BayCEER Workshop 2026

Fungal Carbon Uptake in Tropical Woody Seedlings

Tropical forests harbour the majority of Earth´s biodiversity and provide important ecosystem services. Seedling regeneration remains a critical bottleneck for the future of these forests. In the dark forest understory, which receives less than 1 % of sunlight, carbon uptake through photosynthesis is low, and seedlings are severely carbon limited. Under these conditions, the ability for additional carbon gain, should provide a significant ecological advantage. 

Some species have evolved the ability to take up additional carbon from mycorrhizal networks, a nutritional strategy known as partial mycoheterotrophy. In tropical lowland forests, associations with arbuscular mycorrhizae (AM) are dominant, and stable isotope analyses have recently provided first evidence for this nutritional mode in AM associated tropical tree species. In this study, we explore additional evidence to corroborate carbon uptake through partial mycoheterotrophy in tropical seedlings. 

We test whether seedlings of the candidate tropical woody species Acalypha macrostachya use this nutritional strategy by combining: (i) isotope analysis (¹³C and ¹⁸O) to detect fungal-derived carbon, (ii) microscopic assessment of AM colonisation and the formation of hyphal coils (Paris-type), a morphological variant considered to be a prerequisite partial mycoheterotrophy, and (iii) DNA-based identification of root fungal communities, comparing our target species with co-occurring fully autotrophic reference seedlings.

Preliminary results show that A. macrostachya hosts a significantly higher proportion of Paris-type AM than reference seedlings and exhibits a carbon signature consistent with fungal carbon uptake. Our findings underline partial mycoheterotrophy as an overlooked mechanism of seedling establishment in tropical forests.