Table of Content

10 March 2023, Volume 42 Issue 3

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Changes of community structure and diversity of natural forests in mountainous areas of central Hainan Island.

LI Chendi, YANG Xiaobo, LI Donghai, SHI Jiankang, ZHAO Junfu, LI Long, CHEN Lin, ZHANG Peichun, TIAN Lujia

2023, 42(3):  513-523.  doi:10.13292/j.1000-4890.202303.013

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To understand the changes of community structure and diversity of natural forests in mountainous areas of central Hainan Island, two surveys were conducted in the montane rain forest in Wuzhishan, the lowland rain forest in Jianfengling, the montane rain forest in Diaoluoshan and the cloud forest in Bawangling from 2012 to 2020. A plot with a size of 1600 m² was set up for each forest type. The temporal variations of community structure, tree growth, tree mortality and species diversity in eight years were analyzed. The results showed that from 2012 to 2020: (1) DBH size-class and tree height class of the montane rain forest in Wuzhishan and the lowland rain forest in Jianfengling showed an inverted “J” shape. DBH sizeclass of the montane rain forest in Diaoluoshan and the cloud forest in Bawangling showed an inverted “J” shape, while tree height class showed a near “L” shape. The community structure became more complex over time. (2) Height growth rate of young trees was faster. With the increase of DBH, growth rate of tree height decreased and growth rate of DBH increased. The number of dead indivi duals decreased with the increase of DBH. Young trees had a strong competition for resources, such as sunlight. (3) The change rates of population size of Pterospermum heterophyllum, Garcinia oblongifolia, Prismatomeris tetrandra and Symplocos hainanensis were higher than 5%, indicating rapidly changing populations. Pioneer species were gradually replaced by transitional species. (4) The average change rate of species diversity was +1.48%, +1.59%, +4.19%, and +12.26% in the montane rain forest in Wuzhishan, the lowland rain forest in Jianfengling, the montane rain forest in Diaoluoshan and the cloud forest in Bawangling, respectively. Most of the immigrating and exiting species were occasional species, which accounted for the changes of species diversity. Community succession of the damaged forests in the mountainous areas of central Hainan Island can be well restored, the structure complexity, species diversity and community stability of which can be effectively improved by effective enclosure.





The characteristics of stratification diversity of pine-oak mixed forests in the Nanpan River Basin.

LI Jie, LI Yuanfa, LU Daodiao, YE Shaoming, TIAN Jia

2023, 42(3):  524-533.  doi:10.13292/j.1000-4890.202303.010

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Natural forests in subtropical regions are usually mixed, multilayered, and uneven-aged, with a few stands being vertically stratified. However, few studies have examined the diversity characteristics of different layers in stratified stands. Analyzing species diversity and structural diversity at vertical layers is conductive to understand the causes of stratification and its role in maintaining species coexistence. In this study, we evaluated diversity at different layers of pine-oak mixed forests located in the Nanpan River basin, Southwest China, using 11 traditional indices of species diversity and three structural diversity indices. The results showed that: (1) Species richness (R), Shannon index (H), Simpson index (D), Brillouin index (HB) and Fisher’s alpha diversity index (α) of the understory was higher than that of the canopy (P<0.01). The abundance (N), Heip evenness index (E_h), Pielou evenness index (E_H), Alatalo evenness index (E_a), Sheldon evenness index (E_s) of the understory was higher than that of the canopy on the whole. The Jaccard similarity index between those two layers was 0.29-0.52. (2) For the understory and canopy layers, 56.4%-60.1% and 56.7%-58.9% of individual trees were in a status of random distribution (W=0.50), 19.1%-23.9% and 17.3%-21% in cluster (W=0.75, 1.00), 19.6%-20.8% and 21.5%-26.0% in uniform (W=0.00, 0.25), respectively. (3) The average species mixture of the understory layer (M=0.50-0.72) was higher than that of canopy layer (M=0.31-0.61). The mixture of understory layer gradually increased with increasing grades of mingling (M) in all measured plots that were mainly characterized by high and complete mixture (M=0.75, 1.00) (44.4%-64.4%), and canopy layer had a low-level species mixture (M =0.00, 0.25), accounting for 22.6%-64.5%; (4) The dominance (U) of each layer was about 0.5, while the frequency of each dominance grade was close to 20%. These results suggest that the stratification determines the diverse characteristics of pine-oak mixed stands and their layers, which could be an important mechanism underlying species coexistence and the maintenance of stand physical structure. More attention should be paid to the role of stratification in biodiversity conservation and management of forests.





Natural restoration characteristics and assembly mechanisms of soil microbial community in tropical rainforest under different  disturbance types.

YU Jingjing, CONG Wei, DING Yi, JIN Lixiao, ZHANG Yuguang

2023, 42(3):  534-543.  doi:10.13292/j.1000-4890.202303.007

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Community structure and co-occurrence relationships of soil microorganisms were studied using Illumina high-throughput sequencing technology to better understand restoration characteristics and assembly mechanisms of soil microbial communities during natural restoration of forest. Tropical rainforests with naturally restored for 40-60 years after three types of disturbance (slash and burn, clear cutting, and selective cutting) were compared with old-growth forests. A Null model was used to quantify the relative contributions of deterministic processes and stochastic processes in microbial community assembly. Results showed that soil physicochemical properties (total nitrogen, hydrolysable nitrogen, and available potassium) in the slash and burn forests were not significantly different from that in the old-growth forests. Plant diversity was significantly lower than old-growth forests (P<0.05). Soil bacterial diversity was not significantly different from that of old-growth forests, but soil fungi richness was significantly lower (P<0.05). Most soil physicochemical properties, including total nitrogen, available phosphorus and available potassium, as well as plant diversity, were significantly higher after clear cutting and selective cutting than that in old-growth forests (P<0.05). There was no significant difference in soil microbial diversity. Soil microbial community structure of forests from the three different disturbance types was significantly different from that of old-growth forests (P<0.05). Results of ecological network analysis showed that slash and burn and clear cutting disturbances reduced network complexity of soil microorganisms, while selective cutting increased the complexity. Network structure (total nodes, total links and modularity) of soil bacteria was greater than that of soil fungi. The Null model analysis showed that the relative contribution of stochastic processes (bacteria: 54.76%-66.58%; fungi: 87.62%-93.57%) was higher than deterministic processes (bacteria: 33.42%-45.24%; fungi: 6.73%-12.38%). The slash and burn disturbance had the greatest impact on soil microbial diversity and community structure. After a long-term natural recovery, soil microbial diversity did improve, with greater recovery for bacteria than for fungi, but with large differences in soil microbial community structure and relationships. Our study elucidated microbial community structure and assembly processes in forest soils affected by different disturbances, which is important for predicting ecosystem function of soil microorganisms and their responses to environmental changes.





