Recent vegetation changes in central Queensland, Australia: Evidence from δ13C and 14C analyses of soil organic matter
Recent vegetation changes in central Queensland, Australia: Evidence from δ13C and 14C analyses of soil organic matter
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DOI：
10.1016/j.geoderma.2004.09.012
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发表时间：
2005-06
期刊：
影响因子：
6.1
通讯作者：
E. Krull;J. Skjemstad;William H. Burrows;Steven G. Bray;Jonathan G. Wynn;R. Bol;Leonie Spouncer;B. Harms
中科院分区：
文献类型：
--
作者：
E. Krull;J. Skjemstad;William H. Burrows;Steven G. Bray;Jonathan G. Wynn;R. Bol;Leonie Spouncer;B. Harms
本研究探讨从草地到木本植被的变化是否符合欧洲农业实践（过去50-150年）在昆士兰州中部的开始，使用的网站，历史记录表明入侵的木本植被（金合欢属）。土壤样品沿着样带，跨越C4占主导地位的草地和C3占主导地位的林地之间的过渡。利用土壤有机质（SOM）的δ 13 C和14 C数据来推断植被和土壤碳储量变化的时间过程。土壤有机质δ 13 C值表明，与草地相比，林地土壤有机质的碳源由草源（C4）向树源（C3）转移。粒度分离物的δ 13 C分析表明，大多数不稳定的C3衍生碳存在于颗粒有机碳（POC）部分（>53 μm）（低至30 cm）中，而<53 μm部分的δ 13 C值显示出更大的C4贡献。草地和过渡带的POC和<53 μm组分的δ 13 C值存在显著差异，推断从C4-到C3-占主导地位的系统的变化相对较近（<100年）。这一解释得到了14 C数据的支持，因为>200 μ m和53-200 μm组分的14 C活性都大于108%现代（pMC），表明大多数C3衍生的POC组分是在过去的2045年中形成的。这种“炸弹衍生的”碳（>100 pMC）存在于30 cm的深度。因此，14 C和δ 13 C数据的大小部分表明，在这个网站上的植被变化发生在过去的50年。我们还发现，加厚网站有更大的C存储在地上生物量和土壤碳储量相比，草地网站。使用Roth-C模型对碳储存变化进行的初步建模支持从草地到林地的变化可能发生在不到100年前。
This study examines whether changes from grassy to woody vegetation coincide with the initiation of European farming practices (last 50–150 years) in central Queensland, using a site where historical records suggest invasion of woody vegetation (Acacia sp.). Soil samples were taken along a transect, spanning the transition between C4-dominated grassland and C3-dominated woodland. We utilize δ13C and14C data of bulk and size-separated soil organic matter (SOM) to infer the time course of changes in vegetation and soil carbon stocks. δ13C values of bulk SOM indicate a shift from grass (C4)- to tree (C3)-derived carbon in the woodland compared with the grassland. The δ13C analyses of the size-separates showed that most of the labile, C3-derived carbon was present in the particulate organic carbon (POC) fraction (>53 μm) (down to 30 cm), whereas δ13C values in the <53 μm fraction showed greater C4 contributions. The δ13C values of the POC and the <53 μm fractions in the grassland and transition zone were significantly different, inferring a relatively recent change from a C4- to a C3-dominated system (<100 years). This interpretation is supported by14C data as the14C activity of both the >200 and 53–200 μm fraction was greater than 108% modern (pMC), indicating that most of the C3-derived POC fractions were formed during the past ∼45 years. This “bomb-derived” carbon (>100 pMC) was present to a depth of 30 cm. Thus,14C and δ13C data from the size fractions indicate that much of the vegetation change at this site occurred over the last 50 years. We also found that the thickened site had greater C storage in above-ground biomass and soil carbon stocks compared with the grassy site. Preliminary modelling of changes in carbon stocks, using the Roth-C model, support that the change from grassland to woodland probably occurred <100 years ago.