Table of Content

10 October 2022, Volume 41 Issue 10

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Effects of waterlogging stress on the growth and osmotic adjustment substances in the seedlings of forage mulberry.

LI Si-yuan, RAO Liang-yi

2022, 41(10):  1873-1880.  doi:10.13292/j.1000-4890.202209.019

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Morus alba has strong capacity of waterlogging tolerance. We examined the growth characteristics and ecophysiological responses of 4-year-old fodder-potted Morus alba seedlings under waterlogging stress. Plant height and the number of adventitious roots of M. alba seedlings were measured at regular intervals under four water conditions: control (CK), shallow waterlogging (QY), semi-waterlogging (BY), and deep waterlogging (SY). The changes of physiological indices of M. alba seedlings, including SPAD value, osmotic adjustment substances (soluble sugar, soluble protein, proline) and malondialdehyde (MDA) were analyzed at different waterlogging durations. The results showed that plant height of M. alba seedlings in the four treatments increased to different degrees in the waterlogging process. The increase of plant height in CK and QY was significantly higher than that in BY and SY during 20 to 60 days of waterlogging. After 10 days of waterlogging, a few adventitious roots began to appear at the base of the stem in each waterlogging group. At the end of waterlogging, the number of adventitious roots produced in BY was higher than that in SY. The SPAD value of leaves in waterlogging groups decreased signi ficantly after waterlogging. After 60 days of waterlogging, the SPAD value in QY, BY, and SY reached the minimum, with a reduction of 59.65%, 62.37% and 64.91% respectively. In the early stage of waterlogging, foliar soluble sugar contents in waterlogging groups increased significantly. With increasing waterlogging duration, foliar  soluble sugar content in waterlogging groups decreased, but still higher than that in CK. After 60 days of waterlog ging, there was no significant difference in soluble sugar content between QY and CK, but the content increased by 34.61% and 13.65% in BY and SY respectively. Waterlogging significantly increased foliar contents of soluble protein, proline, and MDA. After 60 days of waterlogging, the contents of the three substances in BY and SY were significantly higher than those in CK. Our results indicated that M. alba seedlings could adapt to waterlogging environment by forming adventitious roots and increasing the content of osmotic adjustment substances.





Relationship between leaf traits and photosynthetic efficiency of Ligustrum lucidum under Pb stress.

KONG You-sha, XU Hong-yang, HUANG Xin-hao, ZHU Fan

2022, 41(10):  1881-1886.  doi:10.13292/j.1000-4890.202209.021

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Leaf traits could reflect plant adaptation strategies to environmental changes. In this study, we measured photosynthetic efficiency and leaf traits of Ligustrum lucidum under Pb stress and analyzed their relationships, aiming to understand the adaptive strategies of L. lucidum to Pb stress. Two-year-old L. lucidum was treated with four Pb concentrations (0, 300, 600, 1800 mg·kg^-1, designated as CK, L1, L2 and L3, respectively). The results showed that net photosynthetic rate (P_n) was significantly reduced by 37.66%, 57.73%, and 77.47% under L1, L2, and L3 treatments, respectively. The maximum photochemical efficiency (F_v/F_m) of L. lucidum was only decreased significantly by 6.25% and 12.50% in L2 and L3, respectively. Specific leaf area (SLA), chlorophyll (Chl), chlorophyll a (Chla), chlorophyll b (Chlb), leaf phosphorus (TP), leaf nitrogen (TN), and nitrogen to phosphorus ratio (N/P) were significantly decreased. However, the intracellular CO₂ concentration (C_i) and carbon to nitrogen ratio (C/N) were significantly increased in Pb treatments. Carbon to phosphorus ratio (C/P) was significantly increased under L2 and L3 treatments. Stomatal conductance (G_s) and leaf thickness (LT) were significantly decreased under L3 treatment. SLA and Chl were significantly correlated with the leaf traits except LT. N/P was significantly correlated with the leaf traits except G_s and C_i. Results of structural equation modeling showed that gas exchange and Chl directly affected photosynthetic efficiency, while leaf phenotype and chemical elements had indirect effects. Principal component analysis verified the adaptability of the leaf economics spectrum in L. lucidum under Pb stress, which belonged to the end of slow investment return in the leaf economics spectrum.





Effects of foliar spraying alginate oligosaccharides on stress resistance and physiological characteristics of rice seedlings under salt stress.

LIU Ling, FENG Nai-jie, ZHENG Dian-feng, GAO Hong, HAN Zhen-hong, CHEN Guan-jie, MU De-wei

2022, 41(10):  1887-1894.  doi:10.13292/j.1000-4890.202209.013

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We examined the effects of alginate oligosaccharides (AOS) with 900 mg·L^-1 concentration under 0.3% NaCl salt stress on shoot growth, construction of root morphology, activities of antioxidases, antioxidant content, O₂^-_· production rate, osmotic adjustment substance and malondialdehyde (MDA) content in rice seedlings of salt sensitive cultivar IR29 and salt resistant cultivar FL478. The results showed that salt stress had negative impacts on the growth of seedlings of IR29 and FL478, and positive impacts on the O₂^-_· production rate and MDA contents in leaves. Under the stress conditions, foliar spraying AOS significantly promoted the growth of rice seedlings and increased stem diameter, leaf area of IR29 by 10.53% and 8.54%, respectively. Foliar spraying AOS significantly increased stem diameter, leaf area and shoot fresh weight of FL478 by 9.09%, 7.50% and 6.06%, respectively. Foliar spraying AOS significantly increased root length, root dry weight, root surface area, root volume and root tip number of IR29 by 18.98%, 23.33%, 18.29%, 14.15% and 15.15%, respectively; significantly increased root length and root dry weight of FL479 by 8.36% and 10.73%, respectively. Foliar spraying AOS significantly increased the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and phenylalanine ammonialyase (PAL) in leaves of IR29 by 10.79%, 21.31%, 22.21%, 23.66% and 15.39%, respectively; significantly increased the activities of ascorbate peroxidase (APX) of FL478 by 26.15%. Foliar spraying AOS significantly increased the content of ascorbic acid (ASA), glutathione (GSH), soluble protein and free proline (Pro) of IR29 by 33.88%, 13.51%, 5.54% and 20.52%; significantly increased the content of ascorbic acid (ASA), glutathione (GSH) and soluble protein of FL478 by 25.16%, 14.86% and 2.69%. Foliar spraying AOS significantly decreased MDA content of IR29 and FL478 by 8.14% and 17.17%, respectively. O₂^-_· production rate in the leaves of IR29 and FL478 reduced by 34.68% and 29.24%, respectively. Our results indicated that exogenous AOS spraying could enhance the resistance of rice seedlings to salt stress by improving the antioxidant and osmotic regulation capacity and removing a large amount of accumulated ROS to reduce membrane lipid peroxidation level.





