I believe Leaf Area Index of the arable cum forest crop combination and the complementary nutrient use of the crops are the two I can think of. The former is relevant with respect to shading and accessibility to solar radiation for photosynthesis, while the latter has to do with contributions of nutrients such as N from legumes, and uptake of the N from a N-consuming crop such as corn-if a legume-Cereal Agro-forestry system is being mapped as an example.
Agroforestry suitability analysis based upon nutrient availability mapping: a GIS based suitability mapping
Abstract: Agroforestry has drawn the attention of researchers due to its capacity to reduce the poverty and land degradation, improve food security and mitigate the climate change. However, the progress in promoting agroforestry is held back due to the lack of reliable data sets and appropriate tools to accurately map and to have an adequate decision making system for agroforestry modules.Agroforestry suitability being one special form of land suitability is very pertinent to study in the
current times when there is tremendous pressure on the land as it is a limited commodity. The study aims for applying the geo-spatial tools towards visualizing various soil and environmental data to reveal the trends and interrelationships and to achieve a nutrient availability and agroforestry suitability map. Using weight matrix and ranks, individual maps were developed in ArcGIS 10.1 platform to generate nutrient availability map, which was later used to develop agroforestry
suitability map. Watersheds were delineated using DEM in some part of the study area and were evaluated for prioritizing it and agroforestry suitability of the watersheds were also done as per the schematic flowchart. Agroforestry suitability regions were delineated based upon the weight and ranks by integrated mapping. The total open area was identified 42.4% out of which 21.6% area was found to have high suitability towards agroforestry. Within the watersheds, 22 village points were generated for creating buffers, which were further evaluated showing its proximity to high suitable agroforestry sites thus generating tremendous opportunity to the villagers to carry out agroforestr yprojects locally. This research shows the capability of remote sensing in studying agroforestry practices and in estimating the prominent factors for its optimal productivity. The ongoing agroforestry projects can be potentially diverted in the areas of high suitability as an extension. The
use of ancillary data in GIS domain can have enormous ability to map the land for the benefit of rural people even up to the village level. Source ;AIMS Agriculture and Food, 2(2): 201-220, DOI: 10.3934/agrfood.2017.2.201..P_DF enclosed for further reading..
GIS-based land-use suitability analysis: a critical overview byJacek Malczewski,
Progress in Planning, Volume 62, Issue 1, July 2004, Pages 1-2
Hy Firoz, i think Density of canopy is very important, as well forest change or deforestation. You can learn and download (GIS information) for any country, from this site.