Haibo Hu’s research while affiliated with Nanjing Forestry University and other places

Carya illinoinensis is a relatively water-tolerant species widely planted in areas with high flood risk. Evaluating its adaptation strategies and tolerance thresholds is crucial for ecological restoration in the context of climate change. In this study, five treatments were applied to 1-year-old C. illinoinensis seedlings in a potting simulation experiment: T1 (field capacity: 75%), T2 (5 cm below the root collar), T3 (up to the root collar), T4 (10 cm above the root collar), and T5 (30 cm above the root collar). The flooding episode lasted for 4 months and was followed by a recovery period of 6 months. The results show that, at the end of flooding, total biomass (TB), stem-mass ratio (SMR), malondialdehyde (MDA), soluble protein (SP), superoxide dismutase (SOD), and catalase (CAT) were significantly increased in all the flooded groups (T2–T5) compared to the control (T1), while the root-to-shoot ratio (RSR), root-to-mass ratio (RMR), leaf-to-mass ratio (LMR), and leaf-mass fraction (LMF) were significantly decreased. Although survival in the high stress group (T5) temporarily decreased to 83.3% (T1–T4 remained 100%), survival in all treatment groups fully recovered (100%) after recovery. Significant decreases (p < 0.001) were observed when comparing post-recovery to end-flooding levels within each flooded group (T2–T5), with reductions ranging: LMR (21.0–30.8%), REL (14.0–26.7%), MDA (16.1–25.3%), SP (42.2–67.3%), SOD (27.6–49.8%), and CAT (47.0–61.3%) across treatments. At this time, T5 showed lower TB and higher MDA, soluble sugars (SS), and SP compared to T1. PCA analysis indicated that the damage ranked as T5 > T4 > T3 > T2 > T1 at the end of flooding, and as T5 > T1 > T4 > T3 > T2 at the end of recovery. Therefore, it could be concluded that 1-year-old C. illinoinensis exhibits high flooding tolerance, with self-recovery thresholds below the T5 treatment, making it suitable for ecological restoration in flood-prone areas.

Tropical monsoon countries like Bangladesh have experienced erratic spatiotemporal rainfall distribution, heavy rainfall, and extensive erosion in recent decades. The erosive nature of the soil in the country poses a serious ecological problem. However, there is a lack of studies on the spatiotemporal distribution of rainfall erosivity and precipitation concentration trends in Bangladesh. This study intends to investigate the Rainfall erosivity over the past three decades in Bangladesh. Using the Precipitation Concentration Index (PCI) and the Modified Fournier Index (MFI), this study attempted to demonstrate precipitation concentration and erosivity distribution during 1991–2020. The PCI and MFI indices were calculated using monthly precipitation records from 30 observatories nationwide. PCI values ranged between 15.43% and 21.04%, indicating substantial irregularity in rainfall across Bangladesh, while the MFI value higher than 98 shows a very high erosion capacity of rainfall in a shorter period. The mean annual rainfall erosivity factor (R-factor) found 865 MJ mm ha− 1 hr− 1 y− 1 with a range of 711.89–1019.97 MJ mm ha− 1 hr− 1 y− 1, suggesting moderate to higher erosivity potential in annual rainfall. All the stations exhibited higher erosivity values in monsoon (597.673–902.893 MJ mm ha− 1 hr− 1 y− 1), followed by pre-monsoon (325.779–436.599 MJ mm ha− 1 hr− 1 y− 1) and post-monsoon (166.67–241.52 MJ mm ha− 1 hr− 1 y− 1). Higher rainfall erosivity is concentrated in Bangladesh’s mid-central to northeastern region, while the southwest, northeast, and southeastern areas are at higher risk of monsoon rainfall erosivity. Though decreasing trends in annual rainfall erosivity were observed in 26 stations, monsoon and post-monsoon rainfall erosivity showed an increasing trend in 19 and 8 stations, respectively. The outcome of the current study is expected to help address the challenges of climate change and sustainable development issues in Bangladesh and similar climate-vulnerable countries around the world.

