India has committed to increase carbon sequestration by forests under the Nationally Determined Contributions (NDC). However, the CO2 carbon exchange characteristics (Gross Primary Productivity, Net Ecosystem Exchange, and Ecosystem respiration) of Indian forests are poorly understood. Immense carbon sequestration opportunities exist with the natural as well as planted forests. Therefore, it becomes vital to assess the potential of existing forests (natural and planted) by means of the most accurate and reliable methods of eddy covariance (EC). It is also important to know the eco-physiological response of the forests towards diurnal, seasonal, and yearly changes in the prevailing environmental conditions. We analyzed CO2 carbon exchange characteristics of a mature moist deciduous forest and a young mixed deciduous plantation located in the sub-tropical climate regime in the western Himalayan foothills of India with the help of co-located EC measurements (2016 to 2018). The study reveals that both the mature forest (− 719.43 gCm− 2year− 1) and young plantation (− 467.49 gC m− 2 year− 1) are absorbing a significant amount of atmospheric CO2 carbon. The maximum uptake of atmospheric CO2 occurred during the post-monsoon season in both the forests. The minimum NEE of the mixed deciduous plantation was observed during the leaf fall period while the NEE of the moist deciduous forest was the lowest in monsoon due to a higher respiration rate during monsoon. Among the environmental factors, soil moisture showed maximum control on the productivity of both the forest ecosystems. The value reported in this study can help Forest Survey of India in establishing/assessing emission factor for these particular forest types. This study can also help forest managers in carbon assessment of plantation under NDC.

中文翻译：

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印度喜马拉雅西部山麓天然林和人工林碳交换的环境控制

印度已承诺根据国家自主贡献 (NDC) 增加森林的碳固存。然而，人们对印度森林的 CO2 碳交换特征（总初级生产力、净生态系统交换和生态系统呼吸）知之甚少。天然林和人工林都存在巨大的固碳机会。因此，通过最准确和可靠的涡度协方差 (EC) 方法评估现有森林（天然和人工林）的潜力变得至关重要。了解森林对主要环境条件的昼夜、季节和年度变化的生态生理反应也很重要。我们借助同位 EC 测量（2016 年至 2018 年）分析了位于印度喜马拉雅西部亚热带气候区的成熟湿润落叶林和年轻混合落叶林的 CO2 碳交换特征。研究表明，成熟森林 (− 719.43 gCm− 2year− 1) 和幼林 (− 467.49 gCm− 2 year− 1) 都在吸收大量的大气 CO2 碳。两个森林的大气 CO2 最大吸收发生在季风后季节。在落叶期间观察到混合落叶林的NEE最小，而潮湿的落叶林的NEE在季风期间最低，因为季风期间呼吸速率较高。在环境因素中，土壤水分显示出对两个森林生态系统生产力的最大控制。本研究报告的值可以帮助印度森林调查局建立/评估这些特定森林类型的排放因子。这项研究还可以帮助森林管理者对 NDC 下的人工林进行碳评估。