Discussion on the Bibliographic Collection in Multi-Campus University Libraries under the dynamic Taking Library of Shandong Agricultural University as an Example     

《农业图书情报学刊》2012,24(1)

通过调查统计分析多校区多学科动态变化对图书馆馆藏文献配置典藏工作带来的影响,结合山东农业大学图书馆实际工作情况,提出了动态环境下文献配置典藏策略。  相似文献   

农业水利调配问题研究   总被引：1，自引：0，他引：1  

张远福  马舰 《安徽农业科学》2010,38(6):3152-3153

针对农业水利调配过程中存在的问题,提出了一种费用最小的水利调配方法。  相似文献   

赤眼蜂寄生行为研究（Ⅳ）—子代数量分配和子代性分配   总被引：1，自引：0，他引：1  

郭明Fang  张兢业 《昆虫天敌》1993,15(2):51-59

本文在对赤眼蜂性控行为研究的基础上〔3〕,进一步探讨了不同种赤眼蜂在同一种寄主不同分布以及同一蜂种(松毛虫赤眼蜂 Trichogramma dendrolimi)在不同种寄主上的子代数量分配和子代性分配问题。研究结果表明,赤眼蜂具有根据寄主卵体积大小分配及调整其子代数量和子代性别的能力,在不同体积的寄主上具有明显不同的子代数量安排策略和子代性安排策略。在同一种寄主卵上,不同种的赤眼蜂对子代性分配的安排存在着较明显的种间差异.在米蛾卵上,松毛虫赤眼蜂的第一雄卵主要在其第一产卵序产出,稻螟赤眼蜂的第一雄卵主要在其第二产卵序产出,拟澳洲赤眼蜂产第一雄卵的位置比较分散,主要分布在前三卵序。松毛虫赤眼蜂大约每产6粒雌卵而产1粒雄卵;稻螟赤眼蜂和拟澳洲赤眼蜂大约每产5.33和3.37粒雌卵而产1粒雄卵(见表2).寄主卵的体积不同,雌蜂在不同寄主上所分配的子代数量也明显不同。松毛虫赤眼蜂在每粒米蛾卵上只安排1粒蜂卵;在每粒马尾松毛虫卵上平均安排18.64粒蜂卵;在每粒“人造卵”上平均安排33.15粒,在柞蚕卵上平均安排77.43粒蜂卵(见表3)。随着寄主卵体积的增大,雌蜂产第一雄卵的时间后移,在松毛虫卵上,松毛虫赤眼蜂雌蜂在产下第一粒雄卵后,大约以每产16粒雌卵而产1粒雄卵;在柞蚕卵上,大约每隔15粒雌卵产1粒雄卵;在“人造卵”上,产雄卵的间隔大约为9粒雌卵。  相似文献   

21世纪我国农业资源配置战略   总被引：5，自引：1，他引：4  

罗其友 《农业现代化研究》2000,21(1):37-40

水土问题是２１世纪可持续发展诸多矛盾的焦点。进入８０年代水土对我国农业的约束不断硬化，并长期困绕我国农业的可持续发展，摆脱困境的基本思路是实施农业资源高效持续配置战略－－“实现四个结合，建设六大体系”。  相似文献   

封育年限对典型草原大针茅无性系构件组成与生长的影响     

平伟梦  赵凌平  梁方晖  谭世图  王冬  孙平  赵芙蓉 《草业科学》2022,1(1):2135-2143

研究不同封育年限对黄土高原大针茅(Stipa grandis)无性系构件结构组成和生长的影响,可为阐明无性系构件组成和资源分配提供一定基础。在黄土高原典型草原选取不同封育年限区(10和20年)和放牧地(对照)作为试验样地,采用整个无性系完整挖掘的方法进行大针茅无性系构件特征的研究。结果表明：1)与放牧相比,封育10年显著增加了大针茅无性系丛径、生殖枝高度和花序高度(P < 0.05),而封育20年则显著提高了大针茅无性系丛径、总枝数、生殖枝数、营养枝数、分蘖芽数、生殖枝高度、花序高度、地上总生物量、营养枝生物量和花序生物量(P < 0.05)。封育降低了大针茅生殖枝数、生殖枝高度、花序高度、地上总生物量、生殖枝生物量和花序生物量的变异系数。2)随封育年限增加,营养枝生物量比例明显提高,生殖枝生物量比例下降,但花序生物量比例基本不变。3)封育措施显著提高了营养株单株生物量(P < 0.05),但生殖株单株生物量和全体分枝单株生物量与放牧处理差异不显著(P > 0.05)。4)大针茅丛径与地上总生物量、生殖枝数、生殖枝生物量、花序生物量呈极显著正相关关系(P < 0.001),与营养枝生物量呈极显著正相关关系(P < 0.01),与总枝数呈显著正相关关系(P < 0.05)。而地上总生物量与生殖枝数、营养枝数、总枝数、营养枝生物量呈极显著正相关关系(P < 0.001),与分蘖芽数、生殖枝生物量和花序生物量呈极显著正相关关系(P < 0.01)。分蘖芽数与营养枝数、总枝数、营养枝生物量呈极显著正相关关系(P < 0.001),与地上总生物量呈极显著正相关关系(P < 0.01)。综上所述,短期封育提高了大针茅的生殖分配,使大针茅迅速成为群落优势种,而长期封育使大针茅更依靠无性繁殖进行种群更新。  相似文献   

