Yes, there are several more and less important factors related to plant density that will definitely influence photosynthesis in both the short and long terms:
- Shade (light availability) will be less or higher
- Plant competition for soil resources: nutrients, water,
- Soil mineral exhausting,
- Temperature (soil and canopy)
- Evapotranspiration
- Root density... among others.
Have a look at these papers.
If you need a specific research paper and you know the DOI or have its reference, send that info and I can try to find the PDF for you.