CO2与养分交互作用对番茄幼苗叶片碳、氮积累及碳、氮比动态的影响

营养液栽培条件下,以番茄(品种,合作906)为材料,研究CO2施肥与4种不同养分供应强度的交互作用对番茄幼苗生长及其叶片中的碳、氮浓度与碳、氮比动态变化的影响。结果表明,在不同营养液养分浓度下,CO2施肥能增加番茄幼苗生物量的积累,提高生长速度;增加番茄幼苗叶片中氮、碳积累量与吸收速率;而且对CO2作用效果的响应随营养液养分浓度的提高而增加。在所有处理中碳、氮积累量与吸收速率随生育期的延长呈上升趋势。说明在番茄育苗后期要增加施肥量,而且在CO2施肥的情况下施肥量增加的量要大。CO2施肥对生长在不同营养液中番茄叶片中的碳、氮比在不同生长阶段的影响是不同的,但在同一CO2浓度条件下,番茄幼苗各个取样阶段均表现为碳、氮比随营养液浓度的降低而增加。对番茄幼苗碳、氮积累量、总干生物量与生长时间的关系研究表明,氮积累量、总干生物量与生长时间均符合二次曲线变化。     

Temporal and spatial dynamics of soil solution C and N concentrations during Lolium perenne L. sward establishment and the effects of elevated CO2 and N additions

There is now clear evidence for a prolonged increase in atmospheric CO₂ concentrations and enrichment of the biosphere with N. Understanding the fate of C in the plant-soil system under different CO₂ and N regimes is therefore of considerable importance in predicting the environmental effects of climate change and in predicting the sustainability of ecosystems. Swards of Lolium perenne were grown from seed in a Eutric Cambisol at either ambient (ca. 350 μmol mol⁻¹) or elevated (700 μmol mol⁻¹) atmospheric pCO₂ and subjected to two inorganic N fertilizer regimes (no added N and 70 kg N ha⁻¹ month⁻¹). After germination, soil solution concentrations of dissolved organic C (DOC), dissolved inorganic N (DIN), dissolved organic N (DON), phenolics and H⁺ were measured at five depths down the soil profile over 3 months. The exploration of soil layers down the soil profile by roots caused transient increases in soil solution DOC, DON and phenolic concentrations, which then subsequently returned to lower quasi-stable concentrations. In general, the addition of N tended to increase DOC and DON concentrations while exposure to elevated pCO₂ had the opposite effect. These treatment effects, however, gradually diminished over the duration of the experiment from the top of the soil profile downwards. The ambient pCO₂ plus added N regime was the only treatment to maintain a notable difference in soil solution solute concentration, relative to other treatments. This effect on soil solution chemistry appeared to be largely indirect resulting from increased plant growth and a decrease in soil moisture content. Our results show that although plant growth responses to elevated pCO₂ are critically dependent upon N availability, the organic chemistry of the soil solution is relatively insensitive to changes in plant growth once the plants have become established.     

Carbon fluxes in soil food webs of increasing complexity revealed by C labelling and C natural abundance

Soil food webs are mainly based on three primary carbon (C) sources: root exudates, litter, and recalcitrant soil organic matter (SOM). These C sources vary in their availability and accessibility to soil organisms, which could lead to different pathways in soil food webs. The presence of three C isotopes (¹²C, ¹³C and ¹⁴C) offers an unique opportunity to investigate all three C sources simultaneously. In a microcosm experiment we studied the effect of food web complexity on the utilization of the three carbon sources. We choose an incomplete three factorial design with (i) living plants, (ii) litter and (iii) food web complexity. The most complex food web consisted of autochthonous microorganisms, nematodes, collembola, predatory mites, endogeic and anecic earthworms. We traced C from all three sources in soil, in CO₂ efflux and in individual organism groups by using maize grown on soil developed under C₃ vegetation and application of ¹⁴C labelled ryegrass shoots as a litter layer. The presence of living plants had a much greater effect on C pathways than food web complexity. Litter decomposition, measured as ¹⁴CO₂ efflux, was decreased in the presence of living plants from 71% to 33%. However, living plants increased the incorporation of litter C into microbial biomass and arrested carbon in the litter layer and in the upper soil layer. The only significant effect of food web complexity was on the litter C distribution in the soil layers. In treatments with fungivorous microarthropods (Collembola) the incorporation of litter carbon into mineral soil was reduced. Root exudates as C source were passed through rhizosphere microorganisms to the predator level (at least to the third trophic level). We conclude that living plants strongly affected C flows, directly by being a source of additional C, and indirectly by modifying the existing C flows within the food web including CO₂ efflux from the soil and litter decomposition.     

