Wood density, as a key parameter for evaluating wood quality, is a focal point in both wood trading and processing. The development of efficient, non-destructive, and cross-species detection technologies for wood density is of great importance for the exploitation of forestry resources and the efficient utilization of wood.

This study selected two typical hardwood species from northeast China, specifically Manchurian walnut (Juglans mandshurica) and Manchurian ash (Fraxinus mandshurica), as research subjects to establish a near-infrared (NIR) spectral transfer model for cross-species wood density prediction. A stable predictive feature selection (SPFS) algorithm was designed to score and rank spectral bands. The elbow method was applied to determine the optimal number of bands and to select common feature bands. A stacked autoencoder (SAE) was introduced as a feature transformation mechanism. Combined with an artificial backpropagation (BP) neural network prediction model, a new cross-species spectral model transfer method was constructed.

Following the transfer of the Juglans mandshurica model based on SAE, the coefficient of determination (R²) for the Fraxinus mandshurica prediction set rose from 0.172 7 to 0.827 1, and its root mean square error of prediction (RMSEP) fell from 0.180 1 to 0.049 3 g/cm³. In the opposite transfer direction, applying SAE to the Fraxinus mandshurica model improved the R² for the Juglans mandshurica prediction set from 0.000 9 to 0.884 9, and reduced the RMSEP from 0.187 8 to 0.032 9 g/cm³. These results indicate that the SAE-based method achieves substantial improvements in both R² and RMSEP metrics when compared to traditional techniques such as piecewise direct standardization and slope/bias correction algorithms.

The findings of this study demonstrate that the SAE-based NIR transfer model is effective for cross-species applications, allowing for the rapid and efficient prediction of wood density in different tree species. This approach promotes model sharing across species and offers both a theoretical basis and technical support for improving the universality of NIR models.

Under the global context of climate change and the pursuit of carbon peaking and neutrality goals, scientifically assessing the dynamic evolution, driving mechanisms, and future evolution pathways of tourism-related carbon emissions at the provincial scale is critical for formulating differentiated emission reduction strategies.

Taking Hunan Province as a case study, this paper develops a hybrid accounting framework that integrates top-down and bottom-up approaches to systematically measure the magnitude and structure of tourism carbon emissions from 2006 to 2025. An extended STIRPAT model combined with ridge regression is employed to identify key driving factors, while the Tapio decoupling model and multi-scenario simulation are coupled to project peak emission pathways.

1) In terms of emission scale, tourism carbon emissions in Hunan reached a staged historical peak of 17.814 3 million tons in 2019, rebounding strongly to 16.889 7 million tons from 2023 to 2025, with transportation and sightseeing activities accounting for 74%-84% of total emissions; 2) Regarding driving factors, tourist volume is the primary positive driving factor (elasticity coefficient 0.648 7), while energy intensity shows a relatively marginal contribution (elasticity coefficient 0.106 6), indicating that current growth remains dominated by scale expansion, with technological mitigation effects not yet fully materialized; 3) In terms of decoupling trends, the dominant decoupling state from 2006 to 2025 is weak decoupling (9 occurrences), with strong decoupling occurring only once in 2008 due to external shocks; the abnormally high decoupling index in 2022 reflects exceptional circumstances, suggesting that low-carbon transition stability still requires consolidation; 4) Multi-scenario prediction indicate that under the stringent low-carbon scenario with enhanced policy constraints, emissions will peak at 19.849 million tons in 2030 and then decline gradually, contrasting with the persistent growth trajectories under the baseline and moderate low-carbon scenarios.

The relative rate of change between tourist volume and energy intensity is the decisive factor for achieving the peak; only by simultaneously curbing tourist growth and reducing energy intensity can a trend reversal be realized. This study establishes a systematic analytical framework encompassing aggregate accounting, driver decomposition, and scenario simulation, providing quantitative decision-making references for the formulation of low-carbon tourism development policies at the provincial level.

