Can additional N fertiliser ameliorate the elevated CO2‐induced depression in grain and tissue N concentrations of wheat on a high soil N background?

Elevated CO₂ stimulates crop yields but leads to lower tissue and grain nitrogen concentrations [N], raising concerns about grain quality in cereals. To test whether N fertiliser application above optimum growth requirements can alleviate the decline in tissue [N], wheat was grown in a Free Air CO₂ Enrichment facility in a low‐rainfall cropping system on high soil N. Crops were grown with and without addition of 50–60 kg N/ha in 12 growing environments created by supplemental irrigation and two sowing dates over 3 years. Elevated CO₂ increased yield and biomass (on average by 25%) and decreased biomass [N] (3%–9%) and grain [N] (5%). Nitrogen uptake was greater (20%) in crops grown under elevated CO₂. Additional N supply had no effect on yield and biomass, confirming high soil N. Small increases in [N] with N addition were insufficient to offset declines in grain [N] under elevated CO₂. Instead, N application increased the [N] in straw and decreased N harvest index. The results suggest that conventional addition of N does not mitigate grain [N] depression under elevated CO₂, and lend support to hypotheses that link decreases in crop [N] with biochemical limitations rather than N supply.     

Soil enzyme activities during the 2011 Texas record drought/heat wave and implications to biogeochemical cycling and organic matter dynamics

Extreme droughts and heat waves due to climate change may have permanent consequences on soil quality and functioning in agroecosystems. During November 2010 to August 2011, the Southern High Plains (SHP) region of Texas, U.S., a large cotton producing area, received only 39.6 mm of precipitation (vs. the historical avg. of 373 mm) and experienced the hottest summer since record keeping began in 1911. Several enzyme activities (EAs) important in biogeochemical cycling were evaluated in two soils (a loam and a sandy loam at 0–10 cm) with a management history of monoculture (continuous cotton) or rotation (cotton and sorghum or millet). Samplings occurred under the most extreme drought and heat conditions (July 2011), after precipitation resulted in a reduction in a drought severity index (March 2012), and 12 months after the initial sampling (July 2012; loam only). Eight out of ten EAs, were significantly higher in July 2011 compared to March 2012 for some combinations of soil type and management history. Among these eight EAs, enzymes key to C (β-glucosidase, β-glucosaminidase) and P cycling (phosphodiesterase, acid and alkaline phosphatases) were significantly higher (19–79%) in July 2011 than in March 2012 for both management histories regardless of the soil type (P > 0.05). When comparing all sampling times, the activities of alkaline phosphatase, aspartase and urease (rotation only) showed this trend: July 2011 > March 2012 > July 2012. Activities of phosphodiesterase, acid phosphatase, α-galactosidase, β-glucosidase and β-glucosaminidase were higher in July 2011 than July 2012 in at least one of the two management histories. Total C was reduced significantly from July 2011 to March 2012 in the rotation for both soils. Only the activities of arylsulfatase (avg. 36%) and asparaginase showed an increase from July 2011 to March 2012 for both soil types, which may indicate they have a different origin/location than the other enzymes. EAs continued to be a fingerprint of the soil management history (i.e., higher EAs in the rotation than in monoculture) during the drought/heat wave. This study provided some of the first evidence of the adverse effects of a natural, extreme drought and heat wave on soil quality in agroecosystems as indicated by EAs involved in biogeochemical cycling.     

1958—2018年广西早稻高温热害时空变化规律

为了掌握广西水稻高温热害的变化规律特征,为水稻生产制定防灾减灾对策提供决策依据,本研究利用广西89个气象观测站1958—2018年观测资料及地理信息数据,采用GIS技术、M-K突变分析和Morlet小波周期分析等方法,探究广西早稻高温热害发生的时间变化规律和空间分布等特征。结果表明：（1）1958—2018年广西早稻高温热害呈增长趋势,20世纪90年代为发生低谷期,21世纪10年代为高发期;（2）高温热害发生次数在2009年发生增多突变,除重度高温热害外,轻、中度高温热害次数变化均有突变发生;（3）高温热害发生频次存在18、32年左右的显著周期变化,预计2018年之后广西早稻高温热害仍处于高发期;（4）高温热害高发区位于左、右江河谷,桂中盆地和西江—浔江—郁江等流域区域,沿海地区发生频次少于内陆。以上研究结论对实现水稻丰产稳产优产具有重要的现实意义。     

基于GODAS资料的南海上层海洋热状态气候变化特征分析

为了深入了解南海上层海洋热力状态的变化规律,利用1980—2015年共36年GODAS月平均海温资料,将5~366 m的垂直平均海温表征南海地区海洋上层的热含量,分析了南海海洋上层热状态的水平和垂直分布特征以及季节和年际变化特征。结果表明：年平均南海热含量水平分布表现为东高西低的形势,垂直纬向平均分布表现为暖水厚度和温跃层深度东厚（深）西薄（浅）,垂直经向平均表现为暖水厚度南厚北薄,温跃层深度中间浅两边深;南海地区海温变化幅度在75~200 m处最大,不同深度海温距平均具有明显的年际和年代际变化特征;南海区域平均热含量在秋季最高,春夏次之,冬季最低,其年际变化明显,且在1998年之后出现明显的突变,由负值转变为正值,表现出明显的增温趋势;热含量季节EOF主模态空间分布形势表现为东高西低的特征,对应的时间序列在20世纪90年代末存在年代际转折,由主要为负值转化为主要为正值,表现在空间分布上,则为南海地区热含量由西高东低型转化为东高西低型。     

