基于GAM的长江口鱼类资源时空分布及影响因素

根据2006至2017年长江口及其邻近海域鱼类资源调查,运用广义加性模型研究长江口鱼类资源密度与环境因子之间的关系,并对2017年鱼类资源密度的时空分布进行预测。结果显示,春夏秋冬四个季节最佳GAM偏差解释率分别为69.6%、55.9%、51.4%和47.4%,交叉验证回归线斜率的平均效应为0.62～0.88。盐度、水温和溶解氧是影响长江口鱼类资源密度的主要环境影响因子且在不同季节对鱼类资源密度有不同的影响机制。总体上,在春、夏、秋季,盐度与鱼类资源密度之间存在正向相关性;在夏、秋、冬季,水温对鱼类资源密度有显著影响,在秋季与鱼类资源密度之间存在正向相关性;在春、秋、冬季,溶解氧对鱼类资源密度有显著影响,在冬季与鱼类资源密度之间存在正向线性相关。研究表明,2017年夏季鱼类资源密度较高;在长江口南支的自然延伸水域存在鱼类资源密度的相对低值,在崇明岛向海自然延伸方向水域存在鱼类资源密度的相对高值。后续研究将对长江口鱼类资源进行不同生态类型区分,以期更加准确地掌握影响各生态类型鱼类时空分布的环境因素及其时空分布信息。     

控灌改良对黄河三角洲盐碱地玉米生长与产量的影响研究

本文以黄河三角洲盐碱地玉米为研究对象,利用黄河泥沙对盐碱地进行改良试验,分析不同黄河泥沙施用量和不同灌水量水平对玉米株高、叶面积、干物质量和产量的影响,探讨适宜的泥沙施用量和灌水量。结果表明：玉米的生长和产量都随着泥沙施用量和灌水量的增加而增大,泥沙施用量均大于灌水量对其的影响。株高、叶面积指数、干物质量产量均在在泥沙施用量为6cm,灌水量为150mm处理最大,干物质积累量在成熟期最大为20460kg/hm_²；夏玉米产量最大为11220kg/hm_²。     

Influence of salinity and moisture on the threshold shear velocity of saline sand in the Qarhan Desert,Qaidam Basin of China: A wind tunnel experiment

Determination of the threshold shear velocity is essential for predicting sand transport, dust release and desertification. In this study, a wind tunnel experiment was conducted to evaluate the influence of salinity and moisture on the threshold shear velocity of saline sand. Saline sand samples (mean particle size of 164.50-186.08 μm and the total silt, clay and salt content of 0.80%-8.25%) were collected from three saline sand dunes (one barchan dune and two linear dunes) in the Qarhan Desert, Qaidam Basin of China. Original saline sand samples were placed in two experimental trays for wet and dry processing to simulate deliquescence and desiccation, respectively. Surface moisture content ranging from 0.30% to 1.90% was generated by the steam method so that the saline sand can absorb water in a saturated water vapor environment. The motion of sand particles was determined by the observers with a solid laser. The laser sheet (0.80 cm thick), which was emitted by the solid laser, horizontally covered the sand surface and was bound to the sand. Results show that the cohesion of saline sand results from a combination of salt and water. The threshold shear velocity increases exponentially with the increase in crust thickness for the linear sand dunes. There is a positive linear correlation between the original moisture content and relative threshold shear velocity. The threshold shear velocity of dewatered sand is greater than that of wet sand with the same original moisture content. Our results will provide valuable information about the sand transport of highly saline soil in the desert.     

