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    15 February 2022, Volume 33 Issue 2
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    Population structure and dynamics of Pinus koraiensis seedlings regenerated from seeds in a montane region of eastern Liaoning Province, China.
    ZHANG Xiao-peng, YU Li-zhong, YANG Xiao-yan, HUANG Jia-qi, YIN You
    2022, 33(2):  289-296.  doi:10.13287/j.1001-9332.202202.001
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    Based on the static life table and survival curve, we explored the population structure and dynamics of Korean pine (Pinus koraiensis) seedlings regenerated from seeds in three different forest belts of Korean pine plantation in a montane region of eastern Liaoning Province. The results showed that the age structure of Korean pine seedlings in three different forest belts (i.e., larch forest belt, mixed coniferous forest belt, and mixed broadleaved forest belt) showed a “∩” type of left skewed distribution. The abundance of seedlings was rich but the mortality rate was high in the early phase, and the abundance of seedlings decreased in the later phase, which indicated that the population was depressing. The survival curve of the population conformed to the Deevey-Ⅱ type. The life expectancy of Korean pine seedlings at each age class in larch forest belt was higher than that in mixed coniferous forest belt and mixed broadleaved forest belt. The survival analysis showed that the survival rate of Korean pine seedlings in three different forest belts decreased but the cumulative mortality rate increased with increasing age. The death density function tended to be flat after the age class of Ⅱ-Ⅲ, while the risk function value showed a decreasing trend with the increases of age. The time series predictive analysis showed that the population showed a certain growth trend with increasing age class, indicating that the population could achieve natural regeneration and have a certain growth potential, but with regeneration obstacles.
    Regeneration characteristics of three natural Juniperus forests in the Three-River Headwater Region of Qinghai Province, China
    HUANG Ting, HAO Jia-tian, DU Yi-chen, TIAN Cui-cui, ZHANG Jing, WANG Hai, HOU Lin
    2022, 33(2):  297-303.  doi:10.13287/j.1001-9332.202202.006
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    The aims of this study were to clarify the regeneration characteristics and dominant factors affecting the regeneration of three natural Juniperus forests in the Three-River Headwater Region of Qinghai Province, and thus to provide a reference for the protection and management of natural forests. We evaluated the natural regeneration levels of Juniperus forests, and the effects of stand factors and soil factors on natural regeneration. The results showed that three natural Juniperus forests were poorly regenerated, with insufficient regeneration potential. The average regeneration density of J. tibetica forest, J. przewalskii forest and J. convallium forest was 332, 279 and 202 ind·hm-2, respectively. The height range of regenerate individuals was concentrated in 1-3 m. Only a few seedlings (12 ind·hm-2) were found under the J. tibetica forest, and no seedlings were found under the J. convallium and J. przewalskii forests. The regeneration density of J. tibetica forest was significantly positively correlated with stand density, soil organic matter and available phosphorus, and negatively correlated with shrub coverage. The regeneration density of J. convallium forest was significantly negatively correlated with herb coverage, human disturbance degree, woodland slope and soil total nitrogen, and positively correlated with soil water content. The regeneration density of J. przewalskii forest was significantly positively correlated with stand density, soil available potassium and available phosphorus, but negatively correlated with herb coverage. Results of multiple regression analysis showed that the regeneration of J. tibetica forest was mainly affected by understory shrub coverage and soil available phosphorus, that of J. convallium forest was mainly affected by understory herb coverage, soil total nitrogen and human disturbance, and that of J. przewalskii forest was mainly affected by understory herb coverage and soil available potassium. It was necessary to strengthen forest enclosure, management and protection, rationally regu-late the coverage of understory vegetation, increase soil fertility and improve biotope in the forest, which would promote the protection and natural regeneration of natural Juniperus forests in the Three-River Headwater Region.
    Water use efficiency and leaf nutrient characteristics of five major tree species in broadleaved Korean pine forest in Changbai Mountains, China
    TIAN Jin-yuan, YUAN Feng-hui, GUAN De-xin, WU Jia-bing, WANG An-zhi
    2022, 33(2):  304-310.  doi:10.13287/j.1001-9332.202202.007
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    Water use efficiency (WUE) of five dominant tree species (Pinus koraiensis, Fraxinus mandshurica, Acer mono, Quercus mongolica, and Tilia amurensis) was estimated using the stable carbon isotope method in a broadleaved Korean pine forest in Changbai Mountains. Leaf carbon (C), nitrogen (N), and phosphorus (P) contents were measured to analyze nutrient utilization of the dominant species. The relationship between WUE and leaf nutrient contents was systematically assessed. WUE was different due to the variations of micrometeorological factors at different locations in the canopy. The four broadleaved tree species showed upper layer > middle layer > lower layer, while P. koraiensis showed upper layer > lower layer > middle layer. WUE of evergreen coniferous P. koraiensis was higher than that of two broadleaved species with diffuse-porous wood (T. amurensis and A. mono) and lower than that of two broadleaved species with ring-porous wood (F. mandshurica and Q. mongolica). The compound-leaved species (F. mandshurica) had the highest WUE. The WUE of new leaves was significantly higher than old leaves in P. koraiensis. The carbon content and C/N of the old and new leaves of evergreen coniferous P. koraiensis were significantly higher than those of the other four broadleaved tree species, while nitrogen content and N/P were significantly lower than those of the four broadleaved tree species. P content of old leaves of P. koraiensis was significantly lower than that of the four broadleaved tree species. P content of new leaves of current year was not significantly different from that of the broadleaved tree species. The WUE of five tree species had a poor correlation with leaf C content, but a positive correlation with leaf N content. The WUE of evergreen coniferous and deciduous broadleaved tree species was correlated with leaf P content but in opposite direction.
    Characteristics of nutrient accumulation and vertical spatial distribution in Cunninghamia lanceolata plantation with different stand densities
    DAI Lin-li, CHEN Yi-tang, WU Li-hua, LIU Li, YE Yi-quan, QIU Jing-wen, CAO Shi-jiang, CAO Guang-qiu
    2022, 33(2):  311-320.  doi:10.13287/j.1001-9332.202202.002
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    The growth, biomass, nutrient content and accumulation as well as the vertical distribution of nutrient accumulation in Cunninghamia lanceolata plantation across densities of 1800, 3000, 4500 trees·hm-2 were stu-died in order to provide scientific basis for efficient cultivation of C. lanceolata plantation. The total amounts of nutrients accumulated in C. lanceolata plantation with 1800, 3000, 4500 trees·hm-2 were 1311.57, 2531.55 and 2307.33 kg·hm-2, respectively. There were significant variations among different densities. Under the same density, the order of nutrient content and accumulation in C. lanceolata plantation was total N > total K > total Ca > total Mg > total P. Moreover, the amount of nutrients in trunk and bark decreased with the increases of tree height. The amount of nutrient accumulation in persistent withered branch and leaf were allocated from middle to the upper part of tree, while the opposite was observed for fresh branch and leaf. N accumulation increased with the increases of stand densities, while the other nutrients first increased then decreased. The order of the amount of nutrient accumulation in trunk, bark, root, persistent withered branch, persistent withered leaf and litter among different densities was 4500 > 3000 > 1800 trees·hm-2, and was 3000 > 1800 > 4500 trees·hm-2 in fresh branch and leaf, and 1800 > 3000 > 4500 trees·hm-2 in understory. Under the densities of 1800 and 4500 trees·hm-2, the nutrient distribution ratio in bark was the largest, accounting for 21.6% and 19.4%. In 3000 trees·hm-2, the distribution ratio of fresh leaves reached its maximum, accounting for about 22.9%, and the next was fresh branches, which had a distribution ratio of about 17.8%. 3000 trees·hm-2 was the most appropriate density for nutrient accumulation and distribution in C. lanceolata plantation.
