the maximum spatial displacement in Hunan, Hubei, Anhui, Jiangsu, and Zhejiang provinces, China. Without considering variety change and social economic factors, the per unit area grain yield of main planting patterns would increase about 54-106% if single cropping system was replaced by double cropping system, which turned out to be 27- 58% if double cropping system was replaced by triple cropping system. In Liaoning, Hebei, Shanxi, Shaanxi, Gansu, and Qinghai provinces, Inner Mongolia and Ningxia autonomous regions, China, the northern limits of winter wheat during 1981-2007 moved northward and expanded westward in different degrees, compared with those during the 1950s-1980. Taking Hebei Province as an example, the northern limits of winter wheat moved northward, and the per unit area grain yield would averagely increase about 25% in the change region if the spring wheat was replaced by winter wheat. In Zhejiang, Anhui, Hubei, and Hunan provinces, China, the planting northern limits of double rice moved northward, and the per unit area grain yield would increase in different degrees only from the perspective of heat resource. The stable- yield northern limits of rainfed winter wheat-summer maize rotation moved southeastward in most regions, which was caused by the decrease of local precipitation in recent years. During the past 50 yr, climate warming made the national northern limits of cropping systems move northward in different degrees, the northern limits of winter wheat and double rice both moved northward, and the cropping system change would cause the increase of per unit area grain yield in the change region. However, the stable-yield northern limits of rainfed winter wheat-summer maize rotation moved southeastward due to the decrease of precipitation.

Mechanism for winter cold-mediated epigenetic silencing of a potent floral repressor in plants

Subject Code:C02With the support by the Chinese Academy of Sciences(CAS),the research team of Plant Environmental Epigenetics led by Prof.He Yuehui(何跃辉)at the Shanghai Center for Plant Stress Biology,CAS and CAS Center for Excellence of Molecular Plant Sciences,discovered a molecular epigenetic mechanism underlying how winter cold enables plants to flower in spring,which was published in Nature Genetics(2016,48:1527—1534).