Table of Content

15 April 2022, Volume 33 Issue 4

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Opinion of the Editor-in-Chief

Discussion on the ecological theory and assessment methods of ecosystem quality and its evolution

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

2022, 33(4):  865-877.  doi:10.13287/j.1001-9332.202204.026

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Ecological civilization construction and ecological environment governance are basic tasks of state gover-nance in China. China has clearly put forward the goal of improving ecosystem quality and stability. However, there are no consensus on the scientific concept of ecosystem quality and the assessment methods of ecosystem quality evolution, which has puzzled the academic community. Based on the summarization of the scientific concept of ecosystem quality and its evolution, we discussed the concept of ecosystem quality and its ecological theory basis by referencing the concept of production quality, quality management and quality assessment of material production. The scientific connotation of ecosystem quality and its evolution was discussed from the perspectives of ecosystem natural attribute-social attribute-economic attribute and the relationships between them, the cascade relations of ecosystem component-structure-process-function-service-efficacy, the feedback of factor-system-environment, and the logic relation of state ecosystem fluctuation-quantity variation-quality alternation. We proposed perspectives and approaches of multi-objective assessment of ecosystem quality alternation from the aspects of natural resource environment system, typical ecosystem, regional macro-ecosystem, and ecological engineering efficacy.

Special Features of Soil Physics and Ecological Environment

Soil physical and chemical properties and vegetation characteristics of different types of grassland in Qilian Mountains, China

YANG Xue-ting, FAN Jun, GE Jia-min, DU Meng-ge, JIN Mu

2022, 33(4):  878-886.  doi:10.13287/j.1001-9332.202204.019

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Grasslands in Qilian Mountains plays an important role in maintaining the ecological security of western China. To understand soil physical and chemical properties and the distribution characteristics of vegetation, as well as their correlation in different types of grasslands in Qilian Mountains, we measured soil moisture, nutrient content, bulk density, particle composition, and vegetation characteristics in seven types of grassland in Qilian Mountains. The fractal dimension of soil particles, soil organic carbon, total nitrogen and total phosphorus storages in 0-40 cm soil layer, and plant diversity index were calculated. The results showed that there were significant differences in soil physical and chemical properties and vegetation characteristics among different grassland types. Compared with other types of grassland, alpine meadow had higher soil water, nutrient and clay content, but lower bulk density and sand content. Soil organic carbon, total nitrogen and total phosphorus storages in 0-40 cm layer ranged from 3084 to 45247, 164 to 2358 and 100 to 319 g·m^-2, respectively, with high contents of organic carbon and total nitrogen and low content of total phosphorus. There was a significant positive correlation between soil total phosphorus storage and plant diversity index, indicating that soil total phosphorus content was the key factor affec-ting grassland plant diversity in Qilian Mountains. Compared with other grassland types, alpine meadow in Qilian Mountains had better vegetation status, soil moisture, and nutrient conditions.

Effects of drilling waste combined with exogenous organic matter on physicochemical properties of aeolian sandy soil and growth of spinach

WANG Xi, FAN Jun, ZHOU Gu, FU Wei

2022, 33(4):  887-893.  doi:10.13287/j.1001-9332.202204.024

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An indoor potted experiment was carried out to study the application effects of water-based waste drilling mud (WBDM) and drill cuttings combined with humic acid and woody peat in aeolian sandy soil.We analyze their effects on the growth of spinach, in order to provide a reference for the resource utilization of drilling waste and the improvement of aeolian sandy soil. A total of three individual experiments were set up: 4 treatments in the basic group, taking aeolian sandy soil as the control (CK), mixing aeolian sandy soil and drill cuttings at a mass ratio of 1:1, then added with 0, 2%, and 4% WBDM (dry basis) respectively. The basic group treatment was added with 1% humic acid, 1% humic acid+3% woody peat mixture respectively, as the humic acid group and woody peat group. The results showed that in the basic group, drilling waste application significantly increased soil organic matter content (SOM), pH and electrical conductivity, the 2% WBDM significantly promoted the growth of spinach. Humic acid and woody peat reduced soil pH and increased SOM content and electrical conductivity. Plant growth indicators such as plant height, total leaf area, fresh weight and dry weight of the humic acid group were higher than the corresponding treatments in the basic group. The mixed addition of humic acid and woody peat did not affect plant growth. The treatment with the best performance was to add 2% WBDM to the humic acid group, and the SOM was 13.1 g·kg^-1, spinach's plant height, total leaf area, fresh weight and dry weight significantly increased by 49.7%, 93.4%, 83.3%, and 34.6% than CK after 40 days of sowing. The application of drilling waste with organic matter could significantly increase SOM content and promote spinach growth. Aeolian sandy soil + drill cuttings + WBDM (2%) + humic acid (1%) was the best combination mode.

Effects of residual film density and area on water accumulation infiltration amount of soil

LI Yue, WANG Chun-xia, HE Xin-lin, WU Chen-tao, NIU Jing-ran

2022, 33(4):  894-900.  doi:10.13287/j.1001-9332.202204.023

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With continuous increases in the amount and duration of plastic film used, the residual film in farmland soil is accumulated and tended to be fragmented, which affects soil water infiltration. We carried out an experiment of one-dimensional vertical infiltration of soil moisture. We examined the effects of different residual film density and area on soil water cumulative infiltration under 21 experimental treatments with 5 residual film area levels (0.25, 0.5, 1, 2, 8 cm²) and 5 residual film density levels (0, 60, 180, 300, 420 kg·hm^-2). The results showed that soil water infiltration rate was accelerated and the total infiltration amount was increased by adding a certain amount of residual film into the clay loam soil with bulk density of 1.53 g·cm^-3. The total infiltration amount of different residual film area always appeared mutation or turning point when the single residual film area was 1 cm². When the residual film area and density were larger or smaller than that, the cumulative infiltration amount would be significantly affected, with the treatment of 0.5 cm² residual film area and 200 kg·hm^-2 residual film density being obvious demarcation. When the residual film area was 0.25 cm², the cumulative infiltration reached the maximum. When the residual film with a single area ≤0.25 cm² was uniformly mixed into the soil, the slope of soil water cumulative infiltration curve was significantly different from that of other residual film treatments, forming a “new structure” soil with unique water infiltration characteristics.

Effects of exogenous attapulgite addition on water conservation function of reclaimed soils in a semi-arid mining area

TAO Tao, MA Dong-hao, WU Si-cong, HUO Ya-wen, CHEN Jin-lin, ZHANG Jia-bao, ZHANG Cong-zhi, TAN Jun, PAN Hui, MA Hong-jiao

2022, 33(4):  901-908.  doi:10.13287/j.1001-9332.202204.027

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Large-scale mining has greatly damaged vegetation and caused ecological degradation in the semi-arid area in China. It is urgent to restore the vegetation to solve the deteriorating ecological and environmental problems in mining area. How to reclaim soils for effectively storing and utilizing precipitation is the primary issue for vegetation restoration in the area. In this study, we proposed to take the mixture of attapulgite clay and local sandy soils as covering materials to improve the weak water conservation function of soils in mining areas, and studied the effects of the addition of attapulgite clay on soil infiltration, drainage and water storage sampled from the Shenmu mining area. The results showed that, with increasing application rates of attapulgite clay, the cumulated infiltration volumes decreased by 4.8%-37.4%, the infiltration rates dropped by 6.4%-46.3%, the wetting front advance rates decreased by 9.8%-116.9%, the saturated hydraulic conductivities decreased by 14.3%-59.5%, the drained water volumes reduced by 0.3%-4.3% for 24 hours and by 0.3%-2.5% for 72 hours, and the maximum soil water storages increased by 1.6%-22.4%. The maximum effect of attapulgite clay peaked at the application rate of 150 t·hm^-2. Considering the economic cost, the optimum application rate should be 30-150 t·hm^-2. The results syste-matically revealed the mechanism of reclaiming mining soils with attapulgite clay to restore the function of water conservation, and demonstrated that attapulgite clay is an effective material for soil reclamation in the semi-arid mining area, which can provide references for soil reclamation and ecological restoration in the semi-arid mining area.

