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    18 February 2024, Volume 35 Issue 2
    Effects of community structure of Cunninghamia lanceolata sprouting forests with different densities on ecosystem carbon density at the early stage of succession
    ZHANG Yulin, LIU Lingjuan, LIU Shenglong, FANG Wanli, LUO Zhensha, HONG Xuansheng, CHENG Xiangrong
    2024, 35(2):  289-297.  doi:10.13287/j.1001-9332.202402.014
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    To explore potential responses of ecosystem carbon density to changes of community structure during natural regeneration of woody plants, we analyzed the relationships between ecosystem carbon density and its components, tree species diversity, structural diversity (CVDBH) and spatial structure parameters (mingling, aggregation, dominance, crowding) of Cunninghamia lanceolata forests with different sprouting densities (1154, 847 and 465 individuals·hm-2) at the early stage of succession in Baishanzu National Park. The results showed that tree species diversity (species richness index and Shannon diversity index) increased with the decrease of sprouting density of C. lanceolata. Among the stand structural parameters, CVDBH, stand density, and mingling increased with the decrease of sprouting density of C. lanceolata. The stand distribution pattern of different C. lanceolata densities was uniform, with sub-dominant stand growth status and relatively dense status. The carbon density of tree layer under high, medium, and low sprouting densities of C. lanceolata were 57.56, 56.12 and 46.54 t·hm-2, soil carbon density were 104.35, 122.71 and 142.00 t·hm-2, and the total carbon density of ecosystem were 164.59, 182.41 and 190.13 t·hm-2, respectively. There was little variation in carbon density of understory layer and litter layer among different treatments. The carbon density distribution characteristics of different C. lanceolata densities were following the order of soil layer (63.4%-74.7%) > tree layer (24.5%-35.0%) > understory layer and litter layer (0.8%-2.0%). The results of variance partitioning analysis indicated that the change of tree layer carbon density was mainly influenced by stand structure diversity, soil layer carbon density was influenced by both tree species diversity and stand structure diversity, while ecosystem carbon density was mainly influenced by tree species diversity. Stand spatial structure parameters had a relatively little effect on ecosystem carbon density and its components. The sprouting density of C. lanceolata significantly affected ecosystem carbon accumulation during the conversion from C. lanceolata plantations to natural forests. A lower remaining density of C. lanceolata (about 500 individuals·hm-2) was more conducive to forest carbon sequestration.
    Effects of topography and stand spatial structure on the diameter at breast height growth of major pioneer tree species of natural broad-leaved mixed forests in Zhejiang Province, China
    WANG Jianwu, XU Sen, JI Biyong, DU Qun
    2024, 35(2):  298-306.  doi:10.13287/j.1001-9332.202402.036
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    Based on the continuous inventory data of forest resources in Zhejiang Province in 2019 and 2021, we used statistical methods such as polynomial regression to analyze the impacts of topography and forest spatial structure on average annual diameter at breast height (DBH) growth of main pioneer tree species in natural broad-leaved mixed forests. The results showed that DBH of Schima superba, Quercus glauca, Quercus fabri, Lithocarpus glaber, Castanopsis eyrei, and Castanopsis sclerophylla were between 5-50.8, 5-41.5, 5-50.8, 5-43.9, 5-55.5, and 5-46.1 cm, respectively. We classified all the trees into three classes based on DBH: small (6-12 cm), medium (12-14 cm), and large (>26 cm). The average annual DBH growth of S. superba and Q. glauca was the highest on semi-shady slope and shady slope, with increases of 2.9%-15.7% and 1.1%-41.2%, respectively. The average annual DBH growth of large-diameter S. superba, L. glaber, C. eyrei and C. sclerophylla decreased with the increase of slope, with a maximum decrease of 27.0% for S. superba, with no significant difference among small- and medium-diameter trees as a whole. The slope position did not affect the annual DBH growth of small-diameter trees, while that of medium- and large-diameter S. superba, Q. glauca, and large-diameter Q. fabri, L. glaber decreased with the change of slope position from downhill, mesoslope, uphill to ridge, with a maximum decrease of 28.1% for L. glabe, and the major-diameter C. eyrei was on the contrary. Appropriate increase in the mingling was beneficial to the average annual DBH growth of medium- and large-diameter trees. Moderate mixing was suitable for S. superba, while low degree mixing and moderate mixing was suitable for Q. glauca, Q. fabri and L. glaber, and intensive mixing was suitable for C. eyrei and C. sclerophylla. No significant difference was observed for minor-diameter trees under the mingling. The neighborhood comparison only had a significant effect on the average annual DBH growth of large-diameter Q. glauca, Q. fabri, and L. glaber, which was significantly higher under subdominance-moderation than moderation-inferiority. The average annual DBH growth in the study area was mainly affected by aspect and mixing degree.
    Height-diameter model of broad-leaved mixed forest based on species classification in Maoershan, Northeast China
    CAO Xiaomei, MIAO Zheng, HAO Yuanshuo, DONG Lihu
    2024, 35(2):  307-320.  doi:10.13287/j.1001-9332.202402.016
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    The complex stand structure and high species diversity of natural forests pose great challenges for analyzing stand growth and formulating reasonable plans for forest management. The height-diameter relationship is of great significance for predicting stand growth and formulating forest management measures. Based on survey data of 48 broad-leaved mixed forest plots in Maoershan, we classified 23 tree species into four groups based on species structure, growth characteristics and bionomics. We established a generalized model including stand, tree competition, species mixing and species diversity variables by reparameterization method, and a two-level mixed effect model of plot and tree species group. We tested the prediction ability of the model by leave-one-out cross-validation method. The results showed that the Ratkowsky (1990) model was the optimal basic model. The introduction of dominant height, basal area of trees larger than the object tree, basal area proportion of each species, and Shannon index could better explain the height-diameter relationship of broad-leaved mixed forest in Maoershan. The introduction of the mixed effect model of plot and tree species group could significantly improve the prediction accuracy of the model, with a Ra2 of 0.83. Under the same gradient of environmental factors, intolerant tree species exhibited higher tree heights than shade-tolerant tree species. In this study, we used the constructed tree height-diameter model to analyze the effects of species mixing and tree functional traits on tree height, which provided a theoretical basis for accurately predicting height of different tree species and analyzing the growth relationships in broadleaved mixed forests.
