地膜覆盖旱直播栽培对水稻产量及群体冠层特性的影响

通过田间试验,研究了地膜覆盖旱直播栽培水稻群体冠层的结构特性、生态特性以及产量和产量构成。结果表明：地膜覆盖旱直播栽培水稻产量高于常规水育秧栽培（CK）,有效穗数和成穗率增加。地膜覆盖旱直播栽培冠层各个层次的覆盖指数都显著低于常规水育秧栽培,冠层中、下层平均叶倾角大于常规水育秧栽培,叶片直立,增加了光的通透性。地膜覆盖旱直播栽培水稻冠层空气最高温度延迟2 h达到,且小于对照;冠层空气CO2浓度则较对照延迟2 h达到最低点,且12：00之前高于对照,14：00之后则低于对照;冠层空气水分含量12：00之前小于对照,14：00之后则略大于对照。说明地膜覆盖旱直播栽培改善了群体结构和生态特性,为水稻高产提供了较好的生态基础。     

影响杂交水稻纹枯病发生的若干植株群体指标

 2004-2005年早季和晚季，以两系法杂交稻粤杂122为材料，设置8个氮肥处理，在广州进行连续4季田间试验，研究了纹枯病病情指数与穗分化始期茎蘖数(TILPI)、叶绿素含量(SPADPI)、抽穗期茎蘖数(TILHD)、叶面积指数(LAIHD)、叶绿素含量(SPADHD)等5项水稻群体指标的关系。结果表明，影响纹枯病病情指数的因素包括气象条件和群体条件两大类。TILPI、SPADPI、TILHD、LAIHD和SPADHD是影响纹枯病病情指数的主要群体指标，它们可以解释不同年份、不同季节、不同施氮处理纹枯病病情指数变异的44.8%。日平均温度和相对湿度是影响纹枯病病情指数的主要气象因素，它们与TILPI、SPADPI、LAIHD、SPADHD一起，可以解释不同年份、不同季节、不同施氮处理纹枯病病情指数变异的82.7%。纹枯病病情指数随着抽穗期群体透光率的提高而下降，由日平均温度、相对湿度和抽穗期群体透光率可以解释纹枯病病情指数变异的80.2%。在保证穗数的前提下尽量降低苗峰，提高成穗率，在保证光合生产能力的前提下，适当降低叶片叶绿素含量和抽穗期叶面积指数，提高群体通透性，是协调高产与防病矛盾、培育健康群体的方向。     

地表臭氧浓度升高对麦田水热通量的影响

臭氧(O₃)浓度升高危害小麦生长,现有研究尚不清楚推广新的小麦品种能否减缓O₃对籽粒产量、农田蒸散和水分利用效率的负面效应,且研究O₃浓度升高对麦田水分利用效率的影响对农业用水管理具有重要意义。本研究利用完全开放式O₃浓度升高平台（O₃-FACE）,通过连续观测农田小气候特征,结合能量平衡法分析O₃浓度升高对麦田水热通量、小麦籽粒产量和田间水分利用效率的影响。结果表明：O₃浓度升高显著降低了开花后第32天小麦旗叶的叶绿素含量,降低了乳熟–成熟期的麦田潜热通量平均值和正午峰值,但影响幅度较小。O₃浓度升高对麦田平均水热通量及其分配无显著影响,也未影响籽粒产量、产量组成和田间水分利用效率。不同于10年前江淮地区主推的扬辐麦2号、烟农19和嘉兴002等品种,当前推广的农麦88表现出极强的O₃抗性。在O₃浓度不断升高背景下,种植农麦88有助于减缓O₃浓度升高对田间蒸散和水分利用效率的影响。     

基于变量灌溉动态分区管理的冬小麦产量与节水效果

喷灌机机载式红外温度传感器系统是动态监测农田作物水分亏缺状况、构建变量灌溉(variable rate irrigation,VRI)决策支持系统的重要工具。为了评估圆形喷灌机机载式红外温度传感器系统在变量灌溉动态分区管理中的应用效果,该研究以气象参数和土壤水分传感器网络构建的均一灌溉(uniform rate irrigation, URI)决策方法为对照,评估了基于气象参数、土壤水分传感器网络和作物冠层温度的变量灌溉决策方法对华北平原冬小麦灌溉制度、土壤含水率空间分布均匀性和节水增产效果的影响。在河北省邢台市大曹庄中国水利水电科学研究院智慧灌溉技术与装备创新示范推广基地开展试验,试验区为三跨加悬臂圆形喷灌机控制灌溉面积7.07 hm²,2021年试验区等分为2个子区,布置URI和VRI处理,2022年试验区等分为4个子区,布置URI处理、基于等间隔法进行管理区聚类划分的VRI(T1)处理、基于“Jenks”自然断点法进行管理区聚类划分的VRI(T2)处理和基于几何间隔断点法进行管理区聚类划分的VRI(T3)处理。结果表明,在冬小麦生育期内,URI和VRI处理灌...     

