To investigate the effects of different stumping heights on leaf and root functional traits of T. amurensis and provide reference for its plantation cultivation.

Gas exchange parameters, chlorophyll content, anatomical, the content of soluble sugar and starch of leaves and fine roots were determined and analyzed under four treatments: stubble 15 cm (T1), stubble 10 cm (T2), stubble 5 cm (T3), and unleveled stubble (CK).

The number of sprout strips was the highest and the length increased significantly under T3 treatment. Stumping significantly increased the net photosynthetic rate, transpiration rate, stomatal conductance and water utilization of leaves, and the T3 treatment was the most effective, which increased 84.3%, 74.9%, 45.1% and 42.3%, respectively, compared with CK. The daily trend of the net photosynthetic rate and transpiration rate, all treatments had obvious bimodal curves (except for T3), which had a single peak curve, and both peaks appeared at 9: 00 a.m. and 13: 00 p.m. The daily trend of water use efficiency was all bimodal, but the time of the peaks appeared was different. The content of chlorophyll of all treatments increased after stubble. Among them, the chlorophyll a and b of T3 increased the most, which increased by 64.3% and 35.1% compared with CK, respectively. The thickness of palisade tissue and spongy tissue in the leaves increased significantly after stumping. However, the palisade tissue thickness decreased with the decrease of stumping height, among which the increase of T1 treatment was the most significant, increased by 40.1% compared with CK; the sponge tissue thickness increased with the decrease of stumping height, and the increase of T3 treatment was the most significant, increased by 24.4% compared with CK. The upper and lower epidermal thicknesses of the leaves after stumping was significantly lower than that of CK, and increased with decreasing stumping height. T3 treatment decreased by 27.1% and 45.4%, respectively, compared with CK. Compared with CK, the vascular bundle diameter, thickness of cortex, and root diameter of fine roots decreased after stumping. The content of sugar and starch in the leaves in all treatments was lower than that of CK, while in the roots were higher than that of CK.

Stubble had a certain effect on the growth of leaves and fine roots of T. amurensis. When the stumping height is 5 cm, the compensatory growth is the most significant, which is a relatively suitable stumping height.

A preliminary evaluation of the cold resistance of four tree species was conducted by studying the dynamic changes in cold resistance physiological indicators of branches of Fraxinus mandshurica, Phellodendron amurense, Juglans mandshurica and Tilia amurensis during the natural overwintering process with the aim of selecting the tree species with the strongest cold resistance among them and further providing some reference for cross-regional introduction of broad-leaved tree species in the southern part of Daxing’an mountains.

Four samples were collected during natural low temperature stress to determine theirs REC, enzyme activity of POD, SOD and CAT, content of MDA, SS, SP, Pro and water by using 2-year-old branches of 4 tree species from September 2023 to March 2024, and the cold tolerance of them was preliminarily evaluated by combining correlation analysis and fuzzy membership function methods.

1) The REC of 4 tree species showed a trend of first increasing and then decreasing with temperature changes; The MDA content of F. mandshurica seedlings showed a trend of first increasing and then decreasing, while the other 3 tree species showed a trend of “up-down-up”; 2) Except for J. mandshurica, the SP content of other tree species showed a single peak trend of first increasing and then decreasing; Except for P. amurense seedlings, which showed a trend of first decreasing and then increasing SS content, all other tree species showed a gradually increasing trend; In 4 sampling months, the Pro content of P. amurense was the highest among the tree species, followed by J. mandshurica, and the Pro content of F. mandshurica and T. amurensis was lower than that of P. amurense and J. mandshurica; 3) The protective enzyme activity of 4 tree species did not show a consistent pattern. The SOD enzyme activity of J. mandshurica changed the most, while the POD enzyme activity of P. amurense changed the most. The CAT enzyme activity of P. amurense and J. mandshurica was higher than that of F. mandshurica and T. amurensis in all 4 sampling months; 4) Except for the trend of “up-down-up” in the moisture content of the branches of T. amurensis, the other 3 tree species showed the opposite trend to that of T. amurensis; 5) The membership function values of F. mandshurica, P. amurense, J. mandshurica, T. amurensis were 0.489, 0.488, 0.484, and 0.480, respectively.

