青冈栎混交林生物量及碳储量分布特征   总被引：1，自引：1，他引：0  

林立彬  李铁华  杨柳 《水土保持学报》2019,33(1):139-144

以湖南永顺43年生青冈栎混交林为研究对象,采用平均木法和样方收获法测定乔木层生物量和林下植被层生物量,采用重铬酸钾—水合加热法测定样品碳素含量,对林分各组分的生物量和碳储量分布特征进行研究。结果表明:青冈栎混交林单位面积生物量为320.03t/hm~2,各组分单位面积生物量由大到小的排列顺序为乔木层、枯落物层、灌木层和草本层。林分单位面积碳储量高达389.43t/hm~2,其中植被层和土壤层分别为249.02,140.41t/hm~2。林分内青冈栎、栲树和杉木单株平均蓄积分别为0.156 1,0.2912,0.296 0m~3,单株平均碳储量分别为103.85,99.15,97.90kg。青冈栎属于生长速度较慢但木材密度大的树种,单株平均蓄积仅有栲树和杉木的单株平均蓄积的1/2左右,但其单株平均生物量和碳储量却比栲树和杉木的单株平均生物量和碳储量要高,表明树种碳汇能力的高低并不完全取决于树种生长速度的快慢,这对今后生态公益林树种的选择提供了一个新的方向。  相似文献   

农业保险促进小农户与现代农业衔接的路径研究     

占纪文 《现代农业科技》2023,(6):202-207

小农户与现代农业衔接离不开农业保险的支持。衔接有多种方式,也面临多种风险。农业保险在支持衔接过程中仍然存在保障水平低等不足。衔接的基本思路是以衔接过程中的风险保障需求为导向,全面拓展、深化农业保险的损失补偿、信用增进、资金融通、社会管理等功能,提升农业保险保障能力,促进小农户与现代农业衔接。在此基础上提出构建分层级农业保险产品体系等具体实施路径。  相似文献   

Variation in prey selection and foraging success associated with early‐life ontogeny and habitat use of American paddlefish (Polyodon spathula)          下载免费PDF全文

William D. Hintz  Nicolle K. MacVey  Allison M. Asher  Anthony P. Porreca  James E. Garvey 《Ecology of Freshwater Fish》2017,26(2):181-189

Many fishes are planktivorous during early life and switch to piscivory or consume larger food items as ontogeny progresses. In contrast, paddlefish start as particulate feeders and later become filter feeders. Few studies have identified food items essential for paddlefish growth, survival and recruitment surrounding this ontogenetic diet shift. The objectives of this study were to investigate (i) prey types consumed by paddlefish, (ii) variability in prey selection surrounding an ontogenetic diet shift and (iii) whether habitat affected paddlefish prey selection or foraging success. We analysed gut contents of 189 wild age‐0 paddlefish from the middle Mississippi River (MMR) and also conducted a laboratory experiment to address these objectives. We found that paddlefish primarily foraged on benthic macroinvertebrates in the MMR, which differed from previous studies in lentic systems, suggesting young paddlefish prey selection may be labile depending on habitat (i.e., lotic versus lentic). Dominant prey of wild‐caught and experimental age‐0 paddlefish were caddisfly larvae (Trichoptera), followed by hemipterans and amphipods. We found little evidence that habitat attributes affected foraging success, but the most common prey items consumed were associated with wing dike habitat and the upstream and downstream tips of alluvial islands. Our experimental study revealed that if provided a mixture of organisms, age‐0 paddlefish will primarily consume macroinvertebrates while age‐1 paddlefish will mainly filter zooplankton. Overall results suggest young paddlefish prey selection can be highly variable, but also heavily reliant on a narrow group of prey resources.  相似文献   

农村移民创业致富培训困境及对策研究——以台州市为例     

金梦 《江西农业学报》2014,(2):137-139,147

选取了台州市为研究对象,对该地区的农村移民培训情况进行了实地调查研究,发现农村移民培训实践中存在移民主动性不高、培训机构参差不齐、培训实效不强等问题,并提出了相应的对策与建议,以促进农民整体素质的提高,加快农村增收致富步伐,为农村发展提供有益的借鉴。  相似文献   