Applicability of cosmic-ray neutron sensing for monitoring soil moisture in farmland

JIANG Yi-fei, LI Xiao-peng, XUAN Ke-fan, JI Jing-chun, JIA Ren-hao, WANG Can, LIU Jian-li

2022, 33(4):  909-914.  doi:10.13287/j.1001-9332.202204.020

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Cosmic-ray neutron sensing (CRNS) method was recently used to monitor soil moisture in farmland. But its spatial representation and accuracy needs further study. A field experiment was carried out to evaluate the applicability of CRNS for monitoring soil moisture in winter wheat farmland of the North China Plain. The spatial weight of CRNS detector was simulated by the ultra rapid adaptable neutron-only simulation for environmental research (URANOS) model and the CRNS-estimated soil moisture was compared with the measured soil moisture. The results showed that the CRNS detection radius obtained by URANOS simulation was 127-139 m, and that the weight distribution showed good agreement with the theoretical value. The determination coefficient (R²) and the root-mean-square error (RMSE) between CRNS-estimated soil moisture and measured soil moisture reached 0.64 and 0.05 cm³·cm^-3, respectively. The CRNS-estimated soil moisture was sensitive to the changes of overall moisture in the detection area, with seasonal variation of measurement accuracy. In conclusion, cosmic-ray neutron sensing is a continuous and reliable method for monitoring total water content in winter wheat fields.

Spatial variability of soil available potassium in rubber plantation based on coKriging

FENG Jia-dong, WU Bing-sun, WANG Jing-jing

2022, 33(4):  915-921.  doi:10.13287/j.1001-9332.202204.022

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The coKriging method of selecting effective variables is helpful to improve the spatial prediction accuracy of soil available potassium in county-scale rubber plantation, which is of significance in precision fertilization management of rubber plantation. In this study, we analyzed the spatial variability characteristics of soil available potassium in 0-20 cm layer in the rubber plantation of Baisha County, Hainan Province, by geostatistics. The significant characteristic variables were screened by correlation analysis, and the spatial interpolation precisions of coKriging (COK) of different variables were compared. The results showed that the average soil available potassium content in the study area was 44.65 g·kg^-1, generally at a state of shortage. The variable coefficient was 52.6%, which was a moderate intensity of variation. The nugget effect was 12.5%, with a strong spatial autocorrelation. The organic matter and elevation were closely related to soil available potassium content. The COK spatial interpolation prediction precisions of the three covariates of organic matter (COK₁), elevation (COK₂), and organic matter+elevation (COK₃) were all higher than ordinary Kriging (OK), and the fitting precision of the cross-validation model was COK₁>COK₃>COK₂>OK. The fitting precision was not proportional to the number of covariates selected. Selecting more correlated covariates was more conducive to reflecting the spatial heterogeneity of soil properties. The soil available potassium content was higher in the northwest and lower in the central and eastern regions, which provided a theoretical basis for the further development of soil potassium management in rubber plantations.

Effects of different spectra types on the accuracy and correction of soil salt content inversion in Yinchuan Plain, China

CHEN Rui-hua, SHANG Tiao-hao, ZHANG Jun-hua, WANG Yi-jing, JIA Ke-li

2022, 33(4):  922-930.  doi:10.13287/j.1001-9332.202204.025

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Soil salinization is one of key drivers for the degradation of soil quality and yield in arable land. To accurately and quickly evaluate soil salt content in Yinchuan Plain, field and indoor hyperspectral data were processed with first order differential (FDR) transformation, then the feature bands were identified by stepwise regression (SR). Partial least squares regression (PLSR) and support vector machines (SVM) were used to build models, which were verified to figure out the optimal hyperspectral type for the study area. Moreover, segmented and global corrections were performed to process poor hyperspectral, aiming to improve the accuracy of soil salt content inversion. The results showed that the accuracy of soil salt content inversion model based on field hyperspectral data was 58.9% higher than that of the indoor hyperspectral data. The accuracy of the inversion was improved through the segmented and global correction of the indoor hyperspectral. We found that the segmented correction is more accurate for the PLSR model (R_c²=0.790, R_p²=0.633, RPD=1.64) and the global correction is more accurate for the SVM model (R_c²=0.927, R_p²=0.947, RPD=3.87). The SVM models' inversion accuracy was higher than that of PLSR, with the field hyperspectral model fitted the best, followed by the indoor hyperspectral processed with the global correction and the indoor hyperspectral processed with the segmented correction, while the indoor hyperspectral the worst. Our results suggest that field hyperspectral data could contribute to the quantitative inversion of soil salt content in Yinchuan Plain. The corrected indoor hyperspectral could significantly enhance the inversion accuracy of soil salt content, which could guarantee food security and ecological quality development.

Low sap flow of Picea crassifolia and its influencing factors in Qilian Mountains, China

DU Meng-ge, WANG Shan-ju, FAN Jun, GE Hong-yuan

2022, 33(4):  931-938.  doi:10.13287/j.1001-9332.202204.021

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As an important part of ecological hydrology, transpiration is the basis for analyzing forest water cycle and healthy growth, and important for forest protection and scientific management. We used thermal diffusion probes (TDP) to continuously monitor sap flow of Picea crassifolia in the Qilian Mountains from 2017 to 2018 to explore water consumption of P. crassifolia, and analyze the main controlling factors for the growth and transpiration of spruce. The results showed that the instantaneous change of P. crassifolia sap flow showed a single-peak curve in sunny days, a multi-peak or double-peak curve in cloudy days, and basically no obvious regularity in rainy days. The sap flow density of Qinghai spruce was consistent with the dynamics of solar radiation. The sap flow started earlier and ended later on sunny days, and lasted for 12 to 14 hours. Due to the high altitude (2700 m), low air temperature, and low vapor pressure difference (VPD) in this area, the overall sap flow density was low, with an average of (0.86±0.49) kg·d^-1. On the hourly scale, the instantaneous rate of sap flow was significantly affected by solar radiation and VPD. On the daily scale, soil temperature and soil moisture content of the 0-40 cm layer were significantly related to sap flow density. The spruce sap flow density decreased with the decreases of solar radiation, air temperature, and VPD. In the high-altitude forest area of Qilian Mountains, lower soil and air temperature as well as lower VPD and solar radiation were the causes of low sap flow in Picea crassifolia in this area.

Original Articles

Distribution of phosphorus fractions in soil aggregates in Chinese fir plantations with different stand ages

ZHANG Zhe, HUANG Yong-zhen, ZHANG Chao, YE Shao-ming, WANG Sheng-qiang

2022, 33(4):  939-948.  doi:10.13287/j.1001-9332.202204.001

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Exploring the distribution of phosphorus (P) fractionsin soil aggregates is helpful to improve soil P availa-bility during Chinese fir planting. In this study, soil samples were collected in the 0-20 cm soil layer from Chinese fir plantations with different stand ages (9 a, 17 a, and 26 a) and one nearby abandoned land (CK) in Rongshui County, Guangxi, China. Soil aggregates were classified into >2 mm, 1-2 mm, 0.25-1 mm, and <0.25 mm size classes through dry-sieving process, and then soil P fractions in different sized aggregates were measured. These results showed that: 1) The composition of soil aggregates showed significant difference among different stand ages. As the major aggregate fractions in soil, the contents of >2 mm aggregates increased firstly and then decreased over time, and peaked in the 17 a Chinese fir plantation. The changes of soil mean weight diameter (MWD) and geometric mean diameter (GMD) during Chinese fir planting were the same as the content of >2 mm aggregates. 2) Soil total P, inorganic P, and organic P contents did not differ among different sized aggregates. However, soil available P content was mainly distributed in >2 mm aggregates with a range of 1.23-7.33 mg·kg^-1. Compared with CK, soil total P, available P, and inorganic P contents were significantly higher in Chinese fir plantations, and their contents increased firstly and then decreased over time. Soil total P (322.40 mg·kg^-1) and available P (7.33 mg·kg^-1) contents were the highest in the 9 a plantations, and soil inorganic P content (114.05 mg·kg^-1) was the highest in the 17 a plantation. Moreover, soil organic P content showed an order of 9 a > 26 a >17 a > CK, with the highest content (210.00 mg·kg^-1) in the 9 a plantation. 3) The distribution of P stock in soil aggregates was related to the contents of different sized aggregates, with >2 mm aggregates having the highest P stock. Except for organic P, soil P stock increased firstly and then decreased with the increases of stand age. In conclusion, Chinese fir planting was helpful to improve soil aggregate stability and to promote the increase of soil P level before the stand age of 17 a. However, Chinese fir planting could result in the degradation of soil aggregates and in the decrease of soil P level after 17 a. The formation and stabilization of >2 mm aggregates played an important role in the maintenance of soil quality and soil P supply level after 17 a Chinese fir planting.

