Density dependence on tree survival in an old-growth temperate forest in northeastern China

? Density dependence is a major mechanism for shaping plant communities. However, its role in regulating diverse, mixed natural tree communities is less certain.

? In this study we investigated density-dependent effects in a large-scale (25 ha) old-growth temperate forest in northeastern China. Spatial patterns of neighborhood distribution in the plot were analyzed using various methods for inferring competition, including (1) pair correlation function to determine spatial patterns of pre-mortality and post-mortality and (2) neighborhood analysis of individuals to examine the extent to which tree survival is correlated with other covariates.

? Results showed that, for common species, 3 of 5 canopy species and 3 of 8 midstory and understory species were random in mortality. Negative density-dependent mortality was not found when trees reach 1 cm in DBH. There was no significant correlation for canopy species between tree survival and conspecific abundance, but largely positive correlations for midstory and understory species. In contrast, tree survival was found to negatively correlate with conspecific basal area for most species, indicating strong intraspecific competition. No strong interspecific density dependence was found in the forest.

     

N+离子注入对萌发期小麦中POD和SOD同工酶的影响

采用垂直板聚丙烯酰胺凝胶电泳技术,研究N+离子注入处理后小麦种子豫麦34萌发时期根、盾片、芽、胚乳中POD和SOD同工酶的变化.结果表明:N+离子注入可引起豫麦34的不同器官中POD和SOD同工酶的酶带与酶活性的不同变化,除芽中POD和SOD同工酶活性无明显变化外,其它器官中POD和SOD同工酶均表现为活性增强.4种器官相比,根和胚乳中同工酶变化较大,盾片和芽中同工酶变化不明显.其中,根中同工酶变化更为显著,N+离子束注入处理后根中POD同工酶多了Rf值为0.47的新酶带.     

氮用量对小黑麦东农96026群体生长及饲用品质的影响

为小黑麦东农96026在黑龙江省哈尔滨地区种植获得高的产量及较优的饲用品质,研究从栽培措施的密度及氮肥施用入手,采用裂区设计,4个密度水平（基本苗750万株/hm2,600万株/hm2,450万株/hm2,300万株/hm2）,3个施氮水平（纯氮75kg/hm2, 150kg/hm2, 225kg/hm2）,研究了不同密度和氮肥处理对小黑麦东农96026生长发育、产量及饲用品质的影响。结果表明,降低密度和增加氮素营养水平利于提高东农96026的生物产量,并具有较好的饲用品质。在种植密度为450万株/hm2、施氮水平为150kg/hm2时产量结构比较协调,品质最优。     

小麦春溶蛋白酸性聚丙烯酰胺凝胶电泳（A-PAGE）方法的优化与改良及其应用

依据国际种子检验协会（ISTA）1986年公布的标准小麦醇溶蛋白酸性聚丙烯酰胺凝胶电泳（A-PAGE）方法,结合国内实验室的实际情况,摸索出了适合我国试剂和仪器的小麦醇溶蛋白酸性聚丙烯酰胺凝胶电泳（A-PAGE）的改良方法。该方法克服了标准方法中的胶韧性差、剥胶困难、分辨率不高、谱带识别繁琐、实验效率较低的限制,适合我国小麦品种纯度的快速鉴定、血缘关系分析等。     

滇东南喀斯特石漠化地区粮食增产的主导因素分析——以西畴县为例

根据西畴县近17年（1990 ~ 2006年）的耕地资源和社会经济统计数据,运用多元统计分析中的主成分分析方法来分析西畴石漠化地区影响粮食增产的主导因素。结果表明,耕地质量对粮食增产的贡献率是69.85%,经济投入水平对粮食增产的贡献率是20.29%,说明耕地质量因素是西畴石漠化地区粮食增产的主导因素,而耕地质量的提高则主要得益于西畴土地整理模式的实施。在西畴石漠化地区后备耕地资源极为缺乏,以及因为经济建设发展需要耕地减少难以避免的情况下,只有坚定不移地推进土地整理,切实加强土壤改良和农田基础设施建设,从根本上改良耕地和提高耕地质量,才能提高耕地产出水平,进而提高粮食产量。     

