| The purpose of this study was to explore the changes and migration of Juniperus rigida Sieb.et Zucc.in the suitable areas across China under the background of global warming,and to clarify the chemical composition differences in different suitable areas and their responses to environmental factors.Based on data collection,field investigation and laboratory analysis,the Arc GIS,fragstats and Maxent model were used,we projected the potential distribution of J.rigida under current and future climate secanrio,analyzed the effect of climate change on the potential distribution area,landscape fragmentation and the migration path.The result can reveale the dominant ecological factors influencing the distribution of J.rigida.We analyzed the diversity of chemical components,elaborated the differences of J.rigida among samples,and clarified the influence of the dominant factors on the content of needles polyphenols and essential oil.The achievements can provide theoretical support for the habitat protection of J.rigida resources.The main results are as follows:(1)It was mainly distributed in the northeast,north and northwest of China,with loess Plateau and Inner Mongolia Plateau as the main distribution areas under the current climate scenario.The core suitable area covers an area of 101298.01 km~2,accounting for about 1.11%of the total state area.The total of the core suitable area in Inner Mongolia,Hebei,Shanxi and Jilin provinces accounts for about 80.00%of the total area of the core suitable area.the dominant ecological factors,affecting the distribution of J.rigida,were slope(Slo),altitude(Alt),mean temperature of driest quarter(MTDq)and temperature annual range(TAR).(2)With the climate warming,the area of suitable showed increasing firstly and then decreasing under the four RCPs scenarios.The RCP2.6 scenario,the temperature increase1.4?,was beneficial to the diffusion of the suitable area of J.rigida and the aera stabilized at about 960,000 km~2.The distribution decreased sharply under RCP8.5,which was charactered by the most obvious warming,and the area decreased by 11.39%compared to that of the current habitat.In general,the centroid of the distribution area moved to high altitude.The centroid migrate farther under the RCP8.5.(3)Under the influence of climate warming,the area of the ecological sensitive area will remain at 38,000?40,000km~2 in the 2050s and 2070s under the RCP2.6,RCP4.5 and RCP6.0,moreover,the ecological critical area remain at about 60,000km~2.Under the RCP8.5 scenario,the ecologically critical area reduced to 42,000 km~2,the loss mainly concentrated in two regions,the southern segment of Changbai Mountain in Liaoning province and the Loess Plateau region including Helan Mountain in Ningxia,Taihang and Luliang Mountain in Shanxi Province,Yinshan Mountain in Inner Mongolia and Yanshan Mountain in Hebei province.(4)Under current and future climate conditions,the moderate fragmentation area of the suitable habitat accounted for about 60%of all suitable region.The highly fragmented regions were mainly concentrated in the norther of shaanxi province,the Ordos plateau of the southwest of Daqingshan mountain and the zhangjiakou region of the east of Daqingshan mountain in Inner Mongolia in Inner Mongolia,and the area tend to expand under RCP8.5.(5)The results,obtained by diversity analysis of the main chemical components of juniper of the diversity analysis of the main chemical components of J.rigida,showed that the content of phenolic compounds and essential oil components varied greatly among different types of suitable areas.The clustering analysis was performed on the sample sites based on the phenolic compounds and essential oil content.The results showed that the central Shaanxi species source,located in general suitable region,had a high content of haematoxylin and the essential oil composition was mainly heterogeneous.The northern Shaanxi species source,situated in core suitable region,were charactered by the high content of chlorogenic acid and esters aromatic substances.Northeastern seed source,located in a moderate suitable region,had low total phenolic content and predominantly alkene-based essential oil composition.The result also showed that the North China seed source is located in the core fitness zone,with high contents of spicebush biflavones,mangosteen flavonoids and kaempferol,and the essential oil composition is mainly alkene-like.(6)The results of the correlation analysis and the sequencing analysis between the content of phenolic compounds,ensstial oils and the ecological factors showed that the precipitation of wettest month(PWm),relative humidity(RH),isothermality(Iso),soil total organic matter(TOC)and soil available nitrogen content(Av N)were the main factor affecting the phenolic content.The results also showed that the isothermality(Iso),precipitation of wettest month(PWm),soil total nitrogen content(TN)and total organic matter(TOC)and soil p H(p H)were the main factor and affecting the content of enssential oils. |
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