Temporal changes in mixing effects on litter decay and nitrogen release in a boreal riparian forest in northeastern China

In riparian forests,litter decay provides essential energy and nutrients for both terrestrial and fluvial ecosystems.Litter mixing effects(LMEs)are crucial in regulating litter decay and nutrient dynamics,yet how LMEs change over time is unclear in riparian forests.In this study,leaf litter of three common species(Alnus sibirica Fisch.ex Turcz,Betula platyphylla Sukaczev,and Betula fruticosa Pall.)were mixed in an equal mass ratio and LMEs were measured for mass and nitrogen(N)remaining in whole litter mixtures over a 3-year period in a boreal riparian forest,northeastern China.LMEs were also assessed for component litter mass and N remaining by separating litter mixtures by species.During the decay of litter mixtures,antagonistic effects on mass and N remaining were dominant after one and two years of decay,whereas only additive effects were observed after three years.LMEs correlated negatively with functional diversity after the first and two years of decay but disappeared after three years.When sorting litter mixtures by species,non-additive LMEs on mass and N remaining decreased over incubation time.Moreover,non-additive LMEs were more frequent for litter of both B.platyphylla and B.fruticosa with lower N concentration than for A.sibirica litter with higher N concentration.These results indicate that incubation time is a key determinant of litter mixing effects during decay and highlight that late-stage litter mixture decay may be predicted from single litter decay dynamics in boreal riparian forests.

基于眼动追踪控制的智能制造装备机制研究

智能制造装备行业长期以来着重强调技术,致使制造技术虽日益成熟,但外部形式相对落后。针对该问题,在不同种类的实验对象上进行测试研究。首先,将眼动追踪控制算法与VR仿真技术相结合,对三款微电子技术方面的机台主机设备进行局部调整效果实验。然后,通过分析被试对三款设备方案的总注视时长、平均注视时间、注视频率等评估指标,确定核心视觉倾向,以直观的数据来分析方案的优劣。最后,采用了最佳决策控制算法来提高工业智能制造建设的设计效率。实验结果验证了眼动追踪控算法在智能制造装备中的可行性,能够显著提高智能制造装备的质量与效率。

加速溶剂萃取同步净化-同位素内标-气相色谱-高分辨质谱测定水产品中32种多氯联苯

建立了加速溶剂萃取同步净化-同位素内标-气相色谱-高分辨质谱同时测定水产品中32种多氯联苯含量的方法。通过在加速溶剂萃取仪中加入2 g无水硫酸钠、1 g弗罗里硅土、50 g中性氧化铝作为吸附剂实现同步净化的效果,萃取溶剂为二氯甲烷-正己烷(1∶1,v/v),萃取温度为100℃,循环2次。萃取结束后分别用0.5 mL浓硫酸净化两次,净化液浓缩定容后,采用气相色谱-高分辨质谱测定,同位素内标法定量。32种多氯联苯在0.1~20μg/L范围内平均相对响应因子(RRF)的相对标准偏差(RSD)值(n=7)均小于15%,定量限(S/N=10)为0.3~1.9 ng/kg。在草鱼和海鲈鱼空白基质中做加标回收试验,添加水平为5、20和50 ng/kg,得到的平均回收率为71.9%~119.0%(n=6),RSD为3.5%~19.6%。该方法背景干扰低,灵敏度高,重现性好,回收率稳定,适用于水产品中多氯联苯的检测。

蔬菜水果中菊酯类农药残留快速检测的方法研究

为研究一种蔬菜水果中菊酯类农药残留快速检测方法,通过选购市场上常见的胶体金免疫层析产品及菊酯类农药,对蔬菜水果中菊酯农残的快速检测进行前处理步骤的优化,并考察每种胶体金免疫层析产品在果蔬基质样品检测中的灵敏度、特异性、假阳性率、假阴性率和准确度,以实现胶体金免疫层析产品的整体性评价。结果表明,直接稀释法检测大白菜、韭菜和柑橘时,检测限较高,无法满足检测要求;直接提取法适用于大白菜、韭菜和柑橘的快速检测,检测限为2 mg/kg。方法学验证结果表明:以大白菜、韭菜和柑橘作为空白基质的检测限为2 mg/kg,灵敏度均为100%,特异性为100%,假阳性率为0,假阴性率为0。该方法快速准确、灵敏度高,可适用于蔬菜水果中菊酯类农药残留的快速检测。

