Variation in seed and seedling traits and their relations to geo-climatic factors among populations in Yunnan Pine(Pinus yunnanensis)

Differences in seed germination and seedling growth among populations of Pinus yunnanensis Franch. were quantified to provide information for use in the regeneration, reforestation, and improvement of this species. Seed germination and seedling growth traits at the nursery stage were investigated at the population level. We evaluated relationships between pairs of measured traits as well as the association between measured traits and geo- climatic variables including longitude, latitude, elevation, temperature and precipitation. Seedling growth showed significant differences although a low magnitude of variation was found in the seed germination traits among the populations. Some populations with strong and stable growth （e.g., the Baoshan population） may be selected as superior seed sources for regeneration and reforestation. Germination percentage was negatively correlated with elevation, and positively with precipitation. In addition, germination index, vigor index and seedling height were positively correlated with precipitation. Seed germination index, cotyledon number and length, and seedling diameter were significantly and positively correlated with seed weight. Strong correlations between pairs of traits will be helpful in early evaluations for the selection of certain prominent traits.

Variation in needle and cone traits in natural populations of Pinus yunnanensis

Pinus yunnanensis Franch. is a major component of coniferous forests in southwestern China. Little is known about its intraspecific variation. Morphological variations in needle and cone traits of P. yunnanensis were analyzed to quantify variability among and within natural populations. Seven traits were measured on 10 needles collected from 30 trees in each of the 18 sampled populations of P. yunna- nensis. Four cone traits were measured in 221 individual trees from nine populations. The results showed that there were significant differences （p 〈 0.01） both among popu- lations and within populations in each needle and cone trait. The proportion of phenotypic variation of nearly all needle and cone traits was over 50 % within populations, which showed trees within populations accounted for a majority of the total variation. The needle traits showed higher vari- ability within population than cone traits. Variability in theneedle traits was correlated with geo-climatic parameters （longitude, latitude, altitude, temperature, and precipitation）. Needle length and the ratio of needle length to fascicle sheath length showed clinal variation in response to latitudinal and altitudinal gradients. A hierarchical classification of all populations based on needle traits led to the formation of four major groups. The findings provide important genetic information for the evaluation of variation. Moreover, it will assist in management of genetic diversity of P. yunnanensis.

Modular growth and clonal propagation of Hippophae rhamnoides subsp, sinensis in response to irrigation intensity

A multipurpose clone plant species, Hippophae rhamniodes has the capacity for indefinite longevity, although under successive drought stress it may often decline or die across large areas. Field trials were con- ducted over 2 years to examine the effects of varied irrigation intensities on modular growth and clonal propagation in a semi-arid area. Irrigation levels included a control, as well as two, four and six times the volume of water that was typically received via local annual average precipitation. Irrigation intensity significantly influenced clonal propagation capacity （number of daughter ramets）, aboveground modular growth （height, base diameter, and crown width）, belowground modular growth included root nodule dry weight, stretching capacity of lateral roots （length of the longest lateral roots, and diameter of first-grade lateral roots）, and branching intensity of lateral roots （number of lateral roots bifurcation grade, number of first- grade lateral roots）. The modular growth and the density of daughter ramets were small under non-irrigation or low irrigation, and became larger with increased irrigation intensity. Beyond a certain threshold, however, further increases in irrigation intensity resulted in a reversion to the development. The optimal irrigation intensities for growth and propagation were 3.48-5.29 times the volume of nominal local annual average precipitation. There were effects of irrigation intensities on the positive significant correlations between aboveground and belowground modular growths, and on clonal propagation capacities. Under various water treatments, H. rhamnoides may adapt to the environment through the regulation of growth and propagation. We concluded that water shortages act to weaken the growth and propagation of H. rhamniodes plantations.