Table of Content

15 September 2023, Volume 34 Issue 9

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Nutrient content and resorption efficiency of leaves of broad-leaved trees along altitudes in Wuyi Mountains, China

WU Xinyang, SHAO Jing, CHEN Xiaoping, LI Jinlong, HU Dandan, ZHONG Quanlin, CHENG Dongliang

2023, 34(9):  2305-2313.  doi:10.13287/j.1001-9332.202309.007

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To reveal the variation of leaf nutrient utilization strategies with altitude gradient in subtropical mountain broadleaved trees, 44 species of broadleaved trees at different altitudes (1400, 1600 and 1800 m) in Wuyi Mountains were selected to measure nutrient content, stoichiometric ratio, and nutrient resorption efficiency of green and senescent leaves, and analyzed their allometric growth relationships. The results showed that nitrogen (N) and phosphorus (P) contents in green leaves were significantly higher than those in senescent leaves, which increased with the increases of altitude. The average values of phosphorus resorption efficiency (PRE) and nitrogen resorption efficiency (NRE) were 48.3% and 34.9%, respectively. PRE was significantly higher than NRE. There was no significant difference in nutrient resorption efficiency with altitude. NRE had positive isokinetic growth with and mature leaf N content at low altitude (1400 m) and negative allometry growth with senescent leaf N content at high altitude (1800 m). PRE and N and P contents of senescent leaves had negative isokinetic growth at low altitude (1400 m) and negative allometry growth at high altitudes (1600 and 1800 m). PRE-NRE allometric growth index was 0.95 at each altitude. The nutrient contents of green and senescent leaves increased with the increases of altitude, but altitude did not affect nutrient resorption efficiency. Plants preferred to re-absorbed P from senescent leaves. Nutrient resorption efficiency of leaves at high altitude affected the nutrient status of senescent leaves.

Response of needle photosynthetic and anatomical characteristics of naturally regenerated Pinus koraiensis seedlings to different canopy densities

YUAN Shuyuan, ZHANG Peng, SHEN Hailong

2023, 34(9):  2314-2320.  doi:10.13287/j.1001-9332.202309.004

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We took 5-year-old Pinus koraiensis seedlings under natural secondary forests with canopy densities of 0.2-0.3, 0.4-0.6, and 0.7-0.9 at Laoshan Plantation Experimental Station in Maoershan Experimental Forest Farm of Northeast Forestry University as monitor object, and P. koraiensis seedlings under full-light environment as control (CK), to investigate the photosynthetic characteristics and the anatomical structure of P. koraiensis needles in response to the changes of canopy densities. The results showed that the height and diameter of P. koraiensis seedlings tended to decrease while specific leaf area increased with the increases of canopy densities. The total biomass of P. koraiensis seedlings under different canopy densities ranked in an order of 0.4-0.6＞CK＞0.7-0.9＞0.2-0.3. Photosynthetically active radiation (PAR) was significantly and positively correlated with leaf biomass, stem biomass, and root biomass. The net photosynthetic rate, transpiration rate, and intercellular CO₂ concentration of P. koraiensis seedlings showed a decreasing trend with the increases of canopy densities, while the stomatal conductance showed an increasing trend. Net photosynthetic rate and chlorophyll a/b showed a significant positive correlation with PAR. Stomatal density showed a gradual decreasing trend with the increases of canopy densities, and the needle cross-sectional area, mesophyll tissue area, xylem area, and phloem area of P. koraiensis seedlings under canopy density 0.4-0.6 were significantly higher than those in other treatments. P. koraiensis seedlings with stronger photosynthetic abilities and higher needle anatomy parameters under canopy density 0.4-0.6, and were able to maintain strong competitiveness in this habitat. Those results indicated that 5-year-old P. koraiensis seedlings need certain shading environment.

Physiological responses of typical subtropical landscape shrubs to artificial light at night

SHEN Shiyi, WANG Jianwu, ZHOU Tianhuan, MA Yuandan, WANG Bin

2023, 34(9):  2321-2329.  doi:10.13287/j.1001-9332.202309.002

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Artificial light at night is rapidly spreading and has become an important component of global change. Although numerous studies have focused on its potential ecological impacts, the physiological response mechanisms of landscape plants to artificial light at night have rarely been quantified. With common landscape shrubs in subtropical regions of China, Hydrangea paniculata, Photinia fraseri and Ligustrum japonicum, as test materials, we exa-mined the responses of antioxidant enzyme system and biomass in the light environment at night under different light quality (yellow light, white light) with different light intensities (20, 40, 60 lx) . The results showed that artificial light at night significantly increased the membrane peroxidation, stimulated plant antioxidant protection systems and raised the antioxidant enzyme activities of the three species. The effects of light quality on plant antioxidant enzymes varied across dspecies. The peroxidase (POD) and catalase (CAT) activities of H. paniculata under white light were 1.5 and 1.3 times as that under yellow light, respectively. Both enzyme activities of P. fraseri were 1.1 times as that under white light than under yellow light. The activities of two enzymes in L. japonicum under white light were 88.6% and 99.5% of those under yellow light, respectively. The antioxidant enzyme activities of the three species increased with increasing light intensity at night, whereas the contents of malondialdehyde increased rapidly and the antioxidant enzyme activities decreased when beyond a certain light intensity threshold (at 120 d, the threshold was about 40 lx). The protective enzymes that played the major role under nighttime light stress were different among the three species. For H. paniculata, POD and CAT complemented each other to resist stress-induced oxidative damage, while the main enzyme of L. japonicum was POD. The biomass of the three species increased significantly under artificial light at night. H. paniculata was the most sensitive to nighttime light stress, while L. japonicum had the strongest resistance to the stress. The deciduous shrub H. paniculata could tolerate the white night light lower than 40 lx, while the evergreen shrubs P. fraseri and L. japonicum could tolerate the yellow night light lower than 40 lx.

Response of resin canal area of Pinus tabuliformis with different ages to climate change in Taiyue Mountains, China

DONG Yibo, XIE Pingping, LIU Yang, SUN Bingzhe, ZHANG Xianliang

2023, 34(9):  2330-2336.  doi:10.13287/j.1001-9332.202309.008

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To investigate the responses of resin canal area of Pinus tabuliformis with different ages to climate change, we analyzed the relationship between the resin canal area and climate factors from 1972 to 2017 in P. tabuliformis plantation at young age, middle age, near-mature, mature, and over-mature periods in Taiyue Mountains, Shanxi Province. The results showed that 55.7% to 75.2% of resin canal occurred in earlywood. The mature and over-mature periods had the largest resin channel area, sequentially followed by near mature, middle age, and young age periods. Annual mean latewood resin canal area increased significantly in near-mature period and mature period, but not in other periods. There was a significant negative correlation between earlywood resin canal area and minimum temperature during the growing season (May to July) for trees at middle age period. Earlywood resin canal area of mature trees showed significant negative correlation with minimum temperature during the growing season, but significant positive correlation with drought (PDSI) in the non-growing season (previous September to current April). The total area of earlywood resin canal at the young, near-mature, and mature periods was less influenced by climate than other periods. The minimum growing season temperature was a limiting factor to earlywood resin canal growth, while the non-growing season drought gradually became a limiting factor for earlywood resin canal with increasing tree age. The total area of earlywood resin canal decreased with increasing non-growing season drought and increasing growing season minimum temperature. In the context of global warming, the earlywood resin canal area may gradually decrease at all five periods, and the most reduction in the over-mature stage.

