Table of Content

15 November 2019, Volume 30 Issue 11

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Relationship between the main functional traits of fine root and the rhizosphere soil nutrients of different diameter classes in Zenia insignis plantation.

CHEN Liu-juan, ZHONG Quan-lin, LI Bao-yin, YAO Xiang-ming, XU Chao-bin, CHENG Dong-liang, ZHENG Yue-fang, YU Hua

2019, 30(11):  3627-3634.  doi:10.13287/j.1001-9332.201911.006

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Fine roots are sensitive to changes in the soil environment, and play an important role in plant growth and development. To clarify the relationship between fine root traits and rhizosphere soil nutrient characteristics, fine roots of trees belonging to different diameter classes in six-year-old Zenia insignis plantation were sampled. The results showed that root biomass, root length density and root volume density increased with the increases of diameter class. Specific root length and specific root area showed the trend of first rising and then falling and rising again with the increases of diameter class. Root tissue density did not change with diameter class. There were significant diffe-rences in soil pH, water content, total carbon, total phosphorus, ammonium nitrogen, nitrate nitrogen and total available nitrogen contents of rhizosphere soil belonging to different diameter classes. The concentrations of soil total carbon, total nitrogen, nitrate nitrogen and total available nitrogen in the rhizosphere soil of large diameter trees were relatively higher, while the soil water content, total phosphorus and ammonium nitrogen contents of small diameter trees were relatively higher. The concentrations of soil total nitrogen, total carbon, nitrate nitrogen and total available nitrogen were significantly positively correlated with root biomass, root length density and root volume density. The concentrations of soil total phosphorus was significantly positively correlated with root tissue density of fine roots, but negatively correlated with specific root length and specific root area. Soil water content was significantly positively correlated with root biomass and root volume density. Soil pH was significantly positively correlated with the specific root length and specific root area of fine roots, but negatively correlated with root tissue density. Our results provide scientific basis for the selection of excellent germplasm resources of Z. insignis.

Niche characteristics of understory dominant species of talus slope in degraded tiankeng

GUO Ping-ping, SHUI Wei, JIANG Cong, JIAN Xiao-mei, ZHU Su-feng, ZHANG Yong-yong, FENG Jie, CHEN Yi-ping

2019, 30(11):  3635-3645.  doi:10.13287/j.1001-9332.201911.007

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We carried out niche monitoring and analysis of plant populations under the forest community in the talus slope ecotone of a typical moderate-degraded Bajiaxiantang tiankeng to provide scientific references for biodiversity conservation and vegetation restoration in degraded tiankeng area. The results showed that soil ammonium, available potassium, and available phosphorus signifi-cantly affected species distribution, which explained 37.4%, 32.8%, 29.3% of the total variation, respectively. With the change of talus slope of tiankeng (pit, uphill, mid-slope, downhill and pit bottom), life form of understory plants changed from evergreen and xerophytes to evergreen and hygro-mesophytes, with the niche overlap of herbs being larger than that of shrubs. Shrubs of Viburnum congestum and Campylotropis polyantha, and herbs of Arisaema erubescens and Arthraxon hispidus had wide ecological amplitude and strong resistance, which occupied the upper layer of the shrub and herb layers. Shrub Cornus oblonga and herb Geranium nepalense, Agrimonia pilosa lost the competitiveness with increasing soil alkalinity. Niche characteristics of understory dominant species in Bajiaxiantang were closely related to the canopy structure of mixed trees, ecological strategies of shrub and herb species, unique habitat of tiankeng, and the importance value of dominant species.

Response of understory species distribution of Robinia pseudoacacia plantation to environmental factors in loess hilly region, China.

