Power-law behaviour and parametric models for the size-distribution of forest fires

This paper examines the distribution of areas burned in forest fires. Empirical size distributions, derived from extensive fire records, for six regions in North America are presented. While they show some commonalities, it appears that a simple power-law distribution of sizes, as has been suggested by some authors, is too simple to describe the distributions over their full range. A stochastic model for the spread and extinguishment of fires is used to examine conditions for power-law behaviour and deviations from it. The concept of the extinguishment growth rate ratio (EGRR) is developed. A null model with constant EGRR leads to a power-law distribution, but this does not appear to hold empirically for the data sets examined. Some alternative parametric forms for the size distribution are presented, with a four-parameter ‘competing hazards’ model providing the overall best fit.     

五爪金龙凋落叶腐解物的化感潜力研究

采用莴苣种子为受体,测试了五爪金龙凋落叶早期腐解物的化感作用,并与其鲜叶及凋落叶的化感潜力进行了比较分析。结果如下:凋落叶40d的腐解物、鲜叶及凋落叶的水提取液均具有较强的化感潜力,并表现出低促高抑的浓度效应,在FW0.1g﹒mL-1高质量浓度下的综合化感抑制强度为凋落叶未能加土壤的腐解物>鲜叶>凋落叶加土壤的腐解物>凋落叶,而在FW0.005g﹒mL-1低质量浓度下的综合化感促进作用是凋落叶>鲜叶>凋落叶加土壤的腐解物>凋落叶未加土壤的腐解物。鲜叶的抑制强度较凋落叶的大,表明叶片在衰老过程中抑制作用减弱。凋落叶未加土壤仅在空气微生物作用下的腐解物抑制作用最强,促进作用最小,而加入土壤后在土壤微生物作用下的腐解物的抑制作用却有所减弱,抑制强度介于鲜叶和凋落叶的之间,促进作用却小于鲜叶和凋落叶,说明凋落叶腐解过程中微生物的参与对化感作用产生了复杂的影响。     

我国纺织行业上市公司资本结构实证研究

资本结构是企业筹资的核心问题之一,上市公司资本结构是否合理直接关系到其企业价值最大化的实现.以纺织行业上市公司公开数据为样本,运用回归分析方法,分析影响我国纺织行业资本结构的因素,认为:资本结构与企业获利能力、资产担保价值正相关,与企业规模负相关,与成长性、实际税率相关不明显.     

Increased energy expenditure due to increased territorial defense in male lizards after phenotypic manipulation

Fitness tradeoffs are difficult to examine because many fitness variables are correlated and vary in the same direction. Phenotypic manipulation circumvents many of these difficulties, and here we used this technique to examine mechanisms for tradeoffs between increased aggression (territorial defense) and survivorship. The behavioral phenotype of male mountain spiny lizards (Sceloporus jarrovi) was manipulated with testosterone to increase territorial defense, a sexually selected trait. We previously demonstrated that increased territorial defense results in a decrease in survival caused by a lower ratio of energy intake to energy expenditure. Here we measured energy consumption of increased territorial aggression using the doubly labeled water technique in the field and compared males with and without testosterone implants (Fig. 1). In a supplementary study we measured standard metabolic rate using captive lizards given similar testosterone implants to examine if an increase in energy expenditure was a result of only an increase in standard metabolic rate (Fig. 3). Our results indicated that a primary contribution to tradeoffs between increased territorial defense and survivorship could be made by a 31% increase in energy expenditure in the field that is not due to an increase in standard metabolic rate.     