Geographical provenance variation of growth and wood properties of 18-year-old Schima superba

WANG Miao, WU Guoliang, ZHANG Rui, WANG Jiayi, WANG Yunpeng, HUANG Dazhuang, ZHOU Zhi-chun

2023, 34(9):  2337-2344.  doi:10.13287/j.1001-9332.202309.003

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We analyzed the variation patterns of growth and wood properties of 24 different provenances of 18-year-old Schima superba in Jian’ou, Fujian Province. A total of 11 growth and wood indices were measured, including tree height, diameter at breast height, wood basic density and anatomical structure. We analyzed the geographical variation patterns of growth and wood properties, and the provenance areas were divided. Further, the excellent timber provenances were selected according to different uses. The results showed that the variation of growth traits, which was 17.6%-27.3% with mean value of 22.4%, was larger than that of wood properties (7.0%-21.0%, mean 12.7%). Growth properties and some wood properties (fiber length, fiber lumen diameter and fiber cell wall thickness) had significant differences among provenances. Growth traits were not correlated with fiber traits, and they could be selected independently without emphasis on other traits. There was significant correlation between the longitudinal and radial growth indicators of wood properties, but they were not correlated with the wood basic density, which could be selected independently. In addition, the growth and wood properties were significantly influenced by temperature and precipitation, which showed a latitudinal variation pattern. According to Q-type clustering analysis, 24 provenances could be divided into four categories, of which southern provenances from distribution area of S. superba had vigorous growth and supper wood properties. They had smaller microfibril angle, higher maturity, longer fiber length, and thicker fiber cell wall. Finally, five excellent provenances were selected according to pulpwood and building use.

Compatibility predictive model for regeneration quantities of Larix gmelinii natural forest in Daxing’anling Mountains, China

XIAO Chen, TIAN Dongyuan, MA Rong, DONG Lingbo

2023, 34(9):  2345-2354.  doi:10.13287/j.1001-9332.202309.001

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The natural regeneration grade is an important foundation for formulating forest management measures. Traditional studies have only considered the regeneration quantities predictive model of the total stand or dominant tree species, but the consistency among the prediction results of different tree species and the total regeneration quantities of stand is not solved. That is, the regeneration prediction results at the stand level are not equal to the sum of the predicted results of all tree species. To address this, on the basis of the traditional counting model, we attempted to construct a compatibility predictive model for regeneration quantities of different tree species within the stand, which would provide a theoretical basis for the rational management and decision-making of natural forest. Based on the survey data from 96 standard plots of Cuigang Forest Farm, Xinlin Forest Farm, and Zhuangzhi Forest Farm in Daxing’an Mountains, we selected 30 basic indices from five aspects of site factor, soil factor, stand factor, tree diversity and stand spatial structure, and used Poisson model and negative binomial model as the basic models to construct the regeneration prediction models of Larix gmelinii, Betula platyphylla and other tree species. By comparing the accuracy and fitting effect of the two traditional counting models, we selected the optimal model and used the seemingly unrelated regressions to further construct the compatibility predictive model for regeneration quantities of different tree species. Poisson model was the best one for the regeneration of L. gmelinii, B. platyphylla, and other tree species. The test index RMSE of the compatibility predictive model for regeneration quantities of L. gmelinii, B. platyphylla, other tree species and total stand regeneration quantities were 388, 413, 504, and 871 trees·hm^-2, respectively. The adjusted R² was 0.389, 0.421, 0.488, and 0.407, respectively. The most influential variables for regeneration quantities of L. gmelinii, B. platyphylla and other tree species were Pielou evenness index of DBH (25.2%), herbal coverage (34.6%) and organic matter in B layer (23.2%). In this study, the compatibility predictive model system for regeneration quantities satisfied the additive logic among L. gmelinii, B. platyphylla, other tree species, and total stands, and provided a basis for accurately estimating natural regeneration.

Height-diameter models of regenerated saplings of Larix gmelinii based on dummy variable and quantile regression

LYU Lele, WANG Wenbin, DONG Lingbo

2023, 34(9):  2355-2362.  doi:10.13287/j.1001-9332.202309.005

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Based on data collected from 2054 saplings of Larix gmelinii forest in 55 fixed plots in 2018-2019 in Cuigang Forestry Station, Daxing’anling area, we classified the stand density index (SDI) into four classes, i.e., Class Ⅰ (SDI₁<1863 plants·hm^-2), Class Ⅱ (1863 plants·hm^-2≤SDI₂<2155 plants·hm^-2), Class Ⅲ (2155 plants·hm^-2≤SDI₃<2459 plants·hm^-2) and Class Ⅳ (SDI₄≥2459 plants·hm^-2) by using the quartile method. We constructed a dummy variable model and quantile regression model for the height-breast diameter of saplings of L. gmelinii with dummy variable method introduced SDI. The results showed that among the five selected representative non-linear tree height curve models, the Richards model fitted the best, with R_a², RMSE and MAE of 0.7637, 0.8250 m and 0.5696 m. The dummy variable model including the SDI constructed based on the Richards model showed a 1.3% increase in R_a² compared with the base model, while RMSE, MAE, and AIC decreased by 2.1%, 1.5%, and 11.2%, respectively. When the quantile τ was 0.5, R_a² of quantile regression model was the maximum, and RMSE, MAE, AIC was the minimum, being 0.7612, 0.8294 m, 0.5657 m, and -767.19, respectively. Compared with SDI₁, sapling height in SDI₂-SDI₄ was increased by 5.6%, 5.6%, and 11.3%, suggesting reasonable that regulation of stand density was conducive to increase the height growth of saplings in regeneration.

Variation of carbon source and sink along the environmental gradient from lakeside to highlands in Yuanchi swamp wetlands, Changbai Mountains, China

WANG Ting, MU Changcheng, SUN Ziqi, LI Meilin, WANG Wenjing, XU Wen, ZHAO Haiming

2023, 34(9):  2363-2373.  doi:10.13287/j.1001-9332.202309.006

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Lacustrine wetlands have long-term carbon storage capacity and contribute significantly to regional carbon cycle, but it is unclear how its carbon sinks respond to climate change. We measured soil heterotrophic respiration carbon emissions (CO₂ and CH₄), vegetation carbon sequestration, and related environmental factors (temperature, water level, etc.) of five kinds of natural swamps (Phragmites marsh-L, Carex schmidtii marsh-C, Rhododendron capitatum swamp-D, Betula fruticose swamp-H, Larix olgensis swamp-LT)by using static chamber gas chromatography and relative growth equation methods, along the water environmental gradients from lakeside to highlands in Yuanchi of Changbai Mountains. We quantified the carbon source/sink function (CSS) and global warming potential (GWP) of various swamp types by estimating ecosystem net carbon balance, and revealed the variation patterns and formation mechanisms of CSS and GWP along the environmental gradients, aiming to explore the response of carbon source/sink of lakeside wetland in high altitude area to climate change. The results showed that marshes (L and C) were weak sources (-1.018 and -0.090 t C·hm^-1·a^-1) at the lower habitats of the water environment gradient, shrub swamps (D and H) were strong or weak sinks (1.956 and 0.239 t C·hm^-1·a^-1) at the middle habitats, forest swamp (LT) was strong source (-3.214 t C·hm^-1·a^-1) at the upper habitat. The spatial changes were promoted by water level and suppressed by soil temperature. For GWP, strong thermal radiation for marshes (from 44.682 to 59.282 t CO₂·hm^-1·a^-1), cold radiation for shrub swamps (from -0.920 to -7.008 t CO₂·hm^-1·a^-1), and weak thermal radiation for forest swamp (11.668 t CO₂·hm^-1·a^-1), and their GWP was only promoted by soil temperature. Under current climate change background, marshes and forest swamp at both ends of the water environment gradient from lakeside to highlands played a positive feedback effect due to the increases of CH₄ or CO₂ emissions, while the middle shrub swamp still maintained a negative feedback effect in Yuanchi located the high-altitude area of the temperate Changbai Mountains.

