川北地形过渡带地形因子对土地利用与景观格局变化的影响

[目的]基于地形特征分析不同用地类型时空分布变化,不仅能解释土地利用时空变化规律,并能更进一步为优化土地利用结果,生态环境保护奠定基础。[方法]基于四川省北部江油市2003,2010,2018年3期遥感影像,运用土地利用转移矩阵法,分析不同用地类型之间的转化情况;接着利用地形位指数法、分布指数法,分析地形因子影响下不同用地类型分布指数变化特征;之后利用移动窗口法,探究景观格局中斑块密度与Shannon多样性指数时空变化规律;最后结合双变量空间相关性分析,分析地形因子与景观指数间的空间相关性特征。[结果](1)在2003—2010年期间,水田面积减少最多(减少面积2 238.98 hm~2),建设用地面积增加最多(面积增加3 360.36 hm~2);在2010—2018年期间,水田面积减少1 175.84 hm~2,建设用地面积增加1 614.78 hm~2;2003—2010年期间江油市土地利用的变化量整体高于2010—2018年。(2)北部山区主要由旱地转移为林草地,南部平原地区主要为水田转移为建设用地,中部丘陵区域旱地和水田相互转化强烈。(3)随时间变化,旱地和未利用地优势等级向中地形位等级靠拢;低地形位等级上建设用地、水田和水域优势度逐渐降低,并具有优势等级向较高地形位等级扩展趋势。(4)山区河流沿岸以及山地平原交汇处斑块密度与Shannon多样性指数较高,且呈线性分布;随时间变化,丘陵区域斑块密度增加,主城区附近Shannon多样性指数呈下降趋势。(5)高—高聚集区主要表现为向山地丘陵交汇处聚集;城区附近景观指数因受其他因素影响较多,导致该区域景观指数与地形位指数呈现出不显著相关性。[结论]在地形过渡带区域,不同地貌对于各类用地变化的影响在时空上存在差异性,其地形因子与景观指数的空间相关性差异明显。     

2005-2018年澜沧江下游流域景观生态安全时空变化及其驱动因素

[目的] 分析澜沧江下游流域景观生态安全时空变化规律和驱动机制，为该流域及流经国家的人与自然协调可持续发展提供科学依据。[方法] 以2005，2010，2015和2018年4期遥感影像为数据源，通过景观指数和GIS空间分析方法评价流域景观生态安全，采用双变量空间自相关方法明确城市、道路、河流、高程、坡度、气温和降水等因素对景观生态安全的驱动作用。[结果] ①2005—2018年，澜沧江下游流域的整体景观生态安全度呈先升后降的变化特征。其中，北部和中西部景观生态安全较差，东部、南部和东南部较好，但也有恶化趋势；②各景观类型中，景观生态安全度从大到小为：水域 > 林地 > 草地 > 耕地 > 建设用地 > 裸地。其中，林地和草地的景观生态安全度存在波动，耕地和水域的景观生态安全度一直上升，而建设用地和裸地的景观生态安全度持续下降；③距城市距离、距道路距离、气温和降水等社会和气象因素对景观生态安全时空变化的驱动作用最强，距河流距离也对景观生态安全的时空变化有一定解释作用，而高程和坡度等地形因素并非澜沧江下游流域景观生态安全时空变化的主要驱动因素。[结论] 应尽量降低由人类活动引起的生态环境负荷，积极发挥气象因素对生态安全的正向效应，促进澜沧江下游流域的人与自然协调可持续发展。     

草地贪夜蛾寄生蜂资源及其调控寄主免疫反应的研究

草地贪夜蛾Spodoptera frugiperda（J.E.Smith）原产于美洲，自2019年初入侵我国以来迅速向北蔓延，对农业造成了巨大损失。其寄生蜂作为重要的天敌资源之一，在害虫防治中具有不可替代的作用。本文对目前已鉴定到的9个科170种草地贪夜蛾寄生蜂天敌等进行了分类总结，而后讨论了其在害虫生物防治方面的应用前景，并围绕草地贪夜蛾寄生蜂寄生因子调控寄主免疫反应的分子机理展开详细论述。该研究旨在丰富草地贪夜蛾的生物防治资源素材，并为该害虫的绿色防控提供重要的理论与实践指导意义。     