    Tree parameter extraction in Fokienia hodginsii plantation based on airborne LiDAR data
    JIANG Ze, CHEN Jie, TANG Liyu, YU Can, XIE Rugen, HUANG Danling, SU Shunde
    2024, 35(2):  321-329.  doi:10.13287/j.1001-9332.202402.015
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    Accurate and efficient extraction of tree parameters from plantations lay foundation for estimating individual wood volume and stand stocking. In this study, we proposed a method of extracting high-precision tree parameters based on airborne LiDAR data. The main process included data pre-processing, ground filtering, individual tree segmentation, and parameter extraction. We collected high-density airborne point cloud data from the large-diameter timber of Fokienia hodginsii plantation in Guanzhuang State Forestry Farm, Shaxian County, Fujian Province, and pre-processed the point cloud data by denoising, resampling and normalization. The vegetation point clouds and ground point clouds were separated by the Cloth Simulation Filter (CSF). The former data were interpolated using the Delaunay triangulation mesh method to generate a digital surface model (DSM), while the latter data were interpolated using the Inverse Distance Weighted to generate a digital elevation model (DEM). After that, we obtained the canopy height model (CHM) through the difference operation between the two, and analyzed the CHM with varying resolutions by the watershed algorithm on the accuracy of individual tree segmentation and parameter extraction. We used the point cloud distance clustering algorithm to segment the normalized vegetation point cloud into individual trees, and analyzed the effects of different distance thresholds on the accuracy of indivi-dual tree segmentation and parameter extraction. The results showed that the watershed algorithm for extracting tree height of 0.3 m resolution CHM had highest comprehensive evaluation index of 91.1% for individual tree segmentation and superior accuracy with R2 of 0.967 and RMSE of 0.890 m. When the spacing threshold of the point cloud segmentation algorithm was the average crown diameter, the highest comprehensive evaluation index of 91.3% for individual tree segmentation, the extraction accuracy of the crown diameter was superior, with R2 of 0.937 and RMSE of 0.418 m. Tree height, crown diameter, tree density, and spatial distribution of trees were estimated. There were 5994 F. hodginsii, with an average tree height of 16.63 m and crown diameter of 3.98 m. Trees with height of 15-20 m were the most numerous (a total of 2661), followed by those between 10-15 m. This method of forest parameter extraction was useful for monitoring and managing plantations.
    Effects of forest regeneration types on phosphorus fractions of soil aggregates in subtropical forest
    XIE Jingjin, XU Qiuyue, HE Min, XIA Yun, FAN Yuexin, YANG Liuming
    2024, 35(2):  330-338.  doi:10.13287/j.1001-9332.202402.010
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    Soil aggregates are important for the storage and availability of phosphorus in the soil. However, how forest regeneration types affect phosphorus fractions of soil aggregates remains unclear. In this study, we examined the composition of aggregate particle size, phosphorus fractions, phosphorus sorption capacity index (PSOR), legacy phosphorus index (PLGC) and degree of phosphorus saturation by Mehlich 3 (DPSM3) in bulk soils and soil aggregates of Castanopsis carlesii secondary forest (slight disturbance), C. carlesii human-assisted regeneration forest (moderate disturbance), and Cunninghamia lanceolata plantation (severe disturbance), aiming to explore the impact of forest regeneration types on phosphorus availability and supply potential of bulk soils and soil aggregates. The results showed that forest regeneration types significantly influenced the composition of soil aggregates. The proportion of coarse macroaggregates (>2 mm) in the soil of C. carlesii secondary forest and human-assisted regeneration forest was significantly higher than that in the C. lanceolata plantation, while the proportion of silt and clay fraction (<0.053 mm) showed an opposite trend. The composition of soil aggregates significantly affected the contents of different phosphorus fractions. The contents of soil labile phosphorus fractions (PSOL and PM3) decreased as aggregate particle size decreased. The contents of soil total phosphorus (TP), total organic phosphorus (Po), mode-rately labile phosphorus fractions (PiOH and PoOH), and occluded phosphorus (POCL), as well as PSOR and PLGC, exhibited a trend of decreasing at the beginning and then increasing as particle size decreased. The contents of TP, Po, and PiOH in coarse and silt macroaggregates was significantly higher than that in fine macroaggregates (0.25-2 mm) and microaggregates (0.053-0.25 mm). Forest regeneration types significantly influenced the contents of phosphorus fractions of bulk soils and soil aggregates. The contents of TP, Po, PSOL, and PM3 in the soil of C. carlesii secondary forests was significantly higher than that in C. carlesii human-assisted regeneration forest and C. lanceolata plantation. The contents of PSOL and PM3 in different-sized aggregates of C. carlesii secondary forests were significantly higher than that in the C. lanceolata plantation. Forest regeneration types significantly influenced the composition and supply potential of phosphorus fractions in soil aggregates. The proportions of PSOL, and PM3 to TP in different-sized soil aggregates were significantly lower in C. carlesii human-assisted regeneration forest compared with C. carlesii secondary forest. PSOR and DPSM3 in different-sized soil aggregates were significantly lower in C. lanceolata plantation than that in C. carlesii secondary forest. Overall, our results indicated that natural regeneration is more favorable for maintaining soil phosphorus availability, and that forest regeneration affects soil phosphorus availa-bility and its supply potential by altering the composition of soil aggregates.
    Effects of stand ages on soil enzyme activities in Chinese fir plantations and natural secondary forests
    LI Jiayu, SHI Xiuzhen, LI Shuaijun, WANG Zhenyu, WANG Jianqing, ZOU Bingzhang, WANG Sirong, HUANG Zhiqun
    2024, 35(2):  339-346.  doi:10.13287/j.1001-9332.202402.008
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    Forest type and stand age are important biological factors affecting soil enzyme activities. However, the changes in soil enzyme activities across stand ages and underlying mechanisms under the two forest restoration strate-gies of plantations and natural secondary forests remain elusive. In this study, we investigated the variations of four soil enzyme activities including cello-biohydrolase (CBH), β-1,4-glucosidase (βG), acid phosphatase (AP) and β-1,4-N-acetylglucosaminidase (NAG), which were closely associated with soil carbon, nitrogen, and phosphorus cycling, across Cunninghamia lanceolata plantations and natural secondary forests (5, 8, 21, 27 and 40 years old). The results showed that soil enzyme activities showed different patterns across different forest types. The acti-vities of AP, βG and CBH in the C. lanceolata plantations were significantly higher than those in the natural secon-dary forests, and there was no significant difference in the NAG activity. In the plantations, AP activity showed a decreasing tendency with the increasing stand ages, with the AP activity in the 5-year-old plantations significantly higher than other stand ages by more than 62.3%. The activities of NAG and CBH decreased first and then increased, and βG enzyme activity fluctuated with the increasing stand age. In the natural secondary forests, NAG enzyme activity fluctuated with the increasing stand age, with that in the 8-year-old and 27-year-old stand ages being significantly higher than the other stand ages by more than 14.9%. βG and CBH enzyme activities increased first and then decreased, and no significant difference was observed in the AP activity. Results of the stepwise regression analyses showed that soil predictors explained more than 34% of the variation in the best-fitting models predicting soil enzyme activities in the C. lanceolata plantations and natural secondary forests. In conclusion, there would be a risk of soil fertility degradation C. lanceolata plantations with the increasing stand age, while natural secondary forests were more conducive to maintaining soil fertility.
