Vertical profiles of environmental factors within tropical rainforest, Lambir Hills National Park, Sarawak, Malaysia

Environmental factors, such as global solar radiation, wind speed, air temperature, humidity, and CO₂ concentration, were measured above and within the canopy of a tropical rainforest in Lambir Hills National Park, Sarawak, Malaysia. Few data concerning the environment of this forest have been reported. Intensive observations were carried out in 1998, 1999, and 2000 with the following results: (1) The fraction of global solar radiation reaching the upper layer of the canopy varied with global solar radiation above the canopy. Even though the global solar radiation above the canopy fluctuated, the fraction of that reaching the lower canopy and the ground was constantly approximately 5%. (2) The fraction of wind speed reaching each layer of the canopy increased with wind speed above the canopy. Little wind was usually present at the lower canopy. (3) The daytime air temperature at the canopy top was higher than that near the ground. The maximum difference between the air temperature at the canopy top and that at the ground was about 5°C, and the diurnal temperature ranges at the canopy top and those at the ground were about 8°C and about 5°C, respectively. The highest daytime water vapor pressure occurred within the canopy and particularly near the ground. Vertical gradients of water vapor pressure during the day were steep, probably because of high transpiration. (4) In the 1998 observation the minimum and the maximum CO₂ concentrations were 360 ppm in the day and 450 ppm at night, while in the 2000 observation the minimum and the maximum CO₂ concentrations were 350 ppm in the day and 540 ppm at night. The higher CO₂ concentration in the daytime and the lower concentration at night observed during the 1998 observation period were probably due to reduced photosynthesis and soil respiration caused by exceptional dry conditions during the observation period.     

陕北"一户一田"和"一组一田"耕地细碎化整治模式与绩效评价

耕地细碎化是当前制约中国农业现代化发展的重要因素,如何解决耕地细碎化问题已经成为推动小农户和现代农业有机衔接的必然路径。该研究基于实地农户调研数据和半结构访谈内容,对陕北榆林市榆阳区首创的"一户一田"和"一组一田"2种耕地细碎化整治模式进行系统剖析,并采用双重差分(Difference-in-difference, DID)模型定量分析2种模式的绩效差异。研究发现:1)"一户一田"模式是农民自发的产权重组和分散流转,并与政府支持的土地整治项目叠加与综合;"一组一田"模式是一种"以家庭承包经营为基础、统分收放自如的双层经营体制"创新模式,也是产权改革、统分流转、土地整治与统分经营管理的有机结合。2)"一户一田"和"一组一田"两种模式均能有效解决耕地细碎化问题,显著增加耕地面积,实施后耕地面积增加率分别为6.02%和57.58%;同时也使得农业机械化水平有所提高,显著提升农业生产效率与作物产量,作物产量增加率分别为12.54%和19.87%,"一组一田"提升更为明显。3)2种模式均有利于提高农户收入,"一户一田"主要是通过增加农业种植收入来提高总收入;"一组一田"对农户收入提升更加显著,除增加农业收入外,也通过产业转型增加了务工收入。与"一户一田"模式相比,"一组一田"模式更能够促进集中连片、规模扩大、设施完善、经营现代化的高标准农田建设。为解决耕地细碎化问题,应加强政策引导和支持,挖掘村内能人价值,明晰合作社、分社和农民的责、权、利关系等,促进小农户和现代农业发展有机衔接。     

Can plot edge bias be reduced by means of airborne laser scanning?

This paper presents new methods for plot edge bias (PEB) correction of individual tree competition indices (CIs) using airborne laser scanning (ALS) as auxiliary information in multivariate ratio and multivariate regression models. I applied the methods to 557 plots from the Norwegian National Forest Inventory located in Hedmark County in South East Norway and compared them to the benchmarks methods linear expansion and simulated annealing by studying the individual tree growth predictions before and after PEB correction. Generally, the simulated annealing method seemed to improve growth prediction most and overall the existing methods performed better than those based on ALS. All PEB-correction methods tested gave minor changes in growth predictions and the absolute change in percent in adj. R² and Akaike's Information Criterion (AIC) was numerically small, with an average percentage change for the tested CIs between 1.8 for adj. R² and 0.6 for AIC of the observed values in the original data. The small differences in the results between the original data and the PEB-corrected data show that on average PEB remains a minor problem for individual tree growth prediction. Whether the results are valid for forests with significantly different spatial composition than that of this database remains to be confirmed.     

Effects of adjuvants on deposition efficiency of fenhexamid sprays applied to Chardonnay grapevine foliage

