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A reasonable water and fertilizer supply is key to coordinating nursery stock quality improvement and environmental pollution reduction. Here, the experiment was carried out based on the combinations of four levels of water content (W), substrate available nitrogen (N), phosphorus (P), and potassium (K). The aim was to explore the combining effects of water and fertilizer on the comprehensive growth of Pinus massoniana seedlings, and to obtain the coupling optimization of water-fertilizer. The results indicate that the comprehensive growth index (CGI) of seedlings followed a linear pattern with P and a downward-opening parabola with W, N, and K. The seedling growth was not significantly affected by adjusting the input of other elements when the substrate P ≤ 32.00 mg/kg·dry substrate. Whereas when P was 128.00 mg/kg·dry substrate, the negative effects caused by low water (W was below 45%) could not be alleviated, even if moderate N and K levels were maintained. W and P had direct and significant positive effects on the growth of seedlings, while N and K had negative effects. The combination of 85–91% (W), 65.95–134.27 (N), 128.00 (P), and 215.87–234.00 mg/kg·dry substrate (K) was beneficial to seedling growth. While W of 91% combined with the N, P, and K of 57.39, 88.40, and 123.08 mg/kg·dry substrate coordinated the environmental development and seedling growth. This research showed that P is the key factor affecting the CGI of P. massoniana seedlings. which provides a reference for rational and precise fertilization during the cultivation of P. massoniana seedlings. [Display omitted] • A water-fertilizer multi-factor coupling model for the comprehensive growth of Pinus massoniana seedlings was established. • Substrate effective P is the main driving factor affecting P. massoniana seedling comprehensive growth. • The optimal combination of W, N, P, and K was determined to improve the quality of P. massoniana seedlings. • N-K, P-W, P-N, P-K have synergize effect within a reasonable interval on seeding growth, but W-N have antagonistic effect. [ABSTRACT FROM AUTHOR]

• Stand structure contributes the most to forest recruitment biomass. • Tree species diversity has a positive effect on forest recruitment biomass. • Drivers usually affect forest recruitment biomass through direct and indirect effects. Forest dynamics is largely affected by the recruitment of trees. Despite several investigations on forest recruitment biomass (FRB), it is still not well explored how tree species diversity, stand characteristics, climate, and topography regulate FRB. Moreover, there have been limited studies and discussions on FRB in typical subtropical forests in karst areas. We examined the relationship between influencing factors and forest biomass from the perspective of tree recruitment using data from 2334 Chinese National Forest Inventory (CNFI) plots in Guizhou Province. The best predictors within each group were chosen using a stepwise regression model, and the effects of five categories, including tree species diversity, stand factors (e.g., stand density), climatic factors (e.g., mean annual temperature and annual precipitation), topographic factors (e.g., elevation and slope), and plot factors (e.g., canopy density and forest composition) on FRB were determined using structural equation models (SEM). Besides this, the relative importance of each variable among five categories in determining FRB was also quantified by hierarchical partitioning analysis (HPA). Our results indicated that diversity of tree species had the highest relative importance in determining FRB (28.85 %), followed by average DBH (21.06 %), canopy density (10.29 %) based on HPA. While for five categories, stand factors contributed the most to FRB (37.04 %), followed by plot factors (29.01 %), tree species diversity (28.85 %), climatic factors (3.81 %), and topographic factors (1.29 %). Moreover, SEM showed FRB was strongly directly and significantly controlled by tree species diversity (β = 0.63, P < 0.05), while stand factors had a strong direct effect (β = 0.45, P < 0.05) and indirect effect (β = -0.78, P < 0.05). We conclude that niche complementarity is the primary mechanism driving this forest's FRB. Our findings highlight the significance of tree recruitment in maintaining subtropical forests' carbon storage capacity. Furthermore, increasing tree species diversity, particularly by combining conifers and broad-leaved trees, will encourage the recruitment of young trees. [ABSTRACT FROM AUTHOR]

