基于星载ICESat-2/ATLAS数据的森林地上生物量估测

为探讨星载激光雷达数据ICESat-2（Ice,Cloud,and land Elevation Satellite-2）在山地森林地上生物量（Aboveground Biomass,AGB）的估测可行性和方法。以ATLAS（Advanced Terrain Laser Altimeter System）光子点云数据为主要信息源,以滇西北典型山地香格里拉为研究区,结合地面54块实测生物量遥感样地,在前期进行点云数据去噪、分类预处理基础上,对研究区74 873个林地光斑进行冠层参数及地形因子的提取（共计53个变量）,采用非参数模型随机森林回归和超参数优化后的随机森林进行建模,以均方根误差（Root Mean Square Error,RMSE）、决定系数（R2）、总体估测精度（P1）作为模型的评价指标,建立研究区AGB模型。研究结果表明：1）分析以ICESat-2/ATLAS提取的冠层参数、地形因子与生物量的相关性可知,冠层光子总数与生物量具有极显著相关性（P<0.01）,基于陆地卫星的乔木冠层百分比、冠层光子比率、坡度、光子总数、表观反射率与生物量具有显著相关性（0.01 < P <0.05）,可作为山地森林生物量遥感模型参数变量;2）地形因子对ICESat-2/ATLAS光斑遥感建模具有一定的影响,地形坡度因子对模型的贡献率为13.97%,小于基于陆地卫星的乔木冠层百分比、表观反射率与冠层光子总数对模型的贡献率。未加入地形坡度因子的传统的随机森林回归模型R2=0.90、RMSE=11.90 t/hm2、P1为80.06%;加入地形坡度因子后模型精度为：R2=0.91、RMSE=11.01 t/hm2、P1=81.30%;3）进行超参数优化的随机森林回归模型精度明显高于传统的随机森林回归模型,优化后的随机森林模型精度R2为0.93、RMSE为10.13 t/hm2、P1为83.31%,可用来进行山地森林生物量估测。估测的光斑点总生物量为1.32×105 t,光斑点平均生物量为77.41 t/hm2。参数优化后的随机森林构建的山地森林地上生物量模型拟合度精度较高,模型决定系数在0.9以上,估测精度在82%以上,表明ICESat-2在山地提取的光斑参数进行AGB反演具有可行性;ICESat-2光斑点生物量的空间分布表明,高生物量的光斑点主要分布在研究区北部,存在分布不均、区域差异较大的现象,与2021年研究区蓄积量空间分布具有一致性,可用来进行森林地上生物量估测。     

Community composition of ammonia-oxidizing bacteria in the rhizosphere of intercropped wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.), maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.), and faba bean (<Emphasis Type="Italic">Vicia faba</Emphasis> L.)

Cereal/cereal and cereal/legume intercropping systems are popular in the north, northwest, and southwest of China and often result in yield increases compared to monocropping. Rhizosphere interactions may play a significant role in the yield increases, particularly with respect to nutrient availability. The aim of this study was to investigate the effects of intercropping on N availability and community composition of ammonia-oxidizing bacteria in the rhizosphere of wheat, maize, and faba bean at different growth stages. Denaturing gradient gel electrophoresis (DGGE) based on 16S rRNA genes was used to analyze the community composition of bacterial ammonia oxidizers belonging to β-proteobacteria. The results showed that intercropping with faba bean significantly increased nitrate concentrations in the rhizosphere of wheat and maize at the second sampling time (20 June) compared to monocropping or intercropping between maize and wheat. Intercropping significantly affected the community composition of ammonia-oxidizing bacteria in the rhizosphere compared to monocropping, and the effects were most pronounced in the maize/faba bean and wheat/maize intercropping systems when faba bean and wheat were at anthesis and maize was in seedling stage. In wheat/faba bean intercropping, the effects of intercropping on community composition of ammonia-oxidizing bacteria were less pronounced at the seedling stage of the two species but were significant at anthesis.     

Carotenoid Composition and Changes in Sweet and Field Corn (Zea mays) During Kernel Development

Kernels of two carotenoid‐rich cultivars, sweet corn Jingtian 5 and field corn Suyu 29, were compared in terms of carotenoid composition during corn kernel development. The results showed that eight principal carotenoids were characterized by HPLC with diode array detection and atmospheric pressure chemical ionization tandem mass spectrometry with a C30 column. During kernel development, there was a similar trend in the change of total carotenoids for both corn cultivars, and the variation of individual carotenoids was also somewhat similar; violaxanthin, zeaxanthin, lutein, α‐cryptoxanthin, and β‐cryptoxanthin contents had upward trends, whereas neoxanthin content declined all the time, and α‐carotene and β‐carotene had no significant changes. However, the highest levels of the major carotenoids lutein (41.61 µg/g, dry weight) and zeaxanthin (39.59 µg/g, dry weight) obtained in field corn Suyu 29 during the milk stage were higher than those in sweet corn Jingtian 5, whereas the other individual carotenoid levels were significantly lower. Compared with the grain color, highly significant positive correlations were observed between zeaxanthin, lutein, and violaxanthin contents and deeper yellow/orange coloration indicators for field corn Suyu 29, but these relationships were weak for sweet corn Jingtian 5. Potential genetic variation might exist for carotenoid accumulation in sweet and field corn kernels.     