WU Hui-feng, REN Li-na, HAO Wen-fang, LI Gang, SONG Li-juan, WU Shui-juan

2019, 30(11):  3646-3652.  doi:10.13287/j.1001-9332.201911.002

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We explored the distribution characteristics and influencing factors of understory species in Robinia pseudoacacia plantation in Wuqi, Ansai, Mizhi, Yichuan and other places, in combination with niche breadth, soil, altitude and other environmental factors. We analyzed the response mechanism of species distribution to environmental factor to provide a scientific basis for the mana-gement of R. pseudoacacia plantation in loess hilly region. The results showed that the broadly distributed understory species in R. pseudoacacia plantation were Setaria viridis, Heteropappus altaicus, Artemisia scoparia, Poa sphondylodes, Artemisia leucophylla, Ixeris sonchifolia, and Incarvillea sinensis. With the increasing rehabilitationage, the dominant understory species distribution followed the order: Artemisia capillaries → P. sphondylodes → A. scoparia → others (Rubia cordifolia, Rosa rubus and so on) → A. leucophylla → S. viridis. Results from principal component analysis showed that soil total phosphorus (25.6%), altitude (20.3%) and soil total nitrogen (19.3%) were the key factors influencing understory species distribution in R. pseudoacacia plantation. Soil organic carbon content, soil total nitrogen content, soil total phosphorus content, soil water content and the number of understory species distribution in R. pseudoacacia plantation were generally positively correlated with the degree of correlation varying across different species. There was no correlation between the slope aspect and the understory species distribution in R. pseudoacacia plantation. In conclusion, topography and soil factors played important roles in driving understory species distribution. The steeper the slope, the higher the altitude, the fewer understory species in R. pseudoacacia plantation. Understory species distribution was mainly affected by soil total phosphorus content and altitude. The understory species distribution reflected the differences of soil nutrient status, which had a certain guiding role in the management of R. pseudoacacia plantation.

Effects of the current-year shoot stem configuration on leaf biomass in different canopy heights of woody plants in evergreen broad-leaved forest in Jiangxi Province, China.

LU Yi-miao, WANG Man-tang, CHEN Xiao-ping, LYU Min, ZHONG Quan-lin, CHENG Dong-liang

2019, 30(11):  3653-3661.  doi:10.13287/j.1001-9332.201911.001

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To investigate the effects of stem configuration on leaf biomass allocation in different organs of the current-year shoots at different canopy heights, relationships of biomass in different organs (i.e., leaves, stems, and twigs) and stem configuration (i.e., stem diameter, length, width/length, stem volume and stem density) were analyzed using the data of 69 woody species from the Yangjifeng Natural Reserve, Jiangxi Provence. Standardized major axis (SMA) was used to explore the regression between biomass and stem configuration. The results showed that there was no significant difference in leaf biomass, stem biomass, twig biomass, stem diameter, stem length, stem width/length and stem volume of current year shoots from upper and lower canopy heights and life forms (i.e., evergreen and deciduous woody plants). Stem density differed significantly in the current year shoots at different heights for both evergreen and deciduous woody species. There were isometric relationships among leaf, stem and total biomass of shoots in different canopy heights and in different life forms. Leaf biomass scaled allometrically with stem diameter and volume, with the scaling exponents being not different significantly among different canopy heights. With respect to the stem configuration of the twigs, stem length, stem width/length and stem density contributed less than 24% to the leaf biomass variation in the current-year shoots. On the contrary, stem diameter and volume had greater effects on leaf biomass of the current-year shoots than stem length, stem width/length and stem density. Canopy heights did not significantly affect the allometric scaling relationships between the stem configuration and leaf biomass of the current-year shoots.

