开沟起垄措施对植烟土壤和烟叶产值的影响

为探明烟稻轮作制度下,烟田起垄开沟对植烟土壤化学性质及烟株生长、产质量等影响,以稻茬烟田为试验平台,设置2个开沟深度[A1：浅沟（垄间开沟15cm）;A2：深沟（垄间开沟25cm）]和2个起垄时间[B1：移栽前10d起垄（常规起垄）;B2：翻耕后起垄],于2018年取样,系统分析不同处理对土壤pH、主要养分含量和烟株农艺性状、干物质积累及经济性状的影响。研究结果表明,烟株各个主要生育时期深沟+翻耕后起垄处理（A2B2）的有效叶片数、烟叶最大叶长、叶宽和株高均优于其他处理;且该处理能有效改善土壤速效养分含量,土壤pH处于优质烤烟生产要求范围;同时烟株物质生产能力强,干物质积累多,在各器官间分配合理;烤烟经济性状也表现为该处理的烟叶产量、产值及上等烟比例较高,表现较优。总之,翻耕后起垄+深开沟处理（A2B2）有利于烟株生长,提高烟株的品质,为烟叶优质适产奠定了生物学基础。     

To sea or not to sea? Multiple lines of evidence reveal the contribution of non‐diadromous recruitment for supporting endemic fish populations within New Zealand's longest river

1. Otolith microchemistry was used to identify marine‐ versus freshwater‐derived recruitment of three native freshwater fish species belonging to the southern hemisphere family Galaxiidae, in New Zealand's longest river system, the Waikato River.
2. Water chemistry data for trace elements and ⁸⁷Sr/⁸⁶Sr isotope ratios were collected from five lentic and 10 lotic water bodies throughout the lower river floodplain. Potential spawning sites for galaxiids were compared with values obtained by laser ablation inductively coupled mass spectrometry (LA‐ICPMS) depth profiling of young‐of‐the‐year otoliths sampled from fish in nine lower river catchment sites.
3. Otolith chemical signatures from the larval rearing period indicated that catchment‐scale recruitment for two species, Galaxias argenteus (Gmelin, 1789) and Galaxias fasciatus Gray, 1842, was driven predominantly by non‐diadromous recruitment from one lake (Lake Waahi). In contrast, diadromous recruitment appeared to be more common for Galaxias maculatus (Jenyns, 1842); however, non‐diadromous specimens were also identified for the first time from a New Zealand river.
4. Reversing lake outlet flows linked to river stage appears be important in facilitating the dispersal of rheotactic larvae out of lakes, suggesting that lake outflow management at key times could be used to sustain this ecologically important function.
5. This study highlights that some water bodies can supply a disproportionately large number of recruits to support fish populations within the wider riverscape. Identifying these water bodies and managing them to sustain recruitment is key to the conservation of non‐diadromous Galaxiidae in this modified lowland environment

     

播种深度对花生生育进程和叶片衰老的影响及其生理机制

在春播、土壤水分适宜以及起垄覆膜种植模式条件下,选用大花生品种山花108,设置3、5、7、9、11、13和15 cm (SD3、SD5、SD7、SD9、SD11、SD13和SD15) 7种播种深度,研究播种深度对花生生育进程、叶绿素含量、光合性能、干物质积累量、抗氧化酶活性及产量形成的影响。2年结果表明,播种深度明显影响花生出苗时间,与SD5处理相比, SD15处理的出苗期推迟5 d,产量形成期缩短2.5 d。播深过浅(3 cm)或过深(7 cm)显著降低了植株主茎高和侧枝长,导致叶面积指数(LAI)显著降低;且降低了产量形成期叶片叶绿素含量和光合速率,导致植株干物质积累量显著降低。播种过深(7cm)显著降低了产量形成期叶片可溶性蛋白含量和超氧化物歧化酶(SOD)及过氧化物酶(POD)活性,丙二醛(MDA)含量显著提高,导致叶片膜脂过氧化加剧。各播深处理相比,SD5处理的荚果和籽仁产量较高,主要是由于其单株结果数、单果重及出仁率的提高,播种深度超过7 cm后,减产显著。因而,春花生适宜的播种深度应控制在5 cm。     

基于多指标评价和分形维数的坡耕地优先流定量分析

以重庆紫色砂岩区坡耕地田间染色示踪试验为基础,采用形态学和统计学方法,对3种坡耕地土壤剖面染色图像进行指标提取,运用多指标评价法确定了优先流指数PFI,并结合几何学中的分形理论,定量评价了土壤优先流的发育程度。结果表明:6个优先流特征指标(优先流区染色面积比、基质入渗深度、优先流分数、长度指数、峰值指数和变异系数)均表现出南瓜地和柑橘地的优先流程度高于玉米地;优先流指数PFI由大到小为南瓜地(0.88)、柑橘地(0.77)、玉米地(0);通过Fractal Fox 2.0软件计算得到的优先流湿润峰迹线分形维数由大到小为南瓜地、柑橘地、玉米地。与土壤优先流指数PFI进行比较,所得结果基本一致,说明利用分形维数来评价土壤优先流发育程度是准确可行的。     

