Influence of Meteorological Variables on Carbon Uptake in Oak and Pine-dominated Ecosystems of Himalaya

Micrometeorological variability significantly influences the structures, functions, and dynamics of ecosystems. Despite this, there is a limited understanding of the feedback and causal relationships among micrometeorological drivers in various Himalayan ecosystems. The present study aims to investigate the meteorological controls that govern the variability in net ecosystem exchange (NEE) in Oak (Quercus leucotrichophora) and Pine (Pinus roxburghii)-dominated ecosystems of the Himalayas. We use half-hourly eddy covariance fluxes from Pine and Oak-dominated ecosystems located in Uttarakhand, India. We employ an information theory-based Temporal Information Partitioning Network (TIPNet) approach to generate weekly process networks with a 6-hour lag. The analysis conducted for the monsoon and post-monsoon seasons of 2016 and 2017 reveals that sub-daily scale variations in micrometeorological variables are responsible for fluctuations in NEE in both ecosystems. The Pine ecosystem exhibits greater sensitivity to air temperature, leading to increased carbon uptake compared to the Oak ecosystem throughout the study period. Causal connections indicate that the NEE of the Oak ecosystem is moisture-driven (influenced by precipitation and relative humidity), while that of the Pine ecosystem is heat-dominated (influenced by air temperature and net solar radiation). Precipitation effects on the Pine ecosystem are not immediate due to slower infiltration and lesser fine root production compared to Oak. However, the impact of moisture stress is evident in the network structure of both ecosystems, with more causal links occurring during dry periods compared to normal periods, indicating adaptive responses to resist moisture stress. This research enhances our understanding of micrometeorological influences on carbon dynamics in Himalayan ecosystems, providing valuable insights for ecosystem management and climate change mitigation strategies.

Keywords: Micrometeorology, Process networks, Oak, Pine, Himalayas