Three endangered Pteridaceae species in China: Current population and conservation suggestion.

YUAN Quan, LIU Yong-bo, JIN Dong-mei, SONG Yi-gang, Morigengaowa, GU Yu-feng, DAI Xi-ling, YAN Yue-hong

2022, 41(10):  1895-1902.  doi:10.13292/j.1000-4890.202209.012

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Pteridaceae is the fourth fern family in China with respect to species richness, which contains 18 threatened species with various ecotypes including terrestrial, lithophytic and aquatic. Understanding the status of endangered Pteridaceae species with different ecotypes can provide useful information for the conservation of the endangered fern species. We investigated the location and size of natural populations of three endangered Pteridaceae species on the Chinese mainland: Adiantum nelumboiddes and Aleuritopteris grevilleoides, both terrestrial or lithophytic, and aquatic Ceratopteris pteridoides. We compared their climatic adaptability with 19 bioclimatic factors from WorldClim and found their dominant climatic factors. We simulated their potential distribution patterns using MaxEnt model under current climate scenario. Ad. nelumboiddes, is sensitive to the temperature annual range (bio7) and confined in the canyon of the Yangtze River from Zhongxian County to Wanzhou District of Chongqing City. Its natural population size is extremely small, with a total of about 500 individuals. Since it has high medical and economic values, the natural population has been under the pressure of serious human disturbance. Al. grevilleoides prefers warm winter (bio11) and low annual precipitation (bio12) and is found in Dayao County of Chuxiong Autonomous Prefecture and Luquan County of Kunming City in the north of Yunnan Province. The model simulation showed that Yuanmou, Yongren and Yongsheng in Yunnan Province which belonged to the dry warm valleys of the Jinsha River basin, were highly suitable areas for Al. grevilleoides. Population size of C. pteridoides was much larger than other two species, which is widely distributed in the shallow wetlands of the middle and lower reaches of the Yangtze River as well as the in the reed marsh at the lakeshore of Weishan Lake in Shandong Province. We proposed suggestions for the conservation of these three species.





Diversity and community structure of endophytic diazotroph isolated from Hongjiang Orange.

SUN Peng, WANG Li-yun, LU Dong-mei, YUAN Hong-xu

2022, 41(10):  1903-1908.  doi:10.13292/j.1000-4890.202209.023

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Endophytic diazotrophs isolated from Hongjiang Orange were identified by 16S rRNA sequence analysis. The biodiversity and distribution of endophytic diazotroph in Hongjiang Orange were revealed by Shannon diversity index (H), relative frequency (RF) and similarity index. The differences of the distribution of endophytic diazotroph between the healthy plants and the diseased plants infected by citrus yellow shoot disease were compared. The results showed that the genera of endophytic diazotroph of Hongjiang Orange were abundant. A total of 72 strains were isolated from different tissues of Hongjiang Orange, which belonged to 3 phyla, 4 classes, 5 orders, 8 families, 12 genera. Bacillus spp., Curtobacterium spp., Pantoea spp. and Burkholderia spp. were the dominant endophytic diazotroph of Hongjiang Orange, with relative frequency of 36.11%, 13.89%, 13.89% and 9.72%, respectively. The total Shannon diversity index (H) of endophytic diazotroph was 2.01, and the total evenness index was 0.62. The similarity index between different parts of Hongjiang Orange was C_s(root-stem)=0.29, C_s(stem-leaf)=0.40, C_s(root-leaf)=0.20, respectively, indicating a low similarity of endophytic diazotroph in different parts. There were 9 genera of endophytic diazotroph in leaf, 6 genera in root, and only 1 genus in stem. There was little difference in Shannon diversity index (H_health=1.87 vs. H_disease=1.91) and evenness index (E_health=0.67 vs. E_disease=0.72) between healthy plants and diseased plants, while the relative frequency of two dominant endophytic azotobacter Curtobacterium (RF_health=9.38% vs. RF_disease=17.5%) and Pantoea (RF_health=21.88% vs. RF_disease=7.5%) changed greatly.





Effects of nitrogen addition on carbon and nitrogen stoichiometry and homeostasis characteristics of Kandelia obovata plants soil microbial system.#br#

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YOU Hui-ming

2022, 41(10):  1909-1915.  doi:10.13292/j.1000-4890.202210.024

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In traditional mangrove forest management, the purification benefits of mangrove species were pursued unilaterally, but the concomitant effects of exogenous pollution on soil microbial interface were ignored. To examine the effects of N addition on C and N stoichiometry and homeostasis characteristics of plants soil microbes in the mangrove system, I carried out a greenhouse experiment using an automatic tidal-simulation device with five levels of N addition (0, 5, 10, 20, and 30 g N·m^-2·a^-1) and two sets of simulation systems, with and without mangrove plants. The results showed that medium and low N additions were beneficial to soil microbial biomass C and N, while high N addition inhibited soil microbial biomass. Nitrogen addition did not affect C and N stoichiometry of Kandelia obovata (P>0.05), but had significant effects on soil C content, microbial biomass C, microbial biomass N and microbial biomass C∶N (P<0.01). The presence of mangrove plants promoted soil microbial activity, and increased microbial biomass N by 11%-45%. There was a strong coupling relationship between soil nutrients, Kandelia obovata roots, and soil microorganisms. The stoichiometric homeostasis of C and N in aboveground biomass of plants showed absolutely steady state under N addition. Soil microbial biomass C, N, and root C∶N were sensitive to the changes of soil nutrients. With increasing N addition level, soil C∶N ratio decreased. The increased N addition level will accelerate the decomposition of soil organic matter, leading to higher soil carbon emission.





