Table of Content

15 January 2023, Volume 34 Issue 1

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Opinion of the Editor-in-Chief

Discussion on the ecological theory and technological approaches of ecosystem quality improvement and stability enhancement

YU Gui-rui, WANG Yong-sheng, YANG Meng

2023, 34(1):  1-10.  doi:10.13287/j.1001-9332.202301.025

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Improving ecosystem quality and stability is one of the urgent tasks of national ecological environment construction. However, the ecological theory of ecosystem quality and stability has not been well clarified. Based on the summary of influencing factors and interaction between ecosystem quality and stability, we discussed the ecolo-gical theory on the evolution of ecosystem quality and stability from the perspectives of self-organization of biological agglomeration and structure nesting, correlation of ecological elements and coupling of ecological processes, ecosystem integrity and function emergence, ecological service spillover and efficiency tradeoff, synergy and interactions between resource supply capacity and environmental suitability, as well as interactions between spontaneous change and human activities. Technologies approaches and management strategies were proposed from the aspects of ecosystem macro-pattern adjustment, protected natural areas system construction, regional complex ecosystem comprehensive management, degraded ecosystem restoration, damaged ecosystem reestablishment, typical ecosystem process management.

Original Articles

Effects of field soil warming on the growth and physiology of Juglans mandshurica seedlings

YU Xin-lei, YUAN Jun-feng, LIU Dong-wei, CHEN Jin-hui, YAN Qiao-ling

2023, 34(1):  11-17.  doi:10.13287/j.1001-9332.202301.009

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Global climate change will increase surface soil temperature, with consequences on plant seedling growth and population dynamics. In this study, we carried out a field experiment to investigate the effects of 2 ℃ soil warming on the growth and physiological characteristics of 1- and 2-year-old seedlings of a dominant tree species in broadleaved Korean pine forest, Juglans mandshurica. The results showed that soil warming significantly increased basal diameter, root length, total leaf area, leaf dry weight, root dry weight, total biomass, apparent photosynthetic electron transfer rate (ETR), PSⅡ actual photochemical efficiency (Φ_PSⅡ), and apparent photosynthetic electrophotochemical quenching coefficient (q_P) of 1-year-old seedlings by 18.3%, 66.7%, 94.4%, 105.9%, 95.8%, 37.8%, 89.5%, 100.0%, and 71.4%, respectively. Soil warming significantly increased basal diameter, total leaf area, leaf dry weight, total biomass, leaf superoxide dismutase activity, peroxidase activity, catalase activity and free proline content, ETR, Φ_PSⅡ, and q_P of 2-year-old seedlings by 12.5%, 180.5%, 97.3%, 42.5%, 23.9%, 20.4%, 14.9%, 20.7%, 66.7%, 283.3% and 284.6%, respectively. There was an interaction between seedling age and soil warming on the root-shoot ratio and the Φ_PSⅡ and q_P in chlorophyll fluorescence parameters, in that soil warming significantly reduced the root-shoot ratio of 2-year-old seedlings and that the increase of chlorophyll fluorescence parameters of 2-year-old seedlings (4.1-4.6 times) was much higher than that of 1-year-old seedlings (1.5-1.8 times). Soil warming of 2 ℃ was beneficial to the growth of 1- and 2-year-old J. mandshurica seedlings and increased their regeneration potential. In particular, 2-year-old J. mandshurica seedlings responded to soil warming by increasing leaf area, improving leaf photochemical efficiency, and enhancing protective enzyme activity to increase resistance.

Soil nitrification and denitrification in Cunninghamia lanceolata plantations with different stand ages

WANG Meng-juan, HUANG Zhi-qun, ZHANG Bing-bing, SHI Xiu-zhen

2023, 34(1):  18-24.  doi:10.13287/j.1001-9332.202301.002

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The variations in soil nitrification and denitrification processes, together with the abundances of functional microbes were investigated in Cunninghamia lanceolata plantations with different stand ages of 5, 8, 21, 27, and 40 years old. The results showed that the net nitrification rate fluctuated with increasing forest ages, with that of 8-year- and 27-year-old C. lanceolata plantations being significantly lower than other stand ages. The abundance of ammonia-oxidizing archaea (AOA) amoA in the 27-year-old plantation was significantly lower than that of the 40-year-old plantation, while there was no significant difference among the other stand ages. There was no significant difference in the abundance of AOB amoA gene, denitrifying functional genes or soil denitrification potential among different stand ages. The results of stepwise regression analysis showed that the abundance of AOA amoA gene was not significantly affected by soil physical and chemical properties. In addition, the abundance of AOB was positively associated with soil total carbon content and soil pH. The abundance of denitrifying functional genes including narG, nirK and nosZ increased with increasing soil pH. The abundance of nirK and nirS was influenced by soil total carbon. Stand age influenced soil net nitrification rate through the AOA amoA abundance. Moreover, soil denitrification potential was directly affected by stand age, or indirectly affected by stand age through soil microbial biomass carbon, soil pH and denitrifying gene abundance of narG and nirK. Compared with the denitrification process, soil nitrification and associated AOA amoA gene abundance were more sensitive to the development of C. lanceolata plantations. The rotation period sould be appropriately extended to reduce the risk of nitrogen losses resulting from soil nitrification.

Effects of conversion of natural forest to plantations on the abundance of nitrite reducing genes in soil aggregates in subtropical forest region

DENG Mi-lin, YE Gui-ping, XU Chao, WAN Song, HE Ji-zheng, LIN Yong-xin

2023, 34(1):  25-30.  doi:10.13287/j.1001-9332.202301.005

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Large proportion of natural forest has been transformed into plantations in subtropical regions, with consequences on forest ecosystem structure and function. In order to understand the responses of two nitrite reducing genes (nirK and nirS) in N₂O production to forest conversion, we collected soil samples from Castanopsis carlesii natural forest, Cunninghamia lanceolata plantation and Pinus massoniana plantation and examined the abundance of nirK and nirS genes in soils and aggregates. Results showed that forest conversion increased soil pH, while decreased soil ammonium content. Forest conversion did not influence the mass proportion of soil aggregates. The abundance of nirK and nirS genes varied in aggregates with different particle sizes. The abundance of nirK and nirS genes was the highest in small macraoaggregates and the lowest in the silt-clay particles. Moreover, the abundance of nirK was significantly higher than that of nirS in soils of all forest types, indicating that nirK dominated in the acidic forest soils. Conversion of natural forest to plantations significantly increased the abundance of nirK and nirS genes in the bulk soil and aggregates, indicating that forest conversion would be beneficial for the growth of microorganisms bearing nirK and nirS genes, which might be associated with the increases of soil pH. Taken together, conversion of natural forest to C. lanceolata plantation or P. massoniana plantation significantly increased the abundance of nirK and nirS in soils and aggregates, but did not affect the mass proportions of aggregates.

Characteristics and influencing factors of soil preferential flow in typical stands of Karst area in southwest China

GUAN Ning, CHENG Jin-hua, HOU Fang, ZENG He-zhou, SHEN Zi-ya, ZHAO Meng-yuan, QIN Jian-miao

2023, 34(1):  31-38.  doi:10.13287/j.1001-9332.202301.020

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The study of preferential flow phenomena in Karst areas and the identification of the main factors influencing preferential flow are of great importance for the recovery of local vegetation. The distribution of the dyeing solution in the vertical and horizontal directions was examined by field staining tracer test and image processing technique. We analyzed the total dyeing area ratio, matrix flow depth, preferential flow ratio, and length index as pre-ferential flow characteristic parameters, and 14 factors affecting preferential flow using grey correlation analysis. The results showed that there were two main types of preferential flow, funnel-shaped and dendritic, with lateral water movement occurring in the soil of typical Karst stands. The mean value of the dyeing area ratio of the understory in Karst areas was 19.4%, and that of the matrix flow depth, preferential flow ratio, and length index was 4.96 cm, 62.9%, and 385.5%, respectively. Among the 14 environmental factors influencing preferential flow, the initial soil moisture content had the strongest influence on the dyeing area ratio, the available potassium content had the most significant influence on the matrix flow depth, and available phosphorous content had the most significant influence on both the preferential flow ratio and the length index. The high degree of development and spatial variability of preferential flow under typical forest stands in Karst areas was strongly influenced by physical properties such as initial soil water content, while soil nutrient also exerts important influence on preferential flow.

