Table of Content

10 May 2022, Volume 41 Issue 5

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Morphology and nutrient contents of fine roots from different orders in Fagaceae species in an evergreen broad-leaved forest.

LI Shi-yi-ning, XIONG De-cheng, YAO Xiao-dong, WANG Xiao-hong, CHEN Ting-ting, JIANG Qi, JIA Lin-qiao, FAN Ai-lian, CHEN Guang-shui

2022, 41(5):  833-840.  doi:10.13292/j.1000-4890.202205.010

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We examined the interspcific and root order related variations in fine root morphology and stoichiometric traits of 8 Fagaceae species in an evergreen broadleaved forest in Wanmulin Nature Reserve of Fujian Province. The results showed that fine root diameter, tissue density (RTD) and C/N increased significantly, and specific root length (SRL) and N concentration decreased significantly, but C concentration showed no clear trend with increasing root orders. The main driver for interspecific variation in SRL depended on root orders: the interspecific variations of SRL for the first two orders were mainly caused by root diameter, while those for the higher root orders were caused by RTD. Moreover, the interspecific variations of root traits for the Fagaceae did not conform to a single axis, i.e., the “root economic spectrum”, but had two variation dimensions similar to those found on the global scale, that is, “do-it-yourself vs. mycorrhizal dependence” and “resource acquisition vs. conservation”. There were obvious differences in the ecological strategies of fine roots among different Fagaceae species.

Responses of leaf functional traits and carbon and nitrogen allocation in hybrid poplar (Populus ×euramericana ‘Zhongjin2’) seedlings under twoyear nitrogen addition.

GAO Tian-hui, WANG Wei-feng, SHANG Jia-zhou, LI Tao, WANG Sheng-ji

2022, 41(5):  841-848.  doi:10.13292/j.1000-4890.202204.011

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Atmospheric nitrogen deposition affects forest ecosystems. The ecophysiological process and mechanism of trees in response to nitrogen deposition need further clarification. To explore the changes of photosynthetic traits, biomass accumulation, and carbon and nitrogen allocation in poplar under nitrogen addition, hybrid poplar (Populus ×euramericana ‘Zhongjin2’) seedlings were grown in pots under a rainout shelter in a semiarid area of China. Seedlings were treated with different nitrogen addition levels (0, 3, 6 and 9 g NH₄NO₃·a^-1·plant^-1) for two years. Leaf photosynthetic rate, leaf  functional traits, organ biomass, and carbon and nitrogen allocation were investigated. In the first year, with the increases of nitrogen addition levels, leaf area significantly increased but leaf became thinner, with decreased mesophyll tissue thickness. Leaf area based net photosynthetic rate and stomatal conductance increased firstly and then decreased with increasing nitrogen addition level, while transpiration rate, instantaneous water use efficiency and photosynthetic nitrogen use efficiency did not change. Whole plant biomass and carbon and nitrogen accumulation significantly increased. The carbon investment in stem increased significantly while that in root decreased significantly. In the second year, photosynthetic carbon fixation rate of functional leaves reached saturation more quickly with increasing nitrogen addition level, with toxicity of high-dose addition. The biomass accumulation of individual plant increased significantly and carbon investment to stem was increased in low nitrogen addition, while root growth was inhibited in high nitrogen addition. The enhanced leaf water consumption in response to nitrogen addition may be one of the driving factors of carbon investment to stem, while the decreasing root shoot ratio may reduce the resistance of poplar seedlings to frequent drought in semiarid area.

Effects of stumping height on carbon, nitrogen, and phosphorus stoichiometry in different organs of Pinus yunnanensis seedlings.

CAI Nian-hui, TANG Jun-rong, CHE Feng-xian, CHEN Shi, WANG Jun-min, XU Yu-lan, LI Gen-qian

2022, 41(5):  849-857.  doi:10.13292/j.1000-4890.202203.012

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To understand the effects of stumping on the contents and stoichiometry of carbon (C), nitrogen (N), and phosphorus (P) in different organs of Pinus yunnanensis seedlings, and the correlations and allometric relationships among C, N and P, the contents of C, N, P and the ratios of C∶N, C∶P and N∶P in seven organs (taproot, lateral root, stem, lateral branch, mother plant needle, sprout branch, sprout needle) of P. yunnanensis seedlings with different stumping heights (CK, 5, 10 and 15 cm) were analyzed. The results showed that N, P, C∶N, C∶P, N∶P had significant differences among stumping heights, organs, stumping heights×organs, except that C content showed no response to stumping height. With the increases of stumping height, N, P, C∶N, C∶P, N∶P showed a trend of first increase and then decrease, while C∶N and C∶P showed an opposite trend. The variation coefficients of contents and ratios of elements in each organ fluctuated slightly under different stumping heights, indicating that stumping had little effect on C, N, P contents and their stoichiometric stability. The correlations between C and N and between C and P changed among different stumping heights, while the correlations between C and N and between C and P were weakened with increasing stumping height. Stumping did not affect the allometric growth relationship between them, with the accumulation rate of C being lower than that of N and P, and the growth of seedlings being mainly regulated by N. In summary, stumping changed nutrient content, and then changed the balance of C, N and P in plants. The performance of P. yunnanensis seedlings was mainly regulated by N. With increasing stumping height, the utilization of N and P in seedlings decreased first and then increased, at the same time the degree of N limitation decreased first and then increased.

Effects of nitrogen addition on biomass and root morphology of Phyllostachys edulis seedlings under drought stress.

