Loupe T M, Miller W W, Johnson D W, Sedinger J S, Carroll E M, Walker R F, Murphy J D, Stein C M
College of Agric., Biotechnology, and Nat. Resources, Univ. of Nevada, Reno, NV 89512, USA.
J Environ Qual. 2009 Feb 6;38(2):537-47. doi: 10.2134/jeq2007.0494. Print 2009 Mar-Apr.
Fire suppression in Sierran ecosystems creates a substantial wildfire hazard and may exacerbate nutrient inputs into Lake Tahoe by allowing the buildup of O horizon material, which serves as a source for high N and P concentrations in runoff water. The purpose of this study was to evaluate the effects of biomass reduction using cut-to-length mechanical harvest followed by chipping and controlled burning on surface runoff volume and water quality. Based on previous findings regarding N and P leaching flux and soil solution concentrations, we hypothesized that controlled burning and/or mechanical harvest with residue chipping does not increase inorganic N, P, and S concentrations in overland flow. Runoff, snowmelt, and rainfall were collected, volume measurements were taken, and samples were analyzed for NO(3)-N, NH(4)-N, PO(4)-P, and SO(4). Runoff volume, season, and year were identified as important parameters influencing overland flow nutrient concentrations and loads. Higher nutrient concentrations were commonly associated with summer rather than winter runoff, but the opposite was true for nutrient loads due to the higher runoff volumes. Treatment (unharvested, harvested, unburned, burned) effect was a strong predictor for discharge loads of NO(3)-N and SO(4) but was a weak predictor for PO(4)-P. Discharge loads of NO(3)-N and SO(4) were greater for the unburned harvested and the burned unharvested treatments than for the unburned, unharvested control sites or the burned and harvested combined treatment. Although mechanical harvest and/or controlled burning had a small initial impact on increased nutrient loading, the effects were minimal compared with background levels. Hence, these management practices may have the potential to improve forest health without the danger of large-magnitude nutrient mobilization and degradation of runoff water quality found with wildfire.
内华达山脉生态系统中的灭火措施会带来严重的野火隐患，并且可能通过促使O层物质堆积，加剧营养物质流入太浩湖，而O层物质是径流水中高氮和高磷浓度的一个来源。本研究的目的是评估采用短伐机械采伐，随后进行削片和控制焚烧来减少生物量，对地表径流量和水质的影响。基于之前有关氮、磷淋失通量和土壤溶液浓度的研究结果，我们假设控制焚烧和/或带残余物削片的机械采伐不会增加坡面流中无机氮、磷和硫的浓度。收集了径流、融雪水和降雨，测量了体积，并对样品进行了硝酸盐氮、铵态氮、磷酸磷和硫酸根的分析。径流量、季节和年份被确定为影响坡面流营养物质浓度和负荷的重要参数。较高的营养物质浓度通常与夏季径流而非冬季径流相关，但由于夏季径流量较大，营养物质负荷情况则相反。处理方式（未采伐、采伐、未燃烧、燃烧）对硝酸盐氮和硫酸根的排放负荷是一个很强的预测指标，但对磷酸磷则是一个较弱的预测指标。未燃烧采伐处理和燃烧未采伐处理的硝酸盐氮和硫酸根排放负荷，高于未燃烧、未采伐的对照地点或燃烧与采伐结合处理。尽管机械采伐和/或控制焚烧对营养物质负荷增加的初始影响较小，但与背景水平相比，其影响微不足道。因此，这些管理措施可能有改善森林健康的潜力，而不会像野火那样带来大量营养物质迁移和径流水质恶化的危险。
