The Regulation of Element Concentrations in Mountain Streams in the Northeastern United States
The Regulation of Element Concentrations in Mountain Streams in the Northeastern United States
复制标题
美国东北部山溪中元素浓度的调节
DOI：
10.2307/1942224
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发表时间：
1977
影响因子：
6.1
通讯作者：
P. Vitousek
中科院分区：
文献类型：
--
作者：
P. Vitousek
对美国新罕布什尔州怀特山脉沿海拔梯度和演替梯度分布的57个流域进行了水元素浓度监测。C1 -和SO4 -浓度随海拔升高而降低，这是由于相对蒸散量在海拔梯度上存在差异。Na+、Ca++和Mg++的浓度也随海拔的增加而降低，但坡度更陡。岩石风化/水通量单位以及相对蒸散量控制这些阳离子的浓度。钾和NO3 -浓度在同一河流内和河流之间的季节变化很大。流域间演替状态的差异对控制NO3 -和K+浓度具有重要意义。在相同海拔高度，老年森林生态系统的径流NO3 -、K+和其他植物养分浓度高于中老年演替生态系统的径流。9个没有伐木或其他广泛人为干扰记录的云杉流域的水体NO3 -浓度平均为53微当量/升，而另外5个30年前被记录的云杉流域的水体NO3 -浓度平均为8兆当量/升。控制这些流域水流中元素浓度的主要因素是与供应（降水化学、相对蒸散、岩石风化）和植物养分积累有关的因素。快速生长的演代生态系统可以积累大量的营养元素投入，特别是在生长季节。稳定状态的生态系统，即没有净生物量积累的生态系统，其营养产出等于营养投入。新罕布什尔州空旷流域营养元素损失的增加可以用这些术语来解释。未砍伐或受到其他干扰的生态系统可能存在矿化，植物吸收过量，导致元素输出超过输入。田间试验表明，根沟对植物吸收的阻止导致土壤NO3 -浓度与哈伯德溪实验森林的清净流域的河流中观测到的浓度相当。
Concentrations of elements in streamwater were monitored in 57 watersheds located along elevational and successional gradients in the White Mountains of New Hampshire, USA. Concentrations of C1— and SO4– decreased with increasing elevation as a result of differences in relative evapotranspiration along the elevation gradient. Concentration of Na+, Ca++, and Mg++ also decreased with increasing elevation, but with a steeper slope. Rock weathering/unit of water flux as well as relative evapotranspiration controls concentrations of these cations. Potassium and NO3— concentrations were highly variable, both seasonally within a stream and among streams. Differences among watersheds in terms of successional status are important in controlling NO3— and K+ concentrations. Streams draining old—aged forested ecosystems had higher concentrations of NO3—, K+, and other plant nutrients than did streams draining intermediate—aged successional ecosystems at the same elevation. Nine spruce—fir watersheds which have no record of logging or other extensive human disturbance had streamwater NO3— concentrations averaging 53 microequivalents/litre, while five other spruce—fir watersheds which had been logged 30 yr previously had streamwater NO3— concentrations averaging 8 meq/1. The major factors controlling streamwater concentrations of elements in these watersheds are factors related to supply (precipitation chemistry, relative evapotranspiration, rock weathering) and to plant accumulation of nutrients. Rapidly—growing successional ecosystems can accumulate a large fraction of inputs of nutrient elements, particularly during the growing season. Steady state ecosystems, those with no net biomass accumulation, have nutrient outputs equal to nutrient inputs. The increased losses of nutrient elements from clearcut watersheds in New Hampshire can be explained in these terms. Clearcut or otherwise disturbed ecosystems may have mineralization in excess of plant uptake, leading to element outputs in excess of inputs. Field experiments demonstrated that the prevention of plant uptake by root trenching led to soil NO3— concentrations comparable to those observed in streamwater in the clearcut watershed at Hubbard Brook Experimental Forest.