Tropical forest soils contain some of the largest carbon (C) stocks on Earth, yet the effects of warming on the fate of fresh C entering tropical soils are still poorly understood. This research sought to understand how the fate of fresh C entering soils is influenced by warming, soil weathering status, and C chemistry. We hypothesized that compounds that are quickly incorporated into microbial biomass (i.e., greater C use efficiency [CUE]) subsequently have longer-term (255 days) retention in soil. We also hypothesized that relatively weathered soils with greater sorptive capacity also retain more fresh C in the short and longer-terms, and that C in these soils is more resistant to weathering loss compared with less weathered soils. We tested these hypotheses by adding two ¹³C-labeled compounds (glucose and glycine) to three tropical forest soils from a weathering gradient in Hawai'i, and then incubating soils at ambient (16 °C), +5 °C, and +10 °C for 255 days. We found that 255-day ¹³C retention in mineral soil across sites and temperatures was best predicted by two factors: initial retention of ¹³C in mineral soil and initial microbial ¹³CUE (Adjusted R² = 0.78). Carbon compound type influenced ¹³C initial retention, with greater glucose-¹³C retention versus glycine-¹³C retention in mineral soils and microbial biomass, corresponding to greater glucose-¹³C retention in soil at 255 days. Warming had a negative longer-term effect on the retention of ¹³C only in the least-weathered soil, supporting our hypothesis. These results show that initial retention of fresh C in soils via mineral sorption and microbial uptake is a strong predictor of longer-term retention, indicating that immediate C losses are a major hurdle for soil C storage. Also, retention of fresh C appears most sensitive to warming in less-weathered tropical soils, supporting the idea that mineral sorption may provide some protections against warming. Understanding the interaction between soil sorptive properties and warming for C cycling could improve predictions of forest-climate feedbacks for tropical regions.

热带森林土壤中含有一些地球上最大的碳（C）储量，但人们对变暖对进入热带土壤的新鲜C的命运的影响仍知之甚少。这项研究试图了解新鲜碳进入土壤的命运如何受到变暖，土壤风化状况和碳化学的影响。我们假设迅速被掺入微生物生物量（即更高的碳利用效率[CUE]）的化合物随后在土壤中具有更长时间（255天）的保留时间。我们还假设，具有相对较大吸附能力的相对风化的土壤在短期和长期内还会保留更多的新鲜碳，并且与不风化的土壤相比，这些土壤中的C对风化损失具有更强的抵抗力。我们通过添加两个¹³检验了这些假设将C标记的化合物（葡萄糖和甘氨酸）从夏威夷的风化梯度转移到三种热带森林土壤中，然后在环境温度（16°C），+ 5°C和+10°C下孵育255天。我们发现，通过两个因素可以最好地预测跨站点和温度的矿物土壤中255天的¹³ C保留：矿物土壤中¹³ C的初始保留和微生物¹³ CUE的初始保留（调整后R ²  = 0.78）。碳化合物类型影响¹³ C的初始保留，在矿质土壤和微生物生物质中，葡萄糖的¹³ C保留相对于甘氨酸¹³ C保留较高，这对应于葡萄糖^13的保留C在土壤中保留255天。升温仅在最少风化的土壤中对¹³ C的保留具有长期的负面影响，这支持了我们的假设。这些结果表明，通过矿物质吸收和微生物吸收，土壤中新鲜C的初始保留是长期保留的有力预测指标，表明立即C损失是土壤C储存的主要障碍。同样，在气候较少的热带土壤中，新鲜碳的保留似乎对变暖最敏感，这支持了矿物吸附可能提供一些防止变暖的观念。了解土壤吸附特性和碳循环变暖之间的相互作用可以改善对热带地区森林气候反馈的预测。