Effects of root exudates C:N on soil physical and chemical characteristics and soil respiration in Robinia pseudoacacia plantation

ZHANG Hai-long, WU Run-qin, LI Jia-jia, WANG Rui-qiang, XIAHOU Long, YANG Chun-xia, SHANGGUAN Zhou-ping

2022, 33(4):  949-956.  doi:10.13287/j.1001-9332.202204.013

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We explored the effects of C:N ratio in root exudates of Robinia pseudoacacia plantations on soil nutrient cycling and microbial activity on the Loess Plateau. We collected in-situ soil from the R. pseudoacacia plantations with essentially identical habitat conditions and growing time of 15, 25, 35, and 45 years. By adding root exudates with different C:N ratios (N only, C:N=10, C:N=50, C:N=100, C only) to the soil and using deionized water as a control, we analyzed the effects of C:N ratio of root exudates on the physicochemical properties of elements such as carbon, nitrogen and phosphorus, soil pH, and soil respiration. The results showed that: 1) Organic carbon content was positively correlated with the C:N ratio of root exudates. Soil organic carbon (SOC) decomposition was faster when root exudates C:N=10. Higher C:N ratio of root exudates (C:N=100) could inhibit SOC decomposition, but only C addition had no significant effect on SOC. 2) Different root exudate C:N produced no significant influence on the total nitrogen. The addition of carbon promoted microbial uptake of ammonium nitrogen, while the addition of nitrogen promoted the nitrification of ammonium nitrogen. As the C:N ratio of root exudates increased, soil ammonium nitrogen content decreased. 3) The addition of nitrogen would reduce soil pH and increase soil total phosphorus content. 4) Soil respiration of R. pseudoacacia plantations was positively correlated with the C:N ratio of root exudates. With the increases of C:N ratio, the promoting effect of root exudates on soil respiration at 25 and 35 years R. pseudoacacia plantations was stronger. In conclusion, higher C:N ratio of root exudates will significantly promote the effect on soil respiration of R. pseudoacacia plantations. Our results improved the understan-ding of the root-soil-microbial interactions in forests.

Transcriptome analysis on responses of leaf photosynthesis and nitrogen metabolism of Larix gmelinii to environmental change

LIU Mei-shuo, WANG Chuan-kuan, QUAN Xian-kui

2022, 33(4):  957-962.  doi:10.13287/j.1001-9332.202203.008

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To reveal molecular mechanisms underlying photosynthesis responses of Dahurian larch (Larix gmelinii) to environmental changes, we used the high-throughput sequencing technology to sequence the transcriptome of larch leaves from four latitudinal sites with different environmental conditions, and compared differential expression genes (DEGs). The four sites from high- to low-latitude were Tahe (52°52′ N), Songling (50°72′ N), Heihe (49°22′ N), and Dailing (47°08′ N). A total of 282428811 clean reads were sequenced out, among which the abundace of DEGs were 16915, 18812, 28536, 20635, 29957 and 23617 for the Tahe-Songling, Tahe-Heihe, Tahe-Dailing, Songling-Heihe, Songling-Dailing, and Heihe-Dailing comparisons, respectively. The expression of nine Psb genes family (i.e., PsbB, PsbK, PsbO, PsbP, PsbQ, PsbS, PsbW, Psb27, and Psb28) encoding Photosystem Ⅱ and that of three genes (ATPF1A,atpA, ATPF1G, atpG, and ATPF1D, atpH) encoding F-type ATPase, which were involved in photosynthesis pathway, were significantly up-regulated with increasing environmental differences among the sites. A similar up-regulation pattern occurred for the expression of genes encoding glutamine synthetase (glnA, GLUL), nitrate reductase (NR), and carbonic anhydrase (cynT, can) that were involved in nitrogen metabolism pathway. The numbers of DEGs and up-regulated genes increased with the increases in environmental changes among the sites, resulting in inter-site divergence of photosynthetic capacity of larch trees.

Effects of arbuscular mycorrhizal fungi inoculation on non-structural carbohydrate contents and C:N:P stoichiometry of Heptacodium miconioides under drought stress

LI Yue-ling, JIN Ze-xin, LUO Guang-yu, CHEN Chao, SUN Zhong-shuai, WANG Xiao-yan

2022, 33(4):  963-971.  doi:10.13287/j.1001-9332.202204.014

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A pot experiment was conducted to investigate the effects of drought stress and arbuscular mycorrhizal fungi (AMF) inoculation on C:N:P stoichiometry and non-structural carbohydrate (NSC) contents in two-year-old Heptacodium miconioides seedlings. There were four treatments, including control (CK), drought stress (D), AMF inoculation (AMF), and combined drought stress and AMF inoculation (D+AMF). The results showed that drought stress significantly reduced AMF colonization rate, whereas plant height and leaf number of inoculated treatment were significantly higher than the non-inoculated treatment. Inoculation with AMF significantly increased soluble sugar and NSC content in root and leaf, as well as starch content in stem and leaf. The inoculation significantly decreased the stem and leaf soluble sugar to starch ratio under drought stress. Drought stress caused a significant increase in C content in roots and leaves, and a significant decrease in P content in stems. Compared with no inoculation drought stress, P content in roots, stems, leaves, and C content in leaves of mycorrhizal seedlings were significantly increased by inoculation under drought stress, whereas root C and N content and stem C content were significantly reduced. Under drought stress, AMF inoculation significantly decreased C:N, C:P, and N:P ratios in roots and stems, and N:P ratios in leaves of H. miconioides. P content in roots and leaves were significantly positively correlated with soluble sugar and NSC content. Stem P content was significantly positively correlated with starch and NSC content. N:P ratios in each organ was significantly negatively correlated with NSC content. In all, inoculation with AMF can improve the drought tolerance of H. miconioides seedling by increasing soluble sugar content in roots and leaves and the soluble sugar/starch ratio in roots, improving starch content in above-ground organs, promoting the P absorption, and reducing N:P ratios in each organ. Therefore, AMF colonization could improve the survival rate of H. miconioides seedling in dry environments.

Modification of quicklime on acid soil under forest and their effect on the growth of Panax notoginseng

ZHANG Yi-jie, XU Jie, LU Ren-chuang, YE Chen, HUANG Hui-chuan, YANG Min, HE Xia-hong, ZHU Shu-sheng

2022, 33(4):  972-980.  doi:10.13287/j.1001-9332.202204.018

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Soil acidification is an important factor leading to poor growth and root rot disease of Panax notoginseng in the understorey of forests. In this study, different amounts of quicklime (0, 500, 1000, 1500 and 2000 kg·hm^-2) were amended into acid soil under forest. We evaluated the effect of quikelime addition on soil chemical properties, phenols, rhizosphere microorganisms and growth of P. notoginseng. The results showed that an appro-priate amount of quicklime addition (500-1000 kg·hm^-2) could significantly increase soil pH, decrease the content of phenols (p-hydroxybenzoic acid, vanillin, syringic acid, ferulic acid and vanillic acid), promote P. notoginseng growth, and reduce the incidence of root rot disease. An appropriate amount of quicklime (500-1000 kg·hm^-2) could significantly reduce the fungi:bacteria ratio, increase bacteria diversity, and increase the relative abundance of Ascomycota and Proteobacteria as well as Massilia and Sphingomonas. However, excessive quicklime addition (1500-2000 kg·hm^-2) could reduce the content of available nitrogen and organic matter, and inhibit P. notoginseng growth. Therefore, 500-1000 kg·hm^-2 of quicklime amendment could improve the chemical properties and microbial community of acid soil under forest, thereby promoting P. notoginseng growth, and reducing the incidence of root rot disease.