Effects of litter inputs on soil nitrogen mineralization in a natural Castanopsis carlesii forest.

ZHANG Jin-xin, TU Feng-lan, XU En-lan, ZHANG Lei, GUO Jian-fen

2022, 41(10):  1916-1922.  doi:10.13292/j.1000-4890.202210.011

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As an important source of soil nitrogen (N), litter inputs play a key role in soil N cycling. The present study was conducted to explore the effects of litter inputs (viz. no litter, double litter, normal litter input) on soil nitrogen mineralization in a natural Castanopsis carlesii forest in mid-subtropical China. The differences in potential soil net N mineralization under different treatments and the main influencing factors were investigated through laboratory incubation experiments. The results showed that: (1) Soil net ammoniation rates under different litter inputs were negative, and litter input did not affect soil net ammoniation and nitrification rates. Soil net N mineralization rate increased with increasing litter input quantity, with that under double litter input being significantly higher than that of no litter input. (2) Litter removal significantly decreased the concentrations of total N and soluble organic N in soil, while soil microbial biomass N (MBN) under double litter treatment was significantly higher than that under normal litter input treatment. There was no significant difference in the concentrations of NO₃^--N and NH₄⁺-N among different treatments. (3) Increasing litter inputs significantly increased soil β-N-acetylglucosaminidase (NAG) activity, which was 2.6 times higher under double litter input treatment than under normal litter input treatment, but there was no significant difference in soil leucine aminopeptidase activity among different treatments. (4) Soil N mineralization under different treatments was mainly affected by soil NAG activity, MBN, and NO₃^--N contents. Thus, under global environmental change, increased forest litter inputs in subtropical forests can provide sufficient nutrients for soil microorganisms. The turnover rate of soil N was enhanced by the promotion of NAG activity, which then increased soil N supply capacity.





The key microbial functional gene of soil nitrogen transformation in different degradation stages of Gahai wetland.

LONG Yong-chun, MA Wei-wei, SONG Liang-cui, TANG Yan-mei, XU Guo-rong, CHANG Wen-hua

2022, 41(10):  1923-1931.  doi:10.13292/j.1000-4890.202208.002

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Clarifying the effects of wetland degradation on nitrogen-transforming gene abundance of soil microorganisms provides an important basis for understanding wetland degradation mechanism and scientific management of degraded alpine wetlands. We detected the gene abundance of nitrogen-fixing bacteria (nifH), ammonia oxidizing archaea (AOA amoA), ammonia oxidizing bacteria (AOB amoA) and denitrifying bacteria (nirK) in Gahai wetland soils under four different degrees of degradation (non-degraded, lightly degraded, moderately degraded and severely degraded), by real-time fluorescent quantitative PCR technology. We further analyzed the characteristics of functional gene abundances under different degradation stages. The results showed that the abundances of the four functional genes were significantly higher in the 0-10 cm soil layer than that in the 10-20 cm soil layer. The gene abundance of nifH, AOA, AOB and nirK ranged 10⁶-10⁸, 10⁷-10⁸, 10⁵-10⁶ and 10⁷-10⁸ copies·g^-1 soil, respectively, while the abundance of AOA was significantly higher than that of AOB. The abundances of the four genes peaked in the lightly degraded stage, and significantly decreased in the moderately and severely degraded stages. The interpretation rates of soil physical and chemical properties for the variations of soil microbial functional genes were 87.9% and 91.2%, respectively, with the key drivers differing in different months. Soil water content was the key factor affecting gene abundance in June, while nitrogen content was the key factor driving the variations of gene abundance in August.





Effects of freeze-thaw on soil CO₂ flux in different terrestrial ecosystems: A meta-analysis.

2022, 41(10):  1932-1939.  doi:10.13292/j.1000-4890.202209.022

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Freeze-thaw is a natural phenomenon at high elevation and high latitude, as well as some temperate regions. Many studies have shown that soil carbon dioxide (CO₂) emission flux is strongly influenced by freeze-thaw, indicating that soil CO₂ emission during freeze-thaw period is non-negligible in annual CO₂ emission. To better understanding the variations of CO₂ emission among terrestrial ecosystems during the freeze-thaw period, the effects of freezing temperature and freeze-thaw cycles on farmland, forest, wetland and grassland ecosystems were analyzed by collecting data from 37 papers published from 1990 to 2020. Compared to non-freeze-thaw treatment in the field condition, soil CO₂ emission under weak freeze-thaw treatment on farmland, forest, and grassland were increased by 44.2%, 25.5% and 56.0%, respectively, and was decreased by 10.1% in wetlands; while soil CO₂ emissions of four types of ecosystems under medium and strong freeze-thaw conditions were inhibited. In the laboratory condition, soil CO₂ emissions of the four ecosystems were promoted, with an average increase of 46.3%-272.5% under different freeze-thaw intensities, except for grassland ecosystem under the medium freeze-thaw condition. The peak value of soil CO₂ emission appeared at the early stage of freeze-thaw. After that, soil CO₂ emission rate gradually decreased to a stable level with increasing frequency of freeze-thaw cycles. This study helps to better understand the responses of soil CO₂ emissions from different ecosystems to freeze-thaw conditions and lays a foundation for further research.





Effect of water table restoration on soil enzyme activities in drained peatland.