    Effects of forest conversion on litterfall nutrient return and nutrient use efficiency in Mid-subtropical China.
    ZHANG Nan, YANG Zhi-jie, XU Chao, LIU Xiao-fei, XIONG De-cheng, LIN Cheng-fang
    2022, 33(2):  321-328.  doi:10.13287/j.1001-9332.202202.021
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    To understand the impacts of mid-subtropical forest conversion on carbon and nutrient cycling, we conducted a 4-year investigation to examine litterfall, nutrient return and nutrient use efficiency of Castanopsis carlesii natural forest, C. carlesii secondary forest and Cunninghamia lanceolata plantation which were transformed from C. carlesii natural forest. The results showed that after C. carlesii natural forest was transformed into C. carlesii secon-dary forest and C. lanceolata plantation, the annual litter production decreased by 29.0% and 45.7%, nitrogen return of litter decreased by 34.0% and 72.7%, and phosphorus return decreased by 38.1% and 56.4%, respectively. The amount of carbon returned from litterfall in C. carlesii natural forest was 25.6% and 44.3% higher than that in C. carlesii secondary forest and C. lanceolata plantation, respectively. For C. lanceolata plantation, C. carlesii secondary forest and C. carlesii natural forest, nitrogen use efficiency of litterfall was 175.4, 94.8 and 92.0 kg·kg-1, respectively, and phosphorus use efficiency of litterfall was 3031.0, 2791.6 and 2537.2 kg·kg-1, respectively. It was concluded that C. lanceolata plantation was more limited by nitrogen compared with C. carlesii natural forest and secondary forest, and the effects of phosphorus limitation had similar effects on the three forests.
    Functional traits of leaves with different ages of Taxus wallichiana var. chinensis saplings.
    YANG Ke-tong, CHEN Guo-peng
    2022, 33(2):  329-336.  doi:10.13287/j.1001-9332.202202.003
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    Variations of functional traits with leaf age reflect plant life history strategy and indicate allocation pattern and trade-off characteristics in the limiting resource. In this study, leaves with different ages of Taxus wallichiana var. chinensis saplings were taken as experimental materials. Fourteen leaf functional traits of leaves at three differebt ages were measured in order to reveal changes of the saplings' ecological strategies with leaf aging. The results showed that one-year-old leaves had significantly higher specific leaf area than two- and three-year-old lea-ves, while three-year-old leaves had significantly greater leaf thickness, leaf area, volume, fresh weight and dry weight than leaves at other ages. In addition, one-year-old leaves had significantly greater nitrogen content (N), phosphorus content (P) and N:P than two- and three-year-old leaves, but lower C:N than three-old-year leaves. The slope of allometric relationship between leaf water content and dry weight, leaf thickness and leaf area of one-year-old leaves, leaf thickness and leaf area of three-year-old leaves were all significantly lower than 1.0. Two-year-old leaves showed significantly allometric relationships between many leaf traits, with slope being not equal to 1.0. In conclusion, one-year-old leaves of T. wallichiana var. chinensis saplings tended to have higher photosynthetic capacity, two-year-old leaves had stronger dry matter accumulation, and three-year-old leaves would construct defense system. The coordination and complementation of functional traits among leaves with different ages might have great significance for maintaining individual homeostasis and survival.
    Effects of combined nitrogen and phosphorus addition on fine root traits of young Machilus pauhoi forest
    HE Rui-tong, ZHONG Quan-lin, LI Bao-yin, CHENG Dong-liang, XU Chao-bin, WANG Yan, YU Hua, CHANG Yun-ni
    2022, 33(2):  337-343.  doi:10.13287/j.1001-9332.202202.005
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    Both nitrogen (N) and phosphorus (P) are the main limiting elements for plant growth in terrestrial ecosystems. Fine roots play a critical role in plant growth. To reveal the effects of combined N and P addition on fine root traits of Machilus pauhoi, we performed a field N and P addition experiment in the midmonth from April to September in 2016 and 2017 in a 3-year M. pauhoi forest (N and P supply ratios were 8:1, 10:1, 12:1, 15:1). Both fine root morphological traits (specific root length, specific root area, average diameter, root tissue density) and stoichiometric traits (total carbon content, total nitogen content and carbon-nitrogen ratio) were analyzed. The results showed that the effects of combined application of N and P on fine root raits varied with seasons. In June, fertilization significantly increased specific root area, total nitrogen content and specific root length of 0-1 mm fine root, but decreased root tissuse density, carbon-nitrogen ratio and average diameter of 0-1 mm root. The most obvious change of fine root traits in June was found under the treatment with a N and P supply ratio of 12:1. In December, combined N and P addition significantly increased root tissue density, total nitrogen content, carbon-nitrogen ratio as well as fine root biomass with the diameter of 0-1 mm. The results of principal component analysis showed that different N and P supply ratios exerted different effects on the relationships among fine root traits. Fine root traits were distributed at both ends of Axis 1 when treated with 12:1 N:P, while distributed at Axis 1 and Axis 2 under other treaments. There was a significant negative correlation between fine root average diameter variation and the relative plant growh rate. The relationship among fine root traits, and between fine root traits and the relative growth rate of plant biomass were optimally coordinated at the treament with a N:P ratio of 12:1.
    Stem photosynthesis and its main influencing factors of Haloxylon ammodendron and Tamarix ramosissima.
    FENG Xiao-long, LIU Ran, LI Cong-juan, WANG Yu-gang, KONG Lu, WANG Zeng-ru
    2022, 33(2):  344-352.  doi:10.13287/j.1001-9332.202202.009
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    Stem photosynthesis (Pg) is an alternative and significant carbon source, playing a crucial role in plant survival under extreme environment. The main aims of this study were to quantify stem and leaf photosynthesis, find out the main drivers of Pg, and estimate the contributions of Pg to plant individual carbon balance of two dominant species Haloxylon ammodendron and Tamarix ramosissima in Gurbantunggut Desert. A Li-Cor 6400 portable photosynthesis system and a special chamber were used to measure leaf and stem photosynthesis. Ancillary measurements included leaf/stem functional trait (chlorophyll content, water content, leaf/stem area, carbon/nitrogen content, etc.) and environmental factors (air temperature and humidity, photosynthetically active radiation, soil temperature, and soil water content). Our results showed that Pg of H. ammodendron and T. ramosissima was 2.37 and 0.98 μmol·m-2·s-1, Pg refixation CO2 of stem respiration by 65%-76% and 57%-77% in H. ammodendron and T. ramosissima. Pg was influenced by photosynthetically active radiation, air temperature, soil temperature and water vapor deficit. Pg assimilation CO2 accounted for 8.2%-16.6% and 3.6%-8.3% of CO2 assimilation of H. ammodendron and T. ramosissima, respectively. The maximum value appeared at noon when temperature was high. There might be fundamental defects if we ignore the contribution of branch photosynthesis when predicting carbon process of desert ecosystem under the background of climate change.
    Water sources of Populus euphratica with different tree ages in the oasis of desert hinterland.