基于CA-Markov模型的锡林河流域土地利用变化及预测分析

研究土地利用变化特征及预测未来土地利用变化的趋势，对经济平衡发展、提高生态环境质量、实现土地资源合理利用具有重要意义。以锡林河流域为研究区，对Landsat 2000、2005、2010年和2015年4期遥感数据进行目视解译，采用土地利用结构分析方法、重心迁移模型和CA-Markov模型，分析研究区16 a间土地利用演变特征，并对2030年土地利用情况进行预测。结果表明:1)2000-2015年，草地、林地和耕地呈波动变化，水域面积缓慢增加，建设用地不断扩张，未利用地面积在不断减少。建设用地、耕地和未利用地重心具有明显的方向性移动，耕地先向南后向北移动，建设用地主要向西北方向扩张，未利用土地重心持续向北移动。2)研究区综合土地利用动态度为5.70％，变化速率较快；锡林浩特市和各苏木土地利用变化速率差异较大，总体表现为中游＞下游＞上游；不同土地利用类型动态度为建设用地＞水域＞林地＞耕地＞未利用土地＞草地，即建设用地变化最快。3)研究区土地利用变化的主要方向为草地和未利用地的相互转换、耕地和草地的互相转换以及建设用地的不断扩张。4)2030年预测结果表明，耕地面积继续增加，速率有所下降，重心向西南方向移动；林地延续之前变化趋势，稳中有升；草地和未利用地面积继续减少，且未利用地重心持续向北移动；建设用地扩张明显，重心向锡林浩特市中心移动，速度减缓；水域有少量增加。CA-Markov模型与土地利用重心迁移模型相结合，实现了对未来耕地、建设用地和未利用土地的迁移方向的预测，可以为研究区提高草地退化防治效果、土地管理政策的制定和实施、城乡建设、土地利用规划等提供理论指导。     

Investigation of crop evapotranspiration and irrigation water requirement in the lower Amu Darya River Basin,Central Asia

High water consumption and inefficient irrigation management in the agriculture sector of the middle and lower reaches of the Amu Darya River Basin(ADRB)have significantly influenced the gradual shrinking of the Aral Sea and its ecosystem.In this study,we investigated the crop water consumption in the growing seasons and the irrigation water requirement for different crop types in the lower ADRB during 2004–2017.We applied the FAO Penman–Monteith method to estimate reference evapotranspiration(ET0)based on daily climatic data collected from four meteorological stations.Crop evapotranspiration(ETc)of specific crop types was calculated by the crop coefficient.Then,we analyzed the net irrigation requirement(NIR)based on the effective precipitation with crop water requirements.The results indicated that the lowest monthly ET0 values in the lower ADRB were found in December(18.2 mm)and January(16.0 mm),and the highest monthly ET0 values were found in June and July,with similar values of 211.6 mm.The annual ETc reached to 887.2,1002.1,and 492.0 mm for cotton,rice,and wheat,respectively.The average regional NIR ranged from 514.9 to 715.0 mm in the 10 Irrigation System Management Organizations(UISs)in the study area,while the total required irrigation volume for the whole region ranged from 4.2×109 to 11.6×109 m3 during 2004–2017.The percentages of NIR in SIW(surface irrigation water)ranged from 46.4%to 65.2%during the study period,with the exceptions of the drought years of 2008 and 2011,in which there was a significantly less runoff in the Amu Darya River.This study provides an overview for local water authorities to achieve optimal regional water allocation in the study area.     

Spawning movements of humpback whitefish in interior Alaska rivers

This study was conducted to describe the spawning movements and identify spawning areas for humpback whitefish Coregonus pidschian in the Minto Flats–Chatanika River complex, Alaska, during 2008 and 2009. Radio transmitters were surgically implanted in humpback whitefish in 2008 (N = 60) and 2009 (N = 100), and fish positions were determined through a combination of boat and aerial surveys and fixed receiving stations. Two spawning areas were identified: one in the Chatanika River downstream of the Elliot Highway Bridge and the other in the Tanana River near Fairbanks. Humpback whitefish dispersed from the wetland complex of Minto Flats in June, moved upstream through late August, arrived at the spawning areas in early September and began moving downstream in early October. In 2009, spatially segregated movements were observed when approximately 40% of the radio‐tagged humpback whitefish moved to the Tanana River, suggesting that humpback whitefish in Minto Flats are comprised of mixed spawning stocks. These study results provide a complete account of humpback whitefish movements and their associated spawning habitats, which will allow for better‐informed management strategies.     