Effects of nitrogen addition on the contents and stoichiometric ratio of nitrogen and potassium in a meadow steppe of Hulunbuir, China

GAO Bei, HU Yan-yu, ZHANG Zhi-wei, DING Cong, YANG Yan-ru, LYU Xiao-tao

2022, 33(4):  981-987.  doi:10.13287/j.1001-9332.202203.007

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Potassium (K) is the second most abundant nutrient in plant leaves after nitrogen (N) and the most abundant cation in plant cells. It plays an important role in plant growth regulation, homeostasis maintenance, and stress response. Previous studies on the effects of N input on plant nutrient status mainly focus on N and phosphorus (P), but less on K and its stoichiometry. We examined the effects of N input and mowing on K content and N:K at both plant functional group and community levels. We analyzed the relative contribution of changes in functional groups and community composition to changes of community level nutrition status. The results showed that N input increased N content of each plant functional group and increased K content of rhizomatous grasses and legumes. Mowing reduced N content of rhizomatous grasses and bunchgrass, but did not affect K content and N:K of all functional groups. Nitrogen input significantly increased plant N and K contents at the community level, while mowing significantly increased plant N content. Both N input and mowing did not affect plant N:K at functional group and community levels. The contribution of nutritional changes in plant functional groups to the variation at the community level was greater than that of changes in community composition. For all the three examined nutritional traits, the contribution of nutrients at functional group level and that of community composition showed negative covariation. Our results indicated that plant N:K had high homeostasis in meadow steppe and that plants could regulate N and K balance, which was of great significance for maintaining N:K stoichiometry under the background of increasing N deposition.

Effects of regulation measure on soil and microbial biomass of moderately degraded alpine meadow in Qilian Mountain, China

LIU Jing-jing, YIN Ya-li, LI Shi-xiong, ZHAO Wen, SU Shi-feng, DONG Yi-ling

2022, 33(4):  988-994.  doi:10.13287/j.1001-9332.202203.009

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We examined the effects of different regulation measures (spring rest grazing, spring rest grazing-cutting turf, spring rest grazing-cutting turf-fertilization, spring rest grazing-cutting turf-sowing, spring rest grazing-cutting turf-fertilization-sowing) on vegetation, soil physical and chemical properties, and soil microbial biomass in mode-rately degraded alpine meadow in Qilian Mountain. The results showed that all the regulation measures significantly increased plant coverage and aboveground and underground biomass of degraded alpine meadows. Plant species richness increased significantly under the two measures of spring rest grazing-cutting turf-fertilization and spring rest grazing-cutting turf-fertilization-sowing. The dominant species of spring rest grazing-cutting turf-sowing and spring rest grazing-cutting turf-fertilization-sowing was Poa pratensis cv. Qinghai. Soil pH and bulk density in moderately degraded alpine meadow (control) were significantly higher than those of all regulation measures. Soil water content, soil organic carbon, total nitrogen and total potassium, carbon-nitrogen ratio and nitrogen-phosphorus ratio of spring rest grazing-cutting turf-fertilization-sowing measures were the highest, which were 21.3%, 22.30 g·kg^-1, 2.77 g·kg^-1, 19.93 g·kg^-1, 8.3 and 3.5, respectively. Soil microbial biomass nitrogen and phosphorus (104.98 and 40.74 mg·kg^-1) of degraded meadows under spring rest grazing-cutting turf-fertilization-sowing measures were significantly higher than those of other measures, while soil microbial biomass carbon (240.72 mg·kg^-1) of degraded meadows under spring rest grazing-cutting turf-fertilization measures was significantly higher than that of other measures. The results of radar map showed that the regulation measures affected the characteristics of degra-ded meadow vegetation (aboveground and underground biomass), soil physical and chemical properties (water content, organic carbon, total nitrogen, total phosphorus, and total potassium) and soil microbial biomass (carbon, nitrogen and phosphorus). Spring rest grazing-cutting turf-fertilization-sowing measures had the best performance in restoraing degraded meadows in the study area.

Effects of increasing CO₂ concentration and water deficit on photosynthetic performance and water use efficiency of typical green manure plants

GUO Da-gang, LI Fei, GAO Xiao-dong, HE Na-na, ZHAO Xi-ning

2022, 33(4):  995-1002.  doi:10.13287/j.1001-9332.202204.033

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Exploring the impacts of CO₂ and soil water availability on the photosynthetic performance and water use efficiency of three green manure plants could provide theoretical basis for the adaptive management of grassland ecosystems under future climate change. An experiment was conducted in an artificial climate chamber with precisely controled CO₂ concentrations of 400 (natural atmospheric) and 800 μmol·mol^-1 (doubled), and four water treatments, 80% field water holding capacity (FC) (full irrigation control group), 55%-60% FC (mild water deficit), 35%-40% FC (moderate water deficit), <35% FC (severe water deficit) to investigate the impacts of increasing CO₂ concentration and water deficit on chlorophyll content, gas exchange variables, and water use efficiency (WUE) of oilseed rape (Brassica napus), white clover (Trifolium repens), and alfalfa (Medicago sativa). The results showed that under the same CO₂ concentration, when soil moisture was less than 40% FC, the chlorophyll content and gas exchange parameters of three plants were significantly decreased. The treatment of 55%-60% FC did not alter the total chlorophyll content of three species, but reduced the photosynthetic rate (P_n) and transpiration rate (T_r) of white clover and alfalfa by 6%-25% and did not affect their WUE. Compared with atmospheric CO₂ concentration, the doubled CO₂ concentration significantly decreased the P_n of oilseed rape by 21.5% under the full irrigation treatment, increased the P_n of three species under mild water deficit, increased the P_n of oilseed rape and alfalfa under moderate water deficit, but only improved the P_n of alfalfa under severe water deficit. The doubled CO₂ concentration significantly increased WUE of white clover and alfalfa under all water deficit conditions, but only increased WUE of oilseed rape under mild water deficit. Increasing CO₂ concentration and water deficit significantly interacted to affect P_n of three species and the WUE of oilseed rape. In summary, the three species differed in their responses to doubled atmospheric CO₂ concentration and different levels of water deficit. Our results suggested that elevated CO₂ concentration could improve the adverse effects of mild water deficit on photosynthetic performance and WUE of three species, but only improve the photosynthetic performance of alfalfa under severe water deficit.

Phosphorus forms in marsh soils with different years of Spartina alterniflora invasion in the Minjiang River estuary, China

LI Yan-zhe, SUN Zhi-gao, MAO Li, CHEN Bing-bing, HU Xing-yun, WANG Xiao-ying, SHI Zi-xiang

2022, 33(4):  1003-1011.  doi:10.13287/j.1001-9332.202204.006

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We examined the effects of Spartina alterniflora invasion on phosphorus forms of marsh soils, based on the method of space-for-time substitution by selecting S. alterniflora marshes with different invasion years (SA₁, 5-6 years; SA₂, 8-10 years; and SA₃, 12-14 years) in Shanyutan of the Minjiang River estuary. The results showed that in marsh soils of different invasion years, the proportion of hardly decomposable phosphorus (HCl-Pi and Residual-P) was the highest (46.4%-46.7%), followed by moderately decomposable phosphorus (NaOH-Pi, NaOH-Po and Sonic-Pi) (40.0%-44.0%), and the easily decomposable phosphorus (Resin-Pi, NaHCO₃-Pi and NaHCO₃-Po) was the lowest (9.5%-13.3%). With increasing invasion years of S. alterniflora, soil phosphorus forms and their spatial distributions were greatly altered. The contents of moderately decomposable phosphorus, hardly decomposable phosphorus, and total phosphorus (TP) generally increased, while easily decomposable phosphorus content generally decreased. Compared with SA₁, the contents of moderately decomposable phosphorus, hardly decomposable phosphorus and TP in SA₂ increased by 11.5%, 9.7% and 10.5%, while those in SA₃ increased by 24.8%, 13.2% and 13.5%, respectively. The distribution of phosphorus forms was greatly altered with increasing invasion years, which was dependent on the variations of key factors such as EC, pH value and grain composition. The implementation of regular mowing activities for S. alterniflora in the Minjiang River estuary in recent years, to some extent, reduced the return of phosphorus from residues to soils and decreased the availability of the easily decomposable phosphorus in soils.

