Large contribution of recent photosynthate to soil respiration in tropical dipterocarp forest revealed by girdling
Large contribution of recent photosynthate to soil respiration in tropical dipterocarp forest revealed by girdling
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DOI：
10.1111/1365-2745.13806
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发表时间：
2021-10
影响因子：
5.5
通讯作者：
A. Nottingham;A. Cheesman;T. Riutta;C. Doughty;Elizabeth M. Telford;W. Huaraca Huasco;Martin Svátek;Jakub Kvasnica;N. Majalap;Y. Malhi;P. Meir;Y. Teh
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作者：
A. Nottingham;A. Cheesman;T. Riutta;C. Doughty;Elizabeth M. Telford;W. Huaraca Huasco;Martin Svátek;Jakub Kvasnica;N. Majalap;Y. Malhi;P. Meir;Y. Teh
热带森林是最具生产力的陆地生态系统，每年从大气中固定超过40毫克的碳。这些碳的很大一部分被分配到地下的根和与根相关的微生物中。然而，关于这种地下转移动态的实证研究很少，特别是在热带森林中，碳分配过程受高度植物物种多样性的影响。在婆罗洲的热带低地森林中，我们采用了一种全林分围篱实验来阻止近期光合作用的地下转移。通过在一个0.48 ha的地块上环绕209棵大树，我们确定了：(a)近期光合作用对根际呼吸的贡献；(b)地下碳供应中断与树种组成和死亡率之间的关系。209棵树370 d后的死亡率为62%，不同树种间差异较大，其中梁木科（99%）和壳斗科（100%）的死亡率最高。我们还观察到，对于木材密度较低的树种，围育后的死亡率更高。土壤CO2排放量在围篱后50天内显著下降（36±5%）。在其他3个子样地，土壤CO2排放量对环带的响应或略有下降或无响应。土壤CO2外排减少幅度较大，以龙脑科为主。合成。研究结果表明，该热带森林地下碳分配与根际呼吸的耦合存在较大的空间差异，在以梁木科为主的森林中耦合更紧密。我们的研究结果强调了热带森林树种组成对地下碳转移及其向大气释放的影响。
Tropical forests are the most productive terrestrial ecosystems, fixing over 40 Pg of carbon from the atmosphere each year. A substantial portion of this carbon is allocated below‐ground to roots and root‐associated micro‐organisms. However, there have been very few empirical studies on the dynamics of this below ground transfer, especially in tropical forests where carbon allocation processes are influenced by high plant species diversity. We used a whole‐stand girdling experiment to halt the below‐ground transfer of recent photosynthates in a lowland tropical forest in Borneo. By girdling 209 large trees in a 0.48 ha plot, we determined: (a) the contribution of recent photosynthate to root‐rhizosphere respiration and; (b) the relationships among the disruption of this below‐ground carbon supply, tree species composition and mortality. Mortality of the 209 trees was 62% after 370 days, with large variation among species and particularly high mortality within the Dipterocarpaceae (99%) and Fagaceae (100%) families. We also observed a higher risk of mortality following girdling for species with lower wood density. Soil CO2 emissions declined markedly (36 ± 5%) over ~50 days following girdling in three of six monitored subplots. In the other three subplots there was either a marginal decline or no response of soil CO2 emissions to girdling. The decrease in soil CO2 efflux was larger in subplots with dominance of Dipterocarpaceae. Synthesis. Our results indicate high spatial variation in the coupling of below‐ground carbon allocation and root‐rhizosphere respiration in this tropical forest, with a closer coupling in forest dominated by Dipterocarpaceae. Our findings highlight the implications of tree species composition of tropical forests in affecting the dynamics of below‐ground carbon transfer and its release to the atmosphere.