Abstract Reforestation is the largest natural climate solution, while potentially reversing the biodiversity crisis, especially in tropical countries. Dry tropical forests are of particular interest because they experienced greater historic loss, and offer large reforestation opportunities. This study addressed the potential of secondary forests in dry tropical systems regenerating after 60 + years in cattle pasture to accumulate carbon while increasing floristic diversity. Total carbon and woody species diversity were quantified within experimental treatments established 15 years ago. Initial active management practices included removing exotic grass with herbicide, excluding cattle by constructing live fences, and monitoring succession relative to proximity to forested riparian zones and slope position. Overall, carbon accumulated relatively slowly in this landscape (1.30 MgC Ha-1 Yr-1). Differences were seen between management practices and landscape characteristics. Lower slope plots, adjacent to forested zones, had significantly more carbon than upper slope plots, isolated from riparian zones. The initial application of herbicide decreased total carbon. However, natural regeneration of two valuable timber species with small seeds, Astronium graveolens and Cedrela odorata, benefited from this initial treatment. Live fences that were initially planted to exclude cattle significantly increased carbon of regenerating woody species. Lianas were abundant at this successional stage. Almost half of all inventoried trees (44%) had at least one liana climbing through them, with the most common species being Bauhinia glabra and Macherium microfolium. Some valuable timber tree species found within older, protected riparian forests were not yet regenerating in any treatment, such as the wind-dispersed species, Cieba pentandra, and the animal dispersed species, Hymenaea coubaril. These species may need to be actively planted at the mid-successional stage (~15–20 years) to restore biodiversity. A trade-off between timber value, diversity, and carbon sequestration must be considered in reforestation programs and this depends on landscape characteristics and management. Passive management, even with invasive grass species, is a practical option when sites are located near forested riparian zones due to low cost and high timber value of a suite of native species that naturally regenerate. No intervention is needed other than continual protection from fire and grazing. However, low-cost management, such cutting lianas and enrichment planting at the mid-successional stage, is likely to increase carbon accumulation and diversity. More active management, such as planting drought-tolerant, higher timber value tree species, is recommended at sites isolated from forested riparian zones on upper slopes where carbon accumulation is lower. Tropical forest regeneration mechanisms in proximity to forest fragments can be surprisingly resilient if chronic human impacts are removed.

中文翻译：

---

季节性干旱热带生态系统中主动管理和景观特征对碳积累和多样性的长期影响

摘要 重新造林是最大的自然气候解决方案，同时有可能扭转生物多样性危机，尤其是在热带国家。干燥的热带森林特别令人感兴趣，因为它们经历了更大的历史损失，并提供了大量的重新造林机会。本研究探讨了干燥热带系统中次生林在牛牧场中再生 60 多年后在积累碳的同时增加植物多样性的潜力。在 15 年前建立的实验处理中量化了总碳和木本物种多样性。最初的积极管理实践包括用除草剂清除外来草，通过建造活栅栏将牛排除在外，以及监测相对于森林河岸带和斜坡位置的邻近程度。全面的，碳在该景观中积累相对缓慢（1.30 MgC Ha-1 Yr-1）。管理实践和景观特征之间存在差异。与森林地带相邻的下坡地块的碳含量明显高于与河岸带隔离的上坡地块。除草剂的初始施用降低了总碳。然而，两种具有小种子的珍贵木材物种 Astronium Graveolens 和 Cedrela odorata 的自然再生受益于这种初始处理。最初为排除牛而种植的活栅栏显着增加了再生木本物种的碳。在这个演替阶段，藤本植物丰富。在所有被清查的树木中，几乎有一半 (44%) 至少有一种藤本植物，其中最常见的物种是光紫荆和小叶马赫里 (Macherium microfolium)。在受保护的较老河岸森林中发现的一些有价值的木材树种尚未通过任何处理再生，例如风散树种 Cieba pentandra 和动物散布树种 Hymenaea coubaril。这些物种可能需要在中期阶段（约 15-20 年）积极种植以恢复生物多样性。在重新造林计划中必须考虑木材价值、多样性和碳固存之间的权衡，这取决于景观特征和管理。由于一系列自然再生的本地物种成本低且木材价值高，被动管理，即使是侵入性草种，也是一种实用的选择，当站点位于森林河岸带附近时。除了持续防止火灾和放牧外，不需要任何干预。然而，低成本的管理，这种在过渡中期的切割藤本植物和浓缩种植可能会增加碳积累和多样性。更积极的管理，例如种植耐旱、木材价值较高的树种，建议在与碳积累较低的上坡森林河岸带隔离的地点。如果消除人类的慢性影响，靠近森林碎片的热带森林再生机制可能具有惊人的弹性。