Study On Different Juniperus Rigida Population Dynamics And Reproductive Characteristics Of Loess Plateau

Population Ecology is an important branch of ecology, and quantity changes, spatialdistribution as well as the relationship with the environment of the population including agestructure and dynamics, static life table and survival curve, spatial population distributionpatterns, relationships between and within species, population density adjustment and so onare its main research contents. The research on populations such as the quantity changes ofpopulation can increase and develop beneficial organisms while reduce and control pests so asto improve the environment and provide benefits for human being.Juniperus rigida is an evergreen trees or small trees in Cupressaceae Juniperus thatdistributed in a number of provinces, and the Loess Plateau is one of its main distributionareas. In order to provide a theoretical basis for the protection, sustainable use, resourcemanagement and recovery strategy of J. rigida populations in different regions of the LoessPlateau, the thesis selected five different populations in Wuchuan in Inner Mongolia, Zhuoluin Hebei, Hunyuan in Shanxi, Fugu in Shaanxi and Helanshan in Ningxia, and studied thepopulation structure and dynamics, reproductive characteristics as well as phenotypicvariation so as to reveal the survival status, genetic diversity and future developments of J.rigida populations in different regions of the Loess Plateau. The results are as follows:1. There were some differences among5populations of different regions in the structuresof diameter class, height class as well as crown width class, the populations ZL and HY wereyoung, while the populations WC and HL were relatively mature, and the population FGbelonged to ageing type. The survival curves of5populations of Juniperus rigida belonged totwo types, WC fitted in Deevey-III while the others belonged to Deevey-II on the whole. Withthe increase of age class, the killing powers of5different populations showed a similar trendof change to the mortality rates. Four survival functional curves of5populations showed that,the populations WC and FG reduced in young age, grew stably in middle age and declined inold age and FG showed a sharper reduction, while the populations ZL and HY had a steepreduction in early growth and a late recession, and the population HL reduced slightly inyoung age and recessed late as well.2. The distribution pattern of Helanshan was uniform while the other four populationswere uniform. The values of dispersion index I o f the five popolations all tend to1and the distribution patterns were all tend towards random with increasing quadrat scale., and theclustering intensities decreased with the growing age. In order to ensure the recovery anddevelopment of Juniperus rigida populations, the Juniperus rigida forests should be shieldedfrom interference and be well protected by the local government.3. The differences of the seed size among5regions were extremely notable, the seedfrom Wuchuan was the smallest and the seed from Fugu was the largest. With increasinglatitude and soil total phosphorus content, the length and aspect ratio of the seed becamesmaller, and the thousand-seed weight increased with increasing mean temperature in Januaryand July and decreased with the content of organic matter, available phosphorus and totalnitrogen of soil increased. There was a significant negative correlation between germinationand seed size. and seed germination rates. There were significant differences of germinationamong different regions, the seed germination of Wuchuan was the fastest and highest, andthat of Fugu was the slowest and lowest. Germination rate, germination energy andgermination index increased with increasing latitude, and germination energy and germinationindex increased with increasing soil total phosphorus content as well. Wuchuan and Hunyuanwere excellent provenances.4. There were significant differences in the cone length, cone width, cone length/conewidth and cone length×cone width among individuals within population, there weresignificant differences in the characters among populations except the seed width, seedlength/seed width and cone length/cone width. The variation among populations, that is themean phenotypic differentiation coefficient (Vst), was35.531%and smaller than that withinpopulation (64.469%), within populations variation mainly contributed to phenotypicvariation. Phenotypic characters were significantly correlated with latitude, average annualtemperature, January average temperature, July average temperature, and average rainfall.