黑龙江省国有林区脆弱异质性家庭对停伐政策的态度及影响因素研究     

杨博琳  王蕾  刘钰佳  李娇  赵宗胤 《安徽农业科学》2017,45(16)

基于2016年黑龙江省重点国有林区348户家庭的微观调查数据,实证分析黑龙江省国有林区脆弱异质性家庭对停伐政策的态度及影响因素。采用因子分析与综合评价法将348户职工家庭分为脆弱性家庭和非脆弱性家庭,描述性分析2组样本家庭对停伐政策的态度及认知情况,利用多元有序logit模型分析脆弱性与非脆弱性家庭对停伐政策态度的影响因素。结果表明:非脆弱性家庭对停伐政策的了解程度及执行情况的评价均高于脆弱性家庭,脆弱性家庭相对非脆弱性家庭对停伐政策的认可度较高,但是应对风险冲击的能力相对较低。脆弱性家庭和非脆弱性家庭对停伐政策的态度受户主特征、家庭特征以及政策认知特征变量的显著影响,但脆弱性家庭变量参数估计绝对值相对更大,因而停伐政策对脆弱性家庭有着更为敏感和强烈的冲击。  相似文献   

钢筋混凝土结构锈蚀损伤定位     

吴瑾  程吉昕  陆明生 《勤云标准版测试》2004,(4)

对钢筋混凝土结构锈蚀损伤定位进行了研究,以频率变化平方比作为锈蚀损伤参数,从理论上证明该参数是锈蚀损伤位置的函数。锈蚀钢筋混凝土结构试验结果表明预测的损伤位置和实际的损伤位置较一致,模态参数用于检测混凝土结构构件中的损伤,为大型结构的鉴定和评估提供了新的途径。  相似文献   

小麦矮秆育种中性状间关系的多元分析   总被引：12，自引：0，他引：12  

何中虎  张树榛 《华北农学报》1992,7(1):1-7

以7个株高梯度系列的35个系统及5个亲本品种为材料,采用典范分析和逐步回归分析研究了株高及其构成因子与产量因子、产量生理性状间的关系。结果表明:①株高因子通过产量生理性状影响产量因子,一定的生物学产量是获得高产的基础。②矮秆品种的高化对提高产量、千粒重和收获指数有利,对蛋白质含量的影响不明显;高秆品种矮化能显著提高收获指数,对籽粒的蛋白质含量影响不大。③在主要性状符合育种目标的前提下,选择倒二节间较长、第一和第二叶间距略长、穗颈和穗部较长的类型可能对提高产量有利。  相似文献   

‘过山香’香蕉多芽体的诱导及其体细胞胚的发生   总被引：7，自引：2，他引：7  

魏岳荣  黄学林  黄霞  李佳  肖望  李筱菊 《园艺学报》2005,32(3):414-419

 以我国重要香蕉种质‘过山香’ (AAB) 为材料, 研究了香蕉多芽体诱导、多芽体茎尖薄切片即分生组织性的表层结构物( scalp) 愈伤组织诱导和体细胞胚发生的合适条件。结果表明, 该品种单个不定芽茎尖在P4培养基(含BAP 100 μmol·L ^{- 1}和IAA 1 μmol·L ^{- 1} ) 中继代5个周期后可诱导获得类似花椰菜结构的多芽体。从30 μmol· m ^{- 2} ·s^{- 1}光强, 光/暗周期(16 h /8 h) 培养的多芽体所获得的scalp在添加2,4-D 5μmol·L ^{- 1}和Zeatin 1 μmol·L ^{- 1}的愈伤组织诱导培养基中黑暗培养, 45 d后愈伤组织诱导率可达97.6%。诱导20 d后黄色分生小球体类结节状愈伤组织开始发生, 90～120 d后在分生小球体局部可获得白色或浅黄色松散的胚性愈伤组织(诱导率为17.5% ) 。从胚性愈伤组织诱导的体细胞胚在成熟培养基上培养60 d后体胚萌发率和植株转化率分别为14.5%和11.1%。  相似文献   