Rhizosphere effects of moso bamboo and dominant tree species of secondary broadleaved forest on soil organic carbon mineralization

XU Xiongchao, ZHANG Qianqian, TENG Qiumei, ZHAO Mingshui, LI Yongchun

2023, 34(9):  2374-2382.  doi:10.13287/j.1001-9332.202309.010

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The rhizosphere effect of plants affects soil organic carbon (SOC) mineralization. It is still unclear for the mechanism by which the rhizosphere effect of dominant plants in secondary broadleaved forest habitats invaded by moso bamboo affects SOC mineralization. Taking broadleaved tree species (Quercus glauca and Cunninghamia lanceolata) and moso bamboo, dominating respectively in uninvaded secondary broadleaved forest and bamboo forest formed after the invasion as test materials, we investigated rhizosphere effect of plants on the SOC mineralization in laboratory incubation experiments. The results showed that carbon mineralization rates of Phyllostachys edulis (PE), Quercus glauca (QG) and Cunninghamia lanceolata (CL) rhizosphere soils were 20%, 26%, and 21% higher than bulk soils, respectively. Carbon mineralization of bulk soils of QG and CL was 22% and 26% higher, while that of rhizosphere soils was 14% and 11% higher than PE, respectively. The contents of water-soluble organic carbon and organic carbon in rhizosphere soils of the three species were significantly higher than those of bulk soil, and the abundance of rhizosphere soil bacteria was higher than that of non-rhizosphere. The contents of microbial biomass carbon, water-soluble organic carbon, and total nitrogen were important factors influencing carbon mineralization in rhizosphere, while water-soluble organic carbon and microbial metabolic quotient were important factors influencing carbon mineralization in non-rhizosphere. On the whole, the rhizosphere effect increased total SOC mineralization, driving by changes in microbial biomass carbon, water-soluble organic carbon, and total nitrogen content. The results could provide a theoretical basis for plant-soil interaction on soil carbon cycling in bamboo invasion habitats.

Effects of maize straw and its biochar application on soil organic carbon chemical composition and carbon degradation genes in a Moso bamboo forest

ZHANG Wenyi, JIANG Zhenhui, PAN Lixia, ZHOU Jiashu, LIU Juan, CAI Yanjiang, LI Yongfu

2023, 34(9):  2383-2390.  doi:10.13287/j.1001-9332.202309.018

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We investigated the effects of maize straw and its biochar application on soil organic carbon chemical composition, the abundance of carbon degradation genes (cbhI) and the composition of cbhI gene community in a Moso bamboo forest, to provide the theoretical and scientific basis for enhancing carbon sequestration. We conducted a one-year field experiment in a subtropical Moso bamboo forest with three treatments: control (0 t C·hm^-2), maize straw (5 t C·hm^-2), and maize straw biochar (5 t C·hm^-2). Soil samples were collected at the 3^rd and 12^th months after the treatment. Soil organic carbon chemical composition, the abundance and community composition of cbhI gene were determined by solid-state ¹³C NMR, real-time fluorescence quantitative PCR, and high-throughput sequencing, respectively. The results showed that compared with the control, maize straw treatment significantly increased the content of O-alkyl C and decreased aromatic C content, while maize straw biochar treatment showed an opposite effect. Maize straw treatment significantly increased the abundance of cbhI gene and the relative abundance of Penicillium, Gaeumannomyces and Marasmius. However, maize straw biochar treatment reduced the abundance of this gene. The relative abundance of dominant cbhI in soils was positively correlated with the content of O-alkyl C and negatively correlated with the content of aromatic C. Results of redundancy analysis showed that maize straw treatment had a significant effect on the microbial community composition of cbhI gene by changing soil O-alkyl C content, while maize straw biochar affected the microbial community composition of cbhI gene by changing soil pH, organic carbon, and aromatic C content. Maize straw biochar treatment was more effective in increasing soil organic carbon stability and reducing microbial activity associated with carbon degradation in the subtropical Moso bamboo forest ecosystem compared with maize straw treatment. Therefore, the application of biochar has positive significance for maintaining soil carbon storage in subtropical forest ecosystems.

Effects of combined natural synergists and chemical inhibitors on yield, nitrogen utilization and balance in wheat/maize rotation system

LI Changqing, JI Meng, MA Mengmeng, WANG Shuo, LIU Huan, SUN Zhimei

2023, 34(9):  2391-2397.  doi:10.13287/j.1001-9332.202309.012

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Urease inhibitors and nitrification inhibitors can enhance nitrogen (N) fertilizer utilization efficiency and reducing N losses through regulating urea-N transformation. Common urease or nitrification inhibitors, however, are predominantly chemically synthesized and high-cost. Furthermore, their inhibitory effects are mediated by soil pro-perties, climatic conditions, and crop systems. In this study, we conducted a field experiment using natural synergists humic acid/zeolite, along with chemical nitrification inhibitor dicyandiamide (DCD) and their combination to elucidate the impacts of natural synergists combined with chemical inhibitors on annual yield, nitrogen utilization efficiency, soil nitrate-N accumulation, and nitrogen balance within the wheat/maize rotation system. The treatments included no nitrogen fertilizer application (CK), single application of urea (N), urea +DCD (ND), urea + humic acid (NH), urea + zeolite (NP), urea + urease inhibitor N-butylthiophosphoric triamide + DCD (NUD), urea + humic acid + DCD (NHD), and urea + zeolite + DCD (NPD). The results showed that, compared to the treatments NH and NP, the integration of humic acid or zeolite with DCD (NHD and NPD) significantly increased maize yield (11268 and 11397 kg·hm^-2) and total annual yield (20494 and 20582 kg·hm^-2), which were comparable to those of combined chemical urease and nitrification inhibitors (NUD). The NHD and NPD treatments had higher nitrogen utilization efficiency and lower soil nitrate-N accumulation in 80-100 cm soil layer across all seasons relative to the N treatment, which had no significant difference compared to the NUD treatment. Furthermore, a decline in soil nitrogen surplus by 10.7% and 13.9% was observed when comparing the NHD and NPD treatments with the NH and NP treatments, respectively. These findings suggested that combined humic acid or zeolite and chemical nitrification inhibitors could effectively enhance crop yield and N utilization efficiency and meet the requirements of the green and environmental preservation of modern agriculture.

