Spatial and Temporal Variability in Dissolved Inorganic Nitrogen Fluxes at the Sediment–Water Interface in Lake Illawarra, Australia

In this study, benthic flux measurements of inorganic nitrogen (i.e., $ {\text{NH}}^{ + }_{4} $ , $ {\text{NO}}^{ - }_{2} $ ?+? $ {\text{NO}}^{ - }_{3} $ ) were made using a batch incubation system at different stations (i.e., shallow sandy macrophyte and unvegetated beds, and deep central mud) over four seasons in Lake Illawarra, NSW, Australia, to study the influence of different primary producers (i.e., seagrasses, microphytobenthos (MPB) and macroalgae) and/or different sediment types (i.e., sand or mud) on the benthic fluxes. In general, nutrient fluxes displayed typical diel variations, with lower flux out of sediments (release) or enhanced uptake by the sediment in the light, due to the photosynthetic activities of the plant-MPB-sediment community in Lake Illawarra during photosynthetic periods. A distinct seasonal pattern of inorganic-N fluxes was also observed (e.g., the marked difference between summers 2002 and 2003). This may be explained by the seasonal variations in the biomass and activity (growing or decay phases) of MPB, seagrass and macroalgae, which may influence their nutrient assimilation and alter the chemical conditions of surface sediments that influence the benthic geochemical processes and thus benthic nutrient fluxes. On an annual basis, unvegetated sediments displayed net DIN effluxes, while seagrass beds showed a net DIN uptake, and the highest DIN uptakes coincided with the largest standing crop of seagrass and/or macroalgae and the highest levels of benthic community production. This may be due to the enhanced denitrification and/or assimilation activity by rooted plants and macroalgae, and the effect is most efficient during periods of net growth (e.g., in Spring 2002).     

巴东皱皮木瓜发育及主要成分的变化分析

以湖北巴东产的皱皮木瓜为试验材料,分别在皱皮木瓜果实7个不同生长期采样,通过果实颜色、纵横径、鲜果质量等形态特征的测定,并采用HPLC法对不同生长期内的有效成分(齐墩果酸、熊果酸、原儿茶酸、绿原酸)进行检测,综合评价皱皮木瓜最佳的采收季节和质量指标。结果表明:(1)皱皮木瓜的纵径、横径、鲜果质量增长随生长阶段呈逐渐递增趋势;(2)在不同生长期有效成分含量呈上升或者下降的趋势。其中,齐墩果酸和熊果酸含量在整个发育过程中逐渐增加,7月10日—20日增加较为明显,两者在成熟期达到最大值,原儿茶酸和绿原酸在幼果期时保持较高的含量,两者变化趋势为降—升—降。     

抚育间伐对小兴安岭天然针阔混交林碳储量的影响

在小兴安岭地区带岭林业实验局东方红林场天然林试验区,设置6块样地,对天然针阔混交次生林进行不同强度(10%、15%、20%、25%、30%、35%)的抚育间伐;采用平均标准木法取样、实验室重铬酸钾法测定林木碳质量分数,分析不同间伐强度对乔木层地上部分生物量及碳储量的影响。结果表明:随着间伐强度的增加,乔木层地上部分生物量、碳储量整体呈先增加再减小趋势,但间伐8 a内各间伐生物量、碳储量均显著少于对照。伐后1~4 a,间伐强度20%,乔木层碳储量增长率、增长量均高于对照;间伐后1~4 a内,间伐强度20%,乔木层碳储量的恢复能力最强。间伐后5~8 a,高度间伐(间伐强度30%、35%)碳储量恢复能力最弱;间伐8 a后,各间伐强度(10%、15%、20%、25%、30%、35%)的碳储量,分别为74.93±3.42、86.96±7.31、99.24±2.43、93.64±6.68、85.23±2.11、79.54±3.38 t/hm2,林木各器官碳储量差异显著,从大到小依次为树干、树枝、树叶;间伐8 a后,各间伐树干碳储量所占比例比对照所占比例增加-0.04%~12.27%,在间伐强度为20%时树干碳储量比例最高,说明间伐强度20%有利于小兴安岭天然针阔混交林树干碳储量的累积及单株林木质量的提高。总体看,短期间伐(4 a内)利于20%间伐乔木层碳储量的迅速积累,8 a内各间伐仍处于乔木层地上部分碳储量低于对照的恢复期。     