Trade-off and synergy analysis of ecological services of Grain for Green Program in Loess Plateau: A case study of Ansai County.

YU Hang, JIN Lei, TAN Bingxiang, QI Zhao, SHEN Mingtan, MOU Shaohua

2023, 42(3):  544-551.  doi:10.13292/j.1000-4890.202303.015

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The Loess Plateau is one of the regions characterized by the most serious soil erosion and land degradation in China, and also a critical area for the Grain for Green Program (GGP). This study aimed to assess the implementation effect of the GGP in the Loess Plateau and to inform ecological environment restoration for sustainable development. Ansai County of Shaanxi Province, a central area implementing the GGP in the Loess Plateau, was selected as the study area. InVEST model was used to assess the impacts of the GGP on the changes in ecosystem services (soil conservation, flood regulation, carbon storage, water yield). The tradeoffs and synergies among ecosystem services were analyzed, while ecosystem services under different implementation scenarios for the GPP were simulated. The results showed that GPP significantly changed land cover pattern of Ansai County from 2000 to 2015. The GPPrelated change in land use (conversion of farmland to woodland, shrub land, grassland, etc.) was 464.93 km2 (accounting for 15.8% of the total area), of which the conversion of farmland to grassland accounted for the largest proportion (71.8%). After the implementation of GGP, flood regulation function increased by 33.4%, carbon storage increased by 39.6%, soil conservation increased by 5.3%, and water yield decreased by 22.4%. Results of scenario analysis showed that, under the conditions that the area and proportion of farmland returned to forest and grassland remain unchanged, the priority of returning farmland to forest (grassland) in steep slope and riparian farmland would significantly enhance soil conservation, while other ecosystem services remain unchanged or decline slightly. The GPP would weaken the trade-off effect among ecosystem services when riparian (100 m distance from a river) and steep-sloped farmlands are primarily converted. This study provides a reasonable implementation scheme for program planning and improves the effect of ecological governance.





Effects of long-term fertilization on soil physicochemical and biological properties of chestnut calcareous soil in agro-pastoral ecotone.

GAO Riping, ZHAO Peiyi, LIU Xiaoyue, ZHANG Jun, LI Huanchun, HUANG Jie, JING Yupeng, DUAN Yu

2023, 42(3):  552-560.  doi:10.13292/j.1000-4890.202303.019

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This study aims to explore the effects of long-term fertilization in arid chestnut soil, to reveal the changes of soil physicochemical and microbial properties under different fertilization schemes. Results would provide basis for reasonable fertilization and scientific evaluation of fertilization effects in the agro-pastoral zone of Inner Mongolia. Based on a long-term rotation fertilization positioning experiment (2004-2019) at Wuchuan Dryland Experimental Station in Inner Mongolia, we examined the effects of different fertilization schemes on the topsoil physicochemical and biological properties of chestnut calcareous soil in the agro-pastoral zone. The results showed that long-term organic manure combined with chemical fertilizer (NPK+OM) and single organic manure (OM) applications significantly reduced soil bulk density and increased soil porosity, while unbalanced fertilization (such as NP, NK, PK, N) and no fertilization (CK) showed an increasing trend in soil bulk density. Compared with CK, the contents of soil organic carbon, total nitrogen, alkaline hydrolysis nitrogen, available phosphorus and available potassium were increased in other treatments. The magnitudes of improvement for soil nutrients were ranked as follows: organic manure combined with chemical fertilizer > organic manure > chemical fertilizer balanced application > chemical fertilizer unbalanced application > no fertilization. In terms of soil microorganisms, soil bacterial abundance increased by 108.36%-118.92%, fungal abundance increased by 27.68%-50.46%, actinomycetic abundance increased by 35.43%-40.25% in NPK+OM. Long-term application of organic manure and balanced application of chemical fertilizer improved soil structure, soil nutrients, and microorganism abundance. In particular, the combination of organic manure and chemical fertilizer is the most effective. The application of reasonable ratio of nitrogen, phosphorus and potassium significantly improved soil quality of arid chestnut soil in the agro-pastoral ecotone, unbalanced fertilization also improved soil properties, while no fertilization significantly degraded soil properties in the long term.





Variations of mean residence time of organic carbon pools in red paddy soil in a typical area in recent 10 years.

WANG Xiyang, LI Xiaohui, XIN Zaijun, HE Shifu, SUN Xiaoyan, LI Liang

2023, 42(3):  561-568.  doi:10.13292/j.1000-4890.202303.032

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It is crucial to understand the spatiotemporal variations of mean residence time (MRT) of soil organic carbon (SOC) pool for taking effective measures to enhance carbon sink of agricultural ecosystems. In this study, a new round of soil sample collection was carried out based on historical sampling information, and a 100 d incubation experiment was carried out. Then, the data were fitted to a three-pool first-order kinetics model to estimate the MRT of active SOC pool (MRT_a) and slow SOC pool (MRT_s). We analyzed the spatiotemporal variations and the influencing factors of MRT_a and MRT_s in surface paddy soil in Dongxiang of Jiangxi Province from 2009 to 2019. The results showed that the MRT_a and MRT_s of paddy soil in Dongxiang in 2019 were 26.5 days and 14.1 years, respectively, both of which showed no significant changes compared with that in 2009. The active and slow SOC pools in the southern Dongxiang were generally more stable than the other areas. There were obvious spatiotemporal variations both in MRT_a and MRT_s in red paddy soil in Dongxiang, with the variation ranges of -1.3%-544.5% and -6.7%-1375.5%, respectively. Such variations were partly due to the spatial differences in the proportion of active and slow SOC pools in the total SOC. Compared with other rice-growing areas in southern China, the SOC pool of red paddy soil in Dongxiang was more stable in recent 10 years, despite substantial spatial variation.





Effects of rice straw returning by wet harrow in autumn on soil enzyme activities and nutrients.