WANG Yu-ting, XU Zhi-wei, SUN De-jing, XIN Mu-rong, GAO Chang, WANG Yi-xiao, DONG Yan-min, WANG Sheng-zhong

2022, 41(10):  1940-1947.  doi:10.13292/j.1000-4890.202209.004

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Hydrological condition is important for the restoration of drained peatland by affecting both plants and microorganisms. Soil enzymes released by microorganisms are strongly associated with the decomposition of soil organic matter. It is therefore important to understand the impacts of hydrological condition on soil enzyme activities. To reveal the variation patterns of soil enzymes during water table restoration and also the triggers of these variations, soil samples (0-50 cm) were collected from a natural, a drained, and two rewetted areas of the Baijianghe peatland in June 2020. We measured soil physical and chemical properties and the activities of two oxidases (peroxidase and polyphenol oxidase) and three hydrolases (β-1,4-glucosidase, β-1,4-N-acetylglucosaminidase and acid phosphatase). The results showed that the activities of both peroxidase and polyphenol oxidase in 0-50 cm soils from the rewetted areas were significantly lower than those from the drained area. In terms of hydrolases, the activities of both β-1,4-glucosidase and β-1,4-N-acetylglucosaminidase in 0-10 cm soils from the rewetted areas were significantly lower than those from the drained area. Soil enzyme activities in the natural area was mainly affected by soil water content, but mainly affected by soil pH and the contents of total nitrogen and phosphorus in the drained area. Both soil nutrients and water content affected soil enzymes in rewetted areas. Our results indicated that soil enzyme activities were controlled by different factors under different water tables and that the effect of water table on soil enzyme activities was largely dependent on soil depth.





Characteristics of organic carbon δ¹³C of different sized soil particulates in the southern slope of Qilian Mountains.

HAN Guang-zhao, CAO Guang-chao, CAO Sheng-kui, YE Wen-qian

2022, 41(10):  1948-1954.  doi:10.13292/j.1000-4890.202210.002

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To clarify the decomposition characteristics and stability of soil particulate organic carbon in different vegetation types in alpine region, we analyzed soil particulate composition, soil particulate organic carbon content, and organic carbon isotope (δ¹³C) of different sized particulates of different vegetation types in alpine meadow, shrub, forest and farmland in a southern slope of Qilian Mountains. The results showed that sand content was the highest particulate composition in soils, ranging from 58.3% to 78.2%, followed by silt content, ranging from 20.2% to 32.2%, and the clay content was the lowest, ranging from 1.6% to 6.3%, across different vegetation types. The organic carbon content of soil particulates increased with the increases of particulate size. The organic carbon content was from 21.6 to 74.5 g·kg^-1 for sand particulates, between 64.8 and 163.9 g·kg^-1 in silt particulates, and ranged from 60.3 to 196.4 g·kg^-1 in clays. With decreasing soil particulate size, the δ¹³C values increased gradually, ranging from -27.5‰ to -23.8‰. Those results indicate that the degree of decomposition of organic matter becomes higher, and the rate of decomposition becomes slower as the soil particulate size becomes smaller. The particulate organic carbon content of silt and clay is high, with low decomposition rate. These two kinds of particulates are important factors affecting the stability of organic carbon pools.





Community structure of metazooplankton and its relationship with environmental factors in the Liujiaxia Reservoir.

DU Yan-yan, YANG Zhuo-yu, YANG Shun-wen, SU Zi-jun, SHI Xiao-ning, WANG Tai

2022, 41(10):  1955-1961.  doi:10.13292/j.1000-4890.202209.020

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We investigated metazooplankton community structure and water environmental factors in Liujiaxia Reservoir from March to October 2020. Metazooplankton community structure and its relationships with environmental factors were analyzed by redundancy analysis, aiming to provide reference for water protection and sustainable utilization of fisheries in Liujiaxia Reservoir. A total of 24 species of zooplankton were identified, including 12 species of rotifers, 7 species of cladocerans, and 5 species of copepods. There were 16 species of zooplankton in summer and 11 species in spring. The dominant species were Keratella cochlearis, Polyarthra trigla, Asplanchna priodonta, Daphnia longispina, Daphnia cucullata, Bosmina longirostris, Sinocalanus dorrii and nauplius, with seasonal variations. The density of zooplankton varied from 8 to 116 ind·L^-1, with an average density of 31 ind·L^-1. The biomass of zooplankton varied from 0.056 to 0.606 mg·L^-1, and the average biomass was 0.280 mg·L^-1. The Shannon index, Margalef richness index, and Pielou evenness index were 0.77-1.87 (1.55 on average), 1.90-3.07 (2.56), and 0.20-0.55 (0.44), respectively. The lowest values of all the three diversity indices were found in September. Results of redundancy analysis showed that environmental factors such as water temperature, transparency and nitrate content were significantly related to zooplankton community structure. Water body of Liujiaxia Reservoir was at an oligotrophic level, which accords with the China’s national class II water quality standards.





Effects of embryonic and newly hatched larval development temperatures on thermal adaptability of zebrafish larvae.

ZHENG Xue-li, HUANG Yan, FU Shi-jian, XIA Ji-gang

2022, 41(10):  1962-1968.  doi:10.13292/j.1000-4890.202209.016

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Developmental plasticity is a key factor driving the evolution and diversification of new traits. Under the context of climate change, exploring the developmental plasticity of fish thermal adaptation is helpful for understanding the evolution of fish thermal adaptation phenotype in the early stage of their life history. To examine the effects of embryonic and newly hatched larval development temperatures on thermal adaptability of fish, we carried out an experiment following factorial design, in which both embryos and newly hatched larvae were reared in a low (22 ℃) or a high (28 ℃) temperature. Zebrafish (Danio rerio), a small oviparous fish, was used an animal model. The effects of incubation temperature of embryos and development of newly hatched larvae and their interactions on thermal adaptation phenotypes, including preferred temperature, avoidance temperature (including cold avoidance temperature and heat avoidance temperature), non-avoidable temperature range, and thermal tolerance (including critical thermal minima, critical thermal maxima, lethal thermal minima and lethal thermal maxima) of zebrafish larvae were investigated. The results showed that both incubation temperature of embryos and development of newly hatched larvae had a significant impact on the preferred temperature, avoidance temperature, and thermal tolerance (P<0.05). Moreover, the interaction of embryonic and newly hatched larval development temperature had a significant impact on non-avoidable temperature range (P<0.05). The results suggest that the thermal environment of embryo incubation plays an important role in shaping the thermal adaptation phenotypes of zebrafish in the early stage of life history. The variations of developmental temperature may expand the suitable temperature range of fish, and thus improve their viability under the scenarios of climate change.





