Spectral Pre-Processing and Multivariate Calibration Methods for the Prediction of Wood Density in Chinese White Poplar by Visible and Near Infrared Spectroscopy

Wood density is a key indicator for tree functionality and end utilization. Appropriate chemometric methods play an important role in the successful prediction of wood density by visible and near infrared (Vis-NIR) spectroscopy. The objective of this study was to select appropriate pre-processing, variable selection and multivariate calibration techniques to improve the prediction accuracy of density in Chinese white poplar (Populus tomentosa carriere) wood. The Vis-NIR spectra were de-noised using four methods (lifting wavelet transform, LWT; wavelet transform, WT; multiplicative scatter correction, MSC; and standard normal variate, SNV), and four variable selection techniques, including successive projections algorithm (SPA), uninformative variables elimination (UVE), competitive adaptive reweighted sampling (CARS) and iteratively retains informative variables (IRIV), were compared to simplify the dimension of the high-dimensional spectral matrix. The non-linear models of generalized regression neural network (GRNN) and support vector machine (SVM) were performed using these selected variables. The results showed that the best prediction was obtained by GRNN models combined with the LWT and CARS method for Chinese white poplar wood density (Rp2 = 0.870; RMSEP = 13 Kg/m3; RPDp = 2.774).

Effect of Initial Planting Density on Growth Traits and Wood Properties of Triploid Chinese White Poplar (Populus tometosa) Plantation

Planting density primarily affects the yield and wood quality of plantations. There are multiple reports on the effects of planting density on growth traits and wood properties in young triploid Chinese white poplar (Populus tomentosa) plantations. Nevertheless, assessment of the effects of initial planting density is lacking for plantations older than ten years. Here, an 11-year-old plant density trial (2490, 1665, 1110, 832, 624, 499, and 416 trees/hm2) established with four hybrid clones (S86, B301, B331 and 1316) in northern China was used to determine the effect of initial planting density on growth traits (diameter at breast height (DBH), tree height (H), stem volume (SV) and stand wood volume (SWV)), basic wood density (BWD), and fiber properties (fiber length (FL), fiber width (FW), and the ratio of fiber length to width (FL/FW)). A total of 84 trees from four clones were sampled. In this study, the initial planting density had a highly significant effect on growth traits (p < 0.001) and had a moderate effect on FL. Overall, the reduction in initial planting density led to the increase in DBH, H, SV, and FL/FW. Triploid hybrid clones planted at 416 trees/hm2 had the largest DBH, H, SV, FL/FW and the smallest SWV and FW. Clonal effects were also significant (p < 0.05) for all studied traits except for FL. Clone S86 had a higher growth rate and the largest BWD and FW. Clones–initial planting densities interaction was insignificant for all growth traits and wood properties. A weak and positive estimated correlation between BWD and growth traits (H, SV, SWV) within each planting density was seen. Our results demonstrate that an appropriate reduction in initial density in triploid Chinese white poplar plantations with long rotation is a suitable strategy to promote tree growth and retain excellent wood processing characteristics.

EFFECT OF GRAPHENE OXIDE ON REGENERATED PLANTS OF WHITE POPLAR × ASPEN HYBRID

In this work, we have studied the effect of graphene oxide on the regenerants of the white poplar × aspen hybrid when they were transferred to non-sterile greenhouse conditions during clonal micropropagation. It was shown that a suspension of the nanomaterial at a concentration of 1.5 μg / L stimulated the growth of plant height in the hybrid (white poplar × aspen), but also increased the number of wilted leaves. An increase in the concentration of nanomaterial to 3 μg / L caused a negative effect on seedlings. The number of surviving shoots decreased by 17% relative to the control, plant height decreased by 25%. A decrease in the number of leaves and adapted microclones was also observed: 15% of plants adapted against 55% in the control group. The general condition of the seedlings of this group was assessed only by 3 points out of 5. Analysis of binaccumulation of graphene oxide in plant organs has not showed pronounced foci of nanomaterial accumulation. Thus, graphene oxide had a multidirectional effect on the development of seedlings of the hybrid (white poplar × aspen). The results of the study can be used in assessing the environmental safety of graphene-like materials in relation to plants, as well as for improving the biotechnology of clonal micropropagation of forest plantations

Populus alba (silver-leaf poplar).

P. alba, the white or silver-leaved poplar, is widely grown as an ornamental for its silvery foliage. It is a fast-growing tree utilized in afforestation and reforestation due to its resistance to drought, salt and wood borers. It is not as important commercially as poplar species of sect. Aigeiros, but its adaptation to warm conditions allows it to be cultivated in Mediterranean regions and in Central Asia. P. alba is widely used in interspecific breeding programmes to introduce valuable traits, such as high rooting ability of stem cuttings, into economically more valuable species, particularly P. tremula of sect. Populus. P. alba hybridizes readily with this closely related species, the resulting hybrid, known as grey poplar (Populus x canescens), being intermediate morphologically between its parents, with a thin, grey, downy coating on the leaves, which are also much less deeply lobed than in white poplar. It exhibits marked hybrid vigour, with trees displaying vigorous growth and reaching 40 m in height and over 1.5 m in trunk diameter, much larger than either of its parents.P. alba is suitable for propagation by tissue culture and is used as a subject for Agrobacterium-mediated genetic transformation.

