Controls of streamwater dissolved inorganic carbon dynamics in a forested watershed
Controls of streamwater dissolved inorganic carbon dynamics in a forested watershed
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DOI：
10.1023/a:1021183023963
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发表时间：
2003-03-01
期刊：
影响因子：
4
通讯作者：
Finlay, JC
中科院分区：
文献类型：
--
作者：
Finlay, JC
本文研究了北加州温带森林流域河流溶解无机碳（DIC）来源的控制和沿河流大小和生产力梯度的循环。在严重遮荫的河流中，溶解的CO2 （CO2 (aq)）的动态与较大的、开放的遮荫地点形成强烈对比。在冠层盖度为97%的河流中，CO2 （aq）在基流期最高（达540 muM），且与流量呈负相关。藻类光合作用对CO2 （(aq)）的影响最小，河流CO2 （(aq)）主要受地下水CO2 （(aq)）输入和大气脱气损失控制。与小型河流相比，大型开放式河流的CO2 （(aq)）在基流期间的中午通常低于大气水平，并且与排放量呈正相关。这里，溪流CO2 （(aq)）受到自养和异养过程平衡的强烈影响。HCO3-的动力学不太复杂。HCO3-和Ca2+与流量呈正相关，与流量负相关，与流量大小无明显关系。DIC的稳定碳同位素比值（即δ (13)C DIC）随河流大小和流量的增加而增加，表明DIC的来源与河流不同。在夏季基流中，由于微生物呼吸产生的CO2 （(aq)）和碳酸盐风化产生的HCO3-的影响，δ (13)C - DIC在最小的流中（最小值为-17.7 ppm）被C-13耗尽。在较大的溪流和河流中，δ (13)C DIC较高（高达-6.6 ppm），这是由于藻类对CO2 （aq）的吸收增强了大气CO2的入侵。虽然小河流受到地下水输入的影响，但二氧化碳（aq）的模式和来自稳定同位素的证据表明，河流代谢和与大气的二氧化碳交换对河流和河流碳循环有很强的影响。
I investigated controls of stream dissolved inorganic carbon (DIC) sources and cycling along a stream size and productivity gradient in a temperate forested watershed in northern California. Dissolved CO2 (CO2 ((aq))) dynamics in heavily shaded streams contrasted strongly with those of larger, open canopied sites. In streams with canopy cover > 97%, CO2 ((aq)) was highest during baseflow periods (up to 540 muM) and was negatively related to discharge. Effects of algal photosynthesis on CO2 ((aq)) were minimal and stream CO2 ((aq)) was primarily controlled by groundwater CO2 ((aq)) inputs and degassing losses to the atmosphere. In contrast to the small streams, CO2 ((aq)) in larger, open-canopied streams was often below atmospheric levels at midday during baseflow and was positively related to discharge. Here, stream CO2 ((aq)) was strongly influenced by the balance between autotrophic and heterotrophic processes. Dynamics of HCO3- were less complex. HCO3- and Ca2+ were positively correlated, negatively related to discharge, and showed no pattern with stream size. Stable carbon isotope ratios of DIC (i.e. delta(13)C DIC) increased with stream size and discharge, indicating contrasting sources of DIC to streams and rivers. During summer baseflows, delta(13)C DIC were C-13-depleted in the smallest streams (minimum of -17.7parts per thousand) due to the influence of CO2 ((aq)) derived from microbial respiration and HCO3- derived from carbonate weathering. delta(13)C DIC were higher (up to -6.6parts per thousand) in the larger streams and rivers due to invasion of atmospheric CO2 enhanced by algal CO2 ((aq)) uptake. While small streams were influenced by groundwater inputs, patterns in CO2 ((aq)) and evidence from stable isotopes demonstrate the strong influence of stream metabolism and CO2 exchange with the atmosphere on stream and river carbon cycles.