Characteristics of Soil Seed Bank and Natural Regenerations in Pinus densata Natural Forest of Southeast Tibet

Pinusdensata is one of the main constructive species for coniferous forests in southeast Tibet. P. densata forests are important water conservation forests in the drainage basins of the middle and lower reaches of Yalu Tsangpo River, Nyang River and Parlung Zangbo River. In this study, with P. densata forest distributed in southeast Tibet as research object, the seed rain, soil seed bank, seed germination and natural regeneration of P. densata were monitored and ana- lyzed by field investigation, located monitoring and indoor experimental analysis. The results showed that the average intensity of the seed rain of P. densata was 249.30±78.42 seeds/m2, in which the intensity of full seeds was 168.09±56.36 seeds/m2, the intensity of seeds damaged by worms was 41.11±20.25 seeds/m2, and the intensity of empty seeds was 40.10±21.04 seeds/m2. The intensity of the seed rain exhibited a single-peak trend of increasing at first and decreasing then over time. The spatial distribution patterns in the whole seed falling process and at different seed falling time all exhibited clumping distribution, and within in certain range, with the distance from the seed tree increasing, the diffusion intensity of the seed rain was weakened, exhibiting approximately normal distribution. In average density of P. densata seeds in the soil seed bank of P. densata was 231 seeds/m2, in which 62.77% of seeds were distributed in the litter layer, and 37.23% of seeds were distributed in the soil layer, and about 8% of seeds were lost during the pro- cess from seed rain to soil seed bank. Field sowing observation showed that the accumulated germination rate curve of P. densata fitted with Logistics equation y= 91.404/（1＋e66194.449）. The height structure, basal diameter structure and age structure of seedlings and young trees of P. densata were all of reverse ＂J＂ type, indicating good natural regeneration of P. densata. This study would provide a science basis for protection and resource management of P. densata, and further enrich the eval- uation content of national ecological safety curtain of the Tibet plateau.

Variations in electrical impedance and phase angle among seedlings of Pinus densata and parental species in Pinus tabuliformis habitat environment

Electrical impedance （El） and phase angle （PHI） parameters in AC impedance spectroscopy are important electrical parameters in the study of medical pathology. However, little is known about their application in variation and genetic relationship studies of forest trees. In order to test whether impedance parameters could be used in genetic relationship analysis among conifer species, E1 and PHI were measured in a seedling experiment test composed of Pinus tabuliformis, Pinus yunnanensis, and Pinus densata in a habitat of Pinus tabuliformis. The results showed that variations in both EI and PHI among species were sig- nificant in different electric frequencies, and the EI and PHI values measured in the two populations of P. densata were between the two parental species, P. yunnanensis and P. tabuliformis. These results show that these two impedance parameters could reflect the genetic relationship among pine species. This was the first time using the two AC impedance spectroscopy parameters to test the genetic relationship analysis between tree species, and would be a hopeful novelreference methodology for future studies in evolution and genetic variation of tree species.

Capacitance Characteristics of Pinus densata,Pinus tabuliformis,Pinus yunnanensis and the hybrids Pinus tabuliformis×Pinus Yunnanensis

We employed capacitance to evaluate the kinship and interspecific variation of homoploid hybrid conifer Pinus densata,P.tabuliformis,P.yunnanensis and artificial hybrids of P.tabuliformis(maternal parent)and P.yunnanensis(paternal parent)which were cultivated and selected in the common garden experiment.By measuring capacitance spectra under different voltage frequencies,we could differentiate different germplasms based on the electrical response.We aims to demonstrate that P.densata as the hybrid of P.tabuliformis and P.yunnanensis based on the capacitance values of the species,and to provide new evidence to the previously known biological evidence,as well as and the parental effect on the hybrids.Our results revealed that capacitance values between the species are significantly different in the spectra where P.yunnanensis positioned at the lowest and P.densata was much higher than all other species,indicating that P.densata had possessed a great capacity to store electrical energy.The capacitance spectra of P.densata and the artificial hybrid are not similar,which rejected our hypothesis.Both of the capacitance values of P.densata and the hybrids were closer to P.tabuliformis than to P.yunnanensis,which shows that the maternal influence was stronger than the paternal influence.Correlation analysis on the relationship between capacitance and fitnessrelated characteristics showed that capacitance is negatively correlated to mortality rate,and positively correlated with second-year survival rate.High capacitance values of P.densata and some of the hybrids reveal their superior adaptability to harsh environment in the Tibet Plateau.We concluded that capacitance as a new indicator for plant fitness and evolution evidence of homoploid hybrid conifers.