外源NO对渗透胁迫下红三叶幼苗生长抑制及氧化损伤的缓解效应

25%的聚乙烯醇-6000(PEG-6000)渗透胁迫下,研究一氧化氮(NO)对红三叶(Trifolium pretenseL.cv.Altaswede)幼苗生长抑制及氧化损伤的缓解效应.结果表明:(1)0.05 mmol/L NO供体硝普钠(Sodium nitroprusside,SNP)可显著减轻渗透胁迫对幼苗生长的抑制,显著促进幼苗叶片超氧化物歧化酶(superoxide dismutase,SOD)、过氧化氢酶(catalase, CAT)和过氧化物酶(peroxidase,POD)的活性,降低丙二醛(malondialdehyde,MDA)含量,显著缓解渗透胁迫对红三叶造成生长抑制和氧化损伤作用;(2)高浓度(0.1 mmol/L)SNP处理对渗透胁迫的缓解效应不佳,甚至加重对植物的氧化损伤.     

A New Beam Column Element of Space Framed Structures for Nonlinear Analysis of Geometric Material

An incremental virtual work equation of three dimensional(3D) beam column element is proposed based on the UL method. The geometric nonlinear tangent stiffness matrix for 3D beam column element is deduced with the consideration of warping, shear deformation and effects of moment spatial rotation. Material nonlinearity is addressed by introducing plastic hinges at the element ends. And the Orbison sectional strength is modified in order to consider the effects of torsion moment and warping. The elastic plastic tangent stiffness matrix is acquired as the element ends are in plastic phase based on the flow theory. With a case studied, it is shown that the model can be used to predict accurately the ultimate bearing capacity and instability mode of 3Dspace frames by only one or two elements, and address the effects of warping and shear deformations effectively.     

采用均匀设计法优化西选二号培养基配比

以西选二号为试材,运用均匀试验设计方法调整植物生长调节剂的浓度和种类,通过建立回归模型筛选出适宜于西选二号植株愈伤组织形成、不定芽诱导和植株生根的最佳配方.结果表明:以MS+0.5 mg·L-16-BA+0.1 mg·L-1NAA作为愈伤组织的诱导培养基,可以获得92%的愈伤组织诱导率.MS+3.0 mg·L-16-BA +0.1 mg·L-1NAA可作为芽诱导培养基,其芽分化率为90%.使用芽诱导培养基,附加0.6 mg·L-1GA3作为增殖继代培养基为宜.在1/2MS+1.0 mg·L-1 IBA+0.2 mg·L-1NAA培养基中,芽苗诱导生根效果较佳.小植株炼苗移栽成活率达85%.     

培养基中附加物质对辣椒花药培养的影响

以辣椒红艳为试材,采用均匀设计法考察培养基中不同含量的活性炭、蔗糖和单核苷酸对辣椒花药培养中愈伤组织诱导率和胚状体诱导率的影响.结果表明各因素对辣椒花药愈伤组织诱导率和胚状体诱导率的影响大小均为:蔗糖含量>活性炭含量>单核苷酸含量.诱导愈伤组织的最优条件是1.5 g/L活性炭、65 g/L蔗糖和30 ms/L单核苷酸的组合;诱导胚状体的最优条件为1.5 g/L活性炭,30 s/L蔗糖和30 mg/L单核苷酸的组合.     

烤烟不同留叶数与农艺性状、经济性状的相关关系研究

为了研究不同留叶数对烤烟农艺性状和经济性状的影响,2008～2009年以津引烤烟品种KRK26为材料,对相同生产条件下不同留叶数的烤烟开片情况、外观质量等农艺性状和经济性状进行了研究。结果表明：不同留叶数与表现出的农艺性状和经济性状呈正相关。因此选择适当的留叶数对提高烟叶质量和农业经济效益起着至关重要的作用。