“Little Ice Age”(LIA)was first introduced by Matthes in 1939 with reference to the phenomenon of cirque glacier regrowth during the Holocene.China is located in the Asian monsoon region,and monsoon circulations on ecological environment have a variety of effects on ecological environment during the LIA.However,existing research has little documented on environmental changes based on pollen during the LIA.A 100-cm-deep section of drilling was collected at the Kanas wetland,northern Altay.By using the data of pollen and^14C,we obtained vegetation types from the study area,which will providenew evidence of“Little Ice Age”in the Altay area.
To provide information on vegetation patterns and altitudinal distributions of pollen assemblage in surface soil layers,their complicated relationships in a dryland mountain-basin system in northwestern China and a realistic basis for paleovegetational reconstruction,we investigated 86 vegetation quadrats and analyzed 80 soil samples from the surface soil layers along an altitudinal transect on the north slope of the Middle Tianshan Mountains from alpine cushion vegetation at 3,510 m near glacier to desert vegetation at 460 m in the Gurbantunggut Desert.According to surface pollen assemblages and the results of the detrended correspondence analysis,the transect can be divided into six major altitudinal pollen zones as alpine cushion vegetation,alpine and subalpine meadows,montane Picea forest,forest-steppe ecotone,Artemisia desert and typical desert,which basically reflect the characteristics of the mountainous vegetation patterns on the north slope of the Middle Tianshan Mountains.However,Picea pollen also exists outside the spruce forest,Chenopodiaceae and Artemisia pollen appeared above the elevation of 1,300 m,indicating that most of them might be introduced from lower elevations by upslope winds.Airborne pollen researches from three regions at different elevations further suggest that a high-frequency northwest anabatic wind has a remarkable influence on the transportation and dispersion of surface pollen in the area.
YANG ZhenjingZHANG YunREN HaibaoYAN ShunKONG ZhaochenMA KepingNI Jian
Objective Betula microphylla Bunge, as a resource treasury of desert biodiversity, is a pioneer plant in saline-alkaline soil amelioration. According to previous research, Ebinur Lake, north Xinjiang, is a representative saltwater lake with 92–131 g/L salinity(Li et al., 2006).
LI YumeiZHAO LongJIANG HanchaoZHANG YunKONG Zhaochen
Aims climate change can significantly affect the vegetation worldwide.thus,paleovegetation and paleoclimate reconstruction should consider the quantitative relationship between modern vegetation and climate.the specific objectives of this study were(i)to assess the influence of environmental variables on pollen assemblages in the Kanas region,(ii)to reconstruct the evolution of vegetation over the past 3000 years using pollen records and(iii)to quantify historical climate change(including mean annual temperature and total annual precipitation)using a weighted averaging partial least squares regression method(WAPLS)applied to fossil pollen data from the Kanas wetland in Xinjiang,china.Methods A total of 65 surface and 50 fossil samples were collected from the Kanas wetland and analysed for 14c,pollen and grain size.By com-bining these data with those obtained from 214 samples of surface pollen assemblages in north Xinjiang,the late Holocene climate was reconstructed using a WAPLS model.Important Findingsthe vegetation in Kanas was dominated by forest for the past 3000 years,undergoing an arbour-vegetation transition from predominantly pine to spruce over that period.the WAPLS model showed that the paleoclimate progressed from cold-wet to warm-dry and subsequently back to cold-wet.Prior to 1350 calibrated years before the present(cal.yr BP),the climate of Kanas was cold and wet,and conditions became increasingly warm and dry until 870 cal.yr BP.the temperature reconstruction model indicated that a‘Little Ice Age’occurred~380 cal.yr BP.these data will help us improve the understanding of abrupt climate change and provide important information regarding the prediction of climate.
As the resource treasury of desert biodiversity, thewetland of Betula halophila has fragile ecologic systemand low stability, which causes the sudden reduction ofwetland area. The Alahake Saline Lake is known for anendangered species, Betula halophila. However,palaeoecology changes of the Alahake Saline Lake havebeen little documented.
