Understanding the role of land use type and topographic features in shaping wildfire regimes received much attention because of the intensification of wildfire activities. The intensifying wildfires in the western United States are a great concern both for the environment and society. We investigate the patterns of wildfire occurrence in the western United States at the landscape level by using 118 wildfires with areas greater than 405 ha in the study year of 2018. The selection ratios were calculated to measure fire preference with regard to land cover type, slope, and aspect. The results suggest that grasslands, steeper slopes, and south-facing aspects were more susceptible to wildfires in the western United States. Additionally, there were regional variations in wildfire susceptibility in Washington, Oregon, and California. The most wildfire-prone land cover type in Washington was mixed forests, whereas that in Oregon and California was grassland. The findings of this study improve the understanding of the role of land use changes and topographic features in shaping wildfire patterns in the western United States, providing insights for managing wildfire risks for forest management strategies at the landscape level.

In the Gulf of Mexico coastal region, prescribed fire has been increasingly used as a management tool to restore declining native ecosystems, but it also increases the threat posed by biological invasion, since the treated sites are more susceptible to invasive species such as Chinese tallow (Triadica sebifera). We chose Mississippi Sandhill Crane National Wildlife Refuge (MSCNWR), a fire-managed landscape, to examine the potential effect of prescribed fire and landscape/community features on tallow invasion and spread. We took a complete survey of roadways and fire lines for tallow and measured a systematic sample of 144 10 × 3 m² rectangular plots along two selected roadways and a simple random sample of 56 0.04-ha circular plots across burn units. We used pair correlation function for marked point pattern data, zero-inflated negative binomial models for count data, as well as multivariate Hotelling’s T² test, to analyze the effect of prescribed fire and landscape/community characteristics on tallow invasion and spread along habitat edges and into interiors. Our results show that tallow spread along habitat edges and into interiors in a spatially clustered pattern. Tallow invasion risk decreases with the distance to seed trees and shrub coverage, and with the time since last fire if seed trees are outside the effective seed dispersal range (~300 m), but increases with the time since last fire if seed trees are within the effective seed dispersal range. Tallow seedling (≤2 years old) densities increase with the time since last fire and with increasing overstory tree basal area, but decrease with the distance to seed trees. Tallow-invaded interior plots have significantly shorter mean fire return intervals (2.7 years), lower shrub coverage (8.6%), and are closer to edges (20.3 m) than non-invaded plots (4.3 years, 18.4%, 167.6 m, respectively).