To investigate the morphological characteristics and germination traits of Rhododendron delavayi seeds from six provenances in Guizhou Province, analyze the variation and genetic characteristics of seeds from different provenances, and to provide technical support for the breeding of superior varieties.

The morphological traits (seed length, width, thickness, length-to-width ratio, flattening rate, seed dimension index, and thousand-seed weight) and germination traits (radicle length, germination rate, germination potential and germination index) of seeds from the six provenances were subjected to variability and heritability analysis, correlation analysis, and cluster analysis. The seed quality from different provenances was comprehensively evaluated using principal component analysis.

The results showed that the morphological characteristics of R. delavayi seeds from different provenances exhibited extremely significant differences (P<0.01). The coefficient of variation for seed morphological traits exceeded 10.00%, with the smallest variation observed in thousand-seed weight. The coefficients of variation for seed dimension index, seed thickness, and length-to-width ratio all exceeded 30.00%. The broad-sense heritability of morphological traits was greater than 0.87. The germination traits of seeds from different provenances also showed significant differences (P<0.05). Seeds from the Bailidujuan management area exhibited the longest radicle length (5.17 mm), the highest germination rate (77.50%), and the greatest germination potential (20.00%). Correlation analysis indicated that seed length and length-to-width ratio were significantly (P<0.05) or extremely significantly (P<0.01) negatively correlated with germination rate, germination potential, and germination index. Seed width was significantly (P<0.05) or extremely significantly (P<0.01) positively correlated with radicle length, germination rate, and germination index. The six provenances could be classified into three major categories: the first category included Zhongshan District, Shuicheng District, and Bailidujuan Management Area; the second category included Xixiu District and Hezhang County; and the third category was Changshun County. The comprehensive evaluation of seed quality from different provenances ranked as follows: Zhongshan District > Shuicheng District > Bailidujuan Management Area > Hezhang County > Changshun County > Xixiu District.

In conclusion, the morphological characteristics of R. delavayi seeds are primarily influenced by genetic factors but also exhibit certain variations due to geographical and environmental factors across different provenances. Seeds from Zhongshan District and Shuicheng District were relatively superior and can be further studied as material for breeding and propagation.

To explore the effects of different nitrogen, phosphorus, and potassium fertilizer levels on the photosynthetic characteristics, yield, and fruit quality of ‘Menguan 1’. and to provide reasonable fertilization recommendations for the cultivation of this variety in the eastern part of the northern Tianshan mountains in Xinjiang.

Six-year-old Xanthoceras sorbifolium ‘Mengguan 1’ trees grown in Xinjiang were used as the experimental materials. A “3414” fertilizer-response experimental design was adopted, in which nitrogen, phosphorus, and potassium were each assigned four application levels: 0 (no fertilization), 1 (50% of the conventional fertilization rate), 2 (the conventional fertilization rate), and 3 (150% of the conventional fertilization rate). The conventional fertilization rates were defined as 0.75 kg pure N plant^-1, 0.60 kg P₂O₅ plant^-1, and 0.20 kg K₂O plant^-1. On this basis, the effects of different N-P-K fertilization combinations on leaf photosynthetic characteristics, light-response parameters, fruit morphology, and seed yield were systematically evaluated. The rectangular hyperbolic model (RH), non-rectangular hyperbolic model (NRH), exponential model (EX), and modified rectangular hyperbolic model (MRH) were used to fit the P_n-PAR curve, and the photosynthetic parameters (P_n, T_r, C_i, WUE) and yield and quality were analyzed.

The MRH model provided the best fit, with the calculated AQY, LCP, R_d, P_nmax, and LSP being closest to the measured values. The application of conventional nitrogen fertilizer (N₂P₂K₂) significantly increased leaf P_n, while high potassium fertilizer (N₂P₂K₃) significantly enhanced the WUE of ‘Menguan 1’. Compared to the control (N₀P₀K₀), P_n increased by 57.01% and WUE by 93.62%. Regarding yield and fruit traits, the fertilization ratios of N₂P₂K₂ and N₂P₃K₂ increased the single-plant yield by 68.17% and 62.28%, respectively, compared to N₀P₀K₀. The former increased seed number, fruit diameter, single fruit weight, and single seed weight by 31.50%, 14.91%, 56.50% and 115.21%, respectively, while the latter increased oil content by 14.03%.