    Relationship between negative air ion and PM2.5 in Quercus variabilis under natural conditions
    CAI Lulu, SUN Shoujia, SHI Guangyao, DU Lingtong, NI Xilu, ZHANG Jinsong, MENG Ping
    2024, 35(2):  347-353.  doi:10.13287/j.1001-9332.202402.032
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    In recent years, PM2.5 pollution has become a most important source of air pollution. Prolonged exposure to high PM2.5 concentrations can give rise to severe health issues. Negative air ion (NAI) is an important indicator for measuring air quality, which is collectively known as the ‘air vitamin’. However, the intricate and fluctuating meteorological conditions and vegetation types result in numerous uncertainties in the correlation between PM2.5 and NAI. In this study, we collected data on NAI, PM2.5, and meteorological elements through positioning observation during the period of June to September in 2019 and 2020 under the condition of relatively constant leaf area in Quercus variabilis forest, a typical forest in warm temperate zones. We investigated the spatiotemporal variation of PM2.5 and NAI under consistent meteorological conditions, established the correlation between PM2.5 and NAI, and explicated the impact mechanism of PM2.5 on NAI in natural conditions. The results showed that NAI decreased exponentially with the increases in natural PM2.5, with a significant negative correlation (y=1148.79x-0.123). The decrease rates of NAI in PM2.5 concentrations of 0-20, 20-40, 40-80, 80-100 and 100-120 μg·m-3 were 40.1%, 36.2%, 9.4%, 2.4%, 5.1% and 6.8%, respectively. Results of the sensitivity analysis showed that the PM2.5 concentration range of 0-40 μg·m-3 was the sensitive range that affected NAI. Our findings could provide a scientific basis for better understanding the response mechanisms of NAI to environmental factors.
    Forest fire risk zoning based on fuzzy logic and analytical network process
    OUYANG Yiyun, SU Zhangwen, LI Chunhui, ZENG Aicong, GUO Futao
    2024, 35(2):  354-362.  doi:10.13287/j.1001-9332.202402.024
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    Forest fires have a significant impact on human life, property safety, and ecological environment. Deve-loping high-quality forest fire risk maps is beneficial for preventing forest fires, guiding resource allocation for firefighting, assisting in fire suppression efforts, and supporting decision-making. With a multi-criteria decision analysis (MCDA) method based on geographic information systems (GIS) and literature review, we assessed the main factors influencing the occurrences of forest fires in Youxi County, Fujian Province. We analyzed the importance of each fire risk factor using the analytic network process (ANP) and assigned weights, and evaluated the sub-standard weights using fuzzy logic assessment. Using ArcGIS aggregation functions, we generated a forest fire risk map and validated it with satellite fire points. The results showed that the areas classified as level 4 or higher fire risk accounted for a considerable proportion in Youxi County, and that the central and northern regions were at higher risk. The overall fire risk situation in the county was severe. The fuzzy ANP model demonstrated a high accuracy of 85.8%. The introduction of this novel MCDA method could effectively improve the accuracy of forest fire risk mapping at a small scale, providing a basis for early fire warning and the planning and allocation of firefighting resources.
    Analysis and evaluation of the burning characteristics of six commonly used herbaceous species in Beijing
    YAN Jing, SONG Linshu, LI Bingling, LIU Yan
    2024, 35(2):  363-370.  doi:10.13287/j.1001-9332.202402.007
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    Surface vegetations are one of the key factors affecting the spread of green space fires. To explore the combustibility of commonly used local surface layer herbaceous species in Beijing, and to provide a reference for the construction and management of urban green space, we comprehensively evaluated the combustibility of Carex giraldiana, Carex breviculis, Liriope spicata, Iris lactea, Iris tectorum, and Buffaloe dactyloides, with the entropy weight method and K-mean cluster analysis based on the principal component analysis method. We measured the combustion characteristics indicators (blade ignition point, combustion time and heat release rate), physical and chemical indicators (leaf moisture content and crude fat content), and biological characteristics indicators (blade thickness and unit load) during the key period of fire prevention. The results showed that blade thickness and ignition point got the highest weight and affected the overall combustibility most. Peak heat release rate and ignition time had the lowest weight and minimal impact on the overall combustibility. The combustibility of the six species followed an order of B. dactyloides > C. breviculmis > L. spicata > C. giraldiana > I. lactea > I. tectorum. Results of the clustering analysis showed that the combustion ability of B. dactyloides, C. breviculmis, and L. spicata were in class Ⅰ, with the strongest combustion ability; C. giraldiana was in class Ⅱ; I. lactea and I. tectorum were in class Ⅲ, with the lowest flammability. As widely used surface vegetations, critical attention should be paid on B. dactyloides, C. breviculmis and L. spicata for fire prevention in winter and spring.
    Spatial distribution pattern and correlation of dominant populations in the shrub layer of Fengshui forest in Leizhou Peninsula, China
    CHEN Cai, TANG Guangda, DONG Xiaoquan, XU Songjun
    2024, 35(2):  371-380.  doi:10.13287/j.1001-9332.202402.006
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    To elucidate the spatial patterns of understory species in fragmented forests adjacent to human settlements, we examined the spatial distribution and intraspecific correlations of three dominant species Mallotus philippensis, Dasymashalon trichophorum, and Psychotria rubra by employing point pattern analysis, which were the top three in terms of importance value in the shrub layer of Fengshui forest in Leizhou Peninsula, Guangdong. The results showed that all the three species were mainly aggregated at the scale of 0-25 m, especially for young trees. The degree of aggregation gradually diminished with increasing age class. The spatial distribution patterns of three species were predominantly influenced by habitat heterogeneity, negative density dependence, and dispersal limitation. They showed positive association among different age classes, especially between young trees and middle age trees and between young trees and adult trees. Therefore, in the ecological restoration process of Leizhou Peninsula, M. philippensis, D. trichophorum, and P. rubra should be planted in clusters at a small scale within the range of 0-25 m, with the degree of clusters depending on plant morphology. For larger scales, a dispersed cultivation approach was advocated.
    Distribution pattern and influencing factors of bacterial communities in different soil depths of Caragana jubata shurb in Luya Mountain, China
    LIANG Xueli, LIANG Xiaoxia, MAO Xiaoya, CHAI Baofeng, JIA Tong
    2024, 35(2):  381-389.  doi:10.13287/j.1001-9332.202402.003
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    Soil microorganisms are important components of terrestrial ecosystems, affecting soil formation and fertility, plant growth and stress tolerance, nutrient turnover and carbon storage. In this study, we collected soil samples (humus layer, 0-10 cm, 10-20 cm, 20-40 cm, and 40-80 cm) from Caragana jubata shrubland in Shanxi subalpine to explore the composition, diversity, and assembly of soil bacterial communities at different depths across the soil profile. The results showed that Actinomycota (19%-28%), Chloromycota (10%-36%) and Acidobacteria (15%-24%), and Proteobacteria (9%-25%) were the dominant bacterial phyla. α-diversity of soil bacterial community significantly decreased with the increases of soil depth. Soil bacterial β-diversity varied across different soil depths. Soil pH, water content, and enzyme activity were the main ecological factors affecting the distribution of soil bacterial communities. Soil bacterial communities had more complex interactions in humus layer and 0-10 cm layer. On the whole, soil bacterial communities were dominated by coexistence in C. jubata shrubland, and the soil bacterial community assembly was driven by random process.
