Soil-released carbon dioxide from microbial biomass carbon in the cultivated soils of karst areas of southwest China

 Soil microbial biomass and the emission of CO₂ from the soil surface were measured in yellow soils (Ultisols) of the karst areas of southwest China. The soils are relatively weathered, leached and impoverished, and have a low input of plant residues. The measurements were made for a 1-year period and show a reciprocal relationship between microbial biomass and surface CO₂ efflux. The highest (42.6±2.8 mg CO₂-C m^–2 h^–1) and lowest (15.6±0.6 mg CO₂-C m^–2 h^–1) CO₂ effluxes are found in the summer and winter, respectively. The cumulative CO₂ efflux is 0.24 kg CO₂-C m^–2 year^–1. There is also a marked seasonal variation in the amount of soil microbial biomass carbon, but with the highest (644±71 μg C g^–1 soil) and lowest (270±24 μg C g^–1 soil) values occurring in the winter and summer, respectively. The cumulative loss of soil microbial biomass carbon in the top 10 cm of the soil was 608 μg C g^–1 year^–1 soil over 17 sampling times. The mean residence time of microbial biomass is estimated at 105 days, suggesting that the carbon in soil microbial biomass may act as a source of the CO₂ released from soils. Received: 13 July 1999     

Analysis of the distribution of endemic and rare arthropods in high endemism areas of Algarve-South Portugal

The study of several arthropod groups in high endemism areas (HEA) of Algarve, the Southernmost province of Portugal, has revealed endemic species and species not yet recorded for the Portuguese fauna. The list includes 3 species of Isopoda endemic to Algarve, to Portugal or to the Iberian Peninsula, 2 species new to Portugal and 2 species new to the Iberian Peninsula; 2 species of Pseudoscorpiones not yet cited to Portugal; 11 species of Pauropoda new to Portugal, including one new species probably endemic; 15 species of Collembola endemic to the Portuguese or to the Iberian Peninsula faunas (Gama et al. 1997) and 37 species and 5 subspecies of Staphylinidae endemic to Algarve.With the exception of Collembola, which have been studied by us, the remaining groups have been submitted for study to several specialists.These findings heighten the biological richness of these areas of high endemism in terms of conservation of biological diversity. The authors draw attention to the necessity to preserve or restore the biological value of these areas, encouraging the adoption of protective measures and the creation of research programmes that include the implementation of taxonomic studies and co-operation between taxonomists and ecologists in order to preserve the biodiversity of these areas.     

对双鸭山林区森林分类经营的认识

本文对双鸭山林区森林的分类经营提出了几点认识,并做了具体分析。     

辽东山区天然次生林经营现状,存在问题及对策

文章对辽东山区天然次生林经营现状及在生产中存在的主要问题进行了分析、探讨,并就现有的天然次生林中亟待解决的问题提出了几点参与意见,即增强资源与环境意识;实和行森林分类经营;利用天然林环境优势,发展多种经营;停止皆伐,栽针保阔;采取长轮伐期作业,培育大径材;进行封山育林。     

太行山石灰岩低山区水土保持防护林高效空间配置研究

运用层次分析法（Ａｎａｌｙｔｉｃ Ｈｉｅｒａｒｃｈｙ Ｐｒｏｃｅｓｓ,简称ＡＨＰ）对太行山石灰岩低山区水土保持防护林体系林种结构、树种配置优化进行判断。结果表明,该区水土保持林以生态效益为主,兼顾经济效益和社会效益;以山坡水土保持林为主,多林种多树种结合,山坡水土保护林、梯田经济林、山顶防护林、沟头防护林、沟底防护林、沟边固岸林的比例分别为２８．６％、１８．２％、１７．５％、１７．４％、１０．３％     

小麦玉米轮作区不同用药方式防治灰飞虱及玉米粗缩病的研究

通过小麦用药、小麦和玉米均用药、玉米用药 3种不同用药方式防治灰飞虱和玉米粗缩病的试验 (各用药方式之间差异达极显著水平 )表明 ,在小麦玉米轮作区 ,小麦和玉米田均用药是最佳的防治措施。     

黄土高原主要造林树种集流面积的确定

采用人工供水的方法,研究了油松、侧柏、刺槐人工幼林林地土壤水分年变化规律.根据土壤水分对林木的有效性,提出了人工林土壤水分的补偿方法及各树种的集流面积.结果表明,在3个树种中,刺槐林地的难效水频率最高,侧柏的最低.初步提出了在黄土高原年降水量500～600 mm的地区,20 a生油松和侧柏适宜的集流面积分别为10～12 m2/株和5～9m2/株,8 a生刺槐为12～20 m2/株,年降水量400～500mm的地区,油松和侧柏人工林集水面积至少应为12 m2/株和9 m2/株,刺槐20m2/株.     

马铃薯平衡施肥中的钾素效应研究

在贵州高海拔地区织金县采用马铃薯高产栽培技术和平衡施肥技术,马铃薯产量为14.91t/hm2,超过当地平均产量1.5倍,钾肥配施可增产马铃薯1.0~2.5t/hm2,增幅8.06~20.63%,施钾产投比可达2.0~3.5。施钾肥后马铃薯薯块重量增加19.2%,增产以增加薯块重量为主,马铃薯品质有较大改善。试验认为,高产高效施肥的N:K2O比为100:（95~140）为宜,即施氮（N）105kg/hm2,施钾（K2O）100~150kg/hm2为宜。     

农地重划区植栽绿化调查探讨

1992年以前台湾办理农地重划区或早期农地重划区农水路更新改善工程中,均着重在生产、生活上,之后逐渐重视生态功能之表现,至1996年增加植栽绿美化项目,最近五年方有生态工法。研究作现场勘查后,针对办理重划人员（专家）及农民作问卷调查,对于实施绿美化工作之相关认知及目前遭遇问题作一统计分析与评估,所得结论如下:（1）对于绿美化之优点,如改善环境品质美观、树荫制造休憩及调节湿度等,受测者表示在普通（同意）以上均占85%（65%）以上。（2）受测者五成以上同意本问卷所设计数种植栽配置方式,如利用树冠较小之树种、灌木或增加栽植间距。（3）大多数之农民及专家对于植栽绿美化工作持正面态度,即期望继续推行,且农民认为应该继续施行的意愿较专家为高。     

沙区城市园林绿化建设初探—以酒泉市肃州区世纪大道设计为例

在对沙区城市气候特征充分了解的基本上,提出了沙区气候环境对沙区城市园林绿化的特殊要求,即降低风速、阻挡沙尘、湿润空气和调节气温。沙区城市园林绿化应遵循的主要原则是,主要街道与主害风向要有最大的夹角,林园、植物园、公园设置在上风向,主要街道上设置开放式街道公园和节水设计。其关键技术是树种的选择和结构配置。恶劣的沙区气候环境决定了沙区城市园林绿化比其他城市的园林绿化显得更为重要。第1期常兆丰沙区城市园林绿化建设初探