SONG Peng, YANG Zhenzhong, WAN Zuliang, WANG Xintong, ZHANG Wenzhong, WANG Guojiao

2023, 42(3):  569-576.  doi:10.13292/j.1000-4890.202302.024

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Straw returning is an effective way to maintain and improve soil quality. To explore the effects of straw returning by wet harrow in autumn on soil enzyme activity, soil nutrient content and rice yield in southern Liaoning rice region, an experiment following randomized block design was conducted in Panjin City, Liaoning Province. There were two factors with two levels of each factor, namely, no straw returning (S₀), total straw returning (S₁), panicle fertilizer reduction of 16 kg·hm^-2 (N₁) and conventional panicle fertilizer dosage of 32 kg·hm^-2 (N₂). The results showed that straw returning to the fields by wet harrow in autumn significantly increased the activities of β glucosidase, urease and FDA hydrolase in the soil, and significantly decreased the activities of invertase. The activity of alkaline phosphatase was significantly decreased at tillering stage and heading stage by straw returning, but increased by 6.2%-13.5% at maturity stage compared with S₀N₂. Polyphenol oxidase activity was significantly decreased at tillering stage, but increased by 20.8%-26.7% and 22.3%-28.7% at heading and maturity stages compared with S₀N₂, respectively. Soil available potassium, organic carbon and total nitrogen contents at different growth stages of rice were significantly increased by returning straw with wet harrow in autumn, while soil nitrate content and soil pH at tillering stage and mature stage were significantly decreased by straw returning with wet harrow in autumn. The soil ammonium content at tillering stage of rice was significantly increased by 42.2%-41.0%, compared with that of S₀N₂. There was no significant difference in soil nitrate nitrogen, available phosphorus, available potassium and organic carbon contents between S₁N₁ and S₁N₂. Soil polyphenol oxidase activity was significantly positively correlated with soil organic carbon content, while alkaline phosphatase activity was significantly positively correlated with soil available phosphorus content. The activities of soil urease, FDA hydrolase and β glucosidase were significantly positively correlated with soil available potassium and total nitrogen contents. Soil invertase activity was significantly negatively correlated with soil ammonium nitrogen, nitrate nitrogen, available potassium, organic carbon and total nitrogen contents. There was no significant difference in rice yield among different treatments. In summary, straw returning to the fields by wet harrow combined with reduced application of panicle ferti-lizer in autumn can stabilize yield and maintain soil nutrient balance, promote soil nutrient supply and transformation, which has guiding significance for straw returning treatment in rice area of southern Liaoning.





The effects of ratoon rice cultivation on soil fertility and chemical structure of soil organic carbon.

XIONG Li, SHAO Caihong, ZHANG Wenxue, MARIOS Drosos, ZHOU Xiaohua, LIU Shengxiao, LIU Zengbing, SUN Gang, WANG Shaoxian

2023, 42(3):  577-583.  doi:10.13292/j.1000-4890.202303.028

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The ratoon rice cultivation is important to stabilize rice production under the background of double rice system shifting to single rice system. To investigate the effects of ratoon rice cultivation on soil organic carbon (SOC) and soil fertility, we analyzed the differences of soil nutrients and chemical structure of SOC among single, double, and ratoon rice systems. Soil pH of ratoon rice field was significantly lower than that of single rice field, but no difference with double rice field. The contents of main nutrients in soils generally followed the order: double rice filed>ratoon rice field>single rice field. Accordingly, soil fertility index (SFI) of three rice systems was 0.66, 0.47, and 0.40, with significant difference among each other. The chemical structure of SOC was significantly different among the three rice cultivation systems. The proportion of soil Alkyl-C in ratoon rice field was significantly higher than that in single rice field but lower than that in double rice field. In contrast, the proportion of soil O-Alkyl-C in ratoon rice field was significantly lower than that in single rice field but higher than that in double rice field. The ratio of Alkyl-C/O-Alkyl-C under ratoon rice filed increased by 23.81% compared to single rice field, but decreased by 30.67% compared to double rice field. The Alkyl-C/O-Alkyl-C ratio was significantly and positively correlated with SOC content (R²=0.95, P<0.001) and SFI (R²=0.96, P<0.001). In conclusion, soil fertility of ratoon rice filed is higher than that of single rice field but lower than that of double rice field, which is closely related with fertilizer input, flooding period, and crop nutrient uptake.





Effects of yak excreta addition on nitrogen transformation in alpine peatland soil in northwestern Yunnan Province.

FAN Fenghua, WANG Xue, ZHANG Kun, ZHENG Rongbo, GUO Xuelian

2023, 42(3):  584-590.  doi:10.13292/j.1000-4890.202303.005

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Yak grazing could significantly affect soil environments by changing the transformation and transportation of soil nitrogen, with consequences on primary production of alpine wetland ecosystems. However, little is known about the effects of yak excreta addition on soil nitrogen transformation in peatlands of northwestern Yunnan. In this study, the effects of yak excreta addition on nitrogen transformation of peatland soil was measured in a controlled experiment using soil cores collected from a typical peatland in northwestern Yunnan. The results showed that the addition of yak dung and urine promoted the accumulation of NH₄⁺-N at the early stage. The NH₄⁺-N content was reduced in peatland soil with excreta addition during the whole incubation, but the NO₃^--N content was increased, indicating that nitrification was the dominant process. The addition of dung and urine significantly increased urease activity in peatland soil, but reduced denitrifying enzyme activity (P<0.05). The addition of dung enhanced the activities of catalase and N-acetylglucosaminidase (P<0.05), while the addition of urine inhibited the activity of N-acetylglucosaminidase (P<0.05). The effects of dung addition did not affect nitrogen mineralization and nitrification (P>0.05), but urine addition significantly affect nitrification during the incubation (P<0.05). Dung addition inhibited, but urine addition promoted denitrification during the incubation. Changes in soil physicochemical pro perties and enzyme activities with yak excreta addition play an important role in altering denitrification in peatland soil.





Potential and affecting factors of N₂O production through abiotic processes of hydroxylamine and nitrite in wetland soils of Min River Estuary.

QI Mengting, LUO Liu, WANG Wanzhen, QIAN Wei, TONG Chuan, LI Xiaofei

2023, 42(3):  591-598.  doi:10.13292/j.1000-4890.202303.008

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Abiotic nitrogen transformation processes can generate N₂O in estuarine wetlands. The abiotic processes of hydroxylamine (NH₂OH) and nitrite (NO₂^-) can produce N₂O, but production potential and affecting factors remain unclear. We conducted an experiment with three treatments (without nitrogen addition (CK), NH₂OH and NO₂^- additions) to determine N₂O production rates from abiotic processes in wetland soils of Min River Estuary. The results showed that N₂O production rates significantly differed among three treatments (P<0.05). The potential production rates of N₂O from abiotic processes under NH₂OH addition, NO₂^- addition, and without nitrogen treatments ranged from 16.88 to 307.99, -0.50 to 27.51 and -1.20 to 2.97 ng·g^-1·h^-1, respectively. The contributions of N₂O production from abiotic processes of NH₂OH and NO₂^- additions were 20.74%-98.73% and 1.27%-79.26%, respectively. Average N₂O production rates of abiotic processes for all the five soil types varied significantly among the three treatments (P<0.05). The average N₂O production rates of abiotic process of NO₂^- were in the order of Kandelia candel>Spartina alterniflora>Phragmites australis>Scirpus mariqueter>Cyperus malaccensis, while the rates of abiotic processes of NH₂OH were S. mariqueter>S. alterniflora>P. australis>C. malaccensis>K. candel. These results suggest that abiotic processes of NH₂OH have higher N₂O production rates compared to NO₂^-, and the N₂O production from abiotic processes of soil NH₂OH and NO₂^- varied largely among different vegetation soils. Soil pH, NO₂^-, NO₃^-, Fe²⁺， Fe³⁺  and C/N ratio were crucial factors affecting N₂O production rates from abiotic processes of NH₂OH and NO₂^-.





