中国生态农业学报(中英文)

Cold/hot spots identification and tradeoff/synergy analysis of ecosystem services in Taihang Mountain area

GAO Hui, FU Tonggang, LIANG Hongzhu, LIU Jintong

2022, 30(7): 1045-1053. doi: 10.12357/cjea.20220041

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Abstract:
Mountains provide people with water conservation, soil conservation, climate regulation, biodiversity maintenance, product supply, and other ecosystem services. These ecosystem services are irreplaceable. Research on the characteristics of cold/hot spots of ecosystem services is of great significance for the protection and promotion of ecosystem services. Therefore, taking Taihang Mountain area as a research area, the cold/hot spots of ecosystem services were identified, and the tradeoff/synergies among ecosystem services were analyzed to provide theoretical support for the protection and promotion of ecosystem services in the Taihang Mountain. Cold/hot spots of were identified based on Getis-Ord Gi* statistical index. On this basis, the correlation coefficient method was used to analyze the tradeoff/synergy between the four ecosystem services in the cold/hot spots regions. The results are as follow: 1) On the grid scale, the total value of ecosystem services ranged from 0 Yuan to 185.06 million Yuan. The ecosystem service values were divided into five grades. The area and spatial distribution of the total value of ecosystem services on the grid scale remained unchanged from 1990 to 2015. The main distribution grades were 3.68−11.56 million Yuan and 11.56−33.85 million Yuan, and the two sections account for approximately 80% of the total area of Taihang Mountain area. The high-value area of 62.18−185.06 million Yuan has the least distribution area, accounting for only 1% of Taihang Mountain area. 2) In 2015, the total ecosystem service hot spots were distributed throughout the mountain area. The distribution area was the largest in the sub-alpine region (9558 km²), followed by the mid-mountainous region (5238 km²), and the smallest was in the hilly region (3969 km²). The cold spots area was mainly distributed in the eastern and western edges of the mountain area, whose distribution area in the low hills accounted for approximately 70% of the total area. 3) There were no cold spots in forests, water areas, or wetlands. There were no hot spots in the desert ecosystem. The hot spots in the water area, forest, and wetland were large in proportion; water areas had the largest proportion of hot spots (up to 65%), followed by forests and wetlands. The cold spots area in deserts, construction lands, and farmlands were large in proportion, and desert had the largest proportion of cold spots (up to 69%), followed by construction lands and farmlands. 4) In the cold/hot spots areas of the total ecosystem services in 2015, there was only a synergistic relationship among the ecosystem services. The conclusions drawn from the above results are as follows: 1) Based on the spatial distribution characteristics, the priority area for ecosystem services protection should be the subalpine area. 2) Based on land use, the priority protected areas for ecosystem services should include forests, water areas, and wetlands. 3) Based on the tradeoff and synergy between the four categories of ecosystem services in the cold/hot spots area of the Taihang Mountain, the cold/hot spots area can be used as the priority area for improving the protection of ecosystem services from the perspective of conservation efficiency.

Factors influencing soil water content during dry period in the middle part of the Taihang Mountain

FU Tonggang, GAO Yue, LIU Lili, GAO Hui, QI Fei, WANG Feng, LIU Jintong

2022, 30(7): 1054-1063. doi: 10.12357/cjea.20210793

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Abstract:
Taihang Mountain is an important natural boundary between the second and third steps in China. The elevation of this mountains decreases drastically from west to east. Owing to the complex environment in this transition zone, the spatial pattern of and the factors influencing soil water content (SWC) are complex and unclear. This limits further understanding of the soil hydrological processes. In this study, two line transects (140 km and 164 km long, respectively) were set in the middle part of the Taihang Mountain, which are 85 km apart. Both disturbed and undisturbed soils were sampled along two line transects during the dry period in the middle part of Taihang Mountain region. Soil water content, bulk density (BD), capillary porosity (CP), non-capillary porosity (NCP), soil organic carbon (SOC), and soil particle composition (sand, silt, and clay contents) were measured. Topographical conditions (including slope gradient, slope aspect, and elevation) and vegetation conditions (including vegetation type, vegetation cover, and litter information) were also investigated for each sampling point. Classical statistical, geostatistical, and structural equation modeling methods were used to study the variation and influencing factors of the SWC in the surface (0–10 cm) and subsurface (10–20 cm) layers along the two line transects in the middle part of the Taihang Mountain. The results showed that the SWC of the surface soil layer was significantly lower than that of the subsurface layer. No significant differences were observed between the two studied line transects. In geostatistical analysis, the most suitable SWC model was a linear model for the surface soil layer, but an exponential model for the subsurface layer. This indicated that random factors played a dominant role, and the influencing factors may be more complex for the surface soil layer. For the subsurface layer, an obvious nugget effect was observed, suggesting the coexistence of random and structural factors. The nugget to sill value of the subsurface layer was 48.01% and 31.62%, respectively, for the two-line transects. This indicated that both line transects showed moderate spatial dependence. Among the considered environmental factors, precipitation and elevation significantly influenced the SWC. Other environmental factors showed no significant effects. Among the studied soil properties, BD significantly influenced the SWC of the surface layer, whereas the CP and clay content significantly influenced the SWC of the subsurface soil layer. Structural equation modeling showed that soil properties were the direct factor, and environmental factors were indirect factors of SWC. Over 80% of the environmental factors acted through the soil properties. These results can be helpful in further understanding the soil water characteristics in the middle part of the Taihang Mountain and provide a scientific basis for studying soil hydrological processes in similar mountainous areas.