基于IL-HMMs预测模型的地下水埋深预测研究

以西北干旱典型县域磴口县为研究区,基于增量学习的改进隐马尔可夫预测模型(IL-HMMs),对区域地下水埋深进行了预测研究。为检验IL-HMMs模型预测效果,将模型预测结果与2013年长观井的实测数据进行了比较;同时为检验模型的优劣性,与未经增量学习的隐马尔可夫模型(HMMs)、加权马尔可夫链(WMCP)和BP神经网络(BP neural network,BPNN)预测模型的预测结果进行了比较。结果表明:与其他几种预测模型相比,IL-HMMs模型预测精度显著提高,误差更小,有较好的鲁棒性。并使用IL-HMMs模型对2018年地下水埋深进行了预测,预测结果表明,2018年地下水年平均埋深略有增加、局部区域地下水埋深增量加剧。基于IL-HMMs模型的地下水埋深预测具有很好稳定性的同时对新数据加入又有很好的鲁棒性,可为地下水埋深动态预测提供思路与方法补充,为区域地下水资源开发利用和保护提供重要依据。     

两种模型分析方法下冬小麦根系吸水深度的对比研究

为了研究冬小麦根系吸水深度,应用塑料管土柱法在田间进行冬小麦种植试验,测定了冬小麦越冬期、拔节期、抽穗期、灌浆期和成熟期不同土层深度土壤水稳定同位素值,并应用耦合模型和IsoSource多元线性模型对比分析了水源贡献率。结果表明,冬小麦在越冬期、返青期主要利用0~20 cm土层的土壤水,拔节期主要吸水深度为0~40 cm;抽穗期,基于耦合模型的主要吸水深度为0~40 cm,基于IsoSource多元线性模型的为0~40 cm和80~180 cm;灌浆期,基于耦合模型和IsoSource多元线性模型的主要不同吸水深度为180~200 cm,且基于耦合模型的该层贡献率明显高于IsoSource多元线性模型;成熟期主要利用0~40 cm和80~100 cm土层的土壤水,基于2种模型的分析结果相同。应用耦合模型求解贡献率,当分组较多且组间水稳定同位素差异较小时,应结合其他方法来保证其准确性。     

积雪特性参数分析及雪深模型建立

通过2015~2016年冬季积雪观测试验,测量自然条件下雪深、雪层温度、雪层密度、雪层液态含水率等积雪特性参数,分析积雪特性参数影响因子和发育变化规律,构建径向基神经网络雪深模型。结果表明,空气、地表温度及水汽压是影响雪参数发育三大主要气象因子。在时长为124 d覆雪期中,雪深最大平均融雪速率达3.20 mm·d-1,出现在融雪后期。雪层密度随雪深增加波浪式上升,其中稳定期全层密度0.1~0.4 g·cm-3;雪层液态含水率0.5%~3.5%,分层液态含水率中层较大,积雪表层和底部波动较小;全层积雪孔隙率平均值为72.3%,积底层孔隙率廓线下降最快,极差最大。经两次优化后,雪深模型最大绝对误差为0.614 1 cm,最大相对误差为5.85%,模拟精度控制在6 mm以内。     

The importance of sub‐peat carbon storage as shown by data from Dartmoor,UK

Peatlands are highly valued for their range of ecosystem services, including distinctive biodiversity, agricultural uses, recreational amenities, water provision, river flow regulation and their capacity to store carbon. There have been a range of estimates of carbon stored in peatlands in the United Kingdom, but uncertainties remain, in particular with regard to depth and bulk density of peat. In addition, very few studies consider the full profile with depth in carbon auditing. The importance of sub‐peat soils within peatland carbon stores has been recognized, but remains poorly understood and is included rarely within peatland carbon audits. This study examines the importance of the carbon store based on a study of blanket peat on Dartmoor, UK, by estimating peat depths in a 4 × 1 km survey area using ground penetrating radar (GPR), extraction of 43 cores across a range of peat depth, and estimation of carbon densities based on measures of loss‐on‐ignition and bulk density. Comparison of GPR estimates of peat depth with core depths shows excellent agreement, to provide the basis for a detailed understanding of the distribution of peat depths within the survey area. Carbon densities of the sub‐peat soils are on average 78 and 53 kg C/m³ for the overlying blanket peat. There is considerable spatial variability in the estimates of total carbon from each core across the survey area, with values ranging between 56.5 kg C/m² (1.01 m total depth of peat and soil) and 524 kg C/m² (6.63 m total depth). Sub‐peat soil carbon represents between 4 and 28 per cent (mean 13.5) of the total carbon stored, with greater values for shallower peat. The results indicate a significant and previously unaccounted store of carbon within blanket peat regions which should be included in future calculations of overall carbon storage. It is argued that this store needs to be considered in carbon audits.     

梯形明渠水力学特征水深的解析计算式研究

通过数学理论分析,推出了梯形明渠的临界水深和正常水深高精度解析计算式,并与现有文献相关计算式进行了对比分析。结果表明,新推出的临界水深计算式相对误差小于0.3%;当梯形明渠坡比0.1~7时,新推出的正常水深初值计解析算公式相对误差一般小于3%;另外,给出了收敛速度更快的正常水深迭计算公式,且在m1时正常水深计算公式在初值迭代一次后其误差均小于0.5%。新推出的梯形明渠临界水深和正常水深解析计算式方便简捷、精度可靠。     

地埋滴灌点源入渗土壤水分运动规律实验研究

通过室内砂土中进行地埋滴灌的实验,对地埋滴灌在砂土中的适应性进行初步研究,为田间试验布置提供依据。通过分析湿润锋的推移速率、特征点的土壤含水率变化规律,发现湿润锋推移速率先是径向大于垂向,随着灌水时间和灌水量增加,水平方向和垂向的湿润锋和含水率趋于平衡。根据对比滴灌带埋深15和20 cm特征点的含水率变化情况,得出埋深15 cm节水效果更好,更利于作物生长。实验还得出湿润比能作为滴灌灌水参数的指标,由于作物种植的间距和作物根系深度之比基本小于1.0,因此在田间实际灌溉中湿润比应控制在1.0左右。