Enhancing pedotransfer functions with environmental data for estimating bulk density and effective cation exchange capacity in a data‐sparse situation          下载免费PDF全文

S. I. C. Akpa  S. U. Ugbaje  T. F. A. Bishop  I. O. A. Odeh 《Soil Use and Management》2016,32(4):644-658

Soil bulk density (BD) and effective cation exchange capacity (ECEC) are among the most important soil properties required for crop growth and environmental management. This study aimed to explore the combination of soil and environmental data in developing pedotransfer functions (PTFs) for BD and ECEC. Multiple linear regression (MLR) and random forest model (RFM) were employed in developing PTFs using three different data sets: soil data (PTF‐1), environmental data (PTF‐2) and the combination of soil and environmental data (PTF‐3). In developing the PTFs, three depth increments were also considered: all depth, topsoil (<0.40 m) and subsoil (>0.40 m). Results showed that PTF‐3 (R²; 0.29–0.69) outperformed both PTF‐1 (R²; 0.11–0.18) and PTF‐2 (R²; 0.22–0.59) in BD estimation. However, for ECEC estimation, PTF‐3 (R²; 0.61–0.86) performed comparably as PTF‐1 (R²; 0.58–0.76) with both PTFs out‐performing PTF‐2 (R²; 0.30–0.71). Also, grouping of data into different soil depth increments improves the estimation of BD with PTFs (especially PTF‐2 and PTF‐3) performing better at subsoils than topsoils. Generally, the most important predictors of BD are sand, silt, elevation, rainfall, temperature for estimation at topsoil while EVI, elevation, temperature and clay are the most important BD predictors in the subsoil. Also, clay, sand, pH, rainfall and SOC are the most important predictors of ECEC in the topsoil while pH, sand, clay, temperature and rainfall are the most important predictors of ECEC in the subsoil. Findings are important for overcoming the challenges of building national soil databases for large‐scale modelling in most data‐sparse countries, especially in the sub‐Saharan Africa (SSA).  相似文献   

Effects of Rice Variety and Growth Location in Cambodia on Grain Composition and Starch Structure简     

Seila SAR  Morgan J. TTZZOTTT  Jovin HASJTM  Robert G. GTLBERT 《水稻科学》2014,21(1):47-58

The effects of variety and growth location on grain composition and starch structures were investigated using three rice (Oryza sativa L.) cultivars (Phka Romduol, Sen Pidao and IR66) with different amylose contents. All the three cultivars were planted in three different agro-climatic zones (Phnom Penh, Coastal and Plateau) of Cambodia. The protein content of polished grains increased when rice was planted at a location with higher average temperature, but their lipid content decreased. The amylose content and degree of branching were not greatly affected by the minor temperature differences among the growing locations. Starch fine structures characterized by the chain-length distribution were significantly different among the cultivars, but not significantly among different locations. The results suggested that protein and lipid biosyntheses were more sensitive to the environmental temperature than that of starch in rice grains.  相似文献   

沈阳铁西区装备制造产业聚集实证分析     

刘湛 《农业机械化与电气化》2014,(6):20-23

铁西区通过打造装备制造业产业聚集区。形成了高档数控机床、通用石化装备等六大主导产业以及电气及新能源等五大千亿产业集群，成为我国老工业基地振兴的区域典范。介绍铁西装备制造业聚集区发展现状，采用区位熵法测算沈阳装备制造业的产业集中度，对全市装备制造业的现状及问题进行分析，得出相应结论。  相似文献   

Effects of cover crop growth and decomposition on the distribution of aggregate size fractions and soil microbial carbon dynamics          下载免费PDF全文