The relative physiological indexes of cold resistance of 2-year-old branches of different tree species are significantly different in the process of natural low temperature stress. Combined with the comprehensive evaluation value of membership function, it can be preliminarily determined that P. amurense has the strongest cold resistance and shows adaptability to low temperature, and T. amurensis has the weakest cold resistance.

The multiple distribution of spatial structure parameters and the models of response to them of Hegyi index of L. gmelinii natural forest, unmanaged plantation after 30% intensity thinning, and plantation managed according to target tree management after thinning were studied in Greater Khingan mountains, to provide a scientific basis for an in-depth understanding of the heterogeneity of the spatial structure of L. gmelinii plantation and for the future management.

Taking the above three kinds of L. gmelinii forest as the research objects, the multiple distribution of spatial structure parameters were analysised throught mingling degree, neighborhood comparison, uniform angle index, opening degree based on the relationship among the nearest adjacent trees, based on this, the distribution of Hegyi index of stands is analyzed.

1) From zero-element distribution, the three stands were in the mean state of serious lack of growing space, and the crop stand was mixed at zero degree with uniform distribution. The CK stand was weakly mixed with random distribution. The natural stand was moderately mixed with non-uniform distribution; 2) From the one-dimensional distribution, there were more trees in low mingling degree in the two kinds plantations, but there was little difference in the probability of different mingling degree in the natural stand. The natural stand had the most individuals randomly distributed, and the crop stand had the lowest. Three kinds of stands were concentrated in the growing space shortage or serious shortage; 3) From the quaternion distribution, tree frequencies in the three stands all presented pyramidal distribution centered on random distribution, zero degree mixing and serious lack of growth space, with the most concentrated in crop stand and the most dispersed in crop stand. The crop stand was the most concentrated and the natural stand was the most dispersed. There was no significant difference in the frequency distribution of different neighborhood comparison among the spatial structure parameter combinations; 4) The peak value of the individuals with higher Hegyi index in the three stands was random distribution, zero mixed and seriously insufficient growth space, and the ratio of neighborhood comparison. The competition intensity of natural stand was more intensely than plantation forests stand and differ significantly, with crop stand slightly less than control stand.

The study provides a scientific basis for the differences of spatial structure and tree competition between natural forests and plantations of the L. gmelinii and the effects of target tree management. The spatial structure of natural forests is richer than that of plantations, and the competition intensity of natural forests is higher than that of plantations. The spatial structure is more unitary under target tree management, weaken the competition intensity among reserved trees and promote the growth of individual tree. Combine with the purpose of forest management, this study provides a feasible method for determining felled trees, and show that the Hegyi index distribution based on multivariate distribution of spatial structure contain more information than the simple Hegyi index.

Reasonable fertilization can improve soil fertility, increase trees resistance to pests and diseases, and improve wood yield and quality. To explore the effects of proportionate fertilization on the growth, photosynthesis, leaf nutrient content and leaf anatomical traits of T. amurensis, and provide theoretical reference for the efficient fertilization technology of T. amurensis.

Using 7-year-old Tilia amurensis as experimental materials, used N, P, K 3 factors 3-level orthogonal test L₉(3⁴), set up different fertilization ratios treatments, including T1 (N₁P₁K₁), T2 (N₁P₂K₂), T3 (N₁P₃K₃), T4 (N₂P₁K₂), T5 (N₂P₂K₃), T6 (N₂P₃K₁), T7 (N₃P₁K₃), T8 (N₃P₂K₁), T9 (N₃P₃K₂), a total of nine treatments and the CK, to determine leaf nutrient content, gas exchange parameters, anatomical traits, and tree height and diameter growth.

