Rich said:
For every region / part of the world it will vary, so something more local is always good depending on where someone lives. So I have those kinds of books for NE N America I can recommend but they are more region-specific.
-If the person is asking in a much more general way for a book on plant ecology, I would just go to a decent botany textbook and there is usually a chapter on ecology and ecosystems.
Here are two that are free online:
https://prod-cat-files.macmillan.cloud/MediaResources/instructorcatalog/legacy/BFWCatalog/uploadedFiles/Content/BFW/Product/About/Raven%208e%20Ch32.pdf
https://prod-cat-files.macmillan.cloud/MediaResources/instructorcatalog/legacy/BFWCatalog/uploadedFiles/Content/BFWHS/Correlations/Raven%208e%20Ch31(1).pdf