可编程控制器PLC在跳汰机风阀控制中的应用

介绍由可编程控制器PLC控制的跳汰机风阀控制系统,详细叙述了风阀自动控制的思想,以及各种跳汰参数的调整方法。     

Effects of a severe typhoon on forest dynamics in a warm-temperate evergreen broad-leaved forest in southwestern Japan

The effects of a typhoon on forest dynamics and the response of major tree species were studied in a warm-temperate evergreen broad-leaved forest in southwestern Japan. The strongest typhoon on record (T9313) passed through this region in 1993. Return periods of typhoons over 30 ms⁻¹ in instantaneous wind velocity and T9313 were estimated to be 2.2 and 104.5 years, respectively. Approximately 10% of all stems suffered some damage from T9313 and annual stem mortality rose from 1.3 to 2.7%. The estimated period that the number of stems would fall below 10% of the initial was four years shorter with T9313-class typhoons than without them. Thus, the disturbance by T9313 was not catastrophic at the site although T9313 was an episodic typhoon. The short-term responses of major tree species to T9313 were classified into four types: 1) blunt-response type with little decrease and recruitment of stems in the DBH ≥ 5 cm class (Distylium racemosum), 2) retreat type with larger decrease than recruitment (e.g. Quercus acuta), 3) sharp-response type with a large decrease and much recruitment (e.g. Cinnamomum japonicum), and 4) advance type with less decrease than recruitment (Eurya japonica). Among the four regeneration types classified by previous studies (climax, light-demanding, subcanopy, and few-sapling), the climax and few-sapling types each showed a specific short-term response, the blunt-response and retreat types, respectively, that explains one aspect of the regeneration strategies of each type. On the other hand, the light-demanding or sub-canopy type showed multiple short-term responses, indicating that each regeneration type contains species with various regeneration strategies. In this paper, I analyzed data from the database that was compiled by the Aya Research Team.     

四季竹发笋及幼竹高生长规律研究

研究表明:四季竹发笋期在4月下旬至10月下旬,6月发笋数最多,9月次之。6月出笋占总出笋棵数的35.56%,笋重量占总重的39.14%;9月出笋占总出笋棵数的20.78%,笋重量占总重的17.83%。四季竹幼竹高生长表现为生长初期和后期相对缓慢,整个生长期平均日生长量12.7 cm。生长高峰在笋出土后第15~35 d,平均日生长量19.2 cm,最大日生长量25.4 cm。四季竹日高生长量方程式为y=-3.785 5 1.791 8 t-0.018 t2-0.000 5 t3。     

整地方式对杉木生长和经济效益的影响

用４种不同整地方式１７ａ的试验资料，分析了整对林木各种生长的影响；用帖现方法，比较了不同整地方式的经济效益。结果表明：整地方式对杉木各种连年生长的量的影响，一般在７－１０ａ消失；对平均高，胸径和单株材积的影响，主要箐面在１０－１２ａ前，在７－１０ａ差异最大；整地对胸径的影响比对高树高和单株积的影响短１－２ａ。     

辽宁引种班克松优良家系的苗期试验研究

文章通过对从北美加拿大引进的2个种源48个班克松优良家系的苗期研究,结果表明,48个班克松家系苗高、地径生长差异极显著,多重比较后入选的最优家系均来自北纬46°的Sturgeonlake种源,生长最差的班克松家系均来自北纬45°10′的Bancraft种源。本项研究可为科学地从国外引进优良班克松家系、建立优良的种子园提供参考和做好准备。     

毛竹笋用林合理竹龄结构及其笋期生长规律

通过多年不同毛竹林分观测分析,提出2度竹的比例在一定范围内影响着笋用林的产量。分析丽水市郊山地笋用林盛期出现的时间及其发生规律,认为笋用林笋期生长规律和气象因子关系密切,丽水市郊的山地笋用林通常是在3月下旬至4月上旬为出笋盛期。对刚露箨叶至出土后10天的笋个体分析表明,对单支笋重的影响长度比笋径大,留笋时间的长短对产量有决定性影响,但从营养成分、加工适性等方面考虑,以笋刚出土时挖掘为最适时期,此时,笋长与笋径相关极显著。     

