退化草地群落演替趋向研究进展

草地群落的退化演替以植物个体、种群与群落层次上植物的动态以及土壤理化性状的改变等现象为表征。主要从植物个体形态特征、草地退化模式、草地土壤养分变化等方面对退化的响应,探讨了草地退化演替的特征和趋势,建议今后对草地的退化演替机理、放牧生态学、恢复生态学、界面生态学及草地的价值评估等方面进行更深入的研究。     

基于MaxEnt 的云南省薇甘菊分布预测及评价

利用MaxEnt生态位模型预测云南薇甘菊适生区分布,结果显示,ROC曲线的AUC值均在0.9以上,预测结果具有较高的可信度.影响薇甘菊分布的主要环境因子包括最湿季降雨量(贡献率28.8％)、海拔(贡献率22.1％)、土地覆盖现状(贡献率15.3％)、最湿季平均温、年均降水量、年平均温.从因子的响应曲线分析得出,云南薇甘菊最适环境参数为海拔1 100m,最湿季平均温为22℃,最湿季降雨量为760 mm,土地覆盖为未郁闭林地、灌木林地和荒地等.从样本点数量、环境因子选择及人为影响3个方面对MaxEnt模型预测的云南薇甘菊分布结果进行比较和评价.     

No DNA loss in autotetraploids of Arabidopsis thaliana

To address the issue of genome evolution in autopolyploids and particularly to investigate whether rapid sequence elimination also occurs in autopolyploids as in allopolyploids, amplified fragment length polymorphism (AFLP) fingerprinting was employed to examine a large number of genomic loci in F₁ hybrids between two different autotetraploids of Arabidopsis thaliana accessions, namely Ler and Col. Using this approach, perfect additivity in the F₁ hybrids was found between the newly‐formed autopolyploids when compared with their parental lines. Using flow cytometry, the study was extended in a quantitative manner, in which the nuclear DNA contents in one autotetraploid A. thaliana accession Ler, was determined. The increase in genome size of the autotetraploid line was additive. Taken together, no evidence was found for genome size reduction due to autopolyploidization of A. thaliana. The results indicating that there was no DNA loss in autotetraploid A. thaliana suggest that a different type of genome evolution may occur in autopolyploids during the initial stages of their formation when compared with allopolyploids.     

Neural networks with artificial bee colony algorithm for modeling daily reference evapotranspiration

The study investigates the ability of artificial neural networks (ANN) with artificial bee colony (ABC) algorithm in daily reference evapotranspiration (ET₀) modeling. The daily climatic data, solar radiation, air temperature, relative humidity, and wind speed from two stations, Pomona and Santa Monica, in Los Angeles, USA, are used as inputs to the ANN–ABC model so as to estimate ET₀ obtained using the FAO-56 Penman–Monteith (PM) equation. In the first part of the study, the accuracy of ANN–ABC models is compared with those of the ANN models trained with Levenberg–Marquardt (LM) and standard back-propagation (SBP) algorithms and those of the following empirical models: The California Irrigation Management System (CIMIS) Penman, Hargreaves, and Ritchie methods. The mean square error (MSE), mean absolute error (MAE) and determination coefficient (R²) statistics are used for evaluating the accuracy of the models. Based on the comparison results, the ANN–ABC and ANN–LM models are found to be superior alternative to the ANN–SBP models. In the second part of the study, the potential of the ANN–ABC, ANN–LM, and ANN–SBP models in estimation ET₀ using nearby station data is investigated.     

林木受小蠹虫危害的表征及其遥感监测

通过查阅大量相关文献,分析了小蠹虫对寄主树的选择和定殖,小蠹虫、真菌与寄主树的相互关系以及寄主树的防御反应,总结了遥感在小蠹虫早期危害监测上的应用。     

云南切梢小蠹细胞色素P450基因的克隆与分析

利用RACE技术,从云南切梢小蠹Tomicus yunnanensis中克隆获得了一个细胞色素P450基因cDNA序列。该基因简写为TyunP450,其序列长1 524 bp,开放性阅读框为1 269 bp,编码422个氨基酸,预测蛋白分子量为48.50 ku,pI为8.94。通过MotifScan分析发现,TyunP450氨基酸序列中潜在1个酰胺化位点(XGR265-268)、4个N-糖基化位点(NLSV33-36、NDSV87-90、NGST97-100和NASK372-375)、4个酪蛋白激酶Ⅱ磷酸位点(SVTE176-179、TQRD187-190、SDED217-220和TIDE420-423)、5个N-豆蔻酰化位点(GNVFGF2-7、GNVYND40-45、GGQNAA163-168、GGILSD213-218和GTNIAI340-345)、8个蛋白质激酶C磷酸化位点(SLK77-79、STK99-101、TQR187-189、SLK210-212、SLR288-289、SHK417-419、SLK431-433和TLR443-445)、1个P450细胞色素血红素铁配体的半胱氨酸位点(FSSGPRDCLG384-393),204~316氨基酸区域具有典型的细胞色素P450结合位点结构,317~441氨基酸区域具有典型的细胞色素P450结合位点结构,9~28氨基酸区域具有DUF321蛋白的未知函数结构域,1~441氨基酸区域具有典型的细胞色素P450结合位点结构。TyunP450与埃及伊蚊Aedes aegypt、家蚕Bombyx mori、丽蝇蛹集金小蜂Nasonia vitripennis、赤拟谷盗Tribolium castaneum和豌豆蚜Acyrthosiphon pisum的P450氨基酸序列相似性分别为19%、20%、21%、23%和15%。     

牦牛研究中重复测量方差分析及其在SPSS16.0中的实现

应用SPSS16.0中GLM的Repeated Measure(重复测量分析)和Multivariate(多元方差分析)对18个时间点上测量的牦牛体重进行分析,并比较不同时间和不同分组间的差异,为牦牛及相关研究提供另一种数据处理和分析方法.     

Effects of heat treatment on some properties of MDF (medium-density fiberboard)

This work investigated some mechanical, physical and free formaldehyde emission properties of heat-treated MDF. For this purpose, MDF panels were subjected to varying heat treatment temperatures (155°C, 165°C and 175°C), durations (2.5?h., 3.5?h. and 4.5?h.) and waiting times after hot pressing (30?min., 120?min. and 600?min). Thickness swelling (TS), water absorption (WA), free formaldehyde emission (FFE), bending strength (BS), modulus of elasticity (MOE), tensile strength perpendicular to fibers (TSPF) for treated and untreated samples were tested and evaluated statistically. Consequently, after the heat treatment values of tensile strength, bending strength and modulus of elasticity were almost negatively affected relatively, but the thickness swelling and water absorption and quantities of free formaldehyde were improved positively of MDF samples.     

华山松不同部位挥发性单萜烯的含量及其对华山松木蠹象行为的影响

通过GC-MS分析,发现健康的与遭受华山松木蠹象Pissodes punctatus Langor et Zhang危害的华山松Pinus armandii Franch树干以及华山松枝梢释放的挥发性单萜烯在含量上存在较大差别;利用Y-型双向选择嗅觉仪进行的室内趋向反应实验发现,处于补充营养期和交尾产卵期的华山松木蠹象对单萜烯表现出不同的趋向反应。在华山松枝梢挥发物中含量较高的(-)-β-蒎烯、月桂烯和柠檬烯引起补充营养期华山松木蠹象较大的趋向反应;在华山松树干韧皮部挥发物中含量较高的3-(+)-蒈烯则引起交尾产卵期的华山松木蠹象较大的趋向反应。根据试验结果,对华山松和华山松木蠹象互作的机制进行了初步探讨。