Population Ecology Of Three Rare Tree Species Protected By National Law In South Jiangsu

Population is the link of communities and ecosystems. Studies on population structure, population dynamics and distribution patterns, as an essential part of plant population, can reveal the changing rules along with time and space, can predict their development trends, and can reflect the correlation between populations and their environments.The southern part of Jiangsu Province with excellent geographical conditions is the major distribution areas of rare plants species. According to the key protected wild plants survey for the second time of Jiangsu Province in recent years, there were five rare and endangered plant species which were listed as national protected plants in this region. In order to reveal the population structure, population dynamics and distribution patterns, three of them were selected as objective trees. Then their population ecology research was conducted by making plots in the wild. Particularly, Parrotia subaequalis is taken as the first class wild species protected by national law in China while Zelkova schneideriana and Cinnamomum camphora are taken as the second class ones.Parrotia subaequalis is endemic to East China. In order to reflect the characteristics of its wild populations deeply, the plots (50 m×50 m) were established for Mt. Longwang in Anji County, Zhejiang Province and Mt. Wanfo in Shucheng County, Anhui Province respectively. However, the plot (30 m×30 m) was established for Mt. Dalongxikan in Yixing County, Jiangsu Province due to human influence. The point pattern analysis was applied to analyze their spatial patterns at different scales, and the difference was analyzed on population structure, population dynamics and distribution pattern across the three sites. The plot (30 m×40 m) of Zelkova schneideriana population for Longtan in Liyang County and the plot (40 m×50 m) for Shijiashan in Jintan County were established respectively, to analyze the population ecology characteristics and their differences of this species in the sampled areas. The Cinnamomum camphora population plot (40 m×40 m) was established at a hillside of Piaomiao Village in Xishan Scenic Spot to carry out the population ecology of this species.According to the field survey and statistical analysis, the main results were as follows:(1) The populations structure:For the three Parrotia subaequalis populations (Mt. Longwang, Mt. Wanfo, Mt. Dolongxikan), Zelkova schneideriana population of Longtan in Liyang and Cinnamomum camphora population of Piaomiao Village in Xishan Scenic Spot, the individual number of sapling and young trees was the most, adult trees came second, old trees was the fewest, and all of the populations showed an inverse J-shaped size class distribution. Therefore, for the three tree species, the overall population structures were of increasing type. However, for Zelkova schneideriana population of Shijiashan in Jintan, the individual number of old trees was the most, adult trees took second, sapling and young trees was the fewest. Accordingly, this population was a typical declining population.(2) Dynamics of population numbers:For Mt. Dalongxikan, the expected longevity (ex) gradually increased from class Ⅰ to Ⅳ, decreased from class Ⅳ to Ⅸ. The mortality rate (qx) and vanishing rate (Kx) of class Ⅰ-Ⅲ were higher than other size classes. The mortality rate increased from class Ⅳ to Ⅷ, a maximum value reached at class Ⅱ, the vanishing rate increased from class Ⅳ to Ⅸ, reaching a maximum value at class Ⅸ. The population survival rate decreased with increased DBH, survival curve accorded with Deevey Ⅲ type. However, the populations of Mt. Longwang and Mt. Wanfo had a different trend from Mt. Dalongxikan. The expected longevity decreased with increased DBH. The mortality rate and the vanishing rate increased from class Ⅰ to Ⅶ. The population survival rate also decreased with increased DBH, survival curve accorded with Deevey Ⅱ type.For the Zelkova schneideriana population of Longtan in Liyang, the expected longevity increased first, and then decreased with increased DBH, reaching a maximum value at class Ⅱ. The mortality rate decreased with DBH, the vanishing rate decreased from class Ⅰ to Ⅳ, then increased from class Ⅳ to Ⅴ, reaching a maximum value at class Ⅳ for the mortality rate, and at class Ⅴ for the vanishing rate. The population survival rate also decreased with increased DBH, survival curve accorded with Deevey Ⅲ type. However, for the population of Shijiashan in Jintan, the expected longevity decreased with increased age classes, except for a slight increase for class Ⅲ. The mortality rate and vanishing rate were increased with increased DBH. The population survival rate also decreased with DBH, survival curve accorded with Deevey Ⅱ type.For Cinnamomum camphora population from Piaomiao Village in Xishan Scenic Spot, the expected longevity decreased from class Ⅰ to Ⅳ, and then increased from class Ⅳ to Ⅴ, reaching a maximum value at class V. The mortality rate increased from class Ⅰ to Ⅳ, and the vanishing rate increased from class Ⅰ to Ⅴ. The population survival rate decreased with increased DBH, survival curve accorded with Deevey Ⅱ type.(3) Spatial pattern of populations:The Parrotia subaequalis populations (Mt. Longwng, Mt. Wanfo, Mt. Dolongxikan), the Zelkova schneideriana population of Shijiashan in Jintan and Cinnamomum camphora were all showed clumped distributions at different scales. However, the Zelkova schneideriana population of Longtan in Liyang showed clumped distribution at scales (1 m-4 m), with random distribution at other scales(4m-15 m).The research of population structure of three rare tree species protected by national law in South Jiangsu showed that with the exception of Zelkova schneideriana population of Shijiashan in Jintan being a typical declining population, others were of increasing type. For Parrotia subaequalis, the stamens become mature earlier than its pistils, leading to hampered pollination, and this caused it difficult to regenerate in the wild. Additionally, anthropogenic disturbance, in the form of stealing, picking up branches and trampling from tourists have shrunk the distribution area. Zelkova schneideriana populations are widely distributed in South Jiangsu, similarly, anthropogenic disturbance, in the form of quarrying, building of the road have made damage to this species to some extent. Reproduction by sprouting and self-thinning made a significant impact in the growth and development of Cinnamomum camphora. For dynamics of population numbers, the three species mainly belonged to Deevey Ⅱ and Deevey Ⅲ. The mortality of young trees of Z. schneideriana population of Longtan in Liyang and P. subaequalis population of Mt. Dolongxikan in Yixing were higher than others, survival curve accorded with Deevey Ⅲtype. However, the rest of populations had the same mortality, accorded with Deevey Ⅱ type. For spatial pattern of populations, with the exception of Z. schneideriana population of Xianrendong in Liyang showed random distributions at scales (4 m-15 m), the others were all showed clumped. The reproduction by sprouting occurred in the three rare and endangered tree species. The south of Jiangsu Province has had considerable human activities, though it has excellent geographical conditions. The wild rare and endangered tree species in this region suffer a serious threat in population growth and expansion. Therefore, all efforts that can protect suitable habitats of these species should be made to increase the population size and distribution area.