When the pure amounts of nitrogen, phosphorus, and potassium fertilizers were 413.54 kg/hm², 613.64 kg/hm², and 213.44 kg/hm², respectively, the photosynthetic characteristics, yield, and fruit quality of ‘Menguan 1’ could be effectively improved.

To explore the effects of different nitrogen application rates on the growth of transplanted seedlings of Phoebe neurantha (Hemsl.) Gamble cv. ‘Fengweinan’ Y.J. Fei, and to provide a theoretical basis for the efficient utilization of exogenous nitrogen in transplanted seedlings of this cultivar.

A pot experiment was conducted to compare the performance of one-year-old bare-root transplanted seedlings (L) and soil-root-ball transplanted seedlings (T) under five nitrogen application gradients: 0 (CK), 100 (ZN1), 200 (ZN2), 300 (ZN3), and 400 mg/plant (ZN4). The aim was to determine the optimal nitrogen application rate for transplanted ‘Fengweinan’ seedlings.

For bare-root transplanted seedlings (L), the total root length reaches its peak at ZN2, which is 81% higher than that of the control (CK). For soil-root-ball transplanted seedlings (T), multiple growth indicators are optimal at ZN3: plant height, ground diameter, total root length, and leaf length are significantly increased by 29%, 56%, 102%, and 103% compared with CK, respectively. The photosynthetic pigment content of both types of transplanted seedlings first increases and then decreases with the increase of nitrogen application rate. For bare-root transplanted seedlings, the photosynthetic pigment content is the highest at ZN2, and the basic photosynthetic parameters of the seedlings reach their maximum values, with net photosynthetic rate and transpiration rate significantly increased by 170% and 166% compared with CK, respectively. For soil-root-ball transplanted seedlings, the photosynthetic pigment content is the highest at ZN3, but the peaks of photosynthetic rate and transpiration rate appear at ZN4. Appropriate nitrogen application can increase the contents of soluble sugar, soluble starch, and organic nitrogen compounds, and enhance the activities of nitrogen metabolism enzymes. Excessive nitrogen application (under ZN4 treatment) leads to a 36% increase in root soluble protein content compared with ZN3, but decreases in soluble sugar, soluble starch contents, and nitrogen metabolism enzyme activities. Specifically, the soluble starch content in roots, total nitrogen in underground parts, and leaf nitrate reductase activity in the ZN4 treatment group are 28%, 7%, and 10% lower than those in the ZN3 treatment group, respectively.

Moderate nitrogen application promotes seedling growth by enhancing photosynthetic performance and carbon-nitrogen metabolism. The optimal nitrogen application rates for bare-root seedlings and soil-balled scedings are 200 mg per plant and 300 mg per plant, respectively.

Through the analysis of soil characteristics in main Camellia oil producing areas in Hainan Island, this paper aims to reveal the geographical distribution characteristics of nutrients in Camellia oil forest soil in Hainan Island, and comprehensively evaluates the soil characteristics and fertility in Camellia oil forest land in Hainan Island.

The study measured 15 sample plots from the main Camellia oil production areas in Hainan Island, evaluating key parameters including bulk density, total porosity, capillary porosity, non-capillary porosity, moisture content (weight/volume), maximum capillary water retention, field water retention, saturated moisture content, soil solid-liquid-gas ratio, pH, organic carbon, organic matter, total nitrogen, total phosphorus, total potassium, nitrate nitrogen, ammonium nitrogen, alkaline-hydrolyzed nitrogen, available phosphorus, fast-acting potassium, slow-release potassium, cation exchange capacity, microbial nitrogen biomass, and microbial carbon biomass. Significant differences were analyzed using Duncan's multiple comparisons, visualized through correlation heat maps, and principal component analysis (PCA) was conducted to extract principal components. Comprehensive scores were calculated for ranking purposes.

