Rapid losses of surface elevation following tree girdling and cutting in tropical mangroves.
Rapid losses of surface elevation following tree girdling and cutting in tropical mangroves.
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DOI：
10.1371/journal.pone.0107868
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Huxham M
中科院分区：
文献类型：
--
作者：
Lang'at JK;Kairo JG;Mencuccini M;Bouillon S;Skov MW;Waldron S;Huxham M
红树林在固碳和海岸保护方面的重要性已得到广泛认可。飓风或砍伐对这些森林造成的大规模破坏可能会增加其易受侵蚀、下沉和快速碳损失的风险。然而，目前尚不清楚小规模砍伐可能会对红树林的功能和服务产生何种影响。我们在肯尼亚加济湾的一片红树林中，通过实验研究了小规模砍伐树木对地表高度和碳动态的影响。5个样地的树种。森林首先被环扎起来，然后被砍伐。同一地点的另一组五块地作为对照。治疗引起显著的快速下沉(对照组−为32.1±8.4mmyr−1，体表高度变化为+4.2mmyr−1)。经过处理的地块的下沉可能是由于枯死的根的坍塌和分解以及沉积物的压实，这是沉积物容重增加的证据。底泥中CO2和CH4的释放量显著增加，特别是其异养组分，表明有机质的分解作用增强。与对照样地相比，处理样地的总过剩通量估计为25.3±7.4tCO2 ha−1年−1(使用表层碳排放)和35.6±76.9tCO2 ha−1年−1(使用地表高程损失和沉积物性质)。虽然这种损失可能不是永久性的(前提是采伐面积恢复)，但观察到的快速下沉和小规模采伐导致的土壤沉积物有机质分解加剧为红树林管理提供了重要经验。特别是，红树林管理者需要仔细考虑开采红树林木材和失去其他红树林服务之间的权衡，特别是海岸线稳定、海岸保护和碳储存。
The importance of mangrove forests in carbon sequestration and coastal protection has been widely acknowledged. Large-scale damage of these forests, caused by hurricanes or clear felling, can enhance vulnerability to erosion, subsidence and rapid carbon losses. However, it is unclear how small-scale logging might impact on mangrove functions and services. We experimentally investigated the impact of small-scale tree removal on surface elevation and carbon dynamics in a mangrove forest at Gazi bay, Kenya. The trees in five plots of a Rhizophora mucronata (Lam.) forest were first girdled and then cut. Another set of five plots at the same site served as controls. Treatment induced significant, rapid subsidence (−32.1±8.4 mm yr−1 compared with surface elevation changes of +4.2±1.4 mm yr−1 in controls). Subsidence in treated plots was likely due to collapse and decomposition of dying roots and sediment compaction as evidenced from increased sediment bulk density. Sediment effluxes of CO2 and CH4 increased significantly, especially their heterotrophic component, suggesting enhanced organic matter decomposition. Estimates of total excess fluxes from treated compared with control plots were 25.3±7.4 tCO2 ha−1 yr−1 (using surface carbon efflux) and 35.6±76.9 tCO2 ha−1 yr−1 (using surface elevation losses and sediment properties). Whilst such losses might not be permanent (provided cut areas recover), observed rapid subsidence and enhanced decomposition of soil sediment organic matter caused by small-scale harvesting offers important lessons for mangrove management. In particular mangrove managers need to carefully consider the trade-offs between extracting mangrove wood and losing other mangrove services, particularly shoreline stabilization, coastal protection and carbon storage.
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