The nearest-plant method is robust and powerful enough for different survey teams to monitor change in mesic grassland species composition

A long-term rangeland monitoring programme needs to employ a field survey technique that is practicable, precise, powerful enough to distinguish change, not prone to worker bias, and able to distinguish real change from operator error arising from staff turnover. These criteria were used to evaluate a widely used grassland sampling technique in South Africa – the nearest-plant (with 200 points) method (NP) – against common alternatives, namely NP excluding forbs (NP-nf), the plant number scale (PNS; a cover-abundance method) and quadrat frequency (QF), using multivariate ordination and permutation tests. Four trained teams surveyed four grasslands using each method. PNS took more than twice as long as the other techniques, which were similarly rapid. Estimates of composition using NP methods were the most precise and PNS was least repeatable, with QF intermediate. Compositional differences between sites were most finely distinguished using NP-nf, followed by NP and QF. PNS was able to detect only marked differences and had the greatest potential for surveyor bias. The NP method, with or without including forbs, is therefore recommended for monitoring the species composition of mesic, dense grassland. Some suggestions for monitoring agencies on how best to use multivariate methods are presented.     

Temporal associations between low body condition,lameness and milk yield in a UK dairy herd

Previous work has hypothesised that cows in low body condition become lame. We tested this in a prospective longitudinal study. Body condition score (BCS), causes of lameness and milk yield were collected from a 600-cow herd over 44-months. Mixed effect binomial models and a continuous outcome model were used to investigate the associations between lameness, BCS and milk yield. In total, 14,320 risk periods were obtained from 1137 cows. There were 1510 lameness treatments: the most common causes of lameness were sole ulcer (SU) (39%), sole haemorrhage (SH) (13%), digital dermatitis (DD) (10%) and white line disease (WLD) (8%). These varied by year and year quarter. Body condition was scored at 60-day intervals. BCS ranged from 1 to 5 with a mean of 2.5, scores were higher in very early lactation but varied widely throughout lactation; approximately 45% of scores were <2.5. The key finding was that BCS < 2.5 was associated with an increased risk of treatment for lameness in the following 0–2 months and >2–4 months for all causes of lameness and also specifically for SU/WLD lameness. BCS < 2.5 was associated with an increased risk of treatment for SH in the following 0–2 months but not >2–4 months. There was no such association with DD. All lameness, SU/WLD, SH and DD were significantly more likely to occur in cows that had been lame previously, but the effect of BCS was present even when all repeat cases of lameness were excluded from the analysis. Milk yield was significantly higher and fell in the month before treatment in cows lame with SU/WLD but it was not significantly higher for cows that were treated for DD compared with non-lame cows. These findings support the hypothesis that low BCS contributes to the development of horn related claw lameness but not infectious claw diseases in dairy cows. One link between low BCS and lameness is a thin digital cushion which has been proposed as a trigger for claw horn disease. Cows with BCS 2 produced more milk than cows with BCS 2.5, however, this was only approximately 100 kg difference in yield over a 305-day lactation. Given the increased risk of lameness in cows with BCS 2, the direct costs of lameness and the small variability in milk yield by BCS, preventing cows from falling to BCS < 2.5 would improve cow welfare and be economically beneficial.     

逆出蚕发生的原因及孵化方式的初步研究

针对生产上出现"逆出蚕"这一情况,通过催青实验调查发生逆出蚕的原因及其孵化方式.实验采用碧波×洞庭、春蕾×镇珠2个蚕品种,分别在常温、高温与RH 70%、 RH 80%、 RH 90%组合的6个条件下,进行两段式催青至孵化.通过对孵化率、逆出蚕率的调查,发现影响同一品种逆出蚕的主要原因是湿度,实验还观察到了逆出蚕的孵化方式.这些为今后进一步研究逆出蚕和减少逆出蚕的发生有着积极作用和现实意义.     

四川麻疯树适宜栽培区划

通过对四川麻疯树生态适生条件需求的分析,提出了四川麻疯树适宜、次适宜区域,并通过立地条件选择提出了四川麻疯树栽植适生区.     

气吸辊式水稻精量直播排种器的设计与试验研究

针对我国现有水稻精量直播排种器对种子适应性差、伤种率高、排种速度低等问题,设计气吸辊式水稻精量直播排种器,并进行种子吸附条件分析,确定影响工作性能的参数;完成了参数的单因素试验和正交试验研究。结果表明:所设计的排种器能够满足水稻芽种的精量穴播和低伤芽率的要求;吸种针孔径与排种器吸种性能影响呈正相关趋势,吸种针孔径选择应大于0.60mm;影响排种器播种性能的因素主次顺序依次为吸种针孔径、吸种真空度、吸种辊转速,当吸种针孔径为1.55mm、吸种真空度为0.035MPa、吸种辊转速为50r/min时播种效果较好,吸种合格率为98%。     

张掖制种玉米生长期气候条件分析及气候品质认证

本文研究张掖制种玉米关键生长阶段气象因子适宜指标,确定影响品质的主要气候条件及关键因素,探讨了张掖制种玉米气候品质认证技术.利用张掖国家基准气候站气温、降水、日照等气象资料,分析2020年热量、光照、降水气候条件及诸因子对制种玉米主要生长期的影响,最终对张掖制种玉米进行气候品质等级认证分析评估.结果 表明,2020年研...     