The soil samples showed significant variations in moisture content: HK-1 and CM-2 had the highest relative moisture levels (62.54%-67.15%). Among the three phases (solid, liquid, and gas), the HK series (HK-1 and HK-2) contained the lowest proportion of solid matter (39.21%-43.05%) but higher air content (26.48%-30.23%). HK-2 demonstrated the highest total porosity [(60.79±4.48)%], weight moisture content [(32.35±0.65)%], total phosphorus (TP) (1 222.66±113.41 mg·kg^-1), and available potassium (AK) (210.80±1.61 mg·kg^-1). QH-3 recorded the highest bulk density (1.69±0.13 g·cm^-3), while CM-2 showed the highest organic carbon (OC) (24.13±0.45 g·kg^-1), organic matter (OM) (41.60±0.76 g·kg^-1), cation exchange capacity (CEC) (8.89±0.35 cmol⁺·kg^-1), and maximum specific binding capacity (MBC) (544.35±2.60 mg·kg^-1). DA-2 had the highest pH value (6.88±0.05), BT-2 exhibited the highest total nitrogen (TN) (1.83±0.18 g·kg^-1) and maximum binding capacity (MBN) (54.40±3.31 mg·kg^-1), while QH-1 showed the highest nitrate nitrogen (NO₃-N) (53.34±1.12 mg·kg^-1). Significant differences in soil quality were observed across different sample plots, with comprehensive scoring and ranking effectively distinguishing quality grades, confirming HK-2 as the most fertile.

Significant discrepancies in soil physical properties and nutrient profiles were identified across the principal oil-tea camellia cultivation areas of Hainan Island. Among the sampled plots, HK-2 and HK-1 exhibited the most favorable integrated soil functionality, whereas CM-2, BT-2, and HK-2 demonstrated particularly superior performance in key nutrient indicators. In contrast, plots WZS-1, CM-1, and QH-3 were characterized by pronounced soil compaction, nutrient deficiency, or strong acidification. These findings provide a critical scientific foundation for the precision management, targeted amelioration, and sustainable utilization of soil resources in oil-tea camellia production systems..

The study aims to investigate the effects of climatic factors and interspecific competition on the radial growth of Pinus koraiensis, and to provide scientific support for predicting forest productivity and carbon sink potential under future climate change, as well as the conservation and sustainable management of regional forest resources.

Pinus koraiensis trees from two national nature reserves (Xiaobeihu and Xilinhe) in the mountainous eastern Heilongjiang Province were selected as research materials. Dendrochronological techniques were adopted to acquire radial growth data. Combined with meteorological datasets and neighborhood competition indices, correlation analysis and linear mixed-effects models (LMM) were applied to quantify the independent impacts of climate and competition on the radial growth of Pinus koraiensis. Variance decomposition was further performed to calculate their relative contributions, so as to explore the effects of climatic conditions and neighborhood competition on radial growth as well as corresponding regional disparities.

1) The radial growth of Pinus koraiensis in the Xiaobeihu study area showed significantly positive correlations with temperatures of the previous winter and current spring. Linear mixed-effects model (LMM) outputs indicated that the diameter at breast height (DBH) of competing trees achieved the optimal fitting performance with cumulative radial growth over the past 20 years; 2) Radial growth of Pinus koraiensis in the Xilinhe study area was primarily controlled by March temperature of the current year. LMM results revealed that DBH of neighboring competitive trees had the best fitting effect with cumulative growth over the recent 10 years; 3) The contribution proportions of climatic factors and inter-tree competition differed along the latitudinal gradient. With increasing latitude, the relative contribution rate of climate rose from 39% to 88%, while that of competition decreased from 61% to 11%.