• Establishing the evaluation model of soil erosion based on extenics in karst areas. • Determining the grading standard for soil erosion intensity in the karst areas. • Bedrock exposure rate is a critical index on evaluation soil loss in the karst areas. The ecological environment of karst mountainous areas is fragile, and soil erosion has become an important factor restricting the social and economic development of these regions. How can the degree of soil erosion be scientifically assessed with a reasonable evaluation method? What is effect of the ecological environmental control measures? This study used extenics to assess the degree of soil erosion in karst mountainous areas. The typical karst mountainous area of Guizhou Province was used as the research object. In this study, a soil erosion monitoring indicator system for karst mountainous areas was developed, an evaluation model based on extenics was established, and an index correlation function and comprehensive correlation function were designed to assess the soil erosion of the karst mountainous areas. The key results were as follows. In the soil erosion monitoring index system, the soil nutrient indexes, soil erosion modulus, rock exposure, diversity index, flood season rainfall, population density and natural population growth rate had significant effects on soil erosion in the karst mountainous area. Additionally, we determined the grading standards for soil erosion intensity in typical karst mountains. Finally, the evaluation model was applied to a case study. The status of water and soil conservation was as follows: XW > ML > SB > ZS. These results provide new insights into the evaluation method, namely, extenics, which is helpful for conveniently, quickly and scientifically assessing soil erosion. [ABSTRACT FROM AUTHOR]

Pine seedlings exhibit heteroblastic foliage (primary and secondary needles) during seedling development. However, few trials have studied how heteroblastic foliage influences pine seedling growth by seasonal variation. This study first investigated the anatomical differences between the primary and secondary needles of one-year-old Pinus massoniana seedlings. We measured chlorophyll fluorescence (ChlF) and evaluated the photoprotective mechanisms and light energy partitioning of these heteroblastic leaves from September to November. The results showed that the primary needles, as juvenile foliage, had a greater fraction of mesophyll tissue and stomata. In addition, the primary needles had two vascular bundles, and shorter distance from xylem and phloem to mesophyll cells, exhibiting a luxury growth strategy of rapidly obtaining high returns. The ChlF parameters indicated that the primary needles maintained a relatively high level of photoprotection by thermal dissipation (nonphotochemical quenching (NPQ)) and nonregulated energy dissipation (Y(NO)). The secondary needles, representing mature foliage, had greater area of xylem and phloem tissues. The contents of Chl b and carotenoids (Car) significantly increased in November, promoting φPo and photoprotection, which suggested that the secondary needles were more resistant to low temperatures. During the whole light response process of secondary needles, the increases in the electron transfer rate (ETR) and light energy utilization efficiency (α) helped to increase the actual photosynthetic quantum yield (Y(II)) by reducing energy dissipation by decreasing the proportion of regulated energy dissipation (Y(NPQ)) and Y(NO). Given the sensitivity of this heteroblastic foliage to environmental changes, the practical use and extension of P. massoniana for afforestation purposes should be carried out with caution. • The morphological and photosynthesis-related physiological functions of primary and secondary needles differ significantly. • The primary needles were vulnerable to damage and photosystem II inactivity from intensive light. • The photosynthetic system of secondary needles was relatively stable. • The secondary needles developed greater support and durability tissues, which is more conducive to the growth of seedling. [ABSTRACT FROM AUTHOR]