浙江天台山茶树光合日变化及光响应

自然条件下使用LCA－4型便携式光合测定系统研究了栽培天天台山主峰华顶山的茶树连体叶片的光合日变化及光响应。结果表明：在初夏晴天,上年越冬叶片（下称二年生叶）的光合速率,表观量子效率,羧化效率和饱和光强比展叶红16d的一年生叶高,CO2补偿点和光补偿点比一年生叶低,两者的净光合速率日进程曲线均为“双峰”型,午间胞间CO2浓度上升表明,此时净光合速率下降主要受非气孔限制因素的影响。一年生叶蒸腾速率高于二年生叶,它们日进程曲线为单峰河,午间最高,而气孔阻力进间最低。不同时段作光响应和CO2响应试验表明,上午茶树的表观量子效率,饱和光强和羧化效率较高,光补偿点和CO2补偿点较低。图3表4参26     

土壤水分对沙棘成活率及抗逆生理特性的影响

为提高沙棘在滩涂区，半干旱区造林的成活率，对不同土壤水分下沙棘的生理学特性进行了分析。结果表明：（1）在不同土壤水分处理下，随土壤含水量降低及处理时间的延长，沙棘叶片脯氨酸（Pro)含量升高，POD活性增强，可溶性糖含量升高；水淹情况下，沙棘叶片Pro含量明显上升，POD活性增强，可溶性糖含量升高。（2）土壤含水量在15%-30%之间，沙棘苗木成活率最高（100%），生长最好；35%和40%处理下，沙棘苗木成活率较高（66.7%)，生长良好；5%，10%处理水平和水淹情况下，沙棘苗木成活率低（33.3%)，生长不良，（3）不同处理下，随土壤含水量的降低，沙棘叶片的相对电导度增大，沙棘受伤害的程度加剧，且淹水对沙棘的伤害最重。     

柠檬醛对赤子爱胜蚓(Eisenia fetida)再生的影响

用不同浓度柠檬醛处理不同部位剪切的蚯蚓,和处理剪切后不同时间段的蚯蚓体段,探讨了柠檬醛对赤子爱胜蚓再生作用的体段、作用浓度和敏感时间段.结果表明,柠檬醛对蚯蚓再生有明显影响,但这种作用依不同体段而异,以体段P7和P25作用最显著,而A25,A90和P60的受柠檬醛影响较小; 柠檬醛影响蚯蚓头部再生,而不影响尾部再生;对再生有影响的柠檬醛浓度为1mmolkg-1, 0. 1mmolkg-1和0. 01mmolkg-1 (土壤),对蚯蚓再生作用的时间为切后0. 5~1d.试验显示,柠檬醛干扰蚯蚓再生头部形成而且还影响再生头尾体轴形成;内源视黄酸在蚯蚓头尾轴再生图式形成中有重要作用. 图4表4参18     

用黑麦幼苗法测定土壤中污染元素的生物有效性

本文对全国污灌区１２个土样中Ｃｄ形态与生物有效性的试验表明，Ｃｄ的交换态，吸附态，有机结合态均有效，且有机结合态最为有效，对紫阳县富硒土壤的试验表明：黑麦幼苗中的总Ｓｅ量与０．１ｍｏｌ／１ＫＨ２ＰＯ４的浸提量最为相关，从而推荐该法为酸性土壤有效Ｓｅ的浸提方法，对西安污水厂污水污泥在娄土上不同施用量的试验表明：幼苗中Ｎ，Ｐ随施用量增加而增加，Ｎ，Ｐ的有效率分别为５０－７０％及１５－２８％；黑麦幼苗中     

铁聚合反应速率研究

研究了聚合硫酸铁絮凝剂制备中亚铁的氧化反应速率，证明该速率对Ｆｅ＾２＋为零级，对ＮＯ２（ｇ）为一级，因此提高气相中ＮＯ２的分压可大大缩短制备时间。     

水中氨氮挥发影响因素探讨

本文介绍了水中氨氮挥发的影响因素。水中氨氮挥发速率常数随水的ｐＨ值和水温升高而增加，水面风速大则常数值也大，大气压高的地区的挥发速率常数小于大气压低者。与蒸馏水体系相比，在实验条件相同时滇胡水中氨氮挥发速率常数小。