Effect of soil pore size distribution on plant-available water and least limiting water range as soil physical quality indicators

Soil pore size distribution(SPSD) is one of the most important soil physical properties. This research investigated the relationships of location and shape parameters of the SPSD curves with plant-available water(PAW) and least limiting water range(LLWR) of the light-textured soils at the Torogh Agricultural Research Station in north-eastern Iran. Soil moisture release curve(SMRC), PAW and LLWR in matric heads of 100 and 330 h Pa for the field capacity and location and shape parameters of the SPSD curves of 30 soils with different texture and organic carbon contents were determined, and the variable relationships were statistically analyzed. The results showed that the median equivalent pore diameter(de), mean de, standard deviation(SD*), and skewness of the SPSD curves were significantly correlated with PAW(PAW330) and LLWR(LLWR330) measured in a matric head of 330 h Pa. Decrease in deand increase in the diversity of soil pore size(SD*) increased PAW330 and LLWR330. The SD* values of all the soil samples were lower than the optimal ranges suggested in literature. Neither PAW nor LLWR values were significantly different in the soils with the optimal modal deand those with non-optimal modal de. Optimal values of median and mean equivalent pore diameters and kurtosis of SPSD curves led to a significant improvement of PAW330 and LLWR330 as soil physical quality indicators. It was recommended to revise the optimal ranges for SD* and modal defor future studies.     

Intensive organic vegetable production increases soil organic carbon but with a lower carbon conversion efficiency than integrated management

Intensive vegetable production in greenhouses has rapidly expanded in China since the 1990s and increased to 1.3 million ha of farmland by 2016, which is the highest in the world. We conducted an 11‐year greenhouse vegetable production experiment from 2002 to 2013 to observe soil organic carbon (SOC) dynamics under three management systems, i.e., conventional (CON), integrated (ING), and intensive organic (ORG) farming. Soil samples (0–20 and 20–40 cm depth) were collected in 2002 and 2013 and separated into four particle‐size fractions, i.e., coarse sand (> 250 µm), fine sand (250–53 µm), silt (53–2 µm), and clay (< 2 µm). The SOC contents and δ¹³C values of the whole soil and the four particle‐size fractions were analyzed. After 11 years of vegetable farming, ORG and ING significantly increased SOC stocks (0–20 cm) by 4008 ± 36.6 and 2880 ± 365 kg C ha^?1 y^?1, respectively, 8.1‐ and 5.8‐times that of CON (494 ± 42.6 kg C ha^?1 y^?1). The SOC stock increase in ORG at 20–40 cm depth was 245 ± 66.4 kg C ha^?1 y^?1, significantly higher than in ING (66 ± 13.4 kg C ha^?1 y^?1) and CON (109 ± 44.8 kg C ha^?1 y^?1). Analyses of ¹³C revealed a significant increase in newly produced SOC in both soil layers in ORG. However, the carbon conversion efficiency (CE: increased organic carbon in soil divided by organic carbon input) was lower in ORG (14.4%–21.7%) than in ING (18.2%–27.4%). Among the four particle‐sizes in the 0–20 cm layer, the silt fraction exhibited the largest proportion of increase in SOC content (57.8% and 55.4% of the SOC increase in ORG and ING, respectively). A similar trend was detected in the 20–40 cm soil layer. Over all, intensive organic (ORG) vegetable production increases soil organic carbon but with a lower carbon conversion efficiency than integrated (ING) management.     