Effects of economic fruit forest planting on the stability of red soil aggregates in the subtropical hilly area

TONG Chen-hui, WANG Hui, TAN Shuai, WEI Ya-fei, HU Ting-fei, ZHANG Xian-deng, LIU Li-hao

2022, 33(4):  1012-1020.  doi:10.13287/j.1001-9332.202204.011

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The stability of aggregates is of great significance to evaluate water and soil environment in regions plan-ting economic fruit forest. We explored the effects of economic fruit forest types on the structure and stability of soil aggregates in the 0-50 cm soil layer from 5-year-old Amygdalus persica, Pyrus sorotina, Citrus reticulata, Camellia oleifera and Actinidia chinensis forests in the hilly area in northern Hunan. The content, distribution characteristics and stability indices of soil aggregates from each economic fruit forest were quantitatively analyzed by the Shavinov method. The results showed that most soil aggregates were mechanically stable, with a minimum content of 92.3%. After wet sieving, the size of water-stable aggregates in the soil from Camellia oleifera forest was mainly >2 mm, accounting for 55.9% of the total aggregates. The 0.25-2 mm aggregates were the dominant particles in the A. persica, P. sorotina, C. reticulata and A. chinensis forest soils, with contributions higher than 43.6%. The mean weight diameter (MWD) and the geometric mean diameter (GMD) of soil aggregates for the five economic fruit forest types ranged from 1.10 to 3.19 mm and 0.61 to 2.28 mm, respectively. Furthermore, the percentages of soil aggregate destruction (PAD) and fractal dimension (D) were in the range of 2.9%-37.3% and 2.30-2.68, respectively. With the increases of soil depth, the stability of soil aggregates from A. persica, C. oleifera and A. chinensis forest soils became worse; MWD and GMD decreased by 1.7%-57.7% and 4.5%-65.8%, respectively; PAD and D increased by 0.4%-17.3% and 1.6%-11.1%, respectively. The effects of economic fruit forest types on the stability of soil aggregates decreased with increasing soil depth. Based on the stability indices, aggregate stability from five economic fruit forests followed the order of C. oleifera > A. chinensis > P. sorotina > C. reticulata > A. persica. The type of economic fruit forest improved the stability of soil structure mainly by affecting the content of large-size aggregates. In terms of improving the distribution and stability of soil aggregates, it was suggested that C. oleifera should be given the top priority as the economic fruit forest in the subtropical hilly area, followed by A. chinensis. Whereas A. persica planting might reduce the degree of soil agglomeration, thus, the protective measures of soil loss should be considered during planting. Our results could provide theoretical basis and application guidance for the development, utilization, and ecological management of economic fruit forests in subtropical hilly areas.

Effects of large-grained activated humic acid fertilizer on soil aggregates and organic carbon in apple orchard soil

LIU Yan, TANG Ya-fu, YANG Yue-chao, JIANG Yuan-mao, CHENG Dong-dong

2022, 33(4):  1021-1026.  doi:10.13287/j.1001-9332.202204.012

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The new large-grained activated humic acid fertilizer (LAF) can significantly reduce the amount of chemical fertilizer application and stable fruit yield. Understanding its impacts on soil aggregates and organic carbon is an important basis for revealing its role in driving soil structure of apple orchard. There were four LAF treatments: LAF₁ (full fertilization, fertilization period and mass ratio (the same below), germination stage: fruit expansion stage: maturity stage=3:4:3), LAF₂ (full fertilization, germination stage: fruit expansion stage: maturity stage=2:3:5), LAF₃ (fertilizer application reduction by 1/4, germination stage: fruit expansion stage: maturity stage=2:3:5), LAF₄ (fertilizer application reduction by 1/3, germination stage: fruit expansion stage: maturity stage=2:3:5); with no fertilization as control (CK). In a four-year pot experiment, we examined the composition, stabi-lity and organic carbon content of soil aggregates under different fertilization treatments. The results showed that: 1) compared with CK, each treatment of LAF increased the content of >2 mm and 2-0.25 mm aggregate by 53.4%-77.5% and 12.3%-17.0%, respectively. The application of LAF significantly increased the content of soil water stable aggregates, and such effects were positively related with application amount. The content of soil water stable aggregate was the highest in the LAF₁ treatment. 2) There was no significant difference in aggregate content of each particle size among LAF treatments, with the proportion of aggregate content of 2-0.25 mm particle size being the highest. 3) Compared with CK, all LAF treatments significantly increased the average weight diameter (MWD) and geometric mean diameter (GMD), and reduced the fractal dimension (D). LAF₁ treatment had the highest MWD and GMD values, and had the strongest effect on the stability of soil aggregates. 4) Except for LAF₄ treatment, the content of soil organic carbon in other LAF treatments was significantly higher than that in CK, and the content of soil organic carbon in LAF₂ treatment was the highest. All LAF treatments increased the organic carbon content of soil aggregates with each particle size. LAF₁, LAF₂, and LAF₃ treatments significantly increased the organic carbon of aggregates with particle size >2 mm. Particle size >2 mm had the highest contribution to the total organic carbon. The contribution rate of water stable large aggregate organic carbon to total organic carbon of LAF treatment was significantly higher than that of CK, which was all higher than 66.0%, and that of LAF₁ treatment was the highest. In conclusion, the application of LAF enhanced the formation and stability of water stable aggregates and increased organic carbon content of aggregates in apple orchard soil, with the best performance of the full application. The application of LAF could be used as an effective measure to improve soil structure and fertility in apple orchard.

Effects of biochar combined with nitrification/urease inhibitors on soil active nitrogen emissions from subtropical paddy soils

HUANG Jia-jia, HE Li-li, LIU Yu-xue, LYU Hao-hao, WANG Yu-ying, CHEN Zhao-ming, CHEN Jin-yuan, YANG Sheng-mao

2022, 33(4):  1027-1036.  doi:10.13287/j.1001-9332.202204.017

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We examined the effects of biochar and urease inhibitors/nitrification inhibitors on nitrification process, ammonia and N₂O emission in subtropical soil, and determined the best combination of biochar with nitrification and urease inhibitors. This work could provide a theoretical basis for the mitigation of the negative environmental risk caused by reactive nitrogen gas in the application of nitrogen fertilizer. A indoor aerobic culture test was conducted with seven treatments [urea+biochar (NB), urea+nitrification inhibitor (N+NI), urea+urease inhibitor (N+UI), urea+nitrification inhibitor+urease inhibitor (N+NIUI), urea+nitrification inhibitor+biochar (NB+NI), urea+urease inhibitor+biochar (NB+UI), urea+nitrification inhibitor+urease inhibitor+biochar (NB+NIUI)] and urea (N) as the control. The dynamics of soil inorganic nitrogen content, N₂O emission and the volatility of ammonia volatilization were observed under combined application of biochar with urease inhibitor (NBPT)/nitrification inhibitor (DMPP). The results showed that:1)Compared to the control (5.11 mg N·kg^-1·d^-1) during the incubation period, NB treatment significantly increased therate constant of nitrification by 33.9%, and N+NI treatment significantly reduced the nitrification rate constant by 22.9%. NB treatment significantly increased the abundance of ammonia oxidizing bacteria (AOB) by 56.0%. 2) Compared with N treatment, N+NI and NB+NI treatments signi-ficantly enhanced the cumulative emission of NH₃ by 49%. The N+UI treatment reduced the cumulative loss of NH₃. The inhibition effect of NB+UI treatment was more significant. 3) The emission rate of N₂O was highest in the first 10 days after fertilization. The N₂O emission under NB treatment was the earliest, and that of N treatment was the highest (5.87 μg·kg^-1·h^-1). The combined application of DMPP and NBPT performed the best in reducing soil N₂O emission. We estimated global warming potential (GWP) of the direct N₂O and indirect N₂O (NH₃) emissions. Compared with N treatments, N+NI and NB+NI treatments increased the GWP by 34.8% and 40.9%, respectively. While the NB and NB+UI treatments significantly reduced the GWP by 45.9% and 60.5%, the combination of biochar and urease inhibitor had the best effect on reduction of GWP of soil active nitrogen emissions.