Effects of fine substance content in soil substrate on the formation of artificial cyanobacteria crusts

ZHAO Yanqiao, LIAN Yuchao, XU Wenwen, HAN Gaoling, ZHAO Yang

2023, 34(9):  2398-2404.  doi:10.13287/j.1001-9332.202309.014

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The use of artificial cyanobacteria crusts is one of the effective methods to prevention and control of desertification. Soil fine substance is one of the important factors limiting the colonization and growth of artificial cyanobacteria crusts. We compared the growth of artificial cyanobacterial crusts with different fine substance contents by setting the volume ratios of fine substance to quicksand as 0:1, 1:1, 2:1, 4:1 and 1:0. The results showed that the cover of artificial cyanobacteria crusts increased gradually with the increases of fine substance contents, while the contents of chlorophyll a and extracellular polysaccharide firstly increased and then decreased slightly. The optimum growth of artificial cyanobacterial crusts was achieved under the treatment of 4:1 ratio. Under such treatment after 60 days of incubation, artificial cyanobacteria crusts cover was 70%, and the contents of chlorophyll a, loosely bound exopolysaccharide (LB-EPS), tightly bound exopolysaccharide (TB-EPS), and glycocalyx exopolysaccharide (G-EPS) were 17.5, 70.0, 175.0, and 200.0 μg·cm^-2, respectively. Increasing the amount of cyanobacteria under the condition of low fine substance content could promote the formation and growth of artificial cyanobacterial crusts (0.5 g of cyanobacteria per petri dish was the optimal). It could provide a new idea for the large-scale culture of artificial cyanobacterial crusts inoculum.

Effects of gibberellic acid, kinetin and indole butyric acid mixture on sorghum salinity tolerance and grain yield in saline-alkali coastal zone

GUO Lina, LU Lin, DONG Xuerui, ZHANG Fenglu, YAN Peng, DONG Zhiqiang

2023, 34(9):  2405-2412.  doi:10.13287/j.1001-9332.202309.016

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The development and utilization of coastal saline-alkali lands hold significant importance in mitigating the shortage of cultivated land resources in China, enhancing the agro-ecological environment in coastal saline and alkaline areas, and ensuring national food security. We set up both pot and field trials (randomized block design) at Xinxiang experimental station of Institute of Crop Science, Chinese Academy of Agricultural Sciences (ICS-CAAS) and Dongying Yellow River Delta Modern Agricultural Research Base in Shandong Province in 2021 and 2022, respectively. The experimental materials, Jiliang 1 and Jiliang 2, underwent seed dressing with GKI composites at concentrations of 2.5 and 5 mL·kg^-1. These composites, which contained the main components of gibberellin, kinetin, and indole butyric acid, were denoted as GKI2.5 and GKI5.0, respectively. The control plots (CK) received water seed dressing. The aim was to assess the regulatory effects of GKI on salt tolerance and grain sorghum yield. Compared to CK, the GKI2.5 and GKI5.0 seed dressing treatments significantly enhanced the growth and development of the two grain sorghum varieties, increased antioxidant enzyme activity and soluble protein content of sorghum leaves, while reducing leaf malondialdehyde content. Moreover, the GKI treatments increased leaf net photosynthetic rate. Under field conditions, yields of Jiliang 1 and Jiliang 2 were enhanced by an average of 17.1% and 19.1%, respectively. In conclusion, GKI seed dressing treatment effectively promoted the growth and development of sorghum under salt stress. It enhanced the antioxidant and osmoregulatory capacities of leaves, reduced the level of membrane lipid peroxidation, and improved net photosynthetic rate of leaves, which together improved the salt tolerance and sorghum yield.

Seasonal variation characteristics and influencing factors of dissolved organic carbon of soil water in permafrost peatlands of the Great Hing’an Mountains in summer and autumn

JIANG Jingyi, SUN Xiaoxin, WANG Xianwei, WANG Shujie, MA Guobao, CHEN Ning, DU Yu

2023, 34(9):  2413-2420.  doi:10.13287/j.1001-9332.202309.015

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Dissolved organic carbon (DOC) plays a crucial role in the assessment of greenhouse gas emission and carbon balance in peatlands. However, limited research has been conducted on the seasonal variations and properties of soil water DOC content at different depths in the permafrost peatlands of the Great Hing’an Mountains. In this study, we analyzed the seasonal patterns of soil water DOC contents (surface, 10 cm, 20 cm, 30 cm, 40 cm, and permafrost layer) the permafrost peatlands of the Great Hing’an Mountains (Tuqiang Forestry Bureau), and investigated the influencing factors, such as electrical conductivity, dissolved oxygen, HCO₃^- concentration, pH value, oxidation-reduction potential, and CO₂ content. The stability of DOC was assessed by using UV-Vis spectrum. There were significant seasonal dynamics of DOC content in soil water, with higher contents in autumn and lower content in summer, ranging from 55.7 to 188.1 mg·L^-1. There were significant differences in DOC content among different soil depths, with the highest levels detected in the permafrost layer. The DOC content showed a significantly positive correlation with pH value and electrical conductivity, while showed a significantly negative correlation with redox potential, HCO₃^- concentration, and dissolved oxygen content. Additionally, there was a significantly positive correlation between DOC and CO₂ contents. The dissolved CO₂ content in soil water increased with soil depth, with the highest content observed in the permafrost layer. Results of spectral analysis showed higher aromaticity in autumn compared to summer, indicating greater stability of DOC during the autumn season. Our results clarified the seasonal variations of soil water DOC in permafrost peatlands of the Great Hing’an Mountains and could provide important data to understand the carbon cycling in the region.

Compound erosion effect of snowmelt, wind, and rainfall on sloping farmlands of Chinese typical Mollisol region

ZHAO Yajun, ZHENG Fenli, AN Xiaobing, SHI Hongqiang, HU Wentao, ZHANG Jiaqiong

2023, 34(9):  2421-2428.  doi:10.13287/j.1001-9332.202309.013

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Research on the processes and mechanisms of compound soil erosion by multiple forces can provide scientific guidance for precisely controlling cropland soil erosion. Based on the seasonal alternation of freezing-thawing, snowmelt, wind, and rainfall erosion forces on sloping farmlands under natural conditions from November to next October of each year, we used a set of indoor simulation experiments of multi-force superimpositions to analyze the compound soil erosion processes of snowmelt (1 and 2 L·min^-1), wind (12 m·s^-1), and rainfall (100 mm·h^-1). We further discussed the erosion effects of multi-force superimpositions. The results showed that, under single snowmelt erosion, an increase in snowmelt flow had a greater effect on sloping snowmelt erosion intensity than that of sloping runoff rate. When sloping snowmelt flow increased from 1 L·min^-1 to 2 L·min^-1, sloping runoff rate and erosion intensity increased by 2.7 and 4.0 times, respectively. Under snowmelt-wind superimposition erosion, previous sloping snowmelt erosion inhibited late wind erosion occurrence. As sloping snowmelt flow increased from 1 L·min^-1 to 2 L·min^-1, the inhibiting action subsequently increased and wind erosion intensity caused by previous snowmelt reduced by more than 50%. Both wind erosion and snowmelt-wind superimposed erosion intensified late rainfall erosion. The early wind erosion increased rainfall erosion by 24.5%. The snowmelt-wind superimposed effect increased the later slope rainfall erosion by 132.8% and 465.4% under 1 and 2 L·min^-1 snowmelt runoff rates, respectively. The compound soil erosion amount driven by multiple force superimposition was not the sum of the corresponding erosion amount caused by single erosion force, with promoting or inhibiting effects of erosion force superimposition. The erosion effect of snowmelt-wind superposition was negative, but that of wind-rainfall superposition and snowmelt-wind-rainfall superpositions were positive.

