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[ Objective ] The study aims to understand the population variation of leaf anatomical structure of Quercus variabilis and its relationship with environmental factors. [ Methods ] The leaves of 28 naturally distributed Q . variabilis populations in China were studied by conventional paraffin sections combined with optical microscopy. Nested analysis of variance and Pearson correlation analysis were performed to analyze the relationship between population variation of leaf anatomical structure and environmental fac- tors. [ Results ] ( 1 ) There were significant difference in the anatomic traits of Q . variabilis leaves among 28 populations , and the average coefficient of variation was 7.84%-15.16% , while the variation range of the same leaf anatomic trait varied among different populations. ( 2 ) There were significant difference among the 9 anatomic traits within and among the populations , and the average phenotypic differentiation coefficient was 37.44%. The variation of anatomic traits mainly came from within the populations. ( 3 ) Leaf thickness , upper epidermal cell thickness , palisade tissue thickness , and spongy tissue thickness were significantly positively correlated with latitude , and mean annual temperature and annual precipitation had significant effects on the upper epidermal cell thickness and palisade tissue thickness. [ Conclusion ] The re- sults show that Q . variabilis has rich genetic diversity. To adapt to low temperature and drought , Q . variabilis leaves show a trend of thickening. The results provide a theoretical basis for understanding envi- ronmental adaptation strategies of Q . variabilis.

The Qinling Mountains, the so-called "central water tower," are extremely important water resource hubs in China. The influence of the forest ecological environment on water quality is complicated. Therefore, to investigate the spatiotemporal variations in water quality, we employed a random forest model to integrate multiple key water quality indicators into one overall ranking value. Monthly monitoring data of surface runoff and atmospheric precipitation events (2003–2022) for the Huodigou stream in the Qinling Mountains were used. The results revealed that after atmospheric precipitation entered the forest ecosystem, the coefficients of variation of surface runoff for most of the selected indicators decreased, but there were significant differences among the six indicators (NO3−, Mg2+, Na+, pH, K+, Ca2+). Most of the indicators within surface runoff were positively correlated, such as those in atmospheric precipitation. However, some indices of surface runoff were negatively correlated with those of atmospheric precipitation, and there was a significant negative correlation between Ca2+ in atmospheric precipitation and Ca2+ in surface runoff and between NO3−in atmospheric precipitation and K+ and Na+ in surface runoff (p < 0.01). The water quality grade of the surface runoff generated by atmospheric precipitation through forest ecosystems was significantly improved (p < 0.001), among which the average water quality grade of surface runoff was approximately 3.6, that is, between Grade I-3 and Grade I-4, whereas the average water quality grade of atmospheric precipitation was approximately 4.5, that is, between Grade I-4 and Grade I-5. The order of improved water quality was NO3− > Mg2+ > Na+ > pH > K+ > Ca2+. Overall, our assessment revealed that from 2003 to 2022, the water quality grade in the Huodigou stream improved and was more stable. In summary, the forest ecosystem in the Huodigou stream has a significant water quality purification effect on the atmospheric precipitation it receives. Our novel criterion-based approach for categorizing the water quality of atmospheric precipitation and surface runoff offers a new tool for examining spatiotemporal stream water quality variations in the Qinling region and other mountainous areas. [ABSTRACT FROM AUTHOR]

First-principles calculations and thermodynamic theory of mixing entropy and enthalpy are employed to study the phase stability, mechanical properties, and melting points of 15 existing and hypothetical quaternary high-entropy metal diborides (HEMB 2 s) composed of boron and six group IVB and VB refractory transition metals. A phase diagram in terms of a structural parameter, δ (the lattice size difference), and two thermodynamic parameters, Δ H m i x (the mixing enthalpy) and Ω (the ratio of the entropy and enthalpy terms) is constructed. The phase diagram shows that all the 15 metal diborides satisfy the established Ω - δ criterion (i.e. Ω > --> 1 and δ < 6.6 %), suggesting that they can be formed as single-phase HEMB 2 s. While five of these equiatomic four-metal diborides were experimentally synthesized already, the remaining ten single-phase HEMB 2 s are predicted by this work. Each of the 15 quaternary HEMB 2 s is found to have high Vickers hardness and high fracture toughness, together with an ultrahigh melting point. [ABSTRACT FROM AUTHOR]

Across ecology, and particularly within microbial ecology, there is limited understanding how the generation and maintenance of diversity. Although recent work has shown that both local assembly processes and species pools are important in structuring microbial communities, the relative contributions of these mechanisms remain an important question. Moreover, the roles of local assembly processes and species pools are drastically different when explicitly considering the potential for saturation or unsaturation, yet this issue is rarely addressed. Thus, we established a conceptual model that incorporated saturation theory into the microbiological domain to advance the understanding of mechanisms controlling soil bacterial diversity during forest secondary succession. Conceptual model hypotheses were tested by coupling soil bacterial diversity, local assembly processes and species pools using six different forest successional chronosequences distributed across multiple climate zones. Consistent with the unsaturated case proposed in our conceptual framework, we found that species pool consistently affected α‐diversity, even while local assembly processes on local richness operate. In contrast, the effects of species pool on β‐diversity disappeared once local assembly processes were taken into account, and changes in environmental conditions during secondary succession led to shifts in β‐diversity through mediation of the strength of heterogeneous selection. Overall, this study represents one of the first to demonstrate that most local bacterial communities might be unsaturated, where the effect of species pool on α‐diversity is robust to the consideration of multiple environmental influences, but β‐diversity is constrained by environmental selection. [ABSTRACT FROM AUTHOR]

