Table of Content

10 September 2024, Volume 43 Issue 9

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Effects of climate warming on carbon sink of forest ecosystems: Mechanisms, methods, and progresses.

FANG Yunting, LIU Dongwei, DUAN Yihang, HUANG Kai, WANG Wenchao, QIN Yujing, WANG Ang, WANG Chao, LIU Yuqi, TU Ying

2024, 43(9):  2551-2565.  doi:10.13292/j.1000-4890.202409.043

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Forests are important carbon sinks, absorbing about 33% of the carbon dioxide released from fossil fuel combustion each year. Since 1850, global temperature has increased by 1.1 ℃, and in the future, global temperatures are likely to rise to 2.7-4.8 ℃. However, there are controversies over the direction, degree, and mechanisms of the impact of global warming on forest carbon sequestration, which seriously affects the prediction of future global climate change and the policy-making of government carbon emission control. This article summarizes the mechanisms, research methods, and main progresses of the impact of global warming on the carbon sink capacity and processes of forest ecosystems. In addition, we propose future priority research areas.





Effect of plant functional traits on soil organic matter accumulation in forests: A review.

ZHANG Qian, YANG Kai, ZHOU Changjian, ZHANG Jinxin, SU Yingjia, GAO Tian, LU Deliang

2024, 43(9):  2566-2573.  doi:10.13292/j.1000-4890.202409.027

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Plant functional traits are the individual characteristics and attributes shown by plants to adapt to environment, which affect the survival, growth, and reproduction of plants, and soil ecological functions as well. Here, we summarized literature on the relationships between plant functional traits and soil organic matter from three aspects. Firstly, we analyzed the classification of plant functional traits and clarified the relationship between plant functional traits and soil fertility. Secondly, we clarified the effects of plant functional traits on soil organic matter accumulation. The direction and magnitude of such effects were influenced by soil nitrogen and phosphorus cycling and soil carbon saturation status. We discussed the relationships between plant functional traits and soil organic matter stability and long-term soil organic matter accumulation. Thirdly, we elucidated the mechanisms of plant functional traits influencing forest soil organic matter by means of leaf litter, fine root decomposition and soil microbial community structure and function. Then, we proposed two key issues of the future research focusing on plant functional traits and soil organic matter: (1) to understand the processes and mechanisms that plant-microbial interactions influence plant functional traits and soil organic matter accumulation via advanced technology and methods; (2) to clarify the ecological processes and mechanisms driving the impacts of plant functional traits on soil organic matter accumulation under the background of global change.





Research progress in plant and soil microbial diversity in forest-grassland ecotone.

HAN Jiaxin, WANG Ruzhen, ZHANG Yuge, JIANG Yong

2024, 43(9):  2574-2586.  doi:10.13292/j.1000-4890.202409.031

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Forest-grassland ecotone is a cline of plant communities between forest and grassland. This ecotone is characterized by diverse landscape types, strong environmental heterogeneity, and evident edge effects. Forest-grassland ecotone is sensitive to global climate change, and serves as critical zones of biodiversity conservation. Because of its special habitat, above and belowground biodiversity and ecological linkages of the forest-grassland ecotone is far more complicated than other ecosystems, such as forests, grasslands and farmlands. Here, we reviewed the effects of topographic factors, nutrient cycling of ecosystems, global changes, and anthropogenic disturbances on plant diversity in forest-grassland ecotone. We also discussed the effects of land use types, nitrogen deposition, atmospheric CO₂ enrichment, litterfall, soil organic matter content, and soil depth on soil microbial diversity. Future studies should focus on research approaches that combine manipulative experiments of local scale with observations crossing environmental gradients, so as to reveal the geographical pattern and ecological mechanism of biodiversity formation in forest-grassland ecotone. Specifically, this includes how biodiversity responds to soil acidification, fire, litter composition, enclosure and grazing, and interactions of multi-factors as well as ecological linkages between above- and belowground biodiversity and degraded habitat restoration and vegetation recovery. This would provide theoretical guidance and data reference for land use and biodiversity conservation in the forest-grassland ecotone.





Research progress on functional traits of wood-decaying fungi in forest ecosystem.

XUE Jianbin, CHEN Liting, WEI Yulian

2024, 43(9):  2587-2595.  doi:10.13292/j.1000-4890.202409.008

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As the main group involved in wood decomposition, species richness of wood-decaying fungi is extremely high. They affect and regulate key ecological processes in global forest ecosystems, including nutrient cycling, soil formation and carbon budget. Functional traits reflect the response and adaptation of organisms to habitats, and can effectively link characteristics of individuals with environmental changes. Knowledge of functional traits can provide mechanistic insights into species coexistence. Here, we review key research progress on functional traits of wood-decaying fungi. The main topics of this area are as follows: the traits of wood-decaying fungi in propagation, spread and colonization, the functional traits of hyphal growth and nutrient acquisition, the formation mechanism and functional groups of fungal community diversity, and the characteristics of various enzymes and related enzyme genes during wood degradation. We introduce the commonly used functional trait indicators and measurement methods. Although previous studies have made significant progress in understanding the functional traits of wood-decaying fungi, our knowledge on fungal functional traits is not systematic and in-depth due to the abundant species and diverse traits of fungi. Uncovering the role of functional traits of wood-decaying fungal species in species coexistence, community assembly, and biodiversity maintenance, can deepen the understanding of fungal community functional mechanism.





Effects of climate warming on forest carbon pools in the Changbai Mountain Nature Reserve.

WANG Dan, WANG Wenjuan, WU Haitao, JIANG Ming, LYU Yunfeng, XUE Zhenshan

2024, 43(9):  2596-2606.  doi:10.13292/j.1000-4890.202409.021

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Climate change will affect the structure and function of forest ecosystems, bringing uncertainty in the estimation of forest carbon sequestration potential. To clarify the dynamics of forest carbon pools in the Changbai Mountain under climate warming, we utilized the spatially explicit landscape model LANDIS-Ⅱ to simulate the changes in forest carbon sequestration potential and carbon stock in the Changbai Mountain Nature Reserve from 2000 to 2100 under three future climate scenarios (SSP1-2.6, SSP3-7.0, SSP5-8.5) and the current climate scenario (SSP0-1.0). The results showed that: (1) Net primary productivity (NPP) of forests would continue to increase in the future. By 2100, NPP under the three future climate scenarios is higher than that under the SSP0-1.0 scenario (NPP of 1010 g C·m^-2·a^-1). However, there are no significant spatial-temporal variations in NPP among the different climate scenarios. (2) The total carbon stock in forests shows an increasing trend under all climate scenarios. Compared to the SSP0-1.0 scenario, the SSP1-2.6 scenario leads to an increase in plant carbon pools but a decrease in soil carbon pools and detritus carbon pools, resulting in a 2.1% decrease in total carbon stock. Under the SSP3-7.0 and SSP5-8.5 scenarios, all carbon pools (plant, detritus, and soil) decrease, leading to reductions of 3.4% and 4.2% in total carbon stock, respectively. (3) The carbon pools of high-elevation forests are more sensitive to future climate warming than low-elevation and middle-elevation forests. The response of plant carbon pools to climate change shows an altitudinal gradient effect. Plant carbon pools significantly decrease at low-altitude regions and are promoted at high-altitude regions under all three future climate scenarios. This study could provide a reference for long-term forest management and the enhancement of forest carbon sequestration potential in the Changbai Mountain.





Changes of non-structural carbohydrates of Pinus sylvestris var. mongolica under different stand densities.-

WANG Kai, XING Shiqi, ZHANG Risheng, LIU Jianhua

2024, 43(9):  2607-2614.  doi:10.13292/j.1000-4890.202409.019

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To understand effects of stand density on the allocation of non-structural carbohydrates (NSC) in Pinus sylvestris var. mongolica, we analyzed concentrations of NSC and its components (soluble sugars and starch) in different organs of 39-year-old P. sylvestris var. mongolica monoculture with different stand densities (490, 750, 1110, 1550, 1800, 1930, 2560 and 3520 trees·hm^-2). The results showed that NSC concentrations in needles, branches and roots ranged from 50.51 to 82.12 mg·g^-1, from 58.24 to 76.28 mg·g^-1, and from 13.90 to 56.82 mg·g^-1, respectively. When stand density increased from 490 to 1550 trees·hm^-2, soluble sugars concentration of young needles decreased, starch concentration increased, and NSC concentration remained stable. When stand density increased from 1550 to 3520 trees·hm^-2, concentrations of soluble sugars, starch and NSC in young needles showed downward trends. With the increases of stand density, concentrations of soluble sugars, starch and NSC in old needles first increased and then decreased, and concentrations of soluble sugars and NSC in young and old branches exhibited trends of increasing-decreasing-increasing, while concentrations of soluble sugars, starch and NSC in the roots first reduced and then rose. The optimal management density for mature P. sylvestris var. mongolica plantation should be 1110 trees·hm^-2, in which concentrations of soluble sugars and NSC in young needles and branches were high and reached the maximum in old needles and branches, indicating more carbohydrate production and branch growth promotion.