Effects of slope aspect and age class on diseases of Juglans regia in Wild Walnut Nature Conservation Area of Xinjiang, China

WANG Bo, BA Xue-rui, LI Yi-yang, ZHANG Wei

2023, 34(1):  39-46.  doi:10.13287/j.1001-9332.202301.003

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To understand the disease situation of vulnerable plant Juglans regia, we investigated the proportions of four diseases of J. regia with different age classes in different slope aspects in the Wild Walnut Nature Conservation Area of Xinjiang. We analyzed the correlation of disease types and disease grades with the diameter at breast height (DBH) of J. regia and slope aspects. The results showed that the main diseases of J. regia in the reserve were walnut brown spot disease (95.8%), walnut deadwood disease (90.5%), walnut black spot disease (74.4%), and walnut rot disease (7.7%). J. regia was susceptible to walnut brown spot disease in all the four slope aspects, with walnut deadwood disease on shady and semi-shady slopes, walnut black spot disease on sunny and shady slopes, and walnut rot disease on semi-sunny and semi-shady slopes. The proportion of diseased plants with the four diseases decreased with the increases of disease grades (1-4 grades) in the four slope aspects. Across the four slope aspects, the middle-aged trees had the largest proportion of walnut deadwood disease, walnut black spot disease and walnut brown spot disease, followed by old trees and young trees. No diseased seedlings were found. Walnut rot disease only occurred in old trees. There was significant positive correlation between DBH of J. regia and the four diseases. Walnut black spot disease had significant negative correlation with slope aspect. There was correlation between different disease grades of walnut deadwood disease, walnut rot disease and walnut black spot disease with DBH and slope aspects.

Convolutional neural network tree species identification based on tree-ring radial section image features

GAO Xin, YANG Li-xin, CHEN Zhen-ju

2023, 34(1):  47-57.  doi:10.13287/j.1001-9332.202301.001

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Convolutional neural networks can automatically identify tree species based on the images of structural features of tree-rings samples. In this study, we used a tree-ring image dataset for different species to achieve tree-ring based species automatic identification with high accuracy by four convolutional neural network models (LeNet, AlexNet, GoogLeNet, and VGGNet), aiming to determine the identification accuracy of the models, clarify the species misidentification during the automatic processes, and explore the identification differences among the models. The results showed that tree species identification derived from the trained convolutional neural network models was reliable, with the GoogLeNet and LeNet showed the highest (96.7%) and lowest (66.4%) identification accuracy. The tree species identifications using different models were highly consistent. Quercus mongolica and Abies nephrolepis showed the highest (100% for AlexNet) and lowest identification accuracy, respectively. Misidentification could occur among tree species with similar tree-ring structure. The identification accuracy of the models was higher at family and genus levels than that at the species level. The identification accuracy of broadleaf tree species was higher than that of coniferous trees due to distinct radial structure among broadleaf species. Overall, our method achieved a high accuracy for tree species identification, and provided a fast, convenient, and automatic tree species identification by detecting specific tree-ring properties with convolutional neural network.

Effects of plant residues on C:N:P of soil, microbial biomass, and extracellular enzyme in an alpine mea-dow on the Qinghai-Tibetan Plateau, China

XIAO Xiang-qian, ZHANG Hai-kuo, FENG Ya-si, WANG Ji-peng, LIANG Chen-fei, CHEN You-chao, ZHU Gao-di, CAI Yan-jiang

2023, 34(1):  58-66.  doi:10.13287/j.1001-9332.202301.008

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Plant residues can affect C:N:P of soil, microbial biomass, and extracellular enzyme, but the effects are still unclear. We conducted a field experiment in an alpine meadow on the eastern part of the Qinghai-Tibetan Plateau to explore the effects of removing aboveground plant or roots and adding plant residues on the C:N:P of soil, microbial biomass, and extracellular enzyme. The results showed that removing aboveground plant biomass significantly decreased soil C:N (the change was -23.7%, the same below) and C:P (-14.7%), microbial biomass C:P and N:P, while significantly increased microbial biomass C:N, and enzyme C:N:P compared with meadow without human disturbance. Removing all plant biomass (aboveground and roots) significantly reduced soil C:N (-11.6%), C:P (-24.0%), N:P (-23.3%) and microbial biomass C:N in comparison to removing aboveground plant, while significantly improved microbial biomass N:P and enzyme N:P. Adding plant residues after removing aboveground plant significantly increased microbial biomass C:N and C:P, enzyme C:N compared with removing aboveground plant, while significantly decreased enzyme N:P. Compared with removing all the plant, adding plant residues after removing whole plant significantly reduced soil C:N (-16.4%), microbial biomass C:P, N:P and enzyme N:P, while significantly increased enzyme C:N. Our results suggest that removal of plants could have a strong effect on C:N:P of soil, microbial biomass, and extracellular enzyme, and C:N:P of microbial biomass and that extracellular enzyme woule be more sensitive to plant residues. Roots could play a key role in stabilizing C:N:P of soil, microbial biomass, and extracellular enzyme under plant residues addition. Adding plant residues could be a suitable solution for restoring alpine meadows under the circumstance of intact roots, which was conducive to soil C storage, but might not be suitable for alpine meadows with serious root damage, which would increase soil CO₂ emission.

Effects of nitrogen addition on rhizosphere soil properties in a salinized grassland

CHEN Hong-fei, ZHAO Fang-cao, WANG Yi-hao, DONG Kuan-hu, WANG Chang-hui, CHEN Xiao-peng

2023, 34(1):  67-74.  doi:10.13287/j.1001-9332.202301.004

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We explored the impacts of nitrogen (N) inputs and the rhizosphere effect on the properties of rhizosphere and bulk soils in a salinized grassland in Northern Shanxi under N addition rates of 0, 1, 2, 4, 8, 16, 24 and 32 g N·m^-2·a^-1. The results showed that N addition significantly decreased soil pH, but significantly increased Ca²⁺, NO₃^--N and inorganic nitrogen contents in rhizosphere and bulk soil. With the increases of N addition rates, the contents of Ca²⁺, NO₃^--N, inorganic nitrogen in rhizosphere and bulk soils and total nitrogen in rhizosphere soil increased gradually, whereas the contents of Na⁺, K⁺, Mg²⁺, NH₄⁺-N and amino acid in rhizosphere soil, and total nitrogen in bulk soil first increased and then decreased. Results of the principal component analysis showed that the responses of soil properties to low (≤8 g·m^-2·a^-1) and high nitrogen addition rates (>8 g·m^-2·a^-1) were significantly different. Compared with bulk soil, soil pH, the contents of organic acids and amino acids in rhizosphere soil were significantly lower by 0.71 units, 44.3% and 9.8%, respectively, while the contents of K⁺, Ca²⁺, Mg²⁺, NH₄⁺-N, inorganic nitrogen, total carbon and total nitrogen in rhizosphere soil were significantly higher by 51.0%, 47.6%, 20.8%, 215.5%, 139.3%, 31.7% and 65.3%, respectively. These results indicated that rhizosphere effect on soil properties was stronger than that of nitrogen addition.

