Plant Functional Biology and Climate Change Cluster, School of Life Sciences, University of Technology Sydney, Ultimo, NSW, 2007, Australia.
Department of Environmental Sciences, Macquarie University, Sydney, NSW, 2109, Australia.
Glob Chang Biol. 2016 Mar;22(3):1097-109. doi: 10.1111/gcb.13158. Epub 2015 Dec 15.
Shifts in ecosystem structure have been observed over recent decades as woody plants encroach upon grasslands and wetlands globally. The migration of mangrove forests into salt marsh ecosystems is one such shift which could have important implications for global 'blue carbon' stocks. To date, attempts to quantify changes in ecosystem function are essentially constrained to climate-mediated pulses (30 years or less) of encroachment occurring at the thermal limits of mangroves. In this study, we track the continuous, lateral encroachment of mangroves into two south-eastern Australian salt marshes over a period of 70 years and quantify corresponding changes in biomass and belowground C stores. Substantial increases in biomass and belowground C stores have resulted as mangroves replaced salt marsh at both marine and estuarine sites. After 30 years, aboveground biomass was significantly higher than salt marsh, with biomass continuing to increase with mangrove age. Biomass increased at the mesohaline river site by 130 ± 18 Mg biomass km(-2) yr(-1) (mean ± SE), a 2.5 times higher rate than the marine embayment site (52 ± 10 Mg biomass km(-2) yr(-1) ), suggesting local constraints on biomass production. At both sites, and across all vegetation categories, belowground C considerably outweighed aboveground biomass stocks, with belowground C stocks increasing at up to 230 ± 62 Mg C km(-2) yr(-1) (± SE) as mangrove forests developed. Over the past 70 years, we estimate mangrove encroachment may have already enhanced intertidal biomass by up to 283 097 Mg and belowground C stocks by over 500 000 Mg in the state of New South Wales alone. Under changing climatic conditions and rising sea levels, global blue carbon storage may be enhanced as mangrove encroachment becomes more widespread, thereby countering global warming.
近几十年来，随着木本植物在全球范围内侵入草原和湿地，生态系统结构已经发生了变化。红树林向盐沼生态系统的迁移就是这样一种变化，它可能对全球“蓝碳”储量产生重要影响。迄今为止，定量评估生态系统功能变化的尝试基本上受到了限制，只能在红树林热极限内发生的气候介导脉冲（30 年或更短时间）的侵入中进行。在这项研究中，我们跟踪了红树林在 70 年内连续向澳大利亚东南部两个盐沼的侧向侵入，并量化了生物量和地下 C 储量的相应变化。由于红树林在海洋和河口地点取代了盐沼，生物量和地下 C 储量大幅增加。30 年后，地上生物量显著高于盐沼，并且随着红树林年龄的增长，生物量继续增加。在中盐河地点，生物量每年增加 130 ± 18 Mg 生物量 km(-2)（平均值 ± 标准误差），比海洋港湾地点（52 ± 10 Mg 生物量 km(-2) yr(-1)）高 2.5 倍，表明生物量产生存在局部限制。在这两个地点，以及所有植被类别中，地下 C 储量远远超过地上生物量，随着红树林森林的发展，地下 C 储量每年增加高达 230 ± 62 Mg C km(-2) yr(-1)（± SE）。在过去的 70 年中，我们估计仅在新南威尔士州，红树林的侵入可能已经使潮间带生物量增加了多达 283 097 Mg，地下 C 储量增加了 500 000 Mg 以上。在气候变化和海平面上升的情况下，随着红树林侵入的范围更加广泛，全球蓝碳储存可能会增加，从而抵消全球变暖。
