Table of Content

18 March 2024, Volume 35 Issue 3

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Applicability of the generalized wind profile model over mountainous forests.

PANG Yunchao, GAO Tian, LI Xiufen, ZHAO Tongbin, WANG Xingchang, LI Rongping, YU Fengyuan, QU Shenglin, TENG Dexiong, ZHU Jiaojun

2024, 35(3):  577-586.  doi:10.13287/j.1001-9332.202403.026

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The analytical equation based on Monin-Obukhov (M-O) similarity theory (i.e., wind profile equation) has been adopted since 1970s for using in the prediction of wind vertical profile over flat terrains, which is mature and accurate. However, its applicability over complex terrains remains unknown. This applicability signifies the accuracy of the estimations of aerodynamic parameters for the boundary layer of non-flat terrain, such as zero-displacement height (d) and aerodynamic roughness length (z₀), which will determine the accuracy of frequency correction and source area analysis in calculating carbon, water, and trace gas fluxes based on vorticity covariance method. Therefore, the validation of wind profile model in non-flat terrain is the first step to test whether the flux model needs improvement. We measured three-dimensional wind speed data by using the Ker Towers (three towers in a watershed) at Qingyuan Forest CERN in the Mountainous Region of east Liaoning Province, and compared them with data from Panjin Agricultural Station in the Liaohe Plain, to evaluate the applicability of a generalized wind profile model based on the Monin-Obukhov similarity theory on non-flat terrain. The results showed that the generalized wind profile model could not predict wind speeds accurately of three flux towers separately located in different sites, indicating that wind profile model was not suitable for predicting wind speeds in complex terrains. In the leaf-off and leaf-on periods, the coefficient of determination (R²) between observed and predicted wind speeds ranged from 0.12 to 0.30. Compared to measured values, the standard error of the predicted wind speeds was high up to 2 m·s^-1. The predicted wind speeds were high as twice as field-measured wind speed, indicating substantial overestimation. Nevertheless, this model correctly predicted wind speeds in flat agricultural landscape in Panjin Agricultural Station. The R² between observed wind speeds and predicted wind speed ranged from 0.90 to 0.93. The standard error between observed and predicted values was only 0.5 m·s^-1. Results of the F-test showed that the root-mean-square error of the observed and predicted wind speeds in each secondary forest complex terrain was much greater than that in flat agricultural landscape. Terrain was the primary factor affecting the applicability of wind profile model, followed by seasonality (leaf or leafless canopy). The wind profile model was not applicable to the boundary-layer flows over forest canopies in complex terrains, because the d was underestimated or both the d and z₀ were underestimated, resulting in inaccurate estimation of aerodynamic height.

Stem moisture content prediction model for Larix olgensis based on beta regression.

CAO Huayan, MIAO Zheng, HAO Yuanshuo, DONG Lihu

2024, 35(3):  587-596.  doi:10.13287/j.1001-9332.202403.001

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To investigate the longitudinal variation patterns of sapwood, heartwood, bark and stem moisture content along the trunk of artificial Larix olgensis, we constructed mixed effect models of moisture content based on beta regression by combining the effects of sampling plot and sample trees. We used two sampling schemes to calibrate the model, without limiting the relative height (Scheme Ⅰ) and with a limiting height of less than 2 m (Scheme II). The results showed that sapwood and stem moisture content increased gradually along the trunk, heartwood moisture content decreased slightly and then increased along the trunk, and bark moisture content increased along the trunk and then levelled off before increasing. Relative height, height to crown base, stand area at breast height per hectare, age, and stand dominant height were main factors driving moisture content of L. olgensis. Scheme Ⅰ showed the stable prediction accuracy when randomly sampling moisture content measurements from 2-3 discs to calibrate the model, with the mean absolute percentage error (MAPE) of up to 7.2% for stem moisture content (randomly selected 2 discs), and the MAPE of up to 7.4%, 10.5% and 10.5% for sapwood, heartwood and bark moisture content (randomly selected 3 discs), respectively. Scheme Ⅱ was appropriate when sampling moisture content measurements from discs of 1.3 and 2 m height and the MAPE of sapwood, heartwood, bark and stem moisture content reached 7.8%, 11.0%, 10.4% and 7.1%, respectively. The prediction accuracies of all mixed effect beta regression models were better than the base model. The two-level mixed effect beta regression models, considering both plot effect and tree effect, would be suitable for predicting moisture content of each part of L. olgensis well.

Relationship between leaf vein traits of three dominant Quercus species and ecological factors in the Qinling Mountains, China

SUN Jingyi, HUANG Ruizhi, WANG Qi, ZHAO Yipei, YANG Shaowei, CHENG Xiangfen, LIU Jianfeng

2024, 35(3):  597-605.  doi:10.13287/j.1001-9332.202403.004

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We investigated the inter- and intra-species differences of leaf vein traits of three dominant Quercus species, Q. wutaishanica, Q. aliena var. acutiserrata, and Q. variabilis of Niubeiling (subtropical humid climate) and Taohuagou (warm temperate semi-humid climate), located in the eastern and western Qinling Mountains. The nine examined leaf vein traits included primary leaf vein width, secondary leaf vein width, mean fine vein width, primary vein density, fine vein density, vein areole diameter, areole density, 3D fine vein surface area, and fine vein volume. We further elucidated the influencing mechanisms and regulatory pathways of biotic and abiotic factors on leaf vein traits. The results showed that species identity had significant effects on eight out of nine leaf vein traits except 3D fine vein surface area, while habitat had significant effects on primary leaf vein width, secondary leaf vein width, vein areole diameter, fine vein density, and areole density. Altitude had significant effects on primary vein density, mean fine vein width, vein areole diameter, fine vein density and areole density. Habitat, tree species identity, and altitude had significantly interactive effects on primary leaf vein density, 3D fine vein surface area, and fine vein volume. There were significant differences in primary leaf vein width, mean fine vein width, areole density, 3D fine vein surface area, fine vein volume, primary vein density of Q. wutaishanica between the two studied habitats, but the differences were only found in secondary leaf vein width and areole density of Q. aliena var. acutiserrata and Q. variabilis. The examined leaf vein traits were influenced both by biotic and abiotic factors, with varying effect sizes. Among the biotic factors, petiole length, leaf length and width ratio had strong effect on leaf vein traits. Among the abiotic factors, climatic and soil factors had high effect size on vein traits, with the former being higher than the latter. Leaf vein traits were affected directly by biotic factors, but indirectly by abiotic factors (soil and climatic factors) via regulating biotic factors (leaf stoichiometry and leaf phenotypic traits).