Spatio-temporal variations in soil erosion and its influence factors in Taihang Mountain area based on RUSLE modeling

WANG Feng, LIU Jintong, FU Tonggang, GAO Hui, QI Fei

2022, 30(7): 1064-1076. doi: 10.12357/cjea.20220043

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Abstract:
The study of soil erosion characteristics and their spatial heterogeneity is of great significance for ecological environmental protection. Soil and water conservation is important in Taihang Mountain area. This study was conducted to explore these characteristics. Supported by the normalized difference vegetation index (NDVI), digital elevation model (DEM), and land use data combined with geographic information system (GIS) and remote sensing (RS) technologies, the soil erosion modulus in Taihang Mountain area was calculated from 2000 to 2015 based on the revised universal soil loss equation (RUSLE) model. The spatiotemporal variation in soil erosion in the study area was analyzed, and the relationship between soil erosion, slope gradient, land use type, and NDVI was explored. The results showed that: 1) The average soil erosion modulus were 4434.14 t∙km⁻²∙a⁻¹, 2984.65 t∙km⁻²∙a⁻¹, 1761.93 t∙km⁻²∙a⁻¹ and 1833.81 t∙km⁻²∙a⁻¹ in 2000, 2005, 2010 and 2015, respectively. The erosion modulus showed a notably decreasing trend from 2000 to 2015 with a decreasing rate of 58.64%. 2) The areas where erosion intensity decreased by one level were always larger than those where it increased by one level. However, erosion intensity did not change in more than 74.77% of the total area. The maximum reduction in the erosion intensity occurred in the period of 2005–2010. 3) From 2000 to 2005, the decline in erosion intensity level in Taihang Mountain area was mainly distributed in higher elevation regions near the border of the Shanxi and Hebei Provinces. The areas with decreasing soil erosion intensity from 2005 to 2010 were uniformly distributed in the study area and were mainly located in the south of Yangquan and Shijiazhuang from 2010 to 2015. 4) In 2015, 86.54% of the total soil erosion (2.5×10⁸ t) was concentrated in the mid-mountain and hilly zones, where accounted for approximately 91.12% of the study area. There was no obvious correlation between the erosion modulus and altitude in this area, whereas it showed a positive relationship in the subalpine zone. 5) The erosion modulus had a positive correlation with slope gradient; the threshold value was 40º, and the erosion modulus reached a maximum value of 4693 t∙km⁻²∙a⁻¹. With an increase in slope gradient, the possibility of soil erosion increased gradually with higher grades of erosion intensity. Cultivated land, forest land and grassland were the three main land use types in the study area, and their average soil erosion modulus were 501.72 t∙km⁻²∙a⁻¹, 2475.46 t∙km⁻²∙a⁻¹ and 3505.73 t∙km⁻²∙a⁻¹, respectively. The average slope gradient of the cultivated land was 4.90º, which resulted in the minimum soil erosion modulus. Grassland was the land use type with the largest erosion modulus. The soil erosion modulus decreased significantly with an increase in annual NDVI, and the rate gradually slowed down when NDVI reached 0.66. Soil erosion is a significant index for eco-environmental quality appraisal. This study provides a scientific basis for soil erosion control and ecological engineering measures in Taihang Mountain area.

Vertical distribution of vegetation in mountain regions: A review based on bibliometrics

LIANG Hongzhu, LIU Lili, FU Tonggang, GAO Hui, LI Min, LIU Jintong

2022, 30(7): 1077-1090. doi: 10.12357/cjea.20210858

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Abstract:
Vertical change and distribution of mountain vegetation have always been the focus of mountain ecology research. This paper reviewed the research progress on the vertical distribution pattern of mountain vegetation using methods of bibliometric statistics and literature analysis. Based on the database platform of CNKI and Web of Science, we searched for papers published in this field from January 1915 to December 2020 and analyzed the research history, present status, progress, and trend of vertical patterns of mountain vegetation. The results showed that the number of studies, authors, countries, and institutions in China and abroad has increased. The main research countries or regions cover 85 countries, including the United States, Germany, China, Spain, and France, with 34.7% of the literature concentrated in 25 major journals. Based on the CiteSpace software, this study analyzed the hot fields of the research on vertical distribution of mountain vegetation in China and abroad, and reviewed the theories, hypotheses, research methods, and main research fields. The vertical pattern of mountain vegetation was verified by using methods from single-factor description and multi-factor analysis to determination of mechanism and hypothesis. Representative theories included time theory, spatial heterogeneity theory, competitive coexistence theory, neutral theory, and niche theory. The research methods were summarized as traditional research methods, quantitative classification and environmental interpretation, remote sensing image information technology, models, and digital information technology. In this study, the research hotspots in China and abroad were also analyzed and reviewed from the aspects of the vertical distribution and driving factors of mountain vegetation, vertical change in mountain vegetation productivity, spectral structure of plant communities, and prediction of vegetation distribution based on niche theory. In short, in the context of global climate change, the response of mountain vegetation and ecosystems is sensitive and dramatic, and the response of mountain vegetation to climate change, digital information of vegetation vertical band spectrum, ecological cycle, and ecosystem services under water-soil coupling has received more attention. Multi-scale and multi-subject integration patterns are trends in the studied vertical distribution of mountain vegetation.