    Effect of short-term nitrogen deposition on dry-wet seasonal variation of soil respiration in degraded Poa pratensis alpine meadow of the Napahai, Yunnan, China
    SUN Guanfa, LU Mei, SHAN Shengyang, ZHAO Dingrong, SUN Yujia, LIU Guoqing, ZHAO Xuyan, FENG Jun
    2024, 35(2):  390-398.  doi:10.13287/j.1001-9332.202402.005
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    To explore the coupling of dry-wet seasonal variations of soil respiration with their environmental factors in the alpine meadow under the background of increasing nitrogen (N) deposition, we conducted an experiment in the typical degraded Poa pratensis meadow in the Napahai, Yunnan. There were four treatments, i.e., control (0 g·m-2·a-1), low (5 g·m-2·a-1), medium (10 g·m-2·a-1), and high (15 g·m-2·a-1) levels. We examined the effects of aboveground biomass, plant diversity, and soil physicochemical properties on soil respiration. The results showed that N deposition significantly promoted soil respiration. Compared with that in the control, soil respiration rates increased by 21.9%-53.9% and 27.3%-51.2% in dry and wet seasons, respectively. The maximum value of soil respiration rate was recorded in the medium N treatment. N deposition dramatically elevated aboveground biomass (52.2%-66.4%). Plant diversity declined with increasing N addition levels, with the maximum value (13.5%-24.2%) being recorded in high treatment in wet season. The values of ammonium nitrogen, organic matter, microbial biomass carbon and nitrogen, temperature and moisture in the three N treatments were elevated by 14.3%-333.5% compared with the control, while those of soil pH were decreased by 9.0%-34.6%. Results of the structural equation modelling showed that plant biomass, Shannon diversity, microbial biomass, soil temperature, and moisture showed a positive effect on soil respiration, while bulk density had a negative effect. Soil nitrogen pool and pH were main factors driving soil CO2 emissions, accounting for 55.7% and 45.1% of the variations, respectively. Therefore, short-term atmospheric N deposition stimulated soil respiration primarily via altering soil pH and nitrogen pool components in the degraded alpine meadow.
    Rainfall-runoff partitioning in small watersheds of different vegetation types in the loess area based on hydrogen and oxygen isotope tracing
    ZUO Yuzhu, PAN Chengzhong, MA Yongxing, MA Lan
    2024, 35(2):  399-406.  doi:10.13287/j.1001-9332.202402.027
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    Recognizing watershed runoff process and its component sources is a prerequisite for the rational use of water resources. To elucidate the effects and quantitative contributions of various vegetation types on the components of watershed runoff, we centered on the Caijiachuan main channel watershed in Jixian, Shanxi and five sub-watersheds with distinct vegetation types. By tracking the hydrological responses to two representative rainfall events and assessing the spatiotemporal variations in hydrogen and oxygen isotope signatures, we aimed to discern disparities in the runoff processes across these sub-watersheds and pinpoint their constituent origins. The results showed that under medium rainfall condition, the contribution rates of event water to the river flow of each watershed were in an order of protected forest (94.3%) > Caijiachuan main channel (83.1%) > agro-pastoral composite (64.3%) > plantation-secondary forest (52.4%) > cropland (0.3%) > secondary forest (0.0%); under light rainfall condition, plantation-secondary forest (52.4%) > protected forest (58.5%) > cropland (40.6%) > secondary forest (15.8%) > agro-pastoral composite (12.5%) > Caijiachuan main channel (9.3%). The event water contribution rate of secondary forest and protected forest watersheds to runoff was higher than that of plantation watersheds. The secondary forests watersheds had a stronger runoff storage capacity. The event water contribution rate of protected forest and agro-pastoral composite watersheds under medium rainfall intensity condition was greater than that under light rainfall intensity condition, while the event water contribution rate of cropland, plantation-secondary forest, and secondary forest watersheds was in adverse. The event water contribution to the runoff of forested watersheds was greater than that of cropland watersheds, which may be related to the presence of silt dams at the mouth of agricultural watershed channels. This study can provide a scientific basis for the analysis of water conservation and runoff change attribution in the loess area of west Shanxi.
    Water conservation pattern of Fangcheng River Basin in Beibu Gulf and its response to precipitation
    GAN Wenjing, MO Shangxuan, ZHANG Jianhong, SONG Xianwei, XIAN Jinmei, YANG Lu, NONG Haiqin
    2024, 35(2):  407-414.  doi:10.13287/j.1001-9332.202402.020
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    Assessing the spatiotemporal patterns of watershed water conservation under the influence of the South Asian monsoon climate and its response to precipitation is essential for revealing the evolving patterns of water conservation under different temporal scales. Following the principles of water balance and using the Soil and Water Assessment Tool (SWAT) model, we investigated the spatiotemporal patterns of water conservation and its response to precipitation in the Fangcheng River Basin of Beibu Gulf. The results showed that water conservation in Fangcheng River Basin calculated by SWAT model were 1637.4 mm·a-1, accounting for 50.7% of the mean annual precipitation. The variation of water conservation in different sub-basins was obviously different. Sub-basins with high forest coverage and steep slopes exhibited higher water conservation, while sub-basins with other land use types (such as cropland and grassland), gentle slopes, and intense human activities showed lower water conservation. At the monthly scale, both water conservation and its variation showed similar response characteristics to precipitation in the basin. The response of water conservation variation to sub-precipitation events could be classified into two types. For the short-term rainfall events (duration≤2 days), water conservation variation showed a linear relationship. For the medium to long-term rainfall events (2 days<duration≤10 days), water conservation variation showed a nonlinear curve, being influenced mainly by processes such as evapotranspiration. High-frequency short-duration precipitation events were more conducive to increasing ecosystem water conservation compared to the long-duration precipitation events.
    Effects of fresh-salt water interaction on spatial variations of soil organic carbon in reed wetland of Yellow River Estuary
    YU Miao, GUO Xuelian, LI Yunzhao, ZHANG Kun, DU Zhaohong
    2024, 35(2):  415-423.  doi:10.13287/j.1001-9332.202402.031
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    Estuarine wetlands exhibit significant interaction between fresh and salt water, with long-term carbon sequestration capability. We set up 60 sampling sites in the reed wetlands of the fresh-salt water interaction zone of the Yellow River Estuary, covering four different zones of the weak-intensity fresh-salt water interaction zone (WIZ), medium-intensity fresh-salt water interaction zone (MIZ), high-intensity interaction fresh-salt water zone (HIZ) and strong-intensity fresh-salt water interaction zone (SIZ). We investigated how fresh-salt water interaction affected the spatial variation of soil organic carbon (SOC) storage. The results showed that the area of reed wetland accounted for 17.8% of the total area of the fresh-salt water interaction zone the Yellow River Estuary, which mainly distributed in the WIZ and MIZ. The SOC content of reed wetland in the fresh-salt water interaction zone ranged from 1.09 to 3.65 g·kg-1, the SOC density was between 1.85-5.84 kg·m-2, and the SOC storage was (17.32±3.64)×104 t. The SOC content and SOC density decreased with increasing fresh-salt water interaction. There were significant differences in surface SOC content between different subzones of the fresh-salt water interaction zone. The surface SOC content decreased significantly with the increases of fresh-salt water interaction intensity. SOC density was positively correlated with SOC, TN, NH4+-N, and biomass, but negatively correlated with salt ions, soil bulk density, pH, and EC. SOC storage in the 0-30 cm soil layer accounted for 50.9%-64.2% of that in the 0-60 cm soil layer, while SOC storage in the 0-60 cm soil layer occupied 19.1%-37.7% of that in the 0-400 cm soil layer. The results could provide a scientific basis for accurately evaluating SOC storage of estuarine wetlands, improving carbon sink function and wetland management.
