my monkey puzzle tree

Question

My tree is 40 years old and has always had very dark green leaves, about 4 years ago I had the ground beneath the tree covered with a membrane and gravel. The leaves are now a very light green and some lower braces are brown. Do you think it will help the tree to recover if I remove the gravel and the membrane as I think it may not be getting sufficient water. A. Cooper

Answer 1

If the membrane is not permeable then it is especially important to remove it. If it is permeable and water can penetrate, then try stepping up the watering in the entire root zone beneath the foliar canopy (dripline) and beyond. Apply a water soluble complete fertilizer.

But there is another possibility, that of a pest infestation. Araucaria species are subject to scale insects and mealybugs. They may become more susceptible if stressed from something like water deficit due to the change of conditions and soil covering.
For a 40 yo tree you may need to have an assessment and diagnosis from a certified arborist, plant health care specialist.

Pests and disorders of Araucaria spp:

Araucaria scale (similar to Cottony cushion scale)
Armored scales
Black araucaria scale
Dictyospermum scale
Mealybugs
Golden mealybug

Environmental disorders:
Mineral deficiencies
Nutrient and mineral excesses
Poor water management