Mechanism for the restoration of degraded typical steppe by nitrogen and phosphorus co-addition

QI Zhi-yan, LV Ya-xiang, LIU Wei, SUN Jia-mei, WANG Jing, PAN Qing-min

2023, 34(1):  75-82.  doi:10.13287/j.1001-9332.202301.007

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The reduction of soil nutrient content is one of the major reasons caused grassland degradation in China. Nutrient addition is thus considered as an effective measure for the restoration of degraded grasslands. However, over-fertilization can lead to decrease in plant diversity. To clarify the appropriate amount of nutrient addition and the underlying mechanism that promotes grassland restoration, we set up a nitrogen and phosphorus co-addition experiment in a degraded typical steppe of Inner Mongolia, and examined the responses at community, functional group and species levels to nutrient addition. The results showed that nutrient addition enhanced biomass while did not reduce species richness at the community level. The biomass showed a saturation response with the increases of nutrient addition, which approached saturation under the 12.0 g N·m^-2, 3.8 g P·m^-2 treatment. Species richness increased significantly under the lower nutrient treatments (N <9.6 g·m^-2, P < 3.0 g·m^-2) compared with the control, while the two high nutrient treatments did not alter species richness. At the functional group level, biomass and abundance of perennial rhizome grasses increased significantly with the increases of nutrient addition levels. Biomass and density of annuals increased significantly under high nutrient addition levels. However, the abundance and biomass of perennial bunchgrasses and perennial forbs were rarely affected. At the species level, six target species responded differently to nutrient addition. Biomass of Leymus chinensis was significantly increased due to the increase of population density and individual biomass. Biomass of Stipa grandis, Agropyron cristatum and Cleistogenes squarrosa change little. Biomass of Potentilla acaulis and Carex korshinskyi were reduced due to the decreases in individual biomass and population density, respectively. As a measure of restoring degraded grassland, nutrient addition could significantly increase biomass and species diversity, decrease biomass of the degradation indicator species, and increase biomass of perennial rhizomes grasses.

Application of magnetic resonance imaging (MRI) technology in the characterization of microstructure and moisture content of young Moso bamboo

HUANG Wei-wei, YANG Yu-ying, FU He-ling, DING Yu-long

2023, 34(1):  83-91.  doi:10.13287/j.1001-9332.202301.040

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Bamboo nodes play a key role in the hollow structure and the rapid growth of bamboo culm. Studying on the anatomical structure of bamboo is helpful to understand its growth mechanism. Taking the noninvasive, high-resolution and accurate technical advantages of magnetic resonance imaging (MRI), we conducted cross-sectional high-resolution MRI scanning on the tip of young Moso bamboo culm (removed shoot sheath) and extracted the gray value of the MRIs by using MATLAB software to explore the differences of water distribution in nodes, proximal nodes, and internodes. The results showed that numerous vascular bundles were repeatedly twisted and rotated horizontally at the nodal diaphragms and inner wall near the nodal diaphragms of the young bamboo, forming an intricate and highly connected network. The structure protected important tissues from mechanical stress by allocating axial loads, and enabled to laterally transport water and nutrients, which was an important basis for the rapid growth of Moso bamboo in relatively short term. The signal value (also known as brightness value) of MRIs indicated that water content of vascular bundles in young bamboo culm was much higher than that of surrounding parenchyma tissues. The mean value and standard deviation of water content between pixels of internodes were significantly higher than that of nodes, and the values of that in the proximal nodes were intermediate. The development of MRI would play a significant role in the studies of bamboo anatomy, physiology, and biochemistry.

Effects of nitrogen application rate on the accumulation of ¹³C assimilates after flowering and water-nitrogen use efficiency of wheat under supplemental irrigation based on soil moisture

LI Chuan-liang, YU Zhen-wen, ZHANG Juan, ZHANG Yong-li, SHI Yu

2023, 34(1):  92-98.  doi:10.13287/j.1001-9332.202301.014

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This study aimed to explore nitrogen fertilizer management measures to synergistically improve wheat yields and water and nitrogen use efficiency under supplemental irrigation based on soil moisture in the Huang Huai winter wheat area. Wheat variety “Yannong 1212” was used as the test material. There were three nitrogen application levels, 150 kg·hm^-2 (N₁), 210 kg·hm^-2 (N₂), and 270 kg·hm^-2 (the conventional nitrogen application rate in the Huang Huai winter wheat area, N₃), with the relative soil water content of 0-40 cm of each treatment was supplemented to 70% at the jointing and flowering stages. We investigated the effects of nitrogen rates on photosynthetic characteristics of flag leaves after flowering, ¹³C assimilate accumulation and transport, and water and nitrogen use efficiency after flowering of wheat. The results showed that photosynthetic capacity of flag leaves in the N₂ and N₃ was significantly higher than that in N₁ 14-35 days after flowering, and that there was no significant diffe-rence between N₂ and N₃ treatments. The ¹³C isotope tracing results showed that the translocation amount of ¹³C assimilates in vegetative organs in N₂ was 12.1% and 7.1% higher than that in N₁ and N₃, respectively. The distribution amount of ¹³C assimilates in grains at maturity was 10.1% and 5.3% higher than that of N₁ and N₃, respectively. The amount of nitrogen fertilizer affected water consumption, water consumption proportion, and total water consumption in different growth stages of wheat. Water consumption during the whole growth period showed no difference between N₂ and N₃ treatments, but both were significantly higher than that for N₁. Water consumption and water consumption proportion of N₂ were higher from the jointing to maturity stages, water use efficiency of N₂ was 7.5% and 4.8%, and grain yield was 4.7% and 10.9% higher than that of N₃ and N₁ treatments, respectively. The partial productivity of nitrogen fertilizer was 34.6% higher in the N₂ than that of N₃. Considering wheat grain yield and water and nitrogen use efficiency, 210 kg·hm^-2 nitrogen application was the best rate under water-saving condition of supplementary irrigation after soil moisture measurement in the study area.

Effects of the timing of epibrassinolide spraying on yield and nitrogen use efficiency of wide-belt sowing wheat

WANG Jie, HUA Yi-fan, QIN Ji-yuan, HE Ming-rong, JU Zheng-chun, LYU Peng, DENG Shu-zhen, DAI Xing-long

2023, 34(1):  99-106.  doi:10.13287/j.1001-9332.202301.041

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In this study, we investigated the effects of epibrassinolide spraying at different growth stages on grain yield and nitrogen use efficiency (NUE), and uptake efficiency (UPE) of wide-belt sowing wheat. The results showed that epibrassinolide spraying enhanced wheat grain yield by increasing the number of kernels per spike and (or) 1000-kernel weight, and improved NUE by promoting aboveground nitrogen accumulation and improving UPE. However, the magnitudes of such enhancements in yield and NUE differed among spraying times. Spraying epibrassinolide at the erecting and filling stages, jointing and filling stages, erecting, jointing, and filling stages, as well as erecting, flowering, and filling stages, produced the greatest increase in the number of kernels per spike and 1000-kernel weight, which led to substantial yield increases (12.8%-14.0%), and the greatest increase in aboveground nitrogen accumulation, which improved UPE by 16.4%-18.8%, and resulted in a significant improvement in NUE. Therefore, spraying epibrassinolide at the erecting and filling stage or jointing and filling stages could achieve high yield and NUE in wide-belt sowing wheat.

