Stream water carbon controls in seasonally snow-covered mountain catchments: impact of inter-annual variability of water fluxes, catchment aspect and seasonal processes
Stream water carbon controls in seasonally snow-covered mountain catchments: impact of inter-annual variability of water fluxes, catchment aspect and seasonal processes
复制标题
季节性积雪山区流域的溪流水碳控制：水通量年际变化、流域状况和季节过程的影响
DOI：
10.1007/s10533-013-9929-y
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发表时间：
2014
期刊：
影响因子：
4
通讯作者：
J. Chorover
中科院分区：
文献类型：
--
作者：
J. Perdrial;J. McIntosh;A. Harpold;P. Brooks;Xavier E. Zapata;J. Ray;T. Meixner;T. Kanduč;M. Litvak;P. Troch;J. Chorover
摘要
溪水碳(C)输出是季节性积雪覆盖的山地生态系统碳流失的重要途径之一，有必要对总体控制进行评估。然而，这种评估是具有挑战性的，因为水通量或流动路径的变化、季节性过程以及流域特有的特征都起到了一定的作用。在这项研究中，我们阐明了：(I)水通量的变化(通过比较不同湿度的年份)，(Ii)集水方面[北向(NF)与向南(SF)]和(Iii)季节(融雪与夏季)对新墨西哥州Valles Caldera国家级保护区内森林流域中所有形式的溶解有机碳(DOC)、有色溶解有机物(CDOM)和溶解无机C(DIC)的影响。年水和碳通量之间的显著相关性(例如DOC R2=0.83，p<；(0.02))证实了年水系水量是C外流的主要控制因素，以前的研究表明，C外流很可能来自混合良好的地下水水库。然而，CDOM全年表现出以陆地为主的荧光特征(59%-71%)，表明CDOM的组成受到强烈的河岸和近流土壤控制。融雪过程中，由于坡面冲刷，纳滤流输送的土壤C(40%DOC，56%DIC)明显多于SF流，水作为C库的作用叠加在其对照上。冬季降水的年际变化对调节年度河流C排放至关重要，例如，在干燥(相对于潮湿)的冬季之后，将C排放减少三倍。在较温暖的夏季，溶解氧饱和度%下降，δ13CDIC增加，CDOM呈现出更多的微生物特征，与溪流和河岸土壤的异养呼吸一致。由于溪流C的孵化和土壤呼吸，$$P_{\Text{CO}}_{2}}$$pCO2增加到大气值的12倍，导致大量脱气。
Abstract
Stream water carbon (C) export is one important pathway for C loss from seasonally snow-covered mountain ecosystems and an assessment of overarching controls is necessary. However, such assessment is challenging because changes in water fluxes or flow paths, seasonal processes, as well as catchment specific characteristics play a role. For this study we elucidate the impact of: (i) changes in water flux (by comparing years of variable wetness), (ii) catchment aspect [north-facing (NF) vs. south-facing (SF)] and (iii) season (snowmelt vs. summer) on all forms of dissolved stream water C [dissolved organic C (DOC), chromophoric dissolved organic matter (CDOM) and dissolved inorganic C (DIC)] in forested catchments within the Valles Caldera National Preserve, New Mexico. The significant correlation between annual water and C fluxes (e.g. DOC r2 = 0.83, p < 0.02) confirms annual stream water discharge as the overarching control on C efflux, likely from a well-mixed ground water reservoir as indicated by previous research. However, CDOM exhibited a dominantly terrestrial fluorescence signature (59–71 %) year round, signaling a strong riparian and near stream soil control on CDOM composition. During snowmelt, the role of water as C transporter was superimposed on its control as C reservoir, when the NF stream transported significantly more soil C (40 % DOC, 56 % DIC) than the SF stream as a result of hillslope flushing. Inter-annual variations in winter precipitation were paramount in regulating annual stream C effluxes, e.g., reducing C effluxes three-fold after a dry (relative to wet) winter season. During the warmer summer months % dissolved oxygen saturation decreased, δ13CDIC increased and CDOM assumed a more microbial signature, consistent with heterotrophic respiration in the stream and riparian soils. As a result of stream C incubation and soil respiration, $$ P_{{{\text{CO}}_{2} }} $$PCO2 increased up to 12 times atmospheric values leading to substantial degassing.