Variation in ecological stoichiometry of Populus × xiaozhuanica cv. Zhangwu seedlings under natural drought.

XING Shiqi, WANG Kai, PANG Yingying, LYU Linyou

2024, 43(9):  2615-2622.  doi:10.13292/j.1000-4890.202409.004

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To understand the variations of nutrients and stoichiometric ratios in Populus ×xiaozhuanica cv. Zhangwu seedlings under drought stress, we grew the seedlings in pots under a condition of continuous natural drought. Carbon (C), nitrogen (N), phosphorus (P), and potassium (K) contents in different organs (leaf, stem, root) were measured at 0, 6, 12, 18 and 24 days after drought, and the correlations of elements among organs were analyzed. Results showed that N and K contents and C∶P and N∶P decreased but P content and C∶N and C∶K increased in all organs after 6 days of the drought. N content and C∶P and N∶P increased but P content decreased in all organs when the drought lasted from the 6th day to the 12th day. Root C content, C∶N, C∶P and C∶K showed downward trends when the drought lasted from the 12th day to the 24th day. Under continuous drought treatment, there were significant positive correlations in N or P content among leaves, stems, and roots, as well as C content between leaves and stems, and K content between leaves and roots. P.× xiaozhuanica cv. Zhangwu seedlings could adjust the stoichiometry of C, N, P, and K in various organs to adapt to the gradually intensified drought stress. First, C supply for roots increased, K transferred from stems to leaves and roots, and N content in each organ increased to resist drought stress. Finally, C supply for roots decreased, N consumption increased, and P and K accumulated in the seedlings.








Response of photosynthetic characteristics of Pinus koraiensis seedlings to low temperature and light stress.

CHEN Qingda, DIAO Siyue, HU Jingge, ZHAO Tongbin, ZHU Chengyao, LI Xiufen

2024, 43(9):  2623-2631. 

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In the context of global climate warming, Korean pine (Pinus koraiensis) seedlings with advanced growth are highly susceptible to low temperature in spring, which in turn, affecting regeneration. To explore the impacts of extremely low temperatures in spring on the early growth of Korean pine seedlings, we conducted a manipulative experiment to investigate the combined effects of spring low temperature (T1: 10 ℃, T2: 6 ℃, T3: 2 ℃, T4: -2 ℃, T5: -6 ℃) and different light intensities (L1: 150 μmol·m^-2·s^-1; L2: 750 μmol·m^-2·s^-1; L3: 1500 μmol·m^-2·s^-1) on photosynthetic and fluorescence characteristics of one-year-old Korean pine seedlings. The results showed that: (1) With decreasing temperature, photosynthetic variables tended to decrease. At 6 ℃ and 10 ℃, photosynthetic capacity (net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), transpiration rate (T_r)) was highest in moderate light intensity (750 μmol·m^-2·s^-1), and all of which were higher than under low light intensity (150 μmol·m^-2·s^-1) and high light intensity (1500 μmol·m^-2·s^-1) treatments. (2) F_v/F_m, Φ_PSⅡ, qP and ETR significantly decreased with decreasing stressed temperatures, while F_o and NPQ gradually increased. The PSII photosynthetic system suffered the least damage at light intensity of 750 μmol·m^-2·s^-1, while light intensity (L3) under low-temperature stress (<2 ℃) caused the most extensive damage to PSII photosynthetic system. (3) Under low temperature stress, both low and high light intensity environments exacerbated the damage to the photosynthetic system. Both stomatal and non-stomatal limiting factors contributed to the decline in P_n, with most severe damage under high light conditions. Based on these results, we proposed management measures, such as shading and insulation, establishment of mixed forests of coniferous and broad-leaved tree species, and thinning, to avoid the impacts of low temperatures, aiming to provide scientific basis for the early growth and regeneration of Korean pine seedlings.



Effects of stand type and decomposition position on leaf litter nutrient dynamics in subtropical plantations of China.

WU Panpan, ZHANG Yan, JIANG Lingxin, LI Rui, MAO Rong

2024, 43(9):  2632-2640.  doi:10.13292/j.1000-4890.202409.032

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Nutrient release from decomposing litter is a main source of soil nutrients. Consequently, litter nutrient dynamics are of great importance to maintain soil fertility and stand productivity in forests. However, most previous studies have focused on nutrient dynamics of litter decomposing on forest floor, but ignored nutrient dynamics of litter decomposing in the air. Moreover, little is known about the dynamics of litter medium nutrient elements such as calcium and magnesium in forests compared with the macronutrients such as nitrogen and phosphorus. In this study, we selected leaf litter of four common afforestation species (Pinus massoniana, Pinus elliottii, Liquidambar formosana, and Schima superba) in subtropical regions and used the litterbag method to investigate the effects of stand type (P. massoniana, P. elliottii, L. formosana, and S. superba plantations) and decomposition position (in the air and on the forest floor) on litter nitrogen, phosphorus, calcium, and magnesium dynamics. The results showed that, across the four plantations, leaf litter nitrogen exhibited an initial immobilization and subsequently a net release during 360-day decomposition. However, litter phosphorus remaining during decomposition initially increased and then decreased in P. massoniana and P. elliottii plantations, but showed a net decline in the L. formosana and S. superba plantations. In addition, litter calcium and magnesium showed a gradual net release during 360-day decomposition in the four plantations. Litter nitrogen, phosphorus, calcium, and magnesium remaining of L. formosana and S. superba was greater in the air than on the forest floor, whereas P. massoniana and P. elliottii litter nitrogen, phosphorus, calcium, and magnesium remaining did not exhibit a consistent changing pattern between in the air and on the forest floor during decomposition. These findings suggest that stand type and decomposition position are important determinants of litter nutrient release and highlight that the release patterns of litter macronutrients and medium nutrients differ during decomposition. These observations will be beneficial to understanding nutrient cycling and designing appropriate nutrient management practices in subtropical plantations.





Effects of litter management on chemical structure and thermal stability of soil organic carbon in a Chinese fir forest.

CHEN Chunyu, CHEN Fusheng, ZHENG Zhiyu, PENG Yitong, LIU Qiao, WANG Shengnan, WANG Fangchao

2024, 43(9):  2641-2649.  doi:10.13292/j.1000-4890.202409.024

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Soil organic carbon (SOC) is closely related to forest land maintenance and carbon sink function. Small fluctuations in soil SOC can cause significant changes in atmospheric CO2 concentrations. As a main management measure of plantation, how and why litter management affects the chemical structure and stability of SOC remains unclear. In this study, a field control experiment was conducted in a Chinese fir (Cunninghamia lanceolata) forest with three treatments, namely, litter addition, litter removal and control, following a completely randomized block design. After 6 years of treatment, soil samples from three layers (0-10 cm, 10-20 cm, and 20-40 cm) were collected, and the chemical structure of SOC was determined by transmission Fourier-transform infrared spectroscopy (T-FTIR). The thermal stability of SOC was analyzed by thermogravimetry (TG) and differential scanning calorimetry (DSC), and the soil physicochemical properties were determined. The results showed that (1) Litter removal significantly decreased NH₄⁺-N concentration in the 0-10 and 20-40 cm layers and NO₃^--N concentration in the 10-20 cm layer; (2) Litter addition significantly decreased the relative proportion of alcohols and phenols in SOC and increased the relative proportion of aromatics; (3) Litter addition significantly decreased the thermal stability coefficient (H), and litter removal treatment significantly increased the temperature corresponding to 50% mass loss during SOC combustion (Tg-T50); (4) The NH₄⁺-N and NO₃^--N concentrations were significantly negatively correlated with Tg-T₅₀. Alcohol phenols and aromatic groups were positively and negatively correlated with H, respectively. In summary, litter removal improved the thermal stability of SOC by decreasing N effectiveness, while litter addition improved thermal stability of SOC by decreasing the readily decomposable carbon and increasing the formation of refractory carbon in the chemical molecular structure of SOC. Our results can provide a scientific basis for subtropical plantation to achieve “carbon neutrality” by improving soil carbon sink function through litter management.