Effects of planting density on photosynthetic characteristics of flag leaf and senescence of leaf and root under wide-width sowing condition

KONG Ling-ying, ZHAO Jun-ye, ZHANG Zhen, SHI Yu, YU Zhen-wen

2023, 34(1):  107-113.  doi:10.13287/j.1001-9332.202301.016

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To determine the optimal planting density under wide-width sowing condition, we investigated the effects of different planting densities on photosynthetic characteristics of flag leaves, senescence characteristics of flag lea-ves and roots, grain yield, and water use efficiency under four planting density levels, 90×10⁴ plants·hm^-2 (D₁), 180×10⁴ plants·hm^-2 (D₂), 270×10⁴ plants·hm^-2 (D₃) and 360×10⁴ plants·hm^-2 (D₄), in field condition set in Yanzhou, Shandong during the growing season of 2018-2019 and 2019-2020. The results showed that compared with D₁ and D₄ treatments, D₂ treatment significantly improved photosynthetic characteristics of wheat flag leaves during grain filling, increased the activity of superoxide dismutase (SOD) and soluble protein content, reduced the malondialdehyde (MDA) content, and delayed the senescence of flag leaves and roots. Compared with other treatments, D₂ treatment significantly increased root length, root surface area and root volume in 0-40 cm soil layer. Compared with D₁, D₃ and D₄ treatments, the grain yield of D₂ treatment was increased by 11.8%, 2.5%, 6.4% in 2018-2019 and 22.7%, 5.7%, 17.1% in 2019-2020, respectively. In addition, water use efficiency was increased by 9.2%, 8.8%, 14.2% in 2018-2019 and 21.1%, 6.2%, 21.5% in 2019-2020, respectively. The planting density at 180×10⁴ plants·hm^-2 improved photosynthetic characteristics of flag leaves and root morphology during filling stage, delayed plant senescence, increased grain number per spike and grain weight. Consequently, the highest grain yield and water use efficiency were obtained under D₂ treatment, which was the optimal treatment under the experimental wide-width sowing condition.

Effects of water and salt stresses on plant growth and xylem hydraulic properties of tomato

WANG Yu, LI Hao, YAO Zhen-zhu, LIAO Qi, DU Tai-sheng

2023, 34(1):  114-122.  doi:10.13287/j.1001-9332.202301.012

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Xylem is the main tissue for water transport in plants, and the changes of hydraulic properties in which would affect plant water relations and fruit water accumulation. It remains unclear regarding the responses of xylem anatomy and hydraulic properties to water and salt stresses in tomato plants and their relationships with plant growth and fruit water content. We conducted a pot experiment in a greenhouse to investigate the responses of plant growth, fruit water content, and xylem hydraulic properties of a cherry tomato (Hong Baoshi) and a medium-fruited tomato (Beifan 501). There were three treatments, control with a soil water content (θ) of 75%-95% of field capacity (FC) and an initial electrical conductivity (EC) of 0.398 dS·m^-1; water stress with θ of 75%-95% of FC (before flowering) and 45%-65% of FC (from flowering until maturity) and an EC of 0.398 dS·m^-1; and salt stress with θ of 75%-95% of FC and an EC of 1.680 dS·m^-1. Results showed that water and salt stresses decreased the cross-sectional stem area and xylem vessel diameter by 22.0%-40.7% and 10.0%-18.3%, respectively, and reduced the specific hydraulic conductivity of stem and the hydraulic conductivity of peduncle by 8.8%-41.1% and 12.9%-28.4%, respectively. Those changes inhibited plant growth and reduced aboveground fresh weight, fruit size, fresh weight and water content, with a more pronounced negative effect in the medium-fruited tomato. More-over, fruit water content was positively correlated with the specific hydraulic conductivity of stem and peduncle. In conclusion, water and salt stresses would inhibit plant growht, fruit fresh weight, and consequently tomato yield, due to their negative effects on xylem hydraulic properties of the tomato plant. Medium-fruited tomatoes are more susceptible to water and salt stresses than cherry tomatoes.

Effects of elevated atmospheric CO₂ concentration on nonstructural carbohydrates and grain quality of maize

LI Chang-xin, YAN Qi, NI Li-li, ZHANG Shu-xin, WANG Li-mei

2023, 34(1):  123-130.  doi:10.13287/j.1001-9332.202301.010

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We used open-top chambers (OTCs) to simulate the conditions of elevated atmospheric CO₂ concentration at the Changwu State Key Agro-Ecological Experimental Station of the Loess Plateau. There were three treatments, CK (maize grown under field conditions with natural atmospheric CO₂ concentration), OTC (maize grown in the open-top chamber under natural atmospheric CO₂ concentration), and OTC_e (maize grown in the open-top chamber under elevated atmospheric CO₂ concentration of 700 μmol·mol^-1).We explored the responses of non-structural carbohydrate (NSC) and grain quality (soluble sugar, starch and crude protein) of spring maize to elevated CO₂ at different growth stages, aiming to provide scientific basis for revealing the adaptation mechanism of maize to elevated CO₂. The results showed that the effects of elevated CO₂ on NSC content and accumulation in maize varied across organs and growth periods. Elevated CO₂ promoted the activation and redistribution of NSC in leaves, stems and roots during reproductive growth period, and significantly increased the amount of NSC conversion to the grains (ATM_NSC), as well as the conversion rate to the grains (AR_NSC) and the contribution to the grains (AC_NSC) in leaves, stems and roots. Compared with CK, the warming effect of OTC inhibited the activation and redistribution of NSC in stems and roots, but promoted the activation and redistribution of NSC in leaves, significantly increased the ATM_NSC, AR_NSC, and AC_NSC of maize leaves. Elevated CO₂ did not affect the contents of soluble sugar, starch, and crude protein in maize grains.

Effects of phosphorus application on yield, quality and phosphorus use efficiency of edible sweetpotato: A case study of Xushu 32

LIU Ming, ZHENG Dong-mei, JIN Rong, ZHAO Peng, ZHANG Qiang-qiang, ZHU Xiao-ya, WANG Jing, TANG Zhong-hou

2023, 34(1):  131-136.  doi:10.13287/j.1001-9332.202301.017

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To explore the appropriate amount of phosphorus (P) fertilizer and improve economic yield and P use efficiency of edible sweetpotato, we took Xushu 32 as an example and compared the effects of different P application rates on yield, quality, P accumulation and P use efficiency of edible sweetpotato based on a two-year field experiment (soil available P content was 31.70 mg·kg^-1) from 2018 to 2019. There were five P application levels (P₂O₅), including 0 (P₀), 25 (P₂₅), 50 (P₅₀), 75 (P₇₅) and 100 kg·hm^-2(P₁₀₀). The results showed that, 1) compared with P₀, P application significantly increased the yield of fresh sweetpotao and commodity potato, with the effects being the stongest under P₇₅ treatment, followed by P₅₀ treatment. However, there was no significant difference between the two treatments. 2) P application significantly increased the contents of starch and reducing sugar in storage root. The contents of soluble sugar and protein increased significantly under P₅₀ treatment. 3) Du-ring the growth period of 90 to 120 d, P fertilizer supply significantly increased P accumulation and dry matter accumulation of sweetpotato. 4) The apparent P use efficiency (APUE) decreased with increasing P application rates, while P agronomic efficiency (PAE) increased first and then decreased with the increases of P application rates, which was significantly higher under P₅₀ than other treatments. Taking into account the yield, quality, economic yield and P utilization rate of edible sweetpotato, the optimal dosage of P₂O₅ is 50 kg·hm^-2 under the experimental conditions.