Screening of stabilization materials for arsenic and cadmium co-contaminated soil suitable for freeze-thaw process.

WANG Song, WANG Yi, SHI Liu, LI Xiaojun, CHEN Zhonglin, HOU Wei, GONG Zongqiang, JIA Chunyun

2023, 42(3):  599-606.  doi:10.13292/j.1000-4890.202303.004

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Freezing-thawing alternation is an important factor affecting the stabilization and remediation of heavy metals in contaminated soils in northern China, but few studies are available at present. In this study, 19 kinds of common heavy metal stabilized materials were used to explore the effects of freeze-thaw alternation on soil physicochemical properties and stabilization of As and Cd with 15 freezing-thawing cycles. The results showed that the stabilized materials increased pH and electric conductivity of compound contaminated soil. The application of six materials, including clay minerals (SL), amendment (MCA, SA2), biochar (MBC, FBC1, FBC2), stabilized 15.0%-32.0% As and 14.0%-33.0% Cd simultaneously, with MCA having the best stabilization effect, followed by MBC. The stabilization effect on As and Cd was significantly affected by freeze-thaw alternation. After 15 cycles of freeze-thaw, the pH of stabilized soil showed a rising trend. Under such environment, biochar (MBC, FBC1, FBC2) addition further reduced the availability of heavy metals in soil. MBC addition increased the stabilization effect on As and Cd by 14.2% and 12.5%, respectively. In general, biochar (MBC) befits the remediation of As and Cd contaminated soil in the cold northern China.





Relationship between vegetation spatial distribution pattern and soil factors in drainage ditches in arid irrigation area.

LI Shan, WANG Qian, FAN Qianwen, WU Miao, ZHANG Lei, FEI Liangjun, XUE Renming, LI Lan

2023, 42(3):  607-616.  doi:10.13292/j.1000-4890.202302.023

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Revealing the relationship between vegetation distribution in drainage ditches and soil factors can provide theoretical basis and technical guidance for restoring eco-environment of ditch wetlands and construction of ecological irrigation areas in arid environment. With a case study on the main and sub-main drainage ditches of a saline area in Lubotan reclamation area at Fuping of Shaanxi Province, we examined spatial and temporal distribution of vegetation, as well as soil water content, electrical conductivity (EC) and pH on side slope of drainage ditches, and the correlation between vegetation and soil properties based on field investigation, variance analysis, correlation analysis, typical correlation analysis and RDA analysis. The results showed that: (1) Vegetation on the side slope of the drainage ditches displayed obvious zoning pattern, including a reed area, transition area, and a symbiosis area. The species in main ditches were more diverse than that in the sub-main ditches, whereas species dominance was lower than that in the sub-main ditches. The Simpson dominance index decreased with the distance from drai-nage ditches in different areas of main ditches and sub-main ditches, while species richness index, Shannon diversity index and Pielou evenness index increased with the distance from drainage ditches. (2) Soil moisture was the highest in March (23.7% on average), and soil EC and pH were the highest in September (with a mean value of 576.97 μS·cm^-1 and 8.95, respectively), with no significant differences among different time periods. Soil moisture, EC, and pH of reed area in main ditches were the highest. Soil water content of reed area in sub-main ditches was the highest, while soil EC and pH in the transition area were the highest, with significant differences among different areas. (3) Soil moisture and EC were the key factors driving the spatial distribution and plant species richness in drainage ditches in the arid region. Based on those findings, we put forward artificial intervention methods and measures of controlling drainage and laying prefabricated vegetation blanket to regulate vegetation succession and vegetation construction in ecological drainage ditches in arid regions. Our results may provide scientific basis for the construction of ecological irrigation area.





Effects of soil water content on non-structural carbohydrates and growth of Pinus sylvestris var. mongolica seedlings

WANG Kai, LU Shan, LIU Chang, KANG Hongzhang, LYU Linyou, JIAO Xiangli

2023, 42(3):  617-625.  doi:10.13292/j.1000-4890.202303.011

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To clarify growth adaptation strategies of Pinus sylvestris var. mongolica seedlings under different soil water contents, two-year-old seedlings were grown under different water conditions, i.e., 80%, 60%, 40%, and 20% of soil field water capacity (SFC) for 15, 30, 45, and 60 days. We measured the contents of soluble sugar, starch, non-structural carbohydrate and biomass of different organs. The results showed that height, basal diameter, and  one-year-old needle, fine root and total biomass decreased with decreasing soil water content. Under soil water content of 80% SFC, soluble sugar concentrations were higher in stems and lower in current-year needles and fine roots, while starch concentrations were higher in stems and coarse roots. Under 60% and 40% SFC, soluble sugar concentrations were higher in needles and fine roots, while starch concentrations were higher in stems and one-year-old needles. Under 20% SFC, soluble sugar concentrations were higher in current-year needles and lower in one-year-old needles, while starch concentrations were higher in fine roots and lower in stems and coarse roots. These results indicated that P. sylvestris var. mongolica seedlings had higher growth rate and stress resistance under 80% SFC, exhibited higher resource utilization efficiency and optimal carbon storage strategy under 60% and 40% SFC, and stopped growing under 20% SFC. Therefore, soil water content should be maintained above 7% to promote natural regeneration of P. sylvestris var. mongolica plantation in Horqin Sandy Land.





Comparison of stoichiometric characteristics of main nutrients in different organs of four Chenopodiaceae species.

SU Yuhang, SONG Xiaoqian, ZHENG Jingwen, ZHANG Zhonghua, TANG Zhonghua

2023, 42(3):  626-634.  doi:10.13292/j.1000-4890.202303.012

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Soil nutrient deficiency is one of the main factors limiting plant biomass in saline-alkali land. Chenopodiaceae is a dominant group in saline-alkali land. In this study, four Chenopodiaceae species, Suaeda glauca, Chenopodium acuminatum, Salsola tragus, and Bassia dasyphylla, were selected to evaluate the difference of quantitative characteristics of habitat soil factors and seven elements in different organs, aiming to clarify plant stoichiometry and its relationship with soil nutrients in saline-alkali ecosystems. The results showed that: (1) Soil Na content and soil electronic conductivity of S. glauca population were significantly higher than that of the other three species. Soil N content in S. tragus population was the lowest, while soil P content was the lowest in B. dasyphylla population. (2) Foliar C/N was in an order of S. glauca>S. tragus>C. acuminatum>B. dasyphylla. Root C/P of C. acuminatum was significantly higher than that of the other three species. Foliar N/P was more than 16 and root N/P was less than 14 in all species except C. acuminatum. (3) The K contents in all organs were significantly higher in B. dasyphylla. The Ca contents in leaves and roots were significantly higher in S. tragus. The Na contents in all organs were significantly higher in S. glauca. Mg contents in leaves and roots were significantly higher in B. dasyphylla. (4) The N enrichment coefficients and Ca enrichment coefficients in all organs were significantly higher in S. tragus. The P enrichment coefficients and K enrichment coefficients in leaves, stems and roots were significantly higher in B. dasyphylla. The Na enrichment coefficients in all organs were significantly higher in S. glauca. Our results indicated that N use efficiency was the highest in S. glauca, P use efficiency in roots was the highest in C. acuminatum, S. glauca had the strongest ability to absorb Na from soil, B. dasyphylla had the strongest ability to absorb P and K from soil, and S. tragus had the strongest ability to absorb N and Ca from soil.

