Abstract Managed pine forests cover nearly 130,000 km2 of the Southeastern U.S. and are important to the economic and ecological sustainability of the region. These stands are typically fertilized twice – at establishment and mid-rotation – to enhance timber production during a 25-year rotation. In Florida, Best Management Practices (BMPs) limit fertilizer application rates and require special management zones (SMZs) to reduce nutrient pollution. Recent adoption of numeric nutrient criteria (NNC) for streams and lakes in Florida has raised concerns that forest fertilization, even in compliance with BMPs, may result in excess nutrient loads and degrade stream ecological condition, particularly directly following fertilizer applications. We examined nutrient export dynamics and stream biota in two medium size watersheds (21 and 34 km2, respectively) dominated by loblolly pine (Pinus taeda) plantations in north Florida following fertilization. Over 54 months, we monitored stream discharge, nitrogen (TN, TKN, NO3-N, NH4-N), and phosphorus (TP, orthoP), as well as stream biota (benthic macroinvertebrates, phytoplankton chlorophyll a, periphyton and vascular plants) prior to and following watershed-scale fertilization. We condensed four years of scheduled fertilization into a single year, resulting in nutrient inputs substantially larger than typical. Because flow variation strongly controlled nutrient concentrations, we assessed pre- and post-fertilization concentration-discharge (C-Q) relationships, which remained unchanged. Annual mass export of N and P also remained unchanged, suggesting landscape retention of additional loads. Likewise, we observed no systematic change in biological indicators. These results suggest forest fertilization at BMP rates is unlikely to increase stream nutrient export, supporting the contention that fertilized pine forests in the southeastern coastal plain are protective of statewide goals for water quality and stream biotic integrity.

中文翻译：

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施肥对北佛罗里达州两个森林流域的养分输出和河流生物群的影响可以忽略不计

摘要 受管理的松林覆盖了美国东南部近 130,000 平方公里的土地，对该地区的经济和生态可持续性具有重要意义。这些林分通常施肥两次——在建立时和轮作中期——以在 25 年轮作期间提高木材产量。在佛罗里达州，最佳管理实践 (BMP) 限制了肥料施用率，并要求特殊管理区 (SMZ) 以减少养分污染。佛罗里达州最近对河流和湖泊采用的数值养分标准 (NNC) 引起了人们的担忧，即森林施肥，即使符合 BMP，也可能导致养分负荷过多和河流生态条件恶化，尤其是直接在施肥之后。我们研究了两个中等规模流域（21 和 34 平方公里，分别）在受精后以佛罗里达州北部的火炬松（Pinus taeda）种植园为主。在 54 个月的时间里，我们监测了河流排放、氮（TN、TKN、NO3-N、NH4-N）和磷（TP、orthoP）以及河流生物群（底栖大型无脊椎动物、浮游植物叶绿素 a、附生生物和维管植物）在流域规模施肥之前和之后。我们将四年的计划施肥浓缩为一年，从而导致养分投入比通常情况大得多。由于流量变化强烈控制养分浓度，我们评估了施肥前后浓度-排放 (CQ) 关系，该关系保持不变。N 和 P 的年度大量出口也保持不变，表明景观保留了额外的负荷。同样地，我们没有观察到生物指标的系统变化。这些结果表明，以 BMP 比率进行森林施肥不太可能增加河流养分输出，支持东南沿海平原的施肥松林保护全州水质和河流生物完整性目标的论点。