Responses of leaf traits to altitude in Quercus aquifolioides and Sorbus rehderiana on the eastern edge of the Qinghai-Tibet Plateau, China

XING Hongshuang, FENG Qiuhong, SHI Zuomin, LIU Shun, XU Gexi, CHEN Jian, GONG Shanshan

2024, 35(3):  606-614.  doi:10.13287/j.1001-9332.202403.003

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As the most senstitive plant organs to environmental changes, leaves serve as crucial indicators of plant survival strategies. We measured the morphology, anatomical traits, gas exchange parameters, and chlorophyll fluorescence parameters of Quercus aquifolioides (evergreen broad-leaved) and Sorbus rehderiana (deciduous broad-leaved) at altitudes of 2600, 2800, 3000, 3200 and 3400 m on the eastern edge of the Qinghai-Tibet Plateau, China. We explored the similarity and difference in their responses to altitude change and the ecological adaptation strategy. The results showed that as the altitude increased, leaf dry matter content of Q. aquifolioides decreased, that of S. rehderiana increased, leaf size for both species gradually decreased, and the palisade coefficient of Q. aquifolioides showed a decreasing trend, contrasting with the increasing trend in S. rehderiana. As the altitude increased, the thickness of leaves, palisade tissue, spongy tissue, upper epidermis, and lower epidermis of both species increased significantly, with the increment of 22.4%, 4.9%, 45.1%, 23.3%, 19.6%, and 28.2%, 46.9%, 8.9%, 25.9%, 20.8% at altitude of 3400 m, respectively, compared with the altitude of 2600 m. The gas exchange and chlorophyll fluorescence parameters of S. rehderiana significantly increased with increasing altitude, while Q. aquifolioides showed the opposite trend. Leaf anatomical traits, gas exchange, and chlorophyll fluorescence parameters of both species displayed considerable plasticity. There were significant correlations among most leaf traits and between leaf traits and altitude. The survival strategy of Q. aquifolioides was more conservative in response to altitude changes, while that of S. rehderiana was more active. Both species adapted to different altitudes by adjusting their own traits.

Soil C:N:P stoichiometry in rhizosphere and non-rhizosphere of Pinus sylvestris var. mongolica forests

LIU Yilin, REN Yue, GAO Guanglei, DING Guodong, ZHANG Ying, LIU Ye

2024, 35(3):  615-621.  doi:10.13287/j.1001-9332.202403.005

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The aim of this study was to reveal the stoichiometric characteristics of carbon, nitrogen and phosphorus in rhizosphere and non-rhizosphere soils of Pinus sylvestris var. mongolica in the Hulunbuir desert. We investigated the contents and stoichiometry of organic carbon, total nitrogen, and total phosphorus contents of rhizosphere and non-rhizosphere soils across different stand ages (28, 37 and 46 a) of P. sylvestris var. mongolica plantations, with P. sylvestris var. mongolica natural forest as the control. We analyzed the correlation between soils properties and soil stoichiometry. The results showed that rhizosphere effect significantly affected soil N:P, and stand age significantly affected soil organic carbon content in P. sylvestris var. mongolica plantation. Soil organic carbon content in plantation was significantly lower than that in natural forest. Soil organic carbon and total nitrogen contents of plantations in both rhizosphere and non-rhizosphere soils firstly decreased and then increased with increasing stand age, while total phosphorus firstly increased and then decreased in rhizosphere soils, and firstly decreased and then increased in non-rhizosphere soils. There was significant positive correlations between C:N and C:P in rhizosphere soils but not in non-rhizosphere soils, suggesting that higher synergistic rhizosphere soil N and P limitation. The mean N:P values of rhizosphere and non-rhizosphere soils were 4.98 and 8.40, respectively, indicating that the growth of P. sylvestris var. mongolica was restricted by soil N and the rhizosphere soils were more N-restricted. The C:N:P stoichiometry of rhizosphere and non-rhizosphere soils were significantly influenced by soil properties, with available phosphorus being the most important driver. The growth of P. sylvestris var. mongolica was limited by N in the Hulunbuir desert, and root system played an obvious role in enriching and maintaining soil nutrients. It was recommended that soil nitrogen should be supplemented appropriately during the growth stage of P. sylvestris var. mongolica plantation, and phosphorus should be supplemented appropriately according to the synergistic nature of nitrogen and phosphorus limitation.

Characteristics of soil nitrogen and phosphorus fractions and microbial traits with increasing stand age in two-layered Cunninghumia lanceolata + Phoebe bournei plantations

HONG Xuansheng, WANG Zongxing, XU Qingfu, QIU Yongbin, CHENG Xiangrong

2024, 35(3):  622-630.  doi:10.13287/j.1001-9332.202403.002

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Soil nitrogen and phosphorus are two key elements limiting tree growth in subtropical areas. Understanding the regulation of soil microorganisms on nitrogen and phosphorus nutrition is beneficial to reveal maintenance mechanism of soil fertility in plantations. We analyzed the characteristics of soil nitrogen and phosphorus fractions, soil microbial community composition and function, and their relationship across three stands of two-layered Cunninghumia lanceolata + Phoebe bournei with different ages (4, 7 and 11 a) and the pure C. lanceolata plantation. The results showed that the contents of most soil phosphorus fractions increased with increasing two-layered stand age. The increase in active phosphorus fractions with increasing stand age was dominated by the inorganic phosphorus (9.9%-159.0%), while the stable phosphorus was dominated by the organic phosphorus (7.1%-328.4%). The content of soil inorganic and organic nitrogen also increased with increasing two-layered stand age, with NH₄⁺-N and acid hydrolyzed ammonium N contents showing the strongest enhancement, by 152.9% and 80.2%, respectively. With the increase of stand age, the composition and functional groups of bacterial and fungal communities were significantly different, and the relative abundance of some dominant microbial genera (such as Acidothermus, Saitozyma and Mortierella) increased. The relative abundance of phosphorus solubilization and mineralization function genes, nitrogen nitrification function and aerobic ammonia oxidation function genes tended to increase. The functional taxa of fungi explained 48.9% variation of different phosphorus fractions. The conversion of pure plantations to two-layered mixed plantation affected soil phosphorus fractions transformation via changing the functional groups of saprophytes (litter saprophytes and soil saprophytes). Changes in fungal community composition explained 45.0% variation of different nitrogen fractions. Some key genera (e.g., Saitozyma and Mortierella) play a key role in promoting soil nitrogen transformation and accumulation. Therefore, the conversion of pure C. lanceolata plantation to two-layered C. lanceolata + P. bournei plantation was conducive to improving soil nitrogen and phosphorus availability. Bacteria and fungi played important roles in the transformation process of soil nitrogen and phosphorus forms, with greater contribution of soil fungi.

Short-term responses of soil enzyme activities and stoichiometry to litter input in Castanopsis carlesii and Cunninghamia lanceolata plantations

AI Ling, WU Fuzhong, FAN Xuebo, YANG Jing, WU Qiuxia, ZHU Jingjing, NI Xiangyin

2024, 35(3):  631-638.  doi:10.13287/j.1001-9332.202403.014

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Litter input triggers the secretion of soil extracellular enzymes and facilitates the release of carbon (C), nitrogen (N), and phosphorus (P) from decomposing litter. However, how soil extracellular enzyme activities were controlled by litter input with various substrates is not fully understood. We examined the activities and stoichiometry of five enzymes including β-1,4-glucosidase, β-D-cellobiosidase, β-1,4-N-acetyl-glucosaminidase, leucine aminopeptidase and acidic phosphatase (AP) with and without litter input in 10-year-old Castanopsis carlesii and Cunninghamia lanceolata plantations monthly during April to August, in October, and in December 2021 by using an in situ microcosm experiment. The results showed that: 1) There was no significant effect of short-term litter input on soil enzyme activity, stoichiometry, and vector properties in C. carlesii plantation. In contrast, short-term litter input significantly increased the AP activity by 1.7% in May and decreased the enzymatic C/N ratio by 3.8% in August, and decreased enzymatic C/P and N/P ratios by 11.7% and 10.3%, respectively, in October in C. lanceolata plantation. Meanwhile, litter input increased the soil enzymatic vector angle to 53.8° in October in C. lanceolata plantations, suggesting a significant P limitation for soil microorganisms. 2) Results from partial least squares regression analyses showed that soil dissolved organic matter and microbial biomass C and N were the primary factors in explaining the responses of soil enzymatic activity to short-term litter input in both plantations. Overall, input of low-quality (high C/N) litter stimulates the secretion of soil extracellular enzymes and accelerates litter decomposition. There is a P limitation for soil microorganisms in the study area.

