Hi, I am not sure if this belongs under Humus sapiens, please move if this subject is too broad. Also sorry for being absent for about a year. I now have energy and time to work with Humus sapiens and other stuff.
I have three scientific measurement systems on mind that could be made into “DIY kits”. With these measurements, it is possible to understand pretty much what is going on with trees.
The first one is soil CO2 flux chamber, which is now working, but not yet v1.0 I think. CO2 flux chamber is used to measure how much CO2 soil is emitting to the atmosphere. It also pretty much tells how much (microbial) activity there is in soil. The measurement system is portable.
The second one is a sapflow measurement system. It is used to measure how much water trees are transporting in the stem (tree trunk). The flow rate is directly linked to photosynthesis of the plant, and can also be used to measure the drought stress of trees. The system is simple to build and understand, but it requires permanent installation to the trees, including drilling two holes to the tree (5mm radius, 10 cm in length). The measurement itself requires a couple of days of constant current (about 1W) to make sense.
The third system would be transpiration (evaporation of water through the plant) measurement using IR thermography. I did my master’s thesis about this (unfortunately in Finnish). It’s a simple system that allows measuring transpiration from a single leaf. This measurement requires IR thermometer, and an artificial leaf that heated (this is the DIY part). Also clear instructions how to do the measurements are needed (I can do it).
The CO2 soil flux chamber can be modified to measure also how much tree stem is producing CO2. This is for example related to tree growth (formation of wood). In addition, the same chamber system can be modified to measure photosynthesis from branches. To make it state-of-the-art, a small pump with constant air flow would be preferred.
With the tree measurement systems, it is possible to measure the carbon cycling in the forests, and even get a measurement-based (quantitative) estimation of how large carbon sink a forest is. Canopy (leaves) is an interface between living and non-living world. It is also where (almost) all the energy used in nature is originating. Soil is another interface between living (roots and microbes) and non-living (dead organic material, mineral soil) world. The water transport acts as a link between soil and the canopy of the trees. In fact, the water tension acts as a kind of neural system for trees: the roots sense what is happening in the canopy.
I can provide technical details and support for the measurements and data analysis starting from October 2019.