Occurrence of an exceptional catch of pelagic juvenile lingcod (Ophiodon elongatus) off Point Reyes, California

An exceptionally large catch of pelagic juvenile lingcod (Ophiodon elongatus) was made just offshore of Point Reyes, California in 1990. Results of 678 midwater trawls from annual surveys from 1983 to 1990 show that pelagic juvenile lingcod have a strong nearshore distribution and were most abundant in the Gulf of the Farallones, with a mean abundance of 5.0 per trawl. Otoliths from fish taken in the large catch were used to estimate parameters of a log-transformed Gompertz growth model, which was then used to calculate hatch dates. Hatching peaked around 24 March and ranged from 10 March to 19 April, implying a January-February spawning season for lingcod off central California. The large catch was associated with an anticyc-lonic eddy which would lead to water being trapped near the coast; convergence of fish associated with the eddy may have been due to either physical or biological effects.     

白浆土的农化性状

对白浆土有机质与全量和速效ＮＰＫ及微量元素Ｂ、Ｍｎ、Ｚｎ、Ｃｕ、Ｍｏ、Ｆｅ的分析认为白浆土中有机质与ＮＰＫ养分在表层均较丰富，向下层急剧减少，各地区及不同亚类之间有差异。有效Ｃｕ、Ｚｎ、Ｍｎ、Ｆｅ只有少部分白浆土缺，在剖面上分异大，随着生产的发展，应在测土的前提下进行补充；Ｂ和Ｍｏ在白浆土上缺的范围大，是当前生产上值得注意的问题。     

Analysis of environment-recruitment associations for a coastal red drum population reveals consistent link between year class strength and early shifts in nearshore winds

The identification of factors contributing to strong year classes of marine fishes has been a constant goal toward a mechanistic understanding of recruitment variability. Here, we explored a 26-year time series of the abundance of early juvenile red drum along the North Carolina coast to identify environmental features associated with variable recruitment success. The study location was near the northern edge of the species latitudinal range, and we hypothesized that consistent environmental forcing would be linked to the formation of strong red drum year classes. Patterns of variability in seasonal environmental features were disaggregated into multiple forms of temporal periodicity and analyzed using generalized additive models. We also contrasted patterns of environmental variation that occurred during the strongest recruitment events with those coinciding with the weakest red drum year classes. The early shift, during August, to favorable wind conditions was the most consistent environmental feature associated with red drum recruitment success. The combined duration and magnitude of N and NE winds during August of strong recruitment years was nearly double the level observed during weak recruitment years. Elevated nearshore sea surface temperatures early in the spawning season were also found to occur during years that produced strong year classes. Coastal productivity, indexed using chlorophyll a concentration, was positively associated with red drum recruitment, but also highlighted the need for more spatially resolved productivity data. Our findings highlight the importance of environment-recruitment linkages for marine fishes, especially near distributional boundaries where conditions to promote year class success can be brief.     

Temporal changes in European eel, Anguilla anguilla, stocks in a small catchment after installation of fish passes

Abstract  Changes in the abundance of European eel, Anguilla anguilla L., in the River Frémur, France, were examined over an 8-year period. Natural connectivity of the river was disturbed by three high dams that inhibited eel upstream migration and reduced recruitment by elvers and yellow eels. After eel passes were installed, fish became more abundant upstream (mean density 0.5 eel m⁻²). Moreover, except in the more upstream areas, no decline in eel numbers and biomass was found, in contrast to the general decline of eel throughout its distribution range. It was concluded that eel passes are important to conserve and/or to recover eel stocks.     