Adequate spray deposition on susceptible grapevine tissue is an essential requirement for effective chemical control of economically important diseases, such as grey mould, powdery mildew and downy mildew. The objective of this study was to evaluate the potential of some agricultural adjuvants to improve foliar spray deposition. Deposition quantity and quality was assessed by means of a spray assessment protocol using fluorometry, photomicrography and digital image analyses. The visual droplet rating technique developed by G Furness, Australia, was also included in initial assessments. Both assessment protocols showed that spray deposition quantity increased with increasing spray volume applications of 27 l ha⁻¹ to 581 l ha⁻¹ with a motorised backpack mistblower, but decreased at 698 l ha⁻¹, possibly due to run-off. Addition of selected spray adjuvants at 526 l ha⁻¹ volume demonstrated improved deposition quantity and quality. Agral 90 (ethoxylated alkylphenol), BB5 (acidifier), Nu-film-P (terpene oil), and Solitaire (silicone/plant oil) significantly improved deposition on upper and lower leaf surfaces compared with the fenhexamid-only and water sprayed control. Break-thru S240 (organosilicone) and Villa 51 (alkylpolyethylene glycol ether) did not improve deposition quantity, although remarkably better deposition quality was obtained. An adjuvant concentration effect (within the registered concentration range) was evident at spray volumes of 502 l ha⁻¹, especially those retained on the upper leaf surfaces. Agral 90 and Nu-film-P effected significant improvement of spray deposition at the higher concentrations (18 ml and 50 ml hl⁻¹, respectively), but not at the lower concentrations (6 ml and 20 ml hl⁻¹, respectively). Solitaire improved deposition at the lower concentration tested (50 ml hl⁻¹), whereas reduced deposition at the higher concentration (100 ml per hl⁻¹) was attributed to excessive spray run-off. No significant improvement of spray deposition was observed for both concentrations tested with Villa 51 (50 and 100 ml hl⁻¹). Spray mixtures with adjuvants Agral 90 and Solitaire yielded similar deposition values at 500 l ha⁻¹ compared with the fenhexamid-only control at 720 l ha⁻¹, but reduced deposition at the higher spray volume, possibly due to spray run-off. This study clearly demonstrated the potential of adjuvants to improve deposition quantity and quality, but highlights the necessity to match adjuvant concentrations and application volumes on the spray target to achieve maximum spray deposition.     

3S技术在拉萨市森林植被调查中的应用

综合介绍了在西藏高寒生态条件下，利用3S（RS、GIS、GPS）技术对拉萨市森林资源进行调查的可行性、技术路线及成果精度，并指出了3S技术在西藏森林调查的运用前景。     

里下河小麦小区播种机功能创新研究

介绍了里下河小麦小区播种机的各部分功能以及实现方式,并与现有科研单位使用较为普遍的温特斯泰格、红兴隆小区播种机进行对比,为广大科研单位在小区播种机的选择上提供依据。     

Effectiveness of geotextiles in reducing runoff and soil loss: A synthesis

Despite geotextiles having potential for soil conservation, limited scientific data are available to assess the effects of geotextiles in reducing runoff and water erosion. Hence, the objective of this review is to analyse the effects of plot length (L) and other possible affecting factors [cover percentage (C, %), slope gradient (S), rainfall duration (D), rainfall intensity (I), sand, silt and clay contents, soil organic matter (SOM) content and geotextile type (natural or synthetic)] on the effectiveness of geotextiles in reducing soil and water loss, based on reported experimental data. From linear regressions, C (%) and soil sand, silt and clay contents are found to be the most important variables in reducing SLR (ratio of soil loss in bare plots to that in geotextile treated plots) for splash, C (%) for interrill and D (min) for rill and interrill erosion processes, respectively. Soil clay and silt contents and D are key variables in decreasing RR (ratio of runoff from bare plots to that from geotextile treated plots) for interrill, and clay content for rill and interrill erosion processes, respectively. The linear relationship between mean b-value (geotextile effectiveness factor in reducing soil loss) and L of all studies was not significant (P > 0.05). The same is true for the relationship between L and SLR, and L and RR. However, when L is added to an equation as an interaction term with C (%), geotextile cover is significantly (P < 0.05) more effective in reducing SLR on shorter plots than longer ones for both interrill and rill and interrill erosion processes. Buffer strip plots (area coverage ∼ 10%) with Borassus and Buriti mats have the highest b-values.     

小麦品种边行优势和内行表现对小区产量的影响

小区产量是小麦育种中重要的评价指标。边行优势和内行表现对小区产量影响很大,明确不同品种间边行优势和内行表现的差异,对科学评价品种产量水平有重要意义。选取黄淮冬麦区南片株高相近的半冬性半矮秆小麦品种周麦18、华育198、郑育8号和百农207进行小区试验,分别以边行、内行和小区为收获计产方式,研究不同品种的边行优势和内行表现对小区产量的影响。结果显示,4个品种的边行产量均高于内行产量;除周麦18外,其余3个品种边行与内行间的产量差异均达显著水平。边行产量和小区产量由高到低的品种排序皆为百农207、郑育8号、华育198和周麦18;内行产量由高到低的品种排序为华育198、百农207、郑育8号和周麦18。不同小麦品种在小区试验中边行优势和内行表现会对品种产量评价产生很大影响,在小麦品种选育及推广栽培过程中应予以充分考虑。     

早生优质抗寒茶树新品种"浙农117"选育研究

以福云自然杂交后代为育种材料,经系统选种、无性繁殖育早生优质抗寒茶树良种“浙农１１７”。品比试验与试种结果表明：该品种发芽期特早,适制扁形名茶和大宗红绿茶,品质超过福鼎大白茶;小区产量显著高于对照;茶多酚、咖啡碱、儿茶素平均含量比福鼎大白茶分别高３．３２、０．４５和５５．８９个百分点,氨基酸低０．３６个百分点;抗寒性强,尤其在倒春寒中表现甚佳,抗病虫能力也较强。     

毛泽东与20世纪60年代经济调整中的自留地问题简析

自留地在三年困难时期一度被称为救命地,20世纪60年代在经济调整前后,毛泽东对自留地问题给予了较多的关注,他比较早提出了要恢复农民的自留地;把自留地写入《农村六十条》,从制度上予以保护农民的自留地;在四清运动中,仍然坚持要保留农民的自留地。这一切,都使农民的自留地得以保存,这对农业生产恢复和发展是有利的,从而也为国民经济调整成功作出了贡献。