    WAN Yan-bo, SHI Qing-dong, DAI Yue, LI Tao, PENG Lei, LI Hao
    2022, 33(2):  353-359.  doi:10.13287/j.1001-9332.202202.008
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    Understanding vegetation water utilization can provide scientific basis for vegetation protection and rational distribution of water resources in arid desert oasis area. In this study, sapling (DBH≤10 cm), mature (10 cm<DBH≤40 cm), and overmature (DBH>40 cm) Populus euphratica were chosen as sample trees in natural oasis of Dariaboui. We measured oxygen isotopes of xylem water and potential water sources (surface water, soil water in 0-3 m soil layer and groundwater) of P. euphratica with different tree ages. The IsoSource model was used to study water sources of P. euphratica. The results showed that soil water content increased with increasing soil depth, while the δ18O value of soil water decreased firstly and then stabilized. When groundwater depth was 2 m, the δ18O value of xylem water increased with increasing tree ages. When the depths of groundwater were 4.2 and 8 m, the δ18O values of xylem water decreased with increasing tree ages. Water sources of P. euphratica varied across tree age. When the depth of underground water was 2 m, the main water source for young trees was surface water, and the contribution proportion was 64.7%. For mature and overmature trees, it was deep soil water and ground-water, with a contribution of about 30%. When the depth of groundwater was 4.2 m, the main water sources of P. euphratica of different tree ages were deep soil water and groundwater, and the contribution proportion was about 30%. The lowest contribution of P. euphratica of different tree ages was shallow soil water, accounting for about 10%.
    Comparison of root traits of Stipa krylovii and Allium polyrhizum under grazing in typical steppe.
    LI Tian-liang, HUO Guang-wei, WU Yun-na
    2022, 33(2):  360-368.  doi:10.13287/j.1001-9332.202201.005
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    Plant ecological adaptation is associated with root traits. To clarify the differences of root traits between two dominant species, Stipa krylovii and Allium polyrhizum, under different grazing intensities (light, moderate, and heavy grazing intensities), we measured root traits, including root length, root surface area, root diameter, root volume, root tips, root bifurcations, specific root length, and specific surface area. We analyzed the root morphological patterns of tip proportion, length proportion, surface proportion and volume proportion of both species, and examined their ecological adaptation strategies under grazing. The results showed that grazing inhibited aboveground and belowground growth of S. krylovii, but promoted belowground growth of A. polyrhizum. In addition, the effects of grazing on belowground part of S. krylovii was greater than aboveground part. These results indicated that the growth of S. krylovii was maintained by the aboveground part and that of A. polyrhizum was maintained by the belowground part under grazing. Root length, root bifurcations, root surface area and root tips were the main factors affecting root traits of S. krylovii, while root length, root surface area and root volume were the main factors affecting root traits of A. polyrhizum. S. krylovii could adapt to grazing stress by increasing length proportion, surface proportion and volume proportion of diameter class of 0-0.7 mm, while A. polyrhizum by increasing the length proportion, surface proportion and volume proportion of diameter class of 1.4-1.8 mm. The study on the differences of root traits between S. krylovii and A. polyrhizum could help provide a scientific basis for controlling grassland degradation.
    Effects of nutrient and water addition on soil inorganic phosphorus fractions in an old-field grassland
    ZHANG Yu-ge, LI Xin-yue, LIU He-yong, WANG Jin-huan, YUAN Xin, CAI Jiang-ping, WANG Ru-zhen, JIANG Yong
    2022, 33(2):  369-377.  doi:10.13287/j.1001-9332.202202.010
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    Reasonable nutrient and water management is effective ways to improve productivity and biodiversity of degraded grasslands. However, little is known about the effects of nutrient and water addition on soil inorganic phosphorus (P) fractions in old-field grasslands. Based on a field experiment with nutrient addition (N: 10 g·m-2·a-1, P: 10 g·m-2·a -1) and water addition (180 mm water irrigated during plant growing season) in Duolun County, Inner Mongolia in 2005, we examined the changes of inorganic P fractions and Olsen-P contents in the topsoil (0-10 cm). Results showed that 11-year P addition significantly increased total inorganic P (TIP) content, and that exogenous P was mostly transformed into calcium phosphate (Ca-P: 62.6%-69.2%), and then into aluminium phosphate (Al-P: 19.9%-25.1%), ferric phosphate (Fe-P) and occluded P (O-P). Phosphorus incorporated with nitrogen (N) addition significantly increased Fe-P and Al-P contents by declining soil pH and activating Fe3+ and Al3+ in soil. Water addition alone significantly increased Fe-P, Al-P, and decalcium phosphate (Ca10-P) fractions, and the contents of Fe-P, Al-P, octacalcium phosphate (Ca8-P), and Ca10-P were greater in P incorporated with water treatment than in P addition alone. There was no difference of each inorganic P fraction between P incorporated with N and water treatment and P incorporated with N treatment. Phosphorus and P incorporated with N additions significantly increased soil Olsen-P content, while water addition significantly decreased soil Olsen-P content under P addition alone and P incorporated with N treatment. In the calcareous soils, calcium superphosphate addition could enhance soil inorganic P pool through increasing Ca-P fraction.
    Effects of water levels in heterogeneous habitats on sexual reproductive allocation of Deyeuxia angustifolia.
    DONG Hai-peng, CAO Hong-jie, XIE Li-hong, HUANG Qing-yang, YANG Li-bin, NI Hong-wei, WANG Ji-feng
    2022, 33(2):  378-384.  doi:10.13287/j.1001-9332.202202.004
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    Taking Deyeuxia angustifolia as the research object, a representative plant of wetland in Sanjiang Plain, we analyzed the variations of individual size and biomass among the habitats of swamp wetlands, swampy meadows, typical meadows and miscellaneous grass meadows, and the relationship between reproductive components and plant biomass. We explored the effects of water level on individual biomass and reproductive allocation of D. angustifolia in different types of wetlands. The results showed that plant biomass, height and the characteristics of sexual reproduction significantly decreased with the increases of water level. The reproductive thresholds of D. angustifolia in miscellaneous grass meadow, typical meadow, swampy meadow, and swamp wetland were 0.245, 0.149, 0.148 and 0.157 g, respectively. There was a significantly negative correlation between plant size and reproductive allocation in three habitats except swampy meadow. Compared with individual size, soil water content had a stronger effect on reproductive allocation of D. angustifolia. The different investment between individual size and reproductive allocation in different habitats was the basic condition that contributes to the good ecological adaptability of D. angustifolia.
    C:N:P stoichiometry in plants and soils of Phragmites australis wetland under different water-salt habitats
    BIAN Fu-hua, WU Qiu-tang, WU Meng-di, GUAN Bo, YU Jun-bao, HAN Guang-xuan
    2022, 33(2):  385-396.  doi:10.13287/j.1001-9332.202202.040
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    We examined the effects of channel diversion of Yellow River on the content and stoichiometry of carbon (C), nitrogen (N) and phosphorus (P) in the organs of reeds (stem, leaf, rhizome and fibrous root) and soils in three typical Phragmites australis communities in the Yellow River Delta, including P. australis community in the former Yellow River course abandoned in 1996, P. australis community on the new Yellow River course and the P. australis communities on the intertidal area (far from the abandoned and current channel but affected by the tides). The results showed that foliar C, N and P contents of P. australis were highest in the communities of abandoned Yellow River course. Leaf N, stem C and rhizome P contents were highest in the communities of new Yellow River course. Leaf N and stem C and P contents were highest in the communities of intertidal area. The average leaf C (409.48 g·kg-1) and P (1.09 g·kg-1) contents in the three habitats were lower than national and global average levels, while leaf N content (21.71 g·kg-1) was higher than that of national and global average levels. The mean leaf N:P (20.22) was higher than 16 and the mean soil N:P (0.87) was lower than 14, indicating that the P. australis growth in the three habitats was limited by P. Correlation analysis showed that EC was one of the main factors affecting C:N:P stoichiometry in P. australis. In general, the C and P reserves in P. australis in the study area were low, and N reserve was high. The soil organic carbon content was low, the soil C reserves were large, while the N and P were relatively scarce.