异质光环境中旱柳的光截取和利用反应   总被引：1，自引：1，他引：1  

何维明  董鸣 《林业科学》2002,38(3):7-13

比较了不同光环境中旱柳枝，叶的生物量分配，形态特征，光能利用和水分特征。（1）阳性枝的枝重比显著大于全不遮荫枝；阴生枝的枝重比显著小于全部遮荫枝，而叶重比恰好相反。（2）阳生枝与全不遮荫枝的形态特征无显著差异。阴生枝的叶面积比率，比枝长和单位枝长叶数都显著大于全部遮荫枝，因而阴生枝的截光潜力大于全部遮荫枝。（3）阳性枝和阴生枝的植冠生产力指数分别显著大于全不遮荫枝和全部遮荫枝，因此，异质光环境中旱柳植株对光资源的利用效率大于同质光环境，（4）阳生枝的水分饱和亏缺和失水系数都显著小于全不遮荫枝，这暗示，前者的抗旱保水性大于后者。  相似文献   

Application of the pipe model theory to non-destructive estimation of leaf biomass and leaf area of pruned agroforestry trees     

P. Nygren  S. Rebottaro  R. Chavarría 《Agroforestry Systems》1993,23(1):63-77

The relationship of branch cross sectional area (CS) to leaf biomass (LM) and leaf area (LA) was studied in three agroforestry tree species,Calliandra calothyrsus Maissn.,Erythrina berteroana Urban andErythrina poeppigiana (Walpers) O.F. Cook, to develop a non-destructive method for the estimation of LM and LA for trees managed with periodic pruning. Variation in these relationships was observed according to the bifurcation level and, in theErythrina spp., by clone. All the relationships were linear except the CS-LM relation in small branches ofE. poeppigiana, where it was initially exponential. At main branch level the relationship of CS to LM and LA was linear in all cases but the regression parameter values varied between species and clones, with determination coefficient (R²) 0.88–0.99. It was concluded that the ratio of main branch CS to LM and LA can be used for non-destructive estimation of the latter variables. The method has the additional benefit that the regression parameter value reflects the allocation of dry matter within a tree and, consequently, may give indications about its possible uses in different agroforestry systems.Work carried out at the Centro Agronómico Tropical de Investigación y Enseñanza (CATIE), Turrialba, Costa Rica.  相似文献   

The carbon budget of an adult <Emphasis Type="Italic">Pinus cembra</Emphasis> tree at the alpine timberline in the Central Austrian Alps     

Gerhard?WieserEmail author  Thomas?Gigele  Hans?Pausch 《European Journal of Forest Research》2005,124(1):1-8

We investigated carbon (C) uptake and respiratory losses of an adult Pinus cembra tree at the alpine timberline throughout an entire year by means of an automated, multiplexing gas exchange system. These chamber measurements were then combined with biomass data for scaling up the C budget to the tree level. Integrated over an entire year, the cumulative C gain of the tree under study was 23.5 kg of C in 2002. The daily C balance was negative for 5 months and the estimated total wintertime respiratory losses were 9% of the amount of C fixed during the growing season. The total annual C loss of the tree consumed 55% of the annual net C gain and the remaining surplus was stored in new tissues (36%) and used for fine root growth (9%). Thus, the overall C budget of P. cembra at the upper timberline is balanced fairly well, although the C sink strength in fine roots is strongly limited owing to low root zone temperatures when compared to conifers at lower elevation sites.  相似文献   

Above- and belowground biomass measurements in an unthinned stand of Sitka spruce (<Emphasis Type="Italic">Picea sitchensis</Emphasis> (Bong) Carr.)     

Carly Green  Brian Tobin  Michael O’Shea  Edward P. Farrell  Kenneth A. Byrne 《European Journal of Forest Research》2007,126(2):179-188

Reporting carbon (C) stocks in tree biomass (above- and belowground) to the United Nations Framework Convention on Climate Change (UNFCCC) should be transparent and verifiable. The development of nationally specific data is considered ‘good practice’ to assist in meeting these reporting requirements. From this study, biomass functions were developed for estimating above- and belowground C stock in a 19-year-old stand of Sitka spruce (Picea sitchensis (Bong) Carr.). Our estimates were then tested against current default values used for reporting in Ireland and literature equations. Ten trees were destructively sampled to develop aboveground and tree component biomass equations. The roots were excavated and a root:shoot (R) ratio developed to estimate belowground biomass. Application of the total aboveground biomass function yielded a C stock estimate for the stand of 74 tonnes C ha⁻¹, with an uncertainty of 7%. The R ratio was determined to be 0.23, with an uncertainty of 10%. The C stock estimate of the belowground biomass component was then calculated to be 17 tonnes C ha⁻¹, with an uncertainty of 12%. The equivalent C stock estimate from the biomass expansion factor (BEF) method, applying Ireland’s currently reported default values for BEF (inclusive of belowground biomass), wood density and C concentration and methods for estimating volume, was found to be 60 tonnes C ha⁻¹, with an uncertainty of 26%. We found that volume tables, currently used for determining merchantable timber volume in Irish forestry conditions, underestimated volume since they did not extend to the yield of the forest under investigation. Mean stock values for belowground biomass compared well with that generated using published models.  相似文献   

福建省杉木人工林生物量及其分配研究   总被引：5，自引：0，他引：5  

方宗辉 《福建林业科技》2005,32(3):82-85

通过收集福建省杉木林生物量数据,对福建省杉木林生物量及其分配规律进行分析,结果表明,杉木林生物量随年龄增长呈逐渐增加趋势,并以幂方程拟合的效果最好。杉木林叶和枝生物量占总生物量的比例均随年龄增加而呈明显下降趋势,根占总生物量比例的下降趋势则较小,而干占总生物量比例则随年龄增长而明显增加。叶、枝、干生物量占总生物量比例与年龄拟合的效果较好,且最佳方程均为三次方程。根生物量占总生物量比例与年龄拟合的效果则较差。除年龄对根生物量分配比例有极显著负相关外,降水量对根系生物量分配比例亦有显著的负相关。  相似文献