Mixed Cunninghamia lanceolata-Michelia macclurei plantation decreased soil bacterial residue accumulation in topsoils.

JING Yanli, WANG Qingkui

2024, 43(9):  2650-2657.  doi:10.13292/j.1000-4890.202409.036

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Microbial residues are major contributors to soil organic carbon (SOC). However, their responses to mixed plantation forests remain unclear. In this study, we examined the accumulation of microbial residues in soil at depths of 0-20 cm in  Cunninghamia lanceolata-Michelia macclurei mixed plantation and C. lanceolata pure plantation by analyzing amino sugars and using the ratio of Gram-positive to Gram-negative bacteria to determine the conversion coefficient of bacterial residues. The results showed that bacterial residues at depths of 0-10 cm were 25.3% lower in the mixed plantation than that in the monoculture, leading to SOC being 11% lower in the mixed plantation. The lower accumulation of bacterial residues in the mixed plantation was mainly due to the lower accumulation in macroaggregates. However, the accumulation of total microbial residues and their contribution to SOC did not differ between the mixed plantation and monoculture. These results indicate that the M. macclurei and C. lanceolata mixed plantations after 35 years would reduce bacterial residues as well as soil carbon sequestration, which would be detrimental to the long-term maintenance of soil fertility.





Identification of preservation rate for farmland shelterbelt from high-resolution remote sensing imagery.

DENG Rongxin, XING Zefeng, LI Ying, ZHANG Xing, YANG Gao, LI Shiming, JIA Menghao

2024, 43(9):  2658-2666.  doi:10.13292/j.1000-4890.202409.011

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The preservation rate of farmland shelterbelts reflects the integrity of the shelterbelt structure, determining the protection effectiveness of shelterbelts. Although traditional field measured data of shelterbelt preservation rate are accurate, this method could not meet the needs for rapid and large-scale monitoring. It is of great importance to obtain the information of shelterbelt preservation rate by remote sensing, which could be significantly helpful for the structural and functional research and precise management of farmland shelterbelts. In this study, using the shelterbelt vector line and vegetation fraction data extracted from Jilin-1 high-resolution multispectral remote sensing images, a set of ordered points were extracted along the belt orientation and belt width directions by considering each shelterbelt as a two-dimensional matrix. The shelterbelt boundary was recognized by analyzing the waveform characteristics, and the shelterbelt pixels were determined by the threshold value. Finally, the preservation rate of farmland shelterbelts was identified from the remote sensing image, which were further verified by the reference data (sample number was 160). There were three main findings. (1) The remote sensing identification results and the reference data was significantly correlated (R²=0.936), and the average absolute error was 5.4%, indicating a high overall accuracy. (2) The identification results in different belt directions were highly correlated with the reference data. The correlation in north-south direction was relatively low, which may be affected by belt shadows. (3) The absolute error of identification results increased first and then decreased with the increases of preservation rate. The absolute error was the smallest in high preservation rate (>80%) and low preservation rate (<20%), and the largest in the middle state, especially in the interval of 50%-60%, because these shelterbelts were more fragmented, with small and numerous gaps. In summary, the preservation rate of farmland shelterbelt can be accurately identified based on high-resolution multispectral satellite images. This method promotes the ability of remote sensing monitoring for shelterbelt structure, which could provide technical support for accurate monitoring the structure and function of farmland shelterbelts.





Spatial variation in functional traits of canopy leaves of major species in broad-leaved Korean pine forests in Changbai Mountain.

KANG Huiwen, SU Baoling, LI Yanan, ZHOU Li, YU Dapao, WANG Qingwei

2024, 43(9):  2667-2676.  doi:10.13292/j.1000-4890.202409.025

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Functional trait difference among species is one of the central issues in species coexistence. However, the effects of intraspecific variation in functional traits on species coexistence and distribution remain unclear. Based on a forest canopy tower crane platform, we explored the variations in leaf morphology, physiological, and biochemical functional traits of ten dominant tree species along the canopy vertical gradient from a broad-leaved Korean pine forest in Changbai Mountain. Leaf thickness, leaf mass per area, flavonoid, effective photochemical quantum yield, and leaf C/N tended to increase with increasing canopy height. Leaf functional traits varied significantly among tree species. Interspecific variations significantly affected morphological and chemical traits. Intraspecific variations contributed more to the variations of physiological traits, which was higher in the upper canopy than in the lower canopy. The interspecific variation was not significant along the vertical gradient. The significant variations of leaf functional traits among vertical canopy gradients demonstrated the importance of the interspecific variations for species coexistence in the broad-leaved Korean pine forest, but the intraspecific variations cannot be ignored.





Functional traits and biomass allocation of summer-germinated plants of Erodium oxyrhinchum.

SHAYAGULI·Jigeer, MAMTIMIN·Sulayman, ZANG Yongxin, YIN Benfeng, LU Yongxing, ZHANG Yuanming

2024, 43(9):  2677-2683.  doi:10.13292/j.1000-4890.202409.020

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Ephemeral plants germinate at different times in desert. They germinate in spring and occasionally in autumn, but very rarely in summer. Changes of precipitation pattern increase the probability of the occurrence of short-lived summer-germinated plants. However, life history strategy of summer-germinated plants remains unclear. Therefore, we measured key traits and the temporal variations of biomass allocation of summer-germinated plants, Erodium oxyrhinchum, in different growth periods and four different slope positions (the base of the sand dune facing west (BW), the middle of the sand dune facing west (MW), the middle of the sand dune facing east (ME), and the base of the sand dune facing east (BE)) in the Gurbantünggüt desert. We further examined the synergetic effects of different slope position and aspect of sand dunes. We found that: (1) The summer-germinated individuals of E. oxyrhinchum crossed the winter and completed life cycle in early spring of next year, with a life cycle of 281.95±3.55 days. (2) There were differences in the root/shoot ratio of the summer-germinated individuals at different growth stages. The ratio showed a significant increase trend before overwintering (P<0.05), and a significant decrease trend after overwintering (P<0.05). (3) There were significant differences in the key traits of summer-germinated individuals in different slope positions and directions of the sand ridge. Plant height, leaf number and biomass per plant on the west slope were significantly greater than those on the east slope, but there was no significant difference in the root/shoot ratio between different slope positions and directions. It is of great significance to explore life history strategy of summer-germinated individuals of E. oxyrhinchum in different slope positions and directions of sand ridges for assessing the vegetation dynamics of desert ecosystems under the background of climate change.





Carbon stock dynamics and carbon sink potential in the upper reaches of Songhua River under different scenarios.

ZHANG Jin, ZHANG Xinyan, ZHANG Wenguang, HUANG Yiqiang, LI Yuhong, FENG Mingming, SUN Zeyu, LI Rui, ZOU Yuanchun, JIANG Ming

2024, 43(9):  2684-2693.  doi:10.13292/j.1000-4890.202409.001

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Carbon stock changes in terrestrial ecosystems are closely related to regional land use changes. It is important to predict carbon sources/sinks under different scenarios for land use management decisions and exploring carbon sink potential. Based on land use data in the upper reaches of Songhua River during 2000-2020, we used the CA-Markov model to predict the spatial pattern of land use under the status quo development scenario, economic development scenario, and ecological protection scenario, respectively. With modified carbon density data, we used the Carbon module of the InVEST model to assess carbon stock and changes in carbon sources and sinks in the upper reaches of the Songhua River for five periods during 2000 to 2050. The overall trend of carbon storage in the upper reaches of Songhua River from 2000 to 2020 was decreasing, with a total decrease of 168.4×10⁸ kg. During the 20year period, the decrease of forest area and the expansion of construction land and arable land were the main reasons for the decrease of carbon stocks. Under the status quo development scenario and the economic development scenario, carbon stocks will decrease greatly in 2030 and 2050. Under the ecological conservation scenario, carbon stocks will increase by 441.5×10⁸ and 658.1×10⁸ kg respectively compared to that in 2020, indicating that the land use pattern under this scenario has a strong carbon sequestration capacity. Our results provide a scientific basis for optimizing land use pattern and the sustainable development of the ecological services of carbon stocks in the upper reaches of Songhua River.





