Land use change, particularly the conversion of forest to agriculture, is an important driver of climate change but is rarely considered a major factor in northern temperate regions. This study explored the climate impacts of temperate forest clearing for agriculture in the northeastern United States, hypothesizing that compared to managed cool-season pasture, forest conversion to silvopasture would moderate changes in surface temperature, soil greenhouse fluxes, and soil carbon and nutrient losses. To test this hypothesis, we conducted two land use change experiments, one in New York and the other in New Hampshire, USA. In both locations, forests have regenerated following a period of forest clearing, intensive agricultural management, and farm abandonment, such that secondary forests currently comprise ~60–80% of the land base. In both experiments, we measured microclimatic variables of air and soil temperature and soil moisture, soil greenhouse gas emissions of CO₂ and N₂O, and soil carbon and nitrogen content. Using a mixed-effects modeling framework, we found that near-surface air and soil temperatures were highest in converted pasture plots, lowest in reference secondary forest areas, and intermediate in the converted silvopasture treatment. Soil respiration followed a similar pattern, with elevated soil CO₂ fluxes in open pastures as compared to converted silvopasture and reference secondary forest sites. Although we detected few changes in soil C among treatments, we observed higher soil N stocks and soil N₂O fluxes in converted pastures but not in the converted silvopasture treatment. Our results suggest that silvopasture may offer a biogeochemical “middle ground” between intact secondary forests and managed open fields, retaining the climate benefits of forests while enabling expansion of the agricultural land base. Understanding the climate impacts of forest conversion to open pasture or silvopasture is critical to better anticipate the climate consequences of potentially re-emerging agricultural land uses, both across the northeastern US and other temperate forest regions globally.

土地利用变化，特别是森林向农业的转变，是气候变化的重要驱动因素，但在北温带地区很少被视为主要因素。本研究探讨了美国东北部温带森林砍伐对农业的气候影响，假设与管理的冷季牧场相比，森林转变为林牧草会缓和地表温度、土壤温室通量以及土壤碳和养分损失的变化。为了验证这一假设，我们进行了两项土地利用变化实验，一项在纽约，另一项在美国新罕布什尔州。在这两个地区，经过一段时间的森林砍伐、集约化农业管理和农场废弃后，森林已经再生，因此次生林目前占土地基础的约 60-80%。₂和N ₂ O，以及土壤碳氮含量。使用混合效应建模框架，我们发现近地表空气和土壤温度在转化牧场地块中最高，在参考次生林地区最低，在转化林地处理中处于中等水平。土壤呼吸遵循类似的模式，与转化的林地和参考次生林站点相比，开阔牧场的土壤 CO _{2通量升高。}虽然我们检测到不同处理之间土壤 C 的变化很小，但我们观察到更高的土壤 N 储量和土壤 N ₂O 通量在转换的牧场中，但在转换的林地处理中没有。我们的研究结果表明，造林可以在完整的次生林和管理的开阔地之间提供生物地球化学“中间地带”，在保持森林气候效益的同时扩大农业用地基础。了解森林转变为开阔牧场或林木牧场的气候影响对于更好地预测美国东北部和全球其他温带森林地区可能重新出现的农业用地的气候后果至关重要。