犬传染性肝炎病毒Hexon基因原核表达条件的优化与表达蛋白的活性

[目的]为了提高犬传染性肝炎Hexon蛋白基因在大肠杆菌中的表达量,研究Hexon基因蛋白的最佳表达条件和表达蛋白的活性.[方法]在大肠杆菌菌株BL21(DE3)培养过程中,选择诱导剂(IPTG)的最佳加入时间、诱导剂(IFTG)浓度、诱导时间以及不同温度条件观察对Hexon融合蛋白表达的影响,以确定最佳表达条件,并用Westem-blot检测重组蛋白的生物活性.[结果]大肠杆菌BL21(DE3)在37℃培养2.25h后,添加终浓度为2.0 mmol/L的IPTG,27℃培养8 h,Hexon重组蛋白表达量最高(1.67mg/mL),所表达的重组蛋白能与犬传染性肝炎阳性血清相结合.[结论]在高浓度IPTG诱导和冷培养条件下,Hexon蛋白基因的表达量最高,表达出的重组蛋白具有很好的反应原性,为进一步研究六邻体蛋白的作用机理及亚单位疫苗的研究提供了实验基础.     

三明格氏栲自然保护区土壤条件和肥力状况的研究

研究表明 ,天然格氏栲林下土壤的质地大都为重壤土至轻粘土 ,其土壤的全氮、有机质及速效养分含量都明显高于其他林分的土壤。天然格氏栲林下土壤进入红壤土壤成土过程的最高阶段 ,形成具有较高肥力的土壤     

培养条件对奶牛金葡菌5型荚膜多糖产量的影响

[目的]研究不同培养条件对牛源金葡菌5型荚膜多糖产量的影响,以便于CP5的生产制备,从而为开展奶牛金葡菌新型多糖疫苗的研究奠定基础。[方法]从患隐性乳腺炎奶牛乳样中分离金葡菌,鉴定荚膜多糖血清型,对5型荚膜多糖菌株,采用BHI,哥伦比亚固体培养基,mod110三种培养基,每种培养基分别采用固体培养,碳源为葡萄糖的液体培养和碳源为乳糖的液体培养三种方式,共组成9种不同培养条件进行培养,研究培养条件对金葡菌荚膜多糖产量的影响。[结果]不同培养结果表明,与常用哥伦比亚培养基比较,BHI培养基能降低荚膜多糖产量,而mod110培养基能提高荚膜多糖产量;同种培养基,固体培养方式比液体培养方式有更高的荚膜多糖产量,同时乳糖作为碳源可提高荚膜多糖产量。     

Differences in Organic C Mineralization Between Aerobic and Submerged Conditions in Paddy Soils of Southern Jiangsu Province, China

Moisture regime plays a crucial role in the mineralization of soil organic carbon (SOC). In this paper, the dynamics of SOC mineralization in typical paddy soils of Changshu, Jiangsu Province, China, was investigated by incubation test in laboratory. The differences in SOC mineralization under aerobic and submerged conditions of paddy soils were also studied. Results showed that the daily mineralization of SOC under different moisture regimes was significantly different in the whole incubation period, at the beginning of the incubation, it decreased quickly under aerobic condition, but increased rapidly under submerged condition, and both remained constant after 10 d of incubation. The differences in SOC mineralization were found to be mainly at the beginning period of the incubation and decreased along with the incubation time. Thus, the difference was not significantly different at the later incubation period. The respiration intensity, daily and cumulative mineralization of SOC under aerobic condition was 2.26–19.11, 0.96–2.41, and 0.96–2.41 times than those under submerged condition, respectively. Statistic analyses showed that the higher the contents of microbial biomass carbon and nitrogen, the more significant difference in respiration intensity between aerobic and submerged conditions, but the higher the contents of microbial biomass nitrogen and dissolved organic carbon, the more significant difference in daily mineralization of SOC between the two conditions. The decrease in soil microbial activity under submerged condition was the main reason leading to the decrease in respiration intensity, but the decrease in SOC mineralization was also correlated with the changes in dissolved organic carbon over the whole incubation period.