Altitudinal distribution pattern and its driving factors of plant diversity in the middle section of the eastern slope of the Taihang Mountain

LIANG Hongzhu, LIU Lili, GAO Hui, FU Tonggang, ZHU Jianjia, SU Yang, LIU Jintong

2022, 30(7): 1091-1100. doi: 10.12357/cjea.20210863

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Abstract:
Due to global climate change, altitudinal distribution patterns of biodiversity and factors influencing biodiversity have changed dramatically. To clarify the elevational distribution pattern of plant diversity and the main influencing factors in the middle section of the eastern slope of the Taihang Mountain, the alpha and beta diversities of vascular plant communities were studied along the elevational gradient using the quadrat survey method. In the middle section of the eastern slope of the Taihang Mountain, the succession characteristics of plant communities along the elevational gradient were investigated. Additionally, the main factors influencing the altitudinal distribution pattern of plant diversity were studied. The possible mechanisms of plant altitudinal distribution patterns were discussed by exploring the relationships between plant diversity and environmental factors. The results showed that the distribution of the alpha diversity of vegetationa had two peaks along the elevational gradient, which was in line with the theory of “diversity peaks at the intermediate altitude”. By studying the correlation between plant diversity, water yield, and net primary production of vegetation along the altitudinal gradient, it was demonstrated that the distribution pattern of plant diversity on the elevational gradient was consistent with the vertical distribution pattern of water yield and net primary productivity of vegetation in the study area. The similarity index (beta diversity) of plant communities on the altitudinal gradient reached the lowest value in the peak area of species richness, indicating that there were significant differences among the plant communities within this height range, and that the replacement rate of plant species between communities increased, which led to an increase in plant species richness. The altitudinal distribution of net primary production of vegetation showed a consistent pattern with plant species richness in the study area, and there was a significant positive correlation between them. CCA and RDA analyses revealed that the main environmental factors influencing the distribution of plant diversity on the elevational gradient were altitude, temperature, and precipitation; and no significant correlation was found with topographic factors such as slope and aspect. Comparing the ordination results of CCA and RDA analyses, the results were found to be consistent, which proved that both the linear and unimodal models were suitable for the ordination study of plant species distribution in this region. Using the Monte Carlo permutation test, the significance of the explanatory quantity of environmental factors on species distribution was analyzed. The results showed that the ordination results can comprehensively explain the effects of various environmental factors on species distribution. Based on the comprehensive research results, it was concluded that the altitudinal distribution pattern of the vascular plants in the middle section of the eastern slope of the Taihang Mountain was the result of the synergistic effect of the community altitudinal succession processes, environmental influence, and human disturbance.

The impact of “Production-Living-Ecological” land structure change on ecosystem services and farmers’ livelihood: a case study of the Dongyangpo watershed in Taihang Mountain area

QI Fei, LI Yanxin, GAO Hui, FU Tonggang, WANG Feng, JIANG Guanyan, LIU Jintong

2022, 30(7): 1101-1112. doi: 10.12357/cjea.20220055

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Abstract:
Due to the influence of human activities on Taihang Mountain area, the land use structure of numerous small watersheds has undergone significant changes over the past few decades, which in turn affects the “Production-Living-Ecological” land use structure, ecosystem services, and the livelihood of mountain farmers in small watersheds. The Dongyangpo watershed is a typical transitional geographical space in the transition from the subalpine area to the hilly area of Taihang Mountain area. This study aimed to systematically study the impact of “Production-Living-Ecological” land use change on ecosystem services and farmers’ livelihoods in small mountain watersheds. Taking the Dongyangpo watershed, a typical small watershed in Taihang Mountain area, as an example, this study evaluated the structure change and ecosystem service values of “Production-Living-Ecological” land from 2000 to 2020 by modifying the coefficient of equivalent factor method in combination with the actual situation of the small watershed, and further investigated and analyzed the impact of the land structure change of “Production-Living-Ecological” on farmers’ livelihood by considering Forsythia suspensa, which has the largest artificial planting area. The research results showed that, first, over the past 20 years, the “Production-Living-Ecological” land structure in the Dongyangpo watershed had remained basically unchanged, showing ecological land > production land > living land. However, the land use mode within the ecological land had changed, which was specifically reflected in the significant increase in the planting area of F. suspense, the local dominant tree species, and reduction in grassland areas. Second, the ecological land in the Dongyangpo watershed contributed the most to the total ecosystem services, and the total ecosystem services value in each period accounted for more than 99% of the total. Third, over the past 20 years, the ecosystem service value had increased significantly, with an increase of 146.89%. The main reason for this was a large portion of grasslands in ecological land transforming into forest land represented by F. suspense forest, and the ecosystem service value increase caused by this change accounted for 99.95% of the total value of ecosystem services. Fourth, over the past 20 years, the increase in F. suspensa forest land supply services accounted for 43.05% of the increase in small watershed supply services and 28.02% of the increase in total ecosystem services value in the small watersheds. After F. suspensa planting, the livelihood level of farmers in the Dongyangpo watershed had improved, and the improvement of F. suspensa forest land ecosystem service supply benefits had increased the income of farmers in the Dongyangpo watershed. The change of “Production-Living-Ecological” land brought by F. suspensa planting also played a role in optimizing and adjusting the structure of farmers’ income source. This study provides a theoretical basis for the coordinated development of the ecological economy in Taihang Mountain area.