库姆塔格沙漠东南部胡杨液流变化及其对环境因子的响应

于2018年4月?10月(春季4月、夏季7月、秋季9月)利用PS-TDP8树木茎流监测系统对库姆塔格沙漠东南部胡杨(Populus euphratica)的液流速率变化进行监测,采用相关分析及逐步回归法分析气象因子(太阳总辐射、空气温度、风速、空气相对湿度)对胡杨液流的影响。结果表明:胡杨茎干液流日变化趋势呈几字“宽峰型”;夏季液流的启动时间最早,液流启动在06:00,秋季液流启动时间最晚,不同季节夜间存在较高液流(10.994~26.035 cm·h^?1);树干液流速率与太阳总辐射、空气温度、风速、饱和水气压差呈正相关关系,与空气湿度呈负相关关系;影响春季、秋季胡杨液流速率的主要气象因子是太阳总辐射和空气温度,夏季为太阳总辐射和空气相对湿度;不同季节胡杨液流速率与空气温度、空气相对湿度、风速、饱和水气压差的日变化响应呈顺时针环状,与太阳辐射响应呈逆时针环状;不同季节胡杨液流速率对气象因子的响应规律存在差异。这表明胡杨为了保持水分平衡应对水分亏缺的策略不同,在一定条件下(极端干旱)通过气孔调节降低水分损失。研究结果对于明确干旱沙漠环境中胡杨水分传输对环境因子的响应规律及更深入地认识胡杨适应干旱环境的水分利用策略具有重要意义。     

Partial fishmeal replacement by mussel meal or meat and bone meal in low‐fishmeal diets for juvenile Ussuri catfish (Pseudobagrus ussuriensis): Growth,digestibility, antioxidant capacity and IGF‐I gene expression

This study evaluated the effects of replacing fishmeal with mussel meal or meat and bone meal in low‐FM diet on growth performance, body composition, digestibility, antioxidant capacity and IGF‐I gene expression in juvenile Ussuri catfish (Pseudobagrus ussuriensis). The results showed that no significant changes in SGR, FE and PER were observed between MM₄₀ and LFM groups, but significantly reduced result was found in MBM₄₀ group. MM₄₀ group showed the higher ADC of lipid (93.30%) and lipase activity (95.00 U/gprot) than LFM group (90.97%; 70.18 U/gprot). MM₄₀ or MBM₄₀ diets led to significant reduction of SOD and CAT activities. MM₄₀ group showed significantly higher MDA level (5.84 nmol/mg) than LFM group (4.73 nmol/mg). The activities of LZM decreased significantly in MM₄₀ and MBM₄₀ groups compared with LFM group. MM₄₀ and MBM₄₀ groups showed no significant difference in hepatic IGF‐I gene expression levels compared with LFM group. The findings demonstrated that MM could substitute 400 g/kg of FM in low‐FM diet for Ussuri catfish without influencing the growth, but to some extent, spontaneous oxidative stress and immune damage could occur; when 400 g/kg of FM was replaced by MBM, significantly negative effects were observed on growth, antioxidant capacity and non‐specific immune response of Ussuri catfish.     

