Impact of Agricultural Labor Transfer on Agricultural Nonpoint Source Pollution: A Case Study of Jiangxi,China

A large proportion of the rural labor force in China will continue to transfer to non-agricultural sectors in the near future, which will inevitably lead to the transformation of the agricultural production mode and the structure of the farmers’ livelihood. The Chinese government is making great efforts to govern agricultural nonpoint source pollution (ANSP), and farmers' environmental behavior is a key factor that must be considered in the formulation of agricultural environmental policies. Based on a set of micro survey data on farmers in the study area and econometric methods, this study investigates the impact of agricultural labor transfer on ANSP by considering the substitution effect of agricultural factors and the effect of agricultural economies of scale. The results show that the increase of the agricultural labor force will not be conducive to reducing ANSP, while the income increase brought by agricultural labor transfer will improve the input structure of agricultural factors and have a positive impact on ANSP reduction. Government departments should provide subsidies or incentive measures to help agricultural social service organizations to expand their coverage and increase the frequency of socialized agricultural services, in order to guide farmers in the use of environment-friendly agricultural technology to reduce the ANSP caused by agricultural factors at the source. Furthermore, it is necessary to facilitate the development of small-sized agricultural machinery suitable for small-area land cultivation.     

玉米秸秆带状覆盖对西北旱地土壤温度及马铃薯产量的影响

设黑膜大垄（M1）、玉米秸秆带状平覆（M2）、玉米秸秆带状垄沟覆杆（M3）和不覆盖露地平作（CK）4个处理进行田间小区试验,对比研究不同覆盖方式对西北旱地土壤温度及马铃薯产量的影响。结果表明：M1较CK提高全生育期土壤温度0.98℃,主要提高了块茎膨大期5 cm土层（2015年）及淀粉积累期10 cm土层（2016年）的土壤温度;M2、M3较CK降低全生育期土壤温度1.06℃、0.59℃,主要降低了块茎形成期10 cm土层的土壤温度。两年M1、M2、M3分别平均较CK增产11.68%、21.74%、16.88%。产量与淀粉积累期至收获期单株结薯数、单株产量正相关（r=0.064~0.766）,覆盖处理显著较CK提高淀粉积累期单株结薯数及单株产量,平水年以M1最好,偏旱年以M2最好。     

农户行为视角下的乡村生产空间系统运行机制及重构启示

农户行为转变是乡村生产空间系统量变或从量变到质变的重要驱动力,乡村生产空间系统的运行实质上是农户行为作用的外在表现,厘清农户行为可为诠释乡村生产空间系统的运行机制提供平台。本文在剖析农户行为转变与乡村生产空间系统运行响应的理论框架基础上,从农户行为转变和乡村生产空间系统响应入手构建指标体系,建立模糊综合评价量化模型,并以重庆市江津区恒和村作为实证,诠释乡村生产空间系统运行机制。主要研究结论为：不同农户行为对乡村生产空间系统运行的影响程度各异,大体为生产大户>合作社农户>传统农户;不同农户行为对系统运行响应结果的作用差异明显,生产大户行为主要影响乡村生产空间的利用效率,合作社农户行为对提升生产空间系统经济效益作用明显,传统农户行为对生产空间系统环境改善的贡献作用最小。并从经济、社会、空间重构视角提出发展多种形式的适度规模化经营、培育新型农业经营主体和职业农民、合理引导农户技术和资本投入等建议,以实现乡村生产空间系统协调与均衡发展。     

Early middle Holocene climate oscillations recorded in the Beihuqiao Core,Yuhang, Zhejiang Province,China

A long-standing controversy exists concerning the spatial and temporal characteristics of Holocene climate change in China. Zhejiang is located in the southeast of China, where the East Asian monsoon dominates the climate and a Neolithic culture flourished. In recent years, geographers have debated the climatic conditions existing at the time of the Neolithic cultures. This study reconstructed the sedimentary environment between 11.30 and 4.17 cal ka BP based on a multi-proxy analysis of a 14.3 meter sediment core, drilled in Beihuqiao, Zhejiang Province, China. The results show: (1) The climate was getting warm between 11.50 and 8.77 cal ka BP. Grain size became finer from the bottom to the top layer, accompanied by an increase in the chemical index of alteration (CIA), Mg/Sr ratio, the percentage of clay, pollen concentrations, and a decrease in SiO₂/Al₂O₃ ratio, and the value of bases–alumina (ba), as well as other trace elements. (2) Between 8.77 and 7.99 cal ka BP, the sediment is composed of gray-yellow and gray silt. The percentage of CaO and the ratio of CaO + Na₂O + K₂O to Al₂O₃ is much higher. The pollen concentration sharply decreases. The climate was cold and dry in the early stages of this period, but became relatively warmer and wetter in the later stages. (3) The Holocene Climatic Optimum occurred at 7.99–5.68 cal ka BP. Higher contents of clay, total Fe₂O₃, Al₂O₃, CIA, the chemical proxy of alteration, pollen concentration, evergreen pollens, and high values of Mg/Sr are observed at this stage, coinciding with a lower SiO₂/Al₂O₃ value, (CaO + Na₂O + K₂O)/Al₂O₃ ratio, and an obvious reduction in silt/clay, and SiO₂ and CaO concentrations. (4) During the period 5.68–4.17 cal ka BP, the temperature in the study area declined in a stepwise fashion. The grain size became finer, and the Mg/Sr ratio decreased gradually.     