Analysis of “Production-Living-Ecological” land transformation and landscape ecological risk in the eastern counties of the Taihang Mountain: a case study in Pingshan County

YU Shuhui, KANG Yuanyuan, DENG Wei, WANG Gongming, WANG Hongkuan, XING Yuhua

2022, 30(7): 1113-1122. doi: 10.12357/cjea.20220365

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Abstract:
The Taihang Mountain is the natural ecological barrier of the Beijing-Tianjin-Hebei region. It is strategically important to assess risk to the Taihang Mountain ecology to ensure water security and assess its ecological function in the Beijing-Tianjin-Hebei region. This study established a classification system for the “Production-Living-Ecological” space land, and explored the characteristics of the “Production-Living-Ecological” land transformation in Pingshan County, a typical county in the Taihang Mountain. The landscape ecological risks in Pingshan County were explored using the landscape ecological risk evaluation method, and the contribution of land use transformation to the change in landscape ecological risk was measured. The results showed that: 1) from 1990 to 2018, the ecological land in Pingshan County decreased significantly, whereas the production and living lands increased significantly. The production and living lands were mainly transformed from ecological land, and the transformation areas were mainly distributed along the road and around the water area. 2) Areas with escalated landscape ecological risk in ecological land were mainly located in high-altitude areas in the central and western parts of the study area, and it is necessary to scientifically delineate the ecological protection redline and strengthen the ecological protection of these deep mountain areas in the future. Areas with escalated landscape ecological risks in production land were mainly located in the low mountains and hilly areas in the northern and eastern parts of the study area, where more attention should be paid to the protection and efficient use of cultivated land in the future. In contrast, the areas with escalated risk in living land were mainly located in the southern part of the study area, where the utilization of land resources should be adjusted, and the use of tourism resources should be scientifically planned in the future. 3) The contribution of land use transformation types to the change of landscape ecological risk in the Pingshan County varied greatly (0−29.97%), among which the risk of “transformation from ecological land to production land” made the greatest contribution. The results of this study can provide valuable reference information for promoting the coordinated development of the “Production-Living-Ecological” land use in Pingshan County and exploring green development and optimization of land space structure in the Taihang Mountain.

Spatiotemporal patterns of land-use change in the Taihang Mountain (1990−2020)

WEI Jing, LIU Lili, WANG Hongyun, ZHANG Yanxi, WANG Cailing, LIU Jintong, FU Tonggang, GAO Hui, LIANG Hongzhu, LIU Yuanchen

2022, 30(7): 1123-1133. doi: 10.12357/cjea.20210870

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Abstract:
The Taihang Mountain is an important ecological security barrier of the North China Plain and the Circum-Bohai Sea Economic Zone, which has a unique natural environment and humanistic historical background. The study of landscape patterns in mountainous areas is not only beneficial to the development of mountain ecology science but is also important for guiding sustainable economic and social development and eco-environment protection. In this study, the temporal and spatial variation in land use types in the Taihang Mountain were studied based on remote sensing data from Landsat 30 m TM (in 1990, 2000, 2010, and 2020). In addition, combined with the gravity center model, a comparative analysis of the variation trend of land use patterns in the Taihang Mountain was identified. The results showed that: 1) cultivated land, forest land, and grass land were the principal land use types in the Taihang Mountain from 1990 to 2020, while other land use types were embedded as plaques. 2) Over the past 30 years, the cultivated land area had been decreasing and mainly been converted to building land. The areas of forestland and grass land decreased gradually and were mainly converted into cultivated land. Additionally, the overall area of water decreased. The river ecological restoration project implemented in the Dasha River from 2010 to 2020 led to a large amount of unused land being transferred into water area, slowing down the degree of decline in the area of water. Moreover, the area of building land, mainly converted from arable land, had increased annually. The unused land area increased at first and then decreased, which was mainly reflected in the transformation of the water area. 3) Over 30 years, mainly influenced by the precipitation level, the unused land barycenter migrated 93.74 km northeastward. The barycenter of cultivated land fluctuated, migrating mainly northward, showing a west–east–west swing. This indicates that farmland reclamation intensity in the west of the Taihang Mountain hilly area was higher than that in the east, which was mainly found in Yuncheng and Jinzhong of Shanxi Province. The barycenter transfer direction of forest land and grass land was mainly southwest, over a relatively small distance. Mainly because of natural factors, the barycenter of the water area migrated southwest from 1990 to 2010, then suddenly shifted to the east between 2010 and 2020. The reason for this change was an increase in the water area in the east caused by the comprehensive Dashahe River control project. Thus, it was found that ecological restoration projects carried out by human beings had a significant influence on changes in landscape barycenters. In addition, the barycenter transfer direction of building land was mainly northeast and was affected by urban development, such as in Changping, Fangshan, and Yanqing of Beijing City. In short, based on the above research findings, the driving mechanism of landscape pattern variation in the Taihang Mountain area over 30 years (1990–2020) was further described.

