内陆干旱区不同灌溉制度对盐碱地滴灌土壤盐分离子分布的影响

通过田间试验研究覆膜滴灌条件下不同灌溉制度对土壤盐分分布的影响。试验通过控制滴头正下方20 cm处的土壤基质势下限进行灌溉,共设5个水平的土壤基质势处理:-5 kPa(S1)、-10 kPa(S2)、-15 kPa(S3)、-20 kPa(S4)和-25kPa(S5),每个处理重复3次,按随机区组布置。结果表明:不同土壤基质势控制对盐渍土中盐分分布有显著影响,不同土壤盐分离子的分布各不相同。其中Na+与Cl-容易被淋洗,两个生长季后,各处理土壤中Na+与Cl-含量有显著降低,并且土壤基质势控制越高淋洗效果越好。SO42-与HCO3-的淋洗效果主要受离子浓度影响,第一年淋洗效果较第二年明显。Mg2+与Ca2+不易随水移动,各处理无明显差异。经过两个生长季的灌溉淋洗,各处理土壤SAR值与全盐含量均有显著降低,根区内SAR值与全盐含量的降低幅度均在50%以上。研究结果对内陆干旱区盐碱地水盐调控和灌溉制度的制定具有理论意义和应用价值。     

离底拖网的游泳动物群落特征——以兄弟岛渔场为例

为探究离底拖网对游泳动物的群落结构以及捕捞量的影响,于2019年9月和2020年9月在福建海域兄弟岛渔场开展了36网次的底拖网专项试验,通过调整曳纲长度控制底拖网作业过程中的网位变动,分别保持底拖网作业在贴底或离底1 m的状态,以物种组成、渔获量对数均值、优势度、多度谱、多样性等参数,分析和比较了贴底拖和离底拖的游泳动物群落结构变化。结果显示:贴底拖和离底拖游泳动物的种类数分别为126种和79种,贴底拖游泳动物的总尾数和总体质量均为离底拖的3倍,贴底拖的渔获量对数均值比离底拖要高0.36,表明贴底拖网的渔获物以栖息于底层的游泳动物为主;贴底拖的游泳动物多样性、均匀度和丰富度分别为2.81、0.65和10.01,均高于离底拖(2.29、0.60和8.13),经济幼鱼的比例更高,说明贴底拖会对游泳动物的多样性以及幼鱼造成更大的损害;离底拖游泳动物的优势度指数为0.41,高于贴底拖的0.29,其多度谱曲线更陡,说明近底层游泳动物群落优势种分布更集中、数量分布不均匀。研究结果可以为底拖网渔业的科学管理提供依据。     

青海云杉容器育苗技术

介绍了青海云杉容器育苗从容器选择、基质配制、种子处理及播种苗抚育管理的技术要点,并与苗床育苗作了对比,表明容器育苗在提高苗木品质,缩短育苗周期方面表现良好。     

基于人工神经网络的CHRIS数据内陆水体叶绿素浓度反演研究

利用BP神经网络和CHRIS高光谱数据反演了富营养化非常严重的太湖梅梁湾地区叶绿素A浓度。首先计算了CHRIS模式2的18个波段与叶绿素A浓度的皮尔森相关系数,选择CHRIS的前5个波段和第13波段的反射率值作为神经网络的输入,以野外测量的叶绿素A浓度为神经网络的输出。实验表明,BP神经网络具有很好的非线性拟合能力,叶绿素A浓度的反演精度相对误差仅为22%,明显优于传统的多项式模型,显示BP神经网络与CHRIS高光谱数据结合的方法在内陆水体水质参数反演领域的应用具有相当的优势。     

南海不同海域鸢乌贼生长与死亡参数比较

根据2011-2015年南海海域灯光罩网渔船捕获的鸢乌贼样品,利用Fisat II软件对南海鸢乌贼群体的生长死亡系数进行估算。结果显示：南海没有大型群鸢乌贼个体,且雌性个体（12.05cm）比雄性个体（10.91cm）大;南海北部和南部的鸢乌贼均呈正异速生长,胴长和体质量关系b值分别为3.470~3.605和3.379~3.773;生长参数K反映了南海北部更适合于雄性鸢乌贼生长;南海南部海域鸢乌贼雌性（1.84）和雄性（1.76）总死亡系数相差不大,开发较为均衡;南海北部海域鸢乌贼雌性（0.60）总死亡系数远小于雄性（4.83）,显示该海域鸢乌贼未能充分开发。从渔业资源开发的角度,渔业政策偏向于开发南海南部鸢乌贼资源,使得北部鸢乌贼资源未能充分开发,不利于南海鸢乌贼资源的可持续利用。     