This study indicates that the dominant factor regulating radial growth of Pinus koraiensis shifts from biotic competition to climatic limitation along mountainous eastern Heilongjiang. Thinning can alleviate competitive pressure in low-latitude forest stands, while high-latitude forests should be alert to growth stress induced by spring warming.

Aiming at the industrial problems of low yield, low efficiency and high labor cost in the management of Camellia oleifera forests, this study explored the regulatory effects of mechanized fertilization in autumn on photosynthetic carbon assimilation capacity, oil synthesis and yield of four major promoted C. oleifera cultivars in Hunan Province, so as to provide a theoretical and technical basis for yield and quality improvement as well as precision fertilization of C. oleifera.

Fourteen-year-old C. oleifera forests of four cultivars, namely ‘Huashuo’, ‘Huajin’, ‘Huaxin’ and ‘Xianglin 210’, were selected as test materials. The mechanized fertilization experiment was conducted in late September 2024. Three treatments were set up, including compound fertilizer (CF), phosphorus-potassium fertilizer (PP) and no-fertilizer control (CK). Photosynthetic gas exchange parameters (net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO₂ concentration, water use efficiency, etc.), chlorophyll content, yield per unit area, fruit oil content and fatty acid composition were determined in late October before fruit harvesting and early December.

Compared with CK, CF treatment increases the chlorophyll content, net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, water use efficiency, kernel oil content, oleic acid proportion, linoleic acid proportion and total polyphenol content of all C. oleifera cultivars in late October. In particular, the chlorophyll content of ‘Huaxin’ and ‘Huajin’ is significantly improved (P<0.05), and the net photosynthetic rate and water use efficiency values of ‘Huaxin’, ‘Huashuo’ and ‘Xianglin 210’ also rise significantly (P<0.05). PP treatment extremely and significantly enhances the chlorophyll content of two late-maturing cultivars (‘Huashuo’ and ‘Xianglin 210’) (P<0.05), promotes linoleic acid synthesis in ‘Huaxin’, ‘Huajin’ and ‘Xianglin 210’, and markedly improves the yield of ‘Xianglin 210’. In early December, compared with CK, CF treatment continuously and significantly increases the chlorophyll content of ‘Huajin’, ‘Huashuo’ and ‘Xianglin 210’, and all cultivars maintain high levels of net photosynthetic rate and water use efficiency. PP treatment sustainably elevates the chlorophyll content of the two late-maturing cultivars ‘Huashuo’ and ‘Xianglin 210’ with significant differences (P<0.05).

Autumn application of compound fertilizer (CF) significantly improves the photosynthetic efficiency, chlorophyll content and oil quality of C. oleifera, which is regarded as the optimal fertilization scheme. Phosphorus-potassium fertilizer (PP) exerts remarkable effects on linoleic acid synthesis, yield and kernel oil content of ‘Huaxin’, ‘Huajin’ and ‘Xianglin 210’. In summary, compound fertilizer is recommended as the first choice for field application, and phosphorus-potassium fertilizer can be additionally applied before fruit harvesting according to the botanical characteristics of specific cultivars.

This study aims to investigate the effects of water stress on the growth, biomass allocation, and physiological characteristics of seedlings of three afforestation tree species, in order to screen for species with strong drought resistance and to provide a scientific basis for water-saving and drought-resistant afforestation in arid areas.

Two-year-old seedlings of Elaeagnus angustifolia, Populus euphratica, and Xanthoceras sorbifolium were subjected to four water treatments: 75%-80% of field capacity (CK), 60%-65% of field capacity (T1), 45%-50% of field capacity (T2), and 30%-35% of field capacity (T3). Seedling growth, physiological and biochemical indices, and biomass allocation patterns under water stress were systematically measured, and the differences in the responses of the seedlings of each tree species to water stress were analyzed.