鹅肠道微生物研究进展

肠道微生物是当前研究的热点,鹅肠道微生物的组成与丰富程度不仅和鹅的生长性能密切相关,而且在鹅机体生理活动中具有一定的调节作用,同时与疾病的发生和发展具有密切的联系。通过研究鹅肠道微生物的调节,从而达到促生长或者治疗疾病的目的,是目前鹅研究探寻的新方向。文章主要综述了鹅肠道微生物的组成及其变化规律,以期为鹅产业生物饲料的开发应用、研发推广新型安全高效饲料添加剂提供新思路。     

1971—2016年河南省夏玉米生长季极端干旱时空特征

选用地表湿润指数，利用1971—2016年气象数据对河南省夏季极端干旱发生的时空特征进行了分析。结果表明：近46 a来，河南省夏季极端干旱发生频数在年均0.08～2.15月之间，总体上呈现微弱的下降趋势。6月和9月极端干旱发生次数高于7月和8月。1970s发生频数最多，2000s最少，2010s呈现回升的趋势。6月和9月极端干旱发生站次百分比明显高于7月和8月，且6、7月和9月的发生站次百分比在2010s也呈现回升趋势。各年代平均发生频数均以豫南地区最高，近46 a来极端干旱总次数呈现由南向北逐渐递减的分布特征，但6月份发生总次数高值区则主要分布在豫中和豫西地区。全省范围内极端干旱发生存在明显的4~8 a周期变化，2010s极端干旱发生频数和站次百分比均呈回升趋势，应引起夏玉米生产上的关注和重视。     

Abrupt temperature change and a warming hiatus from 1951 to 2014 in Inner Mongolia,China

An abrupt temperature change and a warming hiatus have strongly influenced the global climate.This study focused on these changes in Inner Mongolia, China. This study used the central clustering method, Mann-Kendall mutation test and other methods to explore the abrupt temperature change and warming hiatus in three different temperature zones of the study region based on average annual data series.Among the temperature metrics investigated, average minimum temperature(Tnav) shifted the earliest,followed by average temperature(Tnv) and average maximum temperature(Txav). The latest change was observed in summer(1990 s), whereas the earliest was observed in winter(1970 s). Before and after the abrupt temperature change, Tnav fluctuated considerably, whereas there was only a slight change in Txav.Before and after the abrupt temperature change, the winter temperature changed more dramatically than the summer temperature. Before the abrupt temperature change, Tnav in the central region(0.322°C/10 a)and west region(0.48°C/10 a) contributed the most to the increasing temperatures. After the abrupt temperature change, Tnav in winter in the central region(0.519°C/10 a) and in autumn in the west region(0.729°C/10 a) contributed the most to the temperature increases. Overall, in the years in which temperature shifts occurred early, a warming hiatus also appeared early. The three temperature metrics in spring(1991)in the east region were the first to exhibit a warming hiatus. In the east region, Txav displayed the lowest rate of increase(0.412°C/a) in the period after the abrupt temperature change and before the warming hiatus,and the highest rate of increase after the warming hiatus.     

石灰岩山地4种林分空气细菌动态变化及其影响因素分析

为探索石灰岩山地不同林分类型中空气细菌的动态变化规律及其影响因素,筛选出抑菌效果较好的林分,选取徐州石灰岩山地4种典型林分为试验材料,采用自然沉降法研究林分中细菌含量的季节变化和日变化,同步监测温湿度、风速、PM2.5和空气负离子浓度,分析空气细菌含量及其之间的关系。试验结果表明:(1)细菌含量季节性变化表现为春季秋季夏季冬季,除冬季日变化呈现"早晚低,中午高"的变化趋势,其他季节表现为"早晚高,中午低";(2)不同林分类型空气细菌含量存在显著差异(P0.05),总体来看,苦楝林对细菌的抑制效果最好;(3)细菌含量与空气湿度和PM2.5呈极显著正相关关系,与空气负离子呈极显著的负相关关系。综上,苦楝林的抑菌效果最好,湿度、PM2.5和负离子是影响空气细菌含量的主要因素。本研究可为此地城市保健林的营建以及生态旅游规划提供科学依据。     

基于无人机多光谱遥感的冬小麦叶绿素含量反演及监测

旨在实现冬小麦各生育期叶绿素含量的准确估测,探究其时空变化规律。利用无人机获取冬小麦越冬期、返青期、拔节期、孕穗期和灌浆期的高分辨率多光谱图像,同时采集地面SPAD数据。选取三类光谱参数建立反演模型,优选出各生育期的最佳预测模型,并定量监测试验区冬小麦叶绿素含量时间变化和空间分布。结果表明：原始波段模型和波段倒数对数模型分别为越冬期及其他生育期叶绿素含量预测的最佳模型,拟合精度R²>0.59;时空分布上,灌浆期前试验区冬小麦叶绿素含量呈南北高、中部低特点,灌浆期则呈北高南低的趋势,叶绿素含量从越冬期到拔节期逐步增加,拔节期到孕穗期开始降低,孕穗期到灌浆期则大幅度降低。本研究建立的倒数对数预测模型,精度较高,且适用于返青到灌浆的4个生育期,对于试验区冬小麦叶绿素含量有较好的时空监测效果。