    Changes of the area of Spartina alterniflora and mangroves in Guangxi Shankou Mangrove National Nature Reserve from 1995 to 2019.
    SHEN Hong-kun, ZHAO Bo-yi, CHEN Ming-yang, HUANG Rong-yong, YU Ke-fu, LIANG Wen
    2022, 33(2):  397-404.  doi:10.13287/j.1001-9332.202202.015
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    Given its high root regeneration ability and adaptation capacity, Spartina alterniflora would predominate the resource competition with other plant species. As an invasive alien species, it has caused serious damages to the coastal ecosystem of China. We explored the impacts of S. alterniflora invasion on the growth and expansion of mangroves around the coastal zones around Guangxi Shankou Mangrove National Nature Reserve (GSMNNR). The area of S. alterniflora and mangroves in the GSMNNR was analyzed based on a sequence of Landsat satellite multispectral images collected during 1995 to 2019. The results showed that S. alterniflora predominated in the competition with mangroves without human intervention. The area of S. alterniflora decreased under the conditions of cutting, rooting and other management measures, while the average annual growth rate of mangrove area correspondingly increased. It indicated that the invasion of S. alterniflora would inhibit the growth and expansion of mangroves. The S. alterniflora management measures, such as mowing and rooting, could weaken the negative impacts of S. alterniflora on mangroves. Mangroves could thus be effectively protected. This study could provide quantitative scientific data for S. alterniflora management and the protection of the mangrove ecosystem in the GSMNNR, and thus be a valuable reference to the prevention on a larger scale of S. alterniflora and the formulation of further protective measures for mangroves.
    Effects of planting methods on the utilization of temperature and sunshine resources and yield of rice under cabbage/rape-paddy cropping system.
    SHEN Jie, LYU Teng-fei, WANG Zhi-qiang, WANG Zhong-lin, LIN Dan, LI Yu, YANG Zhi-yuan, SUN Yong-jian, MA Jun
    2022, 33(2):  405-414.  doi:10.13287/j.1001-9332.202201.024
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    Light simplified cultivation and high quality rice are the main directions of rice production in China. Meteorological factors are the most important environmental factors affecting rice growth and yield. Few studies examined the relationship between rice yield and microclimate under different light simplified cultivation modes. To explore the relationship between rice yield and climatic factors (temperature, sunshine and water) at different growth stages of hybrid rice under different forecrops in southwest China, we carried out a split-plot design experiment in 2019 and 2020, with two forecrops of green cabbage and rape as the main plot, and three planting methods, direct-seeding, blanket-transplanting, and artificial transplanting as the subplots, taking Yixiangyou 2115 as the experimental variety. Results showed that compared with rape-paddy cropping system, cabbage-paddy cropping system significantly improved the accumulated temperature and precipitation production efficiency and consequently improved the effective panicles, setting rate, and 1000-grain weight. The yield was increased by 12.7% and 8.3% under cabbage-paddy and rape-paddy cropping system, respectively. Compared with manual transplanting, mechanical transplanting improved effective panicles, production efficiency of radiation, accumulated temperature and precipitation, and the radiation use efficiency of grain during the whole growth period. The mean yield was increased by 4.6% in 2019 and 2020. However, the above parameters of direct-seeding significantly decreased, but the yield decreased by 8.7%. Compared with 2019, mechanical transplanting and artificial transplanting were sown one month earlier in 2020 under the same stubble, which shortened growth period, reduced air temperature, and increased precipitation after flowering, leading to a significant decrease in effective accumulated temperature and light radiation; production efficiency of accumulated temperature, light energy, and precipitation; and utilization efficiency of light energy of grain, spikelets per panicle, setting rate, and 1000-grain weight. However, the yield was significantly reduced. Partial least squares regression analysis was used to establish the production forecast equation of standardized regression coefficients of meteorological factors. There was a positive correlation between rice yield and effective accumulated temperature and total radiation during the growth stage or the whole growth period. In addition, there was a significant negative correlation between rice yield and precipitation during the whole growth period. In conclusion, mechanical transplanting under cabbage-paddy cropping system was a rice planting method that optimised the seasonal sunshine and temperature resources in southwest China. The method facilitated the full utilization of temperature and sunshine resources, resulting in high yield. However, it was not advisable to sow or transplant too early.
    Effects of long-term different fertilization patterns on soil nutrients and microbial community structure of tomato in a solar greenhouse.
    LI Lin, XIANG Dan, WU Ya-fen, HUANG Yu-dan, LI Huan, ZHANG Xiao-mei, LIANG Bin
    2022, 33(2):  415-422.  doi:10.13287/j.1001-9332.202202.027
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    The phospholipid fatty acid (PLFA) technique was used to investigate the effects of fertilization on soil characteristics and microbial community of tomato in a solar greenhouse in Shouguang, Shandong Province, China, based on a long-term (12-year) fertilization experiment. The experiment involved a control (CK) and five fertilization treatments, namely, traditional nitrogen application (CN), traditional nitrogen application+straw return (CNS), optimized nitrogen application (SN), optimized nitrogen application+straw return (SNS), and organic manure nitrogen application+straw return (MNS). Results showed that the contents of soil organic matter and avai-lable P and K under all fertilization treatments were significantly higher than that of CK, but no significant difference among fertilization treatments. The traditional nitrogen application (i.e., CN and CNS) significantly decreased soil pH. The reduction of nitrogen fertilizer (i.e., SN, SNS and MNS) did not affect soil pH. Compared with CK, no straw treatment (i.e., CN and SN) and MNS did not affect the content of soil available N, but nitrogen combined with straw returned (i.e., CNS and SNS) significantly increased soil available N content. The optimized N with straw return (i.e., SNS) treatment resulted in the highest soil available N. Compared with CK and treatments without straw (i.e., CN, SN), treatments with straw (i.e., MNS, CNS and SNS) substantially changed soil microbial community structure and increased the biomass of soil bacteria, fungi, actinomycetes, mycorrhizal fungi, and the total amount of PLFA. SNS treatment had the highest soil microbial diversity, the highest biomass of soil bacteria, fungi, and actinomycetes, the highest total amount of PLFA, the highest ratios of fungi/bacteria and monounsaturated fatty acids/saturated fatty acids (MONO/SAT), the two indicators for soil ecosystem stability. Further, it had the lowest ratios of iso/anteiso fatty acids (i/a) and gram-positive/gram-negative bacteria (G+/G-), the indicators for nutritional stress. Redundancy and correlation analysis revealed that soil organic matter was the main factor affecting soil microbial community structure, with a significant positive correlation with actinomycetes and gram-positive bacteria. In conclusion, straw returning combined with optimized nitrogen application (i.e., SNS, 8 t·hm-2 of wheat straw with N fertilizer reduced by 58.3%) could improve soil nutrient status, soil microbial biomass, soil microbial community structure, and soil ecological environment. It would be an effective measure for reducing fertilizer application and improving efficiency.
    Effects of Bacillus fertilizer and agent on growth of young peach tree and soil environment under replant condition.