Establishing road shelter forests is a key method to reduce traffic noise pollution. However, the characteristics of various types of road shelter forests and their effectiveness in reducing traffic noise remain extensively unexplored. This study focused on five types of pure road shelter forests (PFs) and one type of mixed coniferous broad-leaved forest (MCBLF). By conducting field noise monitoring and spectrum simulations, we analyzed average mass density, additional noise reduction and economic benefits. With a forest belt width of 60 m, the MCBLF reduced additional noise by 6.6 dB(A). Additionally, Forest height, crown shape, average mass density and noise frequency were all positively linked to noise reduction. The width of shelter forests was the main factor affecting noise reduction. Linear regression analysis results showed that cumulative mass surface density was a significant factor in noise reduction (p < 0.01, R² = 0.93). Furthermore, the type and composition of the shelter forest had indirect effects on noise reduction. The MCBLF had better noise-reducing effects compared to both broad-leaved PFs and needle-leaved PFs due to its more complex structure. Interestingly, as the forest belt became wider, the noise reduction benefits per unit area decreased, implying that a 10 m wide forest belt offered higher economic returns. Considering that a 10 m wide shelter forest belt did not meet noise reduction requirements. This study suggested that the 20 m wide MCBLF was an optimal choice as an urban road shelter forest, providing both effective noise reduction and maximized economic benefits. Our findings provide a basis for the construction and sustainable development of road shelter forests with noise reduction functions.

Warming significantly impacts soil respiration in terrestrial ecosystems, thereby altering global carbon cycle processes. Numerous field experiments have investigated the effects of warming on soil respiration (Rs), but the results have been inconsistent due to various factors such as ecosystem type, soil warming amplitude, duration, and environmental conditions. In this study, we conducted a meta-analysis of 1339 cases from 70 studies in terrestrial ecosystems to evaluate the response of Rs, heterotrophic respiration (Rh), and autotrophic respiration (Ra) to global warming. The results indicated that Rs, Rh, and Ra increased by 13.88%, 15.03%, and 19.72%, respectively, with a significant rise observed across different ecosystems. Generally, Rs increased with rising temperatures within a specific range (0–4 °C), whereas higher temperatures (>4 °C) did not significantly affect Rs. Moreover, Rs, Rh, and Ra exhibited an initial increase followed by a decrease with prolonged duration, indicating an adaptive response to climate warming. Additionally, Rs and Rh exhibit significant seasonal variations, with levels in winter being markedly higher than in summer. Furthermore, environmental factors exerted direct or indirect effects on soil respiration components. The factors’ importance for Rs was ranked as microbial biomass carbon (MBC) > mean annual temperature (MAT) > mean annual precipitation (MAP), for Rh as soil organic carbon (SOC) > MBC > MAT > MAP, and for Ra as belowground biomass (BGB) > aboveground biomass (AGB) > SOC. Future research should focus on the interactions among explanatory factors to elucidate the response mechanisms of soil respiration under global warming conditions.

In recent years, the invasion of Phyllostachys edulis has intensified. This study selected Phyllostachys edulis, Phyllostachys edulis–Quercus acutissima mixed and Quercus acutissima forest areas and analyzed the changes in soil bulk density, porosity, water-holding capacity, pH, soil organic carbon (SOC), soil readily oxidized organic carbon (ROC), soluble organic carbon (DOC) and microbial biomass carbon (SMBC). Then, we obtained the Chao index, Shannon index and Simpson index and analyzed the relationship between microbial α diversity, β diversity and community composition, abundance and structure and between microbial community changes and environmental factors. The results showed that soil with the invasion of Phyllostachys edulis, soil pH, water content, capillary water capacity and total porosity of surface soil increased significantly by 4.35%, 18.71%, 16.37% and 14.56%, respectively, compared with the Quercus acutissima forest, while soil bulk density, organic carbon, microbial biomass carbon and soluble organic carbon decreased significantly by 7.27%, 18.43%, 61.12% and 61.90%. Soil readily oxidized organic carbon decreased at first and then increased. The soil community richness and diversity of the Phyllostachys edulis forest were significantly greater than those of the other two stands. Soil pH and organic carbon content were the main factors affecting the changes in the soil microbial community. Therefore, the invasion of Phyllostachys edulis improved soil water retention, while soil pH had the greatest effect on the microbial community, followed by soil bulk density and organic carbon, and water content had the smallest effect.

