中街山列岛海域食物网结构初步研究及主要消费者潜在碳源分析

为了解中街山列岛的食物网结构特征,本研究于2020年7月在中街山列岛海域采集鱼类、虾蟹类、头足类、贝螺类和浮游动物等消费者样本,利用碳、氮稳定同位素技术,分析大型海藻、浮游植物、悬浮颗粒有机物（POM）和沉积物有机物（SOM）4种潜在碳源对消费者的贡献率以及中街山列岛海域的食物网结构和营养关系。结果表明：（1）碳源的δ¹³C值范围在−22.93‰～−9.73‰之间,δ¹⁵N值范围在1.72‰～7.68‰之间,消费者的δ¹³C值范围在−21.95‰～−12.55‰之间,δ¹⁵N值范围在4.13‰～12.92‰之间,不同碳源及不同消费者类群之间的碳、氮稳定同位素均有显著性差异（p<0.01）;（2）应用SIBER模型计算中街山列岛海域的营养结构指标,与其他海域的研究结果对比发现,该海域生态系统的食源多样性更加丰富,营养级长度和生态位总空间较高;（3）应用SIAR模型计算碳源贡献率,结果表明浮游植物和POM是该海域的重要碳源,平均贡献率为29.63%和28.72%;浮游植物对浮游动物的贡献率最大为80.58%,POM对鱼类的贡献率最大为79.74%;SOM对虾蟹类的贡献率最大为49.94%;大型海藻对消费者的碳源贡献率最低,平均为18.37%;（4）以浮游动物为基线生物计算得知主要消费者的平均营养级在1.58～3.63之间,营养层次为3级,各种类平均营养级由大到小依次为头足类（3.09）、鱼类（3.00）、虾蟹类（2.70）、贝螺类（1.82）,中街山列岛海域消费者以低、中级肉食性动物为主,杂食性和高级肉食性动物较少。本研究初步探明了中街山列岛生态系统食物网,为了解该生态系统营养结构奠定了基础,也为今后进一步研究该海域的生态营养动力学提供理论参考。     

内蒙古岱海水体营养状况分析

岱海是我国半干旱区的一个典型内陆湖。近年来,由于受到流域人类活动的强烈干预,湖泊水位持续下降,湖面不断萎缩。与此同时,湖泊水质也呈现出明显的恶化趋势,2004年水质监测结果显示,湖水中TN、TP和CODMn均出现超标,全湖水质达到劣Ⅴ类。采用综合营养状态指数法进行评价,岱海水体已处于中度富营养化水平,但受湖周生产布局的影响,营养状况空间分布有所差异,自湖西向湖东,营养状态指数逐渐减小,富营养化程度也相应降低。在时间变化上,岱海已由1996年的中营养化过渡到2004年的中度富营养化,上升了两个营养级别。引起岱海水质恶化的原因主要是农田地表径流及城镇所产生的生活污水,另外,湖泊的不断萎缩也是一个不容忽视的影响因素。为防止岱海水环境继续恶化,根据流域特点提出了一些具体的防治对策和建议。     

Land cover effects on soil infiltration capacity measured using plot scale rainfall simulation in steep tropical lowlands of Central Panama

Understanding land use/land cover (LULC) effects on tropical soil infiltration is crucial for maximizing watershed scale hydro-ecosystem services and informing land managers. This paper reports results from a multiyear investigation of LULC effects on soil bulk infiltration in steep, humid tropical, and lowland catchments. A rainfall simulator applied water at measured rates on 2 × 6 m plots producing infiltration through structured, granulated, and macroporous Ferralsols in Panama's central lowlands. Time-lapse electrical resistivity tomography (ERT) helped to visualize infiltration depth and bulk velocity. A space-for-time substitution methodology allowed a land-use history investigation by considering the following: (a) a continuously heavy-grazed cattle pasture, (b) a rotationally grazed traditional cattle pasture, (c) a 4-year-old (y.o.) silvopastoral system with nonnative improved pasture grasses and managed intensive rotational grazing, (d) a 7 y.o. teak (Tectona grandis) plantation, (e) an approximately 10 y.o. secondary succession forest, (f) a 12 y.o. coffee plantation (Coffea canephora), (g) an approximately 30 y.o. secondary succession forest, and (h) a >100 y.o. secondary succession forest. Within a land cover, unique plot sites totalled two at (a), (c), (d), (e), and (g); three at (b); and one at (f) and (h). Our observations confirmed measured infiltration scale dependency by comparing our 12 m² plot-scale measurements against 8.9 cm diameter core-scale measurements collected by others from nearby sites. Preferential flow pathways (PFPs) significantly increased soil infiltration capacity, particularly in forests greater than or equal to 10 y.o. Time-lapse ERT observations revealed shallower rapid bulk infiltration and increased rapid lateral subsurface flow in pasture land covers when compared with forest land covers and highlighted how much subsurface flow pathways can vary within the Ferralsol soil class. Results suggest that LULC effects on PFPs are the dominant mechanism by which LULC affects throughfall partitioning, runoff generation, and flow pathways.     