21世纪桃树次生木质部导管分子特征的观察

运用离析法和显微照相等技术,以晚熟桃21世纪桃为试材、典型的耐寒品种珲春桃为对照,研究比较了21世纪桃次生木质部导管分子的特征。结果表明,21世纪桃树干次生木质部导管分子中存在着许多不同的样式,迎风面导管分子的特征为多具尾性、长导管性、宽导管性、孔纹导管、单穿孔等,这些特征为21世纪桃在生长季节旺盛的水分需求提供了强有力的保证作用,同时,在风力强劲的冬季也可能使导管容易形成空穴和栓塞,水力结构破坏,致使输水系统受限,可能造成冬害。     

The legacy of past disturbance: Chronic angling impairs long-term recovery of marine epibenthic communities from acute date-mussel harvesting

Two major concerns affect the way we perceive impacts: first, no ecosystem can still be considered pristine and second, stressors may interact. Untangling the effects of broad-scale anthropogenic stressors is complicated as appropriate unimpacted areas at relevant scales are usually unavailable for contrast with impacted regions. Although the perfect study design in the traditions of small-scale manipulative experiments may not always be possible, many human impacts and the mechanisms associated with ecosystem responses have been highlighted in literature allowing contrasting predictions on expected patterns to be tested. We applied such an approach to the Marine Protected Area of Bergeggi (Ligurian Sea, NW Mediterranean). Our study aimed at assessing the effects of recreational angling (a presumed chronic stress) on the recovery of epibenthic communities following historical date-mussel harvesting (an extreme disturbance) by making and testing alternative predictions on the structure of epibenthic communities that should be apparent depending on the importance of specific mechanisms. Effects of date-mussel harvesting were still visible 20 years after its cessation, mostly because recovery is hampered by persistent sea-urchin grazing. We hypothesized that fish biomass removal by angling favours high sea urchin abundance. Based on these premises, we assembled information on angling pressure, sea urchin abundance and substratum cover by different trophic guilds to test our predictions. Our study indicates that the interaction between date-mussel harvesting and angling produced a shift, from autotrophic-dominated to consumer-dominated communities as a consequence of cascading trophic effects. Such an outcome implies that chronic recreation fishing pressure is blocking recovery in locations previously impacted by date-mussel harvesting. Testing predictions proved efficient in describing the interaction among stressors when system history is known and represents a valuable approach to provide scientifically sound insight for improved conservation management.     

木麻黄树干细胞组织结构与对星天牛抗虫性的关系

本文报道了４个品系木麻黄木材组织显微解剖结果，分析了木材导管、导管间区木化细胞和射线等物理特征，探讨了木麻黄抗虫机制。高抗品系Ｃ４４木材导管数量少，单位面积（１ｍｍ２）仅有２０．２５个导管，且占木材面积少，仅为９．７２％；导管间区木化细胞较明显，壁厚与腔径比值最大，为５６．５９；单位面积射线的束数、长度、宽度和射线面积／总面积等指标均为最低。说明该品系木麻黄木质部水分含量低、材质坚硬致密、木质部提供养分少，因而不利于星天牛幼虫的生存发育。     

Food-web traits of protected and exploited areas of the Adriatic Sea

This study presents a comparative analysis of protected and exploited Mediterranean Sea food webs using standardized ecological models of two ecosystems: the Central-North Adriatic Sea (highly exploited) and the Miramare Natural Marine Reserve (Northern Adriatic Sea, protected since 1986). Food webs are analysed in terms of structural and functional traits including trophic levels, transfer efficiency, trophic role of species and keystoneness, trophic spectra and other synthetic ecological indicators. Our results highlight similarities between food webs of the Adriatic Sea, differences that are likely due to the impact of fishing and differences that should be related to other factors. Analysis of biomass distribution along functional groups and of trophic spectra indicates that protected area presents higher mean trophic level of the community, higher biomasses, lower production and generally lower transfer efficiency than fished area. Our results indicate that measures of food web complexity (system omnivory index and ascendency), as well as pelagic/demersal and fish/invertebrates biomass ratios are higher in the protected area than in exploited ecosystem due to fishing-induced changes. Thus, this study highlights that marine protected areas can efficiently contribute to maintain structural and functional traits of marine ecosystems.