Complex sentence: Photobiont will become less dependent of fungal nutrient supply when nitrogen deposition increases as it will be able to access its own nitrogen and it will stimulate photobiont, causing it to build up, resulting in the increase in photosynthesis which increases carbon input.
Split into simpler sentences: Photobiont will become less dependent of fungal nutrient supply when nitrogen deposition increases as it will be able to access its own nitrogen and it will stimulate photobiont, causing it to build up. Thus, resulting in the increase in photosynthesis which increases carbon input.