    Effects of light qualities on growth and physiological-biochemical traits of Scutellaria baicalensis
    YANG Yanmeng, ZHANG Jiaxing, LI Yaru, MA Jingran , WANG Duo, JIN Zhancai, XIE Lulu, DENG Jiaojiao, YE Ji, YU Dapao, WANG Qingwei
    2024, 35(2):  424-430.  doi:10.13287/j.1001-9332.202402.004
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    Canopy spectral composition significantly affects growth and functional traits of understory plants. In this study, we explored the optimal light condition suitable for enhancing Scutellaria baicalensis’s yield and quality, aiming to provide scientific reference for the exploitation and utilization of medicinal plant resources in the understory of forests. We measured the responses of growth, morphology, biomass allocation, physiological traits, and secon-dary metabolites of S. baicalensis to different light qualities. S. baicalensis was cultured under five LED-light treatments including full spectrum light (control), ultraviolet-A (UV-A) radiation, blue, green, and red light. Results showed that UV-A significantly reduced plant height, base diameter, leaf thickness, leaf area ratio, and biomass of each organ. Red light significantly reduced base diameter, biomass, effective quantum yield of photosystem Ⅱ (ФPSⅡ), and total flavonoid concentration. Under blue light, root length and total biomass of S. baicalensis significantly increased by 48.0% and 10.8%, respectively, while leaf number and chlorophyll content significantly decreased by 20.0% and 31.6%, respectively. The other physiological and biochemical traits were consistent with their responses in control. Our results suggested that blue light promoted photosynthesis, biomass accumulation, and secondary metabolite synthesis of S. baicalensis, while red light and UV-A radiation negatively affected physiological and biochemical metabolic processes. Therefore, the ratio of blue light could be appropriately increased to improve the yield and quality of S. baicalensis.
    Effects of exogenous melatonin on the osmotic regulation and antioxidant capacity of Ginkgo biloba seedlings under salt stress
    ZHOU Dan, LI Haiyan, WANG Xiujun, LI Qingwei
    2024, 35(2):  431-438.  doi:10.13287/j.1001-9332.202402.001
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    We investigated the effects of exogenous melatonin on the osmotic regulation and antioxidant capacity of 4-year-old Ginkgo biloba seedlings under salt stress. There were three treatments, with low (50 mmol·L-1), medium (100 mmol·L-1), and high (200 mmol·L-1) NaCl stress. Leaves were sprayed and the soil was watered with melatonin solution (0, 0.02, 0.1, 0.5 mmol·L-1). The results showed that saline stress significantly inhibited the osmoregulation and antioxidant capacities of G. biloba seedlings. Application of exogenous melatonin at appropriate concentrations (0.02, 0.1 mmol·L-1) under salt stress could promote plant growth, reduce the rate of electrolyte leakage, decrease the content of flavonoids and malonic dialdehyde, and enhance peroxidase and superoxide dismutase activities in leaves. High concentration (0.5 mmol·L-1) of exogenous melatonin would aggravate the oxidative and osmotic stresses. The 0.02 and 0.1 mmol·L-1 exogenous melatonin alleviated osmotic stress and oxidative stress in G. biloba seedlings under salt stress, while the 0.02 mmol·L-1 exogenous melatonin treatment had the best effect on NaCl stress alleviation. Ground diameter, branch width, branch length, electrolyte leakage rate, superoxide dismutase activity, and flavonoids content could be used as the key indices for rapid identification of the degree of salt stress in G. biloba seedlings.
    Effects of light and water availability on the growth of Aglaia duperreana seedlings
    GAN Feifei, ZHAO Lijun, HUO Chanchan, WANG Sheng
    2024, 35(2):  439-446.  doi:10.13287/j.1001-9332.202402.013
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    Aglaia duperreana, a species with a long cultivation history, is of high ornamental value. To understand the growth and photosynthetic changes of A. duperreana seedlings under variable environmental conditions, we conducted an experiment with light intensities adjusted at 70%, 50% and 30%, crossed with three moisture treatments at 70%, 50% and 30% of field capacity, and a control group which maintained 90% light intensity and 90% field capacity. The results showed that both drought stress and shading propensity significantly inhibited the growth of A. duperreana seedlings, with stronger impacts from drought stress. The increments in stem height and ground diameter, net photosynthetic rate, transpiration rate, stomatal conductance, and chlorophyll content were decreased with the maximum declines by 71.4%, 81.2%, 93.2%, 71.5%, 70.6% and 30.4%, respectively. Under severe drought stress (30% of field capacity), partial shading (50% of translucency) appeared to lessen the detrimental effects of drought. The combination of 70% translucency and 70% field capacity was optimal, resulting in higher increments in stem height, leaf area, net photosynthetic rate, transpiration rate, and stomatal conductance. The maximum fluorescence, variable fluorescence, PSⅡ potential activity, and PSⅡ maximum light energy conversion efficiency increased and then decreased with decreasing moisture. These findings suggested that A. duperreana could adapt to drought and shading stress by modulating growth, enhancing chlorophyll content, and adjusting photosynthetic system. Maintaining translucency at 70% and field moisture capacity at 70% could promote photosynthesis, with positive consequences on growth of A. duperreana.