Decadal change in abundance of surface migratory myctophid fishes in the Kuroshio region from 1957 to 1994

Decadal change in abundance of surface migratory myctophid fishes was examined in the Kuroshio region of the western North Pacific for the 35 yr from 1957 to 1994 in relation to the Kuroshio regime shift, indicated by changes in its transport volume and sea surface temperature in the early 1970s. Each year, samples were collected from the 0‐ to 1‐m depth layer at night, from January to March, at 83 stations on average. Ten species belonging to five genera occurred. Juveniles [standard length (SL) ≤ 40 mm] and adults (SL > 40 mm) of each species were analysed. In juveniles, Myctophum asperum, M. nitidulum, Symbolophorus evermanni and Centrobranchus brevirostris accounted for 91.1% of the total catch (7419 individuals), while M. nitidulum contributed 82.4% of the total adult catch (494 individuals). The abundance of juvenile S. evermanni, C. brevirostris and M. nitidulum showed prominent peaks in 1971, together with adult M. nitidulum. These peaks corresponded to extraordinarily high zooplankton abundance in the Kuroshio region in 1971, suggesting high recruitment success and low adult mortality in surface migratory myctophids. Smaller changes in abundance in other years were species‐specific, and the fluctuation patterns were mainly explained by year‐to‐year fluctuations in the strength of the Kuroshio and the geographical distribution of each species, i.e. an increased Kuroshio flow volume resulted in an increase in tropical species and a decrease in temperate species, but no change in the pan‐Kuroshio species.     

桉树人工幼龄林根区和非根区土壤属性特征分析

深刻认识桉树人工幼龄林根区和非根区土壤属性特征对优化桉树营林措施具有重要意义。本研究以桉树人工幼龄林为研究对象,分析冬季和夏季桉树人工幼龄林根区和非根区0～20 cm和20～40 cm深度土壤理化性质、C∶N∶P化学计量比和细菌数量,探讨桉树人工幼龄林根区和非根区土壤理化属性和细菌丰度特征。结果表明,非根区土壤可溶性有机碳(DOC)、有机碳(SOC)、全氮(TN)含量显著大于根区土壤,非根区0～20 cm土壤可溶性有机氮(DON)和全磷(TP)含量显著大于根区土壤。夏季根区、非根区土壤含水量、DON、SOC和非根区DOC含量显著大于冬季;夏季桉树根区和非根区0～20 cm土壤TN、TP、土壤全钾含量显著低于冬季。参照全国土壤分级标准,冬季根区土壤SOC和夏季根区土壤TN含量为四级较缺乏水平。与全球森林土壤C∶N∶P平均值相比,桉树幼龄林根区土壤C∶N夏季高、冬季低,且根区土壤N∶P和C∶P均低于平均水平,推断桉树人工幼龄林冬季根区土壤存在C限制,夏季根区土壤存在N限制。桉树非根区0～20 cm土壤细菌丰度显著大于根区0～20 cm和非根区20～40 cm土壤。夏季土壤细菌丰度较冬季显著...     

不同耕作模式对稻田土壤真菌丰度及群落结构的影响

为分析我国典型的稻田耕作模式下土壤真菌丰度及群落结构差异,以长期（10 a）4种典型稻田耕作模式为研究对象,设置以下处理：双季稻（DR）、早稻-晚稻（MR）、中稻-油菜（MROR）及中稻-小白菜-油菜（MRPOR）,利用实时荧光定量PCR及高通量测序手段测定土壤真菌的丰度及群落组成。结果显示,双季稻转变为单季稻及水旱轮作模式后显著改变了真菌的丰度,其中双季稻转变为中稻-小白菜-油菜后显著增加了真菌的丰度,相关性分析发现,硝态氮与真菌的丰度呈显著的正相关关系;双季稻转为单季稻及水旱轮作模式后显著改变了真菌的群落结构,冗余分析发现水分含量是影响真菌群落结构最主要的环境因子。综上研究表明,不同轮作模式下稻田土壤真菌群落丰度、组成及多样性存在差异。不同处理下真菌丰度受土壤硝态氮影响较大,而真菌群落结构主要受土壤含水量的影响。     