Spatialtemporal variations of coupling relationship between ecosystem services and human well-being in Shangluo City.

LI Chenlu, XIE Wenfang, WANG Qian, YU Fei, HAO Zhanqing, YUAN Zuoqiang

2024, 43(9):  2694-2701.  doi:10.13292/j.1000-4890.202409.022

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The relationship between ecosystem services (ESs) and human well-being (HWB) is a hotspot in the study of human-earth system coupling and sustainable development. Most studies have explored the impact of ESs on HWB based on the cascading framework, but it is difficult to directly reveal the interaction between ESs and HWB. In this study, we analyzed the coupling relationship between ESs and HWB in Shangluo City of Qinling Mountains as the study area. The results showed that the values of ecosystem services showed a fluctuating increase from 2000 to 2020. Shanyang County and Zhen’an County had higher ecosystem services values, while Shangnan County, Luonan County and Zhashui County were the lower-value areas. HWB increased significantly over time, with obvious spatial heterogeneity. The coupling relationship between ESs and HWB had been greatly improved from 2000 to 2020. In the early stage, the coupling between ESs and HWB was severely dysfunctional and accompanied by lagging ecosystem services. With the implementation of a series of environmental protection policies, their coupling was gradually balanced. In the later stage, their relationship showed a coordinated relationship with lagging human well-being. At present, the coupling relationship between ESs and HWB in Shangluo City is rigidly guided by HWB, and ESs play an elastic role in promoting or constraining. Therefore, at this stage, local government should pay attention to planning ecological space and enhancing the development connotation of HWB, so as to promote the strong coupling between ESs and HWB and pursue highquality development.





Assessment of biomass resources for energy use potential in China.

ZHOU Yanming, WANG Jiaoyue, WANG Shiyun, XI Fengming, BING Longfei, YIN Yan, HU Qinqin, ZHANG Lixia

2024, 43(9):  2702-2713.  doi:10.13292/j.1000-4890.202409.029

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Biomass energy is an important renewable energy source, the effective exploitation of which is crucial to achieving China’s carbon peak and carbon neutrality targets. Biomass resources are abundant and diverse in China. However, few studies have conducted the quantitative and comprehensive assessment of biomass resources, leading to the estimates with large uncertainty. How much biomass resources are there in China? What is the potential for biomass energy use? All of these are the focuses of attention. In this study, we constructed a comprehensive biomass energy resource accounting framework. Based on the framework, we analyzed the spatial and temporal variations of biomass resources in China, and used ARIMA model to simulate and predict the future biomass resources and energy exploitation potential. The results showed that the amount of biomass resources and energy utilization potential in China increased from 17.64 and 10.91 EJ in 2001 to 30.59 and 18.08 EJ in 2019, with an average annual growth rate of 3%, respectively. China’s biomass resources mainly originated from agricultural and forest wastes, and manure, accounting for 78.5% of total biomass resources. Biomass resources in the Great Southwest, Middle Yellow River and Middle Yangtze River integrated economic zones were abundant (50.3%). At the province level, Henan, Shandong, Guangxi and Sichuan provinces were rich in biomass resources, accounting for 25.8% of total biomass resources. Along with the increases in population, grain production, livestock development, afforestation area, and urbanization, as well as clean energy construction, the biomass resources and energy development in China would grow correspondingly in the future. The amount of biomass resources and energy exploration potential would increase to 38.17 and 22.46 EJ by 2030, and 66.19 and 38.85 EJ by 2060, respectively. There would be enormous development potential for transforming clean biomass energy products. Our results will be conducive to promoting biomass energy sustainable development, providing data support for the establishment of a clean and low-carbon energy resources census and information platform in China.





Isotope fractionation effect in denitrification process of typical grassland soil.

LIU Deze, WANG Ang, WANG Yingying, YANG Xiusen, SU Chenxia, SONG Linlin, DUAN Yihang, YU Haoming, LIU Dong, ZHAO Pengwu, LI Yinghua, FANG Yunting

2024, 43(9):  2714-2728.  doi:10.13292/j.1000-4890.202409.034

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Denitrification process is the main pathway for gaseous nitrogen loss in ecosystems, but it is difficult to quantify the rate of denitrification. The ¹⁵N natural abundance method is proved to be effective for quantifying denitrification rates at the ecosystem scale. However, this method requires an understanding of the nitrogen and oxygen isotope fractionation factors during denitrification. Currently, studies on the isotope fractionation factors during denitrification mainly focused on forest and cropland soils, and only few studies have been conducted in grassland soils. Here, we determine microbial nitrate consumption rates of four typical grassland soils from different regions in China (Daxinganling, Duolun, Eerguna, and Gangcha) under anaerobic condition. The nitrogen and oxygen isotope effects (ε) and their ratios (Δδ¹⁸O:Δδ¹⁵N) were then fitted using the Rayleigh fractionation model. Our results showed that the ¹⁵ε of grassland soils ranged from 21.6‰ to 32.0‰ (27.1‰±2.1‰), and the ¹⁸ε ranged from 10.4‰ to 15.7‰ (12.9‰±1.1‰). There was a certain difference in ¹⁵ε among different soils, which could be attributed to the differences in physical and chemical properties of different soil types and composition of denitrifying microbial communities. In addition, different calculation methods, initial nitrate concentration, nitrate dissimilatory reduction reaction, and possible nitrification in open environments may also affect the calculation of ¹⁵ε. Mean annual temperature and mean annual precipitation were important factors affecting ¹⁸ε value. The Δδ¹⁸O:Δδ¹⁵N ratios of grassland soils ranged from 0.38 to 0.49 (0.46±0.03), which were lower than previous studies on terrestrial and aquatic ecosystems and microbial pure cultures. The potential reason for the difference in Δδ¹⁸O:Δδ¹⁵N might be the re-oxidation of nitrite and oxygen isotope exchange with water. In conclusion, there were certain differences in fractionation effects among different grassland ecosystems. Thus, variables such as climate and ecosystem type should be comprehensively considered in quantifying denitrification rates.





Effects of long-term straw-derived organic materials returning on soil water dynamics and pore structure

XIAO Junyao, XU Lingjing, WANG Xinyi, SUN Caixia, ZHANG Yulan, JIANG Zhengde

2024, 43(9):  2729-2736.  doi:10.13292/j.1000-4890.202409.010

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In dryland agriculture, soil water-holding capacity is closely associated with soil fertility. Exploring soil water dynamics under the conditions of straw-derived organic materials returning can help reveal the dependency between the core of water retention and soil fertility improvement. Based on a long-term maize field experiment with the treatments of control (CK, without straw), carbonated maize straw incorporation (BC), and crushed maize straw direct incorporation (SD), soil moisture was continuously monitored using soil temperature and humidity recorder. The relationship between soil moisture and soil physicochemical factors was explored. The results showed that the average soil moisture increased by 19.8% (P<0.05) and 9.7% during the whole growth period of maize under the BC and SD treatments, respectively. In May when precipitation occurred after the soil had been dry for several days, soil moisture in the BC increased faster than that in the SD. From July to September, soil moisture increased rapidly following heavy precipitations, and then gradually decreased over time after reaching its peak. In this duration, soil moisture displayed a slower rate of decrease under BC compared to SD. Compared to CK, total soil porosity in BC and SD increased by 18.9% and 7.0%, respectively. Soil water-filled pore space increased by 8.2% in BC and 2.5% in SD, compared to CK. Soil water content in BC was significantly correlated with soil available phosphorus and total phosphorus contents (P<0.05), while soil pore structure in SD was closely linked to alkaline hydrolysis nitrogen content (P<0.05). These findings provide a theoretical basis and guidance for using straw as fertilizer resource.





Effects of ventilation strategies on humification process and microbial community structure of different organic materials.