加速溶剂萃取/凝胶渗透色谱净化/气相色谱-三重四极杆质谱测定水产品中的持久性有机污染物

建立了一种加速溶剂萃取/凝胶渗透色谱净化/气相色谱三重四极杆质谱同时检测水产品中46种典型持久性有机污染物的方法。水产样品经-105℃、100 mbar条件下的冷冻干燥处理后,加入硅藻土混合碾磨均匀后,经加速溶剂萃取、凝胶渗透色谱净化,使用萘-d、芴-d、蒽-d、■-d作为内标,采用气相色谱三重四极杆质谱的多反应监测模式对水产品中的16种多环芳烃、30种有机氯农药进行定性定量分析。在100℃、1500 psi条件下以二氯甲烷:己烷(1:1,V/V)对46种有机污染物进行萃取,收集凝胶渗透色谱中7.5~16 min馏出液,浓缩定容上机分析。46种持久性有机污染物分离效果良好,相关系数R^2均在0.99以上,低(10μg/kg)、中(50μg/kg)、高(100μg/kg)3个水平的加标回收率均在81.0%~121.0%之间,相对标准偏差(RSD,n=6)在4.1%~11.0%之间,方法检出限为0.0185μg/kg^0.7377μg/kg(干重)。该方法采用加速溶剂萃取仪和凝胶渗透色谱仪进行前处理,可实现前处理无人值守,大大提升检验效率,且方法稳定性好,灵敏度和回收率高,是分析水产品中痕量持久性有机污染物的较好方法。

改进QuEChERS-气相色谱-三重四级杆质谱法测定鸡蛋中七种手性拟除虫菊酯类有机污染物

以改进的Qu ECh ERS(quick,easy,cheap,effective,ruggedandsafe)前处理方法结合气相色谱-三重四极杆质谱(gas chromatography-tandem mass spectrometry,GC-MS/MS)技术,建立了鸡蛋中七种手性拟除虫菊酯类有机污染物的检测和分析方法,为鸡蛋中拟除虫菊酯残留限量的制定提供依据。将鸡蛋样品经80%乙酸乙酯-丙酮提取,乙二胺-N-丙基甲硅烷(PSA)净化,无水硫酸镁脱水,以HP-5MS毛细管柱进行分离,在电子轰击源(EI)和多反应监测模式下进行测定,基质曲线外标法定量。结果表明,该方法能有效的分离7种手性拟除虫菊酯,峰形良好,待测物质在1~200μg/L范围内线性良好,相关系数大于0.99,检出限为0.46~1.59μg/kg,定量限为1.52~5.29μg/kg,加标回收率范围为72.1%~117.5%,相对标准偏差(RSD)为1.6%~15.1%(n=6)。该方法前处理简单易行,便于操作,方法精密度高,适用于鸡蛋中拟除虫菊酯类有机污染物的快速筛查和定量检测。

改进QuEChERS-气相色谱-三重四级杆质谱法测定水果中吗啉脂肪酸盐的残留

该研究建立了水果中吗啉脂肪酸盐果蜡的气相色谱-三重四极杆质谱(gas chromatography-tandem mass spectrometry,GC-MS/MS)分析方法。样品使用改进QuEChERS(quick,easy,cheap,effective,rugged and safe)方法,经1%甲酸-乙腈提取,乙二胺-N-丙基甲硅烷(PSA)和石墨化炭黑吸附剂(GCB)净化,使用5.5 mol/L盐酸和4.3 mol/L亚硝酸钠在冰浴条件下衍生3 h,以HP-FFAP毛细管柱进行分离,在电子轰击源(EI)和多反应监测模式下进行测定,基质曲线外标法定量。结果表明,吗啉脂肪酸盐通过亚硝基化反应可衍生成稳定的亚硝基吗啉(N-nitrosomorpholine,NMOR),目标衍生化合物峰形较好,在1~800μg/L范围内线性良好,相关系数大于0.99,检出限为0.14~1.09μg/kg,定量限为0.47~3.63μg/kg,加标回收率范围为73.6%~118.5%,相对标准偏差(RSD)为3.6%~15.2%(n=6)。该方法准确、高效,在实际样本中检出率较高,适用于水果中吗啉脂肪酸盐果蜡的定性和定量检测。

Decomposition of Mongolian pine litter in the presence of understory species in semi-arid northeast China

