Fang ShengZuo

Variation of microfibril angle and its correlation to wood properties in poplars

The microfibril angle of seven poplar clones was determined by using X-ray diffraction technique. Microfibril angle, wood basic density, fiber length, fiber width and cellulose content were assessed for every growth ring at breast height for all sample trees. Significant variation in microfibril angle was observed among growth rings. Mean microfibril angle (MFA) at breast height varied from 7.8° to 28° between growth rings with cambial age and showed a consistent pith-to-bark trend of decline angles. Analysis of variance also indicated that there were significant differences in wood basic density, fiber length, fiber width and cellulose content between the growth rings, which had an increasing tendency from pith to bark. Correlations between MFA and examined wood properties were predominantly large and significant negative (α=0.01), and the coefficients were −0.660 for cellulose content, −0.586 for fiber length, −0.516 for fiber width and −0.450 for wood basic density, respectively. Regression analysis with linear and curve estimation indicated that a quadratic function showed the largestR2 and the least standard error for describing the relationships between microfibril angle and measured wood properties, and the correlation coefficients were over −0.45 (n=125). The results from this study suggested that microfibril angle would be a good characteristic for improvement in the future breeding program of poplars.

Interclonal and within-tree variation in wood properties of poplar clones

The wood basic density, cellulose content and fiber form were investigated for all sample trees at breast height (1.3 m) in seven poplar clones, and at 0 (butt), 5.6, 9.6, 13.6, 17.6, 19.6 and 21.6 m for clone Nanlin-95 and Nanlin-895, respectively, for providing information on variation patterns of wood density, fiber characteristics and holocellulose content within trees and among clones. The results showed that significant variations about wood density, cellulose content, fiber diameter and the ratio of fiber length to diameter existed among poplar clones examined. Variance analysis indicated that there were significant differences in wood basic density, fiber length, fiber diameter and cellulose content among the growth rings, which had an increasing tendency along the direction from pith to bark. The significant differences also existed in wood basic density, fiber length and fiber diameter at different tree height. The mean wood basic density had a general increase trend with increasing height of trees and the lowest was found at the base, while fiber length and fiber diameter had a general decline pattern with increasing height of trees and the biggest value was observed at the height of 5.6 m. Regression analysis indicated that the relationship between examined wood properties and growth ring number (cambial age), and the relationship between examined wood properties and tree height can be described by polynomial functions.

Impact of Spacing and Rotation Length on Nutrient Budgets of Poplar Plantations for Pulpwood

The above-ground biomass and nutrient accumulation by poplar plantations were evaluated for pulpwood production in China. Experimental treatments applied in a split-plot design included four planting densities (1111, 833, 625 and 500 stems·hm−2), three rotation lengths (4a, 5a and 6a) and three poplar clones (I-69, NL-80351 and I-72). The highest biomass was achieved in the highest stocked stand (1111 stem·hm−2) at 6 of rotation age for both clone I-69 and clone I-72, which is about two times that in the stands of 500 stems·hm−2 at 4 of rotation age. However, the highest occurred in the stand of 833 stems·hm−2 at 6-year rotation for NL-80351. Ranking of the plantation biomass production by component was stem>branches>foliage>stem-bark and the production of the support components of the plantation was 10-fold that of the productive component, i.e., foliage. The pattern of accumulation of nutrients by the plantations was similar to the biomass. Nutrient accumulation in the plantations was in the order of Ca>N>K>Mg>P, but some differences existed in annual nutrient accumulation rates for four planting densities and three poplar clones. The mean annual accumulation of N and P in the plantations was 13.2 and 2.8 kg·hm−2 in stem, 12.1 and 1.9 kg·hm−2 in branch, and 98.5 and 9.5 kg·hm−2 in foliage. The mean Ca, K and Mg accumulations were 28.2, 18.5 and 2.9 kg·hm−2·a−1, 26.9, 11.0 and 2.3 kg·hm−2·a−1 in branch, and 116.5, 81.3 and 16.1 kg·hm−2·a−1 in foliage, respectively. Biomass utilization standards markedly affected the export of nutrients from the site. Whole tree utilization yields the most biomass and removes the most nutrients. Removal of stem with ≥10-cm diameter exports about half of the biomass, but N and nutrients removals are only 23% and 28% of the total, respectively. Removal of the entire stem provides about two-thirds of the total biomass and removes 31.1% total N and 37.5% total nutrients respectively. Including the branches in the removal increases biomass yield to 92% of the total, and nutrient removal is about 68% of the total.

