Department of Natural Resources, Cornell University, Fernow Hall, Ithaca, New York 14853, USA.
Ecol Appl. 2011 Oct;21(7):2357-66. doi: 10.1890/10-2009.1.
The rapid increase in residential land area in the United States has raised concern about water pollution associated with nitrogen fertilizers. Nitrate (NO3-) is the form of reactive N that is most susceptible to leaching and runoff; thus, a more thorough understanding of nitrification and NO3(-) availability is needed if we are to accurately predict the consequences of residential expansion for water quality. In particular, there have been few assessments of how the land use history, housing density, and age of residential soils influence NO3(-) pools and fluxes, especially at depth. In this study, we used 1 m deep soil cores to evaluate potential net nitrification and mineralization, microbial respiration and biomass, and soil NO3(-) and NH4+ pools in 32 residential home lawns that differed by previous land use and age, but had similar soil types. These were compared to eight forested reference sites with similar soils. Our results suggest that a change to residential land use has increased pools and production of reactive N, which has clear implications for water quality in the region. However, the results contradict the common assumption that NO3(-) production and availability is dramatically higher in residential soils than in forests in general. While net nitrification (128.6 +/- 15.5 mg m(-2) d(-1) vs. 4.7 +/- 2.3 mg m(-2) d(-1); mean +/- SE) and exchangeable NO3(-) (3.8 +/- 0.5 g/m2 vs. 0.7 +/- 0.3 g/m2) were significantly higher in residential soils than in forest soils in this study, these measures of NO3(-) production and availability were still notably low, comparable to deciduous forest stands in other studies. A second unexpected result was that current homeowner management practices were not predictive of NO3(-) availability or production. This may reflect the transient availability of inorganic N after fertilizer application. Higher housing density and a history of agricultural land use were predictors of greater NO3(-) availability in residential soils. If these factors are good predictors across a wider range of sites, they may be useful indicators of NO3(-) availability and leaching and runoff potential at the landscape scale.
美国住宅用地面积的快速增加引起了人们对与氮肥有关的水污染的关注。硝酸盐（NO3-）是最易淋溶和流失的活性氮形式；因此，如果要准确预测住宅扩张对水质的影响，就需要更深入地了解硝化作用和 NO3-的可利用性。特别是，很少有评估住宅土壤的土地利用历史、住房密度和年龄如何影响 NO3-库和通量，尤其是在深层土壤中。在这项研究中，我们使用 1 米深的土壤芯来评估 32 个住宅草坪的潜在净硝化和矿化、微生物呼吸和生物量以及土壤 NO3-和 NH4+库的情况，这些住宅草坪的土地利用和年龄不同，但土壤类型相似。这些与具有相似土壤的八个森林参考地点进行了比较。我们的结果表明，住宅土地利用的变化增加了活性氮的库和产量，这对该地区的水质有明显的影响。然而，结果与普遍的假设相矛盾，即一般来说，住宅土壤中的 NO3-产生和可利用性比森林高得多。虽然本研究中住宅土壤的净硝化作用（128.6 +/- 15.5 mg m(-2) d(-1) 与 4.7 +/- 2.3 mg m(-2) d(-1)；平均值 +/- SE）和可交换的 NO3-（3.8 +/- 0.5 g/m2 与 0.7 +/- 0.3 g/m2）明显高于森林土壤，但这些 NO3-产生和可利用性的测量值仍然相当低，与其他研究中的落叶林相当。第二个意想不到的结果是，当前房主的管理实践并不能预测 NO3-的可利用性或产生。这可能反映了施肥后无机 N 的暂时可用性。较高的住房密度和农业土地利用历史是住宅土壤中 NO3-可利用性较高的预测因素。如果这些因素在更广泛的范围内是良好的预测指标，它们可能是景观尺度上 NO3-可利用性和淋溶及流失潜力的有用指标。
