Lovelock Catherine E, Andersen Kelly, Morton Joseph B
Smithsonian Environmental Research Center, PO Box 28, Edgewater, MD 21037, USA.
Oecologia. 2003 Apr;135(2):268-79. doi: 10.1007/s00442-002-1166-3. Epub 2003 Feb 13.
Arbuscular mycorrhizal (AM) fungi are mutualists with plant roots that are proposed to enhance plant community diversity. Models indicate that AM fungal communities could maintain plant diversity in forests if functionally different communities are spatially separated. In this study we assess the spatial and temporal distribution of the AM fungal community in a wet tropical rainforest in Costa Rica. We test whether distinct fungal communities correlate with variation in tree life history characteristics, with host tree species, and the relative importance of soil type, seasonality and rainfall. Host tree species differ in their associated AM fungal communities, but differences in the AM community between hosts could not be generalized over life history groupings of hosts. Changes in the relative abundance of a few common AM fungal species were the cause of differences in AM fungal communities for different host tree species instead of differences in the presence and absence of AM fungal species. Thus, AM fungal communities are spatially distinguishable in the forest, even though all species are widespread. Soil fertility ranging between 5 and 9 Mg/ha phosphorus did not affect composition of AM fungal communities, although sporulation was more abundant in lower fertility soils. Sampling soils over seasons revealed that some AM fungal species sporulate profusely in the dry season compared to the rainy season. On one host tree species sampled at two sites with vastly different rainfall, relative abundance of spores from Acaulospora was lower and that of Glomus was relatively higher at the site with lower and more seasonal rainfall.
丛枝菌根（AM）真菌与植物根系形成共生关系，有人认为它们能增加植物群落的多样性。模型表明，如果功能不同的AM真菌群落能在空间上分离，那么它们就能维持森林中的植物多样性。在本研究中，我们评估了哥斯达黎加一片湿润热带雨林中AM真菌群落的时空分布。我们测试了不同的真菌群落是否与树木生活史特征的变化、寄主树种以及土壤类型、季节性和降雨的相对重要性相关。寄主树种的AM真菌群落各不相同，但寄主之间AM群落的差异不能推广到寄主的生活史分组上。少数常见AM真菌物种相对丰度的变化是不同寄主树种AM真菌群落差异的原因，而不是AM真菌物种有无的差异。因此，即使所有物种都广泛分布，AM真菌群落在森林中在空间上也是可区分的。土壤磷含量在5至9毫克/公顷之间的土壤肥力并未影响AM真菌群落的组成，尽管在肥力较低的土壤中孢子形成更为丰富。对不同季节的土壤进行采样发现，与雨季相比，一些AM真菌物种在旱季大量形成孢子。在两个降雨差异极大的地点对一种寄主树种进行采样时，在降雨较少且季节性较强的地点，无梗囊霉属的孢子相对丰度较低，而球囊霉属的孢子相对丰度较高。
