Douglas Campbell

Undisturbed grasslands accumulate a lot of organic matter in soils, some from leaf litter, but also from root and rhizome material.  So the lignin content of the leaves is only part of the story.  Relative lignin content in leaves goes up in the late season in part b/c carbohydrates and nitrogen compounds are translocated out to seeds, rhizomes, or both.

I do not understand the y axis on your graphs, although the patterns look reasonable.
(ps I worked on related  issues years ago).

Off track, but I used to live 2 km from a cold-war relict, former CBC/RadioCanada shortwave station.
We got CBC International on old copper wired telephones as a background,  and some people had it coming out of their copper plumbed sinks.
No lie.

In Nova Scotia north facing slopes are preferred for apples to lower risk of early blooming and then frost damage. Later blossoming is safer.

Hi
I just  helped with a similar upgrade at latitude 46.
Where are you?
We left the existing roof panels,
and added a ground mount array at a steeper angle for season extension and snow shedding.
Your roof pitch looks quite shallow for anything except summer; unless you are equatorial.
Bifacials will not give much extra benefit on a roof; little light from below.
We used an EG4 12kpv all in one, with 2 mppt.
Each mppt can accept 2 identical input strings.  The 2 mppt do not have to be balanced.
We needed the EG4 12kpv for cold weather; there are other options for above freezing.

I also agree that tree trimming is a place to start.
cheers Doug

I have a similar battle;  acidic clay, to which I foolishly added abundant, partially marine, compost, neutralized the pH, now have chlorotic blueberry bushes.
I am trying elemental sulfur which slowly lowers pH; limited success so far.

Younger, smaller trunks amd branches have alot more bark, which is metabolically active and higher in N.

Technical comments:
Wood is a composite material made from cellulose (long chains of
glucose, pure carbohydrate).  The cellulose fibrils are cross linked by a mesh of lignin.
The cellulose:lignin ratio is major determinant of decomposition rate.
Celery: no lignin
Poplar: some lignin
Oak: lots of lignin.
The lignin itself is complex and diverse across species; a swarm of cyclic structures that are cross linked.
The lignin rings are derived from amino acid metabolism but the N groups are mostly removed during lignin synthesis.

There are other carbohydrates, resins etc depending upon species.
During decomposition the most resistant fractions of the lignins transform to humins and humic acids which are stable and accumulate as soil carbon.
The carbohydrate fractions turn over to CO2 faster.
There is very little N in most wood, but some nitrogen fixing bacteria and directly or indirectly access  the wood carbohydrates to fuel fixation of N2 to available N compounds.
So adding woodchips will tend to cause a temporary drop  in available N as decomposers take up soil N to build biomass to breakdown the wood.
Others have answered the alkalinization question.
cheers Doug

We used to freeze it after pressing. If stored, unsterilized, at room temperature it will start fermenting within days.

Hi  you are in BC; do you get freeze/thaw?
If so, water b/t the retaining wall and the facer stones will push the facing stones off.
There might have been a cap to divert water from flowing down through?
I have limited experience but have seen it done poorly many times. cheers Douug

Note: yeast are fungi, not bacteria.