Canadian Forest Service (Pacific Forestry Centre), Natural Resources Canada, 506 West Burnside Rd., Victoria, BC V8Z 1M5, Canada.
Environ Monit Assess. 2010 Nov;170(1-4):417-33. doi: 10.1007/s10661-009-1243-8. Epub 2009 Nov 12.
Many countries undertake a national forest inventory to enable statistically valid monitoring in support of national and international reporting of forest conditions and change. Canada's National Forest Inventory (NFI) program is designed to operate on a 10-year remeasurement cycle, with an interim report produced at the 5-year mid-point. The NFI is a sample-based inventory, with approximately 18,850 2×2-km photo plots across the country, distributed on a 20×20-km grid of sample points; these photo plots are the primary data source for the NFI. Capacity to provide annual monitoring information is required to keep policy and decision makers apprised of current forest conditions. In this study, we implemented a multistage monitoring framework and used a Moderate Resolution Imaging Spectroradiometer (MODIS) change product to successfully identify 78% of the changes in forest cover area that were captured with a Landsat change detection approach. Of the NFI photo plots that were identified by both the Landsat and MODIS approaches as having changes in forest cover, the proportion of change area within the plots was similar (R2=0.78). Approximately 70% of the Landsat-derived change events occupied less than 40% of a single MODIS pixel, and more than 90% of the change events of this size were successfully detected with the MODIS product. Finally, MODIS estimates of the proportion of forest cover change at the NFI photo plot level were comparable to change estimates for the ecoregions as a whole (R2=0.95). High-temporal, low-spatial resolution imagery such as MODIS, in combination with other remotely sensed data sources, can provide information on disturbance events within a national forest inventory remeasurement cycle, thereby satisfying the interim information needs of policy and decision makers as well as the requirements of national and international reporting commitments.
许多国家开展国家森林清查工作，以支持对森林状况和变化进行具有统计效力的监测，从而进行国家和国际报告。加拿大国家森林清查（NFI）计划旨在以 10 年复测周期运行，在 5 年中期制作一份中期报告。NFI 是一个基于样本的清查，全国约有 18850 个 2x2 公里的相片样地，分布在 20x20 公里的样本点网格上；这些相片样地是 NFI 的主要数据源。为了向政策制定者和决策者提供年度监测信息，以了解当前的森林状况，需要具备提供年度监测信息的能力。在这项研究中，我们实施了一个多阶段监测框架，并使用中分辨率成像光谱仪（MODIS）变化产品，成功地识别了 78%的森林覆盖面积变化，这些变化是通过陆地卫星变化检测方法捕捉到的。在被陆地卫星和 MODIS 方法都识别出森林覆盖变化的 NFI 相片样地中，样地内变化面积的比例相似（R2=0.78）。大约 70%的陆地卫星衍生的变化事件占据不到一个 MODIS 像素的 40%，而大小为这种变化事件的 90%以上都可以用 MODIS 产品成功检测到。最后，MODIS 对 NFI 相片样地层面森林覆盖变化比例的估计与整个生态区的变化估计相当（R2=0.95）。高时间、低空间分辨率的图像，如 MODIS，与其他遥感数据源相结合，可以提供国家森林清查复测周期内的干扰事件信息，从而满足政策制定者和决策者的中期信息需求，以及国家和国际报告承诺的要求。