NIU Mingfen, HU Dandan, WU Tianmu, SHI Ying, SONG Qiaobo, MA Jian

2024, 43(9):  2737-2749.  doi:10.13292/j.1000-4890.202409.040

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To optimize the humification process of compost, we investigated the effects of ventilation volume on microbial respiration intensity using different nitrogen sources including corn straw + urea, corn straw + cow manure, and corn straw + chicken manure in a composting reactor. The results showed that the phased ventilation regulation strategy effectively reduced dry matter loss rate of urea and organic material combination of chicken manure nitrogen source by 12.4% and 16.2%, respectively, while increasing the degree of humus polymerization to 17.9% and 18.1%, respectively, after a composting period of 40 days. The main reason was an increase in HA-FA ratio within the manure compost material. The analysis of the microbial community structure for post-composting treatments revealed that the compost material’s microbial community was influenced by both ventilation and material composition. Compost bodies containing more easily decomposable materials exhibited similar microbial species composition. The phased ventilation regulation strategy had varying effects on the humification of different organic materials, and would be more suitable for regulating the humification process of easily decomposable organic materials.





Effects of sesbania on chlorimuron-ethyl removal and soil microbial community in farmland.

LYU Ze, SU Ao, HU Fangyu, DING Ziming, WANG Baoyu, XU Mingkai, ZHANG Huiwen, AN Jing

2024, 43(9):  2750-2757.  doi:10.13292/j.1000-4890.202409.012

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Chlorimuron-ethyl is widely used in agricultural production activities. Long-term and heavy usage leads to its residues in the soil, posing potential ecological risks to the ecosystem. In a pot experiment, germination rate and plant growth index of sesbania, a green manure plant, was examined. Soil chlorimuron-ethyl content and microbial community structure were analyzed. The tolerance of sesbania to herbicide chlorimuron-ethyl, its remediation effect on chlorimuron-ethyl contaminated soil and influence on soil microbial community were studied. The results showed that sesbania exhibited high tolerance to chlorimuron-ethyl (≤1 mg·L^-1) and significantly reduced the residual amount of chlorimuron-ethyl in the soil. Under the 0.4 mg·kg^-1 chlorimuron-ethyl treatment, sesbania increased the richness and diversity of soil microbial community. However, their richness and diversity in sesbania rhizosphere soil was decreased under 1 mg·kg^-1 chlorimuron-ethyl treatment. Furthermore, sesbania increased the quantity of actinomycetes and acidobacteria in the rhizosphere soil, with the most significant effect being observed in actinomycetes.





Soil trace element accumulation and pollution assessment in typical facility greenhouse in Shandong Province.

ZHANG Jiaqi, SHI Mingyi, LIAN Meihua, ZENG Xiangfeng

2024, 43(9):  2758-2768.  doi:10.13292/j.1000-4890.202409.016

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Underscoring the characteristics of trace element accumulation and their pollution risk in greenhouse soils is an essential prerequisite of risk management in agricultural settings. In this study, we measured the concentrations of total and speciation of iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), cadmium (Cd), lead (Pb), and chromium (Cr) in representative facilities in Shandong. The geo-accumulation index (I_geo), risk assessment code (RAC), and potential ecological risk index (PERI) were used to evaluate the pollution characteristics of soil trace elements. Positive matrix factorization (PMF) and health risk assessment models were combined to identify potential sources of trace elements and calculate their risk levels. Results demonstrated a distinct trend of accumulation of Fe, Mn, Zn, Cu, Cd, and Cr, with the maximum concentration of Cd surpassing the pollution risk thresholds. A significant increase of the bioavailable speciation of Mn, Zn, Cd, and Cr was observed as planting years increased. According to the PMF model, trace elements were primarily affected by agricultural and industrial activities, with contribution rates of 31.49% and 24.07%, respectively. The evaluation based on I_geo, RAC, and PERI indicated that the total concentrations of Cd, Pb, Cu, and Zn, as well as the concentrations of bioavaliable Pb and Zn, exceeded the standard level. Furthermore, the single ecological hazard index (E_i) of Cd was higher, while no risk appeared in terms of comprehensive potential ecological hazard index (RI). The risk probabilities of trace elements in soil were 36.78% for non-carcinogenic and 0.03% for carcinogenic health risks to adults, respectively. Cr emerged as the risk priority control metal.





Variation of soil organic carbon and the influencing factors in croplands of Liaoning Province, China.

CHEN Siyu, LV Ze, ZHANG Yang, WANG Jian, LI Guochen, WANG Chao

2024, 43(9):  2769-2776.  doi:10.13292/j.1000-4890.202409.007

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Northeast China is an important grain production base at the national level. The content of soil organic carbon in this area has been decreasing year by year due to the irrational use. In this study, a total of 444 soil samples were collected from  maize and rice fields (two typical croplands) in Liaoning Province. The contents of soil organic carbon and its components (microbial biomass carbon, necromass carbon, and dissolved organic carbon) as well as their influencing factors were analyzed. The results showed that the contents of soil organic carbon (SOC), microbial biomass carbon (MBC) and MBC/SOC in rice field were higher than those in maize field, while the contents of dissolved organic carbon, bacterial necromass carbon, fungal necromass carbon, and total necromass carbon in rice field were lower than those in maize field. SOC in maize and rice fields had a significant positive correlation with MBC and microbial necromass carbon, while SOC in rice field had a lower slope with MBC and microbial necromass carbon. Results of random forest model analysis showed that soil C/N ratio and fungal necromass carbon were the key factors influencing SOC in maize and rice fields, with higher interpretation for SOC in maize field. There were significant differences in SOC components and key influencing factors between maize and rice fields. Microbial turnover process had stronger influence on SOC in maize field, while soil properties had a dominant influence on SOC content in rice field. This study provides basic data and a theoretical foundation for the scientific regulation of soil organic carbon in the croplands of Northeast China.





Effects of black phosphorus nanosheets on growth traits of soybean under phosphorus deficiency condition.

AN Qile, ZHAO Qing, ZHANG Siyu, ZHANG Xuejiao, LI Haibo

2024, 43(9):  2777-2783.  doi:10.13292/j.1000-4890.202409.002

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Black phosphorus nanosheets (BPNSs) as a potential nano fertilizer would bring new opportunities for agriculture development. We conducted a co-cultivation experiment of BPNSs and soybean to verify the accumulation process of BPNSs and its degradation product phosphate in plants, and to explore the influence of BPNSs on soybean growth traits. The results showed that BPNSs significantly increased phosphorus content of soybean plants, especially in roots. Under phosphorus-deficient Hoagland culture conditions, root phosphorus content of the BPNSs treatment group increased by 45.8%, and the aboveground phosphorus content increased by 8%. Leaf chlorosis and phosphorus-deficient symptoms of soybean was significantly delayed, which facilitated the growth rate of aboveground and belowground parts and help them return to normal. Moreover, the observation results of transmission electron microscopy (TEM) indicated that a large number of BPNSs were enriched in roots, especially in the root pith, which explains why root phosphorus content in the BPNSs treatment was much higher than that of the control group. This study provides basic data for the application of BPNSs in nanotechnology-based agriculture.





Nutritional quality and nutrient utilization properties of silage crops in a semiarid area of western Liaoning Province.

JING Guoyan, WU Chenran, LIANG Zhipeng, WANG Shuqiang, JIANG Dongqi, ZHANG Yulan, CHEN Zhenhua

2024, 43(9):  2784-2791.  doi:10.13292/j.1000-4890.202409.042

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To investigate nutritional quality and nutrient requirements of silage crops in the semiarid area of western Liaoning Province, a field experiment was carried out with three silage crops including silage corn, sweet sorghum, and Sorghum bicolor ×S. sudanense in Fuxin Mongolian Autonomous County, Liaoning Province. Crop yield, nutritional quality, feed value, and plant mineral nutrients were determined. The results showed that: (1) Under the same cultivation management conditions, fresh and dry yields of S. bicolor ×S. sudanense were significantly higher than those of silage corn and sweet sorghum, with the highest dry matter yield reaching 34.22 t·hm^-2. (2) Silage fermentation increased the contents of crude protein and crude fat in silage crops, while reduced that of crude fiber, neutral detergent fiber, acid detergent fiber and lignin. Silage corn demonstrated superior nutritional quality than sweet sorghum and S. bicolor ×S. sudanense. (3) Silage fermentation enhanced the forage value of silage crops, with silage corn showing significantly higher digestible dry matter, dry matter intake, and relative forage value than sweet sorghum and S. bicolor ×S. sudanense. (4) There were no significant differences in nitrogen (N), phosphorus (P), and potassium (K) contents of the three silage crops, with N, P, and K requirements being about 200-300, 60-90 and 320-580 kg·hm^-2, respectively. S. bicolor ×S. sudanense exhibited significantly higher N, P, and K uptake compared to silage corn and sweet sorghum, with a notable demand for K. In conclusion, silage fermentation effectively improved nutritional quality of silage crops, and silage corn would be a more suitable silage crop in western Liaoning Province. Our results provide important support for the high-yield cultivation and promotion of silage crops in western Liaoning.