    YANG Shu-na, GAO Zhi-yuan, XI Xin-yan, WANG Li, YIN Yi-ming, YAO Ying, JIA Hui-juan
    2022, 33(2):  423-430.  doi:10.13287/j.1001-9332.202202.026
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    We analyzed the effects of Bacillus fertilizer and agent supplementation at different concentrations in the replanted soil by examining the growth of young peach trees, soil nutrients, enzyme activities, and fungal commu-nity. The aim of this study was to provide theoretical basis for alleviating peach replant diseases. One-year-old potted ‘Yuanmeng' peach trees were subjected to eight treatments: replanted soil without supplementation (RS), non-replanted soil without supplementation (NS), replanted soil with 1%, 4%, 8% Bacillus fertilizer supplementation (BF1, BF2, BF3), and 0.1‰, 0.5‰, 1‰ Bacillus agent supplementation (B1, B2, B3), respectively. The results showed that shoot growth and root biomass under NS treatment were greater than that under other treatments, and the contents of soil organic matter, available nutrients and soil catalase activity were greatly enhanced. Peach trees treated with BF and B treatments showed better root development than RS, among which, BF3 and B1 treatments were the best, and B1 treatment had similar effects as NS treatment. Compared with RS, BF and B treatments significantly increased the activities of soil catalase and urease during new shoot development, while B treatment significantly increased soil sucrase activity after the growth cessation of new shoots. Bacillus fertilizer and agent increased soil fungal diversity and the relative abundance of Ascomycota, Chaetomium and Penicillium, and decreased that of Basidiomycota. Considering the comprehensive parameters, BF3 and B1 showed more significant effects. In summary, our findings indicated that the supplementation of Bacillus fertilizer and agent to replanted soil could improve soil fertility, fungal community, and root development of roots, and thus provided a feasible method to alleviate peach replant diseases.
    Effects of manure substituting chemical nitrogen fertilizer on rubber seedling growth and soil environment.
    LI Jia-le, LIANG Yong-yi, LIU Wen-jie, YANG Qiu, XU Wen-xian, TANG Shui-rong, WANG Jing-jing
    2022, 33(2):  431-438.  doi:10.13287/j.1001-9332.202202.028
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    The substitution of manure for chemical nitrogen fertilizers has great impacts on the growth of rubber seedlings and soil environment, with implications for rubber cultivation and transplantation and soil environment improvement. In this study, rubber seedlings of thermal research ‘7-33-97' strain were cultivated under four treatments: No fertilizer application (CK), only application of chemical fertilizer (N), manure replacing 50% chemical fertilizer (M+N), and manure replacing 100% chemical fertilizer (M). Plants parameters (including plant height, basal diameter, biomass, and chlorophyll), soil physicochemical properties (including pH, soil organic carbon and nitrogen, soil enzyme activities), and their relationships were investigated. The results showed that plant height, basal diameter, biomass, and chlorophyll content in the M+N and M treatments were significantly higher, while underground biomass and root-shoot ratio were significantly lower than those of in N treatment. Compared with CK, soil pH was significantly increased in the M treatment, decreased in the N treatment, and was not changed in the M+N treatment. Soil ammonium and nitrate content in the M+N and M treatments were significantly lower, while soil organic carbon content, the activity of β-1,4-glucosidase (BG), β-1,4-N-acetylglucosaminidase (NAG) and leucine aminopeptidase (LAP) were significantly higher than those of in N treatment. Results of correlation analysis showed that soil pH was negatively correlated with soil ammonium and nitrate content, but positively correlated with BG and NAG activities. The structural equation model analysis showed that soil pH had significant positive effects on seedling quality index, while nitrate content had significant negative effects, and soil enzyme activities had no significant effect. Those results indicated that soil pH and nitrate content were the important driving factors on the growth of rubber seedlings. The manure replacing of 50% and 100% chemical nitrogen fertilizer could promote rubber seedlings growth, improve soil environment, and promote sustainable development of rubber production in Danzhou City, Hainan Province.
    Variation characteristics of plant electrical signal and their relationship with negative air ion under different light intensities.
    SHI Guang-yao, SANG Yu-qiang, ZHANG Jin-song, CAI Lu-lu, ZHANG Jia-xing, MENG Ping, XUE Pan, QIAO Yong-sheng
    2022, 33(2):  439-447.  doi:10.13287/j.1001-9332.202202.022
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    Negative air ion (NAI) is an essential indicator for measuring air cleanliness of a given area, with vital role in regulating psychological and physiological functions of human body. The photoelectric effect is an important source and influencing factor for the generation of NAI during photosynthesis, but the photoelectric effect is extremely weak and difficult to monitor. Plant electrical signal is an important indicator that indirectly reflects photoelectric effect. Previous studies mostly focused on the spatiotemporal variation of NAI in different forest communities and its relationship with meteorological factors. At present, there is little research on NAI and plant electrical signal. In this study, we explored the effect of different light intensities (0, 150, 300, 500, 700, 800, 1000 and 1200 μmol·m-2·s-1) on characteristics of the plant electrical signal and its relationship with negative air ion, with Pinus bungeana as the research object. The results showed that the intensity of plant electrical signal increased significantly with the increases of light intensity in the illumination range of 0-700 μmol·m-2·s-1. When light intensity reached 700 μmol·m-2·s-1, plant electrical signal activity reached the highest level, and plant was inhibited by light when light intensity increased further, with plant electrical signal activity decreased. The frequency-domain parameters (edge frequency, gravity frequency, power spectrum entropy and power spectrum peak) of plant electrical signals were significantly correlated with NAI. The correlation coefficient between edge frequency (E) and NAI was the highest, the relationship between them was NAI=30.981E+168.814 (R2=0.54), and the mean square error was 52.203. There was a significant correlation between plant electrical signals and NAI, which could characterize the change rule of NAI, and provide scientific evidence for further understanding the contribution potential and production mechanism of forest to NAI.
    Using geographical detection to analyze responses of vegetation growth to climate change in the Loess Pla-teau, China
    HE Peng, BI Ru-tian, XU Li-shuai, WANG Jing-shu, CAO Chen-bin
    2022, 33(2):  448-456.  doi:10.13287/j.1001-9332.202202.012
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    In order to explore the responses of different vegetation types to climatic change in the Chinese Loess Plateau (CLP), we analzyed the changes of different vegetation types and their relationships with meteorological factors using trend analysis, Hurst index, and geographical detector model based on normalized difference vegetation index (NDVI). The results showed that NDVI of different vegetation types from 2002 to 2019 was dominated by a growing trend and codirectional moderate persistence. The NDVI of crops in the built-up and adjacent areas decreased significantly. Except for grassland or meadow that was affected by mixed pixels, the spatial variation of NDVI was significant in the growing season (from April to October). The mean NDVI of different vegetation types followed an oder: coniferous forest > broadleaved forest > scrub > meadow > grassland > crop > steppe > desert. The interactions between meteorological factors were synergistic and non-linear enhancement in the CLP. Moreover, the interaction was more prominent under steppe and desert where habitat was fragile. The synergistic effect of precipitation and temperature had a great influence on all vegetation types. Water vapor, relative humidity, sunshine duration, atmospheric pressure, and wind speed had different explanatory powers on NDVI through indirectly affec-ting hydrothermal conditions.
    Responses of solar-induced chlorophyll fluorescence to meteorological drought across the Loess Plateau, China.
    CAO Yin-xuan, HUANG Zhuo, XU Xi-juan, CHEN Shang, WANG Zhao, FENG Hao, YU Qiang, HE Jian-qiang
    2022, 33(2):  457-466.  doi:10.13287/j.1001-9332.202202.011
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    With the intensification of climate change, the frequency, duration and scope of drought have become more and more serious. Exploring the responses of plant photosynthesis to drought and the impacts of meteorological factors on photosynthesis is of great significance to the dealing with drought stress. Solar-induced chlorophyll fluorescence (SIF) based on remote sensing has the potential for early monitoring and accurate assessment of regional vege-tation photosynthesis under drought conditions. Based on the spaceborne SIF information and the standardized precipitation evapotranspiration index (SPEI), we investigated the responses of vegetation photosynthesis to drought and the influence of meteorological factors in the growing season (April to October) of the Loess Plateau during 2001-2017. The results showed that about 87.8% of total areas of the Loess Plateau had a significant positive correlation between SIF and SPEI. Vegetation photosynthesis in semi-arid area was more sensitive to drought and less sensitive in semi-humid area. Different vegetation types had different photosynthetic responses to drought. Grassland had the highest sensitivity to drought with three to four months SPEI time-scale, while forest had the lowest sensiti-vity with three to ten months SPEI time-scale. There was a significant correlation between meteorological factors and SIF. Temperature and precipitation were the most important factors affecting vegetation photosynthesis on the Loess Plateau. Photosynthetically active radiation showed a similar controlling strength to temperature. The impacts of drought and meteorological factors on vegetation photosynthesis were largely determined by differences in drought resistance among ecosystem types and climate regions.