1) Rational fertilization could significantly (P < 0.05) increase the height and diameter growth of T. amurensis, both of which were highest in the T5 treatment, which increased 155.86% and 115.92%, respectively, compared with CK. 2) there were no significant changes in the total N and total P contents of the leaves of T. amurensis treated with different ratios of fertilization, and the leaf N and P contents were the highest in T1 and T2, respectively, but the leaf N∶K values were significantly elevated (P < 0.05), the leaf total K and K∶P values were significantly reduced, and the K content was the lowest in T9, which was lower than that of the CK by 32.5%. 3) The net photosynthesis rate, transpiration rate, stomatal conductance and inter-cellular CO₂ concentration of leaves of Tilia amurensis treated with different fertilizer ratios were significantly different from those of CK (P < 0.05). Among them, the net photosynthetic rate was greatest at T4, transpiration rate and stomatal conductance reached the maximum at T5, and the inter-cellular CO₂ concentration was the best at T3. 4) proportionate fertilization had a significant effect (P < 0.05) on the structure and tissue thickness of the leaves of T. amurensis, and there was no significant effect on leaf tissue compactness. Among them, the ratio of palisade tissue to spongy tissue was higher than that of CK, and treatment T5 showed the best performance in palisade tissue and spongy tissue ratio, which was 65.96% higher compared with CK. The differences between leaf tissue porosity and control were all non-significant, ranging from 0.29 to 0.42; leaf tissue compactness was significantly higher than that of control in all treatments (P < 0.05), but there was no significant difference between treatments, ranging from 0.31 to 0.49.

Reasonable N, P and K ratio fertilization could improve the photosynthetic capacity and nutrient accumulation capacity of T. amurensis, and promote the growth of T. amurensis. Taken together, the treatment of T4 was the most effective in this experiment, i.e., the fertilization rates of CO(NH₂)₂, Ca(H₂PO₄)₂ and KCl were 28.3, 42.9 and 10.8 g per plant, respectively.

Betula costata and Betula pendula have substantial economic and ecological benefits as timber trees and they are excellent trees for soil rehabilitation and urban greening. The primary method of accelerating the rapid propagation of Betula costata and Betula pendula is to take cuttings from their elite trees. In recent years, putrescine is found to be closely related to cutting rhizogenesis as a nitrogenous base with high biological activities. Identifying the optimal concentration of putrescine during rhizogenesis and exploring its impact on root characteristics are crucial for popularizing these two tree species.

The two-year-old shoots of Betula costata and Betula pendula from the same families were used as the experimental materials. The samples were treated with putrescine solutions with different concentration gradients of T1, T2, and T3 (500, 1 000, 1 500 mg·L^-1), and the control groups (CK1 and CK2) were set up. In this study, we determined the rooting rate, root number, root length, root weight and non-structured carbohydrates in the cuttings. The effects of putrescine on rhizogenesis and non-structured carbohydrate contents of the two tree species were revealed by ANOVA, correlation analysis, and membership function analysis.

The optimal concentration of putrescine for Betula costata was 500 mg·L^-1, the rooting rate was 26.7%, the number of roots was 5.3, and the average root length was 9.4 cm. While the optimal concentration of putrescine for Betula pendula was 1 000 mg·L^-1, the rooting rate was 42.7%, the number of roots was 6.7, and the average root length was 6.5 cm. However, for the content of non-structured carbohydrates in roots and stems, the optimal concentration of putrescine for Betula costata and Betula pendula were 1 000 and 500 mg·L^-1, respectively.

For both Betula costata and Betula pendula, putrescine concentration is a key factor affecting their rhizogenesis. Compared with ABT and IBA treatments, putrescine treatments not only significantly promote the rooting rate, root length, and root weight of cuttings, but also increase the content of non-structured carbohydrates in the root and stem of cuttings. However, based on the membership function analysis, although the putrescine +ABT (or IBA) treatment has the best overall index promotion effect, the advantage was not obvious compared with the treatment with ABT or IBA.

The objective of this study was to explore the effects of small forest gap on the growth and survival of artificially regenerated Tilia amurensis seedlings by characterization of parameters such as leaf morphology, gas exchange parameters[net photosynthetic rate (P_n), transpiration rate (T_r), intercellular CO₂ concentration (C_i), stomatal conductance (G_s)], chlorophyll content(Chlt), carbon and nitrogen contents. These results provide a theoretical basis for the artificial regeneration of Tilia amurensis in small forest gaps and closed canopy.

The two-year-old artificially regenerated Tilia amurensis seedlings in Xiaojiu forest farm, Shangzhi City, Heilongjiang Province were selected as the research object. The plant height, ground diameter, survival rate and leaf morphology, gas exchange parameters, chlorophyll, carbon and nitrogen contents of Tilia amurensis seedlings in small forest gaps (G1, Forest gap area was greater than 30 m²; G2, The gap area was greater than 20 m² and less than 30 m²; G3, The gap area was less than 20 m²) and closed canopy (CK) were measured.

