植物根瘤内Frankia生物多样性的研究

建立了一种简捷、快速植物根瘤内痕量FrankiaDNA的提取方法，经过东北的沙棘、色赤杨、毛赤杨和云南的冬赤杨根瘤的瘤内痕量FrankiaDNA及体外培养的Frankia菌株DNA提纯，并用于酶切和PCR，获满意结果.首次应用RAPD（RandomAmplifiedPolymorphicDNA）与ARDRA（AmplifiedRibosomalDNARestrictionAnalysis）方法，直接扩增中国云南、东北地区赤杨属三种植物和沙棘属一种植物根瘤内的FrankiaDNA，所获指纹图谱揭示了其丰富的生物多样性.研究结果显示，与同属不同种植物（Alnus.tinctoriaSarg和Alnus.hirsuta）结瘤的Frankia，可有相同指纹图谱;同种植物（Alnus.nepalensisDon或Hippophae.rhamnoides）瘤内的Frankia指纹图谱可明显不同.瘤内Frankia有丰富的生物多样性，并且这种Frankia多样性可能与样品采集地点、地势、海拔高度等有关.

Multi-proxy records of Two-Yurts Lake

Within the scope of Russian-German palaeoenvironmental research, Two-Yurts Lake (TYL, Dvuh-Yurtochnoe in Russian) was chosen as the main scientific target area to decipher Holocene climate variability on Kamchatka. The 5x2 km large and 26 m deep lake is of proglacial origin and situated on the eastern flank of Sredinny Ridge at the northwestern end of the Central Kamchatka Valley, outside the direct influence of active volcanism. Here, we present results of a multi-proxy study on sediment cores, spanning about the last 7000 years. The general tenor of the TYL record is an increase in continentality and winter snow cover in conjunction with a decrease in temperature, humidity, and biological productivity after 5000-4500 cal yrs BP, inferred from pollen and diatom data and the isotopic composition of organic carbon. The TYL proxy data also show that the late Holocene was punctuated by two colder spells, roughly between 4500 and 3500 cal yrs BP and between 1000 and 200 cal yrs BP, as local expressions of the Neoglacial and Little Ice Age, respectively. These environmental changes can be regarded as direct and indirect responses to climate change, as also demonstrated by other records in the regional terrestrial and marine realm. Long-term climate deterioration was driven by decreasing insolation, while the short-term climate excursions are best explained by local climatic processes. The latter affect the configuration of atmospheric pressure systems that control the sources as well as the temperature and moisture of air masses reaching Kamchatka.