Sea level rise due to glacier melting caused by climate warming is a major global challenge, but the mechanism of the effect of salinity on soil carbon (C) mineralization in different land types is not clear. The pathways by which salinity indirectly affects soil carbon mineralization rates need to be investigated. Whether or not the response mode is consistent among different land-use types, as well as the intrinsic links and interactions between soil microbial resource limitation, environmental stress, microbial extracellular enzyme activity, and soil carbon mineralization, remain to be demonstrated. In this paper, three typical land-use types (wetland, forest, and agroforestry) were selected, and different salinity levels (0‰, 3‰, 6‰, and 32‰) were designed to conduct a 125-day laboratory incubation experiment to determine the soil CO2 release rate, soil physicochemical properties, and soil enzyme activities, and to correlate C mineralization with biotic and abiotic factors. A correlation analysis of soil physical and chemical properties, extracellular enzyme activities, and carbon mineralization rates was conducted to investigate their intrinsic linkages, and a multiple linear regression of C mineralization at different sites was performed to explore the variability of mineralization among different site types. Structural equation models were established in the pre- and post-incubation stages to study the pathways of soil C mineralization at different incubation times, and the mechanism of mineralization was further verified by enzyme stoichiometry. The results showed that, at the end of 125 days of incubation, the 32‰ salinity addition reduced the cumulative mineralization of forest and agroforestry types by 28.41% and 34.35%, respectively, compared to the 0‰ salinity addition. Soil C mineralization in the three different land-use types was highly correlated with the active C fractions of readily oxidizable C (ROC), dissolved organic C, and microbial biomass C (MBC) in the soil, with the standardized coefficients of multivariate linear regression reaching 0.67 for MBC in the wetland and −0.843 for ROC in the forest. Under long-term salinity additions, increased salinity would reduce the microbial respiratory quotient value by inhibiting β-glucosidase activity, thus indirectly affecting the rate of CO2 release. With added salinity, the mineralization of non-saline soil was more susceptible to the inhibitory effect of salinity, whereas the mineralization of salinized soil was more controlled by soil C pools.

Agroforestry, as a phytoremediation measure, shows great potential for mitigating land degradation by constructing multidimensional and efficient agroforestry composite systems through regulating the microenvironment of agroforestry sites and improving soil properties. However, the effects of different agroforestry composite management modes on saline soils and the interactions between soil–plant systems under salt stress conditions in coastal areas remain largely unexplored. In this study, two salt‐tolerant tree species (Sapium sebiferum (Linn.) Roxb and Zelkova serrata (Thunb.) Makino) and four crop species (Medicago sativa, Sesbania cannabina, Sorghum bicolour, and Avena sativa) were selected for intercropping in eight composite patterns via field experiments, with dynamics of soil physicochemical properties and crop photosynthesis observed. The results showed that treatments intercropped with M. sativa had the highest soil bulk density range (1.41–1.48 g cm⁻³). The dynamics of topsoil (0–10 cm) chemical properties showed similar change patterns among treatments, whereas those of the 10–40 cm soil chemical properties (especially soil pH, soil organic matter [SOM], and total nitrogen [TN]) showed heterogeneity. Moreover, planting S. sebiferum (L.) Roxb under the same crop conditions increased tree height growth rate and survival rate by 75%–114% and 14%–33%, respectively, relative to planting Z. serrata (T.) Makino. Furthermore, a significant negative correlation was observed between soil moisture with crop intercellular CO2 concentration (λ = −0.77), while significant positive correlations were found between crop net photosynthetic rate (Pn) with soil TN (λ = 0.71), as well as SOM with atmospheric CO2 content (λ = 0.72). Structural equation modeling showed significant direct effects between tree height growth rate with soil TN and SOM. Soil moisture (λ = 0.47) and tree height growth rate (λ = 0.53) were dominant drivers of crop Pn. Our findings provide useful information for the prevention of coastal saline soil degradation and sustainable development of agroforestry.