Reconstructing long-term fire, vegetation, climate, and human dynamics in a tropical dry forest: A 1200-year record from Mudumalai National Park, southern India

Approximately 400 million years ago, the conditions that made fire possible appeared on Earth. With suitable climate and burnable biomass, fire evolved into a phenomenon capable of shaping terrestrial ecosystem across the globe. With the arrival of humans, fire also became a tool for their dispersal, landscape modification and agriculture. Today, global climate change, intensified anthropogenic activities, and associated vegetation shifts, are increasing wildfire risk and severity across many biomes, making study of past fire–climate–vegetation–human interactions crucial. Among the key by-products of fire, charcoal is extensively used as a proxy in paleofire studies. It provides critical insights into changes in fire regimes (frequency, vegetation burned, temperature, and severity). Despite this global importance, charcoal-based research from southern India remains limited. In this study, we experimentally produced charcoal from dominant woody and herbaceous species of a tropical dry deciduous forest in the Western Ghats, southern India. It was carried out in controlled temperatures, and its morphometry and morphology were quantified across species and plant parts. Morphometric results show that charcoal derived from trees, shrubs, and grasses can be statistically distinguished, providing a robust framework for interpreting vegetation sources. Complementary FTIR analyses reveal systematic spectral changes with charring temperature, particularly in the OH, aromatic, and cellulose functional group regions, demonstrating the method’s value for independently estimating burn temperature. This reference dataset provides the missing baseline needed to identify vegetation sources, burn temperatures, and interpret fire signals preserved in sediments from this region. We then applied this reference framework to interpret sedimentary charcoal and supplemented it with biomarkers preserved in a ~1,200-year profile from the same landscape. Macrocharcoal concentrations are generally low but increase significantly in the surface and near-surface layers. The charcoal recovered aligns closely with the shrub/grass-derived signatures, indicating a predominantly shrubby/grassy fuel source during these periods. n-alkane analysis shows a predominance of short even-chain n-alkanes (C₁₆ and C₁₈), which is uncommon in sedimentary samples. The odd long-chain n-alkanes (C₂₁–C₃₃) indices such as Carbon Preference Index (CPI), P_aq, and P_wax suggest a transition from mixed aquatic–terrestrial inputs to predominantly terrestrial sources. Average Chain Length (ACL) and tree-to-grass n-alkane ratios point to increasing grass input towards the present. However, the sharp increase in grass input along with fire activity in the upper layers are more likely driven by human ecosystem modification than climate – a potential cultural pyroscape. We present here the first FTIR and morphometric charcoal reference datasets ever to be developed in India and the first multiproxy investigation to understand past fire dynamics in a protected area.