Modelling agroforestry systems of cacao (Theobroma cacao) with laurel (Cordia alliodora) and poro (Erythrina poeppigiana) in Costa Rica II. Cacao and wood production,litter production and decomposition

During 7 years (1979–1985) cacao harvests (beans and husks) have been recorded for the agroforestry systems ofTheobroma cacao underCordia alliodora andErythrina poeppigiana shade trees. The mean oven dry cacao yields were 626 and 712 kg.ha⁻¹.a⁻¹ cocoa beans underC. alliodora andE. poeppigiana respectively. Harvests have gradually increased over the years and the plantation has now reached maturity. Annual extraction of N, P, K, Ca and Mg in fruits, which is relatively small, was calculated on the basis of chemical analyses. The following average values were found (kg.ha⁻¹.a⁻¹): At the age of 8 years, theC. alliodora trees have reached 26.7 cm diameter (DBH) and 14.0 m in height. Mean annual growth (from age 5 to 7) is 14.6 m³.ha⁻¹.a⁻¹. Natural plant residue production has been measured for 4 years (Nov. 1981–Oct. 1985). UnderE. poeppigiana it has reached a value of 8.91 t.ha⁻¹.a⁻¹ and underC. alliodora 7.07 t.ha⁻¹.a⁻¹. The shade trees have contributed 57 and 47% respectively. Transference and decomposition rates are high and important in the nutrient cycles. The nutrient content of the litter was analysed and corresponding average yearly transfers were (kg.ha⁻¹.a⁻¹): For part I see Vol. 4, No. 3, 1986. Agroforestry Project, CATIE/GTZ (Tropical Agricultural Research and Training Center/Gesselschaft für Technische Zusammenarbeit), Turrialba, Costa Rica     

论黑皮油松植物景观构成

黑皮油松植物景观是东北地区极具特色的植物景观。黑皮油松姿态俊美强劲,尤其是冬态能充分体现出东北的植物景观特色。松树的栽植在秦朝就已有史料记载,时至今日更是广泛应用于园林景观中。在我国北方地区松树作为长绿树种更是应用广泛。中国人爱松,不仅是爱其苍劲挺拔的姿态,更是对其高尚气节的崇拜和倾慕,松的精神更是人们陶冶情操和品德修养的精神动力。松的景观营造在构成形式法则上,应遵循节奏与韵律、对比与和谐、变化与统一。     

宁夏引黄灌区灌淤土壤磷累积状况及磷肥肥效研究

宁夏第二次土壤普查结果表明,灌淤耕地速效磷含量明显提高,平均含量由1985年的16.3 mg/kg增加到现在28.04 mg/kg.吴忠市利通区东塔乡国家农业科技示范园区磷肥肥效试验研究表明:土壤速效磷含量在50～60 mg/kg高水平下,小麦套玉米施磷效果较低,小麦玉米总产量肥料函数效应达显著水平.施P2O5最大量1...     

施磷量对旱地小麦氮磷钾和干物质积累及产量的影响

针对目前农业生产中存在的施肥增产效应下降问题,研究了磷肥用量对冬小麦养分、氮磷钾和干物质积累及产量的影响,以期为高产高效施肥提供依据.在黄土高原旱地进行田间试验,设不施磷,施磷P2O5 50kg/hm2(不足)、P2O5 100 kg/hm2(适量)和P2O5 150 kg/hm2(高量)4个水平,在不同生长期采样测定...     

陕北不同土地利用类型下土壤无机磷形态分布及有效性研究

采用蒋柏藩-顾益初无机磷分级方法,对黄土高原两种农田土壤剖面(0～100 cm)中无机磷形态分布特征进行了研究.结果表明:两种农田土壤剖面(0～100 cm)中无机磷形态占全磷的90.95%;无机磷又以Ca-P为主,所占比例在87.86%～92.55%之间;糜子地土壤剖面中无机磷总量、Ca2-P、Ca8-P、Al-P和...     

平茬方式对沙柳再萌生能力的影响

研究了不同平茬方式对沙柳再萌生能力的影响,分析了人工镰割、人工锯割、人工刀砍三种平茬方式平茬后的茬口形态及再萌生沙柳的枝条数量、直径、柳条高度。结果表明：最佳平茬方式为人工镰割,其茬口倾斜度最大,茬口背风,有利于茬口防风沙侵袭;平茬后试验区域再萌生枝条数量平均达96.9根,比锯割方式和刀砍方式多出近7根;三种平茬方式对沙柳再萌生枝条直径的影响不大,平均在6～8 mm之间波动;平茬后6～8月份沙柳的生长高度没有明显差异;9月份,镰刀平茬后的沙柳高度优势有所显现,平均值为158 cm。     

单株立木材积测定方法的研究

单株立木材积的测定对林业生产和科学研究工作有着重要的作用,主要的测定方法是通过胸径、树高、上部直径或上部直径的高度来计算干形指数,然后计算单株立木材积。而不同的方法所用上部直径不同。本文用5个树种的解析木,分别对较常见的5种测定方法的测定精度进行了研究。得出的结论为:3/4形点法、0 5形点法、胸高形率法精度较高,绝对形率法、望高法精度较低。建议对干形饱满的树种采用3/4形点法、0 5形点法;对干形尖削的树种采用0 5形点法、胸高形率法。     

南京中山陵风景区常绿阔叶树种引进及风景林林相改造技术的研究

根据中山陵风景名胜区森林景观建设的需求和遭受松材线虫病危害，严重影响着森林景观的现状，在遭受松材线虫病危害的松林及杂阔林内应用“林下补阔技术”，引进了若槠、香樟、石楠、大叶女贞、木荷、海桐、乐昌含笑和深山含笑等常绿阔叶树种，进行常绿阔叶树与松树、常绿阔叶树与落叶阔叶树异龄复层混交，以形成较稳定的含常绿树种成分的复层混交森林群落，增加树种的多样性，丰富森林绿景，改善林相结构，进一步提高森林生态系统的稳定性和景观质量。并为风景林林相改造研究出了常绿阔叶树种深山含笑、乐晶含笑异地扩大繁殖播种育苗技术，为林相改造提供了造林新树种。     

Scion-rootstock relationships with respect to height growth and foliar concentrations of nitrogen and phosphorus in reciprocal grafts of Pinus caribaea var. hondurensis

Both scion and rootstock clones significantly influenced scion elongation and concentrations of nitrogen and phosphorus in the scion foliage. Scion clone was the more important determinant. Scion clone × rootstock clone interactions were not significant. The ability of a clone to elongate as a scion was not correlated with its capacity to promote or retard scion elongation when used as a rootstock. Genetic differences in foliar nutrient concentrations appeared to reflect levels of nutrient demand, rather than the ability of roots to absorb nutrients. Nutrient demand of the rootstock can also explain negative correlations between nitrogen levels in rootstock clones and levels of both nitrogen and phosphorus in the scions. There was no significant relationship between scion elongation and foliar nitrogen concentrations of either rootstock or scion. The weak relationship between scion elongation and concentration of phosphorus in the rootstock apparently resulted from tissue dilution.     

中小跨径弯斜桥的几何设计探讨

弯斜桥梁的几何设计思路是影响设计、施工的重要因素，文中提出了桥梁受公路线形制约时的几何布置形式，公路弯斜桥几何设计的特点、类型、方法和影响因素。在不增加设计难度的情况下，通过桥梁的几何布置达到改善公路线形的目的。结合黑龙江省望奎至灵山乡公路桥梁设计的实例加以说明。