内蒙古草甸草原生物量碳分配格局

以中国北方草甸草原为研究对象,借助GIS等工具手段,在草地群落类型实测数据基础上,对内蒙古草甸草原的地上/地下生物量分配开展定量研究,主要结论如下:1)内蒙古草甸草原的生物量碳密度为660.43 g C/m²,其中地榆群落(460.63 g C/m²)具有最高的地上生物量碳密度,地榆群落(787.10 g C/m²)和五花草塘群落(776.22 g C/m²)具有最高的地下生物量碳密度,其他群落间则不存在显著性差异(P>0.05);2)温带草甸草原以16.60×10⁶ hm²的面积,贡献了111.20 Tg的生物量碳,其中地上生物量碳为27.57 Tg,地下生物量碳为83.63 Tg,根冠比(R∶S)为3.03;3)地下生物量沿土壤深度的分布可分为两种类型:线叶菊、芨芨草、野大麦、地榆、贝加尔针茅、苔草以及五花草塘群落属于“指数型”,其地下生物量主要分布在0~10 cm土壤层,且符合指数函数,该类型占据草原群落的主要部分;拂子茅、小叶锦鸡儿以及芦苇群落属于“抛物线”形,其地下生物量主要分布在0~10 cm和20~40 cm土壤层,该类别群落主要为灌木或半灌木,分布曲线不符合指数函数而符合二次函数。     

播种期和密度对冬小麦新冬29号产量形成的影响

为给在近年冬前积温增加的前提下冬小麦的种植选择适宜的播种期和密度组合,以新冬29号为材料,于2009-2010年在新疆伊宁市进行播种期和密度二因素试验,研究不同播种期和密度条件下小麦的产量及其构成状况。结果表明,播种期和密度对各生育时期总茎数的影响都显著。播种期对穗粒数、千粒质量的影响不显著,但对穗数和籽粒产量的影响显著。密度对3个产量构成因素的影响均达到显著水平,但对籽粒产量的影响不显著。播种期与密度对单位面积穗数、穗粒数和籽粒产量存在显著交互作用。根据各播种期与密度组合的产量分析,10月10日为最佳播种期,其适宜密度为基本苗480万/hm2;10月2日至10日为较适宜播种期,其适宜密度为基本苗(480~600)万/hm2。     

‘晋大麦（啤）2号’不同播期密度与产量关系的探讨

通过探讨‘晋大麦（啤）2 号’在当地生态环境下的最佳综合配套高产栽培技术,为推广种植本品种获得高产高效提供科学的理论依据。对该品种进行了不同播期、密度与产量关系的研究,以明确产量与播期、播量的关系。结果表明：播量从60.00~120.00 kg/hm2范围内,随播量增加产量随之提高,变幅在6186.98~6573.66 kg/hm2,反之,播量再高时,产量降低。播期以9 月30 日至10 月5 日产量较高,变幅为6600.33~6693.67 kg/hm2,随之播期推迟产量变低。选择适宜的播期和播量,对‘晋大麦（啤）2 号’品种获得高产至关重要。     

关于核密度具有间断点的Cauchy主值积分

讨论在实轴上核密度具有无穷个间断点的Ｃａｕｃｈｙ主值积分的性质，在一定条件下，得到了一些结果。     

轴向柱塞泵功率密度影响因素分析

为进一步提高轴向柱塞泵功率密度,首先结合前人工作针对功率密度给出量化计算公式,并对其中最重要的2个因素进行了研究。分析表明,影响因素1单位体积的每转排量主要由斜盘倾角与柱塞分布圆半径决定,并提出采用柱塞包覆滑靴形式提高该因素值,计算表明其柱塞泵功率密度可提高60%;影响因素2最高转速主要受自吸性能影响,且普通柱塞泵自吸性能受缸体腰型槽粘性阻力与强制漩涡阻力影响,并随着转速提高而下降,对此提出一种双向倾斜式腰型槽缸体,其仿真证明该结构具有离心甩油作用,其最高转速最高可提高45.4%。最后针对大排量双联泵功率密度下降问题提出了一种对称X型高功率密度轴向柱塞泵结构,其功率密度提高了43%。     

Effect of bulk density and soil water tension on denitrification in the rhizosphere of spring wheat (Triticum vulgare

Summary Pot experiments were carried out to study the influence of bulk density (D _b), soil water tension (pF) and presence of plants (spring wheat) on denitrification in a low-humus B_t-horizon of a udalf. Pots of only 5-cm depth were found to be most suitable for the experiments when using the acetylene inhibition method. Almost homogeneous soil compaction between 1.1 and 1.6g soil cm^–3 was achieved by a Proctor tamper. Water tensions were adjusted by means of ceramic plates on which negative pressure was applied. No denitrification was detected in unplanted pots. With planted pots and increasing bulk density denitrification increased more in pots with 14-day-old plants than in pots with 7-day-old plants. With 14-day-old plants N₂O emission pot^–1 increased steadily from 2 mol at D _b 1.1 to 8 mol at D _b 1.6, when soil moisture was adjusted to pF 1.5, although root growth was impaired by higher bulk density. From an experiment with different bulk densities and water tensions it could be deduced that the air-filled porosity ultimately determined the rate of denitrification. When low water tension was applied for a longer period, water tension had an overriding effect on total denitrification. Denitrification intensity, however, i.e. the amount of N₂O g^–1 root fresh weight, was highest when low water tension was accompanied by high bulk density. The results suggest that the increase in denitrification intensity at oxygen stress is partly due to higher root exudation.     

