Shucai Zeng

Excessive and unregulated management of water and fertilizer limits the productivity of Chukrasia tabularis ( C. tabularis ) plantations in subtropical regions. A two-factor factorial potted experiment was conducted using one-year-old C. tabularis seedlings. Three soil water content levels (95%, 75%, and 55% field capacity) and four compound fertilizer rates (0, 6, 12, and 18 g pot ⁻¹ ) were established, with the treatment of 75% field capacity and 0 g pot ⁻¹ fertilizer serving as the control (CK). Soil water content emerged as the dominant factor controlling C. tabularis seedling growth; furthermore, water and fertilizer exhibited a highly significant interaction effect on total biomass and root dry weight ( p < 0.001). At the 12 g pot ⁻¹ fertilizer rate, seedlings grown at 55% field capacity produced 35% more total biomass than those at 75% field capacity, and 224% more than CK. It also raised root dry weight by 32% over the control. But 95% field capacity reduced growth under all fertilizer treatments. Under the 55% field capacity condition, nitrogen and potassium accumulation at the 12 g pot ⁻¹ fertilizer rate increased by 701% and 318%, respectively, compared to CK. In contrast, the 95% field capacity condition caused severe root hypoxia and nutrient leaching, effectively negating the benefits of fertilization and leading to negative apparent fertilizer use efficiency for phosphorus and potassium. At 55% field capacity, the observed CH ₄ patterns suggested a potential shift from net emission to net uptake under selected treatments. A combined PCA-EWM-TOPSIS model demonstrated that a field capacity of 55% combined with 12 g pot ⁻¹ compound fertilizer achieved an optimal balance among growth benefits, resource use efficiency, and ecological trade-offs.

Understory vegetation plays a pivotal role in enhancing forest biodiversity, and its restoration is crucial for sustainable forest development, energy flow, and nutrient cycling. However, the dynamics of the biomass, diversity, and species composition of understory vegetation in plantations in south China, along with their key drivers, remain poorly understood. This study investigated four mature plantation types (Pinus massoniana, Pinus caribaea, Cunninghamia lanceolata, and mixed Chinese fir–broadleaf forests) in south China through plot surveys, environmental factor measurements, and structural equation modeling (SEM) to explore the diversity, biomass allocation patterns, and driving mechanisms of understory vegetation. The results demonstrated the following. (1) The introduced Caribbean pine forests exhibited higher shrub biomass than native Masson pine forests, which was driven by their high canopy openness favoring light-demanding species (e.g., Melicope pteleifolia, IV = 33.93%), but their low mingling degree limited herb diversity. (2) Masson pine forests showed superior shrub diversity due to their random spatial distribution and higher soil total potassium (TK) content. (3) Mixed Chinese fir–broadleaf forests achieved 24.50–66.06% higher herb biomass compared to coniferous monocultures, supported by high mingling degree, random spatial configuration, and phosphorus-potassium-enriched soil, with concurrently improved herb diversity. SEM revealed that stand structure (DBH, density, mingling degree) directly drove shrub diversity by regulating light availability, while herb biomass was primarily governed by soil total phosphorus (TP) and pH. Canopy-induced light suppression negatively affected herb diversity. We recommend optimizing stand density and canopy structure through thinning and pruning to enhance light heterogeneity alongside supplementing slow-release P fertilizers in P-deficient stands. This study provides theoretical support for the multi-objective management of south China plantations, emphasizing the synergistic necessity of stand structure optimization and soil amendment.

Field experiments were conducted on a four-year-old leaf-use ginkgo plantation in southern China to assess the impact of nine different fertilization strategies with varying N-P₂O₅-K₂O rates at three growth phases (FBD: March for bud development; FLG: May for leaf growth; FLS: July for leaf strengthening) on leaf-use ginkgo (Ginkgo biloba L.) leaf productivity and ecological economic benefits (EEBs). The results indicated that regardless of timing and rate, fertilizer application led to an increase in leaf area and thickness, resulting in higher ginkgo leaf yield. The highest fresh (215.14 g tree⁻¹) and dry (78.83 g tree⁻¹) yields were observed with 3 g N + 2.5 g P₂O₅ + 1.5 g K₂O tree⁻¹ in FLG. FLS was found to mitigate the decline in SPAD values of leaves during late summer. Furthermore, fertilized ginkgo trees exhibited higher flavonoid concentrations in leaves, enhancing profitability. However, higher fertilizer rates were associated with elevated greenhouse gas emissions, nitrogen losses and ecological costs. Despite these drawbacks, all fertilization treatments resulted in increased net economic income. Specifically, compared to no fertilization, FBD, FLG and FLS treatments boosted net income by 3.5~26.6%, 11.6~60.5% and 5.8~35.4%, respectively. Using the entropy weight TOPSIS method, it was concluded that optimizing the N, P and K fertilization rate and timing (applying 3–2.5–1.5 g tree⁻¹ of N-P₂O₅-K₂O in May) is a beneficial approach to maximize EEBs and industrial benefits in leaf-use ginkgo plantations in southern China. This study provides valuable insights into suitable fertilization patterns and management for leaf-use ginkgo plantations in southern China.