    Influence of tillage methods combined with mulching on soil physical properties and potato yield in dry farming area under different precipitation years
    MA Xiaoming, LI Dan, LEI Jia, YU Jie, WANG Nan, HOU Xianqing, WEI Na, LI Rong
    2024, 35(2):  447-456.  doi:10.13287/j.1001-9332.202402.012
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    We conducted a field experiment in the dry farming area in south Ningxia from 2018 to 2021, to explore the influence of tillage methods combined with mulching on soil bulk density, aggregate content, soil water storage and potato yield under different precipitation years. There were four tillage methods (15 cm depth ploughing, and 30 cm, 40 cm and 50 cm depth subsoiling) and three mulching measures (mulching with oat straw, plastic film and no mulching), with the ploughing depth of 15 cm without mulching as control. The results showed the combination of tillage and mulching effectively reduced soil bulk density in 0-60 cm layer after three years of farming compared with that prior to the experiment. Under the same tillage mode, the best effect was achieved in mulching with oat straw under different precipitation years. To be specific, the best effect in 20 cm and 40 cm soil layers was achieved in mulching with oat straw for 30 cm depth subsoiling, in 60 cm soil layer for 15 cm ploughing in wet year, and for 40 cm depth subsoiling in 20 cm, 40 cm and 60 cm soil layers in normal and dry years. In 0-20 cm soil layer, the content of >0.25 mm soil aggregate was the highest for 40 cm depth subsoiling with oat straw mul-ching in all the three years. In 20-40 cm soil layer, the content was the highest for 15 cm depth ploughing with oat straw mulching in wet year, and for 40 cm depth subsoiling with oat straw mulching in normal and dry years. In 40-60 cm soil layer, content was the highest for 15 cm depth ploughing with plastic film mulching, 30 cm depth subsoiling with plastic film mulching, and 30 cm depth subsoiling with oat straw mulching in wet, normal and dry years, which was increased by 18.8%, 27.0%, and 35.8%, respectively, compared with the control. In the key growth stage (from squaring to tuber expansion) of potatoes, soil water storage in 0-100 cm layer was optimal for 30 cm depth subsoiling with oat straw mulching in wet year and for 40 cm depth subsoiling with oat straw mulching in normal and dry years, with an increase of 19.4%, 19.5%, and 23.7%, respectively. Potato yield was the highest for 30 cm depth subsoiling with oat straw mulching in wet year and for 40 cm depth subsoiling in normal and dry years, with an increase of 84.6%, 81.7%, and 106.3%, respectively. The correlation analysis showed that improved soil physical properties played a significant role in increasing potato yield, with the most significant role of soil bulk density and soil water storage at the squaring stage. Potato yield was high at a tillage depth of 34.67-36.03 cm. We concluded that the combination of tillage method and mulching could effectively improve soil physical pro-perties and increase soil water storage in the growth stage of potatoes, thereby significantly increa-sing potato yield. Potato yield in dry farming area could be enhanced through 30 cm depth subsoiling with oat straw mulching in wet years, and 40 cm depth subsoiling with oat straw mulching in normal and dry years.
    Ecosystem service tradeoff and synergistic relationship in the Yellow River Delta High-Efficiency Eco-Economic Zone
    LU Chang, CAI Xueqin, HAO Canshu, LIU Yuzhen, WANG Zhiyu, MA Ya'nan
    2024, 35(2):  457-468.  doi:10.13287/j.1001-9332.202402.026
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    Exploring the tradeoff and synergy relationship among ecosystem services in the Yellow River Delta High-Efficiency Eco-Economic Zone is of great practical significance for regional ecosystem service function zoning and high-quality development. Using the InVEST model, spatial auto-correlation and trade-off synergism (ESTD) model, we analyzed the spatial and temporal variations of five ecosystem services (habitat quality, carbon storage, soil conservation, water conservation, and water purification), as well as their trade-off and synergistic relationships at the township scale from 2000 to 2020. The results showed that habitat quality, carbon storage, and nitrogen and phosphorus output decreased as a whole from 2000 to 2020, and soil conservation and water purification increased. Habitat quality showed a distribution pattern of high in the north and low in the south, and carbon sto-rage, nitrogen and phosphorus output, soil conservation and water purification showed a pattern of low in the north and high in the south. During the study period, synergistic relationships among the five ecosystem services were predominant in both time cross-section and time period, but there were still differences, with synergistic relationships mainly between carbon storage and other services in time cross-section, and between habitat quality and other ser-vices in time period. Our results can provide theoretical guidance and practical reference for the enhancement of ecosystem services and the zoning of ecosystem functions, as well as basic support for the optimization of spatial patterns of national territory.
    Identification of priority areas for territorial space ecological restoration in arid area of Northwest China: A case study of Zhangye City in Heihe River basin
    DOU Hanmei, ZHAO Ruifeng, CHEN Xidong, SHI Jing, WANG Jingfa, LIU Fushou
    2024, 35(2):  469-479.  doi:10.13287/j.1001-9332.202402.025
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    Determining priority areas for territorial ecological restoration in the arid region of Northwest China based on the holistic protection and systematic governance is an important measure to build solid national ecological security barrier and promote the construction of territorial ecological civilization. Taking Zhangye City, a typical arid area city in Northwest China, as an example, we constructed the research framework of “ecological network-ecological sensitivities-ecological degradation” from two aspects of internal defects and external threats of ecological networks by using circuit theory and assessment methods of ecological service function importance, ecological sensitivity, and ecological degradation. We then identified the priority areas of territorial ecological restoration in northwest arid region and put forward the restoration strategies. The results showed that the priority areas of ecological restoration in Zhangye City were concentrated in the artificial shelterbelt along rivers and the plain-desert-oasis transition zone with fragile ecology and strong human interference. The ecological network of the study area included 39 ecological sources and 99 ecological corridors, and the highly sensitive and degraded areas were 1595.40 and 6.65 km2. Based on the internal defects and external threats of the ecological network, we identified 31 ecological pinch points, 7 obstacle points, and 753.56 km2 ecological source areas in the territorial spatial ecological restoration priority area. These areas were related to the connectivity of the ecological network internally and the stability maintenance of the ecosystem outwards, and were the areas to restoration in the future. Following the concept of overall protection and system restoration of territorial space, we put forward the idea of territorial space restoration by integrating internal defects and external threats of ecological network, which could provide scientific decision-making basis for comprehensive ecosystem management and territorial optimization of Zhangye City.
    Assessment of land use change of ecological green wedge and cooling island effect: A case study of Wuhan, China
    LIU Huimin, QIAN Wenqi, TANG Lujia, WU Yihan, ZENG Jiaying
    2024, 35(2):  480-488.  doi:10.13287/j.1001-9332.202402.019
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    The construction of urban ecological green wedges, which can mitigate the heat island effect through cooling and ventilation effects, is an important way to enhance the adaptation of cities to climate change. Dynamic monitoring and periodic assessment of both the conservation status and cooling effect of ecological green wedges is a key to ensure the heat mitigation benefits. Based on multi-source remote sensing data, we systematically analyzed the land use changes of six ecological green wedges in Wuhan in 2013 and 2020 using the methods of Markov transfer matrix, land use dynamics, and comprehensive index of land use degree, and evaluated the changes in surface temperature of the ecological green wedges and their cooling island effect. Results showed that the ecological green wedges in Wuhan generally had a large amount of construction land encroaching on ecological land from 2013 to 2020, with the water decreased the most. With the continuous deterioration of ecological green wedges, their land surface temperatures showed rising trends, together with significant weakening trends in cooling island effects. Among all the six wedges, the Dadonghu, Tangxun, and Wuhu exhibited relatively better ecological conservation, slighter land use change and lower overall development degree. Qinglinghu and Houguanhu demonstrated average levels of conservation. Fuhe experienced the most severe change under the significant influence of the westward policy of Wuhan City, with the proportion of water decreasing by 7.1%, warming up by 3.00 ℃, and the largest reduction in cooling distance for the cooling island effect, amounting to about 210 m. The results provided scientific evidence for the urban heat island mitigation-oriented planning and management of ecological green wedges for Wuhan City.