Relationship between grain filling characteristics of maize and meteorological factors under different sowing dates

PENG Dandan, WU Chao, XU Kaiwei, CHEN Dagang, ZHU Hao, LIU Yuanyuan, CHEN Yuanxue

2022, 30(7): 1134-1142. doi: 10.12357/cjea.20210755

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Abstract:
This study, conducted to provide a theoretical basis for suitable sowing dates for the high yield and high-efficiency cultivation of maize in the Chengdu Plain, explored the relationships between 100-kernel weight (KW), grain filling parameters, and sowing date-associated meteorological factors after silking. To investigate the dry matter accumulation and grain filling characteristics under different sowing dates, the widely adaptive maize cultivar ‘Zhongyu 3’ was sown on six dates (March 27, April 6, April 16, April 26, May 6, and May 16). The results showed that with delayed sowing dates, the growth period of maize decreased, and grain yield and KW decreased significantly. The decreased yield was mainly attributed to KW, and variations in the grain-filling rate (G_mean) and the kernel weight at the maximum grain-filling rate (W_max) were the primary factors that influenced KW. Both G_mean and W_max were markedly affected by the effective accumulated temperature (AT), daily average temperature (MT), and precipitation (P_r) after silking. In this experiment, G_mean, W_max, and final KW increased along with MT and AT. A large amount of precipitation occurred during the grain filling period owing to the delayed sowing dates resulted in a decrease in G_mean and KW. AT was the major factor influencing grain-filling characteristics and KW, and a relatively prolonged growth period under early sowing conditions contributed to the increased effective accumulated temperature after silking, which was beneficial for grain filling. With sowing on April 6, higher KW and maize yield were obtained with better grain-filling performance when the effective accumulated temperature reached 863.36 °C. We concluded that suitable sowing dates should be established for the different planting systems used in maize cultivation. Spring maize should be sown as early as possible in the plain regions of the Sichuan Basin from the end of March to the beginning of April. The relationship with the previous crop should be considered in summer sowing especially for areas where late sowing is unavoidable, with sowing being completed in early May to avoid the adverse effects of abnormal meteorological factors on grain filling.

Effects of exogenous 14-hydroxybrassinolide on floret development into grain and physiological characteristics of winter wheat

LIU Beicheng, DUAN Jianzhao, RONG Yasi, ZHANG Yanyan, HE Li, WANG Yonghua, GUO Tiancai, FENG Wei

2022, 30(7): 1143-1154. doi: 10.12357/cjea.20210622

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Abstract:
A high grain number per spike is the basis for achieving a high yield. Promoting spike and floret development, and reducing floret degeneration and abortion can effectively increase the development of fertile florets into more grains. Exploring the effect of spraying exogenous 14-hydroxybrassinosterol (14-HBR) on the development of wheat florets into grains contributes to increasing grains number per spike and improving yield. A field experiment of spraying 0.05 μmol∙L⁻¹ 14-HBR on wheat leaf surface at 20 days after jointing was conducted with multi-spike wheat cultivar ‘Yumai 49-198’ and large-spike wheat cultivar ‘Zhoumai 16’. The development of young spikes and florets, carbon and nitrogen metabolism enzymes in flag leaves, dry matter weight, soluble sugar and nitrogen contents of different organs, and yield components were measured to analyze the effect of exogenous 14-HBR on the optimization of spike and floret development, as well as the physiological mechanism of 14-HBR promoting grains number. The results showed that spraying exogenous 14-HBR increased the number of fertile florets and the setting rate of fertile florets and spikelets. The promoting effect was more obvious for the large-spike wheat cultivar ‘Zhoumai 16’. Spraying exogenous 14-HBR increased the activities of RuBisCo enzyme, sucrose phosphorylase, and sucrose synthase for carbon metabolism, and activities of glutamine synthetase and nitrate reductase for nitrogen metabolism in wheat flag leaf, which promoted the synthesis of photosynthetic products and the metabolism and accumulation of carbon and nitrogen. Overall, the promoting effect was higher for large-spike wheat cultivar ‘Zhoumai 16’ than multi-spike wheat cultivar ‘Yumai 49-198’. Spraying exogenous 14-HBR increased the contents of soluble sugar and nitrogen and dry matter accumulation of spike organ and non-spike organ, promoted the transport and distribution of soluble sugar to spike, and improved the C/N ratio of spike organs, which provided sufficient carbon nutrients for spike and floret development, and overall, the promoting effect was more effective for large-spike wheat cultivar ‘Zhoumai 16’. To analyze the effect of exogenous 14-HBR on the yield and yield components, spraying 14-HBR 20 days after elongation had little effect on spike number and thousand-grain weight, but a significant impact on grains number per spike and yield was observed. Spraying exogenous 14-HBR significantly improved the grains number per spike, which was the main way to increase the yield. Compared with CK treatment (no spraying 14-HBR but spraying water), for the spraying 14-HBR treatment of multi-spike wheat cultivar ‘Yumai 49-198’ and large-spike wheat cultivar ‘Zhoumai 16’, the increase in grains number per spike was 9.85% and 11.40%, respectively, and the increase in yield was 9.31% and 12.03%, respectively. Spraying exogenous 14-HBR mainly improved the carbon assimilation ability of wheat, enhanced nitrogen absorption and accumulation, and promoted the transport and distribution of carbon nutrients to spike organs, thereby providing a good material basis for the two-stage differentiation of florets, reducing the degradation and abortion of florets, and increasing the number and rate of floret settings.