Nitrogen allocation strategy of Scirpus mariqueter based on ¹⁵N tracing analysis on Nanhui coasts and restoration. suggestions

HE Ning, HU Yang, WU Mingxuan, ZHANG Bolun, ZHANG Shengle, WU Pengling, WANG Maoqiu, WANG Qinyi, HE Peimin, FANG Shubo

2023, 42(3):  635-642. 

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Current researches related to ecological restoration of Scirpus mariqueter wetland mainly focus on the statistics of external apparent data and experimental exploration of appropriate modes, with limited understanding on the internal material regulation mechanism of S. mariqueter under different elevations. A ¹⁵N labeling experiment was conducted to explore N distribution characteristics of S. mariqueter under different elevations in the middle and late growing seasons, aiming to provide ecological restoration suggestions. The results showed that in the middle growing season, aboveground allocation rate of new uptake ¹⁵N increased as the elevation decreased, indicating that S. mariqueter tended to allocate more N to the aboveground part to adapt to environmental stress. In the end of growing season, the new uptake ¹⁵N was strongly concentrated to underground part, indicating that S. mariqueter maintained its settlement potential for the following year by allocating more N to underground part in strongly disturbed areas with tidal flooding. The allocation rate of new uptake of ¹⁵N was much higher in corms than that in seeds, indicating that the allocation of N in the propagators was mainly in corms and secondarily by seeds. Based on the ¹⁵N tracing results, we present following suggestions: when ecological restoration is carried out by patch transplanting, patches should be dug out in the area with the same disturbance degree and transplanted nearby; when ecological restoration is carried out through propagules, corms should be preferentially selected to design restoration schemes, and seed banks should be constructed for future germination, while seeds and corms should be selected in relatively high altitude areas with better environment.





Effects of polyaspartic acid and chitosan copolymer on photosynthetic characteristics, nitrogen use efficiency, and yield of foxtail millet.

WANG Qi, XU Yanli, YAN Peng, DONG Haosheng, ZHANG Wei, LU Lin, DONG Zhiqiang

2023, 42(3):  643-652.  doi:10.13292/j.1000-4890.202303.024

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To investigate the effect of polyaspartic acid-chitosan (PAC) on photosynthetic characteristics, nitrogen use efficiency, and yield of spring foxtail millet under the background of one-time basic fertilizer application, an experiment following split plot design was conducted using foxtail millet varieties of “Zhangzagu 13” (Z13) and “Huayougu 9” (H9) in Gongzhuling Experimental Station of Chinese Academy of Agricultural Sciences in 2020 and 2021. PAC and different nitrogen application levels were main treatment and secondary treatment, respectively. There were six nitrogen application levels (0, 75, 112.5, 150, 225, and 337.5 kg·hm^-2). The results showed that PAC improved apparent efficiency of applied nitrogen for both foxtail millet varieties under the same nitrogen application level. The leaf area index and SPAD value of flag leaf in 0-40 days after anthesis were higher than those of the control. PAC application increased photosynthetic rate, transpiration rate, and conductance to H₂O, but significantly decreased intercellular CO₂ concentration of flag leaf at anthesis and mid-filling stage, which could promote dry matter accumulation and yield. The yield of Z13 was increased by 11.24%-21.55% in 2020 and 8.65%-14.22% in 2021, and that of H9 was increased by 5.53%-15.75% and 10.43%-16.17% in 2020 and 2021, respectively. PAC application effectively relieved nitrogen deficiency and plant premature senescence resulted from one-time basic fertilizer application during the late growth period of foxtail millet, and reduced nitrogen loss caused by low nitrogen use efficiency. Therefore, PAC combined with nitrogen fertilizer application could be used as a green, high-yielding, and high-efficiency cultivation technique in foxtail millet production in China.





Effects of rising atmospheric CO₂ concentration and warming on the variation of dissolved organic carbon in double cropping rice fields.

LI Min, JIA Yuxuan, SUN Juan, WANG Bin, WU Yuxin, WANG Shunli, SHI Shengwei

2023, 42(3):  653-661. 

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Global climate change, characterized by elevated atmospheric CO₂ concentration and temperature, is an important issue affecting human sustainable development. In this study, open top chamber (OTC) systems were used to simulate climate change scenarios of rising atmospheric CO₂ concentration (EC, +100 ppm) and increasing temperature (ET, +1.5 ℃). The concentration of dissolved organic carbon (DOC) in surface water and pore water, aromaticity index, biomass, yield and related driving factors of double cropping rice in Jianghan Plain were observed. The results showed that DOC concentration in soil pore water at 20 cm soil layer during the filling stage of early rice was significantly increased by 284.2% under EC treatment, compared with CK (P<0.05), and DOC aromaticity index under EC treatment was significantly decreased by 36.9% and 31.6% at booting stage and heading stage (P<0.05), respectively. DOC aromaticity index at 20 cm soil layer during the jointing stage of early rice reduced by 35.5% under EC treatment (P<0.05). Compared with EC and ET treatments, DOC aromaticity index of soil pore water at 20 cm soil depth under the combined treatment of atmospheric CO₂ concentration increasing and warming (ETEC) was significantly increased, with a range of 23.6%-51.4% during the whole growing period of paddy field (P<0.05). Both EC and ET treatments significantly increased aboveground biomass and grain yield of double cropping rice (P<0.05). This study provided scientific evidence for exploring the responses of double cropping rice to climate change and the key processes of carbon cycling in paddy ecosystems in Jianghan Plain in China.





Effects of selenium forms on the absorption and accumulation characteristics of rice leaves at different positions.