The effects of understory plant litter on domi- nant tree litter decomposition are not well documented especially in semi-arid forests. In this study, we used a microcosm experiment to examine the effects of two understory species （Artemisia scoparia and Setaria viridis） litter on the mass loss and N release of Mongolian pine （Pinus sylvestris var. mongolica） litter in Keerqin Sandy Lands, northeast China, and identified the influencing mechanism from the chemical quality of decomposing litter. Four litter combinations were set up： one monocul- ture of Mongolian pine and three mixtures of Mongolian pine and one or two understory species in equal mass proportions of each species. Total C, total N, lignin, cel- lulose and polyphenol concentrations, and mass loss of pine litter were analyzed at days 84 and 182 of incubation.The chemistry of pine litter not only changed with the stages of decomposition, but was also strongly influenced by the presence of understory species during decomposition. Both understory species promoted mass loss of pine litter at 84 days, while only the simultaneous presence of two understory species promoted mass loss of pine litter at 182 days. Mass loss of pine litter was negatively correlated with initial ratios of C/N, lignin/N and polyphenol/N of litter combinations during the entire incubation period; at 182 days it was negatively correlated with polyphenol concentration and ratios of C/N and polyphenol/N of litter combinations at 84 days of incubation. Nitrogen release of pine litter was promoted in the presence of understory species. Nitrogen release at 84 days was negatively correlated with initial N concentration; at 182 days it was negatively correlated with initial polyphenol concentration of litter combinations and positively correlated with lignin concentration of litter com- binations at 84 days of incubation. Our results suggest that the presence ofunderstory species causes substantial changes in chemical components of pine litter that can exert strong influences on subsequent decomposition of pine litter.

Novel p.C620L RET Mutation Detected in a Patient with Medullary Thyroid Carcinoma

A patient with an apparent sporadic medullary thyroid carcinoma was tested for RET germline mutations by Sanger sequencing of RET exons 10, 11, and 13-16. The patient was heterozygous for two known mutations causative of Multiple Endocrine Neoplasia type 2 disorder, and both mutations were within codon 620 of RET exon 10, c.1859G > T (p.C620F) and c.1860C > G (p.C620W). In order to determine if these adjacent mutations were in cis or in trans, an unlabeled probe method and high-resolution melting analysis were utilized. The mutations were confirmed to occur in cis, representing a novel mutation, c.1859_1860delinsTG (p.C620L). Sanger sequencing of parental samples did not identify any changes at codon 620, so the p.C620L mutation is also de novo. The early age of onset for medullary thyroid carcinoma and the presence of lymph node metastasis in this patient suggests individuals with the p.C620L mutation should be treated and screened (for pheochromocytomas and parathyroid hyperplasia) as Multiple Endocrine Neoplasia type 2 patients with other RET codon 620 mutations (American Thyroid Association risk level B).

三江平原沼泽湿地4种优势植物空间格局对不同水位环境的响应

水文过程是沼泽湿地最基本的生态过程,理解物种空间格局形成机制及其种群特征随水位环境变化的规律对于科学指导沼泽湿地植被恢复具有重要意义。本研究分别选择三江平原季节性积水与常年积水沼泽,应用点格局方法中的完全空间随机模型、泊松聚块模型和嵌套双聚块模型分析了毛薹草(Carex lasiocarpa)、漂筏薹草(C.pseudocuraica)、狭叶甜茅(Glyceria spiculosa)、小叶章(Deyeuxia angustifolia)4个主要优势植物种群的空间格局,并测定了不同水位环境条件下的种群密度和个体大小特征。结果表明:在沼泽湿地中,4个优势种群在0-200 cm的尺度范围内都偏离了完全随机模型,表现为集体性聚集分布特征,且聚集距离主要集中在0-50 cm之间。随着水位的升高,毛薹草种群密度、个体生物量、株高和基径都呈显著增大趋势,但其聚集强度变弱;而小叶章种群密度和个体大小则显著降低,其聚集强度增大;漂筏薹草和狭叶甜茅种群密度、个体大小和聚集强度变化并不显著。在季节性积水区,4个物种在小尺度上均偏离了泊松聚块模型,符合嵌套双聚块模型,即在大聚块中分布较高密度的小聚块。但是,在常年积水区,仅毛薹草、漂筏薹草和狭叶甜茅3个物种符合嵌套双聚块模型,而小叶章种群则符合泊松聚块模型,说明在高水位胁迫下小叶章种群空间格局的大聚块中不存在较高密度的小聚块。综上所述,水位环境胁迫主要通过影响繁殖分配、种内竞争、易化作用以及个体大小变异等生物学过程共同决定着三江平原淡水沼泽湿地植物种群的斑块化分布特征,不同零模型可以帮助解释种群空间分布格局的形成机制。

Biomass allocation between leaf and stem regulates community-level plant nutrient resorption efficiency response to nitrogen and phosphorus additions in a temperate wetland of Northeast China