Deep incorporation of corn straw benefits soil organic carbon and microbial community composition in a black soil of Northeast China

‘Deep incorporation of corn straw’ (CSDI) is to concentrate the burial of corn straw into the subsurface soil layer (20–40 cm) and to break the plough pan, thereby creating a loosened plough layer (0–20 cm) and a fertile subsurface soil layer. However, its impacts on soil organic carbon (SOC) and the microbial community remain poorly understood. A field experiment was conducted to investigate the effects of 1-year CSDI (CD1), 3-year CSDI (CD3) and 5-year CSDI (CD5) on soil aggregates and aggregate-associated SOC, as well as bacterial and fungal community characteristics (examined by the high-throughput gene sequencing method). The results demonstrated that SOC and soil fungal diversity were decreased by CD1, but increased by CD3 and CD5. Compared with the control, CD5 promoted 2–0.25 mm soil macroaggregation, significantly increased SOC by 8.94% and aggregate-associated SOC by 5.96%–8.84%, consequently improving the physical protection of SOC by soil aggregates. CD3 and CD5 enhanced the richness and diversity of soil bacteria and fungi, and altered community composition. For soil bacteria, the relative abundance of Acidobacteria and Chloroflexi was increased, while that of Firmicutes, Gemmatimonadetes, Sphingomonas and Bacillus was decreased. For soil fungi, the relative abundance of Ascomycota, Zygomycota, Mortierella and Fusarium was greatly improved, but that of Basidiomycota was reduced. These obvious variations in microbial community structure were beneficial to straw degradation and SOC accumulation. Overall, the optimization of microbial community with CSDI plays a positive role in promoting soil organic matter, nutrient cycling and carbon sequestration, and thus improving soil fertility.     

基于模糊层次分析法的生物燃气产业竞争力评价模型及应用

随着中国能源需求的不断增长和环境保护的日益加强,生物燃气产业越来越受重视,对产业竞争力进行评价以了解地区生物燃气产业发展水平成为急需解决的问题。该文从规模、经济、技术、管理、可持续发展5个方面选择了22个指标,构建了生物燃气产业竞争力评价指标体系。基于层次分析法和模糊综合评判法,提出了生物燃气产业竞争力评价模型,并应用于北京市生物燃气产业竞争力评价。评价结果表明:规模竞争力在差的隶属度综合得分是0.49,制约因素主要是从业人员人数及气体总消费量。经济竞争力指标在中的隶属度综合评分是0.65,制约因素主要是农民增收情况。技术竞争力指标在良的隶属度综合评分是0.54,制约因素主要是人才吸引力情况。管理竞争力指标在中的隶属度综合得分是0.54,制约因素主要有运营管理模式及技术安全管理水平。可持续发展竞争力指标在优的隶属度综合得分是0.51。北京市生物燃气产业竞争力属于中等水平,在废弃物资源化利用能力以及污染物减排方面具有明显优势,在科研投入、技术装备方面具有较高水平,在管理水平、经济效益、产业规模方面等方面处于中等或较差水平,需要进行完善和提升。模型很好的表征了北京市生物燃气产业的现状,研究结果可为北京市生物燃气产业发展提供依据。     

La/P/Ni改性分子筛催化裂解生物油模型化合物

为研究不同分子筛催化剂对生物油催化裂解特性的影响,该文采用稀土元素La、非金属元素P以及活泼金属元素Ni对ZSM-5分子筛催化剂进行改性,在连续式固定床反应器中对乙酸乙酯、二丙酮醇、糠醛和愈创木酚等生物油模型化合物进行催化裂解试验,进而对比HY、HZSM-5、ZSM-5催化剂以及改性后ZSM-5催化剂对模型化合物的催化裂解反应特性以及脱氧效果。试验结果表明:在反应温度为400℃、反应质量空速为4/h条件下,经La/P/Ni改性ZSM-5分子筛催化剂,模型化合物有机相收率提高,结焦率下降;HY分子筛所得有机相收率最低,结焦率最高。模型化合物各组分裂解难易程度由易到难为二丙酮醇乙酸乙酯糠醛愈创木酚;改性后ZSM-5分子筛使组分单一转化率和总转化率均出现下降;HZSM-5分子筛作用下,反应转化率达到最高。模型化合物催化裂解脱氧产物以芳香烃为主,经La改性ZSM-5分子筛作用后,其芳香烃选择性较ZSM-5略微上升;P和Ni改性后,芳烃选择性下降;HZSM-5对于芳香烃选择性最高,达7.36%;HY对于芳香烃选择性最低,仅为3.15%。通过液体产物组分分析进一步探讨模型化合物反应路径,从而为生物油的催化裂解提供一定的理论基础和科学依据。     