Effects of Ca2+ concentrations on accumulations of mineral elements in the components ofPteroceltis tatarinowii

The bark ofPteroceltis tatarinowii is a raw material for manufacturing Xuan Paper. The effects of Ca2+ concentrations on the accumulation of mineral elements in the bark, leaf and root ofPteroceltis tatarinowii were studied under controlled conditions. The types of Hoagland nutrient solution with three Ca2+ concentrations levels (200, 400 and 600 μg·g−1) and a control (without Ca2+ were designed to culturePteroceltis tatarinowii. After 6 months, contents of seven mineral elements including Ca, K, Mg, Mn, Zn, Cu and Na in the root, leaf and bark were analyzed. The results indicated that Ca accumulations content in the root, leaf and bark had positively relation with Ca2+ concentrations (200, 400, 600 μg·g−1), and the order of the Ca content in the three components was root>leaf>bark. Ca content in the root treated with 600 μg·g−1 Ca2+ concentrations was 5.5 times as high as that of the control, and about 1.4 times as high as that of the root treated in 200 and 400 μg/g Ca2+ concentrations respectively. On the contrary, K and Mg contents in the root, leaf and bark were negatively related to Ca2+ concentrations, especially in the bark, and their accumulation trend followed the order of leaf>root>bark. K content in the bark treated with 600 μg·g−1 Ca2+ concentrations was 39.3% of that of the control, and was 79.0% and 91.8% of that of the bark treated with 200μg·g−1 and 400μg·g−1 Ca2+ concentrations respectively; Mg content in the bark treated with 600μg·g−1 Ca2+ concentrations was 23.4% of that of the control, and was 27.1% and 35.4% of that of the bark treated with 200 and 400 μg·g−1 Ca2+ concentrations respectively. Compared with the control, the general tendency of Mn, Zn and Cu content decreased with increasing of Ca2+ concentrations and their contents were in the order: root>leaf>bark. Based on the results of this study, the experiment has been useful for providing academic bases in improving the bark quality ofPteroceltis tatarinowii on non-limestone soil.

Changes in the biochemical composition and enzyme activity during dormancy release of Cyclocarya paliurus seeds

Cyclocarya paliurus is only propagated from seeds which have pronounced dormancy. Overcoming seed dormancy is an important component of efficient and cost-effective seedling production of Cyclocarya paliurus. Changes in biochemical composition and enzyme activity were investigated during dormancy release. The activities of all the studied enzymes in the stratified seeds increased significantly, compared to those in the control samples. Of the enzymes examined, the activities of protease increased the most (413.8%), followed by peroxidase (278.7%), lipase (161.0%), glucose-6-phosphate dehydrognase (149.1%) and amylase (60.6%) after 8 months of stratification. Crude fat and protein constituted the bulk of the storage reserves in mature seeds of C. paliurus. Compared with the seeds before stratification, about 45% of the starch, 46% of the protein and 11% of the crude fat were depleted during dormancy release of C. paliurus seeds, while the soluble sugar content was enhanced by 101.5% in the germinating seeds. Correlation analysis showed, during dormancy release of C. paliurus seeds, a close positive relationship between POD and G6PDH activity as well as soluble sugar content and amylase activity, while there was a significant negative relationship between storage substances and their related enzyme activities.

Effects of Cutting Density on Growth, Yield and Quality of Poplar Clone Seedlings

In order to identify the optimum cutting density for producing the highest number of plantable seedlings of poplar clones, a split-plot randomized block design was used to establish four cutting densities in plots. Based on data on the survival, leaf area, seedling height, caliper, and biomass of 1-year-old seedlings of clones Nanlin-95, Nanlin-895, Nanlin-1388 and NL-80351, the growth characteristics and seedling quality under four cutting densities were analyzed. Results indicated that the leaf area, stem and leaf biomass, and caliper of seedlings of all four poplar clones increased with the decrease in cutting density. Leaf area index reached its highest level at the spacing of 40 cm×40 cm, while the aboveground biomass of the seedling on an area basis increased as the cutting density increased. Seedling quality at low cutting density was higher than that at closer cutting density. The quantity of first-grade seedlings (grade I) for clones Nanlin-95 and Nanlin-895 was achieved at the spacing of 40 cm×50 cm; for NL-1388 and NL-80351, it was 50 cm×50 cm. According to the seedling quality and the number of plantable seedlings produced, the suggested cutting density for these four poplar clones was 50,000 stems/hm2.