Eocene Podocarpium (Leguminosae) from South China and its biogeographic implications

Podocarpium A. Braun ex Stizenberger is one of the most common legumes in the Neogene of Eurasia, including fossil fruits, seeds, leaves, and possible flower and pollen grains. This genus is not completely consistent with any extant genera according to gross morphological characters and poorly preserved cuticular structures reported in previous studies. The fossil pods collected from the coal-bearing series of the Changchang Basin of Hainan Island and Maoming Basin of Guangdong, South China, are examined by morphologically comparative work, with special reference to venation patterns and placental position. These distinctive features, as well as the ovule development of pods from different growing stages and the epidermal structure of the pods, as distinguished from previous records lead to the conclusion that these fossils can be recognized as a new species of Podocarpium, P. eocenicum sp. nov. This new discovery indicates that Podocarpium had arrived in South China by the Eocene. Investigation on the fossil records of this extinct genus shows that P. eocenicum is the earliest and lowest latitude fossil data. The possible occurrence pattern of this genus is revealed as follows: Podocarpium had distributed in the South China at least in the middle Eocene, and then migrated to Europe during the Oligocene; in the Miocene this genus reached its peak in Eurasia, spreading extensively across subtropical areas to warm temperate areas; finally, Podocarpium shrank rapidly and became extinct in Eurasia during the Pliocene

Distribution of Cenozoic plant relicts in China explained by drought in dry season

Cenozoic plant relicts are those groups that were once widespread in the Northern Hemisphere but are now restricted to some small isolated areas as a result of drastic climatic changes. They are good proxies to study how plants respond to climatic changes since their modern climatic requirements are known. Herein we look at the modern distribution of 65 palaeoendemic genera in China and compare it with the Chinese climatic pattern, in order to find a link between the plant distribution and climate. Central China and Taiwan Island are shown to be diversity centres of Cenozoic relict genera, consistent with the fact that these two regions have a shorter dry season with comparatively humid autumn and spring in China. Species distribution models indicate that the precipitation parameters are the most important variables to explain the distribution of relict genera. The Cenozoic wide-scale distribution of relict plants in the Northern Hemisphere is therefore considered to be linked to the widespread humid climate at that time, and the subsequent contraction of their distributional ranges was probably caused by the drying trend along with global cooling.Peer reviewe

Towards an efficacious method of using Landsat TM imagery to map forest in complex mountain terrain in Northwest Yunnan, China

Mapping forest type using Landsat TM images encounters many problems especially when applied in montane landscapes with complex terrain. In this paper we evaluated the effects of selected data inputs and classification methods on the accuracy of forest type mapping in a complex terrain landscape in mountainous southwest China. Results show that the accuracy of a forest type map produced by the original Landsat TM bands data alone is not acceptable, but the integration of topographic data with Normalised Difference Vegetation Index (NDVI) and Principle Components (PCs) improves the mapping accuracy by 15% and 14%, respectively. In addition, the comparison of two-classification methods showed that a GIS expert system (EXPERT) outperforms the maximum likelihood classifier (MLC) by 9%. It is concluded that combination of topographic data together with NDVI or PCs enable production of more reliable and accurate forest maps in landscapes with complex terrain. Where reliable field knowledge is available, expert systems show potential for producing affordable forest type maps as accuracy as those obtained by conventional classifiers

Evolution of stomatal and trichome density of the Quercus delavayi complex since the late Miocene

A fossil oak species, Quercus tenuipilosa Q. Hu et Z.K. Zhou, is reported from the upper Pliocene Ciying Formation in Kunming, Yunnan Province, southwestern China. The establishment of this species is based on detailed morphologic and cuticular investigations. The fossil leaves are elliptic, with serrate margins on the apical half. The primary venation is pinnate, and the major secondary venation is craspedodromous. The tertiary veins are opposite or alternate-opposite percurrent with two branches. The stomata are anomocytic, occurring only on the abaxial epidermis. The trichome bases are unicellular or multicellular. The new fossil species shows the closest affinity with the extant Q. delavayi and the late Miocene Q. praedelavayi Y.W. Xing et Z.K. Zhou from the Xiaolongtan Formation of the Yunnan Province. All three species share similar leaf morphology, but differ with respect to trichome base and stomatal densities. Q. tenuipilosa, Q. praedelavayi, and Q. delavayi can be considered to constitute the Q. delavayi complex. Since the late Miocene, a gradual reduction in trichome base density has occurred in this complex. This trend is the opposite of that of precipitation, indicating that increased trichome density is not an adaptation to dry environments. The stomatal density (SD) of the Q. delavayi complex was the highest during the late Miocene, declined in the late Pliocene, and then increased during the present epoch. These values show an inverse relationship with atmospheric CO2 concentrations, suggesting that the SD of the Q. delavayi complex may be a useful proxy for reconstruction of paleo-CO2 concentrations