Effects of microplastics on growth and liver antioxidant system of Lates calcarifer.

XIE Mu-jiao, XU Peng, ZHOU Wei-guo, DING De-wen, SUO An-ning

2022, 41(10):  1969-1976.  doi:10.13292/j.1000-4890.202210.013

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To evaluate the effects of microplastics on marine fish, we exposed juvenile Lates calcarifer (initial weight 8-12 g, body length 7-10 cm) in polyethylene  and biodegradable  microplastics (3 mm long × 3 mm wide) at an environmental relevant concentration (0.375 n·L^-1) to diet for 45 days. Liver antioxidant enzyme activities and the expression of genes involving in key pathway were measured after microplastics exposure for 30 and 45 days, respectively. The results showed that both types of microplastics could be ingested by fish but did not influence body weight and body length. Antioxidant enzyme activity showed limited responses to microplastics, and only catalase (CAT) decreased significantly in PE group compared after 45 days exposure. After 30 days exposure, all the relative expressions of kelch-like epichlorohydrinassociated protein 1 (Keap1), nuclear factor-E2-related factor 2 (Nrf2), gluthione S-transferase1 (GST1) and heme oxygenase 1 (HO1) increased in both exposure groups but the differences were not statistically significant. There were no significant differences in biological effects between two types of microplastics. Those results indicated that the exposure to microplastics at environmental relevant concentration did not affect the growth and did not cause obvious antioxidant response of juvenile L. calcarifer. Biodegradable microplastics can be ingested by fish and will not be degraded in the short term. If biodegradable microplastics accumulate in the marine environment, they may negatively affect fish in the long term. The current results underlined the need to assess the long-term impacts of biodegradable and conventional microplastics on marine fish.





Apparent toxicity of synthesized silver nanocubes induced by NaCl to Chlorella vulgaris.

DENG Ning-can, LI Hai-bo, LI Ying-hua, LI Zhe, WANG Ming-shuai, MO Fan, ZHANG Chen-xi, XU Jia-ning, WANG Li-xin

2022, 41(10):  1977-1983.  doi:10.13292/j.1000-4890.202208.001

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To explore the preparation method of cubic AgNPs and its toxic effect on aquatic organisms, silver nanocubes were synthesized by liquid reduction method through the reduction of silver nitrate with NaBH₄ (sodium borohydride) in the presence of PVP (polyvinyl pyrrolidone) and NaCl (sodium chloride). We examined its exposure toxicity on Chlorella vulgaris under the conditions of AgNPs colloidal solution concentrations of 0, 0.5, 1, 2 and 5 mg·L^-1 cubic AgNPs. Results showed that the concentration of NaCl and NaBH₄ solution had great influence on the morphology and size of AgNPs particles. When the concentration of NaCl and NaBH₄solution was 0.5 mol·L^-1, the morphology of silver nanocubes was the most regular, and their size was within a range of 200-300 nm. The cell densities and chlorophyll were markedly decreased, with a dose-effect. The content of reactive oxygen species (ROS) and superoxide dismutase (SOD) in treatment groups increased significantly after 48 h exposure. Obviously damaged cell morphology in C. vulgaris caused by cubic AgNPs was observed by TEM, suggesting that cubic AgNPs had toxic effect on C. vulgaris. Our results revealed the potential risks of AgNPs in aquatic environment.





Coupling effects of nitrogen limitation and ultraviolet radiation on photosynthetic performance of Thalassiosira pseudonana.

LIU Jing-hua, WANG Yi-fei, ZANG Sha-sha, YAN Fang, XU Zhi-guang, WANG Lei, WU Hong-yan

2022, 41(10):  1984-1990.  doi:10.13292/j.1000-4890.202210.014

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In this study, we examined the photosynthetic response of diatom Thalassiosira pseudonana to UV radiation under different nitrogen concentrations. Results showed that the maximum photochemical yield (F_v/F_m) of PSII was significantly inhibited by UV radiation, which was aggravated by nitrogen limitation. Under nitrogen limitation, the net closing rate of the reaction center (M_o) increased, the electron transfer efficiency from Q_A^- to Q_B (ψ_o) decreased, the absorption efficiency of light energy (α) was depressed, which together reduced the tolerance of T. pseudonana cells to UV radiation. UV radiation, especially when under nitrogen limitation, significantly decreased the ratio of PSII repair rate to damage rate (r/k), indicating that the photoinhibition of PSII was intensified by UV radiation through the damage of repair process. Our results suggest that the combination of nitrogen limitation and UV radiation could decrease photosynthetic capacity of T. pseudonana, with consequences on the primary production.





The potential suitable areas and key climatic impacting factors of medicinal plant Excoecaria acerifolia Didr.

