Carbon exchange between ecosystems and atmosphere in the Czech Republic is affected by climate factors

By comparing five ecosystem types in the Czech Republic over several years, we recorded the highest carbon sequestration potential in an evergreen Norway spruce forest (100%) and an agroecosystem (65%), followed by European beech forest (25%) and a wetland ecosystem (20%). Because of a massive ecosystem respiration, the final carbon gain of the grassland was negative. Climate was shown to be an important factor of carbon uptake by ecosystems: by varying the growing season length (a 22-d longer season in 2005 than in 2007 increased carbon sink by 13%) or by the effect of short- term synoptic situations (e.g. summer hot and dry days reduced net carbon storage by 58% relative to hot and wet days). Carbon uptake is strongly affected by the ontogeny and a production strategy which is demonstrated by the comparison of seasonal course of carbon uptake between coniferous (Norway spruce) and deciduous (European beech) stands.     

Blue carbon in human-dominated estuarine and shallow coastal systems

Estuarine and shallow coastal systems (ESCS) are recognized as not only significant organic carbon reservoirs but also emitters of CO₂ to the atmosphere through air–sea CO₂ gas exchange, thus posing a dilemma on ESCS’s role in climate change mitigation measures. However, some studies have shown that coastal waters take up atmospheric CO₂ (C_atm), although the magnitude and determinants remain unclear. We argue that the phenomenon of net uptake of C_atm by ESCS is not unusual under a given set of terrestrial inputs and geophysical conditions. We assessed the key properties of systems that show the net C_atm uptake and found that they are often characteristic of human-dominated systems: (1) input of high terrestrial nutrients, (2) input of treated wastewater in which labile carbon is highly removed, and (3) presence of hypoxia. We propose that human-dominated ESCS are worthy of investigation as a contributor to climate change mitigation.     

A Budget Model to Scale Nutrient Biogeochemical Cycles in Two Semienclosed Gulfs

The nutrient dynamics of the Strymonikos and Ierissos Gulfs, two semienclosed coastal water bodies, are studied using a simple steady-state budget model, according to the Land–Ocean Interaction in the Coastal Zone modeling guidelines. Strymon river plume dynamics prevailed in the area of the Inner and Outer Srymonikos Gulfs, comprising two layers, while the Ierissos Gulf was defined as a one-box system. Seasonal and mean annual model input data for river discharge, precipitation, evaporation, and concentrations of salt, phosphorus, and nitrogen were obtained during four field campaigns. Results from the nitrogen and phosphorus cycling revealed the importance of river discharge in the horizontal and vertical transport of these substances within the system. Furthermore, it occurred that the major biogeochemical transformation of nitrogen and phosphorus takes place in the immediate nearshore zone (Inner Strymonikos Gulf), while the outer system sustains its nutrient dependence on oceanic exchanges. Therefore, under the summer low flow conditions, the river-influenced inner system acts as a net source of nitrogen and phosphorus, while under increased Strymon River discharge, phosphorus is transferred to the biological material (and the sediments), and the system moves to an autotrophic state. The outer system showed an opposite behavior being autotrophic throughout the year and heterotrophic in February. The Ierissos Gulf, a system not directly influenced by significant river discharge, experienced a seasonally independent behavior with net heterotrophic and denitrification processes prevailing. Model scenarios demonstrated that phosphate concentration increases, even under low river flow conditions and stimulates primary production in excess of respiration, resulting in nitrogen fixation prevalence in the Inner Strymonikos Gulf.     

黄河三角洲翅碱篷湿地硫化氢和羰基硫排放动态研究

利用静态箱/气相色谱法,观测了生长季(5~10月)黄河三角洲翅碱篷湿地H2S和COS的释放动态.结果表明,H2S、COS的排放通量具有明显的季节和日变化规律,在生长季,黄河三角洲翅碱篷湿地是H2S和COS的释放源,其中H2S的平均释放通量为4.97μg·(m2·h)-1,COS的平均释放通量为0.92μg·(m2·h)-1.在探讨的环境因子中,不同环境因子对翅碱篷湿地H2S和COS释放通量的影响不同,其中土壤SO2-4含量是影响H2S释放通量的主要因素,土壤含水量是影响COS释放通量的主要因素.含硫气体的排放可能还受到其它因素如植物、潮汐状况等多种因素的影响.     

成都平原不同类型沟渠CO2、CH4和N2O排放通量特征及其影响因素

为研究不同类型沟渠CH_4、CO_2和N_2O排放通量特征及其影响因素,于2014年3月~2015年2月,以每月一次的频率,采用静态浮箱法对成都平原的农业沟渠、农业生活复合沟渠、生活沟渠的CH_4、CO_2和N_2O排放通量进行监测.结果表明:(1)受人为活动的影响,研究区域中3种类型的沟渠CO_2、CH_4和N_2O排放通量较大,变化范围分别为-2.26~1 504.40mg·(m~2·h)~(-1)、0.69~40.00 mg·(m~2·h)~(-1)、-2.27~70.35μg·(m~2·h)~(-1),且均表现出夏季高,冬季低的特征.(2)农业生活复合沟渠CO_2排放通量显著高于农业沟渠和生活沟渠(P0.05),生活沟渠CH_4和N_2O排放通量显著高于农业生活复合沟渠和农业沟渠(P0.05).(3)水温和降雨量是影响CO_2、CH_4和N_2O排放通量的主要环境因子,溶解氧(dissolved oxgen,DO)和全氮(total nitrogen,TN)是影响CO_2和N_2O排放通量的主要水质参数;铵态氮(ammonium nitrogen,NH_4~+-N)与DO是影响CH_4排放通量的主要水质参数.     