GAO Ge, LI Zheng-cai, GE Xiao-gai, HUANG Run-xia, LI Ai-bo

2022, 41(5):  858-864.  doi:10.13292/j.1000-4890.202203.017

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We investigated the responses of aboveground biomass and root morphological characteristics of Phyllostachys edulis seedlings to nitrogen addition under different levels of drought stress. The experiment followed a two factor completely random block design, with three levels of soil water condition (CK, MD, and HD with 80%-85%, 50%-55%, and 30%-35% of field water holding capacity, respectively) and two levels of nitrogen addition (N0, 0 mg N·kg^-1; N1, 100 mg N·kg^-1). The root morphological characteristics and biomass of seedlings were measured. The results showed that nitrogen addition increased the biomass of leaf and root inPh. edulis seedlings under the same water level. Compared with N0MD and N0HD, the aboveground biomass of N1MD and N1HD increased by 15.6% and 11.9%, while the total biomass increased by 36.7% and 25.0%, respectively (P<0.05). Nitrogen addition reduced the specific root length and stem/leaf ratio of Ph. edulis seedlings under the same water level, but significantly promoted root/shoot ratio under moderate and high drought stresses (P<0.05). Under water stress, the proportion of root biomass increased significantly, while the proportion of stem and leaf biomass showed a decreasing trend with nitrogen addition. Nitrogen addition improved root morphological characteristics (root length, root surface area, root volume) of Ph. edulis. Nitrogen addition showed stronger enhancement on dry matter accumulation of Ph. edulis seedlings under moderate drought than under high drought stress, while better alleviated the stress of high drought on root morphology. In conclusion, nitrogen application prompted Ph. edulis to adjust its biomass allocation under drought stress to optimize the access to limited resources. It also facilitates to shape root morphological characteristics through alleviating the inhibitory effect of drought on the growth of Ph. edulis seedlings.

Effects of elevated CO₂ concentration on photosynthetic characteristics of Schima superba seedlings.

PAN Hong, CAO Ji-xin, CHEN Zhan, SHANG He

2022, 41(5):  865-872.  doi:10.13292/j.1000-4890.202203.036

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Few studies have explored plant responses to all of CO₂ scenarios including 430-480, 580-720, 720-1000 and more than 1000 μmol·mol^-1 which will be by 2100 predicted by the IPCC (Intergovernmental Panel on Climate Change). In this study, one-year-old seedlings of Schima superba were exposed to ambient air and three elevated CO₂ concentrations of 550, 750, 1000 μmol·mol^-1 to investigate the changes of gas exchange parameters, photosynthetic pigment contents, and biomass by using Open Top Chambers during growing season. The results showed that net photosynthetic rate was increased by 32.7%, 66.7%, and 82.7%, and intercellular CO₂ concentration was increased by 60.3%, 126.2%, 223.9% at 550, 750, and 1000 μmol·mol^-1, respectively. The improvement in net photosynthetic rate under elevated CO₂ concentrations decreased as affected by non-stomatal factors (such as decreased leaf N content) after longer fumigation time. Stomatal conductance and transpiration rate increased under all elevated CO₂ concentrations from May to July, while there was no significant difference between 1000 μmol·mol^-1 and ambient treatments from August to October. The reduction of the contents of chlorophyll a, chlorophyll b, carotenoids, and N in leaves under 750 and 1000 μmol·mol^-1 was higher than that under 550 μmol·mol^-1. Biomass under the treatments of 550 and 750 μmol·mol^-1 increased by 79.2% and 48.9%, respectively, but decreased under 1000 μmol·mol^-1. Therefore, it would be beneficial for S. superbato fix the increasing CO₂ in atmosphere and preserve water in body under elevated CO₂ concentrations. These benefits would increase the adaptability of S. superba seedlings to arid environments and enhance biomass accumulation under CO₂ concentrations of 550 and 750 μmol·mol^-1.

Drought resistance of major wheat varieties in Shanxi Province at germination and seedling stages.  

WEI Liang-di, LI Ning, YANG Jin-wen, SHI Yu-gang, SUN Dai-zhen, WANG Shu-guang

2022, 41(5):  873-879.  doi:10.13292/j.1000-4890.202205.020

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Water plays an important role in the growth and development of wheat. Shanxi Province is seriously limited by water resources. Therefore, it is imperative to identify the drought resistance of main wheat varieties in Shanxi Province for breeding excellent drought-resistant varieties. In this study, simulated drought (20% PEG-6000) stress was induced at germination and seedling stages of 40 wheat varieties in Shanxi Province. The effects of drought stress on the morphological characteristics of germination and seedling stages were analyzed. The drought resistance of wheat varieties was evaluated by using membership function and comprehensive drought resistance evaluation value. The results showed that various characteristics of wheat germination and seedling stages were affected by drought stress in various degrees. Bud length, root length, bud fresh weight, root fresh weight at the germination stage, and leaf fresh weight and root fresh weight at the seedling stage were significantly affected by drought stress. A total of 21 drought-resistant varieties (52.5%) were screened out at the germination stage, with Shannong 17 having the highest comprehensive evaluation value (0.783). A total of five drought-resistant varieties (12.5%) were selected at the seedling stage, namely Shannong 24, Jinmai 66, Changmai 6135, Jinmai 62, and Changmai 3897. Changmai 3897 was a drought-resistant variety at both the germination and seedling stages. The relationship between the comprehensive evaluation value of drought resistance at the germination and seedling stages were further fitted, showing no significant correlation between the drought resistance of the tested varieties at both stages. Our results can provide a reference for the selection of dryland wheat production varieties and the improvement of drought resistance in Shanxi Province.

Effects of sowing date on growth, dry matter accumulation and yield of sorghum under direct seeding ridge cultivation in Southwest China.

