Studies on Ecological Monitoring of Plant Community and Plant Diversity in Shenzhen, Southern China

From Jan. 2013 to Nov. 2018, we carried out the investigation on vegetation studies in the ecological monitoring programs, Shenzhen and totally researched 170 plant communities of mountain areas etc., few areas of street regions and parks etc., for communities’ structural characteristics and plant diversity. We comparatively analyzed natural forests, semi-natural forest and artificial forest composition and structural characters and family, genus and species diversity level and the main affected factors. We also researched and analyzed these communities’ structural characteristics and pant diversity, comparatively analyzed natural forests, semi-natural forest and artificial forest composition and structural characters and family, genus and species diversity level, the main affected factors;researched and analyzed the relationship between plant community structure characteristics with the absorbing ability to PM2.5 pollutants. The result showed that the structure and plant diversity of natural forest were obviously better than artificial disturbed forest or artificial forest, the semi-natural forest was the middle level of the forests, In the indices of height, DBH, coverage and crow width etc. of tree layer, natural forests and semi-natural forests were obvious higher than that of artificial disturbed forest or artificial forest;in some forests of artificial disturbed forest or artificial forest, though their richness indices of family and genus were a slightly higher, but this contribution was majorly due to herb layer plants, and some shrub layer plants. Analyzing three kinds of communities, the number of tree layer species of natural forest was the largest, and their every α-diversity index value was the highest;these characteristics values of semi-natural forest were second, artificial disturbed forests or artificial forests were the lowest;in shrub layer, and herb layer, few α-diversity indices of artificial disturbed forest or artificial forest were a slightly higher than that of some natural forests, but the integral values of the diversity indices of natural forest and semi-natural forest were obviously higher than the former. The research showed that in the artificial disturbed forest or artificial forest, because there have some little scale clearing areas, so some pioneer plant species could enter the community and formed a temporarily increase of species diversity, however, these species major were some shrub and herb plants;but tree layer possessed obviously more, even surpassed several ten times biomass than shrub and herb layers. Therefore, the respects of maintain ecosystem stability and other ecological efficient have major and dominated position and so on;and then this community can be natural recovery and succession, those forementioned new entire plants shall withdraw from the community and are replaced by the original plants of the community;but this process has already caused the ecological efficient loss and ecosystem unstable. Above research results are better evidence and theory reference to the argument problems on that are natural forest and natural restoration forest biodiversity higher? or is artificial forest biodiversity higher? and or is more artificial disturbed forest higher? Our researches showed that used random investigation method set quadrats, and combined typical investigation method, the structural indices in the all layer of community and all diversity indices of tree, shrub and herb layers and the integral values were similar, same or usually these indices in the community which set 600 m2, 800 m2 total quatrat area were higher (α-diversity) than that of more than 3000 m2, 4000 m2 or 7000 m2, even more than 17,000 m2 total quadrat area of communities. These lots of researches further proved that according to minimum area method for vegetation survey, in subtropical region, using random investigation method combined with typical investigation set 400 m2 or 400 m2 - 500 m2 total quad

Study on Plant Diversity of Mountain Areas of Yangmeikeng and Chiao, Shenzhen, China

In this study, Yangmeikeng mountain area with a long-term natural restoration status (communities 1, 2, and 3) and Chiao mountain area with an artificially disturbed status (communities 4 and 5) in Shenzhen in China were subjected to plant community composition and diversity statistical analysis on the basis of the following indices: plant height;density;tree layer DBH;coverage;number of family, genus, and species;calculated diversity indices;richness;similarity coefficients of family, genus and species;and species evenness. The diversity levels of each index in each community were compared, and the relationships of family, genus, and species in the communities with one another were determined. The integrated diversity levels in the two areas were also analyzed. Results showed that the composition status of three communities, especially communities 2 and 3, which were located at high elevation, in Yangmeikeng with the long-term natural restoration status was better. The diversity values were also evidently higher. The vegetation composition in Yangmeikeng was also greater than that in Chiao. The integration status of numerous diversity indices, such as evenness and richness, was higher than that of the latter. These data could be used as a basis for arguments regarding the status of natural and artificial forest biodiversities. Many species in the community in artificial forests were shrubs and herbs. The richness and proportion of tree species were distinctly low. Thus, shrubs and herbs were the main components of the artificial interference community. The number and richness of the tree species in natural or long-term natural restoration forests were higher than those of the former. The family diversity Df of the three communities in Yangmeikeng was slightly lower than that of the two communities in Chiao. By contrast, the genus diversity Dg, family richness, and genus richness in Yangmeikeng were higher than those in Chiao. In terms of α-diversity and similarity coefficient, family, genus, and species were not directly related to one another. Therefore, species, genus, and family composition should be combined with their diversity status in the statistical and biodiversity analysis of a community. Synthetic diversity indices should be further analyzed to evaluate the diversity status of a community objectively.