丘陵山地姿态调整轮式拖拉机的设计与仿真

针对丘陵山地拖拉机作业环境复杂,对拖拉机的稳定性、通过性和地形适应性要求高的突出问题,设计了一种可进行姿态调平的丘陵山地拖拉机,主要由姿态调整后驱动桥、姿态调整前驱动桥、发动机及电液控制系统组成。姿态调整后,驱动桥设置有可独立回转摆动的轮边减速机构,实现了驱动桥刚性结构柔性调节。姿态调整前驱动桥可围绕拖拉机摇摆轴进行姿态调节。电液控制系统实时监测前、后驱动桥与地面间的坡度夹角变化,自动调节驱动桥的摆动姿态,始终使机身处于水平姿态,提高整机作业稳定性。     

氮磷钾配施对青麻叶产量及肥料利用率的影响

采取田间小区试验,研究氮磷钾配施对青麻叶肥料利用率及产量的影响,探索NPK肥料在青麻叶上的利用效率,以期为青麻叶科学施肥提供科技支撑.结果表明:N肥对青麻叶生物产量、经济产量影响最大,P肥、K肥次之,N、P、K肥料配合施用是提高青麻叶产量的关键措施;N、P、K肥料配合施用能显著提高肥料利用率,在试验条件下,N、P、K肥料配合施用青麻叶的N、P、K肥利用率分别为49.5％、27.4％、58.1％.     

黑龙江省湖泊水域成熟白鲢卵巢周期变化的研究

本文对黑龙江省湖泊、水库等水域成熟白鲢卵巢进行了解剖学、组织学观察。对卵巢的色泽和不同时相卵细胞的组织演变和数量的关系作了叙述。着重讨论了在高寒地区白鲢卵巢发育的特点：即第4时相退化卵的滤泡细胞膜不论在秋、冬两季或在春季均呈扁平，没有吞噬卵黄的现象。退化卵一直延迟到翌年5月中旬才开始吸收，于此同时，正是第3时相卵细胞迅速发育阶段，退化卵的吸收和新一代卵细胞的成长两者几乎是在同一时间进行的。所以卵巢成熟系数在周期变化中，它的波动幅度不大。     

使樱花赏花期延长的日本引种品种的选育搭配研究

对武汉法雅园林集团有限公司从日本引进的39个樱花品种的成活率和花期进行了观测研究,筛选出了23个成活率在80%以上的花期不同的品种,为园林绿化工程中延长樱花赏花期的品种搭配设计提供参考依据。     

魁蚶亲贝控温促熟试验

首次研究了魁蚶亲贝性腺室内控温促熟技术，３月中旬亲入池，人工控温，强化饲育２５－２８天，４月中下旬性腺成熟，排放精卵，比自然界提前３个月左右，水温１６℃以上是魁蚶亲贝性腺成熟的迅速期。１９９１年１１月专家鉴定认为，本研究属国内首次，居国内先进水平。     

池塘投饵机控制系统

根据北方池塘投铒的实际要求，结合电路控制的各项性能，研制开发了一种新型的投铒机控制系统。应用逻辑电路和定时器电路进行控制，使用拨码开关技术设置定时时间、自动重复启动的间隔时间和投铒的各项参数，并具有延时投铒功能。操作简单直观、定时准确、抗干扰能力强，解决了定时定量、准确投喂的问题，避免了铒料投喂的浪费。     

Two Cycles of Recurrent Maternal Half-Sib Selection Reduce Foliar Late Blight in a Diploid Hybrid Solanum phureja-S. stenotomum Population by Two-thirds

Foliar late blight, caused by Phytophthora infestans, is an important disease problem worldwide. Foliar resistance to late blight was found in a hybrid population of the cultivated diploid species Solanum phureja-S. stenotomum (phu-stn). The objective of this study was to determine if resistance to late blight could be improved by recurrent maternal half-sib selection in the phu-stn population. Four clones from each of 72 maternal half-sib families plus the check cultivar ‘Atlantic’ were evaluated for late blight resistance in replicated field trials in Pennsylvania. The most late blight resistant clone from each of the 72 families was randomly intermated to advance the population. The cycle 1, 2, and 3 populations were evaluated in 1996–1997, 2003–2004, and 2009–2010, respectively. Percent infected foliage was recorded several times towards the end of the growing season and used to compute area under the disease progress curve (AUDPC). Mean AUDPC was 652 (cycle 1), 556 (cycle 2), and 276 (cycle 3), whereas the mean AUDPC of ‘Atlantic’ ranged from 775 to 863 each cycle. Narrow-sense heritability for resistance was estimated as 0.78, 0.77, and 0.80 in cycles 1, 2, and 3, respectively. Recurrent maternal half-sib selection continues to improve the levels of resistance to late blight in this diploid population with no adverse effect on the amount of additive genetic variance. Additional improvements for late blight resistance are likely to occur if this approach is continued.