ECOTONE
| Date | Clue |
|---|---|
| 2021-04-07 | Transitional region between biomes |
| 2019-12-26 | Transitional zone between two biomes |
| 2014-04-13 | Transition area from deciduous to evergreen, e.g. |
| 2014-04-02 | Environmental transition area |
| 2013-11-26 | Transitional zone between plant communities |
| 2011-07-09 | Environmental transition area |
| 2009-01-10 | Area between forest and prairie, e.g. |
| 2007-02-25 | Transitional land zone |
| 1996-05-11 | Transition zone between plant communities |