Coverage rate, a critical variable for gridded forest area, has been neglected by previous studies in estimating the annual gross primary production (GPP) of global forest ecosystems. In this study, we investigated to what extent the coverage rate could impact forest GPP estimates from 1982 to 2011. Here we show that the traditional calculation without considering the coverage rate globally overestimated the forest gross carbon dioxide uptake by approximately 8.7%, with a value of 5.12 ± 0.23 Pg C yr−1, which is equivalent to 48% of the annual emissions from anthropogenic activities in 2012. Actually, the global annual GPP of forest ecosystems is approximately 53.71 ± 4.83 Pg C yr−1 for the past 30 years by taking the coverage rate into account. Accordingly, we argue that forest annual GPP calculated by previous studies has been overestimated due to the exaggerated forest area, and therefore, coverage rate may be a required factor to further quantify the global carbon cycle.
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机译：覆盖率是网格化森林面积的关键变量，以前的研究在估计全球森林生态系统的年度初级总产值（GPP）时已被忽略。在这项研究中，我们调查了1982年至2011年森林覆盖率对森林GPP估算的影响程度。在这里，我们表明，不考虑全球覆盖率的传统计算高估了森林总二氧化碳吸收量约8.7％，其值为5.12±0.23 Pg C yr −1 的平均值，相当于2012年人为活动的年排放量的48％。实际上，全球森林生态系统的年度GPP约为53.71±4.83 Pg C yr在过去30年中， −1 考虑了覆盖率。因此，我们认为，由于森林面积过大，以前的研究计算出的森林年度GPP被高估了，因此，覆盖率可能是进一步量化全球碳循环的必要因素。
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