“Redbud Tree,” a highlight of Mark Knopfler’s eighth solo album, could’ve been written 100 years ago. But given our ecocrisis, this tree-hugging folk gem, embossed with a shimmering fingerpicked Strat, feels cannily modern. Knopfler’s sueded voice has changed little since his 1980s heyday, and his elegant electric-guitar work sounds better than ever. The 20 songs, most top-shelf, are a textbook of folk styles, from Irish ballads (“Kingdom of Gold”) and country-flavored weepers (“Seattle”) to slide-driven blues (“Don’t Forget Your Hat”) and Tin Pan Alley nostalgia (“Radio City Serenade”). On the title track, he shows offhis acoustic playing, a folk-rock vet returning to the source.