Differences in uptake, utilization and loss of nitrogen and phosphorus in a Chinese double rice cropping system under different irrigation and fertilization managements

WANG Li-min, HUANG Dong-feng, ZHANG Bing-ya, PAN Zhu-cai

2022, 33(4):  1037-1044.  doi:10.13287/j.1001-9332.202204.016

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In order to optimize water and fertilizer use in the double-cropping rice in eastern Fujian Province, a field runoff plot experiment was conducted to investigate rice yield, nutrient uptake, and runoff losses of N (nitrogen) and P (phosphorus) in the T₀(no chemical fertilization with traditional flooding irrigation), T₁(common chemical fertilizer of 273 kg N·hm^-2, 59 kg P·hm^-2, and 112 kg K·hm^-2 combined with traditional flooding irrigation), T₂(chemical fertilizer of 240 kg N·hm^-2, 52 kg P·hm^-2, and 198 kg K·hm^-2 combined with traditional flooding irrigation) and T₃(chemical fertilizer combined with shallow intermittent irrigation) treatments. Results showed that early rice grain yield in the T₁, T₂ and T₃ treatments significantly increased by 0.7, 1.0, 1.1 times, late rice grain yield significantly increased by 0.9, 1.1, 1.0 times compared to that in the T₀ treatment, respectively. The T₁, T₂ and T₃ treatments significantly increased the uptake of N and P in aboveground parts of the plants, especially in grains. The T₁, T₂ and T₃ treatments significantly increased N uptake by 1.1, 1.2, 1.2 times, increased P uptake by 0.9, 1.4, 1.6 times in early-season grains, and significantly increased N uptake by 0.8, 1.0, 1.0 times, increased P uptake by 0.7, 0.9, 0.9 times in late-season grains, compared to T₀, respectively. Furthermore, T₃ increased agronomic N use efficiency (AEN) and agronomic P use efficiency (AEP) by 71.1% and 69.2% in early rice plants, increased AEN and AEP by 26.4% and 25.0% in late rice plants, whereas T₃ decreased total dissolved N (DN) by 16.0% in comparison with T₁. Dissolved inorganic N loss in surface runoff occurred mainly in the form of NO₃^--N (nitrate N) under different water and fertilizer regimes. However, there were no significant differences in AEN and AEP between T₂ and T₃ treatments. These findings suggested that optimal applications of water and fertilizers (T₃) might increase N and P uptake in rice plants, maintain yield, and reduce N loss, especially in the form of NO₃^--N in surface water from early rice field. In general, this study could provide theoretical support for the optimization of irrigation and fertilization and for the control of N and P non-point source pollution from the double cropping rice paddy fields in eastern Fujian Province.

Dynamics of carbon and nitrogen balance during leaf senescence of maize seedlings induced by low nitrogen stress

WANG Ning, SHI Zhao-kang, XU Shi-ying, YIN Feng-ru, WANG Wei-jie, FENG Wan-jun

2022, 33(4):  1045-1054.  doi:10.13287/j.1001-9332.202204.034

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Timing of leaf senescence is important to ensure maize yield. In this study, we investigated the dynamics of carbon and nitrogen balance during leaf senescence in two maize inbred lines PH6WC and PH4CV under normal (4 mmol·L^-1, CK) and low nitrogen (0.04 mmol·L^-1, LN) treatments. Leaf phenotype, photosynthetic characteristics, nitrogen and sugar contents, and carbon to nitrogen ratio of the second and third leaves were analyzed after 2, 4, 6 and 8 days of cultivation. Results showed that leaf size, biomass, relative chlorophyll content, net photosynthetic rate, soluble sugar content, and starch content of the second and third leaves were decreased, while nitrogen production capacity was increased under low nitrogen treatment compared to the control, with the changes of the second leaf being earlier than that of the third leaf. For all the leaf traits, the variation scales of PH6WC were larger than that of PH4CV under low nitrogen stress, and only the C/N ratio in the seedling leaves was significantly increased. In addition, leaf senescence of PH4CV was slower than PH6WC due to its stronger ability in maintaining carbon and nitrogen balance. In conclusion, low nitrogen could induce leaf senescence of maize seedlings. High C/N ratio could promote leaf senescence. There are significant differences in carbon and nitrogen balance ability of seedling leaves between two maize genotypes under low nitrogen stress.

Effects of saline-water furrow irrigation on the stability of soil water-stable aggregates in cotton field

BI Yan-peng, ZHENG Chun-lian, DANG Hong-kai, CAO Cai-yun, LI Ke-jiang, MA Jun-yong, WANG He, ZHANG Jun-peng

2022, 33(4):  1055-1062.  doi:10.13287/j.1001-9332.202204.002

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It is of great importance to explore the effects of saline-water furrow irrigation on soil water-stable aggregates for safe and efficient utilization of saline water resources. We conducted a long-term cotton experiment with six levels of saline-water furrow irrigation (1, 2, 4, 6, 8, 10 g·L^-1) since 2006 and analyzed the variations of soil salinity and water-stable aggregates in the 10th and 15th years under saline irrigation. The results showed that soil salinity in the 0-30 cm layer at the ditch increased with increasing salinity level of irrigation water. There were significant differences between the 6, 8, 10 g·L^-1 and 1 g·L^-1 treatments. Soil salinity in each treatment increased gradually with increasing soil depth. Saline-water furrow irrigation tended to reduce the stability of soil water-stable aggregates. When the salinity level of the irrigation water was ≥6 g·L^-1, the mass fraction of macroaggregates (>0.25 mm), the mean weight diameter and geometric mean diameter of water-stable aggregates significantly decreased. In contrast, the fractal dimension and mean weight specific surface area increased significantly. The stability of soil water-stable aggregates decreased with soil depth in all treatments. Under the condition of saline-water furrow irrigation for several years, there was no accumulation of soil salinity and instability of water-stable aggregates in the 0-30 cm soil layer at the ditch with each passing year. With the irrigation scheduling of this study, saline-water furrow irrigation with salinity ≤4 g·L^-1 did not affect soil salinity and water-stable aggregate stability of cotton field in this area.

Effects of brackish water irrigation on grain quality characteristics and yield of winter wheat

MA Yu-zhao, DANG Hong-kai, LI Ke-jiang, ZHENG Chun-lian, CAO Cai-yun, ZHANG Jun-peng, LI Quan-qi

2022, 33(4):  1063-1068.  doi:10.13287/j.1001-9332.202204.003

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Brackish water resource is widely distributed in the North China Plain, which has not been effectively utilized. Using brackish water for irrigation can alleviate water resource conflict in the well-irrigated area and solve the problem of groundwater over-exploitation of the North China Plain. A long-term experiment (since 2006) was conducted to investigate the effects of brackish water irrigation on the quality and yield of winter wheat in the North China Plain. There were five salinity degrees of irrigation water, i.e. 1, 2, 4, 6, and 8 g·L^-1, respectively. The results showed that higher salinity degree of irrigation water (4-8 g·L^-1) significantly increased water absorption, development time, sedimentation, wet gluten content, and protein content, but decreased the stabilization time, flour yield, and gluten index. There was no significant difference between the treatments of 1 g·L^-1 and 2 g·L^-1 on grain yield and yield components, but the treatment of 2 g·L^-1 significantly improved grain quality, including water absorption, development time, sedimentation, wet gluten, and protein content. Higher salinity degree of irrigation water (4-8 g·L^-1) treatments significantly decreased spike number (44.0%-60.7%) and grain yield (35.6%-64.7%), compared with 1 g·L^-1 treatment. Results of principal component analysis showed that 2 g·L^-1 treatment had the best overall effect with no significant decrease in grain yield and quality of grain. This study could provide theoretical basis and technical support for use of brackish water in the North China Plain.

Effects of the amount of biochar application on agronomic traits and nutrient content of soybean

LIU Jian-ping, LONG Ying, LI Xiao-hong

2022, 33(4):  1069-1073.  doi:10.13287/j.1001-9332.202204.005

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A pot experiment was conducted at the Shaoyang University test base in May 2020, with Xudou 18 as the research object. We investigated the growth and development as well as the agronomic traits and nutrient content across a gradient of 0 (CK), 5, 10, 20, and 40 g·kg^-1 of biochar addition. The results showed that compared with CK, the biochar application significantly affected growth dynamic, plant height, number of effective pods per plant, 100-grain weight, and leaf and stem dry weights of soybean plants, and the contents of protein, crude fat and isoflavone in soybean seeds. At the application rate of 20 g·kg^-1, the germination rate of soybean was the highest, the growth period was the shortest, the number of effective pods per plant was the highest, the 100-grain weight was the largest, and the contents of protein, crude fat, and isoflavone were the highest in the seeds. When biochar application reached 40 g·kg^-1, the plant height of soybean was the highest with extended vegetative growth and delayed maturity, whereas the effective pods per plant and 100-grain weight was reduced compared to that with 20 g·kg^-1 application. In conclusion, the effects of biochar addition on agronomic traits and nutrient content of soybean varied with application amount, with 20 g·kg^-1 being the optimal under the test condition.

