Subject
- Forest soils -- Oregon -- H.J. Andrews Experimental Forest1
- Forest soils -- Pennsylvania -- Bousson Experimental Forest1
- Humus -- Oregon -- H.J. Andrews Experimental Forest -- Analysis1
- Humus -- Pennsylvania -- Bousson Experimental Forest -- Analysis1
- Soil ecology -- Oregon -- H.J. Andrews Experimental Forest1
- Soil ecology -- Pennsylvania -- Bousson Experimental Forest1