扰种齿辅助气吸式大蒜排种器设计与试验

为解决杂交蒜尺寸差异大而导致排种过程中单粒合格指数低及漏播指数高的问题,设计了一种扰种齿辅助气吸式大蒜排种器.以杂交蒜为研究对象,阐述了扰种齿辅助气吸式大蒜排种器的工作原理,基于杂交蒜自身的物理特性和农艺种植要求,构建了扰种齿曲面方程,确定排种器的关键结构参数;在此基础上以取种合格指数为试验指标,基于EDEM软件对排种...     

人工林邻体干扰模型的探讨及与林木生长的关系

本文提出邻体干扰的改进模型：并提出基株与邻体的确定原则和计测方法。以不同密度的华北落叶松人工林为测试对象，分析干扰指数与基株胸径、材积连年生长量、树冠发育、主干高径比等几个主要生长和形质指标的关系，探讨干扰指数与基株对生境资源利用效率的相关变化规律。结果表明，该指数是计测林木生长状况及在林分中所处地位的数量指标。     

变频器谐波的产生、危害及抑制

变频器的工作原理决定了它会产生高次谐波,这样会对设备及附近的仪器仪表产生影响。本文简单介绍了高次谐波产生的机理、危害及有效抑制干扰的方法。     

室性早搏的中医辨证论治分析

近年来,应用中医药防治室性早搏得到越来越多的重视。本文通过研究室性早搏在性别中的中医证型分布,不同合并症中的中医证型分布,以及初步总结谢海波副教授临床应用中医药治疗室性早搏的经验,为以后研究中医药如何更有效地治疗室性早搏提供参考。     

外源性C、N干扰对森林土壤酶活性的影响

通过对岷江上游连香树、云南松和糙皮桦3种典型林地外源性C、N干扰试验研究表明,施N和施C干扰使云南松林地土壤脲酶、过氧化氢酶和蔗糖酶活性有不同程度的提高,且在适度范围内,随干扰强度的增大效果明显增加。施N干扰可使糙皮桦林地土壤脲酶、过氧化氢酶和蔗糖酶活性较对照有不同程度的提高,而施C对土壤过氧化氢酶活性影响不明显;施N干扰使连香树林地土壤脲酶和过氧化氢酶活性降低,且有随施用量增加而减小的趋势,但使蔗糖酶活性增加,施C干扰使脲酶、过氧化氢酶和蔗糖酶活性较对照有不同程度的提高,且以弱度干扰效果较好。     

干扰对东祁连山高寒杜鹃灌丛土壤水热性能的影响

东祁连山高山地带的杜鹃灌丛受到放牧、砍伐和滑坡３种干扰后,第一年４～１０月,０～１０Ｃｍ土层的平均温度和含水量测定结果表明,与对照相比,长期重牧、砍伐和滑坡后土壤温度分别上升１.４℃、２．８℃和３．１℃;含水量则分别下降４４．２％、０．１１％和５０．６％,均有极显著差异。说明植被对土壤的水分涵养能力具有十分重要的作用,在保护和利用该类型及相邻草地资源时应予以高度重视     

Optimizing a Diode Array VIS/NIR Spectrometer System to Detect Plant Stress in the Field

Several spectrometer types for the detection of plant stress symptoms by measuring reflectance of crop canopies have been described in the literature. Only a few of them were field‐portable and combine both the visual (VIS) and near‐infrared (NIR) spectral ranges. In particular, NIR spectra enable considerable improvements in assessing crop properties. In the current study, a diode array two‐channel VIS/NIR spectrometer combination was adapted from laboratory to field application and optimized with regard to measuring configuration and procedure. Two plant canopies representing two extremes of morphological differentiation were studied. They consisted of a winter oilseed rape and a grass turf canopy of high vs. low morphological complexity. Derived from grass turf and winter oilseed rape canopy reflectance in the VIS and NIR spectral range vegetation indices (REIP, R₈₅₀ and SRWI) were calculated. It was shown that the choice of sensor head configuration mainly affected sensitivity and accuracy of measurements, whereas the vegetation indices were mainly influenced by sensor‐target angle, sensor‐target distance, daytime of measurement and cloud coverage. However, most impairments were substantially reduced by using a continuous referencation. Best results were obtained using an open fibre optic cable, sensor‐target distance of 1 m in nadir direction and a measurement interval between 12.00 and 16.00 h at clear sky conditions. To show the applicability of the proposed configuration and measurement protocol, growth traits of a winter oilseed rape canopy were investigated at an early stage of development. Based upon vegetation indices, reductions in shoot dry matter, shoot‐N concentration and shoot water concentration were reliably detected. Conclusively, this paper studies the effect of sensor head configuration, sensor‐target angle, sensor‐target distance and daytime of measurement on observed canopy reflectance in the VIS and NIR spectral range. Additionally, it presents, for the first time, a comprehensive and integrated analysis of the way in which these factors affect vegetation indices (REIP, R₈₅₀ and SRWI) derived from VIS and NIR spectra. The optimized procedure reduced interferences, expanded operation time and enabled high‐resolution reflectance measurements in the field.     