YIN Xue-wei, Li Qiang, WANG Qiu-yue, LU Yuan-yuan, LI Qing-hu, WEI Ling, ZHANG Xiao-chun

2022, 41(5):  880-886.  doi:10.13292/j.1000-4890.202204.031

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There are problems in direct-seeding sorghum in Southwest China, including variable sowing date, unstable seedling situation, low yield, and low efficiency. A new sorghum variety ‘Chuannuoliang No. 1’ was used as the test material to study the variations of growth process, dry matter accumulation, yield and its composition of sorghum under different sowing dates through field trials from 2015 to 2016. The results showed that, with the delay of sowing date, the growth period of sorghum gradually shortened, while dry matter accumulation, yield and its composition (number of kernels per ear, 1000-kernel weight, and kernel weight per ear) of sorghum increased first and then decreased. The dry matter accumulation, yield and its composition under sowing date D3 (April 20) were higher than that under other sowing dates. The growth duration was significantly negatively correlated with average daily temperature, while the dry matter accumulation and yield were significantly positively correlated with the accumulated temperature. Temperature was the key meteorological factor driving the yield differences of sorghumamongsowing dates. Temperature affected the growth process and dry matter accumulation, then regulated the kernel number per ear and kernel weight per ear, and ultimately affected grain yield of sorghum. April 20 is the suitable sowing date for ‘Chuannuoliang No. 1’ in Southwest China.

The soil needle microbe ecological stoichiometry and homeostasis in Pinus sylvestris var.mongolica plantations with different stand ages.

CHENG Hao-tian, KONG Tao, LYU Gang, WANG Dong-li, HUANG Li-hua, ZHANG Kai, WANG Yi-xiang

2022, 41(5):  887-894.  doi:10.13292/j.1000-4890.202205.019

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The aim of this study was to clarify the nutrient characteristics and stabilization mechanisms of Pinus sylvestris var. mongolica plantation. With Pinus sylvestris var.mongolicaplantations at sapling, young, mature and overmature stages in the Zhanggutai area of Northwestern Liaoning Province as the research objects, we examined the characteristics of C, N and P contents and ecological stoichiometry ratios in soil, needles, and  microbial biomass. We further analyzed the coupling relationship and homeostasis characteristics of those components. The results showed that C, N and P contents were poor in this area. Compared with the global mean value, needles were higher in C, P and lower in N. Compared with the  different stand ages, we found that soil C contents reached the peak value of 12.93 g·kg^-1 in overmature plantation; soil N and P contents peaked at 0.41, 0.25 g·kg^-1, needles C, N and P contents peaked at 641.38, 10.18, 1.81 g·kg^-1, microbial biomass C peaked at 165.68 mg·kg^-1, which all appeared in mature plantation. Microbial biomass N and P reached the peak value of 9.29, 2.92 mg·kg^-1 in young plantation. Soil C∶N of Pinus sylvestris var. mongolica plantation across different stand ages was much higher than the national average level of China, which showed N limitation. Only soil C∶P of overmature plantation was higher than the national average level of China, which showed P limitation. The soil, needles, and microbial biomass C∶N and C∶P of Pinus sylvestris var. mongolica of each stand age reached their peaks in overmature forests, and showed the strongest degree of N and P limitation. The stoichiometric characteristics of the three components (soil, needles, and microbes) had significant coupling relationships, and the relationship between microorganisms and soil was closer. In general, the homeostasis of nutrients and stoichiometric indicators in needles were much higher than that of microbes. It is recommended to apply N fertilizer reasonably in this area to improve the supply of soil nutrients, and to ensure the sustainability and stability of the ecosystem by introducing N fixing  plants. Meanwhile, more attention should be paid to the changes of soil microorganisms and timely supplement of organic fertilizer to improve soil quality during the management of Pinus sylvestris var. mongolica plantations.

Effects of Ligularia virgaurea on litter decomposition and nitrogen release in alpine meadow.

LIANG De-fei, JIANG Hong-yu, LI Hong-lin

2022, 41(5):  895-902.  doi:10.13292/j.1000-4890.202203.010

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Ligularia virgaurea, as “indicator species of alpine meadow degradation”, gradually expanded and became a dominant species in alpine meadow due to disturbances (e.g., overgrazing), and threatened ecosystem function and nutrient cycling. However, little is known about how litter decomposition and nitrogen release respond to dominance of L. virgaurea in alpine meadow. Litter decomposition is a key process linking carbon and nitrogen cycle and plays an important role in maintaining ecosystem function. In this study, a litter decomposition experiment with a mixture gradient of L. virgaurea and other species was conducted in a L. virgaurea dominated alpine meadow. The mass loss and nitrogen release of L. virgaurea and other species litter were measured and the effects of L. virgaurea litter on the decomposition of other species litter were determined. The results showed that: (1) Litter decomposition rate of L. virgaureawas lower than that of other species; (2) Total mass loss and nitrogen release of litter decreased with increasing proportion of L. virgaureain litter mixture; (3) Mass loss and nitrogen release of other species litter were inhibited by the presence of L. virgaurea. The antagonistic non-additive effect further decreased the decomposition of litter mixture. Our results suggested that increasing proportion of L. virgaureacould inhibit litter decomposition and nitrogen release, reduce nutrient input to soil, and thus disturb carbon and nitrogen cycling in degraded grasslands.

Simulation of soil water and salt transportation of typical plant community in estuarine wetland of the Yellow River Delta.