WANG Zhi-wei

2022, 41(10):  1991-1997.  doi:10.13292/j.1000-4890.202208.018

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Based on the information of 82 geographical distribution locations of Excoecaria acerifolia Didr. in river valleys of Southwest China and 67 climatic factors, I analyzed the potential suitable areas and key climatic factors of E. acerifolia using Maximum Entropy (MaxEnt) and ArcGIS. The results showed that the potential suitable areas of E. acerifolia are mainly located in river basins of the eastern Himalayas, Hengduan Mountains, and Sichuan Basin of Southwest China, with the river basins of Hengduan Mountains in Yunnan and Sichuan Provinces as the core distribution areas. Precipitation of April, temperature annual range, temperature seasonality, minimum temperature of January, and maximum temperature of December are the key climatic factors affecting the potential distribution of E. acerifolia. Among those factors, precipitation of April is particularly critical, with a contribution rate of 42.29%. When the probability of presence of E. acerifolia is higher than 0.5, the ranges of the above five factors are: 49-95 mm, 23-28 ℃, 450-700, -5-5 ℃ and 7.5-13 ℃, respectively. Our results are basically  consistent with the distribution records of E. acerifolia, and can offer certain basis for the investigation and protection of germplasm resources, development and utilization of medicinal plants in the dry hot/warm river valleys, a special habitat of Southwest China.





Impacts of climate change on the climatic division for litchi planting in Guangdong Province, China.

DU Xiao-yang, ZHANG Liu-hong, DENG Yu-jiao

2022, 41(10):  1998-2007.  doi:10.13292/j.1000-4890.202210.025

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Based on the dataset of air temperature and precipitation from 86 stations during 1961 to 2021 and DEM data derived from 1:250000 topographic maps, we analyzed the spatial-temporal variations of key climate factors such as annual mean temperature (T_y), annual extreme minimum temperature (T_min), cold accumulation of average daily temperature ≤10 ℃ from previous December to February (∑(10-t)_12-2), average precipitation in March (R₃) using the methods of linear regression, accumulative anomaly, and inverse distance weighted interpolation. We examined the impacts of climate change on climatic division for litchi planting by combining the changes of four key climate factors for the periods of 1961-1990, 1971-2000, 1981-2010, 1991-2020, before (1961-1997) and after T_y mutation (1998-2021). The results showed that spatial distributions of the four key climate factors for litchi planting varied across different places in Guangdong. Generally, T_y and T_min were higher in south parts than that in north parts and higher in plain than that in mountain regions. ∑(10-t)_12-2 was higher in north parts than that in south parts and higher in mountain than that in plain regions. R₃ increased from southwest to northeast. Under the background of global warming, T_y and T_min showed a significant increasing trend with a rate of 0.2 ℃ and 0.4 ℃ per decade, respectively, whereas R₃ showed an insignificant upward trend and ∑(10-t)_12-2 even showed significant drop with a rate of 14.0 ℃·d per decade. T_y had mutation in 1997. According to the climatic conditions of litchi growth and development, the climatic division for litchi planting could be divided into three regions in Guangdong: suitable region, sub-suitable region, and unsuitable region. The suitable region was mainly distributed in the east of Guangdong, the coast of Pearl River Delta, and the north part of western Guangdong. The sub-suitable region was mainly located in Zhanjiang, Yunfu, and the northern Pearl River Delta. The unsuitable region was concentrated in northern Guangdong, northern Zhaoqing, and the Yunwu Mountains. Due to the climate change, the areas of suitable and sub-suitable regions increased, whereas the area of unsuitable region decreased. Relative to that in 1961-1990, the areas of suitable and sub-suitable regions in 1991-2020 increased by 0.44×10⁶hm² and 1.02×10⁶ hm², respectively, while the area of unsuitable region decreased by 8.09×10⁶ hm². The areas of suitable and sub-suitable regions increased by 0.08×10⁶ and 2.01×10⁶ hm², respectively, while the area of unsuitable region decreased by 2.08×10⁶ hm² after climate mutation (1998-2021) compared to that before climate mutation (1961-1997) in Guangdong.





Prediction of potential suitable regions of tea green leafhopper in China in the context of climate change.

JIANG Ming-xin, ZHONG Wen-yu, HU Hai-qin, ZHENG Zhi-qiang, CHEN Yan-ting, YOU Min-sheng, CHEN Li-lin

2022, 41(10):  2008-2016.  doi:10.13292/j.1000-4890.202209.014

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Based on the current 308 sites of tea green leafhopper (Empoasca onukii Matsuda) recorded in China and 7 environmental variables, a maximum entropy model (MaxEnt) was used to predict the current and future (2050 and 2070) potential distributions and its suitable degree under two climate scenarios (SSP2_45 and SSP5_85). The area under curve (AUC) value was 0.904, indicating that the accuracy of the model was good and the outcomes were reliable. The main environmental variables estimated by the Jackknife method were the lowest temperature in the coldest month (bio6), the mean monthly temperature difference between day and night (bio2), the precipitation in the driest month (bio14), and the precipitation in the wettest season (bio16). Currently, the highly suitable regions of tea green leafhopper were mainly concentrated in Zhejiang, Fujian, Jiangxi, Hunan, Guizhou, Chongqing, and Hainan. Under future climate scenarios, the potentially suitable regions would be expanding and move northward. The suitable region is the largest under the SSP5_85 climate scenario in 2070, with a 21.1% increase compared to the current suitable area. Given the wide distribution of tea green leafhopper in most regions of China, accurate predictions of its distribution are vital, and timely control measures should be taken to protect the high-quality production of tea.





Evaluation of cool island demand and spatial differentiation in Fujian Delta urban agglomeration.