    Impact of different grade roads on ecological networks: A case study of Fuzhou City, China
    JIA Dingyi, GUO Rongpeng, QIU Weiguo, WU Zhilong, LIN Sen, HU Xisheng
    2024, 35(2):  489-500.  doi:10.13287/j.1001-9332.202402.023
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    The expansion of roads exacerbates the fragmentation of ecological networks and obstructs landscape connectivity. Scientific analysis of the impacts of different grades of roads on landscape connectivity and ecological networks is crucial for guiding road planning and ecological conservation. Based on the data of 2020 road network, land cover types, and digital elevation models, we used morphological spatial pattern analysis and circuit theory to construct ecological networks within different species dispersal distances (1, 3, 5, 10 km) in Fuzhou. We analyzed the impacts of roads of different grades (motorway, urban expressway, primary and secondary highway) on landscape connectivity at the landscape-patch-corridor scale. The results showed that at the landscape scale, overall landscape connectivity was significantly positively correlated with species dispersal distance. The motorway, urban expressway, primary and secondary highway had the lowest decline rate of overall landscape connectivity within a 10 km species dispersal range, being reduced by 15.6%, 5.3%, 1.5% and 5.2%, respectively. At the patch scale, in the comparison of roads of different grades, motorway led to the highest decline rate of patch connectivity within 1 and 5 km species dispersal range, while primary highway led to the highest decline rate of patch connectivity within 3 and 10 km species dispersal range. At the corridor scale, urban expressway led the highest increase rate of indices. The cost-weighted distance of the overall least-cost path, the ratio of cost-weighted distance to length, ove-rall effective resistance, and total corridor length within 5 km species dispersal range were increased by 43.4%, 33.2%, 57.3%, and 7.3%, respectively. As the distance of species dispersal increased, the patches with high importance were reduced from the northern, central, and northwestern regions to the northern regions, leading to a decrease in the living space of species, and the key corridors were gradually extending from the northwestern and southern regions to the central regions. Our results can guide the construction and optimization of Fuzhou’s ecological network from an overall perspective, and provide a scientific basis for biodiversity conservation, ecological restoration, and road network planning under the context of limited land resource utilization.
    Detritivores accelerate litter mixture decomposition effect via greater consumption of high quality litter
    CAI Xiaoling, YANG Guangrong, FENG Ying, SHEN Rong, ZHAO Liang, LIN Dunmei
    2024, 35(2):  501-506.  doi:10.13287/j.1001-9332.202402.002
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    To explore the mixing effect of litter decomposition and the role of detritivores, we conducted a laboratory-based microcosm experiment to study the influence of detritivores on litter mixture decomposition by using two litter species with contrasting quality, i.e., Cinnamomum camphora and Michelia × alba, and a detritivore (isopoda). After 100 days incubation, the decomposition rate of litter mixture was 52.1%, slower than that of M. alba (62.6%) and significantly faster than that of C. camphora (33.6%). The addition of isopods significantly increased litter decomposition rate, with C. camphora, M. alba, and the mixture increased by 14.4%, 20.1% and 22.1%, respectively. There was no significant mixing effect without isopods. Adding isopods significantly promoted the mixing effect of litter decomposition, with a value of the litter mixture decomposition effect of 8.6%. The detritivores increased litter decomposition rate and mixing effect through increasing consumption of litter with better quality.
    Characteristics of pine wood nematode disease in Nankang District, Ganzhou, Jiangxi Province, China
    YUAN Jiayu, Xiong Li, WU Zhiwei, ZHU Shihao, KANG Ping, LI Shun
    2024, 35(2):  507-515.  doi:10.13287/j.1001-9332.202402.030
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    Pine wood nematode (PWN) disease is one of the major disasters in forests of southern China, causing substantial forest resources and ecological and economic losses. Based on field surveys and WFV image data from the GF-1 satellite, we constructed a spatial identification model of PWN disease with the random forest model to explore the relative influences of topography, human activities and stand factors on the occurrence of diseases and predict their spatial distribution. We then used the spatial autocorrelation analysis to assess the distribution characteristics of PWN disease at the regional scale. The results showed that the random forest model constructed in this study was effective in identifying pine nematode diseases (AUC value=0.99, overall accuracy=0.96). The norma-lized difference greenness index (NDGI), the distance to the highway, and normalized vegetation index (NDVI) were important factors in explaining the spatial variations of PWN disease occurrence. There was a positive spatial correlation in the occurrence of PWN disease (not randomly distributed but with obvious spatial aggregation characteristics). The high occurrence areas of pine wood nematode disease concentrated in Chitu Township, Zhufang Township and Shibatang Township, low occurrence areas concentrated in the vicinity of Rongjiang Street. The areas far away from the highway, low in elevation, and close to county roads were suffered to PWN disease. The results could serve the regional monitoring of pine nematode disease occurrence and provide practical guidance for PWN disease management.
    Effects of temperature and initial pH on the growth of four dominant cyanobacteria species in biological soil crusts
    WANG Yifan, LI Xuan, LUO Shanshan, HUANG Zhuochao, Dingzhenyuzhen, ZHOU Nan, ZHAO Yunge
    2024, 35(2):  516-522.  doi:10.13287/j.1001-9332.202402.028
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    Biological soil crusts are of great significance for environment health and sustainable development in arid and semi-arid areas. Cyanobacteria, Microcoleus vaginatus, Scytonema sp., Nostoc sp., and Anabaena sp. are the dominant species in microbial community of biological soil crusts worldwide. Considering their broad application prospect, it is meaningful to cultivate them extensively. We examined the effects of temperature (10, 20, 25, 30, 35 ℃) and initial pH (4, 6, 8, 10, 12) on biomass and solution pH towards the four species of cyanobacteria with liquid culture in laboratory. The results showed that the biomass of the four cyanobacterial species grew slowly under 20 ℃, and that all species could grow in 25-35 ℃, with the highest growth rate at 25 and 30 ℃. The optimum culture temperature of different cyanobacterial species was slightly different. The optimum culture temperature was 25-30 ℃ for Scytonema sp. and Nostoc sp., and 30 ℃ for M. vaginatus and Anabaena sp. The four cyanobacterial species had a strong ability to adjust solution pH and proliferate in five different initial pH conditions. The highest maximum biomass and specific growth rate were recorded in the culture environment with initial pH of 4, while the lowest maximum biomass and specific growth rate were observed in initial pH of 12. Our results would provide scientific basis for the propagation of dominant cyanobacteria in biological soil crusts.