QU Zhi-cheng, LI Yun-zhao, YU Jun-bao, YANG Ji-song, MA Yuan-qing, ZHANG Jian-bai, ZHOU Di, WANG Xue-hong

2022, 41(5):  903-911.  doi:10.13292/j.1000-4890.202205.006

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To explore the effects of waterlogging and salt condition on soil water and salt transportation of estuary wetlands in the Yellow River Delta, we examined the infiltration process and water/salt redistribution process in the soils of three plant communities dominated by Tamarix chinensis, Phragmites australis and Suaeda salsa, respectively, by soil column experiments in laboratory. The Hydrus-1D model was used to simulate the distribution of water content and salt in soil profile after water infiltration and redistribution. The results showed that water depth significantlyaffected soil water transportation. Under different water depth conditions, the infiltration rates of three soil types showed a similar trend of rising first and then falling. The infiltration rates were decayed and tended to stabilize with the prolongation of infiltration time. At the end of the infiltration experiment, soil salt contents of 0-30 cm layer were similar to those of the infiltration water, while those of the water and salt transportation bottom (100 cm soil depth) were close to the salt contents in original experiment soils. After the water and salt redistribution experiment, the differences of soil water content of each soil layer were decreased, and salt contents of each layer basically unchanged compared with those at the end of the infiltration experiment. Our results indicated that Hydrus-1D model could well simulate the infiltration processes of soil water and salt, as well as the whole change trend of soil profile, providing a theoretical basis for the regulation of water and salt in estuarine wetlands and the restoration of wetland hydrological connectivity.

The transgenerational effect of arbuscular mycorrhizal fungi on root phosphatase activity of host plant Medicago truncatula.

ZHU Jia-ni, HUANG Hong, DU Yong, TANG Jian-jun, CHEN Xin

2022, 41(5):  912-918.  doi:10.13292/j.1000-4890.202205.004

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Arbuscular mycorrhizal fungi (AMF) can help host plants adapt to low P environment by enhancing the root secretion of acid phosphatase (APase). Whether such plastic change can be transmitted across generations, however, remains unclear. In this study, we conducted two experiments to investigate the transgenerational effect of AMF on APase activity in a host plant Medicago truncatula. Under low P condition in experiment 1, AMF infection increased APase activity in root, and increased APase activity and available P content in rhizosphere soil. Under high P condition, there was no difference of APase activity between AMF and non-AMF plants. Under low P condition in experiment 2, the offsprings from parental plants with AMF had higher APase activity compared to those from parental plants without AMF. No difference of APase activity was found between the offsprings from both nonAMF and AMF parental plants grown in high P condition. Under high P condition in experiment 2, however, there was no significant difference of the root APase activity among the offsprings of different parental plants. The results suggest that there was an AMF transgenerational effect on root APase activity, which was determined by soil P condition encountered by the parental plants.

The differences of soil nutrients and enzyme activities of different vegetation restoration models in opencast coal mine dump.

LI Han, LYUGang, LI Ye-xin, Cheng Hao-tian, Liu Yu-xin

2022, 41(5):  919-924.  doi:10.13292/j.1000-4890.202205.021

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To explore soil improvement under different restoration modes of open-pit mine dumps, we analyzed the characteristias of soil nutrient contents and enzyme activities under different vegetation restoration modes (Robinia pseudoacaciaforest, elm forest, mixed forest, shrubland, and abandoned grassland) in Haizhou openpit mine of Fuxin. The results showed that soil nutrient content in all vegetation restoration modes decreased with soil depth, with obvious surface aggregation. The activities of sucrase, catalase, and urease in all the five vegetation restoration modes peaked in the 0-10 cm soil layer, which was significantly different from the other soil layers. Soil protease activities peaked in the 0-30 cm soil layer. Soil nutrient contents were significantly correlated with soil enzyme activity. The results of principal component analysis showed that the principal component comprehensive scores of Robinia pseudoacacia forest, elm forest, mixed forest, shrubland and abandoned grassland were 2.94, 1.68, 4.44, -2.66, and -6.39, respectively. The overall performance of vegetation restoration effect was mixed forest > Robinia pseudoacacia forest > elm forest > shrubland > abandoned grassland. The shallow soil layer had the best restoration effect, with the effect gradually decreasing with soil depth. The mixed forest could be used as the main revegetation mode in this dump site.

Effect of ricecrayfish cultivation mode on the accumulation of soil reducing substances and nutrients.

XU Rong, YANG Ting, HAN Guang-ming, WU Lei-ming, ZHANG Jia-hong, KOU Xiang-ming, WANG Shou-hong

2022, 41(5):  925-932.  doi:10.13292/j.1000-4890.202205.014

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In this study, six model demonstration sites of rice-crayfish coculture (CR) and rice monocropping (MR, as control) in Yangzhou were selected to analyze the content of soil reducing substances, total nutrients and available nutrients across different planting years (1, 2, 3 years), soil layers (0-20, 20-40, 40-60 cm), and the growth period of rice (tillering stage, jointing booting stage, maturity stage), aiming to reveal the temporal and spatial variations of soil physicochemical properties of rice-crayfish coculture and to provide theoretical reference for field management and sustainable development of this model. The results showed that with the increases of planting years, CR increased the  active reducing substances, Mn²⁺ and Fe²⁺ contents  in 0-40 cm soil layer than MR, and such differences increased annually. The active reducing substances in 0-20 cm soil layer of CR was significantly higher than that of MR (P<0.05).The proportion of soil available phosphorus in 0-20 cm soil layer increased significantly under CR after operated for 2 to 3 years, compared with that for 1 year (P<0.05). There was no significant difference in ammonium nitrogen, available nitrogen, available nitrogen proportion, and available phosphorus over time among different treatments, but CR had a certain increasing trend compared with MR (P>0.05). In conclusion, CR could improve nitrogen and phosphorus availability in surface soil (0-20 cm) and thus soil fertility, but increase the risk of secondary gleyization in 0-40 cm soil layer compared with MR.

Comprehensive evaluation of soil nutrient characteristics and fertility of citrus orchard with different parent materials.