Rainfall redistribution of a virgin Pinus koraiensis forest and secondary Betula platyphylla forest in Northeast China

A virgin Pinus koraiensis forest in the Xiaoxing’an Mountains was selected to study its rainfall redistribution effect via 97 rainfall occurrences during a growing season. The following results were obtained: 1) The canopy interception of the P. koraiensis virgin forest amounted to 98168 mm during a growing season (May to September), which was 19.6 per cent of the total rainfall and 1.3 times that of a secondary Betula platyphylla forest. Compared with other forest types in China (11.4%–36.5%), the ratio of the canopy interception in the virgin pine forest was at a medium level. 2) The throughfall of the virgin pine forest was 395.77 mm, which accounted for 78.7% of total precipitation, and the stem-flow was 8.78 mm, accounting for 1.74% of total precipitation. Compared with the secondary birch forest, the virgin pine forest had lower throughfall but higher stem-flow. 3) Cubic regression equations (p < 0.01) which describe the relation between throughfall, stem-flow and canopy interception in the virgin pine forest and rainfall in an open field were fitted. A linear regression equation (p < 0.01) was found to be a better fit for the relationship between throughfall of the secondary birch forest and rainfall outside the forest. Factors affecting throughfall and stem-flow were analyzed, with results providing a good reference to the study of rainfall redistribution in coniferous and broadleaved mixed forests. __________ Translated from Science of Soil and Water Conservation, 2006, 4(6): 61–65 [译自: 中国水土保持科学]     

西江中下游生态公益林对降水截留分配效应研究

为了评估生态公益林涵养水源服务功能,选择德庆县三叉顶自然保护区生态公益林,定位观测2006年6月～2007年6月100次大气降水事件的截留分配效应。结果表明,观测期内降水总量为1 317.60mm,林冠截留量、树干茎流量和穿透水量分别是318.37,87.85和911.38 mm,林冠截留率、茎流率和穿透率分别为24.16%,6.67%和69.17%。林外降水量大于1.3 mm时才能观测到穿透雨,林外降水量达到3.0mm时才开始有树干茎流出现。林冠截留量、树干茎流量和穿透量与降水量均呈正相关,相关系数R2分别为0.788 8,0.957 7和0.965 9;林冠截留率与林外降水量呈负相关,而树干茎流率和穿透率呈正相关,相关系数R2分别为0.835 6,0.803 4和0.874 2。     

Competition between maize and Datura stramonium in an irrigated field under semi-arid conditions

Crop growth of maize ( Zea mays L.) and Datura stramonium L. in monoculture and competition was studied over 4 years in a flood irrigated field in Zaragoza (Spain). Plant density was 8.33 m^–2 for maize and 16.66 m^–2 (1994 and 1995) and 8.33 m^–2 (1996 and 1997) for D. stramonium . Maize yield was decreased by 14–63% when competing with the weed. Yield reduction increased as the time between crop and weed emergence decreased. The development of leaf area per plant during the exponential growth phase was faster in maize primarily because the leaf area of maize seedlings at emergence time was greater than that of the weed. The faster growth of maize in leaf area and height reduced the photosynthetically active radiation received by the weed. Datura stramonium had a lower radiation use efficiency (RUE) than maize. Competition from the weed slightly decreased the maximum leaf area index (LAI) of the crop, and leaf senescence of maize was accelerated. The weed competed with the crop late in the season reducing crop growth rate, grain number per ear and grain weight. Competitive ability of D. stramonium for light was mainly due to its growth habit, with the leaves concentrated in the upper part of the canopy (more than 75% of LAI in the upper 25% of its height), its higher light extinction coefficient (0.89) and its indeterminate growth habit. The N plant content of maize was not influenced by the presence of the weed. The weed had a higher N plant content than the crop throughout the season and took up more N in monoculture.     

Can the ecosystem mimic hypotheses be applied to farms in African savannahs?

The first ecosystem mimic hypothesis suggests clear advantages if man-made land use systems do not deviate greatly in their resource use patterns from natural ecosystems typical of a given climatic zone. The second hypothesis claims that additional advantages will accrue if agroecosystems also maintain a substantial part of the diversity of natural systems. We test these hypotheses for the savannah zone of sub-Saharan Africa, with its low soil fertility and variable rainfall. Where annual food crops replace the natural grass understorey of savannah systems, water use will decrease and stream and groundwater flow change, unless tree density increases relative to the natural situation. Increasing tree density, however, will decrease crop yields, unless the trees meet specific criteria. Food crop production in the parkland systems may benefit from lower temperatures under tree canopies, but water use by trees providing this shade will prevent crops from benefiting. In old parkland trees that farmers have traditionally retained when opening fields for crops, water use per unit shade is less than in most fast growing trees introduced for agroforestry trials. Strong competition between plants adapted to years with different rainfall patterns may stabilise total system productivity -- but this will be appreciated by a farmer only if the components are of comparable value. The best precondition for farmers to maintain diversity in their agroecosystem hinges on the availability of a broad basket of choices, without clear winners or 'best bets'. This revised version was published online in June 2006 with corrections to the Cover Date.     

不同农林复合系统小气候日变化特征研究

通过对江淮丘陵山区不同农林复合模式小气候观测,结果表明：不同模式的小气候因子的日变化有一定的差异,并具有相似的变化规律,初步认为,一年生五角枫（Acer mono Maxim）和马褂木（Liriodendron Chinese）与花生复合模式具有相对良好稳定的水、光、气、热生态小环境。