White poplar (Populus alba L.) stands in Ukraine: the current state, growth specificities and prospects of using for forest plantations

The aim of the study was to assess the current state and evaluate the productivity of white poplar stands by natural zones within Ukraine and to define the prospects for their use for plantation forest cultivation. The objects of the study were white poplar stands in Ukrainian forests grown on the area of more than 7,600 hectares in various natural zones, namely Polissya (forest zone in Ukraine), Forest-Steppe, and Steppe. The study was carried out based on the analysis of forest inventory data (Ukrainian forest fund database) containing given stand characteristics such as origin, age, diameter, height, type of forest site conditions, etc. The characteristics were estimated by grouping the plots by age. The growth specificities (dynamics of the main mensuration characteristics) and the productive capacity of the white poplar stands were analyzed based on the developed tables. It was found that white poplar stands are mainly concentrated in Steppe and Forest-Steppe in Ukraine. The stands are of coppice or artificial origin; they grow in moist fairly fertile, fresh fairly fertile and moist fertile sites. The age distribution of the white poplar stands is severely imbalanced due to a significant predominance of stands aged over 40 years in all natural zones within Ukraine. More productive are the white poplar stands growing within Polissya and Forest-Steppe. The developed growth and productivity tables should be used when planning and prioritizing the relevant forestry interventions in white poplar stands.

Establishment of white poplar clonal plantations by stools

The results of white poplar clonal plantation establishment by stools are presented. The trials were established at three sites, characterized by favorable water regime for growth and development of poplars. Also, the effect of different factors on survival rate, diameter at breast height and plants' height was analyzed. Results suggest that similar high survival rate (90-100%) was achieved by planting of stools on depth of 2.5 m (deep planting), as it was achieved by planting of rooted cuttings at the depth of 0.8 m, which is a comon practise in the establishment of white poplar plantations. The survival rate of planted stools did not decrease signifficantly between the end of the first and second growing season. Selected clones achieved survival rate of Villafranca clone with both methods of planting. Two-year old rootless shoots (2/0 type of plantings) achieved higher survival rate than the one-year old ones (1/0 type) and two-year old rooted cuttings (2/2 type). Survival rate of one-year old rootless shoots (1/0 type) planted at the depth of 0.8 m was not significantly lower than of those planted at the depth of 2.5 m, but it was notably lower than survival rate of rooted cuttings (1/1 type). Establishment of white poplar clones by stools could significantly improve white poplar wood production, considering the benefits of plants production in stool beds. The potential for improvement of the establishment of white poplar plantations on sandy soils with relatively deep level of underground water, and the potential for successful planting of difficult-to-root white poplar genotypes, should be the subject of further studies.

Change in hydrolytic enzyme efficiency over time

Change in hydrolytic enzyme efficiency over time. The purpose of this study was to determine the action of hydrolytic enzymes (by Dyadic Cellulase CP CONC, and the Dyadic Xylanase 2 XP CONC) over time. Chromatographic analysis of holocellulose samples subjected to enzymatic hydrolysis was performed. The following hydrolysis parameters were used: time 48h, temperature 45 ⁰C, acetate buffer pH 5.4, commercial enzymes Dyadic. Holocellulose extracted by the sodium chlorite method from white poplar wood (Populus alba L.) was used. The final yield of enzymatic hydrolysis was determined. The results of hydrolysis performed at intervals were compared. The results obtained show that the hydrolysis yield of holocellulose after five months decreased by 40 p.p. for glucose yield and by 25 p.p. for xylose yield. The yield for glucose after two and a half years decreases by 68 p.p. and 62 p.p. for xylose compared to the initial yield.

Evaluation of physiological indicators of plants of the genus Populus in arid conditions of Zhezkazgan

The creation of modern green spaces should be based on the selection of a sustainable assortment. Resistance is evaluated on the basis of a number of physiological indicators. Preliminary testing is of particular value for industrial regions with difficult climatic conditions. The purpose of this study was to study the resistance of 4 species of poplars to drought, winter conditions, the effects of diseases and pests, and atmospheric pollution. Resistance assessment was carried out for the species Populus alba, Populus balsamifera, Populus canadensis, Populus nigra, covering the period from 2015 to 2019. The results of visual observations showed that all species of poplars have high winter resistance — 4–5 points. Maximum winter resistance is noted for white poplar, minimum — for canadian poplar. The gas stability of poplars is estimated at 3–5 points. The greatest stability is noted in balsamic poplar, the minimum — in canadian poplar. Drought resistance among poplar species is estimated at 3–4 points. White and canadian poplar showed the least resistance to drought, while canadian poplar showed the maximum. Estimated scores of resistance to diseases and pests were 4–5 points, the highest indicators were noted for balsamic poplar, the minimum — for black poplar. On the basis of the identified indicators, the directions of poplar use in green construction are proposed.