Effects of harvest residue treatments on soil phosphorus fractions and availability in a young Chinese fir plantation

JIA Shu-xian, WU Chuan-jing, LIU Xiao-fei, GUO Jian-fen

2019, 30(11):  3662-3670.  doi:10.13287/j.1001-9332.201911.012

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Forest harvesting changes the quantity and quality of organic matter inputs into soil, and thus would alter soil nutrient content and availability. Phosphorus (P) is a key element affecting plant growth. The effects of harvest residue treatments on soil P fractions and availability had not yet been evaluated. In this study, harvest residue retainment (RR), residue removal (R) and residue burning (RB) treatments were manipulated after clear-cutting in a mature Chinese fir (Cunninghamia lanceolata) plantation at the Sanming Forest Ecosystem and Global Change Research Station in Fujian, China. This study focused on the dynamics of soil P fractions and their driving factors in the 0-10 cm and 10-20 cm soil layers after 4-year residue treatments. The results showed that, in RR treatment, the contents of easily-available P, moderately-available P and non-available P at the 0-10 cm soil layer were all significantly higher than those in R treatment, while the contents of moderately-available P and non-available P at the 10-20 cm soil layer was significantly higher than those in RB treatments. The ratios of soil organic carbon (C) to organic P (C:Po) in both layers were over 200 for all the three treatments, with ratios in RR treatment being significantly lower than those in RB and R treatments, indicating that RR could alleviate P limitation in this ecosystem. Moreover, results of the redundancy analysis showed that changes in P fractions were mainly affected by dissolved organic C, free Fe and noncrystalline amorphous Fe. The results suggested that soil organic P and available P were mainly from the decomposition of plant residues, which supported continuous P supply for plant growth. RR could enhance soil P content, thereby improve soil P availability and mitigate P limitation in Chinese fir plantation.

Effects of girdling and defoliation on the growth of female cones and branches and nutrient content in different tissues and organs of Pinus koraiensis.

YIN Dong-sheng, WU Hai-bo, ZHANG Jian-ying, GE Wen-zhi, ZHOU Zhi-jun, SHEN Hai-long

2019, 30(11):  3671-3680.  doi:10.13287/j.1001-9332.201911.011

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To explore the nutrient source and supply-demand relationship of the female cone deve-lopment and new shoot growth of Pinus koraiensis, reproductive mother branches were experimentally girdled, defoliated, and under the combination of both treatments. The effects of different treatments on the female cones development, branch growth and the content of carbohydrate (NSC), nitrogen (N) and phosphorus (P) in different tissues and organs were measured. The results showed that girdling significantly affected female cone development, new shoot growth, and the contents of NSC, N and P in different tissues and organs, while defoliation treatment had limited effect. The NSC content in the mother branch xylem and phloem after girdling were significantly lower than that of the control (CK, ungirdling+0% defoliation), and decreased significantly with the increases of the degree of defoliation. The NSC content in mother branch xylem and phloem of girdling+100% defoliation was 59.0% and 64.8% lower than that of CK, respectively. The deficiency of NSC resulted in the death of mother branches and new shoots and the abortion of female cone. Under girdling treatment, the contents of N and P in xylem and phloem of mother branches of 0%, 50% and 100% defoliation treatment were significantly higher than that of CK. The contents of N and P in xylem of mother branches were 17.3%, 18.2% and 24.3% and 17.9%, 7.1% and 3.6% higher than those of CK, respectively. The contents of N and P in phloem of mother branches was 39.3%, 35.2% and 48.9% and 31.0%, 28.2% and 14.8% higher than those of CK, respectively. The female cone development and new shoot growth of P. koraiensis consumed a large amount of NSC, N and P. The carbohydrates and mineral nutrients manufactured or stored in the mother branches could not meet the needs of female cone development and new shoot growth, and thus they need to be imported from other tissues.

Responses of polyphenoloxidase and catalase activities of rhizosphere and bulk soils to warming during the growing season in an alpine scrub ecosystem.