Quantitative mechanism analysis of the improved P availability in red soil during maize/soybean intercropping

WANG Ruixue, SU Lizhen, ZHANG Lianya, WANG Sirui, WANG Jing, XIAO Jingxiu, ZHENG Yi, TANG Li

2022, 30(7): 1155-1163. doi: 10.12357/cjea.20210636

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Abstract:
Intercropping has been shown to improve P availability in red soil, but a quantitative mechanistic analysis of the relationships between soil biological activity and P availability has not been conducted in field experiments. The aim of this study was to determine the specific effect of soil biological activity on P availability in red soil. In this study, maize/soybean intercropping and maize monocropping with four P application levels [0 kg(P₂O₅)∙hm⁻², 60 kg(P₂O₅)∙hm⁻², 90 kg(P₂O₅)∙hm⁻², and 120 kg(P₂O₅)∙hm⁻², labeled as P0, P60, P90, and P120, respectively] were used to analyze P availability and its relationship with major soil factors during a 4 year field experiment, which compared the values in the first and last years (2017 and 2020). Regression, redundancy, and structural equation model analyses were conducted to determine these relationships. The results showed that the land equivalent ratio of dry matter mass (LER) and land equivalent ratio of P uptake (LERp) were both greater than 1, indicating that intercropping increases biomass production and P uptake of crops. LER significantly (P<0.05) decreased with an increase in P application level in 2020, but LERp did not. This indicates that the advantage of P absorption in intercropping was not affected by P level, and low P levels still had the ability to maintain this advantage. Compared with monocropping, intercropping significantly (P<0.05) increased the soil available P content in maize rhizosphere; the increasing amplitude was from 24% to 103%, and the role of planting pattern changed from a significant level (P<0.05) in 2017 to an extremely significant level (P<0.01) in 2020. This indicates the effects of intercropping and P application on maize rhizosphere P availability in red soil with low fertility over multiple planting years. Regression analysis showed that the slope of the linear relationship between both Olsen-P and microbial biomass P (MBP) with maize P absorption in 2020 was lower than that in 2017 under monoculture (varied from 4.73 to 4.42 in Olsen-P and 19.68 to 7.16 in MBP), whereas the slope increased under intercropping (varied from 4.12 to 4.44 in Olsen-P and 13.72 to 17.78 in MBP). Redundancy analysis showed that the increase in soil available P and microbial biomass carbon (MBC) accounted for P absorption varied from 37.6% and 10.0% in monoculture to 33.3% and 13.8% in intercropping, respectively. This result shows that intercropping decreased the effect of available P on P uptake and increased the role of MBC. Through structural equation model analysis, increasing the activity of alkaline phosphatase was found to directly increase the content of soil available P, whereas acid phosphatase could increase soil available P by increasing MBP. These two enzymes are speculated to affect P availability in rhizosphere soil via different mechanisms. Therefore, under low P application levels, intercropping can enhance P availability in red soil by increasing soil microbial biomass and phosphatase activity in the maize rhizosphere, thus maintaining the dry matter mass and phosphorus uptake of maize. The quantitative contribution of microbial processes should be further studied.

Promoting effect of potato intercropping on functional diversity of soil microbial metabolism and nitrogen regulation

WANG Ding, LI Huan, YI Wenbo, CHEN Linkang, ZHAO Ping, LONG Guangqiang

2022, 30(7): 1164-1173. doi: 10.12357/cjea.20210604

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Abstract:
Intercropping is an efficient model for utilizing time and space resources and is a typical diversified agriculture cropping pattern. However, how the diversified planting of aboveground crops affects subsurface microbial diversity and N regulation remains uncertain. Therefore, in this study, the Biolog-EcoMicroPlate cultivation method was used to analyze soil microbial metabolic activity, diversity, and utilization of six carbon sources in potato mono- (MP) and inter-cropping (IP) soils under four N levels (N0, 0 kg∙hm⁻²; N1, 62.5 kg∙hm⁻²; N2, 125 kg∙hm⁻²; and N3, 187.5 kg∙hm⁻²). The results showed that compared with N0 treatment, N application (N1, N2, and N3 treatments) increased the average well color development (AWCD) values by 32.1%–100.2%, Shannon index by 3.3%–7.1%, and Simpson index by 14.8%–19.2%, and the increase peaked at the N1 treatment. Compared to potato monocropping under the same N application rates, potato intercropping with maize increased AWCD values and Shannon and Simpson indices, but there was a statistically significant difference only in the N0 treatment (P<0.05). Moreover, N application significantly affected the microbial metabolic activity of the six carbon sources (P<0.05). N application increased the microbial utilization of the six carbon sources, except for carbohydrates in monocropping soil. N application increased the microbial utilization of polymers, amines, and phenolic compounds (recalcitrant carbon sources), but decreased the utilization of carbohydrates, carboxylic acids, and amino acids (active carbon sources) in intercropping soil. The Mantel test showed that soil temperature, soil water content, soil organic carbon, soil ammonium N, and potato biomass were the main factors affecting the microbial AWCD values and diversity indices; however, ammonium N only had a significant effect on potato intercropping soil (P<0.05). Furthermore, the average clustering coefficient value in monocultured soil (0.930) was slightly higher than that in intercropped soil (0.907), indicating that potato intercropping with maize weakened the stability of soil microbial metabolic processes compared with potato monocropping ecosystem, leading to microbial carbon metabolism being more sensitive to changes in the soil microenvironment and further weakening the promoting effect of intercropping. Overall, diversified planting of aboveground crops increased subsurface microbial metabolic activity and diversity; however, this process was significantly regulated by N application. This indicates that a reasonable aboveground diversity could accelerate the soil carbon cycle and realize the efficient utilization of soil nutrients and sustainable agricultural development.