不同覆盖物对雷竹林笋生产的影响*

采用随机区组设计，研究了８种覆盖物对林地土壤温度的调节和对雷竹林笋期、笋产量及竹林经济收益的影响。结果表明，８种覆盖物均提高了林地土壤温度，提早了始笋期，延长了产笋期，增加了竹林的笋产量与产值。经综合评定，若糠覆盖为最佳处理，与对照相比，其试验林地表层土壤（０～２５ｃｍ）温度提高３．８３℃，始笋期提早４１ｄ，笋期延长４０ｄ，产量、产值和纯收益分别增长２９．４％、２７０．３％和３１０．２％。     

Productivity of intensified crop—fallow rotations in the Trenbath model

Management of crop—fallow rotations should strike a balance between exploitation, during cropping, and restoration of soil fertility during the fallow period. The Trenbath model describes build-up of soil fertility during a fallow period by two parameters (a maximum level and a half-recovery time) and decline during cropping as a simple proportion. The model can be used to predict potential crop production for a large number of management options consisting of length of cropping period and duration of fallow. In solving the equations, the model can be restricted to sustainable systems, where fallow length is sufficient to restore soil fertility to its value at the start of the previous cropping period. The model outcome suggests that the highest yields per unit of land can be obtained by starting a new cropping period after soil fertility has recovered to 50–60% of its maximum value. This prediction is virtually independent of the growth rate of the fallow vegetation. The nature of the fallow vegetation (natural regrowth, planted trees, or cover crops) mainly influences the crop yield by modifying the required duration of fallow periods. Intensification of land use by shortening fallow periods will initially increase returns per unit land at the likely costs of returns per unit labor. When fallows no longer restore soil fertility to 50% of the maximum, overall productivity will decline both per unit land and per unit labor, unless external inputs replace the soil fertility restoring functions of a fallow.This revised version was published online in November 2005 with corrections to the Cover Date.     

观光木播种苗生长规律及育苗技术研究

用有序样本聚类分析法将观光木1年生播种苗生长过程划分为4个时期:出苗期(2月26日-5月20日)、幼苗期(5月21日-7月20日)、速生期(7月21日-10月20日)和生长后期(10月21日-11月20日)。不同播种期的试验表明:冬播观光木比春播提早16 d萌发,苗高、地径生长量和总生物量分别比春播提高13.3%、15.1%和18.8%。采用沙藏可促进种子提早萌发和提高场圃发芽率。不同密度试验表明,观光木育苗采用60株.m-2的密度较好。     

三尖杉不同种源苗期生长性状分析

研究了14个三尖杉种源和篦子三尖杉苗期的生长情况,结果表明,三尖杉和篦子三尖杉幼苗生长曲线均趋直线,整个生长过程中没有明显的停滞期;14个三尖杉种源和篦子三尖杉生长曲线可分为Ⅰ、Ⅱ两种类型,其中江西崇义、上饶,福建明溪,安徽黄山,广东午远5个种源1年生苗生长曲线属Ⅰ型,该类型整个生长期生长较快,但在前期生长较缓慢,后期有一明显相对生长迅速期;江西修水、井冈山,贵州黎平、从江,云南石屏,河南洛阳,四川峨嵋,湖南绥宁,湖北恩施9个种源1年生苗生长曲线属Ⅱ型,其整个生长期生长速率均保持在一个比较低的水平,没有明显可区分的相对生长迅速期;篦子三尖杉生长曲线接近Ⅱ型,介于不同种源三尖杉之间。对14个三尖杉种源和篦子三尖杉1年生苗生长量进行方差分析,结果表明,三尖杉种源间幼苗生长量存在极显著差异,种源与试验地的交互作用也存在极显著差异,不同种源间的苗高生长差异较大,生长量最大的为安徽黄山种源,1年生苗高为18.60 cm,生长量最小的为湖南绥宁10.90 cm,篦子三尖杉1年生苗高生长量为11.00 cm。