Effects of prescribed burning and drought on the solute chemistry of mixed-conifer forest streams of the Sierra Nevada, California
Effects of prescribed burning and drought on the solute chemistry of mixed-conifer forest streams of the Sierra Nevada, California
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规定燃烧和干旱对加利福尼亚州内华达山脉混合针叶林溪流溶质化学的影响
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
J. Melack
中科院分区：
文献类型：
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作者：
Michael R. Williams;J. Melack
1984 - 1995年，在加州内华达山脉的两个混合针叶树集水区（Tharp和Log小溪），测量了大气沉积物和溪流中的溶质浓度。在萨普河流域的规定燃烧的影响显着增加了大多数溶质在溪流中的浓度。在规定的燃烧后的第一年，酸性阴离子的体积加权平均浓度（VWM）的增加比例大于碱性阳离子，和ANC（酸中和能力）增加一倍以上。燃烧后，河水中SO_4 ~（2-）和NO_3 ~-的含量比其它离子增加得多，但燃烧前后河水pH值无明显变化。燃烧发生后第一年的VWM SO 42-和NO3-浓度分别比燃烧前基线高出约16倍和2,000倍，而Cl-则增加了4倍。H+、NO3-、NH3+、SO 42-和Cl-的净保留量（降水输入量减去溪水输出量）在两个流域都出现了，除了1990年秋季对萨普河流域进行了规定的燃烧后，这导致了燃烧后第一年SO 42-、Cl-和K+的净输出。到火烧后第3年末，大部分溶质仍高于干扰前浓度，而H+和SiO2仍低于干扰前浓度。Na+，Ca 2+和SO 42-的浓度周期性增加，ANC和SiO2的减少发生在6年的干旱监测在邻近的未受干扰的集水区的日志溪。
Solute concentrations in atmospheric depositionand stream water were measured in two mixed-conifercatchments (Tharp‘s and Log creeks) in the SierraNevada of California from 1984 through 1995, a periodincluding a 6-year drought and a prescribed burn inone catchment. The effects of prescribed burning inthe Tharp‘s Creek catchment significantly increasedthe concentrations of most solutes in stream water. In the first year after prescribed burning, the VWM(volume-weighted mean) concentrations of acid anionsin stream water increased proportionally more thanthose of the base cations, and ANC (acid neutralizingcapacity) more than doubled. Sulfate and NO3- increased proportionally more in streamwater than any other ions after the fire, but pre- andpost-burn VWM pH were not significantlydifferent. VWM SO42- and NO3-concentrations the first year after burning occurredwere about 16- and 2,000-fold above pre-burnbaselines, respectively, while that of Cl-increased 4-fold. Net retention (precipitationinputs minus streamwater outputs) of H+,NO3-, NH3+, SO42- and Cl- occurred in both catchments, except afterprescribed burning of the Tharp’s Creek catchment inthe fall of 1990, which caused a net export ofSO42-, Cl- and K+ thefirst year after the burn. Most solutes remained abovepre-disturbance concentrations by the end of the thirdyear after burning, whereas H+ and SiO2remained below. Periodic increases in theconcentrations of Na+, Ca2+ and SO42-, and decreases in ANC and SiO2occurred during a 6-year drought monitored in theadjacent undisturbed catchment of Log Creek.