Changes of soil nutrients and organic carbon fractions in Caragana korshinskii forests with different restoration years in mountainous areas of southern Ningxia, China

ZHANG Yuhan, LI Yao, ZHOU Yue, CHEN Yuanjia, AN Shaoshan

2024, 35(3):  639-647.  doi:10.13287/j.1001-9332.202403.018

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Vegetation restoration can effectively enhance soil quality and soil organic carbon (SOC) sequestration. In this study, the distribution characteristics of soil nutrients and SOC along soil profile (0-100 cm), and their responses to restoration years (16, 28, 38 years) were studied in Caragana korshinskii plantations in the southern mountainous area of Ningxia, compared with cropland and natural grassland. The results showed that: 1) the contents of SOC, soil total nitrogen (TN), total phosphorus (TP), particulate organic carbon (POC), mineral-associated organic carbon (MAOC) and the proportion of particulate organic carbon to total organic carbon (POC/SOC) all decreased with increasing soil depth. The ratio of mineral-associated organic carbon to total organic carbon (MAOC/SOC) exhibited an opposite trend. 2) The contents of SOC, TN, TP, C:P, N:P, POC and MAOC gra-dually decreased as the restoration years increased. However, the C:N ratio showed no significant change. The POC/SOC ratio initially increased and then decreased, while the MAOC/SOC ratio decreased initially and then increased. 3) In three different types of vegetation, POC, MAOC, and SOC showed a highly significant positive linear correlation, with the increase in SOC mainly depended on the increase in MAOC. The SOC, TN, TP, POC and MAOC contents in natural grassland and C. korshinskii plantations were significantly higher than those in cropland. In conclusion, soil nutrients and POC and MAOC contents of C. korshinskii plantations gradually decreased with the increases in restoration years. However, when compared with cropland, natural grassland and C. korshinskii plantations demonstrated a greater capacity to maintain and enhance soil nutrient and carbon storage.

Carbon wet deposition flux and river carbon output in a forest watershed in permafrost region of the Da Xing’an Mountains

LIU Huan, YANG Xiaochen, CAI Yushan, CUI Yang, DUAN Liangliang

2024, 35(3):  648-658.  doi:10.13287/j.1001-9332.202403.010

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Carbon wet deposition and river carbon output in river basins are important components of global carbon cycle. The assessment of both properties is of great significance for regional carbon budget. However, research on these topics in high-latitude permafrost regions in China is still lacking. We conducted dynamic monitoring of carbon wet deposition and carbon output in the river from May 28th to October 30th, 2022, in Laoyeling watershed, a typical forested watershed in the Da Xing’an Mountains permafrost region. We analyzed the variations of carbon component concentrations and fluxes in precipitation and river water, and estimated the contribution of carbon wet deposition to carbon output in the watershed. The results showed that wet deposition fluxes of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and total dissolved carbon (TDC) in the Laoyeling watershed were 1354.86, 684.59, and 2039.45 kg·km^-2, respectively. The fluxes of DOC, DIC, TDC, particulate organic carbon (POC), particulate inorganic carbon (PIC), and total carbon (TC) in the river were 601.75, 1977.30, 2579.05, 125.13, 21.99, and 2726.17 kg·km^-2, respectively. The contribution of TDC wet deposition to the river TDC output was 9941.89 kg, accounting for 17.6% of total output. The DIC concentration in the river showed significant seasonal differences, with increased runoff resulting from precipitation leading to a decrease in DIC concentration in the river and showing a clear dilution effect, while the concentrations of DOC, POC, and PIC increased, mainly due to erosion effect. In conclusion, carbon wet deposition flux in the Laoyeling watershed was mainly determined by precipitation, and its contribution to river carbon output was relatively small compared to other factor. Runoff was the dominant factor affecting river carbon output. The results would provide important insights into carbon cycling and carbon budget balance in permafrost regions under climate change.

Phenological characteristics of net ecosystem carbon exchange of Stipa krylovii steppe in Inner Mongolia, China and its remote sensing monitoring

WANG Jin, ZHOU Guangsheng, HE Qijin, ZHOU Li

2024, 35(3):  659-668.  doi:10.13287/j.1001-9332.202403.025

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To accurately monitor the phenology of net ecosystem carbon exchange (NEE) in grasslands with remote sensing, we analyzed the variations in NEE and its phenology in the Stipa krylovii steppe and discussed the remote sensing vegetation index thresholds for NEE phenology, with the observational data from the Inner Mongolia Xilinhot National Climate Observatory’s eddy covariance system and meteorological gradient observation system during 2018-2021, as well as Sentinel-2 satellite data from January 1, 2018 to December 31, 2021. Results showed that, from 2018 to 2021, NEE exhibited seasonal variations, with carbon sequestration occurring from April to October and carbon emission in other months, resulting in an overall carbon sink. The average Julian days for the start date (SCUP) and the end date (ECUP) of carbon uptake period were the 95^th and 259^th days, respectively, with an average carbon uptake period lasting 165 days. Photosynthetically active radiation showed a negative correlation with daily NEE, contributing to carbon absorption of grasslands. The optimal threshold for capturing SCUP was a 10% threshold of the red-edge chlorophyll index, while the normalized difference vegetation index effectively reflected ECUP with a threshold of 75%. These findings would provide a basis for remote sensing monitoring of grassland carbon source-sink dynamics.

Prediction on the changes in potential suitable areas for mangroves along the coast of Guangxi and the threat from Spartina alterniflora invasion

HU Ailian, YANG Juan, LIU Baolin, ZOU Yu

2024, 35(3):  669-677.  doi:10.13287/j.1001-9332.202403.024

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As one of the important blue carbon pools in tropical and subtropical intertidal zones, mangroves are widely distributed along the coast of Guangxi in China. To deeply explore the variations of potential suitable habitats for mangroves in China under the background of climate change, based on remote sensing interpretation data of coastal wetlands in Guangxi, global marine environment and bioclimatic environment data in 2021, we constructed a maximum entropy habitat distribution model to simulate the spatial distribution of potential suitable areas for mangroves and the invasive species, Spartina alterniflora, along the coast of Guangxi, and predicted the patterns under extreme climate change scenarios (SSP5-8.5). The results showed that the interpreted area of mangrove forests along the coastline of Guangxi was 9136.7 hm² in 2021, while the predicted area of potential suitable habitat area was 55955.9 hm². Current distribution area of mangroves had basically covered its potential high suitability area and nearly 10% of the moderate suitability area. The current area of S. alterniflora was 1320.4 hm², and the predicted area of potential high suitability area was twice of current area, indicating that there was still a large proportion of high suitability area that was not occupied by S. alterniflora. The most important environmental factors driving the distribution of potential habitats in mangroves were offshore Euclidean distance (62.2%), terrain deviation index (8.7%), average sea surface temperature in the hottest season (6.1%), and seabed terrain elevation (5.6%). The contribution of geographical conditions on mangrove distribution was predominant. Under the climate change scenario (SSP5-8.5), potential suitable area for mangroves would increase by 5.3%, while that for S. alterniflora would decrease by 3.1%. The overlapping proportion of the potential suitable area for mangroves and S. alterniflora was similar under current and SSP5-8.5 scenarios, being 15.2% and 14.5%, respectively. In the future, it is necessary to strengthen the protection and ecological restoration of mangroves along the coast of Guangxi and there is great challenge for preventing further invasion of S. alterniflora.

