Controls on spatial and temporal variation of nutrient uptake in three Michigan headwater streams
Controls on spatial and temporal variation of nutrient uptake in three Michigan headwater streams
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DOI：
10.4319/lo.2007.52.5.1964
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发表时间：
2007-09
影响因子：
4.5
通讯作者：
T. Hoellein;J. Tank;E. Rosi-Marshall;S. Entrekin;G. Lamberti
中科院分区：
文献类型：
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作者：
T. Hoellein;J. Tank;E. Rosi-Marshall;S. Entrekin;G. Lamberti
从2003年5月到2004年4月，我们在三条森林源溪流的两个河段测量了铵（NH4+）、硝酸盐（NO3−）和磷酸盐（可溶性活性磷[SRP]）的全流吸收量，共8次（每种营养物类型n = 46次）。我们还测量了可能影响吸收的因素，包括环境营养浓度、全流代谢和有机物存储量。在所有三条河流中，我们在春季测量了最高的NH4+和NO3−吸收速率（Vf）。低环境NH4+浓度限制了两条河流对NH4+的吸收。其中一条河流在夏季环境NO3−浓度升高时，NO3−Vf降低。SRP Vf的时间模式在不同的河流中有所不同，但与环境SRP浓度的变化无关。然而，在所有三条河流中，SRP Vf的季节变化受到异养代谢的强烈影响（通过群落呼吸测量；State Creek r = 0.81, p = 0.03; Shane Creek r = 0.89, p < 0.01; Walton Creek r = 0.91, p < 0.01）。虽然异养过程通常在森林源溪流中占主导地位，但我们发现溪流中养分吸收的变异性也可以用自养活动相关的变量来解释（即大型无机基质和总初级生产的比例覆盖）。我们认为，本研究中自养的意外影响是河流采样频率的结果，其中包括冬季和春季，而不是典型的采样季节。我们的研究表明，研究跨河流和不同季节的养分吸收可以深入了解控制养分吸收参数的因素。
We measured whole‐stream uptake of ammonium (NH4+), nitrate (NO3−), and phosphate (as soluble reactive phosphorus [SRP]) in two reaches of three forested headwater streams eight times from May 2003 to April 2004 (n = 46 measurements per nutrient type). We also measured factors that could affect uptake, including ambient nutrient concentrations, whole‐stream metabolism, and organic matter standing stocks. In all three streams, we measured the highest rates of NH4+ and NO3− uptake velocity (Vf) during the spring. Low ambient NH4+ concentrations limited NH4+ uptake (U) in two streams. In one stream, when ambient NO3− concentrations increased during summer, NO3− Vf decreased. Temporal patterns of SRP Vf varied among streams, but were unrelated to variability in ambient SRP concentration. However, in all three streams, seasonal variation in SRP Vf was strongly influenced by heterotrophic metabolism (as measured by community respiration; State Creek r = 0.81, p = 0.03; Shane Creek r = 0.89, p < 0.01; Walton Creek r = 0.91, p < 0.01). Although heterotrophic processes typically dominate in forested headwater streams, we found that variability in nutrient uptake among streams was also explained by variables related to autotrophic activity (i.e., proportion coverage of large inorganic substrata and gross primary production). We suggest that the unexpected influence of autotrophy in this study was a result of stream sampling frequency, which included winter and spring—seasons not typically sampled. Our study demonstrates that examining nutrient uptake across streams and during different seasons can provide insight into factors controlling nutrient uptake parameters.