Fungi play key roles in forest ecosystems and help to shape the forest's diverse functions. However, little is known about the diversity of phyllospheric fungi or their possible relationships with fungal communities residing in different micro-environments of Pinus massoniana forests. We investigated seven different sample types: mature needles (NM), dead needles (ND), needles falling as litter (L), fermenting needles (F), humus (H), top soil (0–20 cm) (TS), and secondary soil (20–40 cm) (SS). These seven fungal communities were examined and compared with ITS amplicons using a high-throughput sequencing technique. A total of 1213 fungal operational taxonomic units (OTUs) were obtained at a 97% sequence similarity level. Distinct fungal communities were associated with different sample types. A greater number of OTUs were present in both NM and F samples than those shared by both NM and TS samples, indicating that phyllospheric fungi may play crucial roles in litter decomposition. Sixty OTUs (the core microbiome) were found in all sample types, and they may probably play different ecological roles in different sample types. These findings extend our knowledge of the fungal diversity of the phyllosphere and its possible interactions with fungal communities found in distinct forest micro-habitats. • Phyllospheric fungal diversity of Pinus massoniana was firstly investigated. • Fungal communities varied among differ micro-environments in P. massoniana forests. • Phyllospheric fungal community shared more OTUs with fermenting litter than soil. • A core microbiome composed of sixty OTUs was identified in P. massoniana forest. • The core microbiome may play a vital role in organic matter decomposition in forests, e.g., litter decomposition. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effects of biochar on surface and underground erosion were investigated. • The effects were dependent on the amount of biochar applied. • Successive rainfall played a key role in the response of erosion to biochar application. • Biochar may reduce underground runoff. Biochar may affect soil erosion by affecting soil structure and has received attention, but its role in karst areas with complex runoff and soil loss processes at the surface and underground is poorly understood. The objective of this study was to investigate the runoff and soil loss characteristics at the surface and underground after two years of soil amendment by corn straw biochar on karst slopes. The rainfall experiments were conducted on a simulated karst microplot in the laboratory. Three biochar application rates, i.e., 15, 30 and 60 t ha−1, were used, and no biochar application measure served as the control (hereafter called T1, T2, T3, CK). The runoff and soil loss samples from the surface and underground were collected under four successive rainfall events with 24 h intervals. The rainfall intensity was 50 mm h−1, and the duration of each rainfall event was 90 min. The results showed that biochar significantly increased the surface runoff (SR) rate (P < 0.05) and surface soil loss compared to the CK. The rates of subsurface runoff (SF) and underground leakage runoff (UFR) decreased significantly after biochar application compared with CK (P < 0.05). The mean UFR rate of CK was 1.6–31.5 times higher than that of T1, T2 and T3, suggesting that biochar application increased surface runoff while decreasing underground runoff. SR accounted for the largest proportion of total runoff (18–88 %), followed by SF (3–30 %) and UFR (1–18 %), which depended on biochar application rates and rainfall events. In addition, in the first and second rainfall events, compared to the CK, biochar application significantly increased the SR rate (P < 0.05), and the increment increased with increasing biochar application amount. However, from three to four rainfall events, no significant difference (P > 0.05) in SR was observed among the four treatments; meanwhile, no obvious regularity was found between different rainfall events for T1-T3, suggesting that successive rainfall is an important factor affecting SR, while it slightly affected SF and UFR. Regression analysis showed that the changes in surface soil loss with increasing SR rate could be described by a power function (P < 0.05) for CK, T1 and T2. Our results indicate that biochar may reduce underground runoff on karst slopes, which means that soil amendment by biochar may be beneficial in karst areas with serious underground leakage. [ABSTRACT FROM AUTHOR]

Gibberellins (GAs) play a crucial role in regulating secondary growth in angiosperms, but their effects on the secondary growth of gymnosperms are rarely reported. In this study, we administered exogenous GA 3 to two-year-old P. massoniana seedlings, and examined its effects on anatomical structure, physiological and biochemical changes, and gene expression in stems. The results showed that exogenous GA 3 could enhance xylem development in P. massoniana by promoting cell division. The content of endogenous hormone (including auxins, brassinosteroids, and gibberellins) were changed and the genes related to phytohormone biosynthesis and signaling pathway, such as GID1 , DELLA , TIR1 , ARF , SAUR , CPD , BR6ox1 , and CYCD3 , were differentially expressed under GA 3 treatment. Furthermore, GA 3 and BR (brassinosteroid) might act synergistically in promoting secondary growth in P. massoniana. Additionally, lignin content was significantly increased after GA 3 treatment accompanied by the express of lignin biosynthesis related genes. PmCAD (TRINITY_DN142116_c0_g1), a crucial gene involved in the lignin biosynthesis, was cloned and overexpressed in Nicotiana benthamiana , significantly promoting the xylem development and enhancing stem lignification. It was regarded as a key candidate gene for improving stem growth of P. massoniana. The findings of this study have demonstrated the impact of GA 3 treatment on secondary growth of stems in P. massoniana , providing a foundation for understanding the molecular regulatory mechanism of stem secondary growth in Pinaceae seedlings and offering theoretical guidance for cultivating new germplasm with enhanced growth and yield. • Exogenous GA 3 enhances xylem development in P. massoniana by promoting cell division. • GA 3 and BR might act synergistically in promoting secondary growth in P. massoniana. • GA 3 changes the expression of lignin biosynthesis related genes and promotes lignin synthesis to regulate the secondary growth of P. massoniana. • PmCAD was regarded as a key candidate gene for improving secondary growth of P. massoniana. [ABSTRACT FROM AUTHOR]