Effects of ant nests on soil CH₄ emissions from Syzygium oblatum communities of a secondary tropical forest

XIE Lingling, WANG Shaojun, XIAO Bo, WANG Zhengjun, GUO Zhipeng, GUO Xiaofei, LUO shuang, LI Rui, XIA Jiahui, LAN Mengjie, YANG Shengqiu

2024, 35(3):  678-686.  doi:10.13287/j.1001-9332.202403.030

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Exploring the effects of ant nests on soil CH₄ emissions in the secondary tropical forests is of great scientific significance to understand the contribution of soil faunal activities to greenhouse gas emissions. With static chamber-gas chromatography method, we measured the dry-wet seasonal dynamics of CH₄ emissions from ant nests and control soils in the secondary forest of Syzygium oblatum communities in Xishuangbanna. We also examined the linkages of ant-mediated changes in functional microbial diversity and soil physicochemical properties with CH₄ emissions. The results showed that: 1) Ant nests significantly accelerated soil CH₄ emissions, with average CH₄ emissions in the ant nests being 2.6-fold of that in the control soils. 2) The CH₄ emissions had significant dry-wet seasonal variations, which was a carbon sink in the dry seasons (from -0.29±0.03 to -0.53±0.02 μg·m^-2·h^-1) and a carbon source in the wet seasons (from 0.098±0.02 to 0.041±0.009 μg·m^-2·h^-1). The CH₄ emissions were significantly higher in ant nests than in control soils. The CH₄ emissions from the ant nests had smaller dry-wet seasonal variation (from -0.38±0.01 to 0.12±0.02 μg·m^-2·h^-1) than those in the control soils (from -0.65±0.04 to 0.058±0.006 μg·m^-2·h^-1). 3) Ant nests significantly increased the values (6.2%-37.8%) of soil methanogen diversity (i.e., Ace and Shannon indices), temperature and humidity, carbon pools (i.e., total, easily oxidizable, and microbial carbon), and nitrogen pools (i.e., total, hydrolyzed, ammonium, and microbial biomass nitrogen), but decreased the diversity (i.e., Ace and Chao1 indices) of methane-oxidizing bacteria by 21.9%-23.8%. 4) Results of the structural equation modeling showed that CH₄ emissions were promoted by soil methanogen diversity, temperature and humidity, and C and N pools, but inhibited by soil methane-oxidizing bacterial diversity. The explained extents of soil temperature, humidity, carbon pool, nitrogen pool, methanogen diversity, and methane-oxidizing bacterial diversity for the CH₄ emission changes were 6.9%, 21.6%, 18.4%, 15.2%, 14.0%, and 10.8%, respectively. Therefore, ant nests regulated soil CH₄ emission dynamics through altering soil functional bacterial diversities, micro-habitat, and carbon and nitrogen pools in the secondary tropical forests.

Change pattern and stability of oasisization land in Mu Us Sandy Land

YANG Haoqin, WANG Haibing, ZUO Hejun, QIAO Shuo, LI Siqi

2024, 35(3):  687-694.  doi:10.13287/j.1001-9332.202403.021

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Understanding land structure change and stability in the process of oasisization is particularly important for the desertification control in sandy land. Based on land use data of eight periods from 1980 to 2020, we extracted the spatial distribution information of oasis land in Mu Us Sandy Land, and analyzed the spatio-temporal variations of land transformation patterns and stability of oasis land with overlay analysis and grid analysis. The results showed that desertification in the Mu Us Sandy Land had reversed, with a significant process of oasis. The area of forest and grassland increased from 10.2% in 1980 to 73.7% in 2020, while the area of oasisization land increased from 32500 km² in 1980 to 33900 km² in 2020. The area of extremely severe, severe, and moderate desertification significantly decreased, while the area of non-desertification and mild desertification obviously increased. The four patterns of oasisization land transformation, including stability, fluctuation, expansion, and retreat, which accounted for 78.7%, 12.2%, 6.2%, and 2.9% of the oasisization land area in 2020, respectively. The oasisization land with low change intensity (the cumulative change intensity less than 0.12) in the Mu Us Sandy Land accounted for 82.7% of the total oasisization area, and the oasisization land in the sandy land was generally stable. Zoning management strategies should be applied according to the stability of sand belt and transformation pattern of oasisization land to achieve the goal of efficient system management and improvement, including eliminating sand hazards at desertification expansion areas with strong wind and sand activities, consolidating sand resources at oasisization areas where ecologically fragile desertification was frequent, and sustainably managing and utilizing sand resources at stable expansion of oases in forest- and grass-rich oasisization areas.

Effects of long-term no-tillage and different stover mulching amounts on soil carbon and nitrogen contents and enzyme activities of carbon and nitrogen cycle in Mollisols

YU Yang, ZHANG Changren, YANG Yali, XU Xin, LYU Fuze, ZHENG Tiantian, XIE Hongtu, BAO Xuelian

2024, 35(3):  695-704.  doi:10.13287/j.1001-9332.202403.012

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To understand the effects of different stover mulching amounts in no-tillage on soil carbon and nitrogen contents and enzyme activities, finding a stover mulching amount which can meet the requirement of soil carbon and nitrogen accumulation while maximizing economic benefits, we conducted a long-term conservation tillage field experiment since 2007 in Mollisols area of Northeast China. We analyzed soil carbon and nitrogen contents, enzyme activities and economic benefits under conventional tillage (Control, CT), no-tillage without stover mulching (NT₀), no-tillage with 33% stover mulching (NT₃₃), no-tillage with 67% stover mulching (NT₆₇), and no-tillage with 100% stover mulching (NT₁₀₀) before planting in May 2020. The results showed that compared with CT, NT₀ did not affect soil organic carbon (SOC) and total nitrogen (TN) contents, but increased soil organic carbon recalcitrance and decreased the availability of dissolved organic nitrogen (DON) and ammonium nitrogen. Compared with NT₀, no-tillage with stover mulching significantly increased SOC contents in 0-10 cm layer and increased with the amounts of stover. In addition, NT₆₇ and NT₁₀₀ significantly increased SOC stocks, facilitating the accumulation of soil organic matter. The effects of different stover mulching amounts on soil nitrogen content in 0-10 cm layer were different. Specifically, NT₃₃ increased DON content and DON/TN, NT₆₇ increased DON content, while NT₁₀₀ increased TN content. Compared with CT, NT₀ decreased peroxidase (POD) activity in 0-10 cm layer. Compared with NT₀, NT₃₃ increased β-glucosidase (βG), cellobiase (CB), 1,4-β-N-acetylglucosaminidase (NAG), polyphenol oxidase (PPO) and POD activities, while NT₆₇ only increased CB, NAG and POD activities in 0-10 cm soil layer, both alleviated microbial nutrient limitation. NT₁₀₀ increased PPO activity in 10-20 cm layer. NT₃₃ increased carbon conversion efficiency of stover compared with NT₁₀₀, and had the highest economic benefit. In all, no-tillage with 33% stover mulching was the optimal strategy, which could promote nutrient circulation, boost stover utilization efficiency, improve the quality of Mollisols, and maximize guaranteed income.