Effects of climate change on wind erosion in the three provinces of Northeast China

YANG Zhenkang, YANG Wanrong, LIU Zhijuan, GAO Weida, REN Tusheng, SHEN Yanjun, YANG Xiaoguang

2023, 34(9):  2429-2435.  doi:10.13287/j.1001-9332.202309.011

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The three provinces of Northeast China are crucial to national commodity grain production. Soils in those areas have begun to severely degrade after long-term high-intensity use, with wind erosion as one of the main reasons. Based on meteorological and soil data from 1981 to 2019, we evaluated the spatial-temporal characteristics of wind erosion on bare land in the three provinces of Northeast China by using the revised wind erosion equation (RWEQ), and analyzed the contributions of meteorological factors to wind erosion on bare land. The results showed that, the meteorological factors of wind erosion were overall high in southwestern part and low in northeastern part of the region. In general, wind erosion in the region was substantial, especially in Liaoning. During the 39 years, wind erosion significantly increased throughout the whole year and during the growing season, at a rate of 129 and 105 t·km^-2 per decade, respectively. The obvious increase in wind erosion was observed in the northwest Liaoning, Liaohe Plain, and Changbai Mountain area. Wind speed and air temperature were the main factors affecting wind erosion during the year and non-growing season, which contributed less during the growing season when precipitation contributed the most. We concluded that climate change has aggravated soil wind erosion in the three provinces of Northeast China.

Dynamic changes and driving factors of land surface phenology under the background of urbanization

HONG Xinqian, SUN Tao, CHEN Liding

2023, 34(9):  2436-2444.  doi:10.13287/j.1001-9332.202309.019

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Rapid urbanization would have significant impacts on vegetation phenology. However, the factors influencing the spatiotemporal changes in urban vegetation phenology are still unclear. We used five fitting methods to construct normalized difference vegetation index (NDVI) curves in the Beijing-Tianjin-Hebei urban agglomeration, and obtained the phenology characteristics of urban vegetation in this area from 2001 to 2019 by the threshold method. We compared the spring and autumn phenology in urban built-up areas and hilly areas, and analyzed the effects of precipitation, air temperature, and land surface temperature (LST) on vegetation phenology. The results showed that from 2001 to 2019, the start of the growing season (SOS) in urban built-up areas in the Beijing-Tianjin-Hebei agglomeration was on average 16.88 days earlier than that in hilly areas, and that the end of the growing season (EOS) in urban built-up areas was 12.22 days later than that in hilly areas. During the study period, the SOS of vegetation in urban built-up areas of the Beijing-Tianjin-Hebei region had been gradually delayed, while that in hilly areas was gradually advanced, and the rate of change of phenology in the urban built-up areas was faster than that in the hilly areas. The difference between the SOS of the two areas decreased significantly over time (-0.58 d·a^-1). As for the EOS, the urban built-up areas and hilly areas both showed a trend of delayed, but the differences between them was not significant with time (-0.10 d·a^-1). The contribution of LST in the urban built-up areas to SOS was close to that of air temperature, while the contribution of LST in hilly areas to SOS was only 1/2 of that of air temperature, indicating that the heat island effect and air temperature within the city jointly influenced urban vegetation phenology, and their contributions were almost equal. The results could help understand the role of urbanization in the variations of vegetation phenology and provide a reference for further assessment of carbon sink potential of urban vegetation.

Retrieving soil moisture using cosmic-ray neutron technology based on COSMIC model in the desert-oasis region

WU Shaoxiong, ZHANG Yongyong, ZHAO Wenzhi, KANG Wenrong, TIAN Zihan

2023, 34(9):  2445-2452.  doi:10.13287/j.1001-9332.202309.023

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Cosmic-ray neutron technology could estimate average soil moisture on scale of hectometers by monitoring the neutron intensity near the ground, which has been successfully applied in forest, grassland, farmland, and other ecosystems. To verify the reliability of Cosmic-ray Soil Moisture Interaction Code (COSMIC) model for retrieving mesoscale soil moisture in arid regions, we carried out soil moisture observation experiment by using the cosmic-ray neutron rover in the desert-oasis region of the middle reaches of Heihe River. The results showed that the fast neutron intensity in the desert-oasis region were 350-715 counts·(30 s)^-1, and the calibrated high energy neutron intensity (N_cosmic) were (38.5±2.2) counts·(30 s)^-1, which was affected by land surface characteristics. Both COSMIC model (root mean square error=0.019 g·g^-1) and N₀ equation (root mean square error=0.018 g·g^-1) could well assess the mesoscale soil moisture, with the accuracy of soil moisture being higher considering soil lattice water. The average penetration depth was 19 cm in the oasis region and 36 cm in the desert region during the experiment. COSMIC model could be used to retrieve soil moisture by cosmic ray neutron in the desert-oasis regions, which had great potential to realize data assimilation of surface meteorological-hydrological-ecological variables by combining with land surface models.

Prediction model of water content in surface dead fuel based on convolution neural network and meteoro-logical factors regression

SUN Long, MA Linggan, GUO Yan, FAN Jiale, CHEN Boxuan, HU Tongxin

2023, 34(9):  2453-2461.  doi:10.13287/j.1001-9332.202309.024

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Water content of surface fuels is an important indicator of forest fire risk level and fire behavior, and the prediction model of which has a significant effect on fire risk prediction and management. Based on field meteorological factors of Quercus mongolica and Pinus sylvestris var. mongolica forests and water content data of dead fuels on the ground, we conducted the relative importance ranking of meteorological factors random forest and Pearson correlation analysis, and predicted water content of fuels using deeply learned convolutional neural network and meteorological factors regression. The results showed that water content of Q. mongolica fuels in the wild was significantly higher than that of P. sylvestris var. mongolica. The results of random forest showed that the factors that had significant effect on water content of fuel were humidity, temperature, rainfall, wind speed, and solar radiation, with the importance ranking from the largest to the smallest. Results of correlation analysis showed that temperature, humidity, and rainfall of current day had a significant impact on water content of fuels, and certain correlations were observed between meteorological factors. The prediction R² of the convolutional neural network model for the surface fuel water content of Q. mongolica and P. sylvestris var. mongolica forest was 0.928 and 0.905, the mean absolute error (MAE) was 6.1% and 8.1%, and the mean relative error (MRE) was 8.9% and 4.2%, respectively. However, the R², MAE, MRE of meteorological factors regression were 0.495 and 0.525, 30.5% and 39.5%, 52.1% and 32.6%, respectively. The precision of convolution neural network model was significantly higher than that of meteorological factors regression. Our results showed that the deeply learned convolutional neural network could provide some reference for the prediction of fuel water content in the future, and effectively support higher level forest fire management.

