Rainfall variability and vegetation recovery in rocky desertification areas recorded in recently-deposited stalagmites from Guilin, South China
Rainfall variability and vegetation recovery in rocky desertification areas recorded in recently-deposited stalagmites from Guilin, South China
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DOI：
10.1016/j.quaint.2019.01.039
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发表时间：
2019
影响因子：
2.2
通讯作者：
Jiangning Yin;Hong-chun Li;Wei Tang;Zhijun Wang;H. Mii;Yushi Lin
中科院分区：
文献类型：
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作者：
Jiangning Yin;Hong-chun Li;Wei Tang;Zhijun Wang;H. Mii;Yushi Lin
利用230th /U、210Pb和AMS14C测年技术，对桂林毛茅头大洞生长活跃的石笋（样品DY-2）进行了测年。post-bomb14C曲线显示，DY-2的沉积时间为1964-2009 CE，该石笋长9.3 cm，生长速度为~ 2.25 mm/a。与毛茅头大洞位于同一地区的盘龙洞石笋样品PL4的顶部7 mm部分的210pb测年限制了1830-2009 CE的沉积间隔，其生长速率要慢得多，为~ 0.04 mm/a。在年代不确定性范围内，dy2和PL4的δ18O变化在年代际尺度上具有高度可比性，并且与当地仪器降雨和历史干湿指数记录具有良好的一致性。这两个δ18O记录表明桂林地区的降水变率受太平洋年代际涛动（PDO）和El Niño-Southern涛动（ENSO）的调制，后者可以影响东亚夏季风（EASM）和西太平洋副热带高压（WPSH）。在年-年代际尺度上，EASM强度和WPSH的增加以及负（冷）PDO和La Niña相的转移会增强桂林地区夏季降水，石笋δ18O值较低。而减弱的东亚东部和西太平洋副热带气旋与正（暖）PDO和El Niño相将导致华南地区气候偏干燥。此外，石笋δ13C和死碳比（DCP）记录在近几十年呈逐渐降低的趋势。从桂林地区渗流水中土壤co2和溶解无机碳（DIC）浓度同步增加的结果来看，石笋δ13C和DCP的变化可能反映了桂林石漠化地区植被恢复的历史，20世纪90年代以来，桂林石漠化地区由于造林政策和措施的影响，石漠化面积一直在减少。
An actively growing stalagmite (sample DY-2) from Maomaotou Big Cave in Guilin, south China was dated using a combined approach of230Th/U,210Pb and AMS14C dating techniques. The post-bomb14C curve shows that the DY-2 was deposited during 1964–2009 CE and a fast growth rate of ∼2.25 mm/a was determined for this 9.3 cm-long stalagmite. The210Pb dating of the top 7 mm part of another stalagmite sample PL4 from Panlong Cave located in the same area as the Maomaotou Big Cave constrained a depositional interval during 1830–2009 CE with a much slower growth rate of ∼0.04 mm/a. The δ18O variations of DY-2 and PL4 are highly comparable on decadal time-scales within age uncertainties, and both reveal a good coherence with local instrumental rainfall and historic dry-wet index records. These two δ18O records suggest that rainfall variability in the region of Guilin is modulated by Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO), as the latter can affect the East Asian Summer Monsoon (EASM) and Western Pacific Subtropical High (WPSH). On annual-to-decadal scales, the increase of EASM intensity and WPSH as well as the shift of negative (cold) PDO and La Niña phases would enhance the summer rainfall in the Guilin region, as revealed by the lower stalagmite δ18O values. While weakening EASM and WPSH with positive (warm) PDO and El Niño phases tend to lead to a dry climate in this region of south China. In addition, the stalagmite δ13C and Dead Carbon Proportion (DCP) records show gradually decreasing trends over the last several decades. According to the findings of synchronous increase in both soilpCO2and dissolved inorganic carbon (DIC) concentrations in seepage waters from the area of Guilin, the variation of stalagmite δ13C and DCP may reflect a history of vegetation recovery in such a rocky desertification area like Guilin, where the area of rocky desertification has been reducing since the 1990s due to afforestation policies and measures.