孔隙结构图像分析中不同试验因素对分析结果的影响

研究了不同试验因素 (包括图像分辨率、土壤切片定向性、分析区域大小等 )对孔隙结构图像分析结果的影响以及试验误差 ,并简要介绍了用于分析土壤孔隙结构的土壤切片及数字图像的制备技术。结果表明 :不同试验因素对分析结果均会产生一定的影响 ,试验误差约在 1 0 %。这表明同一研究中应保持试验条件的相对一致以保证分析结果的可靠性和可比性     

动物毛发的形态结构及其功能特性研究

对人发及其他14种动物毛发的扫描电镜(SEM)照片进行分析,根据它们形态结构特征将其分为指状结构、芽状结构、鳞状结构和波状结构4类,并就每种毛发结构的保温性、疏水性及其柔性进行了比较分析。分析结果表明,具有指状细观结构形态的毛发在保温性、疏水性及柔韧性方面具有明显优势,这一信息对研究开发新型功能材料具有借鉴作用     

延安飞马河试验示范区农业生产的调查研究

在考察和调查的基础上 ,对陕西省延安市郊飞马河农果复合生态农业试验示范区的农业气候、土壤和水等自然资源和社会经济情况 ,农业生产中存在问题与农田种植结构布局特点 ,农业生产技术应用 ,以及农业发展方向进行分析研究 ,为促进该地区农业生产进一步发展提供参考     

商州市川垣河谷区生态农业建设初探

根据商州市川垣河谷区的自然条件、社会经济状况和生产发展限制因素,提出该区若能加强水平梯田建设,积极调整种植业、养殖业结构,发展高效设施生态农业,加强核桃、柿子、花椒和中草药、食用菌的生产,封山育林,植树种草等,则该区一定会变成山青、水秀、民富的生态经济型现代新农村。     

土壤微生物群落结构对凋落物组成变化的响应

凋落物分解是陆地生态系统养分循环的关键过程,明确凋落物多样性如何影响土壤微生物群落构成和多度,继而潜在地改变凋落物分解的微生物学机制有助于认识生物多样性和森林生态系统功能的关系。通过小盆模拟试验,应用磷脂脂肪酸谱图的方法研究了我国南方红壤丘陵区典型物种马尾松和湿地松的凋落物分别与白栎和青冈的凋落物混合,与单一针叶凋落物分解时相比,针阔混合凋落物分解过程中土壤微生物群落结构的变化,结果显示:(1)针阔混合凋落物分解时土壤微生物群落磷脂脂肪酸(Phospholipidfatty acids,PLFA)总量低于单一针叶处理,细菌和放线菌的相对多度高于单一针叶处理,真菌则相反,群落真菌/细菌低于单一针叶处理,土壤微生物生物量的差异主要来自于真菌;(2)主成分分析表明:针阔混合凋落物分解与单一针叶凋落物分解的土壤微生物群落结构差异显著,两个时期(分解9个月和18个月)主成分一分别可以解释65.74%和89.63%的变异,第一主成分主要包括18∶2ω6,9、18∶1ω9c、17∶0和10Me18∶0等磷脂脂肪酸;(3)土壤微生物群落结构受凋落物初始C/N和木质素/N调控,土壤微生物群落细菌的相对多度与凋落物初始C/N和木质素/N显著负相关,真菌则与凋落物初始C/N和木质素/N显著正相关,群落真菌/细菌与凋落物初始C/N和木质素/N显著正相关。针阔凋落物混合分解通过改变凋落物C/N和木质素/N,提供了对分解者更为有利的微环境。     

2BCM-6型茬地免耕半精量播种机的研制

根据新疆气候特征，种植业特点，土壤特性，设计研制了2BCM一6型茬地免耕半精量播种机。主要介绍了工作部件的设计、工作原理、技术指标等。2BCM—6型茬地免耕半精量播种机通过性能实验，达到了设计要求。     

温度对棉纤维强度及超分子结构的影响

利用短季棉中棉所16号品种, 研究了温度对棉纤维断裂比强度与超分子结构的影响, 结果 表明： 纤维断裂比强度随铃龄增大而升高; 相同铃龄随温度下降断裂比强度降低。 较高 温度条件下α角随铃龄增大不断宽化(变大), 对纤维强度提高不利; 较低温度条件下α角 随纤维发育不断变小(优化), 某种程度上有利于纤维强度提高;     

Indirect regulation of heterotrophic peat soil respiration by water level via microbial community structure and temperature sensitivity

