Northeast Institute of Geography and Agroecology, Chinese Academy Of Sciences
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Anthropogenic, detritic and atmospheric soil-derived sources of lead in an alpine poor fen in northeast China
No full textOmbrotrophic bogs are faithful archive of atmospheric metal deposition, but the potential for fens to reconstruct environmental change is often underestimated. In this study, some new data on the Pb depositional history in northeast China were provided using two ~(210)Pb-dated peat sequences from a poor fen in the Fenghuang Mountain of Heilongjiang province. Anthropogenic, detritic and atmospheric soil sources were discriminated using a two-step sequential digestion (weak acid leaching to liberate mobile Pb which is often regarded as anthropogenic Pb, especially for recent samples) and a ratio of unsupported ~(210)Pb and supported ~(210)Pb with the logic of that the 214Pb mainly represents the residual detritus (constant throughout the core) and the unsupported ~(210)Pb arises from atmospheric fallout. A higher ~(210)Pb/214Pb suggests more contributions from atmospheric deposition to the Pb content in the peat, and a ratio of 10 was defined to indicate the boundary between detritic input and atmospheric deposition. The detritic Pb was estimated to be 10–13 mg·kg~(–1), the anthropogenic Pb ranged from 10–80 mg·kg~(–1), and the atmospheric soil-derived Pb ranged from < 5 mg·kg~(–1) to 30 mg·kg~(–1). The history of anthropogenic Pb pollution over the last 150 years was reconstructed, and the calculated Pb deposition rate (AR Pb) ranged from 5 to 56 mg·m-2·yr-1. Using Ti as a reliable reference, the enrichment factor of Pb (EF Pb) relative to the upper continental crust was calculated. Both AR Pb and EF Pb increased with time, especially after the foundation of the People's Republic of China. This is consistent with increasing industrialization and coal burning in the last 60 years in northeast China. The present record of anthropogenic Pb deposition was consistent with the previous reports and an increasing trend of environmental pollution due to anthropogenic activities, in contrasts to Europe and North America which have experienced a major environmental cleanup. For the first time, this work estimates atmospheric Pb deposition via a minerotrophic peat core in China. This will enhance the use of peat archives for studies of environmental change
Diurnal Variation of Soil CO_2 Efflux and Its Optimal Measuring Time-window of Temperate Meadow Steppes in Western Songnen Plain, China
No full textIn order to study the diurnal variation of soil CO_2 efflux from temperate meadow steppes in Northeast China, and determine the best time for observation, a field experiment was conducted with a LI-6400 soil CO_2 flux system under five typical plant communities (Suaeda glauca (Sg), Chloris virgata (Cv), Puccinellia distans (Pd), Leymus chinensis (Lc) and Phragmites australis (Pa)) and an alkali-spot land (As) at the meadow steppe of western Songnen Plain. The results showed that the diurnal variation of soil CO_2 