Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK.
Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Panama.
New Phytol. 2017 Apr;214(1):455-467. doi: 10.1111/nph.14384. Epub 2017 Jan 2.
Tropical forest productivity is sustained by the cycling of nutrients through decomposing organic matter. Arbuscular mycorrhizal (AM) fungi play a key role in the nutrition of tropical trees, yet there has been little experimental investigation into the role of AM fungi in nutrient cycling via decomposing organic material in tropical forests. We evaluated the responses of AM fungi in a long-term leaf litter addition and removal experiment in a tropical forest in Panama. We described AM fungal communities using 454-pyrosequencing, quantified the proportion of root length colonised by AM fungi using microscopy, and estimated AM fungal biomass using a lipid biomarker. AM fungal community composition was altered by litter removal but not litter addition. Root colonisation was substantially greater in the superficial organic layer compared with the mineral soil. Overall colonisation was lower in the litter removal treatment, which lacked an organic layer. There was no effect of litter manipulation on the concentration of the AM fungal lipid biomarker in the mineral soil. We hypothesise that reductions in organic matter brought about by litter removal may lead to AM fungi obtaining nutrients from recalcitrant organic or mineral sources in the soil, besides increasing fungal competition for progressively limited resources.
热带森林的生产力依赖于分解有机物中的养分循环。丛枝菌根（AM）真菌在热带树木的营养中起着关键作用，但对 AM 真菌在热带森林分解有机物质过程中的养分循环中的作用的实验研究很少。我们评估了在巴拿马热带森林中进行的长期叶凋落物添加和去除实验中 AM 真菌的反应。我们使用 454 焦磷酸测序描述了 AM 真菌群落，使用显微镜量化了 AM 真菌根长的定殖比例，并使用脂质生物标志物估计了 AM 真菌生物量。凋落物去除改变了 AM 真菌群落组成，但凋落物添加没有改变。与矿物土壤相比，在浅层有机层中，根的定殖量要大得多。在缺少有机层的凋落物去除处理中，总体定殖量较低。凋落物处理对矿物土壤中 AM 真菌脂质生物标志物的浓度没有影响。我们假设，凋落物去除导致的有机物减少可能导致 AM 真菌从土壤中难以分解的有机或矿物源获取营养物质，除了增加真菌对逐渐有限资源的竞争。
