Evaluating Landscape Metrics as Predictors of Area Burned by Wildfire and Monitoring Landscape Level Change in the Interior Douglas-Fir Zone in British Columbia

The Interior Douglas-fir zone of British Columbia’s Cariboo Region evolved alongside wildfire through millennia of repeat exposure. Resulting from these interactions were fire adapted species and landscape configurations that supported low to moderate severity wildfires. Removing the dominant disturbance agent of these dry forest ecosystems through systematic fire suppression has resulted in unforeseen repercussions. Presently, forests of the Interior Douglas-fir zone hold the potential for higher severity wildfire posing an increased threat to human life. This project was conducted to evaluate landscape metrics as predictors of area burned within the Interior Douglas-fir zone of the Cariboo Region. Six landscape metrics pertaining to the composition and configuration of landscape patches were calculated within 2500 hectare sampling cells. Additional work was conducted to quantify changing landscape metrics between 1985 and 2016. Key to this report are annual land cover maps generated following the Virtual Land Cover Engine framework applied to Landsat-5 TM and Landsat-7 ETM+ imagery. Results indicate that none of the landscape metrics involved in this project are effective predictors of area burned. Trend analysis from 1985 to 2016 concluded that several landscape metrics exhibited significant monotonic trends. The number of patches, landscape shape index, and Shannon’s diversity index were found to be increasing while mean patch area, and proportion of like adjacency were found to be decreasing. Additionally, no significant change in the area burned was observed. These results suggest that another agent, likely timber harvesting and climate change, are driving trends in landscape metrics. Overall, landscapes are becoming more heterogeneous. This does not necessarily translate to decreasing wildfire severity or size.

不列颠哥伦比亚省卡里布地区的内陆道格拉斯冷杉（Interior Douglas-fir）生态带，历经数千年的反复野火干扰，与野火协同演化。二者的相互作用孕育了适应野火的物种与景观格局，支撑了低至中等烈度的野火活动。通过系统性的野火抑制移除这类干旱森林生态系统的主导干扰因子，引发了难以预料的连锁反应。如今，内陆道格拉斯冷杉生态带的森林面临更高烈度野火的风险，对人类生命构成了愈发严峻的威胁。

本研究旨在评估景观指数（landscape metrics）作为卡里布地区内陆道格拉斯冷杉生态带野火过火面积预测因子的有效性。研究团队在2500公顷的样地单元内，计算了6项与景观斑块组成及格局相关的景观指数。此外，研究还量化了1985年至2016年间景观指数的变化情况。

本报告的核心数据是基于虚拟土地覆盖引擎（Virtual Land Cover Engine）框架，利用陆地卫星5号专题制图仪（Landsat-5 TM）与陆地卫星7号增强型专题制图仪（Landsat-7 ETM+）影像生成的年度土地覆盖图。

研究结果显示，本研究涉及的所有景观指数均无法有效预测野火过火面积。1985年至2016年的趋势分析表明，多项景观指数呈现出显著的单调变化趋势：斑块数量、景观形状指数以及香农多样性指数（Shannon's Diversity Index）呈上升趋势，而平均斑块面积与同类邻接比例（Proportion of Like Adjacency）则呈下降趋势。此外，研究未观测到野火过火面积存在显著变化。

上述结果表明，另有其他驱动因子——大概率为木材采伐与气候变化——正在影响景观指数的变化趋势。整体而言，该区域的景观正愈发趋于异质化，但这并不必然意味着野火烈度与过火规模会随之下降。