Effect of water table drawdown on peatland dissolved organic carbon export and dynamics     

M. Strack  J. M. Waddington  R. A. Bourbonniere  E. L. Buckton  K. Shaw  P. Whittington  J. S. Price 《水文研究》2008,22(17):3373-3385

Peatlands play an important role in the global carbon cycle, and loss of dissolved organic carbon (DOC) has been shown to be important for peatland carbon budgets. The objective of this study was to determine how net production and export of DOC from a northern peatland may be affected by disturbance such as drainage and climate change. The study was conducted at a poor fen containing several pool–ridge complexes: (1) control site–no water table manipulation; (2) experimental site–monitored for one season in a natural state and then subjected to a water table drawdown for 3 years; (3) drained site–subjected to a water table drawdown 9 years prior to monitoring. The DOC concentration was measured in pore water along a microtopographic gradient at each site (hummock, lawn and hollow), in standing water in pools, and in discharge from the experimental and drained sites. The initial water table drawdown released ～3 g of carbon per square metre in the form of DOC, providing a large pulse of DOC to downstream ecosystems. This value, however, represents only 1–9% of ecosystem respiration at this site. Seasonal losses of DOC following drainage were 8–11 g of carbon per square metre, representing ～17% of the total carbon exchange at the experimental study site. Immediately following water table drawdown, DOC concentrations were elevated in pore water and open water pools. In subsequent seasons, DOC concentration in the pool declined, but remained higher than the control site even 11 years after water‐table drawdown. This suggests continued elevated net DOC production under lower water table conditions likely related to an increase in vegetation biomass and larger water table fluctuations at the experimental and drained sites. However, the increase in concentration was limited to initially wet microforms (lawns and hollows) reflecting differences in vegetation community changes, water table and soil subsidence along the microtopographic gradient. Copyright © 2008 John Wiley & Sons, Ltd and Her Majesty the Queen in right of Canada.  相似文献   

Comparative biomass structure and estimated carbon flow in food webs in the deep Gulf of Mexico     

Gilbert T. Rowe  Chihlin Wei  Clifton Nunnally  Richard Haedrich  Paul Montagna  Jeffrey G. Baguley  Joan M. Bernhard  Mary Wicksten  Archie Ammons  Elva Escobar Briones  Yousra Soliman  Jody W. Deming 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(24-26):2699

A budget of the standing stocks and cycling of organic carbon associated with the sea floor has been generated for seven sites across a 3-km depth gradient in the NE Gulf of Mexico, based on a series of reports by co-authors on specific biotic groups or processes. The standing stocks measured at each site were bacteria, Foraminifera, metazoan meiofauna, macrofauna, invertebrate megafauna, and demersal fishes. Sediment community oxygen consumption (SCOC) by the sediment-dwelling organisms was measured at each site using a remotely deployed benthic lander, profiles of oxygen concentration in the sediment pore water of recovered cores and ship-board core incubations. The long-term incorporation and burial of organic carbon into the sediments has been estimated using profiles of a combination of stable and radiocarbon isotopes. The total stock estimates, carbon burial, and the SCOC allowed estimates of living and detrital carbon residence time within the sediments, illustrating that the total biota turns over on time scales of months on the upper continental slope but this is extended to years on the abyssal plain at 3.6 km depth. The detrital carbon turnover is many times longer, however, over the same depths. A composite carbon budget illustrates that total carbon biomass and associated fluxes declined precipitously with increasing depth. Imbalances in the carbon budgets suggest that organic detritus is exported from the upper continental slope to greater depths offshore.The respiration of each individual “size” or functional group within the community has been estimated from allometric models, supplemented by direct measurements in the laboratory. The respiration and standing stocks were incorporated into budgets of carbon flow through and between the different size groups in hypothetical food webs. The decline in stocks and respiration with depth were more abrupt in the larger forms (fishes and megafauna), resulting in an increase in the relative predominance of smaller sizes (bacteria and meiofauna) at depth. Rates and stocks in the deep northern GoM appeared to be comparable to other continental margins where similar comparisons have been made.  相似文献   

生态环境中的硒及其地方病     

易秀 《地球科学与环境学报》2000,22(4)