SHI Liu, ZHENG Dongmei, LI Xiaojun, LIN Xin, SUN Jingjing, CAO Lixia

2023, 42(3):  662-667.  doi:10.13292/j.1000-4890.202303.001

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To better serve the optimization of selenium fertilizer formulation and spraying system, we should clarify the redistribution of selenium applied on leaves after entering into crops and screen out the appropriate selenium form for foliar spraying. We examined the effects of foliar spraying of four forms of selenium on selenium absorption and accumulation in different leaves, stems and roots of rice “Daohuaxiang 2” by hydroponic method at seedling stage. The results showed that the distribution of exogenous selenium in leaves was related with different positions. The selenium concentration in the sprayed leaves (the 4th leaf) was the highest, and decreased gradually along the upper and lower leaves. The organic selenium tended to be transported to young leaves. Foliar spraying of sodium selenite significantly increased selenium accumulation in rice seedlings compared with sodium selenate, zinc selenite and selenomethionine treatments. Selenium concentration in leaves under the treatment of spraying sodium selenite increased by 131.4 times, up to 129.21 mg·kg^-1, and that in the stems and roots was 18.6 times and 2.2 times higher than that in the control, respectively. Therefore, selenium in sprayed leaves at the seedling stage could be transported to upper and lower leaves. A large amount of selenium was accumulated in the lower first leaves of selenium-sprayed leaves. Sodium selenite had the best effect on selenium accumulation in rice.





Effects of 14-hydroxylated brassinosteroid·thidiazuron on photosynthetic characteristics, antioxidant system, and yield of rice under salt stress.

HUANG Lu, YU Minglong, FENG Naijie, ZHENG Dianfeng, MA Guohui

2023, 42(3):  668-676.  doi:10.13292/j.1000-4890.202303.029

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To investigate the alleviating effects of spraying Nengbaiwang 2.0 (0.16% 14-hydroxylated brassinosteroid·thidiazuron+polyglutamic acid) at different stages on rice growth and yield under salt stress, hybrid rice ‘Xiangliangyou 900’ and commonly cultivated rice ‘Huanghuazhan’ were used as the experimental materials to examine the effects of continuous spraying Nengbaiwang for 2 (sprayed once at tillering stage and heading stage) or 3 (sprayed once at tillering stage, heading stage, and grain filling stage) times on photosynthetic characteristics, antioxidant metabolism, osmotic regulation, and yield of rice under 0.3% salt stress. The results showed that salt stress inhibited the growth of both rice varieties, significantly decreased net photosynthetic rate (Pn), and reduced yield by 33.7% and 43.2% in Xiangliangyou 900 and Huanghuazhan, respectively. Foliar spraying Nengbaiwang could alleviate the negative effects of salt stress on rice growth. Spraying Nengbaiwang twice significantly increased the effective tillers of Xiangliangyou 900 and Huanghuazhan, and spraying three times significantly increased plant height, stem diameter, total leaf number, flag leaf length, and inverted second leaf length of Huanghuazhan under salt stress compared with the single salt treatment. Foliar spraying Nengbaiwang for two or three times significantly increased the P_n, stomatal conductance (G_s), chlorophyll content, the activities of antioxidant enzymes (SOD, CAT, POD, and APX), the levels of non-antioxidants (AsA and GSH), and proline accumulation. However, it decreased the contents of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) under salt stress compared to the single salt treatment. The yield loss of Xiangliangyou 900 and Huanghuazhan was alleviated by 20.0% and 14.3%, respectively, after spraying twice Nengbaiwang, and 14.5% and 28.6%, respectively, after spraying three times Nengbaiwang. In conclusion, foliar spraying Nengbaiwang could reduce the damage caused by salt stress on rice by enhancing photosynthetic activity, antioxidant system, and osmotic regulation potential, thus alleviating yield loss under salt stress.





Distribution patterns of intertidal macroalgal diversity and biomass in the Guangdong-Hong Kong-Macao Greater Bay Area.

LIU Linqing, LIU Zhiwei, HE Quan, YANG Yufeng, ZOU Dinghui

2023, 42(3):  677-684.  doi:10.13292/j.1000-4890.202303.023

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A four-season survey of intertidal macroalgae resources at eight sites in the Guangdong-Hong Kong-Macao Greater Bay Area was conducted from September 2020 to August 2021 to better understand the distribution and diversity of intertidal macroalgae biological resources in the Greater Bay Area. The variations of diversity and community structure of intertidal macroalgae across the four seasons were analyzed. A total of 91 species in 53 genera from three macroalgae phyla were recorded, including nine genera and 19 species of Chlorophyta, 36 genera and 59 species of Rhodophyta, and eight genera and 13 species of Ochrophyta. Seasonal pattern of macroalgae species were spring > winter > summer > autumn, with uneven seasonal distribution. Most of them were warm temperate seaweeds. A total of 14 species were classified as the dominant populations, with significant seasonal variations. The average annual biomass of macroalgae was 2800.65 g·m^-2, with a seasonal pattern of spring (7914.89 g·m^-2) > winter (2266.44 g·m^-2) > summer (653.12 g·m^-2) > autumn (368.13 g·m^-2), and a vertical pattern of low-tide zone (7075.98 g·m^-2) > mid-tide zone (1112.60 g·m^-2) > high-tide zone (213.37 g·m^-2). The vertical distribution was different across sites in each season. Diversity indices showed significant seasonal differences. The macroalgae species in the Greater Bay Area were abundant and with huge biomass. The species richness and biomass displayed significant seasonal and regional variations.





Seasonal variations and environmental drivers of suitable habitats of Todarodes pacificus in southern Yellow Sea and East China Sea.

YANG Linlin, JIANG Yazhou, ZHANG Hui, YUAN Xingwei, LIU Zunlei

2023, 42(3):  685-693.  doi:10.13292/j.1000-4890.202303.027

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We analyzed the fishery resource and environmental data collected from four trawl surveys conducted in southern Yellow Sea and East China Sea during autumn 2018, winter 2019, spring 2019 and summer 2019, aiming to understand habitat suitability and environment characteristics of Todarodes pacificus in southern Yellow Sea and East China Sea, elucidate the seasonal variations and environmental drivers of suitable habitats, and promote rational utilization and scientific management of T. pacificus. The temporal and spatial variations of the suitable habitat in the southern Yellow Sea and the East China Sea in different seasons were analyzed based on habitat suitability index. The contribution rate of various environmental factors to suitable habitats was analyzed using boosted regression tree model. The migration path of T. pacificus was deduced by combining the seasonal changes of suitable habitat. The results showed that the optimal surface temperature, surface salinity, bottom temperature, bottom salinity, and water depth for T. pacificus were 9.8-27.5 ℃, 23.2-34.3, 8.9-20.2 ℃, 31.6-34.7 and 56-133 m, respectively. The environmental preference of T. pacificus displayed significant seasonal variations. The suitable habitats showed a south-north cycle throughout the year, which were mainly concentrated in middle-northern East China Sea and offshore of southern Yellow Sea. The contribution rate of water temperature to the suitable habitats was the largest, followed by salinity and depth. In conclusion, the suitable habitats of T. pacificus were different across seasons in southern Yellow Sea and East China Sea. T. pacificus migrated northward or southward into the feeding grounds and spawning grounds. Temperature was the most important environmental driver of the suitable habitats.