The plant height and survival rate of Tilia amurensis seedlings were higher in G1 and G2 than those in G3 and CK, and the height and survival rate of Tilia amurensis were positively correlated with the light intensity. The leaf area, specific leaf area and nitrogen content of Tilia amurensis were significantly increased with the decrease of gap area (P < 0.05). The specific leaf area and nitrogen content of Tilia amurensis were negatively correlated with light intensity. The P_n value was significantly higher in G1 and G2 than that in G3 and CK (P < 0.05), and P_n was positively correlated with light intensity. The contents of T_r, G_s and Chla/b were significantly decreased with the decrease of gap area (P < 0.05), while C_i and Chlt were significantly increased (P < 0.05). T_r and G_s were positively correlated with light intensity, while C_i and Chlt were negatively correlated with light intensity.

In small forest gaps, Tilia amurensis seedlings had strong photosynthesis in gaps greater than 20 m² and could maintain strong competitiveness in this habitat. However, Tilia amurensis seedlings could not capture enough light energy in gaps less than 20 m² in the closed canopy, which would inhibit its growth.

As an ideal timber and landscaping tree species, Betula costata has great ecological and economic value. At present, the resources of B. costata are scarce, so artificial cultivation should be strengthened to meet the resource reserve. B. costata is not suitable for sowing propagation due to seed characteristics of short-life, dormancy, low maturity and difficult collection, therefore, cutting becomes one of the suitable means. The purpose of the study was to explore the rooting effect of tender cutting of B. costata under different treatments and provide theoretical and technical support for its rapid propagation and application.

According to L18(3⁷) orthogonal experimental design, we measured the rooting indicators, including rooting rate, the longest root length, number of adventitious roots and root effect indexes under the different factors (substrate type, sampling site, hormone type, hormone concentration and treatment time) by using the 2-3-year-old shoots as the cutting materials.

The cutting substrate had a significant effect on rooting rate, longest root length, adventitious root number and root effect indexes. The rooting rate, number of adventitious roots, longest root length and root effect index were significantly affected by the sampling site. The kinds of hormones showed significant effects on rooting rate and average root length, but had no significant effects on other indexes. Hormone concentration and treatment time had no significant effect on each index.

We found that treatment 16 [Substrate 3 (vermiculite + fine river sand + peat soil) + the upper cuttings + 500 mg·L^-1 ABT + 30 min soak] was the best, with a rooting rate of 38.89%.

Tilia amurensis is an endemic tree species in northern China, with crucial ecological and economic values. It is difficult to regenerate T. amurensis under all-light conditions. Vegetation control can promote the growth of target species by changing light conditions and soil quality. As a consequence, identifying the optimal intensity of vegetation control and its impact on leaf characteristics and seedling's growth is crucial for popularizing T. amurensis.

T. amurensis monocultures (five-year-old) with an inter-row and intra-row spaces of 1.5 m × 1.5 m were used as experimental materials. Vegetation control treatments with different intensities T₃₀, T₅₀ and T₇₅ (clearing vegetation in the radius of 30, 50 and 75 cm around T. amurensis seedlings) and control groups (CK) were set as experimental designs. We investigated leaf morphology, gas exchange parameters, the content of chlorophyll and nutrients, and seedling growth. The effects of herbaceous and woody vegetation control on leaf characteristics and seedling growth of T. amurensis were revealed by ANOVA.