垄膜沟灌马铃薯测土施肥指标体系——以甘肃省张掖市山丹县为例

[目的]确定施肥指标体系,为垄膜沟灌马铃薯提供精确的施肥配方。[方法]2007—2010年在甘肃省张掖市山丹县进行马铃薯"3414"田间肥效试验,分析不同土壤肥力水平下马铃薯土壤有效养分含量与相对产量的相关性,并依此确定土壤养分丰缺指标和推荐施肥量。[结果]将山丹县马铃薯田间土壤碱解氮、有效磷、速效钾含量等级划分为低、较低、中、较高、高5级,对应推荐施氮量分别为>225.7,193.3~225.7,117.2~193.3,161.0~177.2,<161.0kg/hm2;推荐施磷量分别为>164.3,146.5~164.3,137.6~146.5,128.6~137.6,<128.6kg/hm2;推荐施钾量分别为>166.8,149.7~166.8,141.1~149.7,132.5~141.1,<132.5kg/hm2。经过150个示范点的调研分析发现,利用测土配方施肥技术增产率达9.8%,节约化肥67.5kg/hm2,节本506.3元/hm2,节本增效3 286.5元/hm2。[结论]垄膜沟灌马铃著测土配方施肥技术可以实现普遍增产和增效。     

长期施用家畜废弃物堆肥对土壤剖面15N自然丰度的影响

通过对两个长期田间试验的研究,分析了日本火山灰土(Andisols)及其溶液中15N自然丰度(δ 15N)在土壤剖面的分布,其目的是为了评价δ15N值能否作为预测家畜废弃物氮在迁移转化过程中形成的NO3-N污染的指标.在日本中央农业综合研究中心(NARC)进行了6年的试验处理包括猪场废弃物堆肥(猪粪堆肥),缓释尿素(缓释肥),普通铵态氮肥(普通化肥),及不施肥(对照);而在日本农业研究所(NARI)进行了12年的试验则包括三个施用量的牛场废弃物堆肥(牛粪堆肥),以该地长期不施肥的森林土壤(森林)作为对照.研究结果表明在NARC长期施用猪粪堆肥显著改变了δ15N值在土壤剖面的分布模式,猪粪堆肥小区0～20cm的δ15N值最高,然后按对照≥普通化肥＞缓释肥排列,原因主要为猪粪堆肥本身的δ15N值较高及其随后在土壤中的转化等反应;缓释肥处理后的土壤δ15N值最低,表明缓释肥施入土壤后的循环速率较慢或相对于施肥量其损失较低.在NARI,土壤δ15N值随着施肥量的增加而升高.同样不施肥条件下,NARI的森林土壤剖面的δ15N值比相对应的NARC的对照土壤剖面值高1～2个δ单位.NARC土壤剖面100 cm收集的土壤溶液的δ15N值的大小排列为猪粪堆肥＞普通化肥≥对照＞缓释肥;并且普通化肥小区土壤溶液δ15N最低值出现在剖面深度200～250 cm左右.以上结果显示土壤表层或土壤溶液中的δ15N值将有助于我们在火山灰土地区定性地预测污染物来源.     

安徽省油菜钾肥施用效果及土壤速效钾丰缺指标研究

2005—2009连续4个年度在安徽省冬油菜生产区布置油菜钾肥肥效试验73个,研究施用钾肥对油菜产量和经济效益的影响;并通过建立油菜籽粒相对产量和土壤速效钾含量的关系,确定土壤速效钾丰缺指标。结果表明,油菜施用钾肥具有明显的增产效果,施钾后油菜平均产量达2 558 kg/hm~2,比不施钾增产509 kg/hm~2,增产率为28.1%。施钾每公顷平均增收1 349元,67.1%的试验点产投比2.0,施钾收益显著。13.7%的试验点施钾后增产不增收。以相对产量60%、60%~75%、75%~90%、90%~95%和95%为标准,将土壤速效钾分为"严重缺乏"、"缺乏"、"轻度缺乏"、"适宜"和"丰富"5个等级,处于各等级的土壤面积的比例分别为2.7%、17.8%、65.8%、6.8%和6.8%,对应的丰缺指标分别为30、30~60、60~110、110~140和140 mg/kg。此研究建立的土壤速效钾丰缺指标可为安徽省冬油菜的钾肥管理提供依据。