Plant-mycorrhizal associations vary with climate and soil in tropical mountainscapes influenced by landslides: Implications for ecosystem development and soil formation

Landsliding creates new substrates upon which ecosystems develop. From a recovery perspective, these substrates may limit plant growth due their harsh conditions. Yet, from a soil formation perspective, these substrates may enhance weathering rates due to a combination of abiotic and biotic factors. Central to both is the role that mycorrhiza may play in ecosystem development, including biogeochemical cycles. Given that at mountainscape scales landslide populations are diverse due to variation in underlying climatic and edaphic conditions, we hypothesize that plant-mycorrhizal associations and their functions will mirror this diversity. To test this hypothesis, we focus on the Sierra de Las Minas in Guatemala (SLM), a mountain range that offers contrasting climatic characteristics associated with aspect (south aspect is dry to mesic and north aspect wet) and steep elevation gradients (400 – 2600 m a.s.l.). Leveraging plant and soil inventories conducted in forest and landslide habitats in the SLM we ask 1) How do plant-mycorrhizal associations vary with aspect, elevation, and habitat? 2) What is the contribution of soil chemistry to the observed variation in plant-mycorrhizal associations? And 3) How do plant-mycorrhizal associations and environmental conditions explain variation in weathering rates? To answer these questions, we integrated our plant inventories with a global database on plant-mycorrhizal associations. The former contains species composition and soil elemental analyses that we used to estimate a variety of weathering indices. The latter was used to assign plants from our field inventories to one or more mycorrhizal type.

Plant-mycorrhizal associations were diverse and greatly contributed to the separation of plant communities in multivariate space. Aspect followed by habitat explained a large fraction of the observed variability. Subsets of soil variables correlated with different dimensions derived from principal component analyses suggesting that plant-mycorrhizal associations contribute diverse functions. In general, weathering indexes differed with aspect and habitat. For example, Vogt Residual Index and Chemical Index of Alteration, were higher in landslide than forest and this difference was more pronounced in the wet than dry to mesic aspects. Further analyses will allow us to examine the contribution of plant-mycorrhizal associations to ecosystem development and soil formation in tropical mountainscapes influenced by landslide activity.