Responses of soil microbial biomass nitrogen to organic fertilizer with different degrees of maturity and regu-lation to soil mineral nitrogen

DENG Ya-qin, XU Zhi, ZHANG Yong, WANG Yu-yun

2023, 34(1):  137-144.  doi:10.13287/j.1001-9332.202301.018

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By combining the composting process with soil culture experiment, we conducted an experiment with four treatments, including conventional chemical fertilizer (CK), chemical fertilizer + compost maturity reaching 50% germination index (GI, the same below) organic fertilizer (CO1), chemical fertilizer + compost maturity reaching 80% GI organic fertilizer (CO2), chemical fertilizer + compost maturity reaching 100% GI organic ferti-lizer (CO3). We measured soil microbial biomass nitrogen (MBN), mineral nitrogen (NH₄⁺-N, NO₃^--N), net nitrification rate, microbial biomass carbon (MBC), dissolved organic carbon (DOC), soil urease and soil protease, aiming to reveal the regulatory effect of soil MBN on mineral nitrogen. The results showed that organic fertilizer application significantly increased MBN and NH₄⁺-N concentrations by 50.1%-62.4% and 109.9%-147.1%, reduced NO₃^--N concentration and net nitrification rate by 23.3%-46.8%, and 26.2%-51.5%, and enhanced MBC, DOC, urease and protease activities by 33.8%-69.6%, 7.4%-20.8%, 11.2%-69.0% and 9.4%-25.1%, respectively. The change ranges of CO2 and CO3 were significantly higher than CO1. Redundancy analysis (RDA) and structural equation model (SEM) results showed that the application of organic fertilizer with higher degree of maturity (GI≥80%) positively regulated soil MBC, MBN, NH₄⁺-N, and the activities of urease and protease, but had a negative effect on soil net nitrification rate. The combined application of chemical fertilizers and high decomposed organic fertilizers could significantly increase soil MBN and NH₄⁺-N contents, as well as soil urease and protease activities, but reduce soil net nitrification rate. To efficiently utilize organic solid wastes, it is recommended to use chemical fertilizer in combination of organic fertilizers with 80% decomposing degree in practical production to reduce the cost in both economy and time.

Responses of soil microorganisms, enzyme activities and nutrient contents to inter-row grass ploughing and returning to the field in a natural sod culture apple orchard

YU Bo, QIN Si-jun, LYU De-guo

2023, 34(1):  145-150.  doi:10.13287/j.1001-9332.202301.013

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Natural sod culture in orchard is an effective measure to improve the orchard productivity and promote the sustainable production. To explore the effects of inter-row grass ploughing and returning on soil biological cha-racteristics and nutrient contents, we examined the effects of different grass returning to the field on the amount of soil microorganisms, enzyme activities and nitrogen and potassium contents of 0-20 cm soil layer. There are three treatments, cleaning tillage as the control (CK), conventional mowing management (NG), and soil ploughing annually under natural sod culture with conventional mowing condition (NGR) treatments. The results showed that soil microorganisms were dominated by bacteria, followed by actinomycetes, with the least fungi. Compared with CK, both NG and NGR treatments significantly improved the abundance of soil bacteria and fungi, with the strongest effects in NGR treatment, and significantly increased the soil urease, sucrase and catalase activities by 59.0%, 20.7%, 38.3% and 73.5%, 45.9%, 67.8%, respectively. NGR treatment significantly increased soil nitrogen and potassium contents, with the contents of ammonium nitrogen, nitrate nitrogen, particulate organic nitrogen, microbial biomass nitrogen, available potassium and water-soluble potassium being 1.5, 1.8, 1.6, 2.0, 1.3 and 1.4 times of that in CK, respectively. NGR significantly increased soluble sugar content and sugar acid ratio and subsequently improved fruit quality. Overall, NGR increased soil microbial abundance, enzyme activities, nitrogen, potassium contents and fruit quality, which could be a feasible management of inter-row grasses in the natural sod culture apple orchard.

Mitigation of exogenous melatonin on photoinhibition of tomato seedlings under chilling stress

ZHAO Hai-liang, ZUO Lu, ZHANG Lu, GUO Tian-yu, ZHANG Yi, LI Xiao-jing, HU Xiao-hui, WANG Yu-ping

2023, 34(1):  151-159.  doi:10.13287/j.1001-9332.202301.015

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To understand the mitigation effects of melatonin on the chilling-induced photoinhibition in tomato, four groups of seedlings were labelled: NW (normal temperature + water), NM (normal temperature + melatonin), CW (chilling + water) and CM (chilling+ melatonin). We measured chlorophyll fluorescence, key photosynthetic parameters and the cycle efficiency for chloroplast ascorbic acid-glutathione (AsA-GSH). The results showed that, compared with the NW control, photosynthesis rate in CW was decreased by 50.3%-72.6%, chloroplast malondialdehyde content was decreased by 17.5%-132.7%, superoxide anion production was increased by 86.5%-235.9%, and H₂O₂ was increased by 96.6%-208.4%. These trends were significantly alleviated by exogenous melatonin, with photosynthetic rates in CM being increased by 22.7%-24.7% compared with in CW, malondialdehyde content being decreased by 16.6%-29.0%, the rate of superoxide anion production being decreased by 14.9%-22.7%, H₂O₂ content being decreased by 10.7%-27.1%. Compared with CW, the quantum yield of photochemical energy in PS Ⅱ was increased by 15.8% in CM, the quantum yield of regulated non-photochemical energy loss was increased by 7.2%, the quantum yield of non-regulated non-photochemical energy loss was decreased by 24.7%, and the activities of key metabolic enzymes in the AsA-GSH cycle were increased to different degrees. We concluded that exogenous melatonin application could alleviate photoinhibition in tomato seedlings under chilling by balancing the partitioning of absorption energy in PS Ⅱ and by enhancing the ROS scavenging efficiency of the AsA-GSH cycle in the chloroplast.

Variation characteristics of climatic potential yield and resources utilization efficiency of maize under the background of climate change in agro-pastoral transitional zone of Gansu, China

WANG Jun, LI Guang, YAN Li-juan, LIU Qiang, NIE Zhi-gang

2023, 34(1):  160-168.  doi:10.13287/j.1001-9332.202301.023

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To evaluate the effects of changes in radiation, accumulative temperature, precipitation and climate resources on climate resource utilization efficiency in the agro-pastoral transitional zone of Gansu Province, we analyzed the variations of climate potential yield loss rate, light, heat, precipitation and comprehensive utilization efficiency of climate resources in the agro-pastoral transitional zone of Gansu Province by the step-by-step correction and indexation method, with the 1971-2020 weather data from 45 meteorological sites and the maize phenology data. The results showed that solar radiation showed fluctuating downward trend at a rate of -22.03 MJ·m^-2·(10 a)^-1, the accumulative ≥11 ℃ temperature showed significant upward trend at a rate of 60.89 ℃·(10 a)^-1, the precipitation showed slow upward trend at a rate of 2.05 mm·(10 a)^-1 during the study period. The climate potential yield loss rate due to temperature and precipitation limitations was relatively high in Gannan and the northern part of Longzhong, while it was relatively low in the most areas of Longdong. Except for the central part of the study area and part of Longdong, the climate potential yield loss rate due to temperature and precipitation limitations in other regions of the study area showed decreased trend at the rate of -2.0%·(10 a)^-1 and -0.6%·(10 a)^-1. The low-value areas of light and heat utilization efficiency distributed in the northern and southern parts of Longzhong and part of Gannan, the low-value area of precipitation utilization efficiency distributed in Gannan, and the low value of comprehensive utilization efficiency distributed in Lanzhou and Baiyin which were 0.41 and 0.47, respectively. Longdong was the most suitable for maize planting, where the climate resources utilization efficiency of maize was highest, followed by Gannan and Longzhong. The average tendency rate of light, heat, precipitation and climate resources comprehensive utilization efficiency in the study area showed increased trend, which were 0.1%·(10 a)^-1, 0.07 kg·hm^-2·℃^-1·d^-1·(10 a)^-1, 1.17 kg·hm^-2·mm^-1·(10 a)^-1 and 0.05 ·(10 a)^-1, respectively, showing a good potential to increase maize yield.