Northern peatlands contain a considerable share of the terrestrial carbon (C) pool, which climate change will likely affect in the future. The magnitude of this effect, however, remains uncertain, due mainly to difficulties in predicting decomposition rates in the old peat layers. We studied the effects of water level depth (WL) and soil temperature on heterotrophic soil respiration originating from peat decomposition (R_PD) in six drained peatlands using a chamber technique. The microbial community structure was determined through PLFA. Within the studied sites, temperature appeared to be the main driver of R_PD. However, our results indicate that there exist mechanisms related to lower WL conditions that can tone down the effect of temperature on R_PD. These mechanisms were described with a mathematical model that included the optimum WL response of R_PD and the effect of average WL conditions on the temperature sensitivity of R_PD. The following implications were apparent from the model parameterisation: (1) The instantaneous effect of WL on R_PD followed a Gaussian form; the optimum WL for R_PD was 61 cm. The tolerance of R_PD to the WL, however, was rather broad, indicating that the overall effect of WL was relatively weak. (2) The temperature sensitivity of R_PD depended on the average WL of the plot: plots with a high average WL showed higher temperature sensitivity than did those under drier conditions. This variation in temperature sensitivity of R_PD correlated with microbial community structure. Thus, moisture stress in the surface peat layer or, alternatively, the lowered temperature sensitivity of R_PD in low water level conditions via microbial community structure and biomass may restrict R_PD. We conclude that a warmer future climate may raise R_PD in drained peatlands only if the subsequent decrease in the moisture of the surface peat layers is minor and, thus, conditions remain favourable for decomposition.     

陕北黄土区山杏林下草本层植物群落特征研究

根据陕西省吴起县不同立地类型25龄以上山杏人工纯林和山杏沙棘混交林林下草本层植被调查数据,采用时空互代的方法,探讨了在不同立地山杏林下草本层植物群落演替方向及其生态恢复效果.结果表明,阴向缓坡、阴向陡坡和阳向缓坡山杏纯林下草本层由铁杆蒿、达乌里胡枝子群落演替到大披针苔草或铁杆蒿、大披针苔草群落,群落整体由旱生型向中生型转变,盖度和生物量增大,多样性略有降低,呈正向演替;且山杏-沙棘混交林下草本层上述指标均优于纯林.而在阳向缓坡山杏林下由星毛委陵菜、铁杆蒿群落演替到甘草、大披针苔草群落,群落整体向旱生型转变,多样性、盖度、生物量均随林龄增加显著降低,呈逆行演替.建议在阴向缓坡、阴向陡坡及阳向缓坡配置山杏这类低耗水,生长慢乔木树种,其中与沙棘等乡土灌木树种混交的模式更优;在阳向陡坡以营造生长速度适中的灌木林或自然恢复草地植被为宜.     

基于SNP和InDel标记的巴西木薯遗传多样性与群体遗传结构分析

As a typical tropical crop, cassava (Manihot esculenta Crantz) has the characteristics of drought resistance, barren resistance, high biomass and so on. In addition to being used for food and forage, it can also be used for production, processing and starch extraction. Due to highly heterozygous cassava genome, breeding is more difficult. Enriching the genetic diversity of cassava germplasm, comprehensively evaluating its genetic background and traits, and discovering superior alleles that control excellent traits are of great significance for cassava breeding in the future. In order to analyze the genetic diversity, genetic relationship and population structure of cassava germplasm in Brazil, 7946 SNPs and 1997 InDels molecular markers were used. Population structure analysis was performed by ADMIXTURE software, and principal component analysis was performed by GCTA software. Brazilian cassava was divided into nine subgroups, and was roughly consistent with the results of cluster analysis using PHYLIP. Among them, subgroup 1, subgroup 2, subgroup 4, subgroup 6, and subgroup 8 could be clustered together respectively, while the samples of other subgroups could be roughly clustered, and there was a certain cross between the samples. The genetic diversity of cassava germplasm in Brazil (0.274) was higher than the genetic diversity level of cassava germplasm in China and Nigeria. Subgroup 5 of Brazil cassava had a relatively high genetic diversity (0.29). The genetic differentiation of subgroups was low (the genetic differentiation vary from 0.03 to 0.15), but higher than domestic cassava germplasm. The genetic distance between cassava accessions varied from 0.084 to 0.297, with the average of 0.228. The results of this study can provide a basis for subsequent association analysis to identify great alleles and introduction.