Leaf nutrient resorption traits are regarded as important indicators reflecting the strategy of plant nutrient conservation, yet the mechanism underlying the variation of resorption traits in different plant growth forms (PGFs) remains unclear. In order to untangle the phylogenetic and environmental influences on leaf nitrogen (N) and phosphorus (P) resorption traits between woody and herbaceous plants, we investigated N and P contents of green and senesced leaves in 53 species along an altitudinal gradient (1374–3649 m) in the Taibai Mountain of central China and estimated leaf N and P resorption efficiency and proficiency. Our results show that leaf N and P resorption efficiency (NRE and PRE) had significant positive trends with altitude in both woody and herbaceous plants (all p < 0.05); however, their altitudinal patterns of N and P resorption proficiency (NRP and PRP) were different. For woody plants, leaf NRP and NRE:PRE first decreased and then increased with altitude (p < 0.05), while NRP:PRP had the opposite trend (p < 0.05). In herbaceous plants, leaf NRP and PRP decreased but NRP:PRP increased with altitude (p < 0.05). Climatic factors exerted the major influences on the variation in leaf NRE and PRE (18.5–24.8% explained variation). However, phylogenetic taxonomy mainly affected the variation of leaf PRP and NRP:PRP (45.2% and 41.4% explained variation) in all species, NRP:PRP in woody plants (37.8% explained variation), and NRE:PRE in herbaceous plants (49.7% explained variation). In addition, leaf NRP:PRP showed a significant phylogenetic signal (Blomberg's p < 0.05). These results highlight the importance of taking PGFs and phylogenetic information into consideration when examining the interspecies variation in leaf resorption under environmental changes, which can advance our knowledge of plant nutrient utilization strategies in response to fluctuating environments and lay the groundwork for the development of complex element biogeochemical models. [ABSTRACT FROM AUTHOR]

[Objective] This study clarified the effects of nitrogen addition on decomposition of tending and thinning residues of Pinus armandi to provide scientific basis for protection and sustainable management of P. armandi forest in the Qinling Mountains. [Method] From May 2019 to May 2020, the litterbag method was applied for the study of decomposition of tending and thinning residues of Pinus armandi with nitrogen addition at different forms and levels in the Guanyinshan National Nature Reserve of Shaanxi Province. Nitrogen forms included ammonium nitrogen (NH4Cl), nitrate nitrogen (NaNO3) and mixed nitrogen (NH4NO3) and five nitrogen addition levels were N1(0. 5 g/(m2 • a)),N2(1. 25 g/(m² • a)),N3 (2. 5 g/(m² • a)), N4 (5. 0 g/(m² • a)) and N5 (10. 0 g/(m² • a)) with the control without nitrogen addition NO (0 g/(m² • a)). Three 20 mX20 m plots were set with 16 subplots in each plot. Each treatment was arranged in one subplot. Sampes were taken regularly to determine dry matter, carbon (C), nitrogen (N), cellulose and lignin contents of tending and thinning residues of P. armandi one month after the beginning. Then, annual average mass remaining rates, decomposition times of 50% and 95%, decomposition co-efficients and C/N values were calculated. [Result](1) The annual average mass remaining rates of tending and thinning residues of P. armandi with ammonium, mixed nitrogen and nitrate were 82. 47%, 81. 83% and 84. 96%,respectively, which were lower than the control of 84. 99%. (2) Compared with the control, the times required for decomposing tending and thinning residues to 50% were reduced by 0. 41 to 1. 65 years, and that for 95% were reduced by 4. 16 to 7. 15 years. (3) When nitrogen addition level was lower than 5. 0 g/(m² • a), the decomposition of tending and thinning residues was promoted, while it was inhibited when higher than 5. 0 g/(m² • a). Different forms and levels of nitrogen addition promoted the degradation of lignin. (4) With the increase of decomposition time, C content and C/N ratio of tending and thinning residues of P. armandi decreased, while N content increased. The decomposition coefficients were negatively correlated with the C/N ratio, indicating that lower C/N ratio resulted in more rapid decomposition. [Conclusion] After one year of decomposition,the decomposition of tending and thinning residues was promoted with low levels of nitrogen addition whle inhibited with high levels of nitrogen addition. The decomposition was promoted when amounts of ammonium, mixed nitrogen and nitrate were no higher than 2.5,5.0 and 1. 25 g/(m² • a), respectively. [ABSTRACT FROM AUTHOR]