Zhenju Chen

Changes of main secondary metabolites in leaves of Ginkgo biloba in response to ozone fumigation

To investigate the effect of elevated O3 on the accumulation of main secondary metabolites in leaves of Ginkgo biloba L., four-year-old trees were exposed in open-top chambers with ambient air and the air with twice ambient O3 concentration in Shenyang in 2006. Elevated O3 increased the concentrations of terpenes, but decreased the concentrations of phenolics in G. biloba leaves. The results showed that secondary compounds from G. biloba leaves responded to the elevated O3 exposure in a different way when compared to previous studies which showed elevated O3 increased the concentrations of phenolics but had no effect on the terpenes in leaves of other deciduous trees. Furthermore, reduced synthesis of phenolics may decrease the resistance of G. biloba to O3 and other environmental factors. On the other hand, the induced synthesis of terpenes may enhance the antioxidant abilities in G. biloba leaves at the end of O3 fumigation.

Solar activity, global surface air temperature anomaly and pacific decadal oscillation recorded in urban tree rings

A tree ring width chronology developed from 58 samples taken from Chinese pine trees (Pinus tabulaeformis Carr.) growing in Shenyang city was studied to analyze the effects of solar activity, Global Surface Air Temperature Anomalies (GSATA) and the Pacific Decadal Oscillation (PDO) on annual radial growth. An excellent response of tree rings to solar activity and global environmental change was revealed, indicating that these urban Chinese pine trees are a suitable proxy for Sun-Earth system research despite their location in Shenyang, an industrial city. The information derived from annual growth rings of urban Chinese pine trees coincides with records from undisturbed trees in a natural location, and demonstrates significant synchronous response to solar activity in the periodic bands of 5–8, 10–12 and 20–30 years. The wave signal of tree growth was also affected and amplified by the combined effect of the PDO from 1900 to 2004 and GSATA from 1880 to 2004 with a short lag time, revealing 5–8, 11–13, and 20–23 year oscillatory modes. At 20–30 year timescale, Chinese pines validated the strong GSATA influence signal at 20.8 years, and may be the primary cause of the 20 and 23 year periodic waves of tree rings. Shenyang urban tree ring growth also showed high frequency variation (2—4 y) that may be due to low periodicity of solar activity, GSATA, PDO and local climate variations, especially in the 2–4 years band width.RésuméUne chronologie de largeur de cernes a été développée à partir de 58 échantillons prélevés sur des pins chinois (Pinus tabulaeformis Carr.) poussant dans la ville de Shenyang, afin d’analyser les effets de l’activité solaire, de l’anomalie globale de surface de la température de l’air (GSATA) et de l’Oscillation Pacifique décadaire (OPD) sur la croissance radiale. Cette étude a révélé une forte corrélation entre croissance des cernes et activité solaire d’une part, et changement global de l’environnement d’autre part, indiquant que ces pins urbains permettent des études sur les relations Soleil — Terre, malgré leur localisation dans une ville industrielle comme Shenyang. L’information dérivée de la croissance annuelle des cernes coïncide avec des enregistrements sur des arbres non perturbés dans un environnement naturel. De plus elle révèle une réponse significative synchrone avec l’activité solaire avec des périodes de 5–8, 10–12, et 20–30 ans. Le signal de vague de croissance des arbres a été aussi affecté, amplifié par l’effet combiné d’OPD de 1900 à 2004 et de l’anomalie globale de 1880 à 2004 avec un temps de latence réduit, et des modes d’oscillations de 5–8, 11–13 et 20–23 ans. À une échelle de temps de 20–30 ans, les pins chinois ont validé la forte influence du signal de l’anomalie globale à 20,8 années. L’anomalie globale peut être la cause primaire des 20 et 23 années de vagues périodiques des cernes des arbres. La croissance des cernes des arbres urbains de Shenyang a aussi montré une variation importante de fréquence de 2–4 ans qui est peut-être due une faible périodicité de l’activité solaire, de GSATA, de PDO et à des variations climatiques locales, en particulier dans une période de temps de 2–3 ans.

The effect of anthropogenic activities on the reduction of urban tree sensitivity to climatic change: dendrochronological evidence from Chinese pine in Shenyang city

To understand how urban tree growth has responded to the accelerating expansion in population and urbanization, an understanding of the tree-climate–urban ecosystem relationship is necessary. To this end, a metropolitan, suburban, and rural forest stand in and near Shenyang; and a rural forest stand in Weichang, were sampled in southern Northeast China. Radial growth variability of 109 Chinese pines (Pinus tabulaeformis Carr.), established before 1900 within and around the city, was measured. The contents of trace elements in tree rings were also examined to detect the possible relationship to urban environmental contamination. All sampled trees crossdated well, indicating a homogeneous common influence of regional climate. For the common period of 1901–2000, the radial growth of all trees was significantly affected by local and regional climate, especially temperature and precipitation in winter and spring, respectively. From the rural to the metropolitan areas, a significant decreasing relationship in the response of trees to climatic factors was detected. These decreases occurred over time and in tree stands within the same location or between different sites, and also corresponded with the increasing influence of local urbanization and industrialization on the urban environment during the last century. Particularly strong influences are the increase of population, urban built-up area, and urban agricultural and industrial activities. Decreases in mean sensitivity of Chinese pines were also found and are most likely related to the intensification of anthropogenic activities and environmental change. Based on tree-ring width growth in rural areas, a growth pattern of urban trees without anthropogenic disturbances was established. After removing the climate-related signals from actual urban tree growth, the impact of anthropogenic disturbances was chronologically developed. The results indicate that the periods of heaviest disturbances occurred from 1914 to 1922, 1932 to 1935, 1943 to 1946, 1955 to 1969, and 1973 to 2000.

Microwave Fine Structures in the Initial Phase of Solar Flares and CMEs

Solar radio fine structures (FSs) may be as an important diagnostics stool to draw the evolution map of the flare loop in the initial phase of solar flares. Also, it may be an important signature of the initial phase of CMEs. Here we analyzed a series of solar radio bursts with drift pulsation structures (DPS) and FSs during the former part of the 23rd solar activity cycle. Found they were associated with CMEs, and got some important statistic conclusions.