Characteristics of rhizosphere protest community of citrus Huanglongbing plants and its relationship with soil chemical properties.

ZHANG Tianyu, LIU Qiumei, LI Dejun, YANG Gairen, HE Xunyang

2024, 43(9):  2792-2801.  doi:10.13292/j.1000-4890.202409.013

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Citrus Huanglongbing (HLB) is a significant threat to the healthy and long-term development of citrus industry. Protists are an important member of microbial family and play an important role in maintaining plant health. In this study, we analyzed the diversity and community structure of protists in the rhizosphere soil of healthy and diseased citrus, and explored key soil chemical factors affecting the protist community. Results showed that Ciliophora, Chlorophyta, and Cercosoa were the dominant groups in the rhizosphere soil of the healthy and diseased citrus. The occurrence of Huanglongbing significantly reduced the diversity of protist community and led to a decrease in the contents of total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen, available phosphorus, organic matter, and pH. Results of RDA analysis showed that Protosteliida, Diatomea, Cryptophyla, and Heterolobosea were positively correlated with available phosphorus. Protolveolata was positively correlated with alkali-hydrolyzable nitrogen and pH.  Cercozoa, MAST-12, Apicomplexa, and Schizoplasmodiida showed significant negative correlations with various soil chemical indicators. Candidatus Liberibacter asiatichus was significantly negatively correlated with predatory and phototrophic protists. Overall, the infection of Candidatus Liberibacter asiatichus causes changes in soil chemical properties and significantly altered the diversity and structure of protist community in the rhizosphere. Soil organic matter, total nitrogen, and pH are key factors affecting the structure of protist community. Our results help understand the impacts of Huanglongbing on the structure and diversity of protist community and soil chemical properties, and provide reference for green prevention and control of Huanglongbing in citrus.





Impacts of climate change on climatic suitability of banana planting in Guangdong Province, China.

ZHANG Liuhong, DU Yaodong, DU Jiaming

2024, 43(9):  2802-2812.  doi:10.13292/j.1000-4890.202409.003

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To explore the impacts of climate change on climatic suitability of banana planting in Guangdong Province, we analyzed climate data from 86 meteorological stations in Guangdong Province during 1961 to 2022, including annual mean temperature (T_y), ≥10 ℃ annual accumulated temperature (T_a), average minimum temperature in January (T₁), annual extreme minimum temperature (T_min), and days with daily minimum temperature ≤5 ℃ (D≤5 ℃). The impacts of climate change on climatic suitability of banana planting were assessed by combining with the changes of five key climate factors for the periods of 1961-1990, 1971-2000, 1981-2010, 1991-2020, before (1961-1997) and after (1998-2022) T_y mutation. The results showed that T_y, T_a, T₁, and T_min showed a significant increasing trend with the rates of 0.2 ℃, 80.7 ℃·d, 0.4 ℃ and 0.4 ℃ per decade, respectively. D≤5 ℃ showed significant drop with a rate of 1.5 d per decade. T_y had mutation in the year of 1997. Generally, T_y, T_a, and T_min were higher in south than in north part, in plain than in mountain regions. D≤5 ℃ was lower in southern coastal regions than in northern mountainous regions. Except for the high and cold mountainous regions in northern Guangdong, T₁ in other regions met the heat requirements for bananas to overwinter. According to the climatic requirement of  banana growth and development, the climatic  division for banana planting in Guangdong Province could be divided into four regions: most-suitable region, suitable region, sub-suitable region, and unsuitable region. The most-suitable region was mainly distributed in western Guangdong. The suitable region was mainly located in eastern Guangdong and southern part of the Pearl River Delta. The sub-suitable region was mainly located in northern part of the Pearl River Delta and southern part of northern Guangdong. The unsuitable region was concentrated in northern part of northern Guangdong. Due to climate change, the area of most-suitable region showed obvious northward expansion and eastward movement, but the areas of suitable, sub-suitable, and unsuitable region decreased. Compared to that in 1961-1990, the area of most-suitable region in 1991-2020 increased by 3.45×10⁶ hm², but the areas of suitable, sub-suitable and unsuitable region decreased by 1.83×10⁶, 1.10×10⁶, and 0.52×10⁶ hm², respectively. The percentage of most-suitable region increased by 19.04 percentage point, but the percentages of suitable, sub-suitable and unsuitable region decreased by 8.29, 7.77, and 3.00 percentage point, respectively, after 1997 than that before in Guangdong Province.





Surfactant-enhanced bioremediation of heavy metals and polycyclic aromatic hydrocarbons in soil: A review.

LIAN Meihua, ZENG Xiangfeng, MA Yangyang, WANG Peng, LI Xiaojun

2024, 43(9):  2813-2823.  doi:10.13292/j.1000-4890.202409.030

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A rising number of heavy metals, polycyclic aromatic hydrocarbons, and other inorganic and organic pollutants pose a threat to crop safety and human health due to the rapid development of industry and agriculture. Compared with other technologies, bioremediation is a low-cost and environmentally friendly technology. However, soil is a heterogeneous system comprised of inorganic clay minerals, organic matter, and organic-inorganic colloids that are capable of adsorbing pollutants. The efficiency of bioremediation is therefore limited by the bioavailability of pollutants. By contrast, the surface charge and absorption potential energy of the soil, as well as the speciation and solubility of pollutants may change as a result of surfactant addition. We reviewed the pollution status of heavy metals and polycyclic aromatic hydrocarbons in soils, surfactant types, and the influence of various factors on the efficiency of bioremediation enhanced by surfactants. Furthermore, we summarized and prospectively discussed the disadvantages of bioremediation technique to provide a theoretical basis for future screenings and applications of surfactants.





Development, application and challenges of hybrid life cycle approaches.

LIU Zuoxi, WEI Yingying, LI Yanlong, YU Feifei, WANG Shanshan, XUE Bing

2024, 43(9):  2824-2833.  doi:10.13292/j.1000-4890.202409.038

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Hybrid life cycle assessment (HLCA) is an integration of process-based life cycle assessment (PLCA) and economic input-output life cycle assessment (EIO-LCA). This method expands the system boundary and supplements the environmental impact of the abandonment and use phases, thus solving the limitations caused by using one of these methods alone. Here, we introduce four HLCA methods and their advantages and disadvantages. Firstly, the hierarchical hybrid life cycle assessment method (tiered hybrid LCA, TH LCA) is easy to use, and the results cover a wide range, but with doubling-counting. Secondly, the system boundary of I-O based hybrid LCA (IOH LCA) is improved by input-output list, but lacks of the comparison analysis, because all the products in the same economic department are shown with the same factors. It usually results in inaccuracy issues. Thirdly, path exchange hybrid life cycle assessment method (PXC) replaces some paths with process data, which reduces repeated calculation results, but the calculation process is complex and difficult to use. Fourthly, there are two forms of integrated hybrid LCA (IH LCA), namely four-part matrix and nine-part matrix. The four-part matrix is the earliest proposed integrated hybrid life cycle method. It integrates the input-output table and process data into one matrix, which increases the difficulty of calculation but improves the accuracy of the results. The nine-part matrix retains the four-part matrix and adds the whole regional industrial chain database to analyze the environmental impact of the whole life cycle in different regions and different scenarios. By summarizing the life cycle assessment of TH LCA, IOH LCA, PXC and IH LCA, this review provides reference for the development and application of HLCA method.





Effect and mechanism of Fe-Mn oxides and clay minerals on abiotic natural attenuation of normal alkanes.

