Soluble soil aluminum alters the relative uptake of mineral nitrogen forms by six mature temperate broadleaf tree species: possible implications for watershed nitrate retention
Soluble soil aluminum alters the relative uptake of mineral nitrogen forms by six mature temperate broadleaf tree species: possible implications for watershed nitrate retention
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DOI：
10.1007/s00442-017-3955-8
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发表时间：
2017-11-01
期刊：
影响因子：
2.7
通讯作者：
Peterjohn, William T.
中科院分区：
文献类型：
--
作者：
Burnham, Mark B.;Cumming, Jonathan R.;Peterjohn, William T.
森林土壤中单体铝（Al 3+）的有效性增加是酸性沉降的一个重要不利影响，它会降低根系生长并抑制养分吸收。有证据表明，Al 3+暴露干扰NO3（-）吸收。如果是真的上层树木，减少立场的NO3（-）的需求可能会增加NO3（-）排放的溪流。这些影响也可能因耐受不同土壤酸度的物种而异。为了检验这些想法，我们测量了NO3（-）和NH 4（+）的相对吸收的变化，由六个树种在原位土壤铝增加使用N-15-标记技术，并测量可溶性土壤铝水平在一个单独的全流域酸化实验在Fernow实验森林（WV）。当暴露于添加Al 3+，无机N的比例为NO3（-）收购下降14%，跨物种，但我们没有检测到减少整体N吸收，也没有树种在此响应不同。在长期酸化试验中，我们发现土壤可溶性Al主要以游离态Al 3+形式存在，酸化流域矿质土壤中Al 3+浓度比未酸化流域高约65 μ M（约250%）。因此，在酸性沉降条件下，土壤Al 3+水平的增加会导致成熟树木对NO3（-）的吸收减少。当我们的N-15吸收结果应用于流域酸化实验时，他们表明，增加Al 3+暴露可使树木对NO3（-）的吸收减少7.73 kg N ha（-1）年（-1），从而增加流域NO3（-）排放。
Increased availability of monomeric aluminum (Al3+) in forest soils is an important adverse effect of acidic deposition that reduces root growth and inhibits nutrient uptake. There is evidence that Al3+ exposure interferes with NO3 (-) uptake. If true for overstory trees, the reduction in stand demand for NO3 (-) could increase NO3 (-) discharge in stream water. These effects may also differ between species that tolerate different levels of soil acidity. To examine these ideas, we measured changes in relative uptake of NO3 (-) and NH4 (+) by six tree species in situ under increased soil Al3+ using a N-15-labeling technique, and measured soluble soil Al levels in a separate whole-watershed acidification experiment in the Fernow Experimental Forest (WV). When exposed to added Al3+, the proportion of inorganic N acquired as NO3 (-) dropped 14% across species, but we did not detect a reduction in overall N uptake, nor did tree species differ in this response. In the long-term acidification experiment, we found that soluble soil Al was mostly in the free Al3+ form, and the concentration of Al3+ was similar to 65 mu M higher (similar to 250%) in the mineral soil of the acidified watershed vs. an untreated watershed. Thus, increased levels of soil Al3+ under acidic deposition cause a reduction in uptake of NO3 (-) by mature trees. When our N-15 uptake results were applied to the watershed acidification experiment, they suggest that increased Al3+ exposure could reduce tree uptake of NO3 (-) by 7.73 kg N ha(-1) year(-1), and thus increase watershed NO3 (-) discharge.