The effects of phenoseason and storm characteristics on throughfall solute washoff and leaching dynamics from a temperate deciduous forest canopy.
The effects of phenoseason and storm characteristics on throughfall solute washoff and leaching dynamics from a temperate deciduous forest canopy.
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DOI：
10.1016/j.scitotenv.2012.04.060
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发表时间：
2012-07
期刊：
影响因子：
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通讯作者：
J. V. Van Stan;D. Levia;S. Inamdar;M. Lepori-Bui;M. Mitchell
中科院分区：
文献类型：
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作者：
J. V. Van Stan;D. Levia;S. Inamdar;M. Lepori-Bui;M. Mitchell
淋失离子通量的季节变化和淋失动力学是影响森林生态系统生物地球化学循环的一个重要过程，特别是对于具有明显物候季节（或“表型季”）的温带落叶森林。大多数关于温带落叶森林的研究将季节通通量集中到有叶（生长期）和无叶（休眠期），但控制季节性的物候条件需要更精细的尺度划分，包括过渡表型季（叶衰老和出苗期）。为了填补这些空白，我们的研究考察了3年（2008-2010年）期间（有叶、无叶和两个过渡表型季节）的大量和顺序采样降雨事件中Na+、Mg2+、K+、Ca2+、Cl−、SO42−和NO3−的淋失和淋失动力学。由于雨水冲刷和淋溶溶质通量也与降雨条件密切相关，我们通过风暴事件对比图和因子方差分析进一步研究了风暴特征对淋溶为主（Na+和Cl−）和淋溶为主（K+, Ca2+, Mg2+）通量的影响。在不同的气象条件下（p<0.001），在不同的表型季节区（p<0.00001）内嵌套的浸出溶质通量和washhoff溶质通量存在显著差异。表型季节washoff Na+和Cl−通量似乎与叶面积关系更密切；而所有溶质的淋溶通量和冠层交换更符合主要物候变化（此时冠层往往代谢最活跃）。淋溶Mg2+、K+、Ca2+和SO42−通量的最大差异不在全叶和无叶表型季之间（差异33-80%），而是在过渡时期之间（叶片衰老期比叶片出苗期大80 - 200倍）。然而，在两个过渡表型季节，风暴内平均冠层NO3−淋失从低损失（1μmolcm−2h−1）到冠层吸收（- 2μmolcm−2h−1）不等。衰老过程中，K+、Ca2+、Mg2+的交换性明显增强，且Ca2+和Mg2+被冠层束缚得更紧。除K+和SO42−外，所有测量的溶质的浸出率和通量都可以忽略不计，甚至为负。我们的研究结果表明，在温带落叶生态系统中，森林土壤穿透溶质通量的时间和大小的变化可能归因于物候划分的季节和风暴条件。
Seasonal variations in the washoff and leaching dynamics of throughfall ionic fluxes represent a significant process affecting the biogeochemical cycling of forested ecosystems—particularly for temperate deciduous forests with distinct phenological seasons (or “phenoseasons”). Most studies on temperate deciduous forests aggregate seasonal throughfall fluxes to the leafed (growing) and leafless (dormant) periods, yet the phenological conditions controlling seasonality demand finer-scale demarcations that include the transitional phenoseasons (leaf senescence and emergence). To fill these gaps our study examines the washoff and leaching dynamics of Na+, Mg2+, K+, Ca2+, Cl−, SO42−, and NO3−throughfall derived from bulk and sequentially sampled rain events across leafed, leafless and both transitional phenoseasons over a 3-year period (2008–2010). As throughfall washoff and leached solute fluxes are also closely-coupled to rainfall conditions, we further examine the effects of storm characteristics on phenoseasonal washoff-dominated (Na+and Cl−) and leaching-dominated (K+, Ca2+, Mg2+) fluxes through intrastorm event comparison plots and factorial MANOVA. Highly significant differences in leached and washoff solute fluxes were found across meteorological conditions (p<0.001) nested within phenoseasonal divisions (p<0.00001). Phenoseasonal washoff Na+and Cl−fluxes seemed to be more closely related to leaf area; whereas, leaching flux and canopy exchange of all solutes to correspond more with major phenological changes (when the canopies tend to be most metabolically active). The greatest differences in leached Mg2+, K+, Ca2+, and SO42−fluxes were not between the full leafed and leafless phenoseasons (33–80% difference), but between the transitional periods (80 to 200 fold greater during leaf senescence than leaf emergence). Intrastorm average canopy NO3−leaching, however, ranged from low losses (1μmolcm−2h−1) to canopy uptake (−2μmolcm−2h−1) during both transitional phenoseasons. K+, Ca2+, Mg2+were all markedly more exchangeable during senescence, with Ca2+and Mg2+being more tightly held by the canopy. Leaching rates and fluxes for all measured solutes were negligible to negative during emergence, except for K+and SO42−. Our results indicate that much of the variance in timing and magnitude of throughfall solute fluxes to forest soils within temperate deciduous ecosystems may be ascribed to phenologically-delineated seasons and storm conditions.