子莲主要农艺性状与产量的相关及通径分析     

朱红莲  柯卫东  刘玉平  彭静  黄来春  周凯 《中国蔬菜》2014,1(3):41

对7 份子莲材料的主要农艺性状与产量进行相关及通径分析。结果表明：子莲11 个主要农艺性状与产量相关性强
弱为：莲蓬数＞花托直径＞单粒鲜莲子质量＞单个鲜花托质量＞平均心皮数＞鲜果实横径＞结实率＞叶柄粗＞鲜果实纵径＞
叶片长半径＞叶柄高。其中，莲蓬数、花托直径和单粒鲜莲子质量与产量呈极显著或显著正相关。从通径分析结果来看，莲
蓬数、单个鲜花托质量、结实率、平均心皮数对子莲产量的影响主要取决于直接作用；花托直径、鲜果实横径、鲜果实纵径、
叶柄粗对子莲产量的影响主要取决于间接作用；而叶柄高、叶片长半径、单粒鲜莲子质量对子莲产量的影响则通过直接和间
接共同起作用。综合以上分析，提高子莲产量的主攻方向是提高单位面积莲蓬数、单个鲜花托质量、平均心皮数和结实率，
同时兼顾花托直径、单粒鲜莲子质量的增加，并协调好它们之间的关系。  相似文献   

Study on Decision Method in Choosing MIS Softwares for Manufacturing Enterprises     

DAN Bin  WANG Zhi jie  CHENG Sen lin  LIU Fei 《保鲜与加工》1999,(5):32-36

The decision objects and evaluation target architecture in choosing Management Information Systems (MIS) softwares for manufacturing enterprises are proposed. Fuzzy mathematics comprehensive evaluation method is used in decision analysis. The method in is applied practically.  相似文献   

薪炭林植物选择指标数值分析     

汪有科  王晗生  傅左  李立  杨光 《水土保持研究》1992,(1):124-130

根据薪炭林植物应具有热值高,抗旱性强的特点,文章选择了产量、热值、水势、组织含水量、自由水/束缚水和自然饱和亏六个特征指标,在单指标分析的基础上,又应用数值分析技术选出了沙棘、狼牙刺、山桃、柠条、沙打旺、草木樨、苜蓿、红豆草共8个优良的薪炭林植物种。  相似文献   

Factors influencing male mating success in bur oak,Quercus macrocarpa     

Dow  Beverly D.  Ashley  Mary V. 《New Forests》1998,15(2):161-180

Pollen donors of acorns and saplings in a stand of bur oak were identified by paternity exclusion using microsatellite genotype analysis. Here we examine the influence of several factors likely to affect reproductive success of males with wind-dispersed pollen, including distance of pollen donor from maternal tree, genetic relatedness of pollen donor to maternal tree, direction of pollen donor relative to maternal tree, and size of pollen donor (crown volume and trunk diameter). Surprisingly, none of these factors were strongly correlated with fertilization success, although weak but significant correlations with crown volume and distance were found. The slight influence of distance is actually overestimated here, because our analysis necessarily excluded a large proportion of pollinations that were effected by trees outside the stand. The pollen donors outside the stand were not identified, but were more than 150 meters away. Pollination patterns in this stand of bur oak are quite complicated. Seed parents were fertilized by multiple pollen donors within the stand from all directions and as far as 200 m away. These results caution against the use of models of pollination that are based on simple distance or directional parameters because they will not adequately predict gene flow or male reproductive success. Our results further emphasize the importance of genetically identifying successful pollen donors rather than relying on patterns of physical movement of pollen.  相似文献   

山东省不同土类微量元素含量及分布状况     

吴建明  高贤彪  高弼模  林日辉  房瑞士  李正英 《中国农业科学》1988,21(2):17-24

结合83个县土壤普查,测定6千多个土样,通过微机处理数据,对山东省不同土类微量营养元素含量分析汇总。认为本省土壤以缺硼、锌为主,部分缺锰;在3个地貌区的分布有明显规律,元素间有密切相关;各土类各元素的丰缺也有明显规律,并多呈正偏态分布,应以中位数和平均差表示之;本省土壤工作分类基本适于研究微量元素含量分布和应用微肥的依据;各元素在土壤剖面中含量多随深度而降低;土壤微量元素与成土母质关系密切,pH、碳酸钙也是重要的影响因素。  相似文献   

制干辣椒若干数量性状遗传研究   总被引：6，自引：0，他引：6  

杨广东  雷锋进 《山西农业科学》1999,27(4):50-52

对１２ 份制干辣椒材料的９ 个植株性状进行了简单相关和偏相关分析,并在相关系数的基础上,进行了各相关性状对单果重的遗传通径分析,此外还估算了这９ 个性状的遗传相关信息及其贡献。结果表明,单果重、果宽、果皮厚度和干缩率是影响产量的重要性状;单果重的遗传相关贡献大于其他各性状;果宽对单果重起主要决定作用,果皮厚度通过果宽对单果重产生一定的间接影响。  相似文献