WANG Jue, ZHOU Wei-jun, SHANG Gui-duo, TAN Jie, TANG Dou, CAO Sheng

2022, 41(5):  933-940.  doi:10.13292/j.1000-4890.202203.027

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To explore the characteristics of soil nutrients of citrus orchards with different parent materials, clarify the influence of soil parent materials on fertility, and provide theoretical basis for orchard management and precise fertilization, 217 citrus soils with five different parent materials were collected to analyze soil pH, and the contents of organic matter, macro, medium and trace elements. The results showed that the mean soil pH value in citrus orchard was less than 5.5, and the soil was acidic. Except for plate shale and limestone, organic matter of other parent materials was deficient. Quaternary laterite was rich in exchangeable calcium and magnesium, while other parent materials were poor. The contents of soil alkalihydrolyzable nitrogen, available zinc, boron and molybdenum in each parent material were suitable, while available potassium, available phosphorus, sulfur, iron, manganese and copper were excessive. Analysis of variance showed that all soil indices except available copper and zinc were significantly different among different parent materials. The contents of soil organic matter, alkalihydrolyzed nitrogen, available phosphorus, available potassium, and available iron, copper and molybdenum in plate shale were higher than those in other parent materials, while the contents of exchangeable calcium and magnesium were lower than those in other parent materials. According to the comprehensive scores of principal components, soil fertility of each parent material was as follows: plate shale > sandstone > quaternary laterite > river-lake alluvial sediments > limestone. With the extension of citrus planting years, soil fertility of plate shale, river-lake alluvial sediments, and limestone soil was extremely significantly improved, and that of quaternary laterite was significantly increased. Comprehensive analysis shows that soil nutrients developed in plate shale were the most abundant. Soil organic matter, alkali-hydrolyzed nitrogen, available potassium, available boron, available phosphorus, and available sulfur were important factors affecting fertility. Due to the differences of soil nutrients in different parent materials, orchard soil should be accurately managed in case of local conditions to ensure the sound development of orchards.

Distribution characteristics of Rhizoctonia solani and Sclerotium rolfsiiin the soil of urban green space in Shanghai.

LUO Shu-hong, LUO Yu-zhen, ZHANG Wei-wei, LIU Wen, HE Shan-wen, AN Lei, WANG Yong-jie, HAN Ji-gang

2022, 41(5):  941-947.  doi:10.13292/j.1000-4890.202205.017

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To clarify the distribution characteristics of Rhizoctonia Solani and Sclerotium Rolfsii, which are seriously harmful to landscape plants in the urban green space in Shanghai, we quantitatively measured the abundance of ITS gene of two pathogens in the soil by realtime fluorescence quantitative PCR. Soil physical and chemical properties were simutaneously analyzed. The results showed that soil pH of green space is slightly alkaline, with high soil water content. The coefficient of variation of soil physical and chemical indices was high. The detection rates of R. solani and S. rolfsii in the soils were 99.7% and 11.6%. The average abundance of ITS gene was 9.09×10⁵ and 2.42×10⁵ copies·g^-1, respectively. There was significant difference in ITS gene abundance of R. solani between the green space soil of park and road (P<0.05), and no difference between that of downtown and suburb sites (P>0.05), indicating that green space types affect ITS gene abundance of R. solani. There was no significant difference in ITS gene abundance of S. rolfsii between the green space soil of park and road, and between that of downtown and suburban sites (P>0.05). ITS gene abundance of S. rolfsii was significantly negatively correlated with soil total chromium, total nickel, and total arsenic contents. These results contribute to better understanding of the prevention and control of R. solani and S. rolfsii in the soil of urban green space in Shanghai.

Effects of hydrological managements on soil enzyme activities during peatland restoration in the Changbai Mountains.

ZHAO Jing, DUAN Lei-lei, WANG Ming, WANG Sheng-zhong, CHEN Cong, LI Hong-kai, LI Xing-li

2022, 41(5):  948-954.  doi:10.13292/j.1000-4890.202203.005

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We analyzed the effects of hydrological management measures on soil enzyme activities (0-10 cm) and their driving factors during peatland restoration across natural peatland, restored peatland under different hydrological managements (high water level, alternating high-low water level, and low water level) and the degenerated peatland (abandoned land) in Changbai Mountains. The results showed that the activities of β-1,4-glucosidase and β-1,4-N-acetyl-glucosaminidase decreased from natural peatlands to restored peatlands to degraded peatlands. The activity of acid phosphatase in degraded peatlands was significantly lower than that in natural and restored peatlands, while the activity of polyphenol oxidase was the lowest in natural peatlands. In the restored peatlands, the activities of soil β-1,4-glucosidase, β-1,4-N-acetyl-glucosaminidase and acid phosphatase decreased gradually with the decreasing water level. However, the activity of soil polyphenol oxidase was the lowest in the restored peatlands under the hydrological management with alternating high-low water level. The activities of β-1,4-glucosidase andβ-1,4-N-acetylglucosaminidase were positively correlated with soil organic carbon content, water content, water level and total nitrogen content, and negatively correlated with pH and total phosphorus content. Soil acid phosphatase activity was positively correlated with soil water level, and negatively correlated with pH and total phosphorus content. Soil polyphenol oxidase activity was negatively correlated with soil organic carbon content, water content and total nitrogen content. Results of redundancy analysis showed that environmental factors explained 81.2% of the total variation in soil enzyme activities. Water level and soil organic carbon content were the main factors controlling soil enzyme activities. Our results indicate that appropriate hydrological management can effectively improve the contents of soil organic carbon, nitrogen and other nutrient elements and soil microbial enzyme activities of thedegraded peatlands, enhance soil ecological function, and accelerate the recovery of ecosystem function in peatlands.

Effects of water environmental factors on the biological toxicity of lanthanides.