Regulation on air temperature by residential area morphology: A case study in Xuzhou City, China

ZHOU Hongxuan, WANG Wenzhen, YU Yuexin, SUN Jing

2023, 34(9):  2462-2470.  doi:10.13287/j.1001-9332.202309.022

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Due to woodlands and farmlands being replaced by residential areas in cities, continuous urbanization resulting in frequent urban heat island effects, especially in summer when high temperature seriously threaten health and lives of citizens. Although scientists realized that reasonable residential area morphology could effectively regulate air temperature and improve microclimate, it is lack of air temperature regulation-oriented specifications and requirements on morphology of residential areas. In this study, we used three types of morphological parameters of 15 residential areas in Xuzhou City and air temperature data via field investigation to analyze air temperature regulation caused by residential area morphology. The results showed that key morphological parameters of residential areas were different in morning and afternoon. In morning, independent effects of mean building height, street aspect ratio, and complete aspect ratio contributed 15.4%, 7.3%, and 6.8%, while those of building density, sky view factor, and the ratio of building surface area to floor area were 21.1%, 23.1%, and 6.9% in afternoon, respectively. Threshold values of efficiency of morphological parameters of residential areas were different between morning and afternoon. There were significant correlations between some morphological parameters of residential area. The results could provide data support and methodological reference for residential areas design in Xuzhou and surrounding cities.

Construction of ecological network based on habitat risks identifying by points of interest: A case study of Wuhan Metropolitan Area

HAO Mengyuan, LIU Dianfeng

2023, 34(9):  2471-2480.  doi:10.13287/j.1001-9332.202309.026

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Ecological network construction plays a key role in ecological restoration, which can effectively mitigate negative effects of habitat fragmentation on biodiversity. Here, we proposed an improved analytical framework for ecological network identification. Specifically, ecological sources were identified using a three-dimension indicator system in terms of form, quality and functions of habitats. Ecological resistance surfaces were determined based on the incorporation of points of interest data that could characterize human activities into habitat risk assessment (HRA) model, while ecological corridors were extracted using circuit theory approach. With Wuhan Metropolitan Area as a case, we explored the key points and structures of ecological network. Moreover, we compared the construction method of ecological resistance surface based on points of interest and HRA model with traditional methods that determined by land use types and by traditional HRA model, to validate the proposed framework. The results showed that the ecological source area of Wuhan Metropolitan Area was 15200 km², the length of ecological corridor was 1956.68 km, and that there were 87 ecological “pinch points” and 67 ecological barrier points. Compared with traditional methods, the material circulation, network complexity, and ecological connectivity of the ecological network identified by the improved framework were significantly improved, with network closure, dot-line ratio, and network connectivity being increased by 61.5%, 28.1% and 28.7% on average. The identified ecological “pinch points” and barrier points could provide precise decision-making support for ecological restoration and conservation.

Evaluation and optimization of ecological landscape pattern for urban agglomeration in the Pearl River Delta, China

XIE Zhuohong, LEI Min, LIU Lijie, MO Yanqing, ZHAN Guoqiang, LIU Ping

2023, 34(9):  2481-2488.  doi:10.13287/j.1001-9332.202309.025

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The evaluation and optimization of landscape ecological pattern has important implications for the accurate improvement of forest quality and high-quality urban development in the Pearl River Delta urban agglomeration. Based on the “one map” data and digital elevation model data of forest resource management in 2021, we evaluated and optimized landscape ecological pattern of the Pearl River Delta urban agglomeration by morphological spatial pattern analysis and minimum cumulative resistance model. The results showed that there were 435861 patches in the Pearl River Delta urban agglomeration that could be used as ecological source area, covering an area of 7346.60 km² and accounting for 13.4% of the Pearl River Delta area. Thirty patches were selected as the ecological source area of the study area by using the area and patch importance index, covering an area of 2792.59 km² and accounting for 5.1% of the Pearl River Delta area. The overall natural environment of the Pearl River Delta urban agglomeration was excellent. The ecological resistance level was small. The peripheral ecological resistance was low. The core ecological resistance was high. There was still a large room for adjustment of stand types and landscape patterns, which should be optimized by adjusting the composition and spatial distribution of tree species. The ecological network of the Pearl River Delta urban agglomeration was optimized with 30 ecological sources, 103 key ecological corridors, and 95 ecological nodes. The improvement rates of the optimized probability of connectivity index and integral index of connectivity index were 297.5% and 695.1%, respectively. The optimization results could effectively connect the ecological sources and spread the ecological service functions of ecological sources.

Construction of ecological security pattern in Ningbo based on remote sensing ecological index and graph theory knowledge

HUANG Junjie, FENG Xiuli, DONG Yuyi, ZHANG Chi, XIE Lijian, CHENG Junkai, GAO Tianyu

2023, 34(9):  2489-2497.  doi:10.13287/j.1001-9332.202309.027

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Constructing ecological security pattern and identifying ecological important areas are the focus of current research on regional ecological security. With Ningbo City as a case study area, we identified ecological sources by remote sensing ecological index, the ecological corridors and pinch point by circuit theory model, and the minimum spanning tree and cuts by graph theory algorithm. The results showed that there were 203 ecological sources in Ningbo, and that the main type of land cover was forest, including a small amount of paddy fields and flooded vegetation. There were 368 ecological corridors with a total length of 573.42 km, being dense in the southwest and sparse in the northeast. There were 91 ecological pinch points, which mainly distributed between coastal areas and closely related ecological sources. According to current situation, we put forward the optimization strategy with 187 primary corridors, 181 secondary corridors, 50 ecological restoration priority areas and 59 long-term ecological restoration areas. The optimization strategy combined with graph theory and circuit theory model would provide a refe-rence for the constructing of ecological security pattern.

Spatio-temporal variations of ecosystem service value and its spatial heterogeneity mechanism in the Dongjiang River Basin, China

YU Haixia, WANG Yuxiao

2023, 34(9):  2498-2506.  doi:10.13287/j.1001-9332.202309.020

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Comprehensive and deep research on the variations of ecosystem service value (ESV) based on land utilization/land cover change from a spatio-temporal perspective is of great significance for regional ecosystem optimization, as well as coordinated sustainable development of natural environment and economic society. Based on land utilization, natural environment, and socio-economic data of Dongjiang River Basin from 2010 to 2020, combined with hotspot analysis tools and local spatial autocorrelation analysis methods, we comprehensively analyzed the spatio-temporal variations of Dongjiang River Basin ESV, and further explored the spatial differentiation mechanism with geographic detector tools. The results showed that Dongjiang River Basin was dominated by forest ecosystem from 2010 to 2020. The construction land area had expanded significantly mainly from arable land and forest. The Dongjiang River Basin ESV showed a downward and then an upward trend. The ESV of arable land, forest and construction land continuously decreased, and the ESV of water decreased first and then increased substantially. The spatial distribution of ESV hot and cold spots had a significant agglomeration effect, presenting a pattern of hot spot dispersion in the upstream area and cold spots aggregation in the downstream area. The ESV distribution in the upstream and downstream area was not balanced, with the downstream area bearing greater ecological stress. According to the detection results of ESV spatial differentiation mechanism, land utilization was the main factor affecting the spatial differentiation, with the spatial difference of ESV (q value) reaching 0.462. The interaction of factors could greatly strengthen the spatial differentiation effect on Dongjiang River Basin ESV.