总结了硒的来源及在环境介质中的分布特点 ;讨论了硒的形态及影响其生物有效性的因素、硒的生物地球化学循环 ;分析了硒与地方病的关系以及它在生态环境中所起的重要作用  相似文献   

Biogeochemical cycling in the Taiwan Strait   总被引：2，自引：1，他引：1  

Hema Naik  Chen-Tung Arthur Chen 《Estuarine, Coastal and Shelf Science》2008,78(4):603-612

Based on repeat observations made during 2001–2003 along two transects in the Taiwan Strait this study aims at understanding factors controlling primary productivity with an emphasis on biogeochemical cycling of nitrogen, the major bio-limiting macronutrient. The Taiwan Strait receives copious supplies of nutrients through river runoff and upwelling in its western and northeastern parts, respectively, but the phytoplankton biomass, as inferred from the Chl a concentration, does not appear to be commensurately high. It is proposed that high water turbidity results in light limitation of primary productivity, especially in the western part of the strait. The accumulation of nitrite in the surface mixed layer appears to be due to nitrate reduction during phytoplankton assimilation, whereas in the near-bottom waters nitrite is most likely produced during nitrification. The net balance between input and loss of nitrogen is inferred from the nitrogen tracer N*. The Taiwan Strait is found to be a net recipient of combined nitrogen.  相似文献   

基于次溴酸钠氧化-氨基磺酸还原测定沉积物15N加富培养样品中的15NH+4的方法探索     

徐颢铭  宋国栋  刘素美  梁生康  张桂玲 《海洋学报》2022,44(1):147-154

沉积物中的异化硝酸盐还原过程是海洋中活性氮转化的关键过程之一.不同于反硝化和厌氧铵氧化,异化硝酸盐还原为铵(DNRA)是将硝酸盐直接还原为铵,而不是以氮气的形态移除,这有可能会加重水体富营养化和缺氧.目前测定沉积物中异化硝酸盐还原过程的主要手段是15N标记培养技术.为了准确评估DNRA的潜在速率,首先要准确测定加富样品...  相似文献   

Tidal exchange of nitrogen and phosphorus between a mesohaline vegetated marsh and the surrounding estuary in the lower Chesapeake Bay     

Thomas G. Wolaver  Joseph C. Zieman  Richard Wetzel  Ken L. Webb 《Estuarine, Coastal and Shelf Science》1983,16(3):321-332

A 22-month study was conducted to determine the exchange of nitrogen and phosphorus between a mesohaline vegetated marsh in the Carter's Creek area of Virginia and the surrounding estuary, focusing on the role of the vegetated marsh surface in the processing of these constituents. On an annual basis there was a removal of $\text{NH}{}_4{}^{\mathrm{+}}$, $\text{PO}{}_4{}^{\mathrm{3?}}$, $\text{NO}{}_3{}^{\mathrm{?}}$, dissolved organic nitrogen, dissolved organic phosphorus, particulate nitrogen and particulate phosphorus from the tidal water as it resided on the vegetated marsh. Only nitrite was transported from the marsh to the estuary. Most of the nitrogen and phosphorus species showed distinct seasonal trends with respect to the direction of transport except nitrate and orthophosphate. The ammonium flux data indicates that this nutrient was removed from the inundating water during late spring and fall, with a slight release of this constituent into the tidal water during the late summer. The transport of nitrite was from the estuary to the marsh for most of the year except during the fall. The large release of this nutrient into the tidal water at this time is associated with the senescence of the marsh vegetation. There was a large removal of DON from the tidal water during the fall, while the flux of DOP was from the estuary to the marsh for most of the year except during the summer. The largest removal of particulate nitrogen and phosphorus from the tidal water occurred during the summer months when the turbidity of the tidal water was highest, especially when wave scouring of the mudflats brings material into the water column. A loss of particulate nitrogen from the marsh to the estuary was evident during the fall and winter.  相似文献   

Silicon limitation on primary production and its destiny in Jiaozhou Bay, China Ⅳ: Study on cross-bay transect from estuary to ocean     

杨东方  陈豫  高振会  张经  王凡 《中国海洋湖沼学报》2005,(1)

1 INTRODUCTION Terrestrial matter is continuously loaded into ocean by rivers and up taken by myriad organisms who would ultimately sink to the sea bottom, whichconstitutes a complete process of transferring terrestrial matter from land to sea. Among this dynamic process, diatoms are very important in theNo.1 YANG et al.: Silicon limitation on primary production and its destiny 73material cycle. Phytoplankton is a prime mover in the conversion from inorganic matter to organic in marine…  相似文献   