SUN Li-zong, GUO Cheng, TAI Pei-dong

2022, 41(5):  955-962.  doi:10.13292/j.1000-4890.202205.023

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The expansion of the application of lanthanides (rare earth elements) has aroused wide attention to their biological safety. To explore the effects of environmental factors on the biological toxicity of lanthanides, using zebra fish (Danio rerio) as the test organism, we examined the effects of water environmental factors (pH, HCO₃^-, Ca²⁺Mg²⁺, K⁺, Cl^-, etc.) on biological toxicity and bioaccumulation of lanthanides, and analyzed the toxicity levels and trends of four representative lanthanides (La, Ce, Gd and Ho) under different water environmental conditions. The results showed that in standard water, the 96 h-LC₅₀ of La to adult Danio rerio was 165.6 μmol·L^-1. Its toxicity was significantly related to pH, HCO₃^- and Ca²⁺Mg²⁺ in the water, with its slopes being 0.912, 1.135 and 0.222, respectively, and had little relationship with Cl^-, Na⁺, K⁺ and SO₄^2-. At the beginning of the test, the four lanthanides could be complexed with HCO₃^- to form precipitated particles. A decrease in pH or HCO₃^- could promote the conversion of lanthanides from granular state to soluble state, with enhanced biological toxicity and bioaccumulation. Under the conditions of pH 5.0 and HCO₃^- 0.2 mmol·L^-1 (excluding the influence of lanthanide precipitation), four lanthanide elements showed a consistent trend of toxicity (6.11-6.43 μmol·L^-1 of 96 h-LC₅₀ for Danio rerio). We speculate that the difference in the toxicity of the four lanthanide elements in standard water may be due to the difference in the effective state of a single element rather than the different toxicity of the elements. Therefore, before the differences in biological toxicity mechanisms are revealed, lanthanides can be considered as a group of elements with a toxicity additive model for biological toxicity assessment. The evaluation process should focus on the effects of pH and carbonates.

Analysis of activity rhythm and habitat selection of water deer based on the infraredtriggered camera technology in autumn and winter in urban forest park.

HAN Qian, LIANG Tao, ZHANG Man-yu, LIU Meng-meng, WANG Zhen-qi, LU Chang-hu

2022, 41(5):  963-972.  doi:10.13292/j.1000-4890.202203.011

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Water deer (Hydropotes inermis) is an endemic species in East Asia, whose natural distribution onlyoccurs in China and Korean Peninsula. Because of the excessive human disturbance and habitat fragmentation, the population size of water deer has shown a sharp decreasing trend during the last several decades. To better understand their survival conditions in highly isolated urban forest parks, the activity rhythm and habitat preference of water deer in autumn and winter were monitored by infrared camera in Laoshan Forest Park and the surroundings in Nanjing, China. A total of 35 infrared-triggered camera-traps were installed from October 2020 to March 2021. The effects of temperature and vegetation type on the activity rhythm and habitat selection were analyzed using generalized linear model (GLM). During the monitoring period, 233 effective photos of water deer were taken by infrared cameras, contributing to 245 effective detection times. The relative abundance index (RAI) was 10.7. The daily activity rhythm of water deer displayed a typical bimodal pattern, with the intensive daily activities happening from 4:00 to 6:00 and from 18:00 to 20:00. The peak of monthly activities was in December. Temperature had significant effects on the daily activities of water deer, with the activity intensity being the highest when the environmental temperature was within a range from 4 to 6 ℃. Results of the generalized linear model showed that water deer tended to select habitats with evergreen deciduous broad-leaved forest and dominant shrub with height above 120 cm. In addition, the RAI index was positively correlated with the distance to road and negatively correlated with the disturbance index. Compared with its counterparts living in other large-scale nature reserves and water network areas, water deer showed typical morning and evening activity mode, no obvious diurnal or nocturnal activity patterns in Laoshan, with random selection on the distance from the nearest water source. Since the human disturbance in urban forest park is relatively high, reasonable control of human activities in Laoshan Forest Park and surrounding areas could be helpful to better safeguard water deer population in Laoshan.

Dynamics of Carcinoscorpius rotundicauda population at Shankou Mangrove Ecological and Natural Reserve, Guangxi.  

YING Zi-wei, LIN Wu-ying, XIAO Xiao-bo, ZHAO Xin-yi, LI Yin-kang, XIE Xiao-yong

2022, 41(5):  973-978.  doi:10.13292/j.1000-4890.202205.016

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Horseshoe crabs are precious marine ‘living fossil’. Little information is available on dynamics of Carcinoscorpius rotundicauda population. During the period of 2014 to 2020, wemonitored C. rotundicauda population at Shankou Mangrove Reserve in Behai, Guangxi. A total of 990 individuals of C. rotundicauda were recorded, with a declining trend of the population. In the sixth survey year, the population decreased by 94.60% compared with that in the first survey year, indicating thatthe conversation of this species is imperative. Male accounted for 80.28% of the total individuals, while females accounted for 17.50%. The population of C. rotundicaudafluctuated seasonally, and the population size was significantly positively correlated with temperature and the north and south wind direction states (0 and 4), suggesting biological characteristics of coastal vane for C. rotundicauda. This study help understand the population dynamics of C. rotundicauda and its influencing factors, providing reference for the protection of C. rotundicauda resources in the reserve.

Effects of temperature in parental reproduction and embryo incubation on hatching performance of zebrafish.

