Search Results (4)

The essential oils of Juniperus are highly beneficial medicinally. The present study aimed to assess the chemodiversity and bioactivity of Juniperus formosana, Juniperus przewalskii, Juniperus convallium, Juniperus tibetica, Juniperus komarovii, and Juniperus sabina essential oils from the Qinghai-Tibet Plateau. The results revealed 92 components in six essential oils: α-pinene (2.71–17.31%), sabinene (4.91–19.83%), and sylvestrene (1.84–8.58%) were the main components. Twelve components were firstly reported in Juniperus oils, indicating that the geographical location and climatic conditions of the Qinghai-Tibet Plateau produced the unique characteristics of Juniperus essential oils. The chemodiversity of Juniperus essential oils varied greatly, with J. sabina having the most recognized components (64) and the highest chemodiversity (Shannon–Wiener index of 3.07, Simpson’s diversity index of 0.91, and Pielou evenness of 0.74). According to the chemodiversity of essential oils, the six plants were decided into the α-pinene chemotype (J. formosana), hedycaryol chemotype (J. przewalskii, J. komarovii, J. convallium, J. tibetica), and sabinene chemotype (J. sabina). PCA, HCA and OPLS-DA showed that J. formosana and J. sabina were distantly related to other plants, which provides a chemical basis for the classification of Juniperus plants. Furthermore, bioactivity tests exhibited certain antioxidant and antibacterial effects in six Juniperus oils. And the bioactivities of J. convallium, J. tibetica, and J. komarovvii were measured for the first time, broadening the range of applications of Juniperus. Correlation analysis of components and bioactivities showed that δ-amorphene, β-udesmol, α-muurolol, and 2-nonanone performed well in the determination of antioxidant activity, and α-pinene, camphene, β-myrcene, as well as (E)-thujone, had strong inhibitory effects on pathogenic bacteria, providing a theoretical basis for further research on these components. Full article

Predicting the suitable habitat of plants under climate change has become a trending research topic in recent years. Juniperus tibetica Komarov (Cupressales: Cupressaceae) is a unique and vulnerable species on the Qinghai–Tibet Plateau (QTP) and the highest timberline in the Northern Hemisphere. The prediction of the suitable habitat of J. tibetica will be beneficial for understanding the ecosystem of the QTP. In the present study, variations in the distribution pattern of the suitable habitats (DPSH) of J. tibetica on the QTP were investigated by MaxEnt and GIS spatial analysis based on 288 distribution records and 8 environmental factors. The environmentally abnormal areas and environmental factors determining the DPSH along with climate change were analyzed, and the most suitable climate models were evaluated. The results show that the suitable habitat of J. tibetica will migrate to higher-elevation and -latitude areas in the future. Precipitation was the most important factor affecting current suitable habitats and limiting future ones, followed by temperature. By comparing the integrality of suitable habitat under different climate models, it was suggested that the HadGEM2-ES (RCP2.6) and BCC-CSM1.1 (RCP8.5) climate models were the best for predicting the DPSH of J. tibetica. This study revealed the response of the suitable habitat of J. tibetica relative to climate change at a large scale and provides a theoretical basis for the scientific management and conservation of J. tibetica resources on the QTP. Full article

Climate change is an important driver of biodiversity loss and extinction of endemic montane species. In China, three endemic Juniperus spp. (Juniperuspingii var. pingii, J.tibetica, and J.komarovii) are threatened and subjected to the risk of extinction. This study aimed to predict the potential distribution of these three Juniperus species under climate change and dispersal scenarios, to identify critical drivers explaining their potential distributions, to assess the extinction risk by estimating the loss percentage in their area of occupancy (AOO), and to identify priority areas for their conservation in China. We used ensemble modeling to evaluate the impact of climate change and project AOO. Our results revealed that the projected AOOs followed a similar trend in the three Juniperus species, which predicted an entire loss of their suitable habitats under both climate and dispersal scenarios. Temperature annual range and isothermality were the most critical key variables explaining the potential distribution of these three Juniperus species; they contribute by 16–56.1% and 20.4–38.3%, respectively. Accounting for the use of different thresholds provides a balanced approach for species distribution models’ applications in conservation assessment when the goal is to assess potential climatic suitability in new geographical areas. Therefore, south Sichuan and north Yunnan could be considered important priority conservation areas for in situ conservation and search for unknown populations of these three Juniperus species. Full article

Tree-rings are recorders of environmental signals and are therefore often used to reconstruct past environmental conditions. In this paper, we present four annually resolved, multi-centennial tree-ring isotope series from the southeastern Tibetan plateau. The investigation site, where juniper and spruce trees jointly occur, is one of the highest known tree-stands in the world. Tree ring cellulose oxygen (δ¹⁸O) and carbon (δ¹³C) isotopes were analyzed for a common period of 1685–2007 AD to investigate climate–isotope relationships. Therefore, various climate parameters from a local meteorological station and from the CRU 4.02 dataset were used. Tree-ring δ¹⁸O of both species revealed highly significant sensitivities with a high degree of coherence to hydroclimate variables during the growing season. The obtained δ¹⁸O–climate relationships can even be retained using a species mean. In contrast, the individual δ¹³C series indicated a weaker and non-uniform response to the tested variables. Underlying species-specific responses and adaptations to the long-term trend in atmospheric CO₂ bias even after a trend correction identified dominant environmental factors triggering the tree-ring δ¹³C at our site. However, analysis of individual intrinsic water-use efficiency in juniper and spruce trees indicated a species-specific adaptation strategy to climate change. Full article