The Relationship between Plant Community Structure and Their Ability to Absorb and Subtract PM_(2.5)

The research aimed to study absorption and reduction of PM_(2.5)by different plant community structure,and explore which plant community can have better or best comprehensive absorption efficiency,thereby improving and optimizing urban vegetation structure,further promoting improvement of urban air quality,improving people's quality of life,and ensuring a good living environment.In this paper,the method of quadrat survey commonly used in field survey was adopted to record the height,coverage,DBH and other indicators of statistical plants,and corresponding comprehensive value was calculated through these indexes.PM_(2.5)was measured at forest edge,4 and 8 m in the forest,with three repetitions.Subtraction amount of PM_(2.5)determined at different layers was analyzed,as well as its relationship with comprehensive value of community structure.The results showed that PM_(2.5)amount decreased significantly at forest edge,4 and 8 m in the forest,and better community structure had a positive effect on PM_(2.5)absorption.The higher the comprehensive indexes of community structure such as plant height,DBH(arbor),density and coverage,the better the ability of absorbing and reducing PM_(2.5).Therefore,it must pay attention to the diversity of plant species per unit area,to build a good plant community structure,which could better improve structure of local ecosystem,and play a good role in absorbing and reducing PM_(2.5)pollutants in the atmosphere.

Iodine speciation in aerosol particle samples collected over the sea between offshore China and the Arctic Ocean

Iodine species collected by an onboard PM10 particle sampling system during the Second Chinese National Arctic Research Expedition （July-September 2003） were measured using inductively coupled plasma mass spectrometry and ion chromatography-inductively coupled plasma mass spectrometry. Iodine （I^-） was detected in all samples over the Arctic Ocean, whereas additional iodine species including insoluble iodine, soluble organic iodine plus I were detected over the northwestern Pacific Ocean. The results suggest that the main form of iodine is different within the Arctic Ocean than it is outside. Enrichment factor values showed moderate enrichment of iodine in the northwestern Pacific, whereas a high enrichment factor was found in polar regions, implying sources other than sea salt. A potential explanation was ascribed to the role of sea ice melt in the Arctic and rapid growth of algae in seawater, which enhances the production of iodocarbon and air-sea exchange. This was confirmed by the larger values of total iodine in 2008 than in 2003, with greater sea ice melt in the former year. In comparison with earlier reports, ratios of iodate to iodide （IO3^-/I^-） were much smaller than 1,0. These ratios were also different from modeling results, implying more complicated cycles of atmospheric iodine than are presently understood.

Methanesulphonic acid in aerosols along a cruise path from China to the Arctic Ocean: Spatial and temporal distributions and link with iodine