Response time and water origin in a steep nested catchment in the Italian Dolomites

In this study, we investigate the surface flow time of rise in response to rainfall and snowmelt events at different spatial scales and the main sources originating channel runoff and spring water in a steep nested headwater catchment (Rio Vauz, Italian Dolomites), characterized by a marked elevation gradient. We monitored precipitation at different elevations and measured water stage/streamflow at the outlet of two rocky subcatchments of the same size, representative of the upper part of the catchment dominated by outcropping bedrock, at the outlet of a soil‐mantled and vegetated subcatchment of similar size but different morphology, and at the outlet of the main catchment. Hydrometric data are coupled with stable isotopes and electrical conductivity sampled from different water sources during five years, and used as tracers in end‐member mixing analysis, application of two component mixing models and analysis of the slope of the dual‐isotope regression line. Results reveal that times of rise are slightly shorter for the two rocky subcatchments, particularly for snowmelt and mixed rainfall/snowmelt events, compared to the soil‐mantled catchment and the entire Rio Vauz Catchment. The highly‐variable tracer signature of the different water sources reflects the geomorphological and geological complexity of the study area. The principal end‐members for channel runoff and spring water are identified in rainfall and snowmelt, which are the dominant water sources in the rocky upper part of the study catchment, and soil water and shallow groundwater, which play a relevant role in originating baseflow and spring water in the soil‐mantled and vegetated lower part of the catchment. Particularly, snowmelt contributes up to 64 ± 8% to spring water in the concave upper parts of the catchment and up to 62 ± 11% to channel runoff in the lower part of the catchment. These results offer new experimental evidences on how Dolomitic catchments capture and store rain water and meltwater, releasing it through a complex network of surface and subsurface flow pathways, and allow for the construction of a preliminary conceptual model on water transmission in snowmelt‐dominated catchments featuring marked elevation gradients.     

The vulnerabilities of agricultural land and food production to future water scarcity

Rapidly increasing populations coupled with increased food demand requires either an expansion of agricultural land or sufficient production gains from current resources. However, in a changing world, reduced water availability might undermine improvements in crop and grass productivity and may disproportionately affect different parts of the world. Using multi-model studies, the potential trends, risks and uncertainties to land use and land availability that may arise from reductions in water availability are examined here. In addition, the impacts of different policy interventions on pressures from emerging risks are examined.Results indicate that globally, approximately 11% and 10% of current crop- and grass-lands could be vulnerable to reduction in water availability and may lose some productive capacity, with Africa and the Middle East, China, Europe and Asia particularly at risk. While uncertainties remain, reduction in agricultural land area associated with dietary changes (reduction of food waste and decreased meat consumption) offers the greatest buffer against land loss and food insecurity.     

基于碳氮稳定同位素技术的小清河口邻近海域底栖食物网结构研究

为了掌握小清河口邻近海域底栖食物网结构特征,于2020年10月在小清河口邻近海域采集沉积物有机质、悬浮颗粒有机物、浮游动物和浮游植物4种潜在食源及35种生物样本,应用碳氮稳定同位素技术以及贝叶斯混合模型(MixSIAR)分析了小清河口邻近海域底栖食物网结构和营养关系.结果显示,潜在食源的δ13C值范围为-25.56‰～...     

范各庄矿12煤底板突水过程模拟分析

以范各庄煤矿水文地质条件为基础,建立了承压水上采煤的岩体水力学模型,应用岩石破裂过程渗流-应力耦合分析系统(RFPA^2D-Flow)模拟分析了范各庄矿12煤层底板开采扰动下,裂隙形成、扩展到突水通道最终贯通形成突水的全过程。通过对损伤区分布、应力场和渗流场的演化分析,揭示了开采扰动及水压驱动下完整泥岩底板由隔水岩层到突水通道的演化过程,对突水通道进行了模拟定位,并对不同水压条件下含水砂岩层对底板突水的影响进行了分析。结果表明：12煤底板突水问题取决于含水砂岩中的水压力,在假设隔水层厚度不变时,水压力与突水系数呈正相关关系,随着水压的增大突水越易发生。该研究为12煤底板突水预测与防治提供了理论依据。     