SHEN Zhong-jian, LIANG Chen

2022, 41(10):  2017-2025.  doi:10.13292/j.1000-4890.202209.015

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Greenspace and water could mitigate the urban heat island effect through their cooling island effect. Evaluation of greenspace and water cool island demand is of great significance to optimizing spatial distribution of greenspace and water. We integrated Landsat remote sensing images, NPP/VIIRS nighttime light data, GDP and population density data of Fujian Delta urban agglomeration in 2017, and constructed an evaluation index system of cool island demand based on three dimensions, including heat island stress degree, land vulnerability degree, and social sensitivity degree. Further, we examined the spatial distribution and heterogeneity of cool island demand degree, and identified demand area and dominant factor types. The results showed that heat island stress degree, land vulnerability degree, and social sensitivity degree in Fujian Delta urban agglomeration had a significant spatial autocorrelation in 2017, with positive correlations among the three parameters. The high demand area and sub-high demand area for cool island were 2820.02 and 2078.31 km², respectively. Cool island demand degree had a significant positive correlation in space, and its spatial pattern was closely related with geographical location and terrain. The high value area was in urban areas along the east coast, and the low value area was in the western inland areas with high elevations. The results of dominant factor partitioning showed that comprehensive dominated area was concentrated in the urban center area, social sensitivity dominated area was mainly located in urban edge area, heat island stress dominated area was mainly bare land and part of industry zone, and land vulnerability dominated area was located in sparse vegetation cultivated land far from the urban areas. This study can provide insight into cool   island  demand and spatial pattern optimization of greenspace and water.





Evaluation of human disturbance in nature reserves of Guangdong based on multi-source data.

WANG Hai-yun, KUANG Yao-qiu, WEN Xin-jian, LIN Xiao-bo, HE Ye-yu, CHEN Ze-feng

2022, 41(10):  2026-2034.  doi:10.13292/j.1000-4890.202209.024

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Human activities threaten the rare and endangered wildlife in nature reserves. Satellite remote sensing technology has advantages of high accuracy and objectivity in monitoring human activities in nature reserves. Tencent is the largest messaging and social media platform in China, with broad coverage. Tencent user density (TUD) dataset is thus a useful proxy of dynamic population distribution with the advantages of real-time and efficient. In this study, we identified the artificially disturbed landscapes in the national and provincial nature reserves in Guangdong Province in 2015 and 2019 based on the high-resolution remote sensing images. We quantitatively evaluated the spatiotemporal variations of the artificially disturbed landscapes in the nature reserves using a disturbance intensity index. We further used TUD data for comparison and verification. The results showed that: (1) The intensity of human disturbance in the nature reserves was not high in general. The spatial distribution was uneven, with a high intensity in the northeast and a low intensity in the southwest. (2) From 2015 to 2019, the disturbance index of human decreased by 81.8%. The intensity of human disturbance was relatively strong in the areas with good geographical conditions in terrain and traffic. The higher the proportion of basic farmland and population density, the greater the intensity was. (3) The evaluation results of human disturbance intensity were consistent with the TUD data. The higher the human disturbance intensity, the higher the TUD was. Nature reserves in urban areas and with tourism development had higher TUD.





Spatiotemporal distribution characteristics of air pollutants in urban street canyons as observed by mobile monitoring.

CUI Ai-wei, MIAO Chun-ping, HE Huan, XIONG Zai-ping, HU Yuan-man, CHEN Wei

2022, 41(10):  2035-2042.  doi:10.13292/j.1000-4890.202209.006

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To explore the variation of air pollutant concentration and the influence of meteorological factors on air pollutant concentration in urban street canyon, we used portable air pollution monitoring equipment to detect five kinds of air pollutants (CO, SO₂, PM₁, PM_2.5, and PM₁₀) in the Qingnian Street of Shenyang during the peak and off peak periods under clean weather and polluted weather. Pearson correlation analysis was used to assess the influence of meteorological factors on the mass concentrations of five air pollutants. The results showed that the distribution of air quality index (AQI) in the Qingnian Street had significant spatial and temporal variations over short-term. The spatial distribution of AQI showed a pattern of “high in the north and low in the south” under clean weather, and a pattern of “high in the south and low in the north” under polluted weather, with high pollutant concentration at road intersections. Temporally, the concentrations of the five pollutants were higher under polluted weather than that under clean weather. They were the highest in peak commuting time and the lowest in off peak commuting time. The concentrations of air pollutants were significantly positively correlated with air temperature and relative humidity, and negatively correlated with air pressure in clean weather. In polluted weather, air temperature was negatively correlated with PM₁; relative humidity was negatively correlated with SO₂ and CO concentrations, positively correlated with PM_2.5 and PM₁₀ concentrations; and pressure was negatively correlated with CO, SO₂, PM₁ and PM_2.5 concentrations. This study provided a reference for future studies on air pollution control and regional air pollutant transport in street canyons.





Research progress on fire adaptations and responses of Quercus forests.

ZHANG Wen-wen, WANG Jin, WANG Qiu-hua, ZHANG Xi-yan, LONG Teng-teng, CAO Heng-mao

2022, 41(10):  2043-2049.  doi:10.13292/j.1000-4890.202208.012

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Due to the influence of human activities and increasing frequency of extreme weather events, forest fires continue to occur frequently, and fire patterns (e.g., season, frequency and intensity, etc.) change accordingly. Although fires with different frequencies and intensities occurred in Quercus forests, most Quercus species have evolved the ability to survive after periodic fires. It is necessary to elucidate the responses of Quercus to forest fires and reveal their adaptive strategies. In this review, we introduced the characteristics and flammability of Quercus forests, natural renewal of Quercus forests, the adaptations and responses of individuals and populations to fire disturbance, and discussed the adaptations and responses of Quercus forests to fire. We then analyzed the problems in current research, and put forward the future research direction. The results can provide scientific basis for the selection of tree species for ecological restoration, the selection of fire resistant tree species, and the construction of biological fireresistant forest belt, which is conducive to the suitable afforestation and management of Quercus forest in China, especially for the selection of Quercus species with strong fire resistance in areas with frequent fires. Meanwhile, the results can help improve the efficiency of Quercus forest management, so that the goal of a comprehensive utilization of Quercus could be achieved, with their ecological, economic and social benefits being fully explored.





Research progress in chemical communication of the decapod crustaceans.

