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首页> 外文期刊>Remote Sensing of Environment: An Interdisciplinary Journal >Dynamics of national forests assessed using the Landsat record: Case studies in eastern United States
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Dynamics of national forests assessed using the Landsat record: Case studies in eastern United States

机译：使用Landsat记录评估的国家森林动态：美国东部的案例研究

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The national forests (NFs) in the United States are protected areas managed for multiple purposes, and therefore are subject to both natural and anthropogenic disturbances. Monitoring forest changes arising from such disturbances and the post-disturbance recovery processes is essential for assessing the conditions of the NFs and the effectiveness of management approaches. In this study, we used time series stacks of Landsat images (LTSS) to evaluate the dynamics of seven NFs in eastern United States, including the De Soto NF the Talladega NF the Francis Marion NF and the Uwharrie NF in southeastern U.S., and the Chequamegon NF, the Hiawatha NF, and the Superior NF in northern U.S. Each LTSS consisted of 12-14 Landsat images acquired for the same location, spanning from 1984 to 2006 with a nominal interval of one image every 2 years. Each LTSS was analyzed using a vegetation change tracker (VCT) algorithm to map forest disturbance. Accuracy assessments of the derived disturbance maps revealed that they had overall accuracy values of about 80%, with most of the disturbance classes having user's accuracies ranging from 70% to 95%. The producer's accuracies were generally lower, with the majority being in the range between 50% and 70%. While this may suggest that the disturbance maps could slightly underestimate disturbances, a more detailed assessment of the omission errors revealed that the majority of the disagreements were due to minor disturbances like thinning or storm damages that were identified by the image analysts but were not captured by the VCT algorithm. The derived disturbance year maps revealed that while each of the seven NFs consisted of 90% or more forest land, significant portions of the forests were disturbed since 1984. Mapped disturbances accounted for about 30%-45% of total land area in the four NFs in southeastern U.S. and about 10%-20% in the three NFs in northern U.S. The disturbance rates were generally higher in the buffer zones surrounding each NF, and varied considerably over time. The time series approach employed in this study represents a new approach for monitoring forest resources using the Landsat or similar satellite data records. The disturbance products derived using this approach were spatially explicit and contained much more temporal details than conventional bi-temporal change products, and likely will be found more useful by many users including ecologists and resources managers. The high disturbance rates found in the southeastern U.S. suggest that this region may have a more significant role in modulating the atmospheric carbon budget than currently recognized.
机译：美国的国家森林（NFs）是出于多种目的而管理的保护区，因此会受到自然和人为干扰。监测由此类干扰和扰动后恢复过程引起的森林变化对于评估自然保护区的状况和管理方法的有效性至关重要。在这项研究中，我们使用Landsat图像（LTSS）的时间序列堆栈来评估美国东部的七个NF的动力学，包括美国东南部的De Soto NF，Talladega NF，Francis Marion NF和Uwharrie NF以及Chequamegon美国北部的NF，Hiawatha NF和上级NF每个LTSS包含从同一位置获取的12-14张Landsat图像，范围从1984年到2006年，标称间隔为每2年一张图像。使用植被变化跟踪器（VCT）算法对每个LTSS进行了分析，以绘制森林干扰图。对派生的干扰图的准确性评估表明，它们的总体准确性值约为80％，大多数干扰类别的用户准确度范围为70％至95％。生产者的准确性通常较低，大多数介于50％和70％之间。尽管这可能表明干扰图可能会低估干扰，但对遗漏错误的更详细评估显示，大多数分歧是由图像分析人员识别但未被捕获的细微干扰（如细化或风暴破坏）引起的。 VCT算法。导出的扰动年图显示，尽管七个自然保护区中的每个森林都包含90％或更多的林地，但自1984年以来，大部分森林受到了扰动。映射的扰动约占四个自然保护区总土地面积的30％-45％。在美国东南部，在美国北部的三个NF中约占10％-20％。在每个NF周围的缓冲区中，干扰率通常较高，并且随时间变化很大。本研究中使用的时间序列方法代表了一种使用Landsat或类似卫星数据记录监视森林资源的新方法。使用这种方法得出的干扰产物在空间上是明确的，并且比常规的双向变化产物包含更多的时间细节，并且可能会被包括生态学家和资源经理在内的许多用户发现有用。在美国东南部发现的高干扰率表明，该地区在调节大气碳收支方面可能比目前公认的更为重要。

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