Forests play an important role in mitigating many of the negative effects of climate change. One of the ways trees mitigate impacts of climate change is by absorbing carbon dioxide and storing carbon in their wood, leaves, roots, and soil. Field assessments are used to quantify the carbon storage across different forested landscapes. The number of trees, their size, and total area inform estimates of how much carbon they store. Urban forested natural areas often have greater tree density compared to trees planted in designed cityscapes suggesting that natural area forests could be an important carbon stock for cities. We report a carbon budget for urban forested natural area using field-collected data across an entire city and model carbon stock and annual stock change in multiple forest pools. We find that natural area forests in New York City store a mean of 263.04 (95% CI 256.61, 270.40) Mg C ha^-1 and we estimate that 1.86 Tg C (95% CI 1.60, 2.13 Tg C) is stored in the city’s forested natural areas. We provide an upper estimate that these forests sequester carbon at a mean rate of 7.42 (95% CI 7.13, 7.71) Mg C ha^-1 y^-1 totaling 0.044 Tg (95% CI 0.028, 0.055) of carbon annually, with the majority being stored in trees and soil. Urban forested natural areas store carbon at similar and in some cases higher rates compared to rural forests. Native oak-dominated forests with large mature trees store the most carbon. When compared to previous estimates of urban-canopy carbon storage, we find that trees in natural area forests in New York City account for the majority of carbon stored despite being a minority of the tree canopy. Our results show that urban forested natural areas play an important role in localized, natural climate solutions and should be at the center of urban greening policies looking to mitigate the climate footprint of cities.

森林在减轻气候变化的许多负面影响方面发挥着重要作用。树木减轻气候变化影响的方法之一是吸收二氧化碳并将碳储存在它们的木材、叶子、根和土壤中。实地评估用于量化不同森林景观的碳储存。树木的数量、大小和总面积可以估算它们储存的碳量。与在设计的城市景观中种植的树木相比，城市森林自然区域的树木密度通常更高，这表明自然区域森林可能是城市的重要碳储量。我们使用整个城市的现场收集数据报告城市森林自然区域的碳预算，并模拟多个森林库中的碳储量和年度储量变化。^-1，我们估计在城市的森林自然区域中储存了 1.86 Tg C（95% CI 1.60，2.13 Tg C）。我们提供了一个上限估计，即这些森林以 7.42 (95% CI 7.13, 7.71) Mg C ha ^-1 y ^-1的平均速率固碳每年总计 0.044 Tg (95% CI 0.028, 0.055) 的碳，其中大部分储存在树木和土壤中。与农村森林相比，城市森林自然区域的碳储存率相似，在某些情况下更高。拥有大型成熟树木的以橡树为主的原生森林储存的碳最多。与之前对城市冠层碳储存的估计相比，我们发现纽约市自然森林中的树木占了储存的大部分碳，尽管只是树冠的一小部分。我们的研究结果表明，城市森林自然区域在局部自然气候解决方案中发挥着重要作用，应该成为旨在减轻城市气候足迹的城市绿化政策的核心。