Realizing the potential of trait‐based approaches to advance fisheries science

Analysing how fish populations and their ecological communities respond to perturbations such as fishing and environmental variation is crucial to fisheries science. Researchers often predict fish population dynamics using species‐level life‐history parameters that are treated as fixed over time, while ignoring the impact of intraspecific variation on ecosystem dynamics. However, there is increasing recognition of the need to include processes operating at ecosystem levels (changes in drivers of productivity) while also accounting for variation over space, time and among individuals. To address similar challenges, community ecologists studying plants, insects and other taxa increasingly measure phenotypic characteristics of individual animals that affect fitness or ecological function (termed “functional traits”). Here, we review the history of trait‐based methods in fish and other taxa, and argue that fisheries science could see benefits by integrating trait‐based approaches within existing fisheries analyses. We argue that measuring and modelling functional traits can improve estimates of population and community dynamics, and rapidly detect responses to fishing and environmental drivers. We support this claim using three concrete examples: how trait‐based approaches could account for time‐varying parameters in population models; improve fisheries management and harvest control rules; and inform size‐based models of marine communities. We then present a step‐by‐step primer for how trait‐based methods could be adapted to complement existing models and analyses in fisheries science. Finally, we call for the creation and expansion of publicly available trait databases to facilitate adapting trait‐based methods in fisheries science, to complement existing public databases of life‐history parameters for marine organisms.     

玉米果穗不同部位子粒水分动态差异研究

为明确玉米果穗不同部位子粒含水率和脱水速率的动态变化差异,在春玉米区宁夏银川和夏玉米区河南新乡采用8个不同熟期和脱水速率的品种,将玉米果穗垂直等分为5个部位,定期测定不同部位子粒含水率,计算子粒脱水速率。结果表明,玉米生长中后期,果穗上部子粒含水率低于中下部子粒含水率,生理成熟前各部位子粒含水率的差值低于生理成熟后。参试品种生理成熟前20 d时不同部位子粒含水率极差低于3%,成熟期的极差值变幅为0.6%～5.2%,生理成熟后极差最大值可达6.2%。同一果穗自上而下子粒的脱水速率逐渐降低,品种之间有明显差异,先玉335、迪卡517和迪卡519果穗不同部位子粒脱水速率差异较大。果穗中部子粒脱水速率和平均脱水速率与不同部位子粒含水率的极差值呈负相关。     

脉冲式烟雾水雾机热力雾化水剂农药效果分析

针对脉冲式烟雾水雾机在喷施水雾剂农药时常出现滴液、流液或较大雾滴群等雾化不良现象，通过改装6HYW-60S型脉冲式烟雾水雾机，将药液流量设置成可调的测试装置，设定5个油门开度及4个药液流量，测试了脉冲发动机喷药前后的气流速度、温度及各喷药工况下的雾滴粒径分布。结果表明，在最小的油门启动开度到最大的油门工作开度可调范围内，对应的脉冲发动机燃油消耗率变化范围较小（相对变化13.0%），喷管内对应的气流温度与速度也发生同等程度的变化。喷药时，喷管口处的气流温度与速度发生明显变化，由不喷药时约700℃的高温气流下降为75℃左右的雾滴流，相应的气流速度下降了16%左右；油门开度及药液流量对雾滴流温度的影响非常小，但对雾滴流速度的影响非常明显，油门开度增大，雾滴流速度明显增加，药液流量增大，雾滴流速度明显下降。在各油门开度下，对最小药液流量20L/h的雾化效果均不佳，尤其距喷雾出口较近处存在大量的300μm以上的较大雾滴，这些大雾滴极易跌落至地面，无法有效喷施到目标物上；药液流量增大至40L/h及以上时，各油门开度下的雾滴体积中径均较小，同一工况下各位置点的平均值不超过60μm。热力雾化的雾滴粒径分布曲线不是单一峰值的正态分布形态，常会出现不同中心雾滴粒径的雾滴群，且这些雾滴群的中心雾滴粒径基本保持一致。从喷雾出口喷出的雾滴流中，喷管中心轴线上的雾滴细小均匀、雾化充分，中心轴线上方的雾滴一般比中心点处稍大，中心轴线下方雾滴明显增大，且距中心轴线越远的下方，雾滴增大越明显，即雾滴流中较大雾滴群的量逐渐增加。以药液流量60L/h及油门开度90°为最佳雾化工况，在整个喷施区域内均形成了良好的雾化效果。     