Effects of returning paddy field to wetland on composition and stability of soil aggregates in the Yellow River Delta

LU Guowei, WANG Qixuan, YANG Jisong, SUN Dandan, WANG Zhikang, ZHOU Di, GUAN Bo, YU Junbao, NING Kai

2024, 35(3):  705-712.  doi:10.13287/j.1001-9332.202403.017

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The composition and stability of soil aggregates are important indicators for measuring soil quality, which would be affected by land use changes. Taking wetlands with different returning years (2 and 15 years) in the Yellow River Delta as the research object, paddy fields and natural wetlands as control, we analyzed the changes in soil physicochemical properties and soil aggregate composition. The results showed that soil water content, total organic carbon, dissolved organic carbon and total phosphorus of the returning soil (0-40 cm) showed an overall increasing trend with returning period, while soil pH and bulk density was in adverse. There was no significant change in clay content, electrical conductivity, and total nitrogen content. The contents of macro-aggregates and micro-aggregates showed overall increasing and decreasing trend with returning period, respectively. The stability of aggregates in the topsoil (0-10 cm) increased with returning years. Geometric mean diameter and mean weight diameter increased by 8.9% and 40.4% in the 15^th year of returning, respectively, while the mass proportion of >2.5 mm fraction decreased by 10.5%. There was no effect of returning on aggregates in subsoil (10-40 cm). Our results indicated that returning paddy field to wetland in the Yellow River Delta would play a positive role in improving soil structure and aggregate stability.

Effects of root-applied biochar on soil nitrogen transformation and root nitrogen metabolism of cucumber seedlings in facility continuous cropping soils

YANG Xue, CAO Xia, BAI Bing, YUAN Yanna, ZHANG Ning, XIE Yang, WU Chuncheng

2024, 35(3):  713-720.  doi:10.13287/j.1001-9332.202403.015

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The problem of soil barrier caused by excessive accumulation of nitrogen is common in continuous cropping soil of facility agriculture. To investigate the modulating effects of biochar amendment on soil nitrogen transformation in greenhouse continuous cropping systems, we conducted a pot experiment with two treatments, no biochar addition (CK) and 5% biochar addition (mass ratio). We analyzed the effects of biochar addition on soil microbial community structure, abundances of genes functioning in nitrogen cycling, root growth and nitrogen metabolism-related genes expressions of cucumber seedlings. The results showed that biochar addition significantly increased plant height, root dry mass, total root length, root surface area, and root volume of cucumber seedlings. Rhizosphere environment was improved, which enhanced root nitrogen absorption by inducing the up-regulation of genes expressions related to plant nitrogen metabolism. Biochar addition significantly increased soil microbial biomass nitrogen, nitrate nitrogen, and nitrite nitrogen contents. The abundances of bacteria that involved in nitrogen metabolism, including Proteobacteria, Cyanobacteria, and Rhizobiales (soil nitrogen-fixing bacteria), were also significantly improved in the soil. The abundances of genes functioning in soil nitrification and nitrogen assimilation reduction, and the activities of enzymes involved in nitrogen metabolisms such as hydroxylamine dehydrogenase, nitronate monooxygenase, carbonic anhydrase were increased. In summary, biochar addition improved soil physicochemical properties and microbial community, and affected soil nitrogen cycling through promoting nitrification and nitrogen assimilation. Finally, nitrogen adsorption capacity and growth of cucumber plant was increased.

Effects of Cu₂O nanoparticles on the kinetic characteristics of rapid chlorophyll fluorescence induction and related genes in wheat seedlings

GUO Wei, WANG Nan, ZHANG Kaiyue, SONG Peipei, MA Zhanqiang

2024, 35(3):  721-730.  doi:10.13287/j.1001-9332.202403.009

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Metal nanoparticles could be accumulated in soils, which threatens the ecological stability of crops. Investigating the effects of cuprous oxide nanoparticles (Cu₂O-NPs) on photosystem Ⅱ (PSⅡ) of wheat seedling leaves holds considerable importance in comprehending the implications of Cu₂O-NPs on crop photosynthesis. Following the hydroponic method, we investigated the effects of 0, 10, 50, 100, and 200 mg·L^-1 Cu₂O-NPs on chlorophyll fluorescence induction kinetics and photosynthetic-related genes in wheat seedlings of “Zhoumai 18”. The results showed that, with the increases of Cu₂O-NPs concentrations, chlorophyll contents in wheat leaves decreased, and the standardization of the OJIP curve showed a clearly K-phase (ΔK＞0). Cu₂O-NPs stress increased the parameters of active PSⅡ reaction centers, including the absorption flux per active RC (ABS/RC), the trapping flux per active RC (TRo/RC), the electron transport flux per active RC (ETo/RC), and the dissipation flux per active RC (DIo/RC). Cu₂O-NPs stress decreased the parameters of PSⅡ energy distribution ratio including the maximum quantum yield of PSⅡ (φ_Po), the quantum yield of electron transport from QA (φ_Eo), and the probability that a trapped exciton moved an electron further than QA (Ψ_o), while increased the quantum ratio for heat dissipation (φ_Do). Moreover, there was a decrease in photosynthetic quantum yield Y(Ⅱ), photochemical quenching coefficient (q_P), net photosynthetic rate (P_n), stomatal conductance (g_s), intercellular CO₂ concentration (C_i), and transpiration rate (T_r) of leaves with the increases of Cu₂O-NPs concentration. Under Cu₂O-NPs stress, the expression levels of genes which included PSⅡ genes (PsbD, PsbP, Lhcb1), Rubisco large subunit genes (RbcL), cytochrome b6/f complex genes (PetD, Rieske), and ATP synthase genes (AtpA, AtpB, AtpE, AtpI) were downregulated. These results indicated that Cu₂O-NPs stress altered the activity and structure of PSⅡ in wheat seedlings, affected the activity of PSⅡ reaction centers, performance parameters of PSⅡ donor and acceptor sides. PSⅡ related genes were downregulated and exhibited significant concentration effects.

Construction of yield loss indicators for cold vortex, light-temperature-water combined stress during the flowering period of rice in Northeast China

LYU Jiajia, CHU Zheng, LI Baichao, GONG Lijuan, ZHOU Baocai, LIU Dan, WANG Dongni, JIANG Lixia

2024, 35(3):  731-738.  doi:10.13287/j.1001-9332.202403.035

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The construction of a yield loss evaluation index for the cold vortex type light-temperature-water composite adversity during rice flowering period in Northeast China is important for elucidating the impacts of cold vortex type composite disasters on rice yield loss in middle and high latitude areas. Moreover, it can provide meteorological support to ensure safe production of high-quality japonica rice in China and contribute to regional disaster reduction and efficiency improvement. By combining growth period data, meteorological data, and yield data, we delineated and constructed the composite stress occurrence index of cold vortex type light-temperature-water at the flowering stage of japonica. We analyzed the relationship between factors causing disasters and yield structure, as well as the relationship between different yield structures and yield by employing BP neural network method. We further dissected the processes involved in the causation of combined disasters. Based on the K-means clustering method and historical typical disaster years, we quantified the critical thresholds and disaster grades, and established an evaluation index and model for assessing yield loss caused by combined stress from cold vortex type light-temperature-water. Finally, we examined the spatial and temporal variations of low temperature, abundant rainfall, and reduced sunlight during the flowering period in the three provinces of Northeast China. Results showed that the critical thresholds for light, temperature, and water stress index during the flowering stage of mild, moderate, and severe cold vortex types were [0, 0.21), [0.21, 0.32), and [0.32, 0.64], respectively. The rates of yield loss were [0, 0.03), [0.03, 0.08), and [0.08, 0.096], respectively. Based on the verification results of a total of 751 samples in 11 random years from 1961 to 2020, the percentage of stations for which the production reduction grade, as calculated by the composite index developed in this study, aligning with the actual production reduction grade was 63.7%, consistently exceeding 58.0% annually. Moreover, the proportion of sites with a similarity or difference level of 1 stood at 88.3%, surpassing 85.0% in each year. The index could effectively assess the extent of rice yield loss caused by cold vortex disasters in Northeast China.