Spatiotemporal responses of habitat quality to land use changes in the source area of Pearl River, China

WU Ke-xin, SHUI Wei, XUE Cheng-zhi, HUANG Yun-hui, JIANG Cong

2023, 34(1):  169-177.  doi:10.13287/j.1001-9332.202301.021

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Habitat quality assessment provides an effective interface for exploring the mechanisms linking land use change and biodiversity. We used InVEST model to assess the spatial and temporal variations of habitat quality in the Pearl River source area from 2000 to 2020, and to examine the impacts of land use change on habitat quality. The results showed that during the study period, construction land had the largest change, with an area increase of 321.48 km², and the area of grassland decreased most significantly. Habitat quality in the Pearl River source area was generally at a high level, with a small downward trend. The low value areas were concentrated in the town centers and main agricultural production areas, while habitat quality was high in the mountainous areas in the south and north region. The cold spots of habitat quality change had the most significant aggregation effect in the Quzhan Basin along the Nanpan River. The number of hot spots was small and scattered. Among the various types of nature reserves, habitat quality of Jiache Nature Reserve in Huize County was the lowest, and that of Zhujiangyuan Nature Reserve had a slight decreasing trend, mainly due to the transformation of grassland to cropland. The contribution of habitat quality degradation driven by land function change was 5.6 times as that of improvement. The encroachment of urban and rural construction space into grassland ecological space and agricultural production space was the dominant factor driving the reduction of habitat quality in the Pearl River source area. The contribution of construction land expansion decreased from 69.9% (2000-2010) to 46.7% (2010-2020). The expansion of construction land was the main cause for the degradation of habitat quality. The degradation threat from arable land expansion overtook the traffic network construction as the secondary threat source from 2010 to 2020. It was necessary to increase control of nature reserves in the Pearl River source area and to implement land use regulation strictly to guarantee no net loss and integrity of the ecosystem.

Urban ecological security pattern construction coupled with risk and service: A case study of Xianyang City, Shaanxi Province, China

PAN Wei-tao, YUE Bang-rui, YAO Long-jie, XUE Jian-feng, LI Jun-feng

2023, 34(1):  178-186.  doi:10.13287/j.1001-9332.202301.022

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How to combine regional ecological risks and local ecological needs to construct ecological security is one of the main issues of its application in territorial spatial governance and associated with whether it can be effectively applied. Based on the “source” accessibility and the quality of space, we constructed the ecological security pattern of Xianyang City through the way of source-corridor-node. During the construction processes, we combined the cha-racteristics of topography, influencing factors of regional ecological security, and landscape characteristics. We coupled them with morphological spatial pattern analysis (MSPA) and comprehensive evaluation results of ecological resistance, ecological connectivity and ecosystem service value, and superimposed with ecological gradient ana-lysis. The results showed that there were 66 ecological sources, with a total area of 2506.65 km², accounting for 24.6% of the total area of Xianyang City, which were mainly distributed in the northeast, west and central mountainous areas. There were 106 ecological corridors with a total length of 823.5 km, including potential corridors, water systems, irrigation canal sites, Qinzhidao and other natural and cultural systems, which extended along the ecological source to the northwest and south Weihe River. There were 20 ecological nodes to improve ecological connectivity, which were mainly distributed between second layers of loess tableland and arid mountainous areas with banded distribution in the north part of the city.

National park classification and spatial identification: A case of Yunnan Province, China

FENG Zi-xin, SUN Xin-tong, XUE Ling, ZHAGN Tian-jiao

2023, 34(1):  187-195.  doi:10.13287/j.1001-9332.202301.024

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National park is a major institutional innovation to promote the construction of ecological civilization in China. How to scientifically classify types and identify spaces is a fundamental task in the layout and construction of national parks, which is critically needed in practice. Based on the national conditions of China and related international experience, we classified national parks into wilderness oriented, ecological priority, recreation oriented, and heritage oriented types, and constructed a relatively complete national park classification scheme. With Yunnan Province as a case, which has a high degree of natural and human diversity, we established a set of index and zoning rules based on “dual evaluation”. The artificial neural networks were used to establish a land use evolution learning algorithm. The meta-cellular automata incorporating an adaptive inertia mechanism was used for spatio-temporal simulation. Spatial identification of different types of national parks was performed for the whole province under high resolution. The contraction-expansion principle was applied to compare, correct, and optimize the identified areas. A comprehensive plan for the future layout of Yunnan National Park was proposed. The results showed that national parks in Yunnan Province were mainly concentrated in the Sanjiang region and the Hengduan Mountains, the west and southwest Yunnan. Those three types of areas could be used as key areas for future natio-nal park planning and protection. The general and worth popularizing research paradigm for national park typology and spatial identification established here could be served as a reference for national application.

Runoff effect of precipitation variation and landscape pattern evolution in Lianshui watershed, Jiangxi, China

SHENG Fei, LIU Shi-yu, ZHANG Ting, YU Min-qi

2023, 34(1):  196-202.  doi:10.13287/j.1001-9332.202301.027

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Precipitation and landscape pattern are two main factors affecting runoff process of the watershed. Understanding their runoff effect is of great significance to water resources management and ecological construction of watershed. Based on the data of precipitation, runoff, and land use from 1958 to 2020, we analyzed the characteristics of precipitation, landscape pattern and runoff in Lianshui watershed in red soil hilly area of southern Jiangxi Pro-vince, established the relationship between precipitation, landscape pattern and annual runoff, flood runoff, low runoff, respectively. The results showed that the annual precipitation, runoff and annual maximum one-day runoff in the watershed showed a non-significant downward trend during the study period, while the annual minimum one-day runoff showed a non-significant upward trend but with the largest inter-annual variation range. Forested land was the landscape type with the highest proportion in watershed, and other woodland had the most dramatic variation. At the landscape level, Shannon diversity index, Shannon evenness index, patch density and landscape shape index increased from 1.125, 0.541, 0.667 and 16.925 in 1980 to 1.348, 0.614, 0.731 and 18.172 in 2020, respectively, while the landscape contagion index decreased from 68.237 in 1980 to 64.293 in 2020. The overall landscape diversity, fragmentation degree and shape complexity of the watershed increased, the spatial distribution tended to be uniform, and the connectivity decreased. The correlation coefficients between precipitation and annual runoff, flood runoff, low runoff were 0.907, 0.594 and 0.558, respectively. At the class level, the reduction of cultivated land had a greater impact on annual runoff, flood runoff, and low runoff, while the overall change at the landscape level promoted a decrease in annual runoff and flood runoff and an increase in low runoff. The contribution rate of precipitation variation and landscape pattern evolution to the change of annual runoff, flood runoff ,and low runoff were 17.8%, 82.2% and 1.5%, 98.5% and -8.8%, 108.8%, respectively. Our results could provide theoretical refe-rence for landscape pattern allocation and comprehensive management of soil and water loss.

