Abstract

Burn severity, commonly assessed as the amount of fuel consumed during fire, is an indicator of postfire sediment yield and erosion. This study examined the effect of burn severity on sediment and nutrient response in three different fire-adapted forest types of the Southeast. Soil and litter samples were experimentally burned to achieve increasing levels of fuel consumption. Simulated rainfall was applied to burned litter samples collected from pine, hardwood, and mixed hardwood-pine forests in the Clemson Experimental Forest. Runoff and leachate samples were collected and analyzed for sediment yield (kilograms per hectare) and total suspended solids (grams per liter); both runoff and leachate samples were analyzed for ammonium (NH₄^–), nitrate (NO₃^–), and orthophosphate (PO₄^3–). Sediment yield and total suspended solids increased at only the highest burn severity treatment in all three forest types, with pine litter samples yielding significantly greater sediment in surface runoff than both mixed and hardwood samples. Burn treatment did not readily affect soluble nutrient concentrations in either runoff or leachate, but the data suggest that high-severity burning increases the availability of PO₄^3– bound to sediment. This study suggests that high-severity burn patches function as sediment sources, but overall sediment and nutrient response to burning was minimal.

Study Implications

This study suggests that low-to-moderate burn severity, in terms of litter removal, is not an important indicator of sediment and nutrient exports from southeastern forests; precipitation in the immediate aftermath of fire (<48 hours) is not an effective transport mechanism for biologically available macronutrients; and that even at the highest burn severity treatment, sediment yield was relatively low.

中文翻译：

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模拟降雨对南方森林沉积物和养分出口的烧伤严重性影响

摘要

燃烧严重程度通常被评估为火灾中消耗的燃料量，是火灾后沉积物产量和侵蚀的指标。这项研究考察了东南部三种不同的适应火灾的森林类型，燃烧强度对沉积物和养分响应的影响。实验对土壤和垃圾样本进行了燃烧，以提高燃料消耗水平。模拟降雨应用于从克莱姆森实验林中的松树，硬木和混合硬木-松树森林收集的烧掉的垃圾样品。收集径流和渗滤液样品，并分析其沉积物产量（千克/公顷）和总悬浮固体（克/升）；既径流和渗滤液分析样品的铵（NH ₄ ^- ），硝酸根（NO ₃ ^-）和正磷酸盐（PO ₄ ^3–）。在所有三种森林类型中，只有在最高烧伤严重程度的处理下，沉积物的产量和总悬浮物才会增加，与混合和硬木样品相比，松树凋落物样品在地表径流中产生的沉积物要多得多。焚烧处理不易影响径流或渗滤液中的可溶性营养物浓度，但数据表明，高强度焚烧可增加与沉积物结合的PO ₄ ³的利用率。这项研究表明，高强度的烧伤斑块是泥沙的来源，但是泥沙和养分对燃烧的总体响应却很小。

研究意义

这项研究表明，就清除凋落物而言，中低度烧伤严重程度并不是东南部森林沉积物和养分输出的重要指标。火灾后立即发生（<48小时）的降水不是生物上可利用的大量营养素的有效运输机制；即使在最高烧伤严重程度的处理下，沉积物的产量也相对较低。