Spatial distribution of eggs of Stolephorus commersonnii in the Pearl River Estuary.

TIAN Fengge, HE Wei, HUANG Binbin, LOU Quansheng, HU Huina, DENG Wei

2023, 42(3):  694-701.  doi:10.13292/j.1000-4890.202303.018

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The spatial distribution of eggs of Stolephorus commersonnii and its relationship with water mass were studied based on ecological survey data of four cruises in the Pearl River Estuary in August of 2013, 2017, 2019, and 2020. The adaptability of the S. commersonnii eggs to salinity was analyzed using Gaussian model. According to K-means cluster analysis of water temperature and salinity, the survey region could be divided into three water masses: runoff water, brackish mixed water, and high-salinity water. The eggs of S. commersonnii were distributed in the regions of brackish mixed water and high-salinity water, but almost not in runoff water. The relationship between egg abundance and sea surface salinity (SSS) was consistent with the Gaussian model in August 2020. The optimal SSS was 16.28, ranging from 11.76 to 20.80, while the tolerance range was from 7.24 to 25.32. The eggs of S. commersonnii were mainly distributed in the middle of the Pearl River Estuary, including south of Neilingding Island, waters around Qingzhou, Guishan and Lantau islands. In the northern part of the Pearl River Estuary, the distribution of S. commersonnii eggs varied with the fluctuation of runoff input. There were almost no eggs in 30 m deep shelf area towards southeast.





Influence of landscape factors on golden takin (Budorcas taxicolor bedfordi) group.

QI Hongyun, GONG Minghao

2023, 42(3):  702-707.  doi:10.13292/j.1000-4890.202302.019

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Group living is the social behavior of ungulates, with important consequences on the responses of individuals and populations to environmental changes, and thus is considered as an important survival strategy to increase population fitness. The effects of food resources and predator risks on group living have been widely stu died. However, less is known about the impacts of habitat landscape features. Golden takin (Budorcas taxicolor bedfordi) is a typical group-living species. We collected spatial location information, age structure, and group size of each takin group in Shaanxi Sangyuan National Nature Reserve by extracting data from infrared cameras. The correlation between group structure and landscape factors, including slope and altitude, was calculated, with the aim to investigate the main topographical factors and their characteristics affecting the takin group living structure. The  results showed that: (1) Slope was significantly correlated with group size (r=0.336, P=0.006), while group size was not significantly associated with both elevation and aspect. (2) The influence of slope varied significantly between small size group (≤ 7 individuals) and big size group (> 7 individuals) (P=0.015). (3) The small size groups were mainly composed of adult takins, with a high proportion of male individuals, which preferred environment with small slope (12.42°±0.21°). The inter-specific competition is relatively strong in this area and vegetation composition is relatively rich. The big size groups were mainly family groups with a large proportion of takin juve niles and a high proportion of adult females, preferring to choose environment with a large slope (22.02°±0.95°). The competition between species is relatively small and the vegetation composition is relatively simple. The results indicated that slope was the main landscape factor affecting the scale, type, and structure of golden takin groups, and that the spatial environment and interspecific competition pressures selected by different groups were also signi ficantly different.





Dynamic patterns of habitat connectivity of local giant panda populations in Liangshan Mountains.

MAO Zeen, HONG Yang, WANG Yujun, FU Liqiang, LUO Huan, HUANG Yaohua, LIU Tingting, BAI Wenke, ZHANG Jindong, ZHOU Caiquan

2023, 42(3):  708-715.  doi:10.13292/j.1000-4890.202303.016

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Habitat loss and fragmentation are the major threats to many endangered species. Establishing ecological corridors can mitigate the negative effects of habitat fragmentation and connect isolated giant panda populations. To understand the patterns in changes of habitat connectivity among local populations of giant panda (Ailuropoda melanoleuca), we analyzed the dynamics and influencing factors of suitability and connectivity of suitable habitats for giant pandas in three adjacent reserves (Mabian Dafengding, Meigu Dafengding and Mamize) in Liangshan Mountains using data from the third and fourth National Survey of giant pandas (the 3rd survey in 2000 and the 4th survey in 2010). The results showed that the highly suitable habitat area of giant pandas increased by 73 km² from 3rd to 4th survey, mainly distributed in Mabian Dafengding and Meigu Dafengding nature reserves, while decreased by 4 km² in the junction regions of those two reserves. The areas with decreased connectivity were mainly distributed in Meigu Dafengding Reserve and the north of Mabian Dafengding Reserve, with an area of 625 km², and the overall connectivity in the study area showed a downward trend from 3rd to 4th survey. The area of increased connectivity was 617 km² in the southern part of Mabian Dafengding Reserve and Mamize Reserve. In addition, the least-cost path method was used to simulate the distribution of giant panda potential corridors. The total length of potential corridor was 5130 km in the 3rd survey and 4003 km in the 4th survey, with a reduction of 1127 km from the 3rd to 4th survey. We analyzed the reasons for the changes of suitable habitat distribution and habitat connectivity of giant pandas by combining conservation policies with the economic development characteristics of the surrounding communities. We found that with the implementation of relevant conservation policies (e.g., The Natural Forest Conservation Program and Grain to Green Program), forest ecosystems and giant panda habitats were effectively protected. However, due to the adjustment of the livelihood mode of local residents (from relying on traditional agriculture to animal husbandry which could provide higher economic value), the intensity of human activities in some areas had been increased, which hindered the connectivity of giant panda habitats. We suggest that local conservation and management departments need strictly manage the emerging human disturbances to ensure better connectivity of giant panda population, so as to protect the stability and growth of local giant panda population.





The spatial-temporal variations of ground temperature at the depth of 0 cm in different regions across China during 1961-2020.