Impacts of increased fire frequency and aridity on eucalypt forest structure,biomass and composition in southwest Australia

Water stress and fire disturbance can directly impact stand structure, biomass and composition by causing mortality and influencing competitive interactions among trees. However, open eucalypt forests of southwest Australia are highly resilient to fire and drought and may respond differently to increased fire frequency and aridity than forests dominated by non-eucalypt species. We measured the variation in stem density, basal area, stand biomass, sapwood area, leaf area and litterfall across 16 mixed jarrah (Eucalyptus marginata) and marri (Corymbia calophylla) forest stands along an aridity gradient in southwest Australia that had variable fire histories. Fire frequency was defined as the total number of fires over a ∼30-year period and aridity as the ratio of potential evapotranspiration to annual precipitation. Total stand biomass and sapwood area were predicted from diameter at breast height of individual jarrah and marri trees using allometric equations. Leaf area was estimated using digital cover photography. More arid and frequently burnt stands had higher stem density, especially of smaller trees, which were mainly jarrah. Overall, both standing biomass and leaf area decreased at more arid sites, while sapwood area was largely unaffected by aridity, suggesting that these stands respond to increased water limitation by decreasing their leaf area relative to their sapwood area. Biomass of marri was reduced at more arid and, to a lesser extent, at more frequently burnt stands. However, total stand biomass (jarrah and marri) and leaf area index did not vary with fire frequency, suggesting that less marri biomass (due to slower growth rates, higher mortality or less recruitment) was compensated by an increase in the density of jarrah trees (regeneration). We conclude that increased fire and drought shift tree species composition towards more fire-resistant species and result in denser stands of smaller trees. In contrast, total stand biomass declines with increasing aridity, but has no association with fire frequency.     

亏缺灌溉对成龄库尔勒香梨产量与根系生长的影响

研究了亏缺灌溉对成龄库尔勒香梨树营养生长、果实生长与吸收根系分布的影响。香梨的生育中期,设计了4种土壤水分亏缺(灌前土壤水势下限):轻度胁迫(-100 kPa)、中度胁迫(-200 kPa)、重度胁迫(-300 kPa)和对照(-50 kPa)。灌溉系统为地表滴灌。试验结果表明,亏缺灌溉显著地减少了夏季剪枝量,提高了果实产量。充分灌溉条件下,香梨树根长密度从树行由内向外呈递减趋势,滴灌促进了湿润体内的吸收根系的发育;距树行0.5 m,根长密度随着深度的增加而减少;距树行1 m至1.5 m,根长密度随着深度的增加而增加;距树行2 m的非灌溉区,根长密度在垂直方向上变化不显著。为适应滴灌湿润体内水分胁迫,香梨树在湿润体内及非灌溉区的吸收根系的分布均发生了显著的调整。适度水分胁迫下的根长密度增加对香梨产量有促进作用。     

林带冬季相结构参数及透风系数的算法推导

从林带结构参数——疏透度β、立木表面积疏透度S’、立木体积疏透度V’、地上生物表面积密度C、地上生物体积密度W的定义和运算关系出发,推演出冬季相林带结构参数之间、以及它们与林带透风系数α、林带宽度D、枝条平均直径d的相互关系,其表达式为:W=V’/D=1/4dC=dS’/4D=-πdlnβ/4D=-0.1πdlnα/D该式是对几个主要结构参数之间具有同质性的证明,说明不同结构参数概念具有本质上的继承性和一致性,不存在严格意义上的排他性,在一定条件下是可以换算的,为林带防风效应评价运算提供了方便。导出一组适合我国北方干旱风沙区农田防护林带防风效应评价的运算公式。     

Effects of Clear‐Cutting Alder Coppice on Surface Soil Properties and Aboveground Herbaceous Plant Biomass

The purpose of this investigation was to evaluate the effects of clear‐cutting and skidding impacts on surface soils in an alder coppice and aboveground herbaceous biomass. For this purpose, experimental sites used in the study were a randomized complete block with four replications. Some soil properties were measured at 60 pits at 0 to 5 cm and 5 to 10 cm deep in control, normal harvest, and main skid trail sites. In the main skid trail site, as compared to the control and normal harvest site, the bulk density increased from 0.90 to 1.52g cm^?3, the soil organic‐matter content decreased from 4.77% to 1.65%, and saturated hydraulic conductivity decreased from 86.34 to 9.6 cm h^?1 at 0 to 5 cm deep. Optimization of harvesting time and rehabilitation of skid roads needed to be done to prevent and minimize negative impacts of the skid roads on soils.