Methanesulphonic acid（MSA） may play an important role in the climate change occurring in response to the warming of the Arctic Ocean. However, the spatial and temporal distributions of MSA in this region are poorly understood. We report on the MSA content of aerosols over oceans measured during the 3rd Chinese National Arctic Research Expedition（CHINARE2008） from July to September, 2008. Results show that the aerosol MSA content can be influenced by multiple processes in different areas. In coastal regions, airborne pollutants, especially nitric oxide, may strongly influence the oxidation of dimethyl sulfide（DMS） and increase the concentration of aerosol MSA. In remote areas of the Pacific and Arctic oceans, changes in plankton will indirectly influence the airborne MSA concentration. Moreover, we found fairly similar trends in the variation of the concentrations of total iodine（TI） and MSA in the Arctic during CHINARE2008, suggesting that iodine and MSA may come from similar sources in the Arctic. Compared with the findings from other two cruises, CHINARE1999 and CHINARE2012, we found that sea ice is an extremely important factor that influences the aerosol MSA content in the Arctic. In addition, MSA concentrations may increase in the Arctic in the future caused by sea ice melting due to global warming.

Observation on the aerosol and ozone precursors in suburban areas of Shenzhen and analysis of potential source based on MAX-DOAS

Long-term stereoscopic observations of aerosol,NO2,and HCHO were carried out at the Yangmeikeng(YMK)site in Shenzhen.Aerosol optical depths and NO2 vertical column concentration(NO2 VCD)derived from MAX-DOAS were found to be consistent with other datasets.The total NO2 VCD values of the site remained low,varying from 2×10^(15)to 8×10^(15)mol/cm^(2),while the HCHO VCD was higher than NO2 VCD,varying from 7×10^(15)to 11×10^(15)mol/cm^(2).HCHO VCD was higher from September to early November than that was from mid-late November to December and during February 2021,in contrast,NO2 VCD did not change much during the same period.In January,NO2 VCD and HCHO VCD were both fluctuating drastically.High temperature and HCHO level in the YMK site is not only driving the ozone production up but alsomay be driving up the ozone concentration as well,and the O_(3)production regime in the YMK site tends to be NOx-limited.At various altitudes,backward trajectory clustering analysis and Potential Source Contribution Function(PSCF)were utilized to identify possible NO2 and HCHO source locations.The results suggested that the Huizhou-Shanwei border and the Daya Bay Sea area were the key potential source locations in the lower(200 m)and middle(500 m)atmosphere(WPSCF>0.6).The WPSCF valuewas high at the 1000maltitude whichwas closer to the YMKsite than the near ground,indicating that the pollution transport capability in the upper atmosphere was limited.

Integrating structure and function:mapping the hierarchical spatial heterogeneity of urban landscapes

Background:Cities are social-ecological systems characterized by remarkably high spatial and temporal heterogeneity,which are closely related to myriad urban problems.However,the tools to map and quantify this heterogeneity are lacking.We here developed a new three-level classification scheme,by considering ecosystem types(level 1),urban function zones(level 2),and land cover elements(level 3),to map and quantify the hierarchical spatial heterogeneity of urban landscapes.Methods:We applied the scheme using an object-based approach for classification using very high spatial resolution imagery and a vector layer of building location and characteristics.We used a top-down classification procedure by conducting the classification in the order of ecosystem types,function zones,and land cover elements.The classification of the lower level was based on the results of the higher level.We used an objectbased methodology to carry out the three-level classification.Results:We found that the urban ecosystem type accounted for 45.3%of the land within the Shenzhen city administrative boundary.Within the urban ecosystem type,residential and industrial zones were the main zones,accounting for 38.4%and 33.8%,respectively.Tree canopy was the dominant element in Shenzhen city,accounting for 55.6%over all ecosystem types,which includes agricultural and forest.However,in the urban ecosystem type,the proportion of tree canopy was only 22.6%because most trees were distributed in the forest ecosystem type.The proportion of trees was 23.2% in industrial zones,2.2%higher than that in residential zones.That information“hidden”in the usual statistical summaries scaled to the entire administrative unit of Shenzhen has great potential for improving urban management.Conclusions:This paper has taken the theoretical understanding of urban spatial heterogeneity and used it to generate a classification scheme that exploits remotely sensed imagery,infrastructural data available at a municipal level,and object-based spatial analysis.For effective planning and management,the hierarchical levels of landscape classification(level 1),the analysis of use and cover by urban zones(level 2),and the fundamental elements of land cover(level 3),each exposes different respects relevant to city plans and management.