Impact of climate change on maize yield in China from 1979 to 2016

Climate change severely impacts agricultural production, which jeopardizes food security. China is the second largest maize producer in the world and also the largest consumer of maize. Analyzing the impact of climate change on maize yields can provide effective guidance to national and international economics and politics. Panel models are unable to determine the group-wise heteroscedasticity, cross-sectional correlation and autocorrelation of datasets, therefore we adopted the feasible generalized least square(FGLS) model to evaluate the impact of climate change on maize yields in China from 1979–2016 and got the following results:(1) During the 1979–2016 period, increases in temperature negatively impacted the maize yield of China. For every 1°C increase in temperature, the maize yield was reduced by 5.19 kg 667 m–2(1.7%). Precipitation increased only marginally during this time, and therefore its impact on the maize yield was negligible. For every 1 mm increase in precipitation, the maize yield increased by an insignificant amount of 0.043 kg 667 m–2(0.014%).(2) The impacts of climate change on maize yield differ spatially, with more significant impacts experienced in southern China. In this region, a 1°C increase in temperature resulted in a 7.49 kg 667 m–2 decrease in the maize yield, while the impact of temperature on the maize yield in northern China was insignificant. For every 1 mm increase in precipitation, the maize yield increased by 0.013 kg 667 m–2 in southern China and 0.066 kg 667 m–2 in northern China.(3) The resilience of the maize crop to climate change is strong. The marginal effect of temperature in both southern and northern China during the 1990–2016 period was smaller than that for the 1979–2016 period.     

白云国家森林公园适老性评价及优化分析

指出了人口老龄化是社会发展的必然趋势,也是当前中国面临的重要社会问题之一,国家和地方各级政府出台了一系列政策,切实保障老年人的权益。森林公园除保护其范围内自然环境和自然资源外,为人们的游憩、疗养、避暑和文化娱乐等提供了良好的环境,逐渐成为老年人休闲娱乐生活的选择。选取浙江丽水白云国家森林公园为研究对象,通过实地踏查、问卷调查和随机访谈等方法,深入调查了老年人个人基本资料及背景、活动状况和使用情况,对3类典型空间和4类景观元素进行了详细地分析,针对不足之处提出了相应的优化建议,以期为相关公园绿地的适老性规划设计提供建设思路。     

基于距离相关系数和KNN回归模型的森林蓄积量估测研究

【目的】探究Landsat8 OLI数据和KNN算法在森林蓄积量估测中的潜力。【方法】以湖南省湘潭县为研究区,采用Landsat8 OLI数据和同时期的二类调查数据,通过距离相关系数筛选特征,分别采用线性回归模型(MLR)、K-近邻模型(KNN)、距离加权KNN模型(DW-KNN)和优化欧式KNN模型(FW-KNN)对森林蓄积量进行估测。使用十折交叉方法进行精度检验,对检验结果进行对比分析。【结果】3种KNN模型的估测结果均高于传统的线性模型,并且在3种KNN模型中,FW-KNN算法效果最好,决定系数达到0.69,为3种模型中最高;3种KNN模型中,本研究优化欧氏距离KNN模型的估测精度最高,其均方根误差为30.3%,相比于传统KNN模型的均方根误差降低了5.1%,相比于DW-KNN模型降低了3.3%。【结论】采用DW-KNN蓄积量估测结果明显优于其他两种模型,说明通过特征与蓄积量的相关性优化样本间的距离是一种可行的KNN优化方法。     

不同施肥处理对马铃薯农田土壤理化性状及产量的影响

为了探究不同施肥处理对马铃薯农田土壤理化性状及产量的影响,试验地采用马铃薯连作模式,设置3个施肥处理,即：单施化肥(T)、有机肥配施化肥(YTF 1/2)、全量有机肥(YTF)。结果表明：在不同施肥处理下马铃薯农田土壤的理化性质和马铃薯产量发生了变化,其中变化最为明显的土壤指标有土壤容重、孔隙度、饱和导水率、有效磷。YTF处理较T处理可分别显著(P<0.05)降低土壤容重16.8%,增加土壤孔隙度12.7%,提升饱和导水率25.3%。YTF处理可显著提升土壤有效磷含量43.0%,但各处理间土壤pH、有机碳、全氮、全磷、碱解氮、速效钾之间差异并未达到显著水平。同时,较之T处理,YTF处理亦可显著提升土壤团聚体含量。YTF和YTF 1/2处理可分别较T处理提升马铃薯产量24.6%和12.8%。因此,施用有机肥不仅可以改善土壤结构,改良土壤物理性状,亦能促产增收。     

茶树花青素形成分子机理的研究进展

花青素是由类黄酮合成途径产生的次生代谢产物,含量高时会使茶树新梢呈现红色或紫色。同时,花青素相比儿茶素等具有更明显的抗氧化、预防肿瘤等药理保健作用。文章就茶树花青素合成途径、转录及转录后调控等方面进行综述,以期更好地为高花青素茶树的育种研究提供理论依据。     

不同秧龄对沿江地区双季晚稻秧苗素质及产量的影响

以早熟高产品种上农粳2号和镇稻18为材料,采用常规毯苗机械栽插,分别设置20 d、24 d、28 d、32 d等4个秧龄处理,研究不同秧龄对沿江地区双季晚稻秧苗素质、生育进程、茎蘖动态及产量构成的影响。结果表明,随秧龄天数增加,参试品种的绿叶数、茎基宽和根系盘结力均逐渐升高;与20 d、24 d和28 d秧龄的处理相比,32 d秧龄处理的成熟期提前4~5 d,茎蘖高峰期提早15 d左右,结实率显著升高;与24 d秧龄处理相比,上农粳2号和镇稻18在32 d秧龄处理下的产量分别提高10.26%和20.82%。在秧苗强化化控和苗床管理的条件下,安徽沿江地区常规毯苗机插的栽插秧龄可延长至32 d。     

王正非林火蔓延模型改进研究

王正非林火蔓延模型是目前国内比较先进的森林火灾蔓延模型,但是由于林火行为的复杂性,此模型在准确率和普适性方面仍存在许多不足。本文结合已有的成果进一步改进王正非模型,增加了可燃物湿度对林火蔓延速度的影响,改进了林火初始速度的计算方式。针对各种坡度对林火蔓延行为的影响给出了一个计算公式。与改进前相比,改进后的模型使其对林火蔓延情况的预估更为精准。     

Compatibility of root growth and tuber production of potato cultivars with dynamic and static water‐saving irrigation managements

The important root characteristics of root length density (RLD) and root mass density (RMD) generally differ among irrigation managements and potato cultivars. The objective of this study was to investigate the RLD and RMD variations and their functional relationships with gross potato tuber yield for two commercial potato cultivars, Agria and Sante, under different irrigation strategies. Full irrigation and water‐saving irrigation strategies, deficit and partial root drying irrigations, were applied statically (S) and dynamically (D) based on daily crop evapotranspiration. Results showed that SPRD had significantly greater RLD (3.64 cm/cm³) and RMD (132.7 μg/cm³) than other irrigation treatments. Between the potato cultivars, Agria had significantly larger values of RLD (3.50 cm/cm³) and RMD (138.7 μg/cm³) than Sante. The functional relationship between the root growth characteristics and tuber yield showed that under water‐saving irrigations, Agria increased root mass at the expense of gross tuber yield but Sante increased root mass to maintain larger gross tuber yields. However, Agria produced more roots and gross tuber yield than Sante, and it is concluded that Agria is a more drought‐tolerant potato cultivar, which is recommended for tuber production in regions where water might be scarce. It was shown that larger root production in potatoes was associated with improved tolerance to water stress.