Spectral characteristics of dissolved organic matter and its environmental responses across successional stages in a glacier retreat area

LIANG Zi-yan, LI Xiao-ming, WANG Tao, DUAN Bao-li, LEI Yan-bao

2022, 33(4):  1074-1082.  doi:10.13287/j.1001-9332.202204.032

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Dissolved organic matter (DOM), the most active type of soil organic matter, plays a key role in soil biogeochemical cycling. Therefore, exploring the source, composition, environmental response, and accumulation mechanism of DOM during vegetation succession has great significance for predicting soil carbon cycling. In this study, DOM was extracted from topsoil and subsoil at plots after 12, 30, 40, 50, 80, and 120 years of primary succession along the Hailuogou Glacier retreat area. The concentrations and spectral characteristics of DOM were analyzed via a combination of elemental analysis, ultraviolet-visible spectroscopy, and three-dimensional fluorescence excitation-emission matrix spectroscopy. The results showed that concentrations of soil dissolved organic carbon and dissolved organic nitrogen of both topsoil and subsoil increased significantly during vegetation succession. Along the chronosequence, the protein-like components and optical indices were significantly enhanced, humic-like components and the optical indices decreased, the aromaticity degree of DOM increased first and then decreased. Soil pH and NH₄⁺-N content explained 62.2% of the total variation of surface soil DOM components, while soil moisture and pH explained 64.3% of that of subsurface soil DOM, indicating that environmental conditions were key factors affecting the concentrations and composition of soil DOM in the Hailuogou Glacier retreat area.

Influence of landscape pattern on elevation effect of δ¹⁸O in surface water in Hani Terrace

LIU Cheng-jing, JIAO Yuan-mei, XU Qiu-e, YANG Yan-fen, DING Yin-ping, LIU Zhi-lin

2022, 33(4):  1083-1090.  doi:10.13287/j.1001-9332.202204.010

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With the Quanfuzhuang River basin located at Hani Rice Terrace core region as study area, we analyzed the isotopic composition and the effects of 12 surface water sampling sites for the forest landscape type and terrace landscape type from May 2015 to April 2016. The results showed that: 1) For the variation of isotope composition, both the average value and the variation range of δ¹⁸O in surface water under forest patches were smaller than that under terrace patches. 2) The overall elevation effect of the hydrogen and oxygen stable isotopes in surface water was obvious, except that in August and March, which could be expressed as the linear regression equation δ¹⁸O=-0.012H+13.84 (r=-0.83, n=12). 3) The altitude gradient of δ¹⁸O in surface water was -1.2‰·(100 m)^-1, which was not the true altitude gradient affected by precipitation but by landscape gradient of δ¹⁸O in surface water between forest patches and terrace patches. 4) Under the “Forest-Terrace” landscape pattern, the δ¹⁸O differences in surface water between forest patches and terrace patches enhanced the elevation effect. Therefore, when landscape heterogeneity was strong, isotopic effect was strengthened, even with opposite isotope effect.

Effects of moso bamboo (Phyllostachys edulis) expansion on soil microbial community in evergreen broad-leaved forest

MA Xin-ru, ZHENG Xu-li, ZHENG Chun-ying, HU Yu-ting, QIN Hua, CHEN Jun-hui, XU Qiu-fang, LIANG Chen-fei

2022, 33(4):  1091-1098.  doi:10.13287/j.1001-9332.202204.030

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The special eco-physiological characteristics of moso bamboo (Phyllostachys edulis) facilitate their fast invasion in nature ecosystems. The widespread expansion of moso bamboo causes degradation of adjacent forest ecosystem and change of landscape, as well as soil properties and microbial community composition. However, how moso bamboo expansion affects soil microbial composition is far from fully understood. Herein, we selected four moso bamboo expansion transects with three forest types at the Anji Lingfeng temple forest farm, Zhejiang Province, including evergreen broadleaved forest (BLF), mixed P. edulis and broadleaved forest (MEF) and P. edulis forest (PEF). We examined the effects of moso bamboo expansion on soil properties and soil microbial phospholipid fatty acids (PLFAs). Our results showed that soil pH was higher in moso bamboo forest than in MEF and BLF by 0.37 and 0.32 unit. In contrast, soil organic carbon, ammonium, and nitrate contents significantly decreased. Biomass of soil microbial groups displayed a decreasing trend except arbuscular mycorrhizal fungi, and the microbial richness index (SR) and diversity index (H) decreased significantly. In summary, moso bamboo expansion affected soil nutrient and carbon inputs, which was an important factor affecting soil microbial community structure. Results of redundancy analysis showed that changes of soil organic carbon and ammonium content were the main factors driving soil microbial community.

Effects of reducing chemical fertilizers combined with organic fertilizers on soil microbial community in litchi orchards

AN Xiang-rui, JIANG Shang-tao, XIE Chang-yan, XU Yang-chun, DONG Cai-xia, SHEN Qi-rong

2022, 33(4):  1099-1108.  doi:10.13287/j.1001-9332.202204.031

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Organic fertilizer application can replace a part of chemical fertilizer (CF) to improve the quality and efficiency of litchi production. To further explore the soil microbiological mechanism, with 19-year-old ‘Feizixiao' litchi trees as the research objects, we examined the effects of two consecutive years of reduced CF applications (average 21.5% of total nutrients) combined with sheep manure (OF) and bio-organic fertilizers (BIO) on soil microbial diversity, community composition and differential microorganisms. The results showed that reducing the application of chemical fertilizers and combining it with the application of sheep manure and bio-organic fertilizer for two consecutive years could significantly improve yield and quality. The average increase of yield in the two years was 23.1% and 39.0%, respectively. Soil organic matter content and pH increased significantly in response to the combination treatments. Compared to that in the chemical fertilizer treatment, the contents of soil available phosphorus, potassium, calcium, magnesium, iron, manganese, copper, and zinc displayed an increasing trend in the combination treatments. The application of organic fertilizer increased the diversity of bacteria and fungi in rhizosphere soil, but not in non-rhizosphere soil. Both treatments significantly changed soil microbial community structure, increased eutrophic bacterial groups such as Bacteroides, Proteobacteria, and Bacillus phylum, and reduced anatrophic bacterial groups such as Acidobacteria and Chloroflexus. Compared with CF, the relative abundances of MND1 under OF and TK10, Gemmatimonas, Pseudolabrys, Trichoderma and Botryotrichum under BIO were significantly increased, which was positively correlated with yield. In conclusion, reducing CF and applying organic ferti-lizer for two consecutive years could effectively improve soil pH and nutrient availability, increase rhizosphere microbial richness and diversity, change soil microbial community structure, and shape microbial communities being more conducive to yield and quality improvement.

Soil bacterial community characteristics and ecological function prediction of alfalfa and crop rotation systems in the Loess Plateau, Northwest China

WANG Xiao-fei, LUO Zhu-zhu, ZHANG Ren-zhi, NIU Yi-ning, LI Ling-ling, TIAN Jian-xia, SUN Peng-zhou, LIU Jia-he

2022, 33(4):  1109-1117.  doi:10.13287/j.1001-9332.202204.028

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In order to understand the effects of lucerne cropping rotation on the bacterial community of loess soil, a long-term field experiment was conducted in rain-fed agricultural area of Loess Plateau. The cropping systems included continuous lucerne (Medicago sativa, LC), lucerne removed and rotated with spring wheat (Triticum aestivum, L_FW), lucerne removed and rotated with corn (Zea mays, L_FC), lucerne removed and rotated with potato (Solanum tuberosum, LP), and lucerne removed and rotated with continuous millet (Panicum miliaceum, LM). Based on 16S rRNA high-throughput sequencing technology, we investigated soil bacterial community structure and diversity in different cropping systems, and predicted ecological function using PICRUSt method. The results showed that the dominant phyla of loess soil bacteria were Actinomycetes (20.3%-32.0%), Proteobacteria (19.2%-23.0%), Acidobacteria (12.4%-14.2%) and Chloroflexus (11.0%-12.7%). The dominant genus was Bacillus (1.9%) in lucerne-corn system and Pseudarthrobacter (2.5%) in other treatments. Rotation with annual crops decreased the relative abundance of Actinobacteria and increased that of Chloroflexi and Firmicutes. Redundancy analysis showed that the main soil factors driving soil bacterial community structure were nitrate, ammonium, and total nitrogen. PICRUSt function prediction results showed that metabolism (78.6%-79.1%) was the main function of soil bacterial communities in loess soil. Rotation with continued annual crops significantly decreased the abundance of soil bacterial carbohydrate metabolism functional genes, and significantly increased the abundance of functional genes for soil bacterial cofactors and vitamin metabolism, neurodegenerative diseases, and immune system. In conclusion, lucerne removed and rotated with continuous annual crops changed soil bacterial community structure and ecological functions. This study provided theoretical reference to explore succession characteristics of soil bacteria and to select succeeding crops for alfalfa in loess soil.

