| Forests perform their health functions by emission of Biogenic Volatile OrganicCompounds,BVOCSand through the environment characteristic of forests, which have an effecton people both physically and psychologically. At present, in landscape construction such as theconstruction of gardens or forestation, landscape effect is usually emphasized, while ecologicalservice functions, especially ecological health functions performed by gardens or plantcommunity or artificial vegetation system that is formed after afforestation are less emphasized.In our research,3typical forest communities in the Nanjing Purple Mountain (Liquidambarformosana community, Quercus acutissima community and Pinus massoniana+Osmanthusfragrans community), together with their respective main trees, Liquidambar formosana,Quercus acutissima and Osmanthus fragrans were studied. BVOCSemissions by3typical forestcommunities and3representative trees were sampled by headspace sampling method, and thesamples were analyzed with TCT-GC/MS. A systematic study was conducted on the type andcontent, dynamics (diurnal variation, monthly variation) of these emitted BVOCS, and inner linksbetween the variations and major environmental elements(light intensity, air temperature, relativehumidity) were studied in order to expose the emission laws of BVOCSby the three typical forestcommunities and their respective main trees, to present mathtiristic reference and serve as guidefor improving construction of landscape and urban forest. The result suggests that:1. The emission law of BVOCSby the three typical forest communities:â‘ There were somedifferences between the component of BVOCSin the3communities.38kinds of volatile organiccompounds were detected in the air of Liquidambar formosana community, dominant withterpenes, alcohols, ethers, aldehydes, ketones and alkanes. Terpenes and alcohols were larger inamount.47kinds of volatile organic compounds were detected in the air of Quercus acutissimacommunity, dominant with terpenes, alcohols, ethers, aldehydes, ketones, alkanes and phenols,among which alcohols, terpenes, ketones and alkanes were larger in amount.37kinds of volatileorganic compounds were detected in Osmanthus fragrans community.7types of volatile organiccompounds, terpenes, alcohols, ethers, aldehydes, ketones, alkanes and phenols were the maintypes. Alcohols and terpenes were larger in amount.â‘¡There were similarities between themonthly variation law of BVOCSin the3communities from May to December. The monthlyvariation laws of BVOCSin the air of Liquidambar formosana community and Quercusacutissima community were similar, both of which firstly showed a gradual increase in terpenes,alcohols, ethers, aldehydes, ketones and phenols, which reached the highest level in July, but the amounts showed a gradual decrease afterwards, while the monthly variation of alkanes showed agradual decrease first, and it reached the lowest level in July, and then it showed a gradualincrease. Monthly variation laws of BVOCSin Osmanthus fragrans community were special.Monthly variation laws of terpenes, alcohols, ketones, phenols and alkanes are the same as thoseof Liquidambar formosana community and Quercus acutissima community, while the monthlyvariation laws of ethers and aldehydes in the Osmanthus fragrans community were complicated.But the fluctuation laws were the same.2. Effects of3environmental elements of light intensity, temperature and humidity onBVOCs in a forest community were studied. Main results were as follows:â‘ There existed asignificant positive correlation between total BVOCScontent of main components in the air ofeach of the3typical forest communities and monthly average light intensity. There existed asignificant positive correlation between relative contents of terpenes, alcohols, ketones andphenols in the3typical forest communities and light intensity, while there existed a significantnegative correlation between relative contents of alkanes and light intensity. There also existed asignificant positive correlation between ethers and aldehydes in both Liquidambar formosanacommunity and Quercus acutissima community and light intensity. However, there existed nosignificant correlation between ethers and aldehydes in Osmanthus fragrans community and lightintensity.â‘¡There existed a significant positive correlation between total BVOCScontent ofmain components in Liquidambar formosana community and Osmanthus fragrans communityand monthly average temperature respectively while no such correlation was found with Quercusacutissima community. There existed a significant positive correlation between relative contentsof terpenes, alcohols, ketones and phenols in the3typical forest communities and temperaturewhile there existed a significant negative correlation between relative contents of alkanes andtemperature.There also existed a significant positive correlation between ethers and aldehydes inLiquidambar formosana community and Quercus acutissima community and temperature whilethere existed no significant correlation between relative contents of ethers and aldehydes in theair of Osmanthus fragrans community and temperature.