Karanj protein isolate prepared from karanj seed cake: Effect on growth,body composition and physiometabolic responses in Labeo rohita fingerlings

A protein isolate was prepared from karanj seed (KPI) with 921.2 g protein/kg seed, which contained a negligible amount of anti‐nutritional factors and a balanced amino acid composition, especially rich in methionine. For 60‐day feeding trial, five isonitrogenous (300 g/kg CP) and isocaloric (15 MJ DE/kg) diets were formulated by replacing soybean protein isolate (SPI) on protein equivalent basis, KPI‐0 (control, 0 g/kg KPI); KPI‐25 (replacing 250 g/kg SPI protein with KPI); KPI‐50 (replacing 500 g/kg SPI protein with KPI); KPI‐75 (replacing 750 g/kg SPI protein with KPI) and KPI‐100 (replacing 1,000 g/kg SPI protein with KPI) for the feeding of L. rohita. The weight gain percentage, specific growth rate, feed conversion ratio and protein efficiency ratio were not significantly (p > .05) varied among the KPI fed and control groups. A significantly higher hepatosomatic index was recorded in the control and KPI‐25 groups compared with other groups. The whole‐body compositions, except ether extract, did not differ significantly (p > .05) among the groups. Digestive (amylase, protease, lipase and alkaline phosphatase) and metabolic enzyme activities (hexokinase, transaminases and lactate dehydrogenase) and glycogen stores were not significantly affected, whereas intestinal alkaline phosphatase differed significantly (p < .05). The RNA–DNA ratio was significantly (p < .05) higher in the KPI‐75 group. Thus, the study revealed that KPI can completely replace SPI protein at 191 g/kg inclusion level in the diets of L. rohita fingerlings.     

Effects of alternative dietary lipid sources on growth performance,health status and fillet fatty acid composition of hybrid sturgeon (Acipenser baeri Brandt ♀ × Acipenser schrenckii Brandt ♂)

An 8‐week trial was conducted to determine the effects of total replacement of 12.9% fish oil (FO) with soybean oil (SBO), peanut oil (PNO), sunflower seed oil (SFSO), corn oil (CO) and canola oil (CNO) on growth performance, health status and fillet fatty acid composition of hybrid sturgeon (194.28 ± 0.14 g). Compared to the FO group, dietary SBO decreased growth performance (p < .05), increased serum glucose and hepatic lipid content (p < .05). No obvious adverse effects on growth performance and health status were observed in PNO, SFSO and CO groups (p > 0.05). The fish fed with CNO had increased growth performance (p < .05), reduced serum ALT, AST, LDL‐C (p < .05) and enhanced serum GSH‐Px, T‐AOC, and LZM, MPO, C4 (p < .05). The contents of C18:1n9, C18:2n6, and ∑n‐3 PUFA and ∑n‐6 PUFA in fillets showed a positive linear correlation with the diets (p < .05). In summary, PNO, SFSO and CO are probable alternative lipid sources to fully replace FO. Hybrid sturgeon prefers to use CNO as a lipid source with improved growth performance and health status. The fillet fatty acid composition mirrors the dietary fatty acid composition.     

Stability comparison of three candidate internal reference genes in Chinese giant salamander (Andrias davidianus)

The Chinese giant salamander (Andrias davidianus) as food and medicinal product has been an important aquaculture object in China. Study of gene function in the Chinese giant salamander requires accurate normalization though the use of appropriate reference genes. In this study, the expression levels of three candidate reference genes including β‐actin, GAPDH and cytb of different tissues, different developmental stages and different challenges in Chinese giant salamander were evaluated by qPCR. The stabilities of these three reference genes were analysed by geNorm, NormFinder and BestKeeper software. The results showed that the expression of GAPDH was more stable than that of β‐actin and cytb in four tissues and at two developmental stages of Chinese giant salamander. Compared with GAPDH and cytb, β‐actin was the most stable in spleen of Chinese giant salamander treated with LPS or GSIV. Therefore, the result showed that GAPDH was the suitable reference gene in different tissues and at different developmental stages of Chinese giant salamander. The β‐actin could be used as a reference gene in spleen of Chinese giant salamander challenged with LPS and GSIV. This study provides convincing information for the GAPDH and β‐actin as suitable reference gene in Chinese giant salamander of different tissues, different developmental stages and different challenges respectively.     