Community structure and diversity formation of fermentation fungi in traditional Shaoxing Huangjiu

DU Zhen-na, SHAN Zhi-chu, SHEN Chi, CHENG Fei, GUO Huai-yu, ZANG Wei, SUN Jian-qiu, PAN Xing-xiang

2022, 33(4):  1118-1124.  doi:10.13287/j.1001-9332.202204.040

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To reveal the formation mechanism of fungal community and diversity during the production of Shaoxing Huangjiu, we examined fungal communities in the samples of Linfanjiumu, Maiqu and fermentation mash based on Illumina MiSeq PE300 high-throughput sequencing platform. A total of 136000, 215283, 166150, and 143624 sequences were obtained from the samples of Linfanjiumu, Maiqu, initial mash and mature mash, respectively. After clustering, 32, 133, 107 and 84 OUT (operational taxonomic units) were obtained, respectively. The diversity and richness of fungi were in order of Maiqu > initial mash > mature mash > Linfanjiumu. At the level of phylum, Ascomycota were dominant in all samples. At genus level, Saccharomyces was dominant in Linfanjiumu, Aspergillus was dominant in Maiqu, and Saccharomyces and Aspergillus were the dominant fungi in the initial and mature mash. With the extension of the fermentation time, the proportion of Saccharomyces gradually increased in the mash, while other fungal groups including Aspergillus showed a decreasing trend. According to the results of PCoA analysis and similarity cluster analysis, the structure of fungi community in Linfanjiumu, initial mash and mature mash was much similar, while the fungal resources in Maiqu were quite different from other samples. The analysis of fungal community characteristics in the initial mash showed that the Linfanjiumu and Maiqu affected fungal diversity in Shaoxing Huangjiu. The dominant species of saccharification and fermentation starter (Linfanjiumu and Maiqu) played a leading role in driving community assembly of fermentation fungi.

Barrier effect against Bemisia tabaci and the control of tomato yellow leaf curl virus in a tomato-maize intercropping system

WEI Pei-yao, LI Ying-mei, LIU Chen, REN Ping

2022, 33(4):  1125-1130.  doi:10.13287/j.1001-9332.202204.004

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We examined the barrier effects against Bemisia tabaci and the potential to control the tomato yellow leaf curl virus (TYLCV) of different tomato-maize intercropping modes. Tomatoes (variety Jinshan 511) were planted at a fixed row distance either as a monoculture or together with maize (variety Xianyu 335) at the distances of 10, 20, and 30 cm. We investigated the viral index for TYLCV and the population density of B. tabaci. Compared with tomato monoculture, the natural barrier established by the maize stabilized the growth environment for tomato. When the maize spacing was 10, 20, and 30 cm, the average temperature of tomato plants from 6:00 to 20:00 decreased by 3.01, 2.26, and 1.45 ℃, the average relative humidity increased by 13.0%, 8.8%, and 6.0%, and the mean light intensity reduced by 26.1%, 20.4%, and 14.5%, respectively. The changes of those factors alleviated the adverse environmental conditions (i.e., intense light, high temperature, and lack of moisture) that promote the spread of virus-related diseases during the high-temperature period of the day, with the most effective planting distance for the maize being 10 cm. Our results suggested that the intercropping of tomato and maize had a barrier effect against B. tabaci and was able to control the TYLCV in tomato. When the planting distance for the maize was 10, 20, and 30 cm, the number of B. tabaci was 88.7%, 82.0%, and 73.9% lower than tomato monoculture, respectively. The TYLCV was inhibited, with the viral disease index being decreased by 67.3%, 59.4%, and 44.5%, respectively. Tomato-maize intercropping was also beneficial for tomato plant growth and fruit set, which could enhance tomato yield. Such effect was strengthened under higher maize density.

Effects of bisphenol A exposure on proteins tyrosine phosphorylation in mammalian sperm

HU Qi-meng, LI Shan-shan, YANG Yu-xin, LI Meng-yu, HE Jian-yun, HE Qun

2022, 33(4):  1131-1136.  doi:10.13287/j.1001-9332.202206.029

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Bisphenol A (BPA) is a synthetic estrogen compound, which widely exists in the environment, interferes with mammalian endocrine and affects the function of reproductive system of males. Taking fresh sperm of boar, 17 ℃ preservation boar sperm, and mouse sperm as test materials, we examined the effects of BPA (0, 0.1,1,10,100 μmol∙L^-1) on proteins tyrosine phosphorylation in sperm and the molecular mechanism by using wes-tern blot (WB) and immunofluorescence techniques coupled to in vitro culture method. The results showed that low BPA concentration (0.1, 1 μmol∙L^-1) markedly accelerated the protein tyrosine phosphorylation of fresh boar capacitated sperm. However, the tyrosine phosphorylation of boar sperm decreased in high BPA concentration (10, 100 μmol∙L^-1). The tyrosine phosphorylation of the mouse sperm raised with the increases of BPA concentration. Moreover, BPA affected different kinds of proteins related to tyrosine phosphorylation modification of porcine and mouse sperm capacitation, suggesting that the effect of BPA exposure on mammalian sperm was species-specific. Furthermore, the results of immunofluorescence showed that the effects of BPA on protein tyrosine phosphorylation in sperm mainly occurred in the middle and principal piece of flagellum.

Using shape analysis to inform variation in otolith morphology with life stages of Dissostichus mawsoni

WEI Lian, QIAN Hu-rui, YANG Dan, SOMHLABA Sobahle, ZHU Guo-ping

2022, 33(4):  1137-1144.  doi:10.13287/j.1001-9332.202204.029

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As the most important domestic fish in the Antarctic Ocean, Antarctic toothfish (Dissostichus mawsoni) has an important ecological role and high commercial value. The otolith morphology of fish species differs across stages of life history. Therefore, otolith shape analysis can be used to infer life history of D. mawsoni. In this study, otoliths from 120 D. mawsoni individuals with four life stages randomly collected from the Ross Sea, Amundsen Sea, Weddell Sea and Lazarev Sea were used to analyze the otolith morphological differences of D. mawsoni at life stages by conventional measurement and elliptical Fourier analysis. The results showed that variation in otolith morphology occurred across life stages. Generally, the morphology of otolith was changed from smooth and low comple-xity to zigzagging and high complexity. The growth rate of otolith along the longitudinal direction was lower than that along the transverse direction. The characteristic parts of otolith, such as antirostrum, changed significantly across life stages. Compared to the linear discriminant analysis (71.9%), the elliptical Fourier analysis had the higher discrimination rate (85.4%), indicating that the elliptical Fourier analysis was more suitable to analyze the otolith morphology of D. mawsoni.

Reviews

Responses of soil respiration to the interaction of rainfall changes and nitrogen deposition: A review

QIN Shu-qi, PENG Qin, DONG Yun-she, QI Yu-chun

2022, 33(4):  1145-1152.  doi:10.13287/j.1001-9332.202204.015

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Soil respiration (R_s), as a key process of carbon cycle in terrestrial ecosystems, has a direct impact on atmospheric CO₂ concentration. How R_s responds to global change factors, such as rainfall changes and increased N deposition, has become a hot and difficult issue in the field of global change. Compared with the responses of R_s to the single factor of rainfall changes or increased N deposition, studying the response of R_s to the interaction of these two factors is more in line with natural environment, which can predict the future changes of soil carbon emission more accurately. At present, the related researches focused on different terrestrial ecosystems all over the world, and revealed the response mechanism from three aspects: soil, microorganism, and plant. Here, the research progress of soil respiration in response to the interaction of rainfall changes and increased N deposition in different terrestrial ecosystems was reviewed from the aspects of R_s and its components, factors related with soil properties, microorganisms and plant, and the deficiencies of current researches, and the research direction to be strengthened in the future were pointed out. Our review would provide a reference for further understanding the response law and the mechanism of soil respiration to the interaction between rainfall changes and increased N deposition.