种植方式对青海湖流域人工草地植被和土壤养分特征的影响

为探究多年生人工草地在青海湖流域的适应性和稳定性,本研究以青海草地早熟禾(Poa pratensis. Qinghai)和青海中华羊茅(Festuca sinensis. Qinghai)单播及混播人工草地为研究对象,分析不同种植方式下人工草地植被和土壤养分特征的变化。结果表明：青海草地早熟禾+青海中华羊茅混播草地和青海草地早熟禾单播草地的生物量和盖度高于青海中华羊茅单播草地,且在生长旺期(8月),青海草地早熟禾+青海中华羊茅混播草地生物量最高,为586.2 g·m^-2;青海草地早熟禾单播、青海中华羊茅单播和青海草地早熟禾+青海中华羊茅混播草地间土壤有机质、全氮、全磷、硝态氮、铵态氮和土壤含水量在相同土壤深度下差异不显著,但土壤氮、磷及有机质间存在显著的相关性。综上所述,在青海湖流域建植青海草地早熟禾+青海中华羊茅混播型人工草地可以获得较高的产量,但需在种植和管理过程中协调好土壤氮、磷间的关系。     

准噶尔盆地南部农区野生饲用植物资源研究

为了解准噶尔盆地南部农区野生饲用植物资源,调查研究了该区域野生饲用植物的科属组成及其生活型和生态型特点,并对其适口性和营养价值进行了分析。结果表明：该区共有野生饲用植物34科145属214种,优势科有禾本科(38属71种)、藜科(18属22种)、菊科(15属21种)、豆科(14属19种)、苋科(8属11种)、十字花科(8属10种);生活型植物以草本植物(1～2年生124种,多年生62种)为主,占86.92%,木本植物有28种,占13.08%;生态型植物以中生为主(183种)。依据适口性可将该区野生饲用植物划分为优、良、中、低4个等级,其中优等95种、良等77种、中等36种、低等6种。营养成分丰富且适口性较好的饲用植物主要集中在禾本科(21种)、豆科(17种)和藜科(13种)。     

黑河上游冰沟流域3种林地土壤有机碳分布特征与土壤特性的关系

研究了青海省祁连县黑河上游冰沟流域3种林地的土壤有机碳分布特征与土壤特性的关系,以期为黑河上游冰沟流域水源涵养研究提供科学依据。结果表明,3种林地0-60mm土层有机碳密度表现为针叶林森林灌丛阔叶林,针叶林有机碳密度为7.18kg·m-2,是森林灌丛、阔叶林的1.24和1.58倍,针叶林、森林灌丛、阔叶林0-10mm土层有机碳密度分别为13.22、9.49和8.62kg·m-2,是剖面有机碳密度均值的1.84、1.63和1.89倍。3种林地0-60mm土层自然含水量、团聚体、全氮均值表现为针叶林森林灌丛阔叶林,而容重、物理性沙粒、pH均值表现为针叶林森林灌丛阔叶林。3种林地土壤有机碳含量与自然含水量、团聚体、全氮之间呈显著的正相关关系(P0.05),与容重、物理性沙粒、pH之间呈显著的负相关关系。     

闽江下游山地巨桉无性系施肥试验研究

对巨桉无性系施用不同肥料组合的试验研究结果表明:以火烧垃圾土做基肥再配施适量的尿素做追肥,组成了有机—无机复混肥体系,其施用效果明显优于纯化肥类肥料组合,不但能明显提高林分生产力、维持地力,而且经济效益较好,充分显示出有机无机混合肥的施用优势;采用火烧垃圾土2 kg.株-1(基肥)+尿素200 g.株-1(追肥)的施肥方案,2年生时林分平均树高、胸径、材积和蓄积分别可达9.41 m、9.51 cm、0.0335 m3和53.72 m3.hm-2,投入产出比高达1∶2.9,经济纯收入是纯化肥类肥料组合的2.0~2.8倍,符合桉树短工林集约经营和持续发展方向,值得推广应用。