MA Zhi-liang, ZHAO Wen-qiang, LIU Mei

2019, 30(11):  3681-3688.  doi:10.13287/j.1001-9332.201911.010

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To understand the effects of climate warming on rhizosphere ecological processes in the alpine scrub ecosystem, the responses of polyphenoloxidase and catalase activities in the rhizosphere and bulk soils to experimental warming (1.3 ℃) were examined during the growing season in a Sibiraea angustata scrub ecosystem on the eastern Qinghai-Tibetan Plateau, China. The results showed that the activities of polyphenoloxidase in rhizosphere and bulk soils in the middle growing season were significantly higher than those in the early or late growing season. The activities of catalase in the bulk soil increased gradually during the growing season, while they showed no seasonal changes in the rhizosphere soil. In the bulk soil, warming significantly increased the activity of polyphenoloxidase by 17.5% in the late growing season and increased that of catalase by 2.2% in the middle growing season, whereas it did not affect soil enzyme activities in early or late growing seasons. In the rhizosphere soil, warming only significantly increased the activities of polyphenoloxidase and catalase by 6.5% and 1.3% in the early growing season. The rhizosphere effect of soil polyphenoloxidase activity was positive throughout the growing season, while there was no obvious rhizosphere effect for soil catalase activity. Furthermore, warming significantly decreased the rhizosphere effect of soil polyphenoloxidase activity by 15.2% during the late growing season. These results indicated that the activities of polyphenoloxidase and catalase activities differed between rhizosphere and bulk soils, with consequences on the rhizosphere soil ecological processes under climate warming in the alpine scrub ecosystem on the eastern Qinghai-Tibetan Plateau.

Characteristics of soil enzyme stoichiometry along an altitude gradient on Qinghai-Tibet Pla-teau alpine meadow, China

HUANG Hai-li, ZONG Ning, HE Nian-peng, TIAN Jing

2019, 30(11):  3689-3696.  doi:10.13287/j.1001-9332.201911.013

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Soil enzymes play critical roles in material cycle and energy flow of ecosystems. Understanding soil enzyme activities is of great significance for exploring ecosystem functions. In this study, we investigated soil enzyme activities, stoichiometry and their driving factors at six different altitudes (4300-5100 m) on Qinghai-Tibet Plateau alpine meadow using Biolog microplate analysis. The results showed that β-1,4-glucosidase (βG) closely related to C cycle, β-1,4-N-acetylglucosaminidase (NAG) and L-leucine aminopeptidase (LAP) closely related to N cycle and the activity of acid phosphatase (AP), which was closely related to P cycle, all exhibited unimodal trends with increasing altitude, with the order of 4800 m>4950 m>4400 m>4650 m>5100 m>4300 m. Soil N:P enzyme activity ratio showed the same trend as soil enzyme activity, and reached the highest value at 4950 m, however, soil C:N and C:P enzyme activities ratios increased along the altitude. Pearson correlation analysis showed that SOC, TN and soil water content were significantly positively correlated with the activities of four types of enzymes. Mean annual precipitation was significantly negatively associated with the activities of NAG and AP. Mean annual precipitation, mean annual temperature, Shannon diversity, vegetation richness, vegetation coverage and TN affected ratios of soil C:P and N:P enzymes. Soil C:N activity ratio correlated with mean annual temperature, mean annual precipitation, vegetation richness, vegetation coverage, SOC and TN. In summary, soil enzyme activities and stoichiometry had remarkable difference along the altitude gradient on Qinghai-Tibet Plateau alpine meadow, with certain N limitation in high altitude areas. Soil water content, TN, SOC, mean annual precipitation and mean annual temperature were key factors driving such differences.

Responses of leaf functional traits of dominant plant species in grassland communities to nitrogen and phosphorus addition in loess hilly-gully region.