ZHANG Yanzi, LIU Changfeng, YAN Xiuxiu, AN Jing

2024, 43(9):  2834-2841.  doi:10.13292/j.1000-4890.202409.028

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Soil constitutions, especially iron oxides, manganese oxides and clay minerals (FeMn-Clay minerals, FM-C), exert a distinguished role in the transformation of organic contaminants. However, the contribution of FM-C to abiotic natural attenuation of normal alkanes in the dark has long been overlooked. In this study, a sterile experiment was conducted to examine the effects of different contents (1%, 2%, 3%) of iron oxides (Fe₃O₄, Fe₂O₃ and FeO(OH)), manganese oxides (MnO₂) and clay minerals (kaolinite and montmorillonite) on the degradation of normal alkanes (long-chain C16-C31). The results showed that 3% FM-C possessed the highest transformation rate for normal alkanes, with a transformation rate up to 52.79% in 63 h. X-ray photoelectron spectroscopy (XPS) characterization suggested that Fe(Ⅱ) had the strongest effect, which was conducive to directly convert O₂ into superoxide radical (O₂^-_·). FM-C had the higher oxygen vacancy concentration, providing sufficient adsorbed oxygen that was stimulative for transformation and degradation of normal alkanes. The O₂^-_· signal before and after the reaction was detected by electron paramagnetic resonance (EPR). The results confirmed that the transformation of normal alkanes was accompanied by O₂^-_·. FTIR characterizations showed that the abiotic natural attenuation of normal alkanes was accompanied by forming new functional groups (C-OH). Consequently, the promoting effects of FM-C on abiotic degradation of normal alkanes and the possible pathways were concluded. Our results provided valuable insights into the abiotic natural attenuation of normal alkanes by inorganic minerals in soils under dark conditions.








Effect of arsenic input on microbial anaerobic fermentation of estuarine sediments.

GAO Mengshan, LI Yongbin, WANG Shaofeng, XI Yimei, ZENG Xiangfeng, JIA Yongfeng

2024, 43(9):  2842-2849.  doi:10.13292/j.1000-4890.202409.035

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The effect of exogenous arsenate (As(Ⅴ)) input on the anaerobic fermentation and community structure in situ in arsenic (As)-contaminated sediments was investigated to elucidate the interaction between As(V) and microbial community composition in the arsenic-contaminated estuarine sediments. The As-contaminated sediments were collected from the Wuli River in Huludao City, Liaoning Province, China. The sediment samples were incubated after adding As(V) (i.e., 1, 10, 60 mg·L^-1, respectively). Physicochemical parameters (e.g., hydrogen production, acid production, pH, and carbon consumption) and microbial community composition were measured during incubation. The dominant strains were isolated from culture solution with high As(V) concentration using plate dilution method. During the enrichment culture, transformation of arsenic form was observed in all treatments. Among them, about 43% of As(V) was converted to arsenite (As(Ⅲ)) in the treatment with 60 mg·L^-1 As(V). At the end of the incubation, the phylum number in the original sediment decreased from eleven to one (Firmicutes), and the dominant genus Clostridium_sensu_stricto_1 occupied the dominant ecological niche. An anaerobic fermentative Clostridium butyricum CXL-1 with the high As(Ⅲ) tolerance (≥200 mg·L^-1) was isolated from the treatment with the addition of 60 mg·L^-1 As(V), which showed the capacity to produce fermentation products such as organic acids and H₂ by glucose fermentation metabolism, thereby providing hydrogen and carbon sources for sulfate-reducing bacteria and methanogens. Our results can provide reference for the anaerobic mineralization remediation of As-contaminated environments by microorganisms.





Application of industrial and agricultural wastes in the treatment of livestock farming wastewater.

SUN Na, LIU Changfeng, SHI Yanan, CHEN Xijuan

2024, 43(9):  2850-2858.  doi:10.13292/j.1000-4890.202409.033

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Industrial and agricultural wastes have a promising application in the removal of pollutants from livestock farming wastewater. In this study, three industrial and agricultural wastes, including magnesium slag, iron slag, and biochar, were selected to mix in a volume ratio of 1∶1∶1. The composite materials were then mixed with surface soil with the volume ratios of 0.75%, 2%, 5% and 10% to conduct soil column transport experiments under steady-state saturation conditions. The results showed that the removal rate of pollutants from swine wastewater was positively correlated with the amount of mixed material, with the highest removal rate in the columns filling with 5%-10% mixed material. The removal rate of total nitrogen (TN) was 29.89% and the cumulative removal amount was 21.95 mg·kg^-1. The removal rate of total phosphorus (TP) was 57.49% and the cumulative removal amount was 15.03 mg·kg^-1. The removal rate of chemical oxygen demand (COD) was 18.08% and the cumulative removal amount was 363.11 mg·kg^-1. The removal rate of biochemical oxygen demand (BOD₅) was 38.52% and the cumulative removal amount was 6.59 mg·kg^-1. The removal rate of turbidity reached 19.22% and the cumulative removal amount was 210.78 NTU. Our results demonstrated that soil mixing with 5%-10% of composite materials can effectively remove more than 20% of pollutants from wastewater. Our results can provide scientific basis for the interception and deterrence strategy of surface pollution mainly from livestock farming wastewater.





Preparation of biochar modified by calcium and humic acid for cadmium pollution remediation.

TAN Hui, WANG Shaofeng, LIAN Meihua, ZENG Xiangfeng, JIA Yongfeng

2024, 43(9):  2859-2870.  doi:10.13292/j.1000-4890.202409.039

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Biochar is a commonly used material for remediation of cadmium contaminated soil, but its efficiency is not high. To improve the adsorption capacity of biochar for Cd²⁺, rice straw biochar was modified by loading Ca²⁺ and activating modification by humic acid oxidation impregnation. The materials were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Batch adsorption experiments and pot experiments were carried out to explore the adsorption fixation properties and mechanism of the materials for Cd²⁺. The results showed that: (1) The best adsorption performance was observed when the mass ratio of biochar to humic acid was 1∶1 and the concentration of Ca²⁺ was 1.5 g·L^-1 (referred to as RHB1-1), and the maximum adsorption capacity was 74.46 mg·g^-1, which was 61% higher than that of original biochar. (2) The content of acidic oxygen-containing functional groups on the surface of calcium-humic acid modified biochar was significantly increased, and the free hydroxyl group was newly formed. Cd²⁺ was efficiently adsorbed by coordination chelation and complexation co-ion exchange. The adsorption of Cd²⁺ by calcium-humic acid modified biochar was mainly chemisorption, which was consistent with Freundlich adsorption isotherm model. (3) The materials can absorb Cd²⁺ in soil and promote the transformation of Cd²⁺ from an acid extractable state to a residual state, reducing the bioavailability of Cd²⁺ in soil.





Effects of nutrient solution of activated iron tailing silicon-selenium nanoparticles on the growth of rice seedlings.

ZHAO Xiang, ZHANG Xiaorong, GONG Zongqiang, SU Dan, JIA Yanjie, LUO Chunfeng, LIU Fengfei

2024, 43(9):  2871-2880.  doi:10.13292/j.1000-4890.202409.041

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The objectives of this study were to prepare a nutrient solution with iron tailing silicon-selenium nanoparticles and to provide theoretical basis for enhancing rice growth and selenium assimilation. A two-factorial experiment was conducted using rice cultivar Daohuaxiang No. 2, with four levels of silicon (0, 300, 600, 900 g·hm^-2) and four levels of selenium nanoparticles (0, 18.75, 37.5, 56.25 g·hm^-2). Additionally, a control group using sodium selenite (37.5 g·hm^-2) and silicon (600 g·hm^-2) was included. This experiment was established to examine the impacts of silicon and selenium nanoparticle concentrations in the nutrient solution on the growth and selenium accumulation in rice seedlings, determine the optimal silicon-selenium ratio, and elucidate the role of silicon in selenium enrichment and its underlying physiological mechanisms. Results showed that the concurrent application of silicon and selenium synergistically enhanced rice growth compared to treatments with only selenium or silicon. Silicon addition facilitated the growth of rice seedlings by increasing the activities of superoxide dismutase (SOD) and catalase (CAT). The nutrient solution containing 600 g·hm^-2 of silicon and 37.5 g·hm^-2 of selenium nanoparticles markedly outperformed other treatment groups, increasing plant height and root-to-shoot ratio of rice seedlings by 9.9% and 5.3%, respectively; and the selenium content in roots, stems and leaves increased by 41.4%, 32.4% and 42.3% respectively, compared to the sodium selenite-treated group.





Effects of different metallurgical solid waste materials on the stabilization of heavy metals in soils.

