Deforestation and land use change (LUC) to expand the agricultural frontier in the Brazilian Amazon deplete soil carbon (C) stocks, and negatively impact climate regulation. The variety of soil types, land-transition options, and management practices present in the Amazon region require detailed inventories to reduce the uncertainties associated with estimates of soil C change. Therefore, we conducted a study covering ca. 1 million hectares to estimate the soil C stock changes due to LUC in Paragominas and Santarém, Pará state, eastern Brazilian Amazon, for the period of 1990–2010. Soil C stocks for 1990 were modeled based on land cover at the time. In 2010, we carried out a field work taking soil samples to measure soil C stock changes in 356 transects across contrasting land uses (logged and burnt forest, young secondary forest, intermediate secondary forest, old secondary forest, pasture, and cropland). The response ratios for the conversion from undisturbed forest to new land uses were calculated considering the differences in soil C stocks, with the undisturbed forest as reference. Between 1990 and 2010, LUC induced a total loss of 1.51 Tg C year^-1 (over an area of 7350 km²). For this period, the uncertainty of estimates was ± 23.2%. The land transitions to pasture and cropland were the main drivers of soil C losses. Thus, deforestation contributes to climate change not only through losses of forest biomass but also subsequently soil C losses. These results can inform national and international climate change initiatives associated with LUC in the eastern Brazilian Amazon.

森林砍伐和土地利用变化 (LUC) 扩大了巴西亚马逊地区的农业前沿，耗尽了土壤碳 (C) 储量，并对气候调节产生了负面影响。亚马逊地区存在多种土壤类型、土地过渡选项和管理实践，需要详细的清单以减少与土壤碳变化估算相关的不确定性。因此，我们进行了一项涵盖约的研究。100 万公顷，用于估计 1990-2010 年期间巴西亚马逊东部帕拉州帕拉戈米纳斯和圣塔伦因 LUC 引起的土壤碳库变化。1990 年的土壤碳储量是根据当时的土地覆被建模的。2010 年，我们开展了一项实地工作，采集土壤样本以测量不同土地利用（伐木和烧毁林、幼龄次生林、中次生林、老次生林、牧场和农田）。考虑到土壤碳库的差异，以未受干扰的森林为参考，计算了从未受干扰的森林到新的土地利用转换的响应比。1990 年至 2010 年间，LUC 导致总损失 1.51 Tg C 年^-1（超过7350 km ²的面积）。在此期间，估计的不确定性为 ± 23.2%。土地向牧场和农田的转变是土壤碳流失的主要驱动因素。因此，森林砍伐不仅通过森林生物量的损失而且随后的土壤碳损失也会导致气候变化。这些结果可为与巴西亚马逊东部地区 LUC 相关的国家和国际气候变化举措提供信息。