1) With increasing water stress, the increments in height and ground diameter of the three tree species seedlings generally decreased. Among them, E. angustifolia seedlings exhibited the largest increments in height and ground diameter across all water treatments, and the three species showed the smallest reductions in height and ground diameter growth under the T1 treatment; 2) As water stress intensified, the root, stem, and leaf biomass of the three tree species seedlings significantly decreased, while the root-to-shoot ratio (R/S) significantly increased. Among them, X. sorbifolium seedlings exhibited the greatest increase in R/S, whereas E. angustifolia seedlings accumulated the highest root, stem, and leaf biomass across all treatments; 3) With increasing water stress, chlorophyll content and value of photosynthetic parameters such as net photosynthetic rate (Pn) and stomatal conductance (Gs) significantly decreased (P<0.05). Notably, P. euphratica seedlings had significantly higher valuse of Pn, Gs, and other photosynthetic parameters than the other two species (P<0.05), while the water use efficiency (WUE) of E. angustifolia seedlings was significantly higher than those of the other two species under the T3 treatment (P<0.05); 4) As water stress intensified, the malondialdehyde (MDA) content, osmoregulatory substance content, and the activities of superoxide dismutase (SOD) and peroxidase (POD) generally increased across the three species. Among them, E. angustifolia seedlings exhibited relatively higher chlorophyll content, osmoregulatory substance contents, and POD activity, while X. sorbifolium seedlings showed relatively higher MDA content.

Under water stress, the growth of the three tree species seedlings was inhibited to varying degrees, with multiple photosynthetic indices significantly decreasing and stress-resistant physiological indices showing an increasing trend. However, the three species were ranked in drought resistance as follows. Based on the comprehensive evaluation results using the membership function method, the drought resistance of the three tree species seedlings ranked as follows: E. angustifolia showed the strongest resistance, followed by P. euphratica, and X. sorbifolium showed the weakest resistance.

This study aims to understand the status, spatial distribution of Chinese fir king resources nationwide and their relationships with environmental factors.

ArcGIS spatial analysis method was used to study the spatial distribution pattern of Chinese fir kings across the country, and the correlations between their distribution and environmental factors such as altitude and temperature were explored.

There are 278 ancient Chinese fir trees meeting the Chinese fir king standard nationwide, among which 91, 101 and 86 trees meet the national first-, second-, and third-class ancient tree standards respectively. The quantity of Chinese fir king resources varies greatly among different distribution regions in China: 54.32% of Chinese fir kings are distributed in the eastern part of the middle zone, and 38.49% in Fujian Province. There are 18 Chinese fir kings with an age over 1 000 years, 30 with a height over 40 m, 5 with a diameter at breast height (DBH) over 2.1 m, and 24 with a crown width over 20 m. The spatial distribution of Chinese fir kings nationwide exhibits a spatial agglomeration characteristic, with high-density core distribution areas covering the junction of northern Fujian and southern Zhejiang, the junction of Guizhou, Guangxi and Hunan, and western and southern Fujian. The quantity of Chinese fir king resources is negatively correlated with the population density of the distribution area, and positively correlated with the radius of the river buffer zone in the distribution area. Most Chinese fir kings are distributed in low-hotspot areas of traditional villages and regions with an altitude of 600-900 m, and the majority grow on forestlands. The height of Chinese fir kings is significantly correlated with local temperature factors and significantly positively correlated with slope; their DBH is significantly positively correlated with local altitude; their crown width is significantly correlated with local wettest-month rainfall and altitude; and their age is significantly negatively correlated with local annual average temperature and maximum temperature of the warmest month.

Chinese fir kings across China exhibited a spatially clustered distribution, with high-density core areas mainly located in northern Fujian and southern Zhejiang, which are traditional Chinese fir-producing regions. This spatial aggregation reflects the environmental adaptability of Chinese fir and provides valuable references for the conservation of ancient Chinese fir trees and the management of Chinese fir plantations. Moreover, 65.10% of Chinese fir kings were distributed within hotspot areas of traditional villages, further demonstrating that the distinctive awareness of protecting ancient Chinese fir trees, shaped by local people's reverence for these trees, has contributed to their long-term preservation.