A phosphorus threshold for mycoheterotrophic plants in tropical forests.
The majority of terrestrial plants associate with arbuscular mycorrhizal (AM) fungi, which typically facilitate the uptake of limiting mineral nutrients by plants in exchange for plant carbon. However, hundreds of non-photosynthetic plant species-mycoheterotrophs-depend entirely on AM fungi for carbon as well as mineral nutrition. Mycoheterotrophs can provide insight into the operation and regulation of AM fungal relationships, but little is known about the factors, fungal or otherwise, that affect mycoheterotroph abundance and distribution. In a lowland tropical forest in Panama, we conducted the first systematic investigation into the influence of abiotic factors on the abundance and distribution of mycoheterotrophs, to ask whether the availability of nitrogen and phosphorus altered the occurrence of mycoheterotrophs and their AM fungal partners. Across a natural fertility gradient spanning the isthmus of Panama, and also in a long-term nutrient-addition experiment, mycoheterotrophs were entirely absent when soil exchangeable phosphate concentrations exceeded 2 mg P kg-1Experimental phosphorus addition reduced the abundance of AM fungi, and also reduced the abundance of the specific AM fungal taxa required by the mycoheterotrophs, suggesting that the phosphorus sensitivity of mycoheterotrophs is underpinned by the phosphorus sensitivity of their AM fungal hosts. The soil phosphorus concentration of 2 mg P kg-1also corresponds to a marked shift in tree community composition and soil phosphatase activity across the fertility gradient, suggesting that our findings have broad ecological significance.
Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK merlinsheldrake@gmail.com.|Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Republic of Panama.
Merlin
0000-0003-4888-9972
M
Sheldrake
Center for Environmental and Climate Research, Lund University, 22362 Lund, Sweden.
Nicholas P
NP
Rosenstock
Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Republic of Panama.|Department of Biological Sciences, Northern Arizona University, PO BOX 5640, Flagstaff, AZ 86011, USA.
Daniel
D
Revillini
Department of Biology, Lund University, 22362 Lund, Sweden.
Pål Axel
PA
Olsson
Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Republic of Panama.
S Joseph
SJ
Wright
Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Republic of Panama.
Benjamin L
BL
Turner
D065928:Forests; D038821:Mycorrhizae; D010176:Panama; D010758:Phosphorus / Q000032:analysis*; D018517:Plant Roots; D010944:Plants / Q000382:microbiology*; D012987:Soil / Q000737:chemistry; D014329:Tropical Climate
D012987:Soil; D010758:Phosphorus
arbuscular mycorrhizal fungi; epiparisitism; mycoheterotroph; phosphorus; tropical forest