    Predicting soil property in hilly regions by using landscape and multiscale micro-landform features
    WEI Yu-chen, ZHAO Mei-fang, ZHU Chang-da, ZHANG Xiu-xiu, PAN Jian-jun
    2022, 33(2):  467-476.  doi:10.13287/j.1001-9332.202202.013
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    To assess the high-resolution digital soil mapping method for small watersheds in hilly areas, we explored the role of landscape classification and multiscale micro-landform features in predicting soil pH, soil clay content (SCC), and cation exchange capacity (CEC). Geomorphons (GM) terrain classification method was used to create landform units. The traditional digital elevation model (DEM) derivatives and remote sensing variables were employed for different combinations with landscape and micro-landform classification variables, with further compa-rison and analysis being conducted. In addition, three machine learning techniques, including support vector machine (SVM), partial least squares regression (PLSR), and random forest (RF), were used to build prediction models. The best method was then selected, and then combined with regression kriging by modeling spatial structure of the model residuals. The results showed that the application of landscape and multiscale micro-landform classification variables effectively improved the prediction accuracy of pH, SCC, and CEC by 18.8%, 8.2% and 8.7%, respectively. The map of landscape classification that contained vegetation coverage information had greater model contribution than land use data. The GM classification map with 5 m resolution was more suitable for high-precision DSM than those with lower resolution. The composite model of RF performed the best in predicting SCC, while the pH and CEC were not suitable for adding the residual regression kriging on the basis of RF model. Finally, the combination of landscape and multiscale micro-landform classification variables, DEM derivatives and remote sensing variables had the highest prediction accuracy for all the three soil properties. This result indicated that multivariable contained more effective soil information than single data source for rolling areas. The landscape variables composed of GM and surface classified data explained about 40% of the spatial variation of tested soil attributes in hilly area. Therefore, multi-resolution GM and landscape classified variables could be included into the construction of prediction model in research of soil mapping.
    Relationship between alien plant invasion and landscape matrix in the water-level fluctuating zone of the Three Gorges Reservoir, China.
    HUANG Jin-xia, YI Xue-mei, JIA Wei-tao, LIU Ying, ZHANG Song-lin, LI Xiao-hong, WU Sheng-jun, MA Mao-hua
    2022, 33(2):  477-488.  doi:10.13287/j.1001-9332.202201.011
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    Invasive process of alien species is affected by not only the invaded habitats, but also the surrounding landscape matrix. Understanding the effects of landscape matrix on alien species is of great significance for controlling invasive alien species. We surveyed plant communities along the water-level fluctuating zone (WLFZ) of the Three Gorges Reservoir. Invasive status of alien plant species was evaluated. Totally 10 spatial scales of the surrounding landscape matrix in the scope of 2000 m (including WLFZ) were classified, and 14 landscape indices were applied to analyze the landscape matrix composition and configuration. Using the principal component analysis and correlation analysis, the effects of landscape matrix on the alien invasive plant species and associated scale effect were tested. Results showed that a total of 42 alien invasive plant species were found in the WLFZ, belonging to 17 families and 36 genera. Fuling was a dividing place to differentiate invasive species distribution. The number of the alien invasive species between Fuling and the Three Gorges Dam was found more than that between Fuling and Jiangjin. For the all scales (within 2000 m). The higher the landscape matrix fragmentation was, the more difficult the alien species invading. The higher landscape connectivity was, the easier the alien species invading. The effects of landscape matrix composition and configuration on the invasive plant diversity at large scales (1200-2000 m) was more significant than those at small scales (200-1000 m), in which landscape matrix composition and configuration at 1200-1400 m showed the strongest effect, demonstrating a significant spatial scale effect. Different invasive plant species showed the scale effects of landscape matrix composition and configuration. At all scales, Xanthium strumarium and Bidens frondosa showed weak correlations with landscape indices, but Bidens tripartita and Erigeron canadensis showed strong correlations. Landscape matrix was closely related to invasive plant species, and demonstrated a significant scale effect. The alien invasive plant species could be traced to the landscape matrix at large scales. Grassland and forest patches at the small scales could be used as the ‘stepping stone' for the alien species transiting before they arrived at the WLFZ. In order to control alien plants in the WLFZ, land-use management and optimization should be strengthened at different scales of landscape matrix on the basis of enhancement of habitat management. A diversified comprehensive control for alien species should thus be taken into account.
    Cross-scale spatiotemporal characteristics of landscape ecological conditions index in coastal zone of Jiangsu Province, China during 1990-2020.
    YUAN Bing-yu, GAO Jian-hua, CHI Yuan, ZHA Bian, GONG Zhao-hui
    2022, 33(2):  489-499.  doi:10.13287/j.1001-9332.202202.016
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    Coastal zone ecosystems in Jiangsu have produced different degrees of spatial response and degradation characteristics under complex external disturbances, especially significant spatiotemporal evolution of landscape pattern in recent decades. It is urgent to carry out comprehensive assessment on landscape ecology covering landscape composition, configuration, and function at multiple scales. We analyzed the spatial and temporal variations of landscape ecological condition index (LECI) in large-scale coastal zone of Jiangsu Province from 1990 to 2020, assessed landscape ecological conditions of 14 county-level districts, and selected evaluation units with side lengths of 100, 200,…, 1000 m to understand the spatial scale effects of LECI. The results showed that the indicators of landscape composition, configuration and function could sensitively reflect the changes of LECI, which could comprehensively evaluate landscape ecological condition of Jiangsu coastal zone during the study period, with 300 m evaluation unit being the best spatial scale. The LECI value in the study area fluctuated. Landscape ecological condition was the best in 1990 and the worst in 2020. Landscape composition and configuration had a greater impacts on the changes of landscape ecological condition. The fluctuation of LECI in different counties and cities was closely related to intense human activities. Human activities, such as industrial development and urban expansion, had damaged landscape ecological status. The establishment of nature reserves had restored landscape ecological status to a certain extent. LECI could effectively indicate the changes of landscape ecological status of large-scale coastal zone, and provide multi-perspective suggestions for space utilization and protection.
    Characteristics and optimization strategies of territorial space zone in Fujian Province, China based on carbon neutrality.
    XU Ying, GUO Nan, RU Kai-li, FAN Sheng-long
    2022, 33(2):  500-508.  doi:10.13287/j.1001-9332.202201.016
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    Under the background of urban low-carbon transformation, a study on regionalization can provide a refe-rence for achieving optimization of territorial protection and high-quality development. We examined carbon emission and spatial differentiation characteristics of land use in 79 counties of Fujian Province. From the perspective of carbon neutral, reasonable division of region of Fujian Province was gotten after a comprehensive evaluation combined with economy contributive coefficient of carbon emission, ecological support coefficient of carbon absorption and priority function zoning. Then, we proposed the low-carbon optimization strategy for differentiated land space. The results showed that the total carbon emission in Fujian Province was 62.0416 million t and the total carbon absorption was 49.0971 million t in 2017, indicating that Fujian was at a state of carbon deficit. The spatial distribution of carbon emission and carbon absorption was opposite from coastal to inland. The six territorial space zones were low-carbon development-ecological function zone, low-carbon development-main producing area of agricultural products zone, low-carbon development-urban optimization zone, carbon sink function-main producing area of agricultural products zone, carbon intensity control-urban optimization zone, and high-carbon optimization-urban optimization zone. We proposed the corresponding low-carbon optimization strategies of territorial space for each zone.