    Review on mechanism and remediation strategies of dissolved oxygen abnormal in surface water
    WANG Jiajia, MA Xiangjuan, ZHENG Heng, YU Shujing, XU Hai, FENG Huajun
    2024, 35(2):  523-532.  doi:10.13287/j.1001-9332.202402.029
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    Dissolved oxygen (DO) is an important index to evaluate the quality of surface water environments. In recent years, anomalies in DO level have emerged as a major contributor to the decline of surface water quality. These anomalies have triggered several ecological and environmental challenges such as biodiversity loss, the degradation of water environmental quality, intensification of eutrophication, and an exacerbation of the greenhouse effect. Understanding the mechanisms underlying DO anomalies and devising targeted remediation strategies holds paramount importance in the scientific pursuit of water pollution control and aquatic ecosystem restoration. We explored and summarized the fluctuations and abnormal mechanism of DO concentration in surface water, focusing on factors like oxygen solubility, reoxygenation rates, and oxygen consumption by water bodies. We compiled a range of approaches for addressing DO anomalies, including pollution source management, artificial oxygenation, and the reconfiguration of aquatic ecosystems. Ultimately, we underscored the emerging significance of monitoring and regulating DO level in surface waters. Future research in this realm should encompass the establishment of distinct quality standards for surface water, the development of a comprehensive real-time spatial monitoring system for DO levels across watersheds, and the formulation of standardized procedures and technical norms.
    Effects of urban green space landscape pattern on flood retention efficiency from “urban-block” scale perspective
    LI Bei, JIAO Sheng, ZHOU Min, ZHOU Yuan
    2024, 35(2):  533-542.  doi:10.13287/j.1001-9332.202402.022
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    Under the background of frequent flood disasters and stock planning challenges, clarifying the relationship and mechanism of urban green space landscape patterns and flood retention efficiency at multiple spatial scales has become a critical scientific issue in realizing the maximum flood retention efficiency of limited urban green spaces and improving the capabilities of urban flood control. We reviewed and summarized the factors, mechanisms, and scale differences in the influence of green space landscape patterns on flood retention efficacy at the urban and block scales. Based on the causes for differences in conclusions and research deficiencies, we suggested that future studies should focus on watershed-scale research and expand the investigation into three-dimensional green space landscape patterns. Additionally, attention should be paid to urban and suburban areas separately, and a set of research indices with indicative significance for the flooding process should be established for different flood-sensitive areas and block structures. These measures will help quantitatively reveal how green space landscape patterns of urban and block scales affect flooding process, providing theoretical guidance for urban planning and establishing urban flood safety patterns.
    Research progress in parameterizing irrigation and fertilization in land surface model
    WANG Fei, ZHOU Zihan, HAN Dongrui, WANG Meng, WEI Qinggang, LUO Xiubin, GAO Rui, ZHANG Zhuoran, FANG Jingchun
    2024, 35(2):  543-554.  doi:10.13287/j.1001-9332.202402.021
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    Under the context of global climate change and growing population, irrigation and fertilization have become important ways to ensure food production, with consequences on water cycling, energy flow, and materials cycling in terrestrial ecosystems. In the land surface model (LSM), coupling irrigation and fertilization schemes are of great importance for clearly understanding the land-atmosphere interactions to ensure food security. We reviewed the expression methods of three key parameters, namely, the applied method, usage, and time in the parameterization process of irrigation and fertilization (nitrogen fertilizer) in LSM. We found that the ways to irrigate and ferti-lize in LSM are different from the ways used in actual practice due to the limitation of the high resolution of spatio-temporal data, which makes it difficult to understand the actual influences of irrigation and fertilization on grain yield, environment, and local climate. Finally, we proposed future works: 1) taking the differences of crop water demand into account and making the different irrigation thresholds for different crops to properly evaluate the total and intensity of water consumption of different crops; 2) using the field records and the regional grid data of fertilization and irrigation developed in recent years to develop parameterized schemes that are more in line with actual agricultural operations, which can accurately reveal their economic, ecological, and climatic effects; 3) developing fertilization diagnosis scheme considering crop type, phenological stage, and soil basic fertility as the supplementary scheme in LSM, to improve the applicability and simulation accuracy of LSM in the areas without nitrogen fertilizer data.
    Research progress on the method and index evaluating strong seedlings of winter wheat during overwintering stage
    CAI Hongmei, WANG Feifei, WANG Pengna, TANG Zhiwei, HUANG Weixiang, ZHENG Baoqiang, LI Jincai, CHEN Xiang
    2024, 35(2):  555-563.  doi:10.13287/j.1001-9332.202402.011
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    The extreme weather disasters before winter caused by global climate change seriously affect the formation of strong seedlings of wheat. Cultivating strong seedlings is the premise of realizing high yield, high efficiency, and high quality of wheat. The cultivation of strong wheat seedlings is closely related to seed quality, straw returning quality, land preparation quality, sowing quality, water and fertilizer operation and meteorological factors. Seed quality and tillage measures are the primary factors affecting the cultivation of strong wheat seedlings, which determine the quality of wheat seedling emergence. Secondly, meteorological factors determine growth rate and photosynthetic production of wheat seedlings. Mounting studies have addressed the cultivation of strong seedlings and the evaluation of seedling conditions of wheat. This research focused on comparing and summarizing the evaluation methods and indices of strong seedlings of winter wheat, the historical changes of evaluation standards and the main technical measures for cultivating strong seedlings, and proposed the cultivation and evaluation methods of strong seedlings of winter wheat in the future. We aimed to further improve the evaluation method of winter wheat strong seedlings, advance the classification management, precise guidance and fine service of winter wheat seedlings, and realize strong seedlings through scientific and technological ways.
    Biogenic element driving mechanism in the occurrence of Chinese coastal eco-environmental disasters and regulation for ecological environment health
    XING Jianwei, SONG Jinming, YUAN Huamao, LI Xuegang, DUAN Liqin, QU Baoxiao, WANG Qidong, MA Jun, WANG Yueqi, DAI Jiajia
    2024, 35(2):  564-576.  doi:10.13287/j.1001-9332.202402.018
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    In recent decades, China’s coastal ecological environment has undergone significant changes under multiple pressures such as climate change and high intensity of human activities. The occurrence and scale of harmful algal blooms represented by the red tide and the green tide are increasing rapidly. Moreover, environmental problems such as hypoxia and acidification in seawater have become increasingly prominent. It is urgent to find out the occurrence mechanism and prevention measures of marine eco-environmental disasters. Therefore, we explained the connotation of the concept of “marine eco-environmental disaster” for the first time, and systematically interpreted the biogenic element driving mechanisms in the occurrence of eco-environmental disasters in China nearshore area in the aspects of exogenous input of nutrients, the mineralization and decomposition of marine organic matters and nutrient regeneration, as well as the abnormal nutrient structure in offshore waters. We pointed out that the drastic increases of terrigenous nutrient discharge caused by enhancing human activities, together with the complex biogeochemical cycle process after biogenic elements entering the sea, led to the frequent occurrence of coastal eco-environmental disasters. On this basis, combined with the latest research progress in this field, we put forward the regulatory schemes for coastal ecological environment health based on the controlling of seawater biogenic element. That is, based on land-sea integration strategy, the reduction of land-source pollutants, especially inorganic nitrogen from land, coastal zone and into the sea, and the normalization of nutrient structure in coastal seawater through artificial regulation technology, are the key points to reduce and control the occurrence of disasters and improve the quality of the coastal ecosystems.