东祁连山杜鹃灌丛生态系统特征及干扰的影响

分布于东祁连山高山带的杜鹃灌丛优势种为头花杜鹃和百里香杜鹃,分盖度２０％～４０％。群落中绝大多数植物为地面芽（３３.３％）、矮高位芽（３０.１％）和地下芽（２６．１％）,一年生植物和地上芽植物仅占少数（１０.５％）。常绿植物杜鹃的物候期早于其它植物,其中以青海杜鹃（Ｒ. Ｐｒｅｚｗａｌｓｋｉｉ）最早。地上植物量呈单峰变化趋势, ８月干物质量达最高值 ９５０．２ ｇ／ｍ２。灌木地上地下植物量的主体以杜鹃为主,分别占 ７２．５％和 ６２．６％,且地上植物量大于地下。全群落地下植物量以草本为主。百里香杜鹃和头花杜鹃的热值含量分别为 ２１．９４ ｋＪ／ｇ和 ２１．６８ ｋＪ／ｇ,高于其它灌木,也明显高于世界陆生植被的平均热值。两种杜鹃不同部位热值含量的顺序为叶＞茎＞根。群落地上净第一性生产力为３０１.７ｇ／ｍ２干物质,光能转化率为０.１０２１％。群落在生长季保持低增长状态,具有顶级群落的特征。砍伐后第１年内群落的植被成分无明显变化,但自然滑坡地段的植被成分变化明显,植物种类由１８种变为１０种,优势种变为鬼箭锦鸡儿,对杜鹃和苔藓影响较大。     

Environmental disturbance and chironomid palaeodiversity: 15 kyr BP of history at Lake Mascardi,Patagonia, Argentina

1. Palaeoecological records may be useful in predicting the ecological outcomes for certain communities exposed to natural and human disturbance. In turn, theoretical work has emphasized the importance of baseline information on diversity to establish precise conservation and restoration policies. 2. Lake sediments provide good evidence of long-term changes in community composition, especially of insects from the family Chironomidae. Midge fauna is highly diverse and their remains are well preserved in sequential order allowing the construction of past assemblages. 3. To assess long-term community trends and stability in an environment virtually free from human impact, fossil midge assemblages were collected from a sediment core at Lake Mascardi (Río Negro, Argentina). Shannon's diversity index as well as rank-abundance relationships were estimated for core subsamples (10 cm slices), using a ‘taxonomic minimalist’ approach. 4. Diversity levels are relatively constant along the core. However, sharp reductions in diversity and equitability in midge assemblages are recorded. These reductions appear to be related to natural variability—mainly ash falls (pulse) and climatic (press) disturbing events. During pulse disturbances, both diversity and equitability fall, recovering rapidly after pressure is released. During press events (long-term disturbances) equitability falls whereas diversity remains fairly constant. Subfamily succession between pulse disturbances, follows proposed ecological species rank-abundance models. 5. These findings suggest that at long time-scales, a low level of taxonomic detail may be adequate for the analysis of community responses to environmental change. © 1998 John Wiley & Sons, Ltd.     

Impact of the invasion of pinewood nematode and the following different removal disturbance intensities on the plant diversity of Masson pine community

Reported in this paper are our findings of the study on changes in species diversity of different Masson pine communities after the invasion of Bursaphelenchus xylophilus (Steiner and Buhren) Nickle and subsequent and different removal disturbance management approaches. Based on the results, the species diversity indices for the arbor layers of the different communities can be arranged in the following order (from high to low): 1) broad-leaved stand after the removal of all infected pine trees in the pure pine stand in Fuyang; 2) lightly infected Masson pine and Schima superba mixed stand in Fuyang; 3) uninfected stand mixture of Masson pine and Castanopsis fargesii as a control; 4) lightly infested pure Masson pine stand in Fuyang; 5) Quercus variables stand formed following the selective removal of infected pine trees from a mixed Masson pine and Q. variables stand in Zhoushan Islands; 6) pure young Masson pine stand formed following the removal of all infected pine trees from a pure Masson pine stand; 7) pure Liquidambar formosana stand after the removal of infected pine trees from a pure pine stand in Zhoushan Islands; 8) a mixed stand consisting of Pinus thunbergii and the Masson pine in Zhoushan Island; and 9) moderately infected Masson pine stand in Zhoushan Islands. All the three diversity indices (R ₀ = richness, H′ = Shannon-Wiener index, and E = evenness) for the shrub layer did not show any significant differences among the various communities except for the pure pine stand in Zhoushan Island, which had the lowest diversity. The three indices for the herb layer of the pure young Masson pine, Q. variables stand, and L. formosana stand were higher than that of other stands. The integrated analysis showed that the Masson pine forest in different geographical situations and extent of damage had distinct disparity, just as in different disturbance degrees and restoring manners. We created the “index of disturbing intensity of stump and fallen woods” (IDISFW) to represent the degree of disturbance of tree removal to plant diversity. We found that the relationship between the species diversity index and the IDISFW shows both a lower and higher degree of removal disturbance that follows the “mid-altitude bulge” theory. Specifically, both excessive and insufficient removal of infected trees will cause a decline of plant species diversity to a certain degree. Covariance analysis indicated that different IDISFW had no significant effects on the species diversity of the arbor layer, but had different impacts on that of the shrub and herb layers, and therefore can be used to assess changes in species diversity of different Masson pine communities after the invasion of pine wood nematode. __________ Translated from Chinese Journal of Applied Ecology, 2006, 17(7): 1,157–1,163 [译自: 应用生态学报]