efflux exhibited a single peak curve in the growing season. Diurnal maximum soil respiration (Rs) often appeared between 11:00 and 13:00, while the minimum occurred at 21:00-23:00 or before dawn. Air temperature near the soil surface (Ta) and soil temperature at 10 cm depth (T_(10)) exerted dominant control on the diurnal variations of soil respiration. The time-windows 7:00-9:00 could be used as the optimal measuring time to represent the daily mean soil CO_2 efflux at the Cv, Pd, Lc and Pa sites. The daily mean soil CO_2 efflux was close to the soil CO_2 efflux from 15:00 to 17:00 and the mean of 2 individual soil CO_2 efflux from 15:00 to 19:00 at the As and Sg sites, respectively. During nocturnal hours, negative soil CO_2 fluxes (CO_2 downwards into the soil) were frequently observed at the As and Sg sites, the magnitude of the negative CO_2 fluxes were 0.10-1.55 μmol/(m~2?s) and 0.10-0.69 μmol/(m~2?s) at the two sites. The results implied that alkaline soils could absorb CO_2 under natural condition, which might have significant implications to the global carbon budget accounting
松花江流域季节性气象干旱特征及风险区划研究
No full text利用松花江流域67个代表性气象站1960~2009年气象观测资料,采用标准化降水指数(SPI)为评价指标,计算松花江流域50 a中各季干旱指数,在此基础上分析了流域季节性气象干旱演变特征及规律,研究发现,松花江流域气象干旱呈现出明显的空间分带性和季节分带性。从地域变化来看,流域干旱区主要分布在东北、西南部;从季度变化来看,春旱和夏旱是流域气象干旱的主要类型,夏季干旱最严重,春季次之。建立评价指标体系实现了基于GIS技术的气象干旱风险区划,针对不同风险区提出相应的抗旱措施,为流域有效应对干旱灾害提供依据
化肥配施生物炭对稻田田面水氮磷流失风险影响
No full text在控制外源氮输入相同的前提下,通过大田试验研究生物炭部分替代化肥作为底肥,不同生物炭施用量(5、10、20 t·hm~(-2))对水稻生长期内稻田田面水氮磷迁移转化特征的影响。研究结果表明:各处理的田面水总氮、硝氮、铵氮浓度在施肥后第3 d达到最高,然后迅速下降,并逐渐稳定;田面水总磷浓度在施肥后2~4 d内增幅较小,而后迅速下降至稳定,施加生物炭对田面水总磷的影响不大;可溶性磷浓度在施肥后2~4 d内处于平稳下降的状态,之后迅速下降至稳定。稻田施肥后10 d内是控制氮磷流失的最佳时段。采用生物炭代替部分化肥的施肥方式,在一定范围内能降低稻田田面水的氮磷浓度,稻田退水氮、磷的输出负荷分别减少了39%~50%和38%~50%,显著提高了水稻生态效益。通过综合效益评估可知,施加5 t生物炭代替化肥是综合效益最高的施肥方法,该施肥方式下氮、磷的年输出负荷分别为16.83、1.89 kg·hm~(-2)
湿地中黑碳的研究进展
No full text黑碳是生物质或化石燃料不完全燃烧产生的含碳物质。湿地,特别是泥炭地,是忠实记录和反映古环境信息的理想地质档案之一,研究湿地中的黑碳,对探讨湿地中稳定性碳的储量、长时间尺度的火活动及其与气候和植物变化的关系具有重要意义。综述了湿地中黑碳的来源及其适用的测量方法;与其它沉积环境相比,湿地环境中黑碳含量特征及其与有机质之间的关系;总结了湿地中黑碳的储量及其影响因素;分析了其与火活动、气候和植物变化的关系;结合当前国内外研究现状,展望了未来湿地中黑碳研究的方向
查干湖和新立城水库秋季水体悬浮颗粒物和CDOM吸收特性
No full text分别于2012年9月对不同盐度水体的查干湖和新立城水进行水体野外采样和室内实验分析，通过测定颗粒物、 CDOM等光学活性物质的吸收系数来对比分析两种水体的光学活性物质的吸收特性、 来源及其在400~700 nm范围内对总吸收系数的贡献. 结果表明，综合营养状态评价指数显示秋季查干湖、 新立城水库水体属于中等富营养化，总悬浮颗粒物的吸收光谱表现均与色素类颗粒物吸收光谱相似. 对于盐度较大的查干湖水体(EC=988.87 μS·cm~(-1))，非藻类颗粒物占主导地位，各组分贡献率为非藻类颗粒物>色素颗粒物>CDOM； 而盐度较低的新立城水库水体(EC=311.67 μS·cm~(-1)),色素颗粒物贡献率略大于非藻类颗粒物贡献，各组分贡献率依次为：色素颗粒物>非藻类颗粒物>CDOM. 查干湖总悬浮颗粒物吸收系数a_p(440)、 a_p(675)和非藻类颗粒物吸收系数a_d(440)分别与TSM(总悬浮颗粒物)、 ISM(无机悬浮颗粒物)和OSM(有机悬浮颗粒物)、 Chl-a(叶绿素a)相关性均较好，相关系数在0.55以上； 新立城水库a_p(440)、 a_p(675)与Chl-a相关性较好(0.77和0.85, P<0.05)，a_d(440)与ISM具有相关性(0.74, P<0.01)，与OSM表现为负相关(-0.63, P<0.05). 查干湖CDOM吸收系数a_g(440)仅与OSM表现为负相关性(-0.54, P<0.05)，而新立城水库a_g(440)与其他参数均无相关性. 通过对CDOM吸收曲线在250~400 nm的拟合所得到的S_g以及相对分子量M_r发现，查干湖的S_g [(0.021±0.001) m~(-1)]大于新立城的S_g[(0.017 6±0.001) m~(-1)]，而CDOM的相对分子量M_r值分别为11.44±2.00(7.5~15.09)、 7.53±0.79(6.17~8.89)，查干湖M_r值高于新立城水库水体，表明查干湖CDOM组成较新立城水体中CDOM的分子量小，组成更趋向于小分子. 查干湖受风速和湖岸坍塌的影响产生矿物悬浮、 沉积微粒，水体颗粒物以非藻类为主，部分来自于浮游植物降解产物； 新立城水库水体不仅有径流携带的陆源性无机物的输入，同时水体浮游植物生长减弱且微生物分解活动加强，降解有机颗粒物与非藻类吸收系数呈现负相关