â‘¢Exept in some cases with specialmoisure (a relative moisure content of71%), there existed a significant correlation between eachtype of BVOCScontent in Liquidambar formosana community and Quercus acutissimacommunity and humidity, and there existed a significant correlation between each type ofBVOCSexcept ethers and aldehydes in Osmanthus fragrans community and humidity. Moreover,there also existed a significant negative correlation between the total BVOCScontent of maincomponents in Liquidambar formosana, Quercus acutissima and Osmanthus fragranscommunity and monthly average humidity respectively.â‘£There existed compatible correlationlaw between major BVOCScomponents in both Liquidambar formosana community andQuercus acutissima community, that is to say, there existed a significant negative correlationbetween total alkanes and other types while there existed a significant positive correlationbetween other types of BVOCS. In general, there existed correlation between different types of BVOCSin Osmanthus fragrans community similar to those in Liquidambar formosanacommunity and Quercus acutissima community, but the correlation between some types ofBVOCSwas not significant.3. BVOCScomponent of3main trees in the3typical forest communities and their emissionlaws were studied, the main results were as follows:â‘ The types of components of BVOCSemitted by the3main trees were similar, but their dominant components were different. Amongthe BVOCSemitted by Liquidambar formosana, Quercus acutissima and Osmanthus fragran,terpenes, alcohols, ketones, ethers, aldehydes, alkanes, etc. were the major components. Amongthe BVOCSemitted by Liquidambar formosana, terpenes, alkanes, etc. were the majorcomponents. Among the BVOCSemitted by Quercus acutissima, ketones, terpenes and alcoholswere the major components. Among the BVOCSemitted by Osmanthus fragrans, alcohols,terpenes were the major components.â‘¡There was a marked diurnal variation in the majorBVOCScomponents emitted by the3main trees. Among the BVOCSemitted by Liquidambarformosana, the variation trend of terpenes is similar to the diurnal variation trend of temperature,with the highest level at noon and the lowest level in the morning or evening. The variation trendof ethers, alkanes, etc.is similar to the diurnal variation trend of humidity, with the lowest level atnoon and the highest level in the morning or evening. Alcohols and aldehydes were emitted in thelargest amount in the late afternoon, with1,6-Octadien-3-ol,3,7-dimethyl-and Benzaldehydebeing the major content. Among the BVOCSemitted by Osmanthus fragran, the diurnal variationtrend of Alcohols was consistent with the diurnal variation trend of temperature. The diurnalvariation law was: it gradually increased till about noon, then it gradually decreased. The diurnalvariation law of terpenes was: its content was the highest in the morning, then it graduallydecreased as temperature increased, but at around2:00p.m, it began to increase. The diurnalvariation law of ketones was: its content was the lowest in the morning, then it kept growing untilit reached the highest level in the late afternoon. The variation law of ethers was contrary to thatof ketones. The diurnal variation law of ethers was: its content was the highest in the morning,then it kept dropping until it reached the lowest level in the late afternoon. The emission trend ofaldehydes was consistent with the variation trend of humidity. The variation law of diurnalemission of aldehydes was: its content decreased first and then increased. Its content was higherin the morning than in the afternoon. The diurnal emission trend of alkanes, etc. was identical tothe variation trend of light intensity. The diurnal BVOCSemission law was contrary to that ofaldehydes. Its diurnal variation law was: it first increased and then decreased, and more wasemitted in the morning than in the late afternoon.â‘¢T here was a marked monthly variation in themajor BVOCScomponents emitted by the3main trees. The monthly variation trend of Terpenesemitted by Liquidambar formosana was consistent with that of temperature: it first increased andthen decreased. The monthly variation trend of alkanes, etc. was contrary to that of Terpenes.Their content was higher in May and November, but the lowest in August. In addition, theemission of ethers was rather low in August (could hardly be tested). Contents of other types of compounds were also low in every month. The monthly variation law of BVOCSemitted byOsmanthus fragrans was rather complicated. The monthly content of ethers was the highestamong all types of BVOCS. It was the highest in May and the lowest in October. The monthlyvariation trend of Alcohols was: it first increased and then decreased, and with the highestcontent in October and the lowest content in December. The monthly variation law of other typesof BVOCSwas rather complicated.The study results show that when an artificial ecological system is established or vegetationis reformed, it is feasible to improve its health functions with BVOCSthrough proper selectionand scientific arrangement of tree species. Due to limits of many factors, the conclusion of thisstudy is only a limited achievement at a certain stage and it is to be testified and improvedthrough more repeatable experiments in the future.
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