Influence of temperature on CO2 evolution,microbial biomass C and metabolic quotient during the decomposition of two humic forest horizons

The decomposition of the litter layer and the humic mineral horizon from a beech forest site was studied at temperatures of 5, 12, and 22°C for both substrates and additionally at 32°C for beech litter. Weight losses, basal and substrate-induced CO₂ production, and the extractable biomass C were monitored periodically during a 2-year incubation period. Weight losses and microbial activity were controlled by substrate quality and temperature. No significant differences were found between 5 and 12°C in decomposition, biomass C, and the metabolic quotient in the humic mineral horizon. The decay of beech litter and the humic mineral horizon was highest at 22°C but was faster in the litter material by a factor of 2.9 on average. In the glucose-amended samples, the relationship among the CO₂-C fluxes was 1:1:2:3 at temperatures of 5, 12, 22, and 32°C in the litter layer, and 1: 2: 2.4 at 5, 12, and 22°C in the A horizon, respectively. The microbial activity in the humic mineral horizon was only 2–11% of that in the litter layer. The level of biomass C remained constant over 1 year and no significant differences were obtained from the 12 and 22°C treatments in the litter layer.     

用超临界CO2脱除绿茶浓缩液中咖啡碱的工艺研究

对绿茶浓缩液中咖啡碱的超临界CO₂萃取工艺进行了研究，通过4因素正交试验探讨了浓缩液的浓度、操作压强、操作温度、萃取时间对咖啡碱脱除率的影响。结果表明，超临界CO₂萃取技术可以有效地脱除绿茶浓缩液中大部分的咖啡碱，在此基础上完成了用超临界CO₂脱除绿茶浓缩液中咖啡碱的连续作业试验，从而获得了加工脱咖啡碱绿茶浓缩液或速溶绿茶的新工艺。     

淮山品种"桂淮2号"的选育及栽培研究

淮山为薯蓣科薯蓣属多年生蔓性块茎类植物，是药食兼用的高效经济作物。通过优良单株筛选，结合群体观察以及植物学、生理学、产量和营养品质等相关研究，从广西地方种质资源中选育出淮山品种“桂淮2号”，并介绍其特征特性和田间肥水管理及病虫害防治等栽培技术要点。该品种具有淀粉含量高、矿质营养丰富等特点，可作为药材加工和菜用、粮用、饲用等。     

CO2施肥对黄瓜幼苗矿质营养吸收与分配的影响

以土培和砂培黄瓜幼苗为试材，研究CO₂施肥对植株矿质营养吸收和分配的影响。结果表明：每天上午以1100±100 μl/L CO₂浓度施肥3 h或上、下午各施肥3 h明显降低植株各部位多数矿质元素的含量，CO₂施肥时间延长，降幅增大。CO₂施肥增强了黄瓜对矿质元素的吸收能力，使单株吸收总量显著增加，且施肥时间越长，吸收数量越多。因此，在CO₂施肥的同时应增加矿质营养的供给。     

利用SAR影像与多光谱数据反演广域土壤湿度

针对基于主动微波遥感途径开展广域土壤湿度反演的过程中,对植被和土壤粗糙度影响难以进行有效估算的问题,该研究联合多极化雷达和原始多光谱数据源,提出一种改进的卷积神经网络(Improved Convolutional Neural Network,ICNN)方法。该方法采用不同尺寸的卷积核对原始变量进行一维卷积运算,自适应提取能反映测区土壤湿度时空差异的高级特征维;同时,去除了传统卷积神经网络结构中的池化层,保证提取的特征信息完整。试验结果表明,在边长超过100 km的四川盆地研究区域内,模型预测值与样本数据相关系数达到0.934,预测值偏差服从均值趋近于0的正态分布,均方根误差为1.45%,误差分布范围小于6.3%,结果具有较高的可靠性。该方法可为精准农业、旱涝灾害等领域的广域监测研究提供一定的支撑。     

作物—CO2环境模拟装置及评价

利用作物—ＣＯ₂环境模拟装置，探讨未来大气ＣＯ₂浓度倍增与作物生长关系的实验研究，已在各国取得不同程度的进展。该文简要综述了近年来国外有关的实验装置概况和发展动向，概述了三种类型装置（封闭式气室、开顶式气室、开放式系统）的结构、性能、特色及其应用，并作出了综合评价。     

秸秆还田对灌溉玉米田土壤反硝化及N2O排放的影响

运用乙炔抑制技术研究了不同施氮水平下秸秆还田对灌溉玉米田土壤反硝化反应和氧化亚氮(N2O)排放的影响。结果表明,土壤反硝化速率及N2O的排放受氮肥施用、秸秆处理方式及其交互作用的显著影响。与秸秆燃烧相比,不施氮或低施氮水平时,秸秆还田可刺激培养初期反硝化反应速率及N2O排放,增加培养期间N2O平均排放通量;高施氮水平时,秸秆还田可降低反硝化反应速率及反硝化过程中的N2O排放。秸秆还田可降低反硝化中N2O/N2的比例。