气候变化、火干扰与生态系统碳循环   总被引：6，自引：0，他引：6       下载免费PDF全文

胡海清  魏书精  孙龙  王明玉 《干旱区地理》2013,36(1):57-75

 随着全球变暖的日益显著,气候变化及其影响越来越受到广泛关注。火干扰作为森林生态系统碳循环的一个重要组成部分,其干扰过程是对碳的再分配过程,因而对区域乃至全球的碳循环产生重要影响。气候变化、火干扰与生态系统碳循环三者之间存在因果循环关系,正确认识气候变化与火干扰的复杂关系及双向反馈作用,以及火干扰在生态系统碳循环中的作用,这对制定科学合理的火干扰管理策略,提高生态系统管理水平,减少碳排放,促进碳增汇,减缓全球变化速率均有重要意义。从两个方面阐述了气候变化、火干扰与生态系统碳循环之间的交互作用关系：气候变化与火干扰相互影响关系及双向反馈作用,分别从气候变化对火干扰的影响及火干扰对气候变化的影响两个方面阐述了两者之间的相互影响关系;火干扰与森林生态系统碳循环的交互作用,分别从火干扰对森林生态系统碳循环的影响及模型方法在模拟火干扰对森林生态系统碳循环影响中的应用两个方面论述火干扰对森林生态系统碳循环的影响及其定量评价模型方法。目前火干扰直接碳排放的模型方法比较完善,而间接影响碳循环的模型方法并不成熟,许多方法局限于定性描述,因此,应进一步探讨集成实地测量、遥感观测和模型模拟的跨尺度火干扰对碳循环的影响研究,注重尺度的转换问题。最后,提出了气候变暖背景下火干扰管理的路径选择,以及对今后的研究方向进行了展望。  相似文献   

新疆天然矿泉水成因类型及资源远景区预测   总被引：1，自引：0，他引：1  

顾新鲁  王占和  曾永刚  杜健  丁光发 《新疆地质》2012,30(1):95-98

新疆天然矿泉水资源主要为锶、偏硅酸、碳酸、锂、锌、矿物盐6种类型,以锶水和偏硅酸水类型最多,成因类型可分为构造断裂深循环淋溶型、裂隙浅循环淋溶型、补给富集埋藏型3种,针对上述3种成因将现状矿泉划分为7种典型矿床模式,在此基础上提出并分析已形成2处矿泉水田与预测9处天然矿泉水资源远景区,对全疆天然矿泉水勘察及开发具一定指导意义.  相似文献   

Nutrient budget of a montane evergreen broad‐leaved forest at Ailao Mountain National Nature Reserve,Yunnan, southwest China     

Wenyao Liu  John E. D. Fox  Zaifu Xu 《水文研究》2003,17(6):1119-1134

Hydrological fluxes and associated nutrient budget were studied during a 2 year period (1998–99) in a montane moist evergreen broad‐leaved forest at Ailao Mountain, Yunnan. Water samples of rainfall, throughfall, and stemflow, and of surface runoff, soil water, and stream flow were collected bimonthly to determine the concentration and fluxes of nutrients. Soil budgets were determined from the difference between precipitation input (including nutrient leaching from canopy) and output via runoff and drainage. The forest was characterized by low canopy interception and surface runoff, and high percolation and stream flow. Concentrations of nutrients were increased in throughfall and stemflow compared with precipitation. Surface runoff and drainage water had higher nutrient concentrations than precipitation and stream water. Total nitrogen and NH₄⁺‐N concentrations were higher in soil water than stream water, whereas K⁺, Ca²⁺, and Mg²⁺ concentrations were lower in the former than the latter. Annual nutrient fluxes decreased with soil depth following the pattern of water flux. Annual losses of most nutrient elements via stream flow were less than the corresponding inputs via throughfall and stemflow, except for calcium, for which solute loss was greater than the inputs via precipitation. Leaching losses of that element may be compensated by weathering. Losses of nitrogen, phosphorus, potassium, magnesium, sodium, and sulphur could be replaced through atmospheric inputs. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献