模拟氮沉降对闽江口淡水感潮沼泽湿地CO2、CH4排放通量的短期影响

为了评价氮沉降对我国亚热带河口区淡水感潮沼泽湿地CO_2、CH_4排放通量的影响,在福建闽江口道庆洲淡水感潮短叶茳芏沼泽湿地,设置对照CK[0 g·(m~2·a)~(-1)]及3个梯度的氮沉降处理:N1[24 g·(m~2·a)~(-1)]、N2[48 g·(m~2·a)~(-1)]和N3[96 g·(m~2·a)~(-1)],采用静态箱-气相色谱法测定短叶茳芏湿地CO_2、CH_4排放通量,并同步观测相关环境因子.结果表明,(1)与对照相比,N1处理CO_2排放通量增加20.30%,N2处理CO_2排放通量减少10.05%,N3处理CO_2排放通量增加4.06%,除了12月的N2、N3处理CO_2排放通量与对照间有显著差异外(P0.05),其它时间各处理间CO_2排放通量差异性不显著(P0.05).(2)与对照相比,N1处理CH_4排放通量提高64.51%,N2处理CH_4排放通量提高30.23%,N3处理CH_4排放通量提高80.57%,但是各处理间CH_4排放通量的差异性未达到显著水平(P0.05).(3)CO_2、CH_4排放通量与土壤温度具有显著的正线性相关关系(P0.05),与土壤EC、土壤p H的相关性不显著(P0.05).     

Dynamic pursuing ecological model concerning the nitrogen cycle in the environment of Chinese mainland

The paper gives a special dynamic pursuing ecological model on the bio-geochemical cycle of nitrogen in the whole range 9.6 million square kilometers of Chinese mainland, basing on the reservoir-content and flux-rate of nitrogen and among the four spheres: atmosphere, pedosphere, biosphere, and hydrosphere, and the law of bio-geochemical cycle of nitrogen, the model predicted the size of reservoir capacities and fluxes of nitrogen in each sphere. Through tested and verified, the model was proven reasonable and reliable.     

太子河流域莠去津的空间分布及风险评价

应用气相色谱-质谱联用仪(gas chromatograph-mass spectrometer,GC-MS),分析了莠去津(atrazine,AT)在太子河流域地表水、悬浮物和地下水中的含量水平,以及AT在该流域水体环境中的分布特征与环境行为,并对地表水中的AT污染程度进行了初步评价.结果表明,太子河流域地表水中ρ(AT)为0~734.0 ng·L-1,悬浮物中ω(AT)为0~1 496.6 ng·g-1,地下水中ρ(AT)为30.0~245.0 ng·L-1,其算术平均值分别为335.3 ng·L-1、382.9 ng·L-1和104.4 ng·L-1.AT在太子河流域地表水中水相-悬浮物相的有机碳标准分配系数(lg koc)介于3.50~4.14,表明悬浮物的吸附是水体中AT迁移的一个重要途径.AT在太子河流域地表水体中(水相和悬浮物相)的通量介于1.5~184.7 mg·s-1之间,最高值出现在中游地区.风险评价结果显示,地表水中AT的生态风险很小,95%以上的物种能够得以保护,但太子河流域地表水中AT的残留水平可能具有一定的潜在危害.     

滇池沉积物有机质沉积特征与来源解析

以滇池湖泊东南部和东部沉积柱为研究对象,对沉积柱中不同层的沉积物样品使用210Pb定年,分析不同年代沉积物中总有机碳(TOC)和正构烷烃的含量及沉积通量,利用正构烷烃相关指标示踪有机质来源.结果表明:1两采样点沉积物中TOC含量和沉积通量随时间增长均表现为总体上升的变化趋势;正构烷烃沉积通量随沉积年代的变化,分为上升期、下降期与再次上升期这3个阶段.2正构烷烃与TOC沉积通量均增大时,两者来源具有一致性,均来自于湖泊内部和入湖河流携带的泥沙物质之中;20世纪80年代至20世纪末,正构烷烃沉积通量在减小,TOC沉积通量在增大,说明该时期两者来源存在较大差异,湖泊内的细菌、藻类对正构烷烃的贡献较大,而TOC受湖泊内部与入湖泥沙的影响较大.3两采样点检测到的正构烷烃碳数范围为C12~C35,由正构烷烃基本特征与源解析指标分析得出:挺水植物对滇池湖泊沉积物中有机质来源贡献较大,浅层深度,细菌和藻类的贡献突出.     

不同耕作方式下土壤水分状况对土壤呼吸的初期影响

以2001年在东北典型黑土上进行的保护性耕作长期定位试验下免耕、垄作及常规耕作土壤进行了室内培养实验,按照田间持水量(water-holding capacity,WHC)的30%、60%、90%、120%、150%、180%、210%、240%、270%设定了9个水分梯度,并分别对其二氧化碳(CO_2)排放量进行了22 d的短期观测,以研究不同耕作方式下土壤水分状况对土壤呼吸的初期影响.结果表明:1干土条件下在加水培养初期,3种耕作方式均产生了明显的激发效应,并且土壤呼吸速率与土壤含水量间存在正相关关系.2除干旱(30%WHC)及淹水(240%WHC、270%WHC)条件下,3种耕作方式CO_2排放通量分别为免耕垄作常规耕作.3对不同耕作方式下土壤水分状况及CO_2排放通量进行了方程拟合,在30%~270%WHC条件下,免耕的CO_2排放通量与水分状况拟合为二次回归方程,而垄作与常规耕作则是线性回归方程.在30%~210%WHC条件下,免耕与垄作下土壤CO_2排放通量与水分状况均可拟合为较好的对数方程,可决系数R~2分别为0.966、0.956.