Household and community responses to impacts of climate change in the rural hills of Nepal

The research was designed to answer how households and local communities in rural Nepal are responding to the impacts of climate change. Using four villages as case study units, a mixed method approach was adopted in a multi-scaled process carried out at community, district and national levels. The research found that adaptation practices being adopted differ according to household well-being and are largely governed by access to education, information and resources within the community. Responses such as livelihood and income diversification, internal migration, share cropping, taking consumption loans, use of alternative energy and use of bio-pesticides were found to mostly vary according to well-being status of the interviewees. Development of adaptation plans, strategies and support mechanisms should take account of the different adaptation practices and needs of households. If such individual situations are not considered, adaptation responses may be ineffective or even be maladaptive and increase vulnerability. The research also found that the autonomous, unplanned and reactive nature of adaptation practices chosen by rural communities can contribute to further inequity and unequal power relations. The knowledge generated from this research contributes to understanding of how climate change contributes to vulnerability, but also how local practices and lack of an effective climate policy or response measures may magnify the effects of many existing drivers of vulnerability in terms of maladaptation and increasing social inequalities.     

北京不同区域气溶胶辐射效应

采用大气辐射传输模式SES2以及2013年1月—2015年10月欧洲中期天气预报中心细网格再分析资料计算了北京地区4个观测站地面接收的短波辐射通量,分析了晴天和云天北京城郊气溶胶对总辐射的定量影响时空变化特征。结果表明:北京城区和近郊区气溶胶对总辐射的影响约为远郊区的2倍,北京南部和西部气溶胶对辐射的影响较大,晴天和云天北京城区和近郊区气溶胶对总辐射的削减值分别为146.23~180.99 W·m-2和202.11~217.02 W·m-2,晴天总辐射削减空间差异较大;秋冬季气溶胶对总辐射的影响明显大于春夏季,北京市观象台秋冬季气溶胶对总辐射的削减作用最大可达60%,较春夏季高10%~20%;北京城郊总辐射和直接辐射削减率与气溶胶光学厚度变化均呈线性关系,近地面PM_2.5浓度对辐射的影响不容忽视。     

High-Resolution Vertical Profile Measurements for Carbon Dioxide and Water Vapour Concentrations Within and Above Crop Canopies

We present a portable elevator-based facility for measuring \(\hbox {CO}_{2}\), water vapour, temperature and wind-speed profiles between the soil surface and the atmospheric surface layer above crop canopies. The end of a tube connected to a closed-path gas analyzer is continuously moved up and down over the profile range (in our case, approximately 2 m) while concentrations are logged at a frequency of \(20 \hbox { s}^{-1}\). Using campaign measurements in winter wheat, winter barley and a catch crop mixture (spring 2015 to autumn 2016) during different stages of crop development and different times of the day, we demonstrate a simple approach to correct for time lags, and the resulting profiles of 30-min mean mole fractions of \(\hbox {CO}_{2}\) and \(\hbox {H}_{2}\hbox {O}\) over height increments of 0.025 m. The profiles clearly show the effects of soil respiration and photosynthetic carbon assimilation, varying both during the diurnal cycle and during the growing season. Profiles of temperature and wind speed are based on a ventilated finewire thermocouple and a hot-wire anemometer, respectively. Measurements over bare soil and a short plant canopy were analyzed in the framework of Monin–Obukhov similarity theory to check the validity of the measurements and raw-data-processing approach. Derived fluxes of \(\hbox {CO}_{2}\), latent and sensible heat and momentum show good agreement with eddy-covariance measurements.     

德州一次沙尘天气过程成因及气溶胶粒子的输送路径分析

利用NCEP 1°×1°再分析资料分析了2017年5月4日浮尘和5月5日扬沙天气的成因。结果表明：3日20时—4日08时,蒙古气旋在有利的环流背景下迅速发展,配合冷锋在内蒙古中部和东部形成大范围的强沙尘天气;4日20时—5日08时沙尘通过高空气流输送到华北地区,在自身沉降和较强下沉气流的共同作用下,迅速沉降形成华北地区大范围的浮尘天气;5日08—14时由于西北路冷空气影响,横槽转竖,冷锋加速南下,将大量沙源地的沙尘输送到德州造成扬沙天气。通过HYSPLIT模式对本次过程中气团后向轨迹的模拟,证实以上两个阶段沙尘天气过程中的输送方式及路径。通过分析影响系统、物理量和气象要素发现,蒙古国、我国内蒙古中部沙源地天气系统强度、位置的变化直接影响沙尘天气的类型,高层气流变化与沙尘天气的类型有很好的对应关系。     

2006—2015年山东短时强降水时空分布特征

利用山东2006—2015年5—9月123个国家级气象观测站10 a逐小时降水量资料,统计分析了山东短时强降水的时空分布特征,结果表明：1）站次时空分布不均。鲁南易出现短时强降水,2013年最多,达到了564站次,7月最多,平均207站次,多出现在傍晚前后和凌晨。2）极值时空分布差异较大。10 a单站极值大值区分布在鲁西北、鲁南和半岛东部,2009年最多,为17站,且多夜间发生;10 a中年度极值均出现在13:00—次日02:00,8月最多,为7次。3）5、6、9月局地和小范围短时强降水天气过程所占比例较大,7—8月大范围短时强降水过程明显增加。