ZHOU Zi-hao, WU Hong-ying, HUANG Jin-long, WU Zheng-jun

2022, 41(10):  2050-2057.  doi:10.13292/j.1000-4890.202210.016

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Chemical communication plays an important role in the survival and reproduction of most animals. Some species can perceive internal and external environment changes through chemical communication and then react in favor of them. For most decapod crustaceans, chemosensory is the dominant sensory pathway. Antenna and antennule are the most important sensory organs of decapod crustaceans. The recognition of chemical signal molecules in the environment is of great significance to avoiding predators, mating, and reproduction. Different positions of antenna and antennule mediate different pathways and assist the organisms to make more accurate and effective judgments when responding to different signals. With the development of molecular technology, more olfactory receptors and chemoreceptors have been found. They are the basis of receiving and transmitting the information. Different receptors perform different functions and are sensitive to different substances. Exploring the structure and function of receptors will better reveal the mechanisms of chemical communication of decapod crustaceans. In this review, we summarized the mechanisms of chemical communication. After receiving chemical signals, chemosensory organs produce physiological and behavioral changes through different conduction pathways. We also summarized the main types and functions of pheromone in decapod crustaceans, including sex pheromone, alarm pheromone, and larval release pheromone. The purpose of this paper is to provide the theoretical references for research on decapod crustaceans.





Multidimensional exploration in the study of urban bird diversity: A review.

WANG Qian, LIU Zhi-cun, LIU Tian-yu, WAN Dong-mei, JIANG Yi-ting

2022, 41(10):  2058-2063.  doi:10.13292/j.1000-4890.202210.004

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Urbanization across the world has results in many ecological problems, among which is the rapid loss of species diversity. Birds are one of the taxa most affected by urbanization. For instance, urbanization significantly reduces bird diversity and changes species composition of bird communities. Human-dominated urban ecosystems have replaced native habitats. Urban infrastructure, vegetation, and human activities have greatly changed the urban environment. Here, we summarize research progress on urban avian diversity from three perspectives: urban landscape, urban greenspace habitat heterogeneity, and human disturbance. In addition, we introduce several novel diversity indices and three different dimensions to explore avian diversity in urban ecosystems. We propose specific measures to protect avian diversity during urbanization, such as enhancing patch connectivity, increasing green spaceheterogeneity, and increasing buffer zones. We put forward five suggestions for in-depth research on urban avian diversity in China.





Ecological security evaluation of plateau urban wetland based on DPSIRM model: With Xining section of Huangshui Basin as an example.

XIANG Li, ZHOU Wei, REN Jun, HUANG Yu-han, GUAN Yan-jun

2022, 41(10):  2064-2071.  doi:10.13292/j.1000-4890.202209.003

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As a special ecosystem in plateau cities, urban wetland plays an important role in maintaining socio-economic development and ecological security. The evaluation of wetland ecological safety in plateau cities is the key to comprehensively understand ecological security status of wetland, which would provide scientific basis for protecting wetland and ecological security. With Xining section of Huangshui Basin as an example, we evaluated the ecological security of wetland from 2000 to 2019, through establishing ecological security index system of wetland based on DPSIRM model and the principal component analysis to determine the index weight. Further, the factors influencing wetland ecological security were analyzed using the gray correlation method. The results showed that the ecological security of wetland in Xining section of Huangshui Basin from 2000 to 2019 gradually improved, the comprehensive index of security increased from 0.338 to 0.781, and the level of security increased from unsafe to relatively safe. For the six subsystems, the security level of driving force, state and management had risen to relatively safe level, while pressure, impact and response had increased to safe level. Mean annual precipitation, per capita GDP, per capita water resources, water quality index, proportion of tertiary industry and wetland management level had the highest correlation scores, with the greatest influence on their ecological security. Climate and human activities were the critical factors affecting the ecological security of plateau urban wetland, mainly including mean annual precipitation, urbanization rate, water quality index, the proportion of tertiary industry, population density, the proportion of days with good air quality, per capita water resources, wetland management level, and mean annual temperature.





Effects of indoor simulated air temperature and relative humidity on the equilibrium moisture content and time lag of the fuelbed of Quercus mongolica.

ZHANG Yun-lin, TIAN Ling-ling, XIANG Min, DAI Ke-yang

2022, 41(10):  2072-2080.  doi:10.13292/j.1000-4890.202209.010

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The timelag method is the most widely used prediction model of litter moisture content. Two key parameters, equilibrium moisture content and timelag, are important for predicting litter moisture content. However, the two key parameter calculation methods currently used are not applicable because they do not consider the effects of bed structure and litter type, which causes errors in the prediction of litter moisture content. Analyzing the influence of driving factors on equilibrium moisture content and timelag, and establishing corresponding prediction models are of great significance for improving the prediction accuracy of litter moisture content. In this study, Quercus mongolica leaves were used as the research material to construct beds with different packing ratios. Through an indoor experiment with different air temperatures and relative humidity, we obtained the water loss situation and the influencing factors of the equilibrium moisture content and timelag, and established the corresponding prediction model, and analyzed the prediction ability of the model. The results showed that moisture content of the litter bed of Q. mongolica decreased exponentially with time under fixed air temperature and humidity. The equilibrium moisture content of litter bed was mainly affected by air temperature and humidity, while the timelag was affected by air temperature, humidity and packing ratio of the fuelbed. It is not feasible to directly use the Nelson model to predict the equilibrium moisture content of litter of Q. mongolica. The Simard model perfomed better than the Nelson model, with the error locating within an acceptable range. The prediction error of the selfbuilt model was not significantly different from that of the Simard model, while the coefficient of variation of the fitting parameters was smaller. A timelag prediction model for the Q. mongolica leaf bed with different packing ratios was established, and the prediction errors were all within an acceptable range. The model reveals the influencing mechanisms of air temperature, humidity, and packing ratio on timelag. Through examining the effects of air temperature, relative humidity and packing ratio of the fuelbed on the equilibrium moisture content and timelag of Q. mongolica and constructing prediction models, this study is of great significance for improving the prediction accuracy of litter moisture content and forest fire prediction.