基于RS和GIS的农田防护林对作物产量影响的评价方法
No full text在区域尺度评价农田防护林对作物产量的影响对于农田防护林建设和经营管理具有重要意义。该文提出了一种基于遥感(remote sensing,RS)和地理信息系统(geographic information system,GIS)技术的农田防护林对作物产量影响的评价方法。首先利用多时相遥感影像识别农田防护林的经营阶段和和生长状态,建立农田防护林防护效应的综合判定模式;其次采用机制法,通过光、温、水、土逐级衰减,计算作物生产潜力,并基于遥感影像和光能利用率模型估算作物单产;最后构建农田防护林对作物产量影响的评价方法体系。基于该方法,在吉林省长春市北部的农田防护林重点建设区选择样区,评价了该区2009年农田防护林对玉米产量的影响。结果表明,农田防护林在一定程度上将会促进玉米增产。尤其在自然条件较差的低产区,农田防护林的增产作用更加显著,增产率达到8.85%;而在高产区,增产率约为2.4%,但是由于胁地效应的影响,在部分地区可能造成减产。因此,在农田防护林的规划建设中,应根据不同的立地条件,因地制宜,在占地面积最小的情况下,达到稳产增产的作用,实现农田防护林的最大防护效应。该研究丰富了在区域尺度研究农田防护林防护效应的技术方法,可以更加科学合理的评价区域尺度上农田防护林的增产效益,并为农田防护林的经营管理提供科学依据
长期施肥对东北黑土不同活性有机碳库的影响
No full text试验采用团聚体分组和闭蓄态微团聚体分离技术,将土壤有机碳分为总粗颗粒有机质(活性碳库)、总细颗粒有机质(慢性碳库)和总粉粘粒(惰性碳库)等组分,研究长期施肥对东北黑土不同活性有机碳库的影响。结果显示,与不施肥相比,19年连续单独施用化肥没有影响土壤有机碳含量和土壤总体的团聚化效果;化肥和有机肥配施则显著提高了土壤团聚化程度,增加了有机碳含量和储量,增幅分别为36%和18%。粉粘粒结合有机碳占土壤总有机碳的50%~70%,其作为惰性碳库是黑土有机碳的重要组成部分。与无肥相比,单施化肥没有影响不同活性有机碳库含量及土壤有机碳库的稳定性;有机无机配施没有改变土壤中粉粘粒结合有机碳含量,但显著提高了总粗颗粒有机质和总细颗粒有机质中有机碳含量,降低了土壤有机碳库的稳定性。有机无机配施土壤中活性有机碳的增加,一方面有利于提高农田黑土生产力,另一方面又会加剧温室效应。因此,在保证作物产量的同时,尽量减少CO_2排放,确定适宜的有机肥施用量,是解决黑土区农业生产和环境保护矛盾的重要途径
Characterization of root-associated bacterial community structures in soybean and corn using locked nucleic acid (LNA) oligonucleotide-PCR clamping and 454 pyrosequencing
No full textThe community structure and diversity of root-associated bacteria have been tentatively investigated using polymerase chain reaction (PCR) amplification methods in several studies. However, the homology between small submit ribosomal (SSU) rRNA genes of plant plastids and mitochondria and that of bacteria have hindered in these studies. To address this issue, in this paper, we adopted the methods of locked nucleic acid (LNA) oligonucleotide-PCR clamping with 454 pyrosequencing to analysis the root -associated bacterial community compositions in soybean and corn. Results showed that plant chloroplast and mitochondria genes were effectively inhibited from PCR amplification in the root samples with LNA oligonucleotides (LNA (+)), and PCR amplicons with LNA (+) had higher bacterial operational taxonomic unit (OTU) numbers and ACE, Chao1, and Shannon indices, as well as a lower Simpson index than the corresponding samples without LNA oligonucleotides (LNA (-)). Those findings suggested that the methods of this study provide a much more detail description of root -associated bacterial communities. In the soybean LNA (+) sample, Pseudomonas, Bradyrhizobium and Flavobacterium were the three most abundant genera, whereas the top two predominant genera in corn LNA (+) samples were Streptomyces and Niastella. The presence and absence of major genera varied between soybean and corn, suggesting the root -associated bacterial communities differed between two crops. The rare phylotypes and uncultured root -associated bacterial members detected in this study inferred that the root -associated bacterial communities are highly complex and information on their taxonomic affiliates potentially gives the clues for selecting the optimal medium and method to isolate the novel bacteria for further functional analysis