ZHANG Lei, GUO Anhong, CAO Yun, ZHAO Xiaofeng

2023, 42(3):  716-724.  doi:10.13292/j.1000-4890.202303.022

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Ground temperature is an important component in earth-atmosphere system. Understanding the changes in ground temperature is of great significance for deepening knowledge of climate change and ecosystem adaptation to climate change. The spatial-temporal variations in ground temperature at the depth of 0 cm were explored in 10 regions across China during 1961-2020, especially for up -to-date climatic baseline period of 1991-2020, by using linear trend and Cramér-von Mises methods based on daily observations from 640 meteorological stations. During 1961-2020, the average increment of ground temperature at the depth of 0 cm for yearly, spring, summer, autumn and winter was 0.41, 0.42, 0.16, 0.34 and 0.70 ℃·(10 a)^-1, respectively. The average increment in 1991-2020 relative to 1961-1990 was 0.52-2.12 ℃. Yearly and seasonal average ground temperature at the depth of 0 cm decreased from south to north. Only a few stations observed obvious increasing trend during 1961-1990, while most stations showed an obvious increasing trend during 1991-2020, and the increasing rate in northern areas was greater than that in southern areas. Regional increment of average ground temperature at the depth of 0 cm in 1991-2020 relative to 1961-1990 was 0.23-2.16, 0.24-2.18, -0.21-1.69, 0.18-1.52 and 0.20-4.35 ℃ for yearly, spring, summer, autumn and winter, respectively. When comparing across different regions, the increment of average ground temperature was larger in Northeast China, Inner Mongolia and Xinjiang, which was larger in winter and smaller in summer. The increasing trend of yearly and seasonal average ground temperature at the depth of 0 cm was not obvious in most regions during 1961-1990, but showed an increasing trend during 1991-2020. The increasing rate of average ground temperature at the depth of 0 cm was the greatest in winter, followed by spring, autumn, and summer. Moreover, the abrupt change years of significant difference of annual and seasonal ground temperature were generally after 1991.





Research progress on ecological adaptation, physiological and genetic mechanisms of animal personality in small mammals.

GAN Lin, LIU Wei, WANG Dehua

2023, 42(3):  725-735. 

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Mounting evidence has shown that animal personality is correlated with behavior, physiology, genetics and ecological adaptation. However, most studies about animal personality focus on non-mammals, with limited understanding on mammals (especially small mammals). Here, we review the origin of animal personality conception and the establishment of research methods. From the perspective of ecological adaptation, we summarized the research progress of behavior (including foraging, reproduction, dispersal and group living), physiology and genetic consequences of animal personality in small mammals. Furthermore, we summarized current research status of two important hypotheses about the adaptive mechanisms of animal personality, “the pace of life syndrome” hypothesis and “the state-behavior feedback” hypothesis. Finally, we discussed and prospected the possible future developments of animal personality research in small mammals.





Research advances in water environmental carbon cycle in the Yangtze River Basin.

WANG Wei, GUO Qingjun, DU Chenjun, DENG Yinan

2023, 42(3):  736-747.  doi:10.13292/j.1000-4890.202303.002

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As one most important material cycling on the earth, carbon cycling has great implications for global climate change and human well-being. Carbon in rivers could reflect the changes in climate and environment in river basins, and is a key part of the global carbon cycle. The Yangtze River Basin is the largest basin in China, with wide distribution of carbonate rocks, which has huge carbon sequestration potential. Due to the complexity of natural environment change in the Yangtze River Basin, our understanding of water environment carbon cycle under the background of global change is still limited. Here we review the temporal and spatial variations and source of carbon in the water environment and the carbon sink data of rock weathering in the Yangtze River Basin. The source and distribution of organic carbon are mainly affected by human activities. Inorganic carbon mainly comes from the chemical weathering of rocks in the Yangtze River Basin. Rock weathering has great potential in carbon sink. Under the influence of global change, the migration and transformation of these carbonic materials may lead to new ecolo-gical and environmental problems, which is of great significance for predicting future environmental changes. Our work provides a basis for the study of carbon cycle in the Yangtze River Basin.





Ecosystem landscape pattern change and its response to climate in desert steppe of Inner Mongolia.

ZHU Xiaohua, YANG Qian, DING Zixiao, LI Chuanrong, TANG Lingli, CHEN Binbin

2023, 42(3):  748-758.  doi:10.13292/j.1000-4890.202303.020

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Desert steppe is an ecotone between desert and steppe. Desert steppe is very fragile. Furthermore, it is difficult to restore once destroyed. Desert steppe in Siziwang Banner is one of the most arid types in the temperate steppe of Inner Mongolia. The evolution of landscape pattern in desert steppe is not only related to the diversity of grassland ecosystem, but also has important significance for the restoration of ecological functions of neighboring ecosystems. In this study, we assessed the change of landscape pattern and habitat quality in Siziwang Banner desert steppe based on remote sensing technology, landscape ecology theory, and  InVEST model. We analyzed its responses to climate factors based on the key parameter NPP to enhance our understanding of desert steppe. From 2003 to 2017, the fragmentation degree of ecosystem landscape pattern in Siziwang Banner was increased, the connectivity of dominant patch landscape was further weakened, and the overall habitat quality was decreased by about 2%, showing obvious regional differences. The NPP of Siziwang Banner decreased year by year, with a spatial distribution pattern of decreasing in the north and increasing in the south. NPP in Siziwang Banner grassland was more correlated with cumulative precipitation than with air temperature. There was an obvious legacy effect, with a lag time of 2.96 months.





Temporal and spatial variations of ecological quality of Chengdu-Chongqing Urban Agglomeration based on Google Earth Engine cloud platform.

WU Xiaobo, FAN Xiaoyu, LIU Xiaojing, XIAO Lin, MA Qimin, HE Ning, GAO Sizhuo, QIAO Yuting

2023, 42(3):  759-768.  doi:10.13292/j.1000-4890.202303.009

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Rapid urbanization has a stressful effect on regional ecological environment. Timely monitoring of ecolo-gical quality changes is thus crucial for urban ecological management and planning. The remote sensing-based ecological index (RSEI) is an objective, quick, and easy tool for monitoring and evaluating ecological quality, which has been frequently used in ecological research. However, large-scale and long-term monitoring is frequently confronted with the problem of cloud blockage. Based on Google Earth Engine (GEE) cloud platform and its massive MODIS remote sensing images, we calculated remote sensing indices of greenness, humidity, dryness, and heat of Chengdu-Chongqing Urban Agglomeration (CCUA) annually by using the median synthesis method, and constructed the RSEI using the principal component analysis to evaluate the temporal and spatial variations of ecological quality in this area in the past 20 years. The results showed that: (1) The RSEI of the CCUA showed a slow upward trend and remained stable since 2012. The ecological quality in hilly area of central Sichuan and Chengdu Plain had been deteriorated dramatically, and were significantly improved in mountainous areas of the northeastern Chongqing; (2) The changes in the CCUA’s ecological quality showed clear spatial autocorrelation. The Moran’s I index was 0.825. Greenness and wetness indices were positively correlated with RSEI, while heat and dryness indices were negatively correlated with it, and the greenness was the primary driver for the changes in ecological quality of the CCUA. (3) Image processing based on GEE cloud computing may considerably enhance image processing efficiency, and address the problem of remote sensing data missing due to overcast and wet conditions. It also has the potential to broaden the scope of RSEI’s use in large-scale and long-term sequence ecological monitoring. Our findings can be used as a theoretical basis for environmental conservation and land management under the context of rapid urbanization.