Effect of iron plaque controlling techniques on iron plaque formation on rice (Oryza sativa) root surface and accumulation of selenium in grains under acidic soil condition

YANG Xujian, TIAN Yuhao, SHEN Hong

2022, 30(7): 1174-1185. doi: 10.12357/cjea.20210629

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Abstract:
Iron plaque (IP) is a colloidal membrane consisting of iron (hydr)oxides formed on the root surface of rice (Oryza sativa), which not only enhances the adaptation of roots to the surrounding waterlogging but also affects nutrient uptake by rice. However, further exploration of methods to increase the Se accumulation in rice grains by regulating IP formation on the rice root surface is needed. Experiments on rice plants with different levels of phosphate-iron ratios (P/Fe), urea peroxide (UP), and alternation of wetting and drying (AWD) treatments were conducted under pot cultivation with mildly acidic (pH = 6.1) soil conditions to investigate the effects of these three IP-controlling techniques on IP formation and Se accumulation in grains. The results indicated that the IP content on the root surface and the grain Se content after a 1∶5 P/Fe treatment were significantly higher than that after a 1∶0 P/Fe treatment. The IP content and grain Se content after 90 kg∙hm⁻² UP treatment were significantly higher than that without UP. When P/Fe was less than 1∶3 or the UP dose was greater than 60 kg∙hm⁻², the variation trend of the grain Se content became steady. In addition, the IP content and grain Se content after long-term waterlogging treatment were remarkably higher than those of the control (irrigation to maintain a shallow water layer on the soil surface before naturally drying at the grain-filling stage) and AWD treatments. Although the IP content after one cycle of AWD treatment was lower than that after long-term waterlogging, the grain Se contents were similar. Correlation analysis suggested that both amorphous and crystalline IP contents presented a significant linear correlation with the grain Se content under the P/Fe and UP treatments, whereas this phenomenon did not occur under the AWD treatment. However, the linear coefficient of the correlation between the grain Se content and crystalline IP content was higher than that between the grain Se content and amorphous IP content under the P/Fe treatment, whereas the result was the opposite in the UP treatment. In orthogonal experiments, the IP controlling techniques harvesting the highest IP formation and the most remarkable increase in the grain Se content were the treatment combination of P/Fe of 1∶1, UP of 90 kg∙hm⁻², and long-term waterlogging. The grain Se content after this treatment combination was 0.116 μg∙g⁻¹, which was 2.01 times greater than that of the control (1∶0 P/Fe, no UP application, and conventional water management). The analysis of variation indicated that the effect sequence of the three controlling techniques on the IP content and grain Se content was UP>AWD>P/Fe. The effect of the P/Fe ratio on the IP content and grain Se content under this combination treatment could be neglected. In summary, IP controlling techniques, including regulating P/Fe, applying UP, and conducting AWD treatment, can promote IP formation on the root surface and Se accumulation in roots, thereby increasing Se accumulation in rice grains. The results of this study are scientifically relevant for Se-enriched rice production.

Comparative study on the growth and Cd uptake of Suaeda salsa and Suaeda glauca under the stress of salt and Cd and their interaction

WU Yujie, FENG Xiaohui, ZHANG Rui, LI Jing, LIU Xiaojing

2022, 30(7): 1186-1193. doi: 10.12357/cjea.20210778

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Abstract:
Remediation of heavy metal-contaminated saline-alkali soil by halophytes is a cost-effective and environmentally friendly method, but there is less information on the comparative study of different halophytic species under salt and heavy metal stresses. In this study, hydroponic experiments were conducted to compare the effects of salt and Cd interactions on the growth and Cd uptake between two typical leaf succulent halophytes, Suaeda salsa and Suaeda glauca, and to explore the regulatory effect of salt on Cd absorption. There were four treatments with two salt levels (0 and 10 g·L⁻¹NaCl) and two Cd levels (0 and 5 mg·L⁻¹Cd). The results showed that Cd treatment significantly inhibited the growth of the two plants and reduced leaf succulence and root-to-shoot ratio. Additionally, the inhibitory effect was greater on S. salsa than on S. glauca, especially with respect to root growth. Salt treatment promoted the shoot growth of both plants, and the promotion effect on shoot growth was significantly greater in S. salsa than in S. glauca. However, the root growth of S. glauca was significantly inhibited. The salt treatment under Cd stress significantly alleviated the inhibitory effect of Cd on the growth of both plants, and the alleviation effect on S. salsa was greater than that of S. glauca, especially on the root growth of S. salsa. There was no significant difference in shoot Cd content between S. salsa and S. glauca under Cd stress, but the Cd content in the shoots of the two plants was significantly reduced by salt treatment. The Na⁺ content and Na⁺/Cd ratio in the shoots of S. salsa were higher than those in S. glauca, but the K⁺ content, K⁺/Na⁺ ratio, and K⁺/Cd ratio were significantly lower than those in S. glauca. Salt treatment significantly promoted Na⁺ absorption in the shoots of both plants, and Cd treatment further promoted Na⁺ absorption in the shoots. Salt treatment reduced shoot K⁺ content and K⁺/Na⁺ ratio in both plants; these values were higher in S. glauca than in S. salsa. There was a tendency for shoot proline content to increase in both species under salt and Cd stresses, but there were no significant differences among species, salt, and Cd treatments. The shoot soluble sugar content of S. salsa was significantly higher than that of S. glauca under no stress and Cd treatment. Salt treatment significantly decreased the shoot soluble sugar content of S. salsa and increased that of S. glauca. Cd treatment increased the shoot soluble sugar content in both species, especially that in S. glauca. The above results show that the growth of S. salsa and S. glauca have different responses to salt, Cd, and their interactions. Salt can alleviate the inhibitory effect of Cd on growth, especially the inhibitory effect of Cd on root growth of S. salsa. S. salsa tends to accumulate inorganic osmotic regulators such as Na⁺, whereas S. glauca tends to accumulate inorganic osmotic regulators such as K⁺ and organic osmotic regulators such as soluble sugars to resist salt and Cd stress.