ZHENG Xue-Li, FU Shi-jian, XIA Ji-gang

2022, 41(5):  979-984.  doi:v

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Parental effect refers to the effects of parental phenotype or environmental factors they experienced, instead of the genotype, on the phenotypic difference or adaptability of offsprings, which is ecologically important for the maintenance and improvement of offspring’s fitness. To explore the impacts of parental effects on the plasticity of embryo development of zebrafish (Danio rerio), the effects of parental reproduction and embryo incubation temperature (22 and 28 ℃), and their interactions on the hatching performances (hatching rate, embryo mortality, deformation rate of newly hatched fry, hatching duration, initial hatching time and final hatching time) were determined using a 2×2 twofactor design. The results showed that the interaction between parental reproduction and embryo incubation temperature had significant impacts on embryo mortality, initial hatching time, final hatching time, and hatching duration (P<0.05). Embryos had lower mortality and shorter hatching duration when the parental reproduction temperature was consistent with the embryo incubation temperature. The results suggest that zebrafish hatching performance is affected by both parental effects (intergenerational developmental plasticity) and offspring developmental environment (intra generational developmental plasticity). Parental effects play an important role in shaping the phenotypic characteristics of fish in the early life history stage.

Growth characteristics of statolith morphology of Berryteuthis magister shevtsovi.

TENG Yu-rong, LU Hua-jie, CHEN Zi-yue, NING Xin, LIU Kai, CHEN Xin-jun

2022, 41(5):  985-991.  doi:10.13292/j.1000-4890.202203.028

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Statolith is one of the most important hard tissues in Cephalopods, which is widely used in the study of Cephalopod fishery biology and ecology. Based on 261 samples of Berryteuthis magister shevtsovi collected in theJapan Sea in December 2018 by the Chinese Jigging fleets, we examined the statolith shape and growth characteristics. The results of principal component analysis showed that the total statolith length (TSL), wing length (WL), rostrum lateral dome length (RLL) and maximum width (MW) could be used as the morphological characteristic parameters to study the morphological growth of statolith. The analysis of covariance showed no significant gender difference in the relationships between the morphological characteristic parameters and mantle length (ML) as well as body weight (BW). Akaike’s information criterion indicated that linear function could be best describing the relationships between ML and TSL or WL, power functions were best for the relationships between ML and RLL, and logarithm functions for ML and MW. The relationships between BW and TSL, BW and MW were best described by linear functions, but power function for BW and WL. The relationship between BW and RLL was best described by logarithm function. The absolute size of statolith gradually increased with increasing ML, but the morphological structure ratio of statolith remained basically unchanged.

Views on distinguishing the concepts of rangeland and grassland and proposing proper use of their terminology.

DONG Shi-kui

2022, 41(5):  992-1000.  doi:10.13292/j.1000-4890.202205.001

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Rangeland and grassland are two key terms used in multiple disciplines and departments. However, there are confusion, overlap and crisscross in the use of these two terms due to their chaotic connotation and denotation defined by various disciplines and departments. In order to clarify the connotation and denotation of rangeland and grassland in different contexts of disciplines and departments, and to enhance their proper use in practice, I collected diverse and rich references and information in rangeland and grassland terminology, summarized the connotation and denotation of rangeland and grassland defined in various countries and disciplines, clarified the terminology changes of rangeland and grassland across different time and disciplines. Finally, I proposed proper use of those two terms to mitigate the confusion, overlap and crisscross and to provide a scientific basis for rational protection and utilization of grassland resource and ecosystems. The conclusions are based on the comprehensive analysis. There are broad and narrow definitions of rangeland and grassland. The broad definitions are derived from the international subjects of agriculture and vegetation as well as national subjects of agriculture and law, in which rangeland and grassland can be regarded as the synonym referring to the landbiology resources with multiple functions and production base for pratacultural industry, where herbaceous species dominate the vegetation with some shrubs and sparse trees used as the habitats or foods for livestock and wildlife, as well as good living environments and biological products for the human beings. These terms have been generally used as “rangeland” or “grassland” in the official documents of forestry, grassland, and agriculture departments, foreign and domestic literatures, textbooks, courses, etc. The narrow definitions are derived from the national subjects of vegetation science and land types. In the subject of vegetation science, it is defined as the zonal vegetation distributed in semiarid and semihumid areas with the perennial xerophytes as dominant plants (occasionally with some small subshrubs) in the community. The term is normally applied for vegetation classification and should be generally used as “steppe or grassland vegetation” (e.g., temperate grassland vegetation or steppe vegetation). In the subject of land types, it is defined as one of the land use types, dominated by herbaceous species. This term is normally used for land use classification by land resource (natural resources) department and should be generally used as “land type of grassland”.

CO₂ emission characteristics of headwater streams and the influencing factors: A review.

WANG Ji-long, WANG Xiao-feng, YUAN Xing-zhong, WU Sheng-nan, LI Hang

2022, 41(5):  1001-1014.  doi:10.13292/j.1000-4890.202203.002

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Headwater stream plays a vital role in connecting terrestrial ecosystems with inland rivers, and is also a foremost interface of linking the terrestrial carbon sink with oceanic one. With the intensely biogeochemical processes, headwater streams are important contributors to CO₂ emission budget from global inland waters and therefore affecting global carbon cycling. Clarifying the production and emission processes of CO₂ in headwater streams, and illuminating their spatiotemporal characteristics as well as main regulating factors will be beneficial to re-understand carbon processing ability for river systems. Here, we reviewed the primary sources and processes of CO₂ in headwater streams, including in-stream production and external input. We systematically analyzed the spatial and temporal variations at different time scales (i.e., annual, seasonal, daily and diurnal) and spatial scales (i.e., global, regional, watershed, and habitat) of CO₂ emission from headwater streams. We summarized that the meteorological factors, stream structure characteristics, hydro-geomorphological factors, land environmental factors, and in-water physical and chemical factors were key regulators of the spatiotemporal variations in CO₂ emission from headwater streams. Meanwhile, we summarized current methods for CO₂ fluxes monitoring in inland water, and analyzed their applicability and optimization in headwater streams. We constructed a theoretical framework integrating the headstream waters into the carbon budget of headwater catchments, and proposed that the contribution of CO₂ emission from streams to the terrestrial carbon balance cannot be ignored. Finally, based on the disadvantages existing in current research, we proposed several important research fields of CO₂ emission from headstream, including (1) the analysis of dynamic process of CO₂ emission from streams with different geographical environments; (2) the accumulation of observation database for headwater CO₂ emission with high spatiotemporal resolution in different regions; (3) the relationship of CO₂ emission from headwater stream with land landscape pattern as well as the regulatory mechanisms; (4) the response of headstream CO₂ emission to global climate change; (5) the accurate estimation of total CO₂ emission from regional and global headstreams; (6) the establishment and optimization of monitoring and research methods for headstream CO₂ emission.