BAI Xuqin, JIA Chunyun, LIU Changfeng, HAN Xiuyun, DING Yue, WANG Shiwei

2024, 43(9):  2881-2891.  doi:10.13292/j.1000-4890.202409.014

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Alkaline industrial wastes have been widely used for soil heavy metal remediation. They can be combined, processed and modified to stabilize heavy metals in the soil, thereby reducing the toxicity of heavy metals. In this study, we investigated the stabilization effect of blast furnace slag (FG) and iron tailing sand (T) on heavy metal-contaminated soil, and combined SEM-EDS and XRD to reveal the passivation mechanism of heavy metals in soil. The products WFG and HFG were obtained after washing and high-temperature calcination of blast furnace slag materials, while the product HT was obtained after high-temperature calcination of iron tailing sand. The results showed that the application of stabilizing materials significantly increased soil pH, and did not affect EC value. Soil pH declined after soil was stabilized for 40 d. The contents of Cd, Pb and Zn in DTPA extracted soil decreased after 40 d of treatment with stabilizing materials, and the HFG-10% treatment had the best effect on Cd and Zn, with stabilizing rates of 66.04% and 92.21%, respectively. HT-10% had the best stabilizing effect on Pb, with a stabilizing rate of 69.67%. The application of stabilization materials first increased and then decreased the content of heavy metals in the soil in the residual and reducible states over time. The assessment of ecological risk index showed that the risk index of Cd, Pb and Zn in the soil decreased by one level after application of 10% blast furnace slag materials (FG, WFG and HFG). Overall, the HFG-10% treatment had the best stabilization effect on Cd, Pb and Zn in soil, and the heavy metal passivation mechanisms mainly included surface adsorption and complexation reactions.





Effects of Spartina alterniflora eradication project on macrobenthos community structure: A case study of Nanhui tidal flat in Shanghai.

GONG Lv, HU Yang, LI Ben, SONG Yuanhao, LI Zeyuan, LI Tianyou, LI Xiuzhen

2024, 43(9):  2892-2900.  doi:10.13292/j.1000-4890.202409.006

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Spartina alterniflora is a typical invasive species in the coastal zone of China. The removal of S. alterniflora has become a major national ecological restoration mission. The combination of mowing and ploughing is one of the main methods of S. alterniflora eradication. To evaluate the effect of this method on the macrobenthos in coastal salt marsh, we investigated the macrobenthos and sediment physicochemical indices of 12 sampling sites in September to December of 2021-2022, before and after the physical control of S. alterniflora in the ecological restoration project of Nanhui tidal flat. The results showed that 22 species of macrobenthos belonging to 3 phyla, 5 classes, 12 orders, and 19 families were identified during the two years. After the project, species number, density, biomass, Shannon diversity index and Chao1 index of macrobenthos significantly increased. In terms of macrobenthos community, the proportions of Polychaeta, Bivalvia and Malacostraca all increased, but the proportions of Gastropoda and Insecta showed a decreasing trend. The results of non-metric multidimensional scaling (NMDS) and analysis of similarities (Anosim) indicated that community structure of macrobenthos was significantly different before and after the project, and that dominant species changed from Assiminea latericea, Cerithideopsis largillierti and Notomastus latericeus to Assiminea sp., Assiminea latericea, Notomastus latericeus, Glauconome chinensis and Cerithideopsis largillierti. The results of redundancy analysis (RDA) indicated that physicochemical factors such as sediment salinity, water moisture changed after the project, which affected the community structure of macrobenthos.





Production of rhamnolipids by open fermentation of Pseudomonas aeruginosa SQ6.

MA Xin, ZHANG Yang, XIU Jianlong, BAI Xue, HAN Siqin, LIANG Xiaolong, ZHANG Ying

2024, 43(9):  2901-2907.  doi:10.13292/j.1000-4890.202409.037

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To reduce the cost of fermentation and improve the efficiency of microbial oil recovery, we carried out an open fermentation exploration of oil-producing functional bacterium SQ6 (rhamnolipids-producing strain). We investigated the growth at different temperatures, rhamnolipid production, surface tension, emulsification index and other parameters of strain SQ6 under two fermentation modes, i.e., conventional fermentation and open fermentation. The homologous composition of rhamnolipid products was analyzed by liquid chromatography-high resolution mass spectrometry, and the bacterial community structure and percentage of microbial contaminants of open fermentation were analyzed by highthroughput sequencing. The results showed that the highest growth of strain SQ6 was at 45 ℃, and the highest temperature for synthesizing a large amount of rhamnolipids was 40 ℃. The fermentation temperature with the highest yield and lowest miscellaneous bacteria rate in open fermentation was 37 ℃, the yield of rhamnolipids reached 7050.1 mg·L^-1, which was only 33% lower than that of conventional fermentation (10513.2 mg·L^-1), and miscellaneous bacteria rate was the lowest reaching 3.13%. For the SQ6 strain, high-temperature fermentation did not have a stronger inhibitory effect on microbial contaminants and reduced the production of rhamnolipids. The structure of fermentation product showed that the main product was mono-rhamnolipids, accounting for 96.1%. The synthesis of mono-rhamnolipids in high concentration may be the main reason for the stronger inhibition rate of bacterial contaminants in open fermentation under medium temperature. Therefore, strain SQ6 is a functional oil recovery bacterium with substantial open fermentation potential.





Effects of necromass on the transport behavior of bacteria mediated by heptotaxis.

LU En, CHEN Xijuan, SHI Yanan, YANG Xinyao, YANG Liqiong

2024, 43(9):  2908-2916.  doi:10.13292/j.1000-4890.202409.009

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Bacteria can move along pollutant concentration gradients under both liquid and solid phases, facilitating the degradation of contaminants. Migration toward concentrated contaminants along immobilized solid surface is called heptotaxis, which plays a crucial role in the bioremediation of contaminated soils. Soil colloids can influence heptotaxis by affecting the solid-liquid distribution of organic contaminants. In this study, we investigated the effect of soil colloids on bacterial transport mediated by heptotaxis with Pseudomonas fluorescens 5RL (Pf_5RL), a bacterium chemically responsive to naphthalene and its necromass as model bacteria and soil colloids. The results showed that the necromass remained stable in quartz sand, and that neither Pf_5RL nor naphthalene affected its transport behavior, with a maximum breakthrough relative concentration (max C/C₀) of ~0.6. However, the presence of necromass could hinder the transport of Pf_5RL, decreasing the max C/C₀ from 0.97±0.02 to 0.75±0.01. This is primarily attributed to the increased electrostatic attraction which enhanced the attachment of Pf_5RL on the necromass. The presence of naphthalene impeded Pf_5RL transport due to the adsorption of naphthalene on sand, resulting in near-surface chemotaxis and heptotaxis effects, accompanied by a declining max C/C₀ of Pf_5RL from 0.97±0.02 to 0.75±0.04. Under the presence of naphthalene, the necromass further hindered Pf_5RL transport by increasing the adsorption sites for naphthalene, which strengthened near-surface chemotaxis and heptotaxis effects, leading to a further decrease in max C/C₀ of Pf_5RL from 0.75±0.04 to 0.50±0.03. Our results highlight the significant role of necromass in the heptotaxis and chemotactic effects mediated by organic contaminants. It is suggested that necromass may be a crucial factor influencing the in-situ degradation of organic contaminants brought into soils by application of animal manure and reclaimed water.





The effect of amoxicillin on the growth and  metabolism of Firmicutes.

CHEN Wenyue, LI Weiming, LI Botao, LIAN Meihua, LI Lixia, WANG Shaofeng, ZENG Xiangfeng, JIA Yongfeng

2024, 43(9):  2917-2922.  doi:10.13292/j.1000-4890.202409.017

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Antibiotic contamination has a serious impact on microbial ecology. Fermentation is an important biological process under anaerobic conditions, but its response to antibiotic contamination remains unclear. In this study, we investigated the effects of different concentrations of antibiotics on the fermentation metabolism of Clostridium butyricum and Bacillus coagulans, two spore-producing microorganisms of the thick-walled phylum Clostridium perfringens, using the typical β-lactam antibiotic amoxicillin as an example. We measured the changes of the growth curves, carbon source consumption, organic acid production, and pH of both strains of bacteria during the fermentation process. The results showed that amoxicillin inhibited the growth and carbon source consumption of both C. butyricum and B. coagulans, with less effect on bacterial morphology. 50 mg·L^-1 amoxicillin caused the growth of C. butyricum to stop, whereas B. coagulans could continue to grow after 24 h of incubation. In terms of organic acid metabolism, the effect of amoxicillin on B. coagulans was more significant. Butyric, formic, lactic and acetic acid production of both strains was inhibited, but lactic acid production in B. coagulans was significantly increased under the addition of low concentration (1 mg·L^-1) of amoxicillin.