Characteristics of spatial and temporal variability in the distribution of biological soil crusts on the Loess Plateau, China

ZHAO Yunge, JI Jingyi, ZHANG Wantao, MING Jiao, HUANG Wanyun, GAO Liqian

2024, 35(3):  739-748.  doi:10.13287/j.1001-9332.202403.011

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Biological soil crust (biocrust) is widely distributed on the Loess Plateau and plays multiple roles in regulating ecosystem stability and multifunctionality. Few reports are available on the distribution characteristics of biocrust in this region, which limits the assessment of its ecological functions. Based on 388 sampling points in different precipitation zones on the Loess Plateau from 2009 to 2020, we analyzed the coverage, composition, and influencing factors of biocrust across different durations since land abandonment, precipitation levels, topography (slope aspect and position), and utilization of abandoned slopelands (shrubland, forest, and grassland). On this base, with the assistance of machine learning and spatial modeling methods, we generated a distribution map of biocrust and its composition at a resolution of 250 m × 250 m, and analyzed the spatial distribution of biocrust on the Loess Plateau. The results showed that the average biocrust coverage in the woodlands and grasslands was 47.3%, of which cyanobacterial crust accounted for 25.5%, moss crust 19.7%, and lichen crust 2.1%. There were significant temporal and spatial variations. Temporally, the coverage of biocrust in specific regions fluctuated with the extension of the abandoned durations and coverage of cyanobacterial crust, while moss crust showed a reverse pattern. In addition, the coverage of biocrust in the wet season was slightly higher than that in the dry season within a year. Spatially, the coverage of biocrusts on the sandy lands area on the Loess Plateau was higher and dominated by cyanobacterial crusts, while the coverage was lower in the hilly and gully area. Precipitation and utilization of abandoned land were the major factors driving biocrust coverage and composition, while slope direction and position did not show obvious effect. In addition, soil organic carbon content, pH, and texture were related to the distribution of biocrust. This study uncovered the spatial and temporal variability of biocrust distribution, which might provide important data support for the research and management of biocrust in the Loess Plateau region.

Responses of runoff and sediment yield to slope length and gravel content of Lou soil engineering accumulation slope in Guanzhong region, Northwest China

GUO Peilong, WANG Wenlong, LI Jianming, KANG Hongliang, LOU Yibao, WEI Sihan

2024, 35(3):  749-758.  doi:10.13287/j.1001-9332.202403.019

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With the economic development, a large number of engineering accumulation bodies with Lou soil as the main soil type were produced in Guanzhong area, Northwest China. We examined the characteristics of runoff and sediment yield of Lou soil accumulation bodies with earth (gravel content 0%) and earth-rock (gravel content 30%) under different rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min^-1) and different slope lengths (3, 5, 6.5, 12 m) by the simulating rainfall method. The results showed that runoff rate was relatively stable when rainfall intensity was 1.0-1.5 mm·min^-1, while runoff rate fluctuated obviously when rainfall intensity was 2.0-2.5 mm·min^-1. The average runoff rate varied significantly across different rainfall intensities on the same slopes, and the difference of average runoff rate of the two slopes was significantly increased with rainfall intensity. Under the same rainfall intensity, the difference in runoff rate between the slope lengths of the earth-rock slope was more obvious than that of the earth slope. When the slope length was 3-6.5 m, flow velocity increased rapidly at first and then increased slowly or tended to be stable. When the slope length was 12 m, flow velocity increased significantly. In general, with the increases of rainfall intensity, inhibition effect of gravel on the average flow velocity was enhanced. When rainfall intensity was 2.5 mm·min^-1, the maximum reduction in the average flow velocity of earth-rock slope was 61.5% lower than that of earth slope. When rainfall intensity was less than 2.0 mm·min^-1, sediment yield rate showed a trend of gradual decline or stable change, while that under the other rainfall intensities showed a trend of rapid decline and then fluctuated sharply. The greater the rainfall intensity, the more obvious the fluctuation. There was a significant positive correlation between the average sediment yield rate and runoff parameters, with the runoff rate showing the best fitting effect. Among the factors, slope length had the highest contribution to runoff velocity and rainfall erosion, which was 51.8% and 35.5%, respectively. This study can provide scientific basis for soil and water erosion control of engineering accumulation in Lou soil areas.

Construction of carbon sequestration ecological network in Linyi City based on supply and demand of ecosystem service

LIANG Huaqiu, SHEN Menghan, SHAO Ming, YAO Peng

2024, 35(3):  759-768.  doi:10.13287/j.1001-9332.202403.027

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The increasing carbon emissions is one of the important reasons for global warming. As a key area of carbon emissions, carbon sequestration capacity of cities is urgently needed to be improved. Carbon sequestration ser-vices can be transferred between supply and demand areas due to the circulation of atmosphere. With Linyi City as an example, we used the minimum cumulative resistance model to extract the matching path of supply and demand, and constructed a carbon sequestration ecological network. The results showed that the regions with high supply of carbon sequestration services were located in the north and south of the study area, and that current total supply could solve about 60% of the total demand. Although the spatial distribution of supply and demand was uneven, 54% of the areas that could meet the surrounding carbon sequestration demand were still idle. The optimized supply-demand matching paths could maintain good transmission efficiency of material and energy, with lower costs. Paths with strong potential carbon sequestration capacity were located in the central and northwest part of the research area. In the construction of carbon sequestration ecological network, it is necessary to strengthen the protection and restoration of the supply side of carbon sequestration services, realize carbon reduction and strengthen carbon sequestration on the demand side, and optimize the matching path of supply and demand. This method provided services to the demand areas through the oversupply of ecosystem services, optimized the overall resource allocation, which could advance regional carbon sequestration capacity.

Correlations between ecosystem service value and landscape ecological risk and its spatial heterogeneity in Jilin Province, China

LIANG Shihao, LI Wen, GAO Yu, LIU Baozhu

2024, 35(3):  769-779.  doi:10.13287/j.1001-9332.202403.022

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Exploring the correlations between ecosystem service value (ESV) and landscape ecological risk and the driving factors of their spatial variations is crucial for maintaining regional ecological security and promoting sustainable human well-being. We carried out a grid resampling size of 5 km×5 km assessment units of Jilin Pro-vince based on the remote sensing monitoring data of land use in 2000, 2005, 2010, 2015, and 2020. We quantitatively evaluated the landscape ecological risk and ESV, and analyzed their spatial-temporal variations. Employing bivariate spatial autocorrelation analysis and the geographical detector models, we examined the correlation between the landscape ecological risk and ESV and explored the driving factors for their spatial variations. The results showed that ESV in Jilin Province decreased from 385.895 billion yuan to 378.211 billion yuan during 2000-2020. The eastern region was dominated by extremely low risk, medium risk, and low risk areas. In contrast, the western region was mainly composed of extremely high risk and high risk areas. There was a significant negative correlation and spatial negative correlation between landscape ecological risk and ESV in Jilin Province. Human activity and land use type were the important driving factors for spatial differentiation in both landscape ecological risk and ESV. Our findings suggested that scientific land use regulation and appropriate control of human activities are critically needed to optimize Jilin Province’s ecological environment.