Phosphorus limitation induced by nitrogen addition changed soil microbial community structure in a subtropical Pinus taiwanensis forest

ZHANG Xiao-qing, ZENG Quan-xin, YUAN Xiao-cun, WAN Xiao-hua, CUI Ju-yan, LI Wen-zhou, LIN Hui-ying, XIE Huan, CHEN Wen-wei, WU Jun-mei, CHEN Yueh-min

2023, 34(1):  203-212.  doi:10.13287/j.1001-9332.202301.042

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Soil microorganisms play an important role in the biogeochemical cycles of terrestrial ecosystems. How-ever, it is still unclear how the amount and duration of nitrogen (N) addition affect soil microbial community structure and whether there is a correlation between the changes in microbial community structure and their nutrient limi-tation status. In this study, we conducted an N addition experiment in a subtropical Pinus taiwanensis forest to simulate N deposition with three treatments: control (CK, 0 kg N·hm^-2·a^-1), low N (LN, 40 kg N·hm^-2·a^-1), and high N (HN, 80 kg N·hm^-2·a^-1). Basic soil physicochemical properties, phospholipid fatty acids content, and carbon (C), N and phosphorus (P) acquisition enzyme activities were measured after one and three years of N addition. The relative nutrient limitation status of soil microorganisms was analyzed using ecological enzyme stoichiometry. The results showed that one-year N addition did not affect soil microbial community structure. Three-year LN treatment significantly increased the contents of Gram-positive bacteria (G⁺), Gram-negative bacteria (G^-), actinomycetes (ACT), and total phospholipid fatty acids (TPLFA), whereas three-year HN treatment did not significantly affect soil microbial community, indicating that bacteria and ACT might be more sensitive to N addition. Nitrogen addition exacerbated soil C and P limitation. Phosphorus limitation was the optimal explanatory factor for the changes in soil microbial community structure. It suggested that P limitation induced by N addition might be more beneficial for the growth of certain oligotrophic bacteria (e.g. G⁺) and the microorganisms participating in the P cycling (e.g. ACT), with consequences on soil microbial community structure of subtropical Pinus taiwanensis forest.

Effects of linalool on Botrytis cinerea growth and control of tomato gray mold

WANG Qi-fang, WANG Xiao-yun, LI Hao-sen, YANG Xiao-yu, ZHANG Rui-min, GONG Biao, LI Xiu-ming, SHI Qing-hua

2023, 34(1):  213-220.  doi:10.13287/j.1001-9332.202301.011

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We examined the antifungal characteristics of linalool against Botrytis cinerea using plate inhibition assay and spore germination assay, and assessed the capacity of linalool in controlling tomato gray mold disease via tomato pot inoculation assay. The results showed that linalool exhibited strong inhibitive effects on mycelial growth of B. cinerea, with an EC₅₀ value of 0.581 mL·L^-1. In the spore germination test, linalool treatment inhibited spore germination in a dose-dependent manner. The electric conductivity and the malondialdehyde (MDA) contents were significantly increased in linalool-treated B. cinerea than that of the control, indicating that linalool induced oxidative damage and destroyed the cell membrane integrity in B. cinerea. The activities of the superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in the linalool-treated B. cinerea were decreased significantly by 27.4%, 68.9% and 26.0%, respectively, suggesting that linalool inhibited the antioxidant activity of B. cinerea. In the pot experiment, the diameter of lesions in linalool-treated tomatoes was significantly smaller than that of the control. The activities of SOD, POD, CAT, polyphenol oxidase, and phenylalnine ammonialyase in the linalool-treated tomatoes increased, while the MDA content decreased, suggesting that linalool could alleviate the oxidative damage caused by B. cinerea and promote plant disease resistance. In summary, linalool had inhibitory effect on the growth of B. cinerea and could control gray mold disease in tomatoes. These findings could lay the foundation for developing bota-nical antifungal agents for management of tomato gray mold disease.

Screening of phosphorus solubilizing microorganisms in cold environment and their effects on the growth of Brassica napus

SUN Jian, WANG Ya-yi, ZHANG Xin-peng, LI Song-ling

2023, 34(1):  221-228.  doi:10.13287/j.1001-9332.202212.035

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To screen out phosphorus solubilizing strains that can adapt to cold climate in Qinghai Province, Bacillus mucilaginosus, B. megaterium, B. cereus, Streptomyces violovariabilis, S. cinnamofuscus, and S. flavoagglomeratus were screened with solid plate medium as the primary and liquid medium as the secondary screening, with calcium phosphate, lecithin, and phytic acid as the single source of phosphorus. By comprehensively comparing the size of phosphate solubilizing circle in the solid plate medium and the soluble phosphorus content in the liquid medium, three strains of phosphate solubilizing bacteria with good phosphate solubilizing effects were screened, S. violovariabilis, S. cinnamofuscus, and B. mucilaginosus. The three phosphate solubilizing bacteria were made into liquid ino-culants, and the small rapeseed pot experiment was carried out with two soils with different fertilities in a cold climate in September. Compared with the control, plant height, fresh weight, root length, and root weight of rapes in high-fertility cultivated soil increased by 35.5%, 191.0%, 26.2%, and 282.7%, while plant phosphorus absorption, total phosphorus and available phosphorus contents in the rhizosphere soil increased by 968.9%, 5.1%, and 2.1%, respectively. In low-fertility soil, plant height and fresh weight was increased by 45.8% and 61.3%, root length and weight was decreased by 2.6% and 4.4%, while plant phosphorus absorption and the contents of total P and available P in rhizosphere soil were increased by 91.5 %, 29.1%, and 213.7%, respectively. The effect of the other two inoculants treatments was less significant than S. violovariabilis. Therefore, S. violovariabilis was the phosphate solubilizing strain suitable for the cold climate in Qinghai.

Cross-resistance and biochemical resistance mechanisms of avermectin resistant population of Dendrolimus punctatus

NIU Qiong-hua, FAN Xiao-dong

2023, 34(1):  229-234.  doi:10.13287/j.1001-9332.202212.036

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To identify the resistance risk and the resistance mechanism of avermectin against Dendrolimus punctatus, we examined the cross-resistance of avermectin resistance population (AV) to multiple tested insecticides and the synergism of piperonyl butoxide (PBO), triphenyl phosphate (TPP) and diethyl maleate (DEM) to AV, Qin-ling Jieguanting (JGT) and susceptible (S) popultions, by leaf dipping method. The activities of carboxylesterase (CarE), glutathione S-transferases (GST) and mixed-functional oxidases (MFOs) in AV, JGT and S populations of D. punctatus was measured with spectrophotometry. The results showed that the AV population of D. punctatus had medium level of cross-resistance to emamectin benzoate (resistance ratio, RR₅₀=25.0), chlorpyrifos (RR₅₀=19.0), and cyhalothrin (RR₅₀=15.4), and low level of cross-resistance to chlorfenapyr (RR₅₀=8.1), but no cross-resistance to spinetoram, spinosad and chlorantraniliprole. Both PBO and TPP had significant synergism of avermectin to AV, JGT, and S populations, while DEM had no synergism to all the three populations. Compared with the S population, the AV population had higher content of MFOs cytochromes P₄₅₀(3.5-fold) and b₅(3.1-fold) and the activities of O-demethylase (4.1-fold) and CarE (2.2-fold). There was no significant difference in the activities of GST between AV and S populations. The increasing mixed-functional oxidases and CarE played an important role in the resistance of D. punctatus to avermectin. Spinetoram, spinosad, chlorantraniliprole, and avermectin were recommended to control D. punctatus.