Effect of Tamarix ramosissima biochar on infiltration characteristics of saline water in coastal saline soil

LIU Congcong, DONG Xinliang, GUO Kai, CHENG Dongjuan, SUN Hongyong

2022, 30(7): 1194-1202. doi: 10.12357/cjea.20210578

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Abstract:
Biochar has great potential for improving saline soil quality owing to its high porosity and organic carbon content. However, biochar was prepared from a halophyte (Tamarix ramosissima), which has rarely been used to improve saline soil quality, for exploring the characteristics of saltwater infiltration in saline soil. In this study, a soil column simulation method was used to study the effects of T. ramosissima biochar addition (mass fractions of 0, 1.1%, and 3.3%) and saltwater with different salinities (0, 5, and 10 g·L⁻¹) on water infiltration characteristics and water and salt distribution in saline soil. The results showed the following. 1) With an increase in the biochar addition amount and salinity of saltwater, the migration time of the wet front decreased by 34.40%–85.85%, and the infiltration rate increased by 6.71%–87.30%; moreover, the effect of biochar addition on the water infiltration characteristics of saline soil was greater than that of saltwater. 2) The addition of biochar increased the water content of 0–10 cm soil by 1.29%–9.23%. 3) After water infiltration, the soil salt content at 0–40 cm depth decreased significantly compared with the initial soil salt content, and the salt content in saline soil increased with the increase in salinity of saline water; however, no significant difference was found. The salt content was highest at a depth of 50–60 cm, and it increased significantly with the increase in biochar addition amount and salinity of saltwater, which increased by 5.21%–35.11% compared with the control group without biochar after fresh water infiltration. In conclusion, under different salinity saltwater infiltration conditions, T. ramosissima biochar addition can accelerate soil salt leaching, and its leaching effect noticeably increasing with an increase in the amount of added biochar. In this study, the effect was observed at an optimal addition of 3.3% of biochar. And the results for rational application of biochar and saltwater resource utilization in coastal areas provide the necessary theoretical basis.

Effect analysis of road structure on multidimensional fragmentation of cultivated land: A case study in the international metropolis of Shanghai City

LI Shiyao, CAI Yinying

2022, 30(7): 1203-1214. doi: 10.12357/cjea.20210707

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Abstract:
Cultivated land fragmentation (CLF) is an important factor restricting agricultural scale production and modernization development. Recent studies have revealed that CLF is a multidimensional problem. A systematic study of the spatial distribution and driving factors of multidimensional cultivated land fragmentation (MCLF) has practical meaning for preserving high-quality farmland in suburbs and restraining urban land expansion. Taking the suburbs of the international metropolis of Shanghai City as an example, this article used canonical correlation analysis to calculate the effects of road structure on the MCLF in urban fringe, rural fringe and rural areas. The results showed that there was spatial heterogeneity in the degree of MCLF in the Shanghai suburbs in 2015. The size and distribution characteristics of CLF mainly occurred near the center of the main city, while the shape characteristics of CLF mainly occurred on the southeast coast. In addition, there was no positive correlation between road density and the degree of MCLF. Without the highest road density, the rural fringe had the highest level of distribution characteristics of CLF. Furthermore, the MCLF was affected by the road structure in heterogeneous zones. The higher density of the fourth-class road density represented a lower degree of the size characteristics of CLF in the urban fringe, and a higher density of the third-class road represented a higher degree of the distribution characteristics of CLF in the rural fringe. In rural areas, the area with a lower density of higher roads and a higher density of lower roads showed a lower CLF in terms of size characteristics and a higher CLF in terms of shape characteristics, while the area with a higher density of higher roads and a lower density of lower roads showed a higher CLF in terms of distribution characteristics. These discoveries enlightened us that to relieve the stress of cultivated land protection and achieve the goal of sustainable land use, we need to be explicit about the main challenges of regional cultivated land protection and consider the potential risks of road construction to the MCLF in the process of road planning and design.

2022 Vol. 30, No. 7