胶州湾鱼类生物量粒径谱特征

为了解胶州湾海域鱼类群落粒径结构特征,本研究根据2016-2017年4次底拖网调查数据构建了胶州湾鱼类生物量粒径谱,比较分析了各季节鱼类生物量粒径谱特征参数的异质性。结果显示,胶州湾Sheldon型鱼类生物量粒径谱呈现单峰模式,鱼类粒径范围为-3~10粒径级,粒径分布相对均匀,且峰值位于5~6粒径级,主要由大泷六线鱼和褐菖鲉等小型鱼类构成。各季节鱼类标准化生物量粒径谱曲率和曲度差异显著,其中春季曲率最大且曲线较平缓,夏季曲率最小且曲线相对陡峭。谱线曲度和曲率的季节变化主要与粒径小的细纹狮子鱼、大泷六线鱼、玉筋鱼及长丝虾虎鱼等地方常栖性种类和赤鼻棱鳀、白姑鱼等季节洄游性种类的出现有关。Abundance-biomass comparison(ABC)曲线表明,春季处于未干扰状态,冬季处于中度干扰状态,夏秋季处于严重干扰状态。研究表明,胶州湾鱼类群落总体处于严重干扰状态,鱼类生物量谱呈现单峰型,粒径结构以小型粒径鱼类为主,且地方常栖性和季节洄游性鱼类等补充群体的数量和粒径大小影响鱼类生物量粒径谱的峰型和曲率。     

黑斑侧褶蛙变态前后身体大小的变化 及对植物血凝素的反应模式

为了解不同发育阶段黑斑侧褶蛙（Pelophylax nigromaculatus）身体大小和对植物血凝素（Phytohemagglutinin-P，PHA-P）溶液的反应，在室温为（25±2）℃条件下，戈斯纳37、38～39、40～41、42～43、44～45和46期蝌蚪被取样，测定了体重、体长、尾长、体全长和重长比，以及注射PHA-P溶液前（0 h）和注射后3，6，9和12 h被注射部位皮肤组织的增厚程度的变化。不同发育阶段蝌蚪的体重无显著差异（P>0.05），体长、尾长和体全长均随发育进程推进而缩短（P<0.05），但重长比在登陆前后明显增大（P<0.05）。登陆前（37～43期）蝌蚪对PHA-P的反应的峰值出现于注射后3 h（P<0.05），登陆后（44～45期和46期）出现于注射后6 h（P<0.05），但不同发育阶段的最大PHA-P反应无明显的组间差异（P>0.05）。黑斑侧褶蛙登陆后尾部萎缩，重长比明显增加，这些特征有利于提高其对陆生环境的适应性，但对PHA-P的反应的峰值被延迟，这可能是造成蝌蚪登陆后存活率低的主要原因之一。     

Quantitative trait loci for fruit size and flowering time-related traits under domestication and diversifying selection in cucumber (Cucumis sativus)

In cucumber, the genetic basis of traits under domestication and/or diversifying selection is not well understood. Here, we reported QTL mapping for flowering time and fruit size-related traits with segregating populations derived from a cultivated × wild cross. Phenotypic data of flowering time (FT), fruit size (FS), fruit number (FN) and fruit weight per plant (FW) were collected in multiple environments. QTL analysis identified 19 QTL for these traits. We found that the major-effect QTL FT1.1 played an important role in regulating flowering time in cultivated cucumber, whereas the minor-effect QTL FT6.3 contributed to photoperiod sensitive flowering time during domestication. Two novel consensus FS QTL, FS1.4 and FS2.3, seem to be the targets of selection during breeding for the US processing cucumber. All other FS QTL were co-localized with previously detected QTL using populations derived from cultivated cucumbers, suggesting that they were under selection during both initial domestication and subsequent improvement. Results from this study also suggested that the wild cucumber is a useful resource for capturing positive transgressive segregation and novel alleles that could be explored in cucumber breeding.