Multi-scenario optimization of land use structure and prediction of ecosystem service value in Guanzhong Plain urban agglomeration

QI Yuting, ZHANG Ping, LIU Lei, MA Xuenan, WANG Huan, ZHAO Juan

2023, 34(9):  2507-2517.  doi:10.13287/j.1001-9332.202309.009

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Rapid economic development has led to significant changes in land use in the Guanzhong Plain urban agglomeration, which alters regional ecosystem service value (ESV). Based on the land use and driver data of the Guanzhong Plain urban agglomeration, we used the system dynamics (SD) model coupled with the mixed-cell cellular automata (MCCA) model to predict the subtle spatial and temporal changes of ESV within the land use unit in 2040 under the scenarios of natural development, economic development, ecological protection, and arable land conservation, to reveal the responses of ESV to the socio-economic evolution. We examined the impacts of land use change on ESV by using the sensitivity index. The results showed that land use transformation between 2000 and 2020 in the study area was mainly the conversion between arable land, forest, grassland, and the conversion of arable land to construction land. Due to increased forest and water, ESV increased slightly during this period. In 2040, compared with the ecological protection scenario, the proportion of forest in the economic development scenario decreased by 1.8%, and the construction land increased by 1.3%. During 2020-2040, under the economic development scenario, ESV showed a downward trend in the central and eastern regions but an upward trend under the arable land conservation scenario, with hydrological and climatic regulation contributing the most to ESV. Total ESV showed a decreasing trend except for the ecological conservation scenario. In the ecological protection scenario, land use change positively impacted ESV. In contrast, ESV had a negative response to land use change in other scenarios, with the greatest reduction in the economic development scenario. The research could provide new methods for multi-scenario land use simulation and ESV prediction and have scientific and practical significance for optimizing land space layout, land resource planning management, and sustainable development path strategy of urban agglomerations.

Spatio-temporal variation of landscape pattern and the response of windbreak and sand fixation service in Hexi corridor of northern sand fixation belt

LIAN Hugang, QU Zhangming, LIU Chunfang, HE Yangxi

2023, 34(9):  2518-2526.  doi:10.13287/j.1001-9332.202309.035

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Landscape pattern, an important factor affecting the supply and maintenance of ecosystem services, is the basis for the healthy and stable regional ecosystem and the optimal decision of land use. Taking the Hexi Corridor in the northern sand fixation belt as the study area, we quantified and analyzed the temporal and spatial variations and response relationship between landscape pattern and windbreak and sand fixation services during 2000-2020 by using the software Fragstats 4.2, the revised wind erosion equation and the spatial autocorrelation method. The results showed that, the landscape pattern of land use types changed obviously in the study area during 2000-2020, mainly from Gobi to cultivated land and from grassland to cultivated land, and that the landscape pattern tended to be diversified, heterogeneous, and fragmented. The spatial pattern of windbreak and sand fixation services was generally characterized by “high in southeast and low in northwest”, with the amount of windbreak and sand fixation increasing at first and then decreasing. The windbreak and sand fixation capacity was higher in cultivated land and grassland and lower in the bare land and construction land. Shannon’s diversity index, patch density and landscape shape index were all positively correlated with windbreak and sand fixation services, while mean patch size was negatively correlated with it. Our results indicated that the increases of landscape heterogeneity, the more uniform distribution, the more patches and the more complex landscape shape had a promoting effect on windbreak and sand fixation services in the Hexi corridor of the northern sand fixation belt with Gobi Desert as the dominant landscape.

Carbon budget and evaluation of marine industry in Jiangsu Province, China

WANG Tong, CHUAI Xiaowei, XIANG Ai, GU Yunjuan, BIE Meng

2023, 34(9):  2527-2535.  doi:10.13287/j.1001-9332.202309.031

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The measurement and evaluation of carbon budget of marine industry is the basis for promoting green and efficient development of marine economy under the goal of carbon neutrality. We constructed a carbon accounting system for the marine industry in Jiangsu Province, and assessed carbon efficiency and neutrality. The results showed that from 2016 to 2020, the total amount of marine carbon sinks in Jiangsu Province were 894.8 to 2773.2 thousand tons, while carbon emissions of major marine industries were 3538.4 to 4350.6 thousand tons. The net emissions of marine industries ranged from 1478.7 to 2906.1 thousand tons. Both of carbon sinks and emissions were significantly increased in this period. In terms of carbon sinks, the offshore wind power accounted for the largest contribution, followed by ecosystem carbon sequestration, and mariculture carbon sequestration was the smallest. In terms of carbon emissions, the marine transportation industry played a dominant role, followed by coastal tourism and marine fisheries, while the marine engineering and construction industry and marine shipping industry accounted for a small proportion. In general, the carbon neutral status showed that marine industry in Jiangsu Province was in carbon deficit from 2016-2020, but the net emissions were decreasing year by year. The net carbon sink efficiency of mariculture in Jiangsu Province was lower than the national level, and carbon efficiency of offshore wind power was stable.

Effects of microplastics on seed germination and seedling physiological characteristics of Spinacia oleracea under alkali stress

GUO Linlin, WANG Jingjing, ZU Jingmei, WANG Pinsu, YANG Yujie

2023, 34(9):  2536-2544.  doi:10.13287/j.1001-9332.202309.032

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Microplastics, a type of new environmental pollutant, have received much attention for their negative effects on organisms and environment. We examined the effects of microplastics on seed germination and seedling physiological characteristics of spinach (Spinacia oleracea) under alkali stress, taking polystyrene microspheres with a diameter of 100 nm (200, 400, 800, 1600 mg·L^-1) as the microplastic treatment, and mixed NaHCO₃ and Na₂CO₃ as alkaline salt solution (5, 10, 20, 40 mmol·L^-1) according to the molar ratio of 1:1. The results showed that the presence of MPs (≥400 mg·L^-1) inhibited seed germination, and that the length of roots and shoots increased at low while decreased at high concentration of MPs. Different concentrations of alkali alone could inhibit seed germination, root and bud elongation. With the increases of MPs concentration, SOD activity of spinach seedlings gradually decreased, while POD activity firstly increased and then decreased, and chlorophyll content increased at low concentration (200 mg·L^-1) and decreased significantly at medium and high concentration (≥400 mg·L^-1). Different alkali stresses reduced chlorophyll content of spinach seedlings, and the effects on SOD and POD were ‘promotion at low concentration and inhibition at high’. In the treatments of microplastics (200, 800 mg·L^-1) and alkali (5, 20 mmol·L^-1) combined exposure, germination of spinach seeds was inhibited, and chlorophyll content decreased. The activities of SOD and POD in spinach seedlings were reduced under the combined exposure except the treatment of 200 mg·L^-1 MPs and 5 mmol·L^-1 alkali. Compared to the alkali stress, the combination of low concentration of MPs (200 mg·L^-1) and alkali could improve germination rate, germination index, germination vigor and vigor index of seeds, and significantly promoted the elongation of roots and shoots, while the addition of high concentration of MPs (800 mg·L^-1) reduced the germination rate, germination index, germination vigor and vigor index of seeds and inhibited the growth of roots and buds. The different concentrations of combined exposure inhibited the activities of SOD and POD and decreased the content of chlorophyll in spinach seedlings.

