半干旱地区八种杨树无性系间苗期净光合速率变化的研究*

辽宁省建平县半干旱地区不同来源的８种杨树无性系净光合速率（Ｐｎ）达到了显著和极显著的差异水平，无性系间的净光合速率可分为高中低三个类群，即：昭林场６号、群众杨、赤峰杨３４号、欧症状杨４７、小黑肠、小青杨、帝国杨５１号、欧美杨６４。具高光合速率的昭林场６号，受光量作用大，但受湿度、空气蒸汽压影响小，适应于具有干热天气的半干旱地区；而低光合类群的三个无性系则不同，其中欧美杨６４一直与光、湿度和蒸汽压的     

基于原野服务器的远程树木直径测定的研究

以卫星遥感为主的资源环境监测,由于受云层分辨率等限制,一直以来其应用重点主要在"监"上,本文介绍一种近年来刚刚兴起的能够进行远程监、控、测集网络与传感器于一身的结合体--原野服务器.首先对其定义、种类、外业设置及远程监控操作做了简单的介绍,然后尝试利用原野服务器传回的图像,通过立体视觉技术重建远隔地树木的胸径,得到了较为满意的结果,从而实现了不到现地便能够测量直径的目的.     

中国木材市场供给结构分析

文内首先对我国木材市场的变化进行了简单回顾，并从计划内产量、计划外产量、非单板型人造板产量以及木材净进口量四个方面，对我国木材市场供给结构进行了分析；最后，针对我国木材市场供给结构的现状，对其进行了发展趋势分析。     

四种常绿植物蒸腾速率、净光合速率的日变化及对环境的影响

4种常绿植物的蒸腾速率日变化呈单峰曲线,蒸腾速率的峰值和均值均以珊瑚树为最高,海桐和桂花次之,大叶黄杨的峰值和日均值最低,与4种植物的自由水含量的高低顺序一致。Pn的日变化呈双峰曲线,峰值分别出现在10时和14时左右,两峰间低谷值出现在12时左右,第1次峰值大于第2次峰值;其中以海桐的峰值和日均值最高,以大叶黄杨最低;光合能力的高低,与不同植物叶绿素的含量以及光补偿点和光饱和点有关。4种植物树冠内温度以海桐最低,吸尘能力以珊瑚树最强。树冠周围的湿度与蒸腾速率的变化一致,CO2含量与光合作用的大小呈反比,二者均与大气呈显著差异。     

晚大新高梨的净光合速率变化规律初探

利用LI-6400便携式光合测定系统对晚大新高梨进行叶片净光合速率测定研究,结果表明,净光合速率日变化在4、5月份为单峰型,在6、7月份为双峰型,年变化为双峰型。净光合速率Pn在光强为18-1 476 μmol·m-2·s-1时随光强的增强而增大, 净光合速率Pn在CO2浓度为31-963 μmol·mol-1时随CO2浓度的增大而升高,叶片在展叶后23 d内,净光合速率Pn呈上升趋势,23 d后Pn值略有下降,然后趋于稳定。不同部位叶片的净光合速率Pn相比,树冠外围中部最高,下部最低。     

在CO2浓度加富条件下马尾松针叶的生理生态响应

研究了在3种不同CO2浓度(360 μmol·mol-1、800 μmol·mol-1、1 200 μmol·mol-1)下马尾松针叶的净光合速率、蒸腾速率、气孔导度、水分利用效率的变化.结果表明:在当前CO2(360 μmol·mol-1)浓度下,当光强为1 000 μmol·m-2·s-1时,净光合速率、蒸腾速率、气孔导度分别为3.46 μmol·m-2·s-1、0.273 mmol·m-2·s-1、0.0254 mmol·m-2·s-1,针叶的光饱和点和光补偿点分别为:(1 800±2) μmol·m-2·s-1和(24±2) μmol·m-2·s-1.当CO2加富到1 200 μmol·mol-1时,针叶的光饱和点降低了200 μmol·m-2·s-1,而光补偿点增加了4 μmol·m-2·s-1.在光照强度为50～2 000 μmol·m-2·s-1的条件下,不同CO2浓度下的水分利用率平均值分别为:1 200 μmol·mol-1浓度下的19.163 μmol·mmol-1,800 μmol·mol-1浓度下的12.912 μmol·mmol-1,360 μmol·mol-1浓度下的11.192 μmol·mmol-1.短期的CO2加富降低了植物叶片的蒸腾速率、气孔导度,而植物的水分利用效率则上升.     