The light intensity was linearly positively correlated with the vegetation control intensity (P < 0.05), and reached the maximum under the T₇₅ treatment (84.43±7.30×10³ lx). The leaf morphological indices (leaf length, leaf width, single leaf area and specific leaf area) of T. amurensis decreased with the intensity of vegetation control, and reach their maximum and minimum values under CK and T₇₅ treatment, respectively. The leaf net photosynthetic rate was the highest under T₃₀ treatment (12.12±1.28 μmol·m^-2·s^-1), and the intercellular CO₂ concentration was largest under CK treatment (263.14±8.77 μmol·mol^-1), both of which decreased with the intensity of vegetation control. The leaf stomatal conductance and transpiration rate increased with the intensity of vegetation control, and reached their maximum values under T₇₅ treatment (0.17±0.02 mol·m^-2·s^-1 and 7.02±1.21 mmol·m^-2·s^-1, respectively). Vegetation control had significant effects on the leaf's total carbon, total nitrogen and total phosphorus contents (P < 0.05), but had no significant effect on the stoichiometric ratio of the leaf's carbon, nitrogen and phosphorus (P > 0.05). In addition, vegetation control increased the contents of soluble sugar and starch in leaves but decreased the contents of chlorophyll a and chlorophyll b in leaves, promoting the seedling's growth of ground diameter, but inhibiting the seedling's growth of tree height.

With the change in vegetation control intensity, the morphology, stoichiometry and physiological characteristics of T. amurensis leaves take adaptive changes correspondingly. T. amurensis seedlings can increase the leaf area, specific leaf area, chlorophyll content and the absorption of nutrients to improve the ability to capture light energy, enhance their photosynthesis and promote the seedling's growth under low light conditions. The leaf net photosynthetic rate and seedling ground diameter growth reach their maximum under the T₃₀ treatment, indicating that T. amurensis seedlings are the most competitive under the T₃₀ treatment. Consequently, vegetation control within a radius of 30 cm centered on seedlings is the best way to promote the artificial regeneration of T. amurensis.

Studying the dynamic characteristics of litter decomposition and nutrient release of different species of plantations of the Larix genus, revealing the pattern of litter decomposition and nutrient release, which is of great significance to the in-depth investigation of the process of material cycling in forest ecosystems, and provides a scientific basis for the management of larch plantation forests.

Four species of 40-year-old Larix plantations (Larix gmelinii, L. principis-rupprechtii, L. kaempferi, and L. olgensis) in the homogeneous habitat were used for the decomposition experiment using net-bagging method of litter. Based on different stages of decomposition, the residual mass of litter was weighed, and the contents of major elements (C, N and P) as well as difficult-to-degrade components (lignin, cellulose and condensed tannins) in the litter were measured. The overall residual rates, mass loss rates and nutrient release rates of litter at each stage of decomposition were calculated, and the Olson index decomposition model was established, which was used to analyze the differences among tree species. Pearson correlation analysis and principal component analysis were conducted to clarify the relationship of litter mass loss rates with initial substrate qualities and nutrient release rates, respectively.

In decomposition to 90 days, the mass loss rate of litter in L. kaempferi plantation was significantly higher than that in L. principis-rupprechtii plantation, with the greatest contribution to mass loss (P < 0.05), and its lignin and cellulose release rates were significantly higher than those in L. olgensis plantation (P < 0.05). The mass loss rate of litter was significantly negatively correlated with the initial C∶N ratio. In decomposition of 90-360 days, the L. principis-rupprechtii plantation had the highest mass loss rate of litter, with the greatest contribution to mass loss, and its lignin release rate was significantly higher than that of L. olgensis plantation (P < 0.05). The mass loss rate of litter was highly significantly negatively correlated with initial lignin content and lignin∶N ratio, and strongly positively correlated with N and lignin release rates. In decomposition of 360-450 days, litter P and lignin release rates were the highest and condensed tannin release rate was the lowest in L. olgensis plantation, and litter cellulose and condensed tannin release rates were significantly higher in L. gmelinii plantation than in the other three Larix plantations (P < 0.05). The mass loss rate of litter was strongly positively correlated with C and cellulose release rates, and strongly negatively correlated with P release rates. In the litter of 4 species of Larix plantations, the C, N elements, lignin and condensed tannins showed a direct release pattern; the P element showed a leaching-enrichment-release pattern; and the cellulose showed a leaching-enrichment pattern.

The initial N, lignin content and C∶N ratio and hardly degradable components release rates of litter were important factors affecting its decomposition. Litter decomposition was the fastest in L. gmelinii plantation, which accelerated nutrient cycling, while litter decomposition was the slowest in L. principis-rupprechtii plantation, which slowed nutrient cycling. This is of great significance to the management of different species of plantations of the Larix genus.