Spatio-temporal variation and environmental drivers of chlorophyll a concentration and diatom community in four small urban lakes of Kunming, China

TIAN Maoqi, CHEN Guangjie, KONG Lingyang, CHEN Li, LI Rui, WANG Lu, HAN Qiaohua, CHEN Xiaolin

2023, 34(9):  2545-2554.  doi:10.13287/j.1001-9332.202309.029

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Chlorophyll a (Chla) and diatom community structure are two indicators of lake water quality. In this study, we investigated the environmental parameters, chlorophyll a, and diatom community of four small urban lakes in Kunming (Beitan, Beihu, Nanhu and Longtan lakes in the campus of Yunnan Normal University) between March 2017 and December 2019. The results showed that the concentrations of total nitrogen (TN), total phosphorus (TP), and Chla in the four lakes showed significant seasonal fluctuation. The Chla concentration in Nanhu Lake, which had the highest nutrient level among the four lakes, was significantly higher than that in the other three lakes and largely affected by TN. In comparison, water temperature significantly contributed to the increases in Chla concentration in the other three lakes. Water temperature and TN were significantly correlated with Chla across the four lakes. Diatom assemblages in Beitan, Nanhu, and Longtan lakes were dominated by planktonic diatoms, and benthic diatoms were dominant in the shallowest lake Beihu, suggesting that water depth significantly affected the proportion of planktonic diatoms and dominant taxa. Water depth, TN, TP, transparency, and water temperature affected the spatio-temporal changes of diatom community structure, with water temperature as the major factor in causing the seasonal variation in diatom community, and TN and TP as the major drivers for community variation among lakes within the same season.

Characteristics of fish community structure and environmental driving factors in Taihu Lake during the first year of fishing ban

SHENG Piao, YANG Min, SHI Zhining, YANG Jianzhong, ZHANG Zhimin, YANG Xu, XIN Wei , ZHU Mingsheng, MEI Xiaole, CHEN Yushun

2023, 34(9):  2555-2565.  doi:10.13287/j.1001-9332.202309.030

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Taihu Lake has officially implemented the full fishing ban policy since October 1, 2020. We investigated fish community of Taihu Lake in the four seasons of 2020. A total of 42 fish species were collected, belonging to 6 orders, 7 families, and 33 genera. The first five dominant species ranked by the index of relative importance were Coilia nasus, Toxabramis swinhonis, Hypophthalmichthys molitrix, Hypophthalmichthys nobilis, and Salangichthys tangkahkeii. The number of C. nasus accounted for 85.1% of the total number of catches. According to the distributional characteristics of cyanobacterial blooms and aquatic plants, Taihu Lake could be divided into the northern, central, and eastern regions. There was no significant difference in catch per unit effort (CPUE) among different lake regions, but Shannon diversity index and Pielou evenness index in the eastern region was greater than in the other two regions. The CPUE, Shannon diversity index, and Pielou evenness index were significantly different among the four seasons, with the lowest CPUE in autumn and higher diversity in autumn and winter than in spring and summer. Electrical conductivity, water depth, chloride, and transparency were the main environmental factors driving the seasonal variations of fish community in Taihu Lake, while electrical conductivity, dissolved oxygen, total alkalinity, and transparency were key variables driving the spatial patterns. The results could be used as the baseline data for fish community studies in Taihu Lake after the fishing ban.

Construction of a multi-scale effectiveness evaluation system for ecological restoration and protection of territorial space

XIAO Wu, RUAN Linlin, YUE Wenze, ZHOU Yan, ZHANG Lijia, HU Yueming

2023, 34(9):  2566-2574.  doi:10.13287/j.1001-9332.202309.021

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The ecological restoration and protection of territorial space is a systematic project for the protection and restoration of ecosystems damaged or degraded by human disturbance. Effectiveness evaluation is of great significance to the optimization, adjustment, and sustainability of ecological restoration and protection. Current research and practices tend to focus on a single element and the site scale. Based on the study on the connotation of ecological restoration and protection of territorial space and the multi-scale characteristics of ecosystems, we constructed a multi-scale effectiveness evaluation system for ecological restoration and protection of territorial space and a full-cycle monitoring system for effectiveness evaluation. The multi-scale effectiveness evaluation system consisted of the regional/watershed scale, the protection and restoration unit scale, and the sub-project scale. The full-cycle monitoring system contained the basic information investigation system before construction, the construction monitoring system during construction, and the multi-scale effectiveness evaluation system after construction. At the regional/watershed scale, structure, quality, and services of ecosystem were concerned and remote sensing was used as the main method to capture data. At the protection and restoration unit scale, ecological stress factors, ecosystem quality and services were concerned, and the main methods were remote sensing combined with field survey. At the sub-project scale, engineering technology measures were concerned and the field survey was used as the main method. In the implementation of the multi-scale effectiveness evaluation, it would be necessary to focus on and solve the key issues including the spillover effect, transmission mechanism, and potential impact of ecological restoration.

Mechanism underlying temperature sensitivity of soil organic carbon decomposition: A review

CHEN Zhenxiong, ZHANG Chao, LI Quan, SONG Xinzhang, SHI Man

2023, 34(9):  2575-2584.  doi:10.13287/j.1001-9332.202309.017

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Temperature sensitivity (Q₁₀) of soil organic carbon (SOC) decomposition is an important index to estimate the dynamics of soil C budget. However, the spatial variation of Q₁₀ and its influencing factors remain largely uncertain. In this study, we reviewed the effects of climate environment, spatial geographic pattern, soil physicochemical property, vegetation type, microbial community composition and function, and global climate change on Q₁₀ to summarize the general rule of each factor influencing Q₁₀ and compare the relative contribution of each factor to Q₁₀ in different ecosystems. The results showed that Q₁₀ decreases with the increases of temperature and precipitation, but increases with the rise of latitude and altitude. The Q₁₀ value is higher in grassland than that in forest, and also in coniferous forest and deciduous forest than that in evergreen broad-leaved forest. Carbon quality is negatively correlated with Q₁₀, but the C quality hypothesis is not always valid with exogenous substrate input. For example, the increment of substrate availability may significantly increase Q₁₀ in low-quality soils. Q₁₀ decreases with the enhanced proportion of r-strategy microorganisms (Proteobacteria and Ascomycetes), but increases with the enhanced proportion of K-strategy microorganisms (Acidobacteria and Basidiomycetes). Q₁₀ increases with elevated CO₂ concentration, but declines with atmospheric nitrogen deposition. In natural ecosystems, Q₁₀ is mainly regulated by temperature and C quality. Temperature is the main factor regulating Q₁₀ in the topsoil while C quality is the main factor in deep soil. Our review provided a theoretical support to improve the coupled climate-C cycle model and achieved the C neutral strategy under global warming.

Research progress in biological control of tomato bacterial wilt

WU Sixuan, GAO Fuyun, ZHANG Ruipeng, SU Hao, YAO Huaiying, FAN Xuelian, LI Yaying

2023, 34(9):  2585-2592.  doi:10.13287/j.1001-9332.202309.028

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Bacterial wilt caused by the infection of Ralstonia solanacearum, is one of the most harmful diseases to tomatoes, one of the most important greenhouse vegetables in China. R. solanacearum can survive and remain active in the deep soil for a long time, and the chemical control of tomato bacterial wilt is consequently limited. In this study, we introduced the characteristics of tomato bacterial wilt disease and the types of R. solanacearum, and systematically reviewed the research progresses of biological control methods from the aspects of botanical insecticides, agricultural antibiotics, biocontrol bacteria. We emphatically introduced the principle and current status of these methods, discussed the limitations and the improvement strategies, and prospected a new environmental protection and efficient biological control system based on micro-ecological regulation would be the development direction of biological control of tomato bacterial wilt.