D. Linsler  M. Kaiser  R. Andruschkewitsch  C. Piegholdt  B. Ludwig 《Soil Use and Management》2016,32(2):192-199

Although the effects of cover crops (CC) on various soil parameters have been fully investigated, less is known about the impacts at different stages in CC cultivation. The objective of this study was to quantify the influence of CC cultivation stages and residue placement on aggregates and microbial carbon (C_mic). Additionally, the influence of residue location and crop species on CO₂ emissions and leached mineralized nitrogen (N_min) during the plant degradation period was also investigated. Within an incubation experiment, four CC species were sown in soil columns, with additional columns being kept plant‐free. After plant growth, the columns were frozen (as occurs in winter under field conditions) and then incubated with the plant material either incorporated or surface‐applied. With CC, concentrations of large and medium macroaggregates were twice that of the fallow, confirming positive effects of root growth. Freezing led to a decrease in these aggregate size classes. In the subsequent incubation, the large macroaggregates decreased far more in the samples with CC than in the fallow, leading to similar aggregate size distributions. No difference in C_mic concentration was found among the CC cultivation stages. CO₂ emissions were roughly equivalent to the carbon amounts added as plant residues. Comparison of columns with incorporated or surface‐applied residues indicated no consistent pattern of aggregate distribution, CO₂ emission or C_mic and N_min concentrations. Our results suggest that positive effects of CC cultivation are only short term and that a large amount of organic material in the soil could have a greater influence than CC cultivation.  相似文献   

基于SPEI_PM指数的渭河流域气象干旱时空演变特征     

杨睿  耿广坡  周洪奎  王涛 《中国农业气象》2021,42(11):962

利用渭河流域25个气象站点1980−2018年月值气象数据集，基于Penman-Monteith蒸散模型计算多个时间尺度的标准化降水蒸散发指数（SPEI），分析渭河流域气象干旱的演变、趋势、影响范围、发生频率和持续时间等时空变化特征，以期为渭河流域防灾减灾管理提供科学依据。结果表明：（1）近39a来渭河流域有明显的干湿周期变化，但整体上呈变干的趋势，干旱时段主要集中在1995−2009年，其中以2000−2009年的干旱站次比最大，平均达到36%，且干旱持续时间最长，约3.6个月，1980−1989年干旱持续时间最短，约1.6个月；（2）渭河流域秋季总体呈湿润变化趋势，而春季和夏季干旱在不断加剧，是区域年际干旱的主要驱动力；（3）渭河流域干旱以危害性较小的轻中旱为主，但2000年前后出现严重及极端干旱的站次相对较多，其中1997年研究区内发生的干旱程度较高，影响范围较广；（4）不同时间尺度各等级干旱发生频率的变化规律表现一致，均呈现出干旱等级越高发生频率越低的态势，且极端干旱在年际尺度内发生次数较为频繁，从空间上看渭河流域东北部是干旱多发区。总之，近39a来渭河流域总体干旱较为严重的时段为2000−2009年，且研究区内干旱呈北重南轻特征，因此北部地区仍需加强防灾管理。  相似文献   

Antioxidant,anti-amylase and anti-glycation potential of brans of some Sri Lankan traditional and improved rice (Oryza sativa L.) varieties     

《Journal of Cereal Science》2014,59(3):451-456

Brans of 23 traditional and 12 improved (both red and white) rice varieties in Sri Lanka were screened for anti-amylase and anti-glycation activities in vitro. Varieties which showed the highest inhibitory activities at screening were further investigated for anti-glucosidase and glycation reversing as anti-diabetic properties. The same varieties were studied for selected antioxidant properties. Significantly high anti-amylase and anti-glycation activities were observed for bran extracts of red varieties compared to white varieties at screening. Traditional red rice varieties, Masuran, Sudu Heeneti, Dik Wee and Goda Heeneti, exhibited significant and dose dependent anti-amylase, anti-glycation and glycation reversing activities. These varieties also showed marked antioxidant properties. It is concluded that brans of Sri Lankan traditional red rice varieties Masuran, Sudu Heeneti, Dik Wee and Goda Heeneti may be potential food supplements for diabetes.  相似文献