Co-application of sewage sludge (SS) with biochar in landscape/forestry soil is a common strategy for enhancing soil fertility and reducing the bioavailability of potential toxic elements (PTEs) derived from SS, such as Cd, Pb, Cu, Zn, and Ni. However, due to variability of biochar quality and uncertainties in responses of different plant species, whether the co-application benefits the landscape/forestry plant system remains elusive. Here, we tested the effectiveness of three types of biochar (SS-derived biochar (SB), rice straw-derived biochar (RB), and litter-derived biochar (LB)), which were added to soil amended with SS at 50% (w/w) at rates of 1.5%, 3%, and 4.5% as growth media for the landscape plant Aglaonema modestum (A. modestum). We analyzed the substrate’s physicochemical properties and assessed the alleviation of phytotoxicity by biochar application. A significant increase in the fertility index of substrate was observed in all the treatments with biochar addition. The addition of biochar reduced the potential mobility of PTEs while increasing their residual fraction in media. Nonetheless, it has been found that the addition of biochar has ineffective or even negative effects on A. modestum growth (height, biomass, root length) and nutrient absorption. Importantly, the reduction in root biomass and the increased activity of root antioxidant enzymes (SOD, POD, CAT, and MDA) indicate contamination stress of biochar on the roots of A. modestum. Toxic elements of concern—namely Cu, Cd, and Pb—were not significantly higher in tissues of A. modestum saplings planted in biochar-SS-amended soil. However, elevated levels of other elements that may pose toxicity concerns, such as Ni and Zn, increased in tissues at high biochar dosages. Based on the Entropy–Weight TOPSIS method, it was further confirmed that compared to the treatment without biochar, all treatments except for 3.0% LB application resulted in poorer A. modestum comprehensive growth. Our results emphasize the need for detailed research on the response of specific plants to biochar in specific environments, including plant adaptability and the unexplored toxicity of biochar, to understand the large variations and mechanisms behind these ineffective or negative effects before the large-scale co-utilization of SS and biochar in landscape/forestry soils.

Sewage sludge (SS) application to forest plantation soils as a fertilizer and/or soil amendment is increasingly adopted in plantation forest management. However, the potential risks of SS-derived heavy metals (HMs) remain a concern. Many factors, including woodland slope may affect the risks, but the understanding of this issue is limited. This research evaluated the HMs migration via surface runoff, interflow, and sediments when SS was applied in woodlands of varying slopes. We conducted indoor rainfall simulations and natural rainfall experiments to clarify the effect of slope on the migration of HMs via runoff (including surface and interflow) and sediments. In the simulated rainfall experiment, HMs lost via sediments increased by 9.79–27.28% when the slope increased from 5° to 25°. However, in the natural rainfall experiment, when the slope of forested land increased from 7° to 23°, HMs lost via surface runoff increased by 2.38% to 6.13%. These results indciate that the surface runoff water on a high slope (25°) posed high water quality pollution risks. The migration of HMs via surface runoff water or interflow increased as the steepness of the slope increased. The total migration of Cu, Zn, Pb, Ni, Cr and Cd via sediment greatly exceeded that via surface runoff and interflow. Particles ≤ 0.05 mm contributed the most to the ecological risks posed by sediments. Cd was the main source of potential ecological risks in sediments under both experimental conditions.

Considering the impacts of global climate change, paths for sustainable development are of particular importance. Biochar has multiple advantages, including but not limited to climate change mitigation, waste management, soil fertility improvement, and pollution remediation. Forest soils play a significant role in terrestrial ecosystems. The application of biochar in forest soils (ABFS) is therefore considered an essential tool for improving soil quality, capturing carbon, and reducing greenhouse gas emissions. The Web of Science Core Collection database was utilized for the bibliometric analysis of ABFS publications published between 2002 and 2022. Three bibliometric software were used to analyze bibliometrics, networks, and research directions for ABFS: Bibliometrix, VOSviewer, and CiteSpace. The analysis shows that research on ABFS is always rapidly developing. Research on ABFS is engaged globally in a complex network of collaborations, and the main research has occurred in China and the United States. Collaboration among authors is relatively diffuse. Research on ABFS involves interdisciplinary integration. In the early stages of research, the origin of biochar (history and boreal forests) and its characteristics (dynamics, nitrogen content, and chemical composition) were the focus of attention. As research progressed, more attention was given to ABFS (carbon, organic matter, vegetation, and heavy metals). Our research shows that while ABFS research has a certain history, its development trend has been consistently upward and shows no signs of declining. Thus, future research will likely concentrate on ABFS. Due to the complexity of biochar functions, ample research opportunities exist in ABFS.