Long-term disturbance dynamics and resilience of tropical peat swamp forests

1. The coastal peat swamp forests of Sarawak, Malaysian Borneo, are undergoing rapid conversion, predominantly into oil palm plantations. This wetland ecosystem is assumed to have experienced insignificant disturbance in the past, persisting under a single ecologically-stable regime. However, there is limited knowledge of the past disturbance regime, long-term functioning and fundamentally the resilience of this ecosystem to changing natural and anthropogenic perturbations through time. 2. In this study, long-term ecological data sets from three degraded peatlands in Sarawak were collected to shed light on peat swamp forest dynamics. Fossil pollen and charcoal were counted in each sedimentary sequence to reconstruct vegetation and investigate responses to past environmental disturbance, both natural and anthropogenic. 3. Results demonstrate that peat swamp forest taxa have dominated these vegetation profiles throughout the last c. 2000-year period despite the presence of various drivers of disturbance. Evidence for episodes of climatic variability, predominantly linked to ENSO events, and wildfires is present throughout. However, in the last c. 500 years, burning and indicators of human disturbance have elevated beyond past levels at these sites, concurrent with a reduction in peat swamp forest pollen. 4. Two key insights have been gained through this palaeoecological analysis: (i) peat swamp forest vegetation has demonstrated resilience to disturbance caused by burning and climatic variability in Sarawak in the late Holocene, however (ii) coincident with increased fire combined with human impact c. 500 years ago, these communities started to decline. 5. Synthesis. Sarawak's coastal peat swamps have demonstrated resilience to past natural disturbances, with forest vegetation persisting through episodes of fire and climatic variability. However, palaeoecological data presented here suggest that recent, anthropogenic disturbances are of a greater magnitude, causing the observed decline in the peat swamp forest communities in the last c. 500 years and challenging the ecosystem's persistence. This study greatly extends our knowledge of the ecological functioning of these understudied ecosystems, providing baseline information on the past vegetation and its response to disturbance. This understanding is central to developing management strategies that foster resilience in the remaining peat swamp forests and ensure continued provision of services, namely carbon storage, from this globally important ecosystem.

1. 马来西亚婆罗洲砂拉越的沿海泥炭沼泽森林（peat swamp forest）正经历快速转化，主要转为油棕种植园（oil palm plantation）。该湿地生态系统既往被认为受干扰程度极低，长期处于单一的生态稳定状态。然而，目前学界对其既往干扰模式、长期生态功能，以及该生态系统随时间推移应对自然和人为扰动的恢复力，仍所知有限。
2. 本研究收集了砂拉越3处退化泥炭地的长期生态数据集，以阐明泥炭沼泽森林的动态变化。对各沉积序列（sedimentary sequence）中的化石花粉与炭屑进行计数，以重建植被历史，并解析其对既往自然与人为环境扰动的响应。
3. 研究结果显示，尽管存在多种扰动驱动因子，泥炭沼泽森林类群在过去约2000年的时间里始终主导这些植被剖面。记录显示，既往存在与厄尔尼诺-南方涛动（ENSO）事件相关的气候波动，以及野火活动的证据。但在过去约500年以来，该区域的燃烧事件与人为干扰指标已远超既往水平，同时泥炭沼泽森林花粉占比出现下降。
4. 通过本次古生态学分析（palaeoecological analysis），我们获得两项关键认识：其一，砂拉越全新世（Holocene）晚期的泥炭沼泽森林植被对燃烧与气候波动引发的扰动表现出恢复力；其二，约500年前，随着燃烧活动加剧叠加人类活动影响，这类森林群落开始出现衰退。
5. 综合分析表明，砂拉越沿海泥炭沼泽既往对自然扰动具备恢复力，其森林植被历经多次野火与气候波动事件仍得以存续。但本次研究提供的古生态学数据显示，近期的人为扰动强度更高，造成了过去约500年间泥炭沼泽森林群落的衰退，对该生态系统的存续构成挑战。本研究极大拓展了学界对这类未被充分研究的生态系统生态功能的认知，为重建既往植被历史及其对扰动的响应提供了基准数据。上述认识对于制定管理策略至关重要，这些策略可助力现存泥炭沼泽森林提升恢复力，并确保这一全球重要生态系统持续提供碳储存等生态系统服务功能。