黄土高原肥水坑施技术下苹果树根系及土壤水分布

为了解黄土丘陵区雨养条件下山地老果园布设肥水坑(water-wertilizer pit,WFP)技术对红富士老果树(Malus pumila Mill)根系及土壤水分空间分布特征的影响,以无肥水坑处理为对照(CK),利用管式TDR系统监测0~300 cm土层土壤含水率,利用根钻法获得21a生旱地果园0~300 cm土层的根系干质量密度。结果表明:WFP能够显著增加果园含水率低值区间(≥40~80 cm土层)土壤含水率,WFP60(60 cm坑深)处理土壤平均含水率增量(145.4%)最显著。WFP40(40 cm坑深)根际土壤湿润区主要集中在≥40~100cm土层,WFP60在≥20~140 cm土层,WFP80(80 cm坑深)主要集中在深层土壤≥140 cm土层。在0~200cm试验土层,WFP60处理土壤多次平均含水率值都最高,为11.02%,依次为WFP40(10.67%)和WFP80(9.80%)。总根系质量密度WFP60处理最大(594.76 g/m3),WFP40(579.08 g/m3)和WFP80(491.82 g/m3)次之,CK最小(372.12 g/m3)。根系在0~100、≥100~200和≥200~300 cm土层中的分配比例为:CK(69.88%、13.74%和16.38)、WFP40(66.04%、14.26%和19.70%)、WFP60(70.35%、24.08%和5.58%)和WFP80(46.54%、15.04%和38.42%),其根系分布与水分分布正相关。该研究表明WFP能够显著改变土壤水分在不同土层深度的分布,坑深越大向下湿润的土体范围也越深;从而显著促进果树根系的生长和根系在不同湿润土层的分配比例关系。总体而言,WFP60处理效果显著好于WFP40和WFP80处理。研究结果将对黄土高原旱地果园集雨和灌溉制度的制定和肥水坑技术的推广提供参考。     

用核磁共振研究浸种方法对水稻种子吸水量的影响

为寻求较佳浸种方法,该文应用低场核磁共振检测技术,研究了不同的浸种方式及浸种溶剂对水稻种子吸水量的影响。试验利用横向弛豫时间 T2反演谱分析了水稻种子的水分状态变化及吸水特性,发现浸种过程改变了水稻种子内部的水分分布情况,水稻种子吸水量对初始含水率差异不显著(P>0.05),但对各种浸种方法差异显著(P<0.05)。研究表明,采用连续浸种4 h、浸种3 h-晾干1 h-浸种1 h、浸种2 h-晾干1 h-浸种2 h及浸种2 h-晾干2 h-浸种2 h这4种不同的浸种方式时,浸种2 h-晾干1 h-浸种2 h的间歇浸种方式吸水率较高;采用清水、强氯精300倍液、饱和澄清石灰水、质量分数为40%福尔马林的50倍液、100倍液及200倍液6种不同的浸种溶液时,应用质量分数为40%福尔马林50倍液药剂时吸水率较高。低场核磁共振检测技术揭示了水稻种子含水量的影响因素,为浸种过程中吸水量的测定提供了一种有效的方法。     

用低场核磁共振检测水稻浸种过程中种子水分的相态及分布特征

为研究水稻浸种过程中种子的水分相态及其分布特征,利用低场核磁共振快速、无损、准确的检测技术,通过硬脉冲回波序列CPMG(carr-purcell-meiboom-gill sequence)测量水稻种子横向弛豫时间T2,根据横向弛豫时间T2的差异区分种子内部的水分相态及其变化规律。试验结果表明:通过T2反演谱横向弛豫时间T2长短的差异,发现水稻浸种过程中种子内部水分存在结合水、自由水2种水分状态,同时可区分出内层水、中层水、外层水3种水分分层;二者均能通过回归方程合理的估测水稻在浸种过程中种子的吸水率情况;通过T2反演谱信号幅值大小的差异,发现水稻浸种过程中的种子总水含量不断上升,但由于判定依据及划分方式的不同,二者在水分的流动方式上略显差异。低场核磁共振技术对水稻浸种过程中种子内部的水分变化进行了直观的揭示,提供了一种高效的种子水分检测方法。     

浮游动物在生物操纵法除藻中的作用研究

采用室外现场实验和室内受控生态系统实验相结合的方法,研究了富营养化水体中浮游动物对藻类生长的控制作用。对浮游动物与藻类的计数与测量数据,利用SPSS统计软件进行了方差分析（LSD多重比较法）和相关性分析。实验结果显示,总磷含量比总氮含量对浮游动物生长的影响更大。浮游动物与藻类之间呈现显著或极显著相关关系,说明浮游动物群体,尤其甲壳类群体,在适当条件下对藻类群体以及其中的蓝藻有一定的控制作用。适当的鱼类密度下,浮游动物能够起有效的控藻作用,但鱼类密度过高会抑制该作用。底泥在生态系统中起重要作用,能够影响浮游动物对藻类的摄食力。