Effects of common afforestation tree species on soil bacterial community and microbial functional guilds in subtropical forests

SHAO Ya-jun, WANG Li-yan, TAN Yun-yan, LENG Peng, WANG Jian-qing, XU Jing-hua, SHI Xiu-zhen

2023, 34(1):  235-241.  doi:10.13287/j.1001-9332.202212.034

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To understand the effects of common afforestation tree species on soil microbial community in subtropical forests, seven different tree species were selected as the research object, including Pinus massoniana, Mytilaria laosensis, Liquidambar formosana, Ilex chinensis, Michelia macclurei, Quercus acutissima and Betula luminifera. Based on 16S rRNA high-throughput sequencing and real-time quantitative PCR techniques, we explored the effects of different tree species on soil bacterial community composition, diversity and microbial functional guilds. The results showed that Acidobacteria, Proteobacteria, and Actinobacteria were the dominant bacterial phyla, and that there was no significant difference in bacterial diversity or richness index among different tree species. Results of redundancy analysis suggested that soil bulk density, soil C/N, litter nitrogen content, and litter C/N were the predominant factors determining soil bacterial community composition. The afforestation tree species had significant effects on functional gene abundances of ammonia oxidizing archaea, ammonia oxidizing bacteria and complete ammonia oxidation. Comammox were dominant in abundance. Ammonia oxidizing archaea amoA gene was the only type whose abundance showed significant correlation with soil nitrate content, suggesting that ammonia oxidizing archaea could play a dominant role in the autotrophic nitrification in the acidic subtropical forest soils. The afforestation tree species had significant effects on functional gene abundances of ammonia oxidizing microorganisms. Results of correlation analysis showed that litter nitrogen content was the driving factor for the abundance of ammonia oxidizing microorganisms. Our study provided strong evidence that the responses of soil microbial functional guilds to tree species were more sensitive than bacterial community composition. Future studies should explore the mechanisms of tree plantations on forest ecosystem functioning from the perspective of microbial functional guilds.

Optimum capture size of Trichiurus japonicus in the East China Sea

YUAN Fan, ZHU Wen-bin, WANG Zhong-ming, ZHU Kai, ZHOU Yong-dong, XU Han-xiang

2023, 34(1):  242-248.  doi:10.13287/j.1001-9332.202301.037

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Trichiurus japonicus is an economically valuable species in the East China Sea, whose allowable capture size varies with fishing effort in different years. To clarify the optimum capture size for T. japonicus in the East China Sea, we collected samples and data from T. japonicus targeting fishing gears such as trawls, canvas spreader stow nets and longlines from 2016 to 2020. We estimated growth and mortality parameters using the FiSAT II software, and calculated the size limit standards for capture. The results showed that the inflection point of anal length, the critical anal length and the anal length of one-year-old T. japonicus was 382.84, 397.12, and 216.05 mm, respectively. The anal length of maturity was 230.38 mm, and the minimum capture size (anal length) was 219.23 mm. Based on the yield per recruitment analysis using Beverton-Holt model, the current fishery reference points were under overfishing condition (t_c=0.38 a, F=2.11), and the suggested optimum capture size was 364.64 mm. There would be a sharp decline of T. japonicus catches in the East China Sea if the suggested minimum capture size was substantially higher, which might be non-practical for local fishermen. Therefore, we suggested 220 mm as the capture size limit, which was close to the anal length of one-year-old fish and the anal length of maturity.

Reviews

Mountain-water-forest-farmland-lake-grassland-sandland holistic protection and restoration engineering and landscape ecology

LI Yue-hui, HU Yuan-man, WANG Zheng-wen

2023, 34(1):  249-256.  doi:10.13287/j.1001-9332.202301.026

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Theoretical researches and practices on the life community of mountain-water-forest-farmland-lake-grassland-sandland mosaic and its protection and restoration have been gradually developed in China, which demands the support of a systematic disciplinary theory. Landscape ecology, as an interdisciplinary science of geography and ecology, can meet such demand thanks to its macroscopic spatial theory and technical system. Here, landscape ecology is taken as the supporting discipline of holistic protection and restoration for mountain-water-forest-farmland-lake-grassland-sandland mosaic. Firstly, we clarified that life community of mountain-water-forest-farmland-lake-grassland-sandland is a heterogeneously mosaic landscape, which bears all the characteristics of landscape and thus follows the principles of landscape ecology. Secondly, we expounded how the basic principles of landscape-ecological construction could be applied to the planning and evaluation of holistic protection and restoration for mountain-water-forest-farmland-lake-grassland-sandland mosaic. Finally, we summarized the new trend of landscape-ecological construction research, listed the theoretical and practical problems to be solved, and discussed how the projects of holistic protection and restoration for the mountain-water-forest-farmland-lake-grassland-sandland mosaic can provide a variety of practices for seeking the solutions. The combination of landscape ecology and practical restoration projects would generate effective solutions to realize sustainable development in terms of ecology, economy, and society in China and even the whole world.

Research progress on coupling artificial intelligence and eco-environmental models

HU Yu-cong, LI Na, JIANG Yan, BAO Xin, LI Xu-yong

2023, 34(1):  257-263.  doi:10.13287/j.1001-9332.202301.019

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Artificial intelligence (AI) has been widely used in the eco-environment field, but with shortcomings in revealing the laws of natural science, such as insufficient generalization ability and poor interpretability. In order to overcome these shortages and tap into complementary advantages, coupling AI and eco-environmental models containing physical mechanism has been a new research method with fast development in recent years. We introduced the classifications of AI used in eco-environmental field, outlined its applications, and mainly illustrated the progresses, status and inadequacies for the coupling research. Based on all the summaries, we proposed a new coupling method of physical mechanism and AI for reconstructing mechanism processes, followed by analyses of theoretical significance of partial parameters, feasibility of better generalization and interpretability, as well as prospection of imitating physical mechanism. At the end of the review, we discussed the trend of the coupling method of AI and eco-environment models.

Stormwater quantity and quality control performance of bioretention systems: A literature review

ZHANG Wen-long, ZHANG Shou-hong, ZHANG Jian-jun

2023, 34(1):  264-276.  doi:10.13287/j.1001-9332.202301.028

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Bioretention systems, as one of the most widely used modern stormwater management tools, have outstanding performance in capturing runoff, mitigating peak flow, delaying outflow occur time, and improving effluent quality. We reviewed the research of hydrologic and water quality performance of bioretention systems around the world from different perspectives, including the structure and classification of bioretention systems, the mechanisms of runoff and pollutants regulation of bioretention systems, the hydrologic and water quality performances of bioretention systems, the runoff control and water purification evaluation models of bioretention systems, as well as the influencing factors of runoff control and water purification efficiency. We proposed that future research should focus on hydrologic and water quality of bioretention systems, e.g., optimization of design configurations, revealing the mechanisms of plant action, revealing the mechanisms of microbial action, the effects of climate change on hydrologic and water quality performance, watershed/regional scale hydrologic and water quality performance, purification effect and mechanisms of emerging pollutants, maintenance methods, as well as life-cycle assessment and cost analysis. This review would provide theoretical and technical supports for research, design, construction, and maintenance of bioretention systems.

Research advance in the distribution and ecotoxicological effects of microcystins in aquatic ecosystem

QIU Yu, MA Zeng-ling, ZHANG Zi-yi, CHEN Yu-tao, QIN Wen-li, JIA Yang, WANG Min

2023, 34(1):  277-288.  doi:10.13287/j.1001-9332.202212.033

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Cyanotoxins produced by the toxic cyanobacteria is a great threat to global freshwater ecosystems, with hepatotoxic microcystins (MCs) as the most widely distributed and harmful ones. MCs have negative impacts on the structure, function and stability of aquatic ecosystems, posing threats to human health. In this study, we reviewed the distribution of MCs in waterbody, sediments, and different groups of aquatic animals. The toxicity mechanisms of MCs were also reviewed. The ecotoxicological effects of MCs on aquatic animals, aquatic and terrestrial plants, human health risk were summarized. Several biological methods about the prevention and control of MCs were mentioned. Many aspects about MCs that need to be further studied were proposed, aiming to provide a scientific basis for risk assessment and management of MCs.