塔里木盆地轮南低凸起断裂系统与复式油气聚集

塔里木盆地轮南低凸起复式油气聚集区的提出对高效指导轮南地区的油气勘探起了促进作用。基于区域石油地质研究成果,充分利用成像测井、高分辨三维地震断裂精细描述和有机地球化学等新技术新方法,本文系统研究了轮南低凸起复式油气聚集成藏的关键地质条件,全面刻画了轮南断裂系统的复杂特征,明确了轮南多含油层系具有相同的寒武系海相烃源,证实了在多期次成藏过程中,断裂系统既是早期成藏的油气充注通道,又是晚期调整气侵的输导体系。对轮南海相碳酸盐岩大型油气田的成藏,断裂系统既是有效的储集空间,又是储集性能改善和连通性增强的重要条件,提出复杂断裂系统多期活动下油气渐进幕式成藏和跨越动态成藏模式。从前提(古隆起)、基础(多套储盖组合)和关键(断裂系统)3方面探讨了复式油气聚集成藏的机理,并指出轮古东走滑断裂带是近期扩大轮南复式油气聚集区规模、实施天然气勘探的现实领域。     

基于渔获量平均营养级的东印度洋渔业资源可持续利用评价

渔业资源可持续利用是渔业经济可持续发展的基础。本文根据联合国粮农组织提供的1950−2018年东印度洋渔业生产统计数据,结合Fishbase提供的相关鱼种的营养级,探讨了69年间东印度洋渔获量平均营养级(MTL)以及营养级平衡指数的长期变化趋势,以此来判定其渔业资源可持续利用状况。研究认为,1950−2018年东印度洋渔获量呈现稳步增长趋势,其中云鲥(Tenualosa ilisha)、鲱鱼(Clupea pallasi)、印度鲭(Rastrelliger kanagurta)为重要渔获种类,其累计年产量占总产量的比重均在10%以上。MTL变动大致可分3个阶段：1950−1974年渔获MTL总体处在高位,其值范围为3.39～3.71,平均值为3.60±0.07,期间年渔获量呈现稳定的增长趋势,平均年增长率为6.4%;1975−1999年渔获MTL呈现波动,其值范围为3.21～3.51,平均值为3.35±0.08,期间年渔获量呈现稳定的小幅度增长趋势,平均年增长率为4.8%;2000−2018年渔获MTL年间波动较小,其值为3.31～3.43,平均值为3.38±0.03,期间年渔获量呈现缓慢稳定的增长趋势,平均年增长率为1.6%。3个阶段的平均营养级平衡指数分别为0.59±0.22、0.94±0.14、1.25±0.04,其值呈现稳定的增长趋势且年间变化幅度越来越小,说明其群落结构越来越趋稳定。渔业资源的开发利用程度增加,而MTL下降程度较小,营养级平衡指数呈现上升趋势,说明渔获量的增加能够弥补MTL的下降;且仅统计营养级大于3.25的种类时,1950−1974年、1975−1999年、2000−2018年3个阶段的MTL平均值分别为4.16±0.04、4.18±0.04、4.19±0.03,呈现小幅稳定增长的趋势,表明高营养级种群渔业资源未受到破坏。研究认为,东印度洋海洋生态系统稳定,高营养级种群渔业资源处于未充分开发状态。     

中肋骨条藻-裸甲藻-双毛纺锤水蚤营养传递的级联效应

中型浮游动物因摄食微型浮游动物,释放了微型浮游动物对浮游植物的摄食压力,这种营养级联效应会增加浮游植物丰度和降低中型浮游动物对浮游植物的摄食率,从而弱化浮游生物网营养传递过程中的下行控制作用。本研究在实验室模拟了食物链中肋骨条藻-裸甲藻-双毛纺锤水蚤的营养传递过程,发现在中肋骨条藻低生物量时,双毛纺锤水蚤偏好于选择摄食裸甲藻;高生物量时,双毛纺锤水蚤偏好选择摄食中肋骨条藻。营养传递过程中存在正的级联效应(0.018～0.12 d^–1),级联效应的大小与裸甲藻的摄食率和双毛纺锤水蚤对裸甲藻的摄食选择指数呈现显著的正相关关系。双毛纺锤水蚤对中肋骨条藻的直接摄食死亡率大于营养级联效应,从而导致中肋骨条藻生物量的降低。因此,营养级联效应对中型浮游动物摄食浮游植物的影响要弱于中型浮游动物的直接摄食作用。