Interspecific Variation and Phylogenic Architecture of Pinus densata and the Hybrid of Pinus tabuliformis×Pinus Yunnanensis in the Pinus densata Habitat:an Electrical Impedance Spectra Perspective

We evaluated a novel and non-destructive method of the electrical impedance spectroscopy(EIS)to elucidate the genetic and evolutionary relationship of homoploid hybrid conifer of Pinus densata(P.d)and its parental species Pinus tabuliformis(P.t)and Pinus yunnanensis(P.y),as well as the artificial hybrids of the P.t and P.y.Field common garden tests of96 trees sampled from 760 seedlings and 480 EIS records of 1,440 needles assessed the interspecific variation of the P.d,P.t,P.y and the artificial hybrids.We found that(1)EIS at different frequencies diverged significantly among germplasms;P.y was the highest,P.t was the lowest,and their artificial hybrids were within the range of P.t and P.y;(2)maternal species effect of EIS magnitudes in the hybrids and P.d was stronger than the paternal species characteristics;(3)EIS of the artificial hybrid confirmed the mid-parent and partial maternal species characteristics;(4)unified exponential model of EIS for the interspecific and hybrids can be constructed as|Z|=Af^(-B);(5)cluster analysis for species and hybrid combinations in total corroborated with the previous hybrid model of Pinus densata.Our non-destructive EIS method complemented the previous finding that Pinus densata was originated from P.t and P.y.We conclude that the impedance would be a viable indicator to investigate the interspecific genetic variations of conifers.

高山松miR482a的鉴定及其表达分析

以裸子植物高山松(Pinus densata)为试验材料,利用实验室前期构建的高山松miRNA数据库,通过生物信息学方法筛选了与生长发育相关的miR482a,并通过RLM-5′RACE的方法验证了NBS-LRR抗性蛋白(Unigenes45569)是高山松miR482a的靶基因。通过PCR方法克隆得到高山松miR482a前体序列是130 bp,并可形成稳定的茎环发夹结构,但其成熟序列的碱基保守性较差。系统进化显示pdemiR482a与裸子植物欧洲云杉的进化关系较近。经qRT-PCR分析表明,pde-miR482a在根中表达量最高,其次是在茎中。而靶基因Unigenes45569在根和茎中的表达水平相对较低,暗示pde-miR482a可以通过调控靶基因NBS-LRR抗性蛋白(Unigenes45569)而参与高山松的生长发育。

Influence of ammonium and nitrate supply on growth, nitrate reductase activity and N-use efficiency in a natural hybrid pine and its parents

Selection of tree species with a high capacity to assimilate N and efficiently utilize N resources would facilitate the success of initial tree seedling establishment in infertile soils.The preference for N forms was tested using three pine species(Pinus densata,Pinus tabuliformis and Pinus yunnanensis).Pinus densata is a natural diploid hybrid between P.tabuliformis and P.yunnanensis.Methods Seedlings of three pine species were supplied with nitrate-N,ammonium-N(at two different pH regimes)or combined ammonium and nitrate as a nitrogen source in perlite culture in a controlled environment.Important Findings Seedlings of P.densata had higher total biomass and net photosynthesis when supplied with nitrate-N and ammonium nitrate than with ammonium-N.In parental species,total biomass and net photosynthesis for P.yunnanensis seedlings was higher in ammonium-N than in nitrate-N,whereas the other parental species P.tabuliformis had the highest total biomass among species for all treatments except ammonium with CaCO_(3).Most morphological traits in P.densata seedlings were intermediate between its two parental species.However,N-use efficiency and photosynthetic N-use efficiency of P.densata significantly exceeded both parents when supplied with nitrate-N and ammonium nitrate.The results suggested that the diploid hybrid tree species P.densata has a preference for nitrate and is not well adapted to ammonium-N as a sole nitrogen source regardless of the growth medium pH.Based on changes in environmental conditions,such as predicted future temperature increases in high altitude areas associated with climate change,P.densata is likely to be increasingly competitive and have wide adaptation in high altitude regions.