A tree stump in New Zealand is very much alive, thanks to an interconnected root system that benefits both the stump and its neighboring trees. Scientists say this unusual symbiotic arrangement could change our very conception of what it means to be a tree. We tend to think of trees as individuals, but the roots of some species fuse together to allow the sharing of resources, such as water, carbon, mineral nutrients, and microorganisms. Leuzinger and Bader stumbled upon the stump while out for a hike. The woody stub caught their eye because callus tissue could be seen growing over...