Aims Nutrient resorption is a crucial component of plant nutrient use strategy,yet the controls on the responses of community-level nutrient resorption to altered nutrient availability remain unclear.Here,we addressed two questions:(1)Did leaf and stem nutrient resorption respond consistently to increased nutrient availability?(2)Was community-level plant nutrient resorption response after nutrient enrichment driven by the intraspecific plasticity in plant nutrient resorption or by altered species composition?Methods We investigated the changes in aboveground biomass,and leaf and stem nutrient resorption of individual species after 3-year nitrogen(N)and phosphorus(P)additions,and assessed community-level nutrient resorption response to 3-year nutrient additions in a graminoid-dominated temperate wetland,Northeast China.Important Findings For both leaves and stems,N and P additions did not affect nutrient resorption efficiency,but they decreased respective nutrient resorption proficiency.Similarly,community-level N and P resorption proficiency declined with respective nutrient addition.Community-level N and P resorption efficiency was reduced by N addition primarily due to altered community composition and declined leaf:stem ratio.These results suggest that leaf and stem nutrient resorption processes exhibit consistent responses to increasing nutrient availability in the temperate wetland.These findings highlight the importance of altered species composition and biomass allocation between leaf and stem in driving community-level nutrient resorption response to nutrient enrichment.

Plant phenols contents and their changes with nitrogen availability in peatlands of northeastern China

Aims Climate warming and increasing nitrogen(N)deposition have influenced plant nutrient status and thus plant carbon(C)fixation and vegetation composition in boreal peatlands.Phenols,which are secondary metabolites in plants for defense and adaptation,also play important roles in regulating peatland C dynamics due to their anti-decomposition properties.However,how the phenolic levels of different functional types of plants vary depending on nutrient availability remain unclear in boreal peatlands.Methods Here,we investigated total phenols contents(TPC)and total tannins contents in leaves of 11 plant species in 18 peatlands of the Great Hing’an Mountains area in northeastern China,and examined their variations with leaf N and phosphorus(P)and underlying mechanisms.Important Findings Shrubs had higher TPC than graminoids,indicating less C allocation to defense and less uptake of organic N in faster-growing and nonmycorrhizal graminoids than in slower-growing and mycorrhizal shrubs.For shrubs,leaf TPC decreased with increasing N contents but was not influenced by changing leaf phosphorus(P)contents,which suggested that shrubs would reduce the C investment for defense with increasing N availability.Differently,leaf TPC of graminoids increased with leaf N contents and decreased with leaf P contents.As graminoids are more N-limited and less P-limited,we inferred that graminoids would increase the defensive C investment under increased nutrient availability.We concluded that shrubs would invest more C in growth than in defense with increasing N availability,but it was just opposite for graminoids,which might be an important mechanism to explain the resource competition and encroachment of shrubs in boreal peatlands in the context of climate warming and ever-increasing N deposition.

Effect of shrub encroachment on leaf nutrient resorption in temperate wetlands in the Sanjiang Plain of Northeast China

Background:Nutrient resorption is an important plant nutrient conservation strategy in wetlands.However,how shrub encroachment alters plant nutrient resorption processes is unclear in temperate wetlands.Here,we collected green and senesced leaves of common sedge,grass,and shrub species in wetlands with high(50–65%)and low(20–35%)shrub covers in the Sanjiang Plain of Northeast China,and assessed the impact of shrub encroachment on leaf nitrogen(N)and phosphorus(P)resorption efficiency and proficiency at both plant growth form and community levels.Results:The effects of shrub cover on leaf nutrient resorption efficiency and proficiency were identical among shrubs,grasses,and sedges.Irrespective of plant growth forms,increased shrub cover reduced leaf N resorption efficiency and proficiency,but did not alter leaf P resorption efficiency and proficiency.However,the effect of shrub cover on leaf nutrient resorption efficiency and proficiency differed between plant growth form and community levels.At the community level,leaf N and P resorption efficiency decreased with increasing shrub cover because of increased dominance of shrubs with lower leaf nutrient resorption efficiency over grasses and sedges.Accordingly,community‑level senesced leaf N and P concentrations increased with elevating shrub cover,showing a decline in leaf N and P resorption proficiency.Moreover,the significant relationships between leaf nutrient resorption efficiency and proficiency indicate that shrub encroachment increased senesced leaf nutrient concentrations by decreasing nutrient resorption efficiency.Conclusions:These observations suggest that shrub encroachment reduces community‑level leaf nutrient resorp‑tion efficiency and proficiency and highlight that the effect of altered plant composition on leaf nutrient resorption should be assessed at the community level in temperate wetlands.