Wet and dry spell induced changes in the soil CO2 effluxes of Pine and Oak ecosystems of Central Himalaya: a comparative assessment for monsoon and winter seasons.

Soil efflux of CO2 ( F CO 2 ) is known to be dependent on natural drying and rewetting of the soil. Although the central Indian Himalayan region is predominantly occupied with two ecosystems, i. e. Pine (Pinus roxburghii) and Oak (Quercus leucotrichophora), differences in their F CO 2  dynamics and responses of F CO 2  to varying wet and dry spells were hardly known. To address this knowledge gap, this study provides a comparative assessment of F CO 2  variability from Pine and Oak ecosystems of central Himalaya as a response to rainfall induced wet and dry spells of monsoon and winter seasons. The F CO 2  data presented in this study are collected for 242 days of 2021-22 that include monsoon and winter seasons from a Pine and an Oak sites. The mean F CO 2 s of Pine and Oak sites are found to be 3.95(± 0.02) and 3.61(± 0.01) µmol.m-2.s-1, respectively. We find that the winter reduction in the F CO 2  in comparison to monsoon at the Pine site (78%) is more substantial than at Oak site (64.6%). The cross wavelet spectra of F CO 2  and monsoon rainfall amount at the Oak site, unlike the Pine site, indicate a negative relationship. The rainfall spell duration and amount of monsoon wet spells are noted to have an inverse relationship with F CO 2  at both sites, although, increasing rainfall spell duration in winter is noted to increase F CO 2  at Pine and Oak sites. Similarly, increasing F CO 2  is observed with increasing dry spells of monsoon at both sites. Results of this study indicate that in comparison to Oak, F CO 2  variability at Pine ecosystem is primarily driven by abiotic factors wherein wet spell is a major determinant.

Impact of monsoon season rainfall spells on the ecosystem carbon exchanges of Himalayan Chir-Pine and Banj-Oak-dominated forests: a comparative assessment.

The Chir-Pine (Pinus roxburghii) and Banj-Oak (Quercus leucotrichophora)-dominated ecosystems of central Himalaya provide significant green services. However, responses of these ecosystems, with respect to ecosystem carbon flux variability, to changing microclimate are not yet studied. Since quantification of ecosystem responses to fluctuation in the microclimate, particularly rainfall, is expected to be beneficial for management of these ecosystems, this study aims (i) to quantify and compare amplitude of rainfall-induced change in the carbon fluxes of Chir-Pine and Banj-Oak-dominated ecosystems using wavelet methods, and (ii) to quantify and compare dissimilarities in the ecosystem exchanges due to varying rainfall spell and amount. Eddy covariance-based continuous daily micrometeorological and flux data, during the 2016-2017 monsoon seasons (total 244 days, 122 days of June-September), from two sites in Uttarakhand, India, are used for this purpose. We find that both Chir-Pine and Banj-Oak-dominated ecosystems are the sinks of carbon, and Chir-Pine-dominated ecosystem sequesters around 1.8 times higher carbon than the Banj-Oak. A systematic enhancement in the carbon assimilation of the Chir-Pine-dominated ecosystem is noted with increasing rainfall spell following a statistically significant power-law relationship. We have also identified a rainfall amount threshold for Chir-Pine and Banj-Oak-dominated ecosystems (10 ± 0.7 and 17 ± 1.2 mm, respectively) that resulted in highest ecosystem carbon assimilation in monsoon. The general inference of this study accentuates that Banj-Oak-dominated ecosystem is more sensitive to maximum rain within a spell whereas the Chir-Pine-dominated ecosystem is more responsive to increasing rainfall spell duration.