Productivity and profitability of multistrata organic versus conventional coffee farms in Costa Rica

In areas where traditional multistrata coffee systems have been transformed to systems with patchy or no shade at all, often dependent on high chemical inputs, ecological and socioeconomic degradation has become an increasing issue. During the 1990s, rising environmental and health concerns have promoted the interest in organic production systems and their environmental services for natural resource conservation. This study compared productivity, profitability, producer-defined constraints, and goals and research priorities between ten individually paired organic and conventional coffee farms in Costa Rica. Although five of the organic farms matched or exceeded the production of their conventional counterparts, the three-year mean yield of the organic farms as a group was 22% lower than that of the conventional farms. However, excluding organic certification costs, mean variable costs and net income (NI) were similar for both groups, mainly because organic price premiums received by the farmers compensated for lower yields. If current organic certification costs are included, the price premiums paid to organic producers would have to increase to 38% in order to equal the NI from conventional coffee. Conventional farmers indentified low and unstable prices as the main constraints to sustained production and stated further intensification of production as their main goal. In contrast, the key issues for future development of the organic group centered on farm diversification, agroecological self-sufficiency, and agronomic practices that permit organic farm management. This revised version was published online in June 2006 with corrections to the Cover Date.     

热带山地雨林生态系统水文化学循环规律的研究

根据５ａ定位观测，对尖峰岭热带山地雨林更新林生态系统的水文化学循环规律的数据分析表明，年均降雨量为２６６８．３ｍｍ，其中总径流量占４６．７％，蒸散量５３．３％，冠层截留量１４．０％。Ｎ、Ｐ、Ｋ、Ｃａ、Ｍｇ的年均降雨输入量为７８．４ｋｇ／（ｈｍ２·ａ），总径流输出５６．７ｋｇ／（ｈｍ２·ａ），净积累２１．６ｋｇ／（ｈｍ２·ａ）；Ｓｉ、有机Ｃ、Ａｌ、Ｍｎ的年均降雨输入量为２５．０ｋｇ／（ｈｍ２·ａ），总径流输出为１１２．３ｋｇ／（ｈｍ２·ａ），净损失８７．３ｋｇ／（ｈｍ２·ａ），更新林系统仅处于更新进展过程中，同时证实了冠层对降水化学的淋溶效应，净淋溶系数达４．１１；提出了降雨、林内净降雨、总径流的各水化学物含量与其相应水量的回归模式     

Agronomic and economic appraisal of alley cropping with Leucaena diversifolia on an acid soil in the highlands of Burundi

Although alley cropping has been shown elsewhere to permit continuous cropping, it has not been widely tested in the highlands of east and central Africa where it has the additional potential of controlling soil erosion. The effect of four rates (0, 30, 60 and 90 kg N ha^–1) of inorganic N on the performance of alley cropping using Leucaena diversifolia as the hedgerow species was studied in the central highlands of Burundi. Significant increase in maize yield (average of 26%) due to alley cropping was only first realised in 1992, three years after the commencement of the trial. In 1993, the average yield advantage of the alley cropping plots was 21%. The prunings augmented the response of maize yield to inorganic N in 1992 and 1993. Compared with the control, economic benefits over the five-year period for all the treatments were negative.     

尾叶桉幼林地上部分生物量及养分循环的研究*

论述了２－３年生尾叶桉幼林地上部分生长、生物量积累和生物量在树木各器官及各径阶中的分配，林分净生产量，树木各器官及凋落物的养分含量和林分的养分循环。２年生时林分的生物量为２２．９ｔ／ｈｍ＾２，其中干材占６０．２％，皮占８．９％，枝占１４．７％，叶占１６．２％。３年生时林分生物量为４０ｔｈｍ＾２，其中干材占６３．６％，皮占７．７％，枝占１４．１％，叶占１４．６％。年净生产量为２０．５ｔ／ｈｍ＾２，约