What causes fir trees to turn Brown?

Aging, compacted soil, compromised roots, drought, needle-casting disease, over-watering and winter injury are reasons why fir tree (Abies spp, Pseudotsuga spp) needles turn brown before dropping and dying. Compaction, drought, off-kilter power of hydrogen (pH), underground obstructions and pests and water-logging can be corrected with aeration, modified watering and soil analysis. Winter injury demands careful cuts into dry wood on dry days while needle-casting disease requires pruning, sanitation and treatments with fungicides.