Evaluation of ecotourism suitability based on AHP-GIS: Taking Xiaoxiangling area of the Giant Panda National Park and the surrounding communities as an example

HU Jiayuan, LIU Lingyu, DAI Qinlong, YANG Bing, ZHOU Wenjia

2024, 35(3):  780-788.  doi:10.13287/j.1001-9332.202403.020

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The primary goal of national parks is to protect ecological environment, but also with the functions of scientific research, education, and recreation. Aiming for the realization of universal sharing, we used the analytic hierarchy process (AHP) to construct an ecotourism suitability evaluation system by selecting four factors, including landscape resources, ecological environment carrying capacity, recreation utilization capacity and social condition, taking Xiaoxiangling area of Giant Panda National Park and the surrounding communities as an example. We evaluated the ecotourism suitability based on GIS, and conducted a questionnaire survey of tourists, to propose suggestions on the functional zoning in terms of ecotourism suitability and subjective choice preferences of tourists. The results showed that the ecotourism suitability of the evaluation area could be classified into five levels. The most suitable areas were located nearby the natural landscape resources and far away from the core conservation area, and the least suitable areas distributed at the edge of the core conservation area. According to the results of suitability analysis, the evaluation area was divided into suitable development area, moderate development area, and restricted development area. Combined with the tourist preferences, we divided the recreational activities in the evaluation area into seven activities, namely, ecotourism, eco-camping, science education, leisure vacation, agricultural and animal husbandry culture experience, eco-education, and mountain adventure. These findings could help provide suitable services for different tourists and offer reference for the ecotourism developmental planning of the Xiaoxiangling area of the Giant Panda National Park.

Prediction of atrazine degradation in soil based on XGBoost model

LI Xiangling, CHEN Fengxian, CHEN Xijuan

2024, 35(3):  789-796.  doi:10.13287/j.1001-9332.202403.016

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We established the optimal model by using the automatic machine learning method to predict the degradation efficiency of herbicide atrazine in soil, which could be used to assess the residual risk of atrazine in soil. We collected 494 pairs of data from 49 published articles, and selected seven factors as input features, including soil pH, organic matter content, saturated hydraulic conductivity, soil moisture, initial concentration of atrazine, incubation time, and inoculation dose. Using the first-order reaction rate constant of atrazine in soil as the output feature, we established six models to predict the degradation efficiency of atrazine in soil, and conducted comprehensive analysis of model performance through linear regression and related evaluation indicators. The results showed that the XGBoost model had the best performance in predicting the first-order reaction rate constant (k). Based on the prediction model, the feature importance ranking of each factor was in an order of soil moisture > incubation time > pH > organic matter > initial concentration of atrazine > saturated hydraulic conductivity > inoculation dose. We used SHAP to explain the potential relationship between each feature and the degradation ability of atrazine in soil, as well as the relative contribution of each feature. Results of SHAP showed that time had a negative contribution and saturated hydraulic conductivity had a positive contribution. High values of soil moisture, initial concentration of atrazine, pH, inoculation dose and organic matter content were generally distributed on both sides of SHAP=0, indicating their complex contributions to the degradation of atrazine in soil. The XGBoost model method combined with the SHAP method had high accuracy in predicting the performance and interpretability of the k model. By using machine learning method to fully explore the value of historical experimental data and predict the degradation efficiency of atrazine using environmental parameters, it is of great significance to set the threshold for atrazine application, reduce the residual and diffusion risks of atrazine in soil, and ensure the safety of soil environment.

Ecological niche shift and suitable area expansion of a globally invasive species Phthorimaea operculella

WANG Lili, YANG Caiqing, WANG Ying, LI Xinhai, WAN Fanghao, ZHANG Aibing

2024, 35(3):  797-805.  doi:10.13287/j.1001-9332.202403.013

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Phthorimaea operculella is a major potato pest of global importance, early warning and detection of which are of significance. In this study, we analyzed the climate niche conservation of P. operculella during its invasion by comparing the overall climate niche from three dimensions, including the differences between native range (South America) and entire invaded region (excluding South America), the differences bwtween native range (South America) and five invaded continents (North America, Oceania, Asia, Africa, and Europe), as well as the differences between native region (South America) and an invaded region (China). We constructed ecological niche models for its native range (South America) and invaded region (China). The results showed that the climatic niche of the pest has expanded to varying degrees in different regions, indicating that the pest could well adapt to new environments during the invasion. Almost all areas of South America are suitable for P. operculella. In China, its suitable area is mainly concentrated in Shandong, Hebei, Tianjin, Beijing, Henan, Hubei, Yunnan, Guizhou, Sichuan, Hainan, northern Guangxi, southern Hunan, Anhui, Guangdong, Jiangsu, southern Shanxi, and southern Shaanxi. With increasing greenhouse gas emissions and global temperature, its suitable area will decrease at low latitude and increase gradually at high latitude. Specifically, the northern boundary will extend to Liaoning, Jilin, and the southeastern region of Inner Mongolia, while the western boundary extends to Sichuan and the southeast Qinghai-Tibet Plateau. The suitable area in the southeast Yunnan-Guizhou Plateau, Hainan Island, and the south of Yangtze River, will gradually decrease. The total suitable habitat area for P. operculella in China is projected to increase under future climate condition. From 2081 to 2100, under the three greenhouse gas emissions scenarios of ssp126, ssp370, and ssp585, the suitable area is expected to increase by 27.78, 165.54, and 140.41 hm², respectively. Therefore, it is crucial to strengtehen vigilance and implement strict measures to prevent the further expansion of P. operculella.

Evaluation of water ecological health of Yanhe River based on benthic fauna integrity index

HE Yao, SUN Chang-shun, HOU Yiming, HU En, HOU Xiangran, FENG Zhiyuan, ZHANG Xuda, PAN Baozhu

2024, 35(3):  806-816.  doi:10.13287/j.1001-9332.202402.017

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Yanhe River Basin is located in the hilly gully area of the Loess Plateau with serious soil erosion. Strong human activities in the middle and lower reaches lead to fragile ecological environment. Soil erosion status varies among different geomorphic units within the watershed (loess liang hilly and gully region, loess mao hilly and gully region, and broken platform region). In this study, we surveyed the benthic community from the Yanhe River Basin in April (spring) and October (autumn) of 2021. To evaluate the water ecological health status of the watershed and investigate the effects of different geomorphic units on the benthic integrity of the benthos, we constructed the benthic-index of biotical integrity (B-IBI) based on the biological data. We identified a total of 113 species of 73 genera in 4 phyla of benthic fauna, with aquatic insects as the dominant taxa in both seasons. Through screening 26 candidate indicators, we found that the spring B-IBI consisted of three indicators: relative abundance of individuals of dominant taxonomic units, family biotic index (FBI), and relative abundance of predator individuals, and that autumn B-IBI was composed of the number of taxonomic units of Ephemeroptera, FBI value, and the relative abundance of predator individuals. Results of the B-IBI evaluation showed that 83.3% of the sampling sites in the upper mainstem and tributaries were at a healthy condition, while only 28.6% sampling sites in the middle and lower mainstem and tributaries were at a healthy condition. In addition, the health status of the watershed was better in spring than in autumn. The Kruskal-Wallis nonparametric tests showed that benthic density, species number, and B-IBI percentile scores in the fragmented loess area were significantly higher in spring than in autumn, and significantly lower in autumn than in the loess liang hilly and gully region and loess mao hilly and gully region, being mainly caused by the increasing erosion due to the concentrated rainfall in wet season. Results of the redundancy analysis showed that key environmental factors affecting benthic community structure in spring were boulder substrate, chlorophyll-a, oxidation reduction potential, turbidity, conductivity, and dissolved oxygen, and were nitrate-nitrogen, oxidation reduction potential, and pH in autumn.