    Spatial-temporal differentiation and influencing mechanism of green development efficiency in three major urban agglomerations in Zhejiang Province, China.
    WENG Yi-jing, WANG Xia-tong, CHEN Si-jing
    2022, 33(2):  509-516.  doi:10.13287/j.1001-9332.202202.014
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    Improving the green development efficiency of the three major urban agglomerations in Zhejiang is an important way to faster build the pilot demonstration area of beautiful China. Based on county panel data from 2000 to 2019 of 41 counties (cities) included in the three major urban agglomerations, we combined the super-efficiency SBM model with window analysis to evaluate the efficiency, and used spatial econometric analysis method to study the spatial distribution and the differences in regional difference. Furthermore, the fixed panel fixed effect model was used to explore the differential influencing mechanism. The results showed that green development efficiency of the three major urban agglomerations increased gradually with fluctuations during the study period. The distribution of efficiency values gradually shifted from a situation of ‘high in the north and low in the south' to a ‘relatively common and coordinated' development in the various regions. There was a significant spatial agglomeration effect in green development efficiency of the three major urban agglomerations, but it presented fluctuating phenomenon among cities which were at the similar level. The average green development efficiency of central Zhejiang urban agglomeration was the highest. The development within the three major urban agglomerations was relatively stable. The annulus Hangzhou Bay urban agglomeration came next, with stable development. The Wenzhou-Taizhou coastal urban agglomeration was the lowest, but the efficiency enhancement was the largest. The increases in population density, along with the proportion of added value of tertiary industry in GDP, per capita industrial added value, local fiscal expenditures, education expenditures and per capita actual use of foreign capital could improve the efficiency of green development. However, the increases in industrial electricity consumption and fixed asset investment in kennels would inhibit the improvement of green development efficiency. The impacts of per capita industrial added value, local fiscal expenditure, education expenditure and per capita actual use of foreign capital on urban agglomerations were heterogeneous among different cities.
    Effects of electron acceptor and light on the abundance of microbial function gene related to soil CH4 emission
    CHEN Juan, HU Lin-yu, LU Peng-wei, JIANG Yu-mei, ZHANG Zhi-bin, ZENG Qing-gui, JIAN Min-fei, ZHU Du
    2022, 33(2):  517-526.  doi:10.13287/j.1001-9332.202202.033
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    To explore the effects of different electron acceptors on soil methane emission and responses of soil microorganisms to different light conditions, a strict anaerobic 20-day incubation experiment was conducted with eight treatments: darkness + Fe3+ (DF); darkness + NO3- (DN); darkness +SO42- (DS); darkness + distilled water (DCK); light + Fe3+ (LF); light + NO3- (LN); light +SO42- (LS); light + distilled water (LCK). The changes of methane concentration in the anaerobic incubation flask and the variation of the abundance of bacteria, archaea, fungi and six soil functional genes were analyzed. Results showed that soil methane emission under NO3-, SO42- addition and control (CK) was significantly lower under light conditions than dark, except the Fe3+ treatment. DN, DCK and LF treatments had the highest abundance of bacteria, fungi and archaea genes, respectively. The gene abundance of methanogenic mcrA, sulfate-reducing bacteria Dsr, and carbon-fixing CbbL were significantly up-regulated in the LF, while that of methanotrophs pmoA, iron-reducing bacteria Geo, and denitrifying bacteria nosZ were significantly up-regulated in the LN, DCK and LCK, respectively. Results of Pearson correlation and RDA analysis showed that CH4 emission was significantly positively correlated with CO2 concentration, pH, ammonium-nitrogen, and total N contents, and negatively correlated with N2O concentration, Eh, nitrate, and total C contents. Under dark condition, methane emission was positively correlated with archaea and pmoA genes abundance, and negatively correlated with other genes abundance. Under light condition, methane emission was negatively correlated with the abundance of soil microbe and functional genes. In general, methane emission under light condition was significantly lower than that under dark condition (except for the Fe3+ treatment). These results showed that it was helpful to reduce methane emission under light condition, but the increase or decrease of methane emission was closely related to the type of electron acceptors and the functional responses of soil micro-organisms
    Effects of landscape complexity and local management on bee pollinator diversity in apple orchards in Changping District, Beijing, China.
    WANG Mei-na, WANG Zi-rui, YU Zhen-rong, XU Huan-li, LIU Yun-hui
    2022, 33(2):  527-536.  doi:10.13287/j.1001-9332.202201.035
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    Pollinators provide important ecosystem services for crop production and food security. With the development of agricultural economy and the increasing intensity of land-use, a large number of natural or semi-natural habitats have been converted to croplands. Landscape homogenization and intensive management lead to the decline of wild bee diversity and threaten the sustainable agricultural production. In this study, we investigated the effects of landscape complexity (proportion of semi-natural habitats), local management practices (local flowering plant diversity and soil total nitrogen), and their interactions on diversity of bee pollinators in apple orchard in Changping District, Beijing. A total of 8642 bee individuals were captured, including 5125 honey bees and 3517 wild bees from 5 families, 14 genera, and 49 species. The optimal landscape scale for the response of bee diversity to landscape complexity and local management intensity was 500 m. Within 500 m radius of the site, the abundance of overall bees and wild bees significantly increased with increasing proportion of semi-natural habitats. The landscape complexity interacting with local flowering plant diversity significantly affected the richness of overall bee and wild bee. When the proportion of semi-natural habitats surrounding the apple orchards was low (≤29.9%), we found a positive effect of flowering plant diversity on the richness of overall bee and wild bee, whereas a reversed trend was found when the proportion of semi-natural habitats surrounding the apple orchards was high (>29.9%). In addition, the abundance of honey bees significantly increased with the increase of local flowering plant diversity and soil total nitrogen. The soil total nitrogen interacting with local flowering plant diversity significantly affected the honey bee abundance. At low levels of soil total nitrogen (≤1.9 g·kg-1), there was a positive effect of flowering plant diversity on honey bee abundance; whereas this trend was reversed at high levels of soil total nitrogen (>1.9 g·kg-1). Increasing the proportion of semi-natural habitats in agricultural landscape was beneficial to the increase of wild bee abundance, and flowering plant diversity could promote bee diversity but depending on landscape scale (proportion of semi-natural habitats) and local scale (nitrogen application). Therefore, multi-scale factors should be considered to develop conservation strategies to maintain the diversity of wild bees in agricultural landscape. Maintaining a higher proportion of cultivated land as much as possible is still a long-term requirement for production, while maintaining intermediate landscape complexity, increasing the diversity of flowering plants on the ground, and reducing the application of nitrogen fertilizer would be effective ways to promote the diversity of pollinating bees in apple orchards.