Effects of bioflocs with different C/N ratios on growth,immunological parameters,antioxidants and culture water quality in Opsariichthys kaopingensis Dybowski

Biofloc technology (BFT) is a new ecological aquaculture technology that is intended not only to eradicate pollutants and elevate feed utilization but also to enhance immunity and antioxidant activity in aquatic animals. A 28‐day feeding trial was implemented to evaluate the effects of promoted bioflocs on the water quality, growth performance, immunological parameters and antioxidant status of Opsariichthys kaopingensis Dybowski juveniles in low exchange culture tanks. Three hundred sixty healthy O. kaopingensis juveniles (7.1 ± 0.02 g) were irregularly distributed among 12 tanks. Four C:N ratios in triplicate tanks were tried: C/N = 10.8:1 with a commercial diet (control), C/N = 15:1, C/N = 20:1 and C/N = 25:1. Anhydrous glucose (99.97%) was added to the commercial diet to maintain elevated carbon ratio in the three treatments. Uninterrupted 24‐hr aeration was supplied during the test by using an air‐stone connected to an air pump to develop the bioflocs in the water column. The results indicated that BFT significantly reduced total ammonia nitrogen (TAN), nitrite (NO2^?‐N), total phosphorus (TP) concentrations and water transparency (Secchi depth) in C/N 15, C/N 20 and C/N 25 (p < .05), whereas the chemical oxygen demand (COD) and nitrate nitrogen (NO3^?‐N) concentrations gradually increased over time. In addition, weight gain, specific growth rate (SGR), survival and protein efficiency ratio (PER) were significantly elevated in C/N 20, while food conversion rate (FCR) was considerably decreased (p < .05) in C/N 20, compared with the control. Significant increases in lysozyme (LSZ), glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT) and alkaline phosphatase (AKP) activities of O. kaopingensis were found in the C/N 20 group after a 28‐day feeding trial (p < .05). Comparing the antioxidant capacity of O. kaopingensis in gills, brains, kidneys, hepatopancreas, intestines and serum of juveniles from the four experimental groups, the activity of superoxide dismutase (SOD), total antioxidant capacity (T‐AOC), catalase (CAT) activity and glutathione peroxidase (GSH‐PX) activity of juveniles in the C/N 20 group were significant higher (p < .05), and the content of malondialdehyde (MDA) was considerably lower, than in the control. Overall, these findings suggest that BFT not only can enhance O. kaopingensis growth performance and strengthen antioxidant status but also can upgrade immune response, ensuring the sustainable development of aquaculture.     

Effects of antimicrobial peptides on growth,feed utilization,serum biochemical indices and disease resistance of juvenile shrimp,Litopenaeus vannamei

This experiment was conducted to assess the effects of antimicrobial peptides at different levels (Diet 1 (0%), Diet 2 (0.1%), Diet 3 (0.2%), Diet 4 (0.4%), Diet 5 (0.6%) and Diet 6 (1%)), on growth, serum biochemical indices and antioxidant effect, feed utilization and disease resistance in Litopeneaus vannamei. There were four replicates in each group in the experiment (mean weight = 0.21 ± 0.00 g) and also fed with their respective diets for 8 weeks. Growth performance compared with the control group (0%) significantly increased at first and then decreased among treatment groups (p < .05) whereas the survival rate ranged from 78% to 96%. No significant differences were observed in terms of moisture, crude protein and ash content, but there was a significant increase in crude lipid (p < .05). In serum, acid phosphatase, alkaline phosphatase, polyphenol oxidase, triglyceride, glucose and total cholesterol changed as compared with 0%. Total antioxidant capacity, glutathione peroxidase, catalase, superoxide dismutase and malondialdehyde were also different from 0%. Disease resistance was increased in shrimp among treatment groups with 0.4% recording the lowest mortality percentage of 37% after the challenge test. The results from the present study suggested that supplementation of AMP at 0.4% in shrimp diet can improve growth performance, antioxidants activities and innate immune response of Pacific whiteleg shrimp.