The application of structural equation modeling in ecology based on R.

SHI Ya-Fei, SHI Shan-Heng, HUANG Xiao-Min

2022, 41(5):  1015-1023.  doi:10.13292/j.1000-4890.202203.016

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Structural equation modeling (SEM) is a major approach for analyzing ecological data. Differing from other multivariate statistical methods, SEM is mainly driven by assumptions and could quantify both direct and indirect causal relationships among multi-variables. Since the introduction of SEM into the field of ecology in China is relatively short, scientists encounter many problems when using SEM, with various mistakes. Therefore, we elaborated principles, processes, evaluation and modification of SEM in this review. With a case study, we introduced the usage of two major R packages for SEM, i.e. lavaan and piecewiseSEM. Concretely, lavaancan perform SEM with latent variables, while piecewiseSEM can incorporate nonindependent observations, and handle response variables with residuals not satisfying multivariate normal distribution. This review can help researchers understand and use SEM correctly and accurately, and promote the usage of SEM in ecology.

Classification of dominant species in coniferous and broad-leaved mixed forest on Changbai Mountain based on UAV-based hyperspectral image and deep learning algorithm.

ZHENG Di, SHEN Guo-chun, WANG Bo-jian, DAI Guan-hua, LIN Fei, HU Jia-rui, YE Ji, FANG Shuai, HAO Zhan-qing, WANG Xu-gao, YUAN Zuo-qiang

2022, 41(5):  1024-1032.  doi:10.13292/j.1000-4890.202203.004

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Rapid and accurate identification of tree species and their distribution patterns is the basis and premise for forest resource management and biodiversity conservation. Compared with the traditional field investigation methods, the rapid development of the surface of remote sensing technology in recent years can obtain high resolution hyperspectral remote sensing images flexibly, efficiently, and conveniently. However, how to select features with large amount of information and low redundancy from many features containing rich information for automatic tree species identification is an urgent problem. We used spectral sensors carried by unmanned aerial vehicles to take hyperspectral images, which covered an area of 6 hm² of the 25 hm² temperate mixed conifer-broadleaf plot in Changbai Mountain. Six canopy tree species, including Pinus koraiensis, Ulmus davidiana, Quercus mongolica, Fraxinus mandshurica,Populus ussuriensis, and Tilia amurensis, were selected as the field labeled tree species. Realtime Kinematic Phase Difference (RTK) technology was used to accurately capture the position of those target tree species. In addition, visual interpretation of the image of the study area was performed using ArcGIS based on the forest re-inventory results in 2019. Three classification methods, including convolutional neural network, maximum likelihood and Mahalanobis distance, were used to analyze the automatic classification of canopy tree species. Our results showed that: (1) The overall accuracy and Kappa coefficient of tree species classification of convolutional neural network (99.85%, 0.998) were better than maximum likelihood (89.11%, 0.86) and Maharanobis distance method (79.65%, 0.75); (2) Among the three classification methods, the classification accuracy of single dominant tree species was the highest when using the convolve neural network, and the highest classification accuracy of P. koraiensis, U. davidiana, Q. mongolica, F. mandshurica, P. ussuriensis and T. amurensis were 100%, 99.9%, 99.9%, 99.8%, 99.8% and 99.5%, respectively. (3) Overall, convolutional neural network had the lowest degree of mixing, while Mahalanobis distance method had the most serious degree of mixing problem. This study indicated that the convolutional neural network model based on deep learning approach can obtain the accurate and efficient classification of canopy species in natural temperate forests, which could provide a great step forward into the species diversity monitoring and forestry resource survey.

Recognition and extraction of planting area of Chinese wolfberry based on Sentinel-2A.

WANG Zhao-yang, SHI Yin-fang, HOU Cheng

2022, 41(5):  1033-1040.  doi:10.13292/j.1000-4890.202205.007

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 Jingyuan County is one of the main production areas of Lycium barbarumL., an important cash crop in Northwest China. It is important to quickly and accurately obtain the information about planting structure and spatial distribution of L. barbarum for local agricultural adjustment and regional economic sustainability. Based on Sentinel-2A image data and objectoriented classification method, a random forest classifier was established, with the planting information of L. barbarum being extracted using spectral and textural features. The results showed that the random forest classification combined spectral features with textural features had the highest accuracy. The overall accuracy was 88.14%, the Kappa coefficient was 0.81, and the user accuracy of wolfberry was 81.03%. The planting area of L. barbarumin Jingyuan was 297.12 km², characterized by large-scale concentrated and sporadic distribution. The planting bases in several towns, including Jing’an, Wuhe, Dongsheng and Beitan, were the main distribution sites. In addition, Sentinel-2A was good ateffectively extracting scattered planted L. barbarum. Our results provided support for the adjustment of planting structure and development and utilization of L. barbarum in Jingyuan County. The method used here provided reference for remote sensing monitoring of L. barbarum in a large area.