    Wildfire smoke injection heights in China based on multi-angle imaging spectroradiometer (MISR) observations
    WANG Wen-jia, ZHANG Qi-xing, ZHANG Yong-ming
    2022, 33(2):  537-543.  doi:10.13287/j.1001-9332.202202.017
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    Smoke injection height is a key driving factor for plume transport, which determines the lifetime of smoke aerosol in the atmosphere, transport path and diffusion along with the wind, and impacts on atmospheric environment. In this study, raw data obtained from the latest multi-angle imaging spectroradiometer (MISR) plume height project was extracted and analzyed. The variation of smoke injection heights of wildfire in China was investigated with statistical analysis methods. The effects of fire characteristics (combustion biomass type and fire radiative power) on the smoke injection height were explored. Meanwhile, the influence of smoke injection heights on the atmospheric environment was discussed based on the proportion of higher injection height plumes and the value of smoke aerosol optical depth (AOD). The results showed that smoke injection heights from wildfire ranged from 345 to 7719 m, with 57.1% of which ranging from 500 to 1000 m. Except for an abnormally high value of smoke injection height from a large grassland fire, the rest of smoke injection heights were lower than 3000 m. The biomass type for combustion was an important factor affecting smoke injection heights. The injection heights of the plume caused by forest fire were the highest and had the greatest variability. Smoke injection heights increased with the fire radiation power, but with obvious dispersion (R2=0.19). By setting a simple threshold, the proportion of higher injection plumes which might cause long-distance transportation of air pollutants in China was 10.5%. Combined with the analysis of smoke AOD, it was found that the average smoke injection height from cropland burning was the lowest, but their smoke caused the highest regional air pollution. In contrast, although forest fires could produce the highest smoke injection height, their smoke had a lower average value of AOD, which indicated a relatively weak impact of forest fires on regional air quality.
    Composition and distribution of zooplankton species in the subtropical areas of the Northwestern Pacific Ocean
    FU Fei-yu, BU Xin-yu, SHEN Ang-lyu, LIU Bi-lin
    2022, 33(2):  544-550.  doi:10.13287/j.1001-9332.202201.031
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    Based on the investigation data of 44 stations in the area 28°－35° N, 147°－154° E of the Northwestern Pacific Ocean by the research ship ‘Songhang' in March 2019, we analyzed species composition and distribution of zooplankton to understand zooplankton community structure in the subtropical areas of the Northwestern Pacific Ocean. The results showed that a total of 456 zooplankton species (including planktonic larvae and unidentified species) were recorded in the surveyed area, which were belonged to 8 categories and 14 groups. There were 163 species of copepods, as the dominant group. The dominant species included 9 warm-water species, Eudoxoides spiralis, Neocalanus gracilis, Pleuromamma gracilis, Sagitta enflata, Doliolum nationalis, S. hexaptera, Euchirella rostrata, Nannocalanus minor and Mesocalanus tenuicornis, and one temperate species, Calanus jashnovi. Both the warm current indicator species S. hexaptera and the cold current indicator species C. jashnovi occurred simultaneously in the subtropical area, indicating that the Kuroshio Current and the Oyashio Current had an important impact on the diversity and temporal-spatial distribution of marine zooplankton. The average biomass was (31.64±23.81) mg·m-3, and the average abundance was (22.2±17.6) ind·m-3. The average values of purity index (C), eveness index (J), Shannon diversity index (H) and richness index (D) were 0.09±0.10, 0.76±0.10, 4.88±0.71, and 23.53±8.08, respectively. The spatial distribution of the four indices were uneven and irregular. During the study period, species composition of zooplankton in the Northwest Pacific was rich, species distribution was uneven, and community structure was stable.
    Effects of hypoxia and acidification stress on ion regulation and gill structure of juvenile Larimichthys crocea.
    ZENG Jiao, WANG Qian, WANG Ya-bing, PENG Shi-ming, CHEN Run, MA Ling-bo, WANG Cui-hua
    2022, 33(2):  551-559.  doi:10.13287/j.1001-9332.202202.032
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    To investigate the ion regulation of large yellow croaker (Larimichthys crocea) under hypoxia and acidification stresses, we investigated the effects of hypoxia (dissolved oxygen DO 3.5 mg·L-1, pH 8.1), acidification (DO 7.0 mg·L-1, pH 7.35) and combined stresses of hypoxia and acidification (DO 3.5 mg·L-1, pH 7.35) on gill tissue structure and physiological indices related to ion regulation of juvenile L. croaker. The results showed that, under hypoxia stress, gill Na+/K+-ATPase activity, serum Na+, Ca2+ and Cl- contents of juvenile L. croaker decreased first and then increased. Under acidification stress, gill Ca2+-ATPase activity, serum Na+ and Ca2+ contents of juvenile L. croaker increased first and then decreased. Under the combined stresses of hypoxia and acidification, Na+/K+-ATPase activity and Na+, K+ and Ca2+ contents increased first and then decreased, while Ca2+-ATPase activity and Cl- content decreased first and then increased. The results of gill histology showed that hypoxia and acidification stresses led to the detachment of gill epithelial cells, and the combined stresses of hypoxia and acidification led to proliferation, hypertrophy and swelling of gill epithelial cells. Comprehensive analysis showed that hypoxia and acidification stress affected the activities of major ion regulatory enzymes in juvenile L. croaker and caused different degrees of damage to gill tissue, resulting in imbalanced ion regulation in juvenile L. croaker.
    Sulfur oxidation-reduction process and its coupling effects with other elements in marsh soil: A review
    MAO Li, SUN Zhi-gao, CHEN Bing-bing, HU Xing-yun, WU Hui-hui
    2022, 33(2):  560-568.  doi:10.13287/j.1001-9332.202202.031
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    Sulfur oxidation-reduction process (SORP) in marsh soil is an important link in sulfur cycle, which plays an important role in maintaining the stability and health of marsh. We summarized the SORP in marsh soil and its influencing factors, and analyzed the research progress of its coupling effects with other elements. The influencing factors of SORP in marsh soil mainly involved biotic (plants, microorganisms, zoobenthos, human activities, etc.) and abiotic factors (physical factors such as temperature, moisture and particle size, and chemical factors such as pH, salinity, organic matter, etc.). Related research on the coupling effects of SORP and other elements in marsh soil mainly involved in biogenic elements such as carbon (C), nitrogen (N) and phosphorus (P), and metal elements such as iron (Fe) and manganese (Mn). Currently, the underlying mechanism of SORP was not deeply explored, the research on coupling effects was unbalance, and the ecological effects were insufficient. In the future, key functional microorganisms involved in SORP should be strengthened, the coupling mechanism between SORP and micro-elements should be enhanced, and the ecological effects produced by the coupling effects of SORP with other elements should be emphasized.
    Research advances on the effects of grazing on plant functional traits in grassland
    WANG Xiao-fang, MA Hong-bin, LIU Jie, MIAO Hai-tao, SHEN Yan, ZHOU Yao, MA Jing-li
    2022, 33(2):  569-576.  doi:10.13287/j.1001-9332.202202.023
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    Plant functional traits is connected with vegetation adaptability to the environment. The trade-off between plant functional traits reflects resource reintegration and acquisition under grazing pressures. We summarized the differences of plant functional traits under grazing disturbance, focused on the linkages between grazing disturbance and plant functional traits. We introduced that the variation of plant functional traits resulted from the coordination between plant genetic characteristics and environmental filtration, summarized the effects of grazing on nutritional and reproductive traits, and noted that plants could use survival and reproductive strategies to adapt to the grazing disturbance. We mainly focused on the effects of grazing on plant population, community and ecosystem. The expression of plant functional traits was different under grazing disturbance. Therefore, plant functional traits could be used as indicators to explain population growth and reproduction, community assembly, and ecosystem function. In order to better serve the ecological environment of grassland with plant functional traits, reasonable grazing resis-tant species could be screened according to plant functional traits. Based on life history characteristics of grassland plant population, the scientific grazing mechanism should be formulated, and the responses of plant functional traits and resource allocation to grazing disturbance should be conducted from the perspective of individual-based level in the future.