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title: 鹤庆栎(Quercus heqingensis n. sp.)的发现及其在古大气CO_2浓度重建中的应用
Other Title: The occurrence of Quercus heqingensis n. sp. and its application to palaeo-CO_2 estimates
author: 黄华生;  胡瑾瑾;  苏涛;  周浙昆
Issued Date: 2016
Abstract: 在云南鹤庆上上新统三营组中发现大量壳斗科栎属高山栎组植物(Quercus sect. Heterobalanus)叶片化石.这些标本主脉呈Z字微弯, 基部粗壮, 至叶尖变细, 二级脉羽状互生, 且互相平行, 在近叶缘1/3~1/2处分叉; 上表皮有单、多细胞毛基, 无气孔, 表皮细胞多为近四边形; 下表皮只有单细胞毛基和环列型气孔器, 表皮细胞为近四边形或五边形. 这些特征虽然与毛脉高山栎(Q. rehderiana)、帽斗栎(Q. guyavifolia)及古帽斗栎(Q. preguyavifolia)等现生种和化石种比较相似, 但仍与它们存在叶表皮毛密度和毛基类型的差异, 故将其定为新种鹤庆栎(Quercus heqingensis n. sp.). 将鹤庆栎的气孔指数应用于已建立的其现存最近亲缘类群(Nearest Living Relatives, NLRs)帽斗栎的气孔指数与大气pCO_2的关系式, 定量重建出晚上新世时期的古大气CO_2浓度分别为263.4224.86 ppm(沿海拔梯度采集样品重建结果)和234.2522.49 ppm (历史标本样品重建结果), 与前人结果相比基本一致, 经过海拔校正后则十分吻合. 同时进一步证明了晚上新世时期的古大气CO_2浓度低于现代水平, 为利用现存最近亲缘类群作为代理(proxies)重建古大气CO_2浓度提供了可靠的证据.
English Abstract: Many leaf fossils belonging to Quercus sect. Heterobalanus were collected from the Upper Pliocene Sanying Formation in Heqing County, Yunnan Province, China. Leaves are oblong, elliptic or obovate with entire margin or spinous serrations, 3.1-8.7 cm in length and 1.8-5.7 cm in width. Leaf apex is round, mucronate or blunt round, while leaf base is heart-shaped, slightly heart-shaped or blunt round, and occasionally asymmetric. The petiole is slightly sturdy, straight or a bit curved, with 1.8-4.9 mm in length. The main vein of these specimens is slightly zigzagging, with a sturdy base attenuating to the apex. Secondary veins are pinnate, 7-12 pairs, alternate and parallel with the stretching angles from 40° to 73°, bifurcating near 1/3 to 1/2 of the leaf margin. Tertiary veins are, relatively thin, 5-7 bands in 1 cm~2, and perpendicular to secondary veins. Quaternary, blind and marginal veins are not clear. The upper epidermis has both unicellular and multicellular trichomes without stomata, and most of the epidermal cells are nearly quadrangular. The lower epidermis has only unicellular trichomes and cyclocytic stomatal apparatuses, and the epidermal cells are nearly quadrangular or pentagonal. The stomatal apparatuses are 20-33 mm in length, 17-27 mm in width, with 2-6 mm wide in apertures. They spread casually with the stomatal density of 50398 mm-2 and the stomatal index of 8.90%0.32%. The guard cells show kidney-shaped, with 5-7 subsidiary cells. These features are similar to Q. rehderiana, Q. guyavifolia, Q. preguyavifolia and some other extant or fossil species of Q. sect. Heterobalanus, but they are different in terms of density and type of trichomes. Both Q. guyavifolia and Q. preguyavifolia have more trichomes in total, and multicellular trichomes in lower epidermis which spread in veins and between veins. The fossil leaves of Q. sect. Heterobalanus in Heqing and Q. rehderiana have less trichomes, and the former has no multicellular trichome in lower epidermis, while the latters multicellular trichome are just found in veins. Hence, it was designated as a new speciesQuercus heqingensis n. sp. The estimates of palaeoatmospheric-CO_2 using the positive relationships between stomatal frequency and atmospheric CO_2 partial pressure in its Nearest Living Relatives (NLRs)Q. guyavifolia show that, the palaeo-CO_2 levels in the late Pliocene reconstructed by Q. heqingensis were 263.4224.86 ppm (equation with extant field collections) and 234.2522.49 ppm (equation with historical herbarium samples). These results are slightly lower than most previous estimates of the same age. Our results are in agreement with other estimates when palaeoaltitude is considered. This indicates that it is feasible to apply the stomatal index of Q. heqingensis to the positive relationship between stomatal index of Q. guyavifolia and atmospheric pCO_2 to reconstruct palaeo-CO_2 levels. Meanwhile, the results further support lower palaeo-CO_2 level in the late Pliocene than present. This study provides credible evidence for future palaeo-CO_2 estimates using NLRs as proxies.
Department: 其他
Source: 科学通报
Content Type: 期刊论文
URI: http://ir.xtbg.org.cn/handle/353005/10623
ISSN: 0023-074X
Language: 中文
Appears in Collections:古生态研究组_期刊论文

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Recommended Citation:
黄华生,胡瑾瑾,苏涛,等. 鹤庆栎(quercus Heqingensis N. Sp.)的发现及其在古大气co_2浓度重建中的应用[J]. 科学通报,2016,61(12):1354-1364.
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