Preliminary investigation on the causes of red tides in Qinhuangdao coastal areas in 2022

XU Jintao, YAO Yuan, YANG Wen, WANG Zhong, LI Xinyang, TAN Faqi, LI Weiwei, MA Jicheng, MA Xin

2024, 35(3):  817-826.  doi:10.13287/j.1001-9332.202403.029

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To explore the causes of red tides in Qinhuangdao coastal water, we conducted surveys on both water quality and red tides during April to September of 2022 and analyzed the relationships between main environmental factors and red tide organisms through the factor analysis and canonical correspondence analysis. The results showed that there were eight red tides along the coast of Qinhuangdao in 2022, with a cumulative blooming area of 716.1 km². The red tides could be divided into three kinds based on the major blooming organisms and occurrence time, Noctiluca scintillans bloom, diatom-euglena (Skeletonema costatum, Eutreptiella gymnastica, Pseudo-nitzschia spp.) bloom, and dinoflagellate (Scrippsiella trochoidea and Ceratium furca) bloom. Seasonal factor played roles mainly during July to September, while inorganic nutrients including nitrogen and phosphorus influenced the blooms mainly in April and July. The canonical correspondence analysis suggested that N. scintillans preferred low temperature, and often bloomed with high concentrations of ammonium nitrogen and dissolved inorganic phosphorus. S. costatum, E. gymnastica, and Pseudo-nitzschia spp. could tolerate broad ranges of various environmental factors, but favored high temperature and nitrogen-rich seawater. C. furca and S. trochoidea had higher survival rate and competitiveness in phosphate-poor waters. Combined the results from both analyses, we concluded that the causes for the three kinds of red tide processes in Qinhuangdao coastal areas in 2022 were different. Adequate diet algae and appropriate water temperature were important factors triggering and maintaining the N. scintillans bloom. Suitable temperature, salinity and eutrophication were the main reasons for the diatom-euglena bloom. The abundant nutrients and seawater disturbance promoted the germination of S. trochoidea cysts, while phosphorus limitation caused the blooming organism switched to C. furca and maintained the bloom hereafter.

Reviews

Research status and prospect of ratoon rice in China under mechanically harvested condition

LIN Wen-xiong, WENG Peiying, LIN Wenfang, SHAO Caihong, GUO Chunlin, LI Zhong, CHEN Hongfei, CHEN Ting

2024, 35(3):  827-836.  doi:10.13287/j.1001-9332.202403.008

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The proportion and area of ratoon rice planting in China have been substantially increased, due to continuous improvement of rice breeding methods and consecutive innovation of cultivation technology, which has developed into one of rice planting modes with significant production efficiency. Combining the experience in research and practice, from the perspective of crop physiology and ecology, we reviewed the current situation and prospects of high-yielding formation and physiological mechanisms of ratoon rice. We focused on four key aspects: screening and breeding of ratoon rice cultivars and the classification; suitable stubble height for mechanically harvested ratoon rice, as well as water and fertilizer management; dry matter production and allocation in ratoon rice and the relationship with yield formation; regenerative activity and vigor of ratoon rice roots and their relationship with rhizosphere micro-ecological characteristics. As for the extending of mechanized low-cut stubbles ratoon rice technique, we should properly regulate the rhizosphere system, coordinate rhizosphere nutrient supply, germination of axillary buds, and tillering regeneration, to achieve the target of “four-high-one-low”, that is high regeneration coefficient, high number of regeneration panicle, high harvest index, high yield, high quality, low-carbon and safe, aiming to improve the sustainability of ratoon rice industry.

Research progress on ecological adaptation and prevention of Parengyodontium album on the surface of cultural relics

MA Xiaorui, WU Fasi, MA Wenxia, ZHANG Qi, FENG Huyuan

2024, 35(3):  837-846.  doi:10.13287/j.1001-9332.202403.031

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Cultural relics as the crystallization of human history are non-renewable and irreplaceable resources. Microorganisms are widely colonized on ancient wall paintings, stone cultural relics, and other types of cultural heritages to cause harm. The dominant disease fungus, Parengyodontium album, is extensively distributed and can seriously threaten the long-term preservation of precious cultural heritage due to surviving in various cultural relics and extreme environments. The classification and nomenclature of P. album have undergone several changes, so its impact on cultural relic received little attention. Here, we summarized the brief histories of its classification and development, distribution range, and cultural heritage preference of P. album. We further analyzed the physiological, biochemical, and ecological characteristics and potential biological degradation mechanism. We proposed that P. album could be used as an indicative species of microbial hazardous effects on cultural heritage. We discussed the prevention and control countermeasures of such typical mural microorganisms and pointed out key research directions in this field.

Improving crop health by synthetic microbial communities: Progress and prospects

WENG Lingyin, LUAN Dongdong, ZHOU Dapu, GUO Qinggang, WANG Guangzhou, ZHANG Junling

2024, 35(3):  847-857.  doi:10.13287/j.1001-9332.202403.028

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Crop health directly affects yields and food security. At present, agrochemicals such as fertilizers and pesticides are mainly used in agricultural production to promote crop health. However, long-term excessive utilization of agrochemicals will damage the ecological environment of farmlands and increase the safety risk of agricultural products. It is urgent to explore efficient and environment-friendly agricultural products. Rhizosphere microbiome are considered as the second genome of plants, which are closely related to crop health. Understanding the key functional microbes, microbe-microbe interactions, and plant-microbe interactions are fundamental for exploring the potential of beneficial microbes in promoting crop health. However, due to the heterogeneity and complexity of the natural environment, stimulating the function of indigenous microorganisms remains uncertain. Synthetic microbial community (SynCom) is an artificial combination of two or more different strain isolates of microorganisms, with different taxonomic, genetic, or functional characteristic. Because of the advantages of maintaining species diversity and community stability, SynCom has been widely applied in the fields of human health, environmental governance and industrial production, and may also have great potential in promoting crop health. We summarized the concept and research status of SynCom, expounded the principles and methods of constructing SynCom, and analyzed the research on the promotion of crop health by exploring the mechanism of plant-microbe interactions, promoting plant growth and development, and improving stress resistance. Finally, we envisaged the future prospects to guide the using SynCom to improve crop health.

Research progress on insect visual electrophysiological techniques

LIU Hang, WEI Chengmei, FENG Taiyang, DONG Wenxia, XIAO Chun

2024, 35(3):  858-866.  doi:10.13287/j.1001-9332.202403.032

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Insect visual electrophysiological techniques are important to study the electrical characteristics of photoreceptor cells and visual neurons in insects, including electroretinography (ERG) and microelectrode intracellular recording (MIR). ERG records the changes of voltage or electric current in the retina of insects in response to different light stimuli, which occurs outside the cell. MIR records the changes in individual photoreceptor cells or visual neurons of an insect exposed to different lights, which occurs inside the cell. Insect visual electrophysiological techniques can explore the mechanism of electrophysiological response of insects’ vision to light and reveal their sensitive light spectra and photoreceptor types. This review introduced the basic structure and the principle of ERG and MIR, and summarized their applications in insect researches in the past 20 years, which would provide references for elucidating the mechanism of light perception in insects and the use of insect phototropism to control pests.