Long-term responses of mountain forests to environmental change in West-Central Mexico

Abstract

This study is an important contribution to the International Long-term Ecological Research Network (ILTER), because it presents the local responses of soil and plant composition to global and regional climatic oscillations of the last millennia in Mexico. Mountain forests are ecosystems that have been constantly threatened by both anthropogenic and climate disturbances, mainly over the Late Holocene. By using palaeoecological techniques with fossil pollen and geochemical elements as proxies, this study incorporates the relationship of trees, herbs and epiphytes with dry and humid climate events. High-temporal resolution in the chronologies allowed the assessment of vegetation changes (every ~ 30 years) and soil geochemical elements in three forests located close (< 8 km) to each other. Our results showed that pine forest contracted along the dry periods of the Little Ice Age (AD 1350–1850), the Medieval Climate Anomaly (AD 800 to 1200) and the Late Classic Drought (AD 600 to 800). However, it expanded in the humid period (AD 1200 to 1350). Cloud forest was the most susceptible ecosystem to the above climate anomalies; trees contracted in periods of aridity and expanded in humid periods. The signature for the transitional forest was confounding: trees increased partially in both dry and humid periods with a well-correlated decrease in epiphytes. Soil losses were common in dry periods while fires increased along the last ~ 300 years.