YANG Quan, CHEN Zhi-fei, ZHOU Jun-jie, LAI Shuai-bin, JIAN Chun-xia, WANG Zhi, XU Bing-cheng

2019, 30(11):  3697-3706.  doi:10.13287/j.1001-9332.201911.005

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To analyze plant functional traits of dominant species to nitrogen and phosphorus addition, three species (Bothriochloa ischaemum, Stipa bungeana, and Lespedeza davurica) were selected in the loess hilly-gully region. A split-plot experiment which included three N treatments (0, 50, and 100 kg N·hm^-2·a^-1) and three P treatments (0, 40, and 80 kg P₂O₅·hm^-2·a^-1) was conducted. At the fast-growing stage, leaf length, leaf width, specific leaf area, leaf dry matter content, leaf N content, leaf P content, and leaf N:P were measured. Results showed that under 50 and 100 kg N·hm^-2·a^-1 treatments, leaf length and width of B. ischaemum increased significantly by 35.3% and 64.4%, respectively, while only the leaf length of S. bungeana and the leaf width of L. davurica increased significantly by 58.8% and 33.9%, respectively. Leaf dry matter content of the three species decreased significantly by 10.7%, 15.3% and 11.2%, respectively. Leaf N content and N:P of B. ischaemum and S. bungeana increased significantly by 23.0% and 99.2%, 45.8% and 96.9%, respectively, compared with unfertilized treatments. Under 40 and 80 kg P₂O₅·hm^-2·a^-1 treatments, leaf length, leaf width and specific leaf area of L. davurica increased significantly by 56.9%, 41.4% and 19.6%, respectively, while leaf dry matter content decreased significantly by 14.9%. Leaf P content of three species increased significantly by 96.7%, 110.9% and 238.4%, while the N:P decreased significantly by 45.8%, 42.8% and 53.7%, respectively, compared with those under unfertilized. Under 50 kg N·hm^-2·a^-1 treatment, compared with no P application, leaf length and leaf width of L. davurica and leaf P content of the three species significantly increased, and leaf N content of B. ischaemum and S. bungeana decreased significantly at 40 and 80 kg P₂O₅·hm^-2·a^-1 treatments. Under 100 kg N·hm^-2·a^-1 treatment, leaf length of B. ischaemum and S. bungeana, leaf width of L. davurica and leaf P content of three species significantly increased, while leaf N content of B. ischaemum decreased significantly after P application. In summary, functional traits of dominant species showed significant responses to short-term nitrogen and phosphorus addition, with the different responses were mainly related to species traits and fertilization levels. Such difference reflected plant adaptation to habitat changes. The divergent responses of different species to nitrogen and phosphorus addition played an important role in maintaining diversity and stability of grassland communities.

Comparison of ecological characteristics of Carex tussock under natural and artificial reco-very.

QI Qing, LIU Xiao-wei, TONG Shou-zheng, ZHANG Dong-jie, ZHANG Ming-ye, AN Yu, WANG Xue-hong

2019, 30(11):  3707-3715.  doi:10.13287/j.1001-9332.201911.008

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We compared the ecological characteristics of tussock individuals and populations undergoing natural and artificial restoration in Carex tussock wetlands in the Sun Island in Harbin and identified the relationships between the growth of Carex tussock and environmental factors. Results showed that there were obvious seasonal dynamics in morphological characteristics of C. appendiculata. Tussocks grew rapidly from May to June, peaked in June, and then decreased steadily from July to August. There were significant differences in ecological characteristics of Carex tussocks between natural and artificial restorations. The morphological characteristics of individual tussock, including leaf area, leaf width, fresh weight per ramet, dry weight per ramet, and the hummock shape indicators (hummock height, diameter, volume and surface area) in natural restored area were significantly higher than those in artificial transplanting area. For the Carex tussock community, tussock density, coverage and biomass in natural restoration area were significantly lower than those in artificial transplanting area. Soil water content, water depth and hummock spacing in natural restoration area were significantly higher than those in artificial restoration area, which facilitated the formation and development of individual tussock. Higher transplanting density was the main factor leading to higher density, coverage, and biomass in artificial restoration area. Our results suggested that the distribution characteristics of tussocks in natural restoration area should be taken into account in future restoration and protection works. Appropriate adjustment of the distance between hummock (54.22-117.89 cm) and population density (1.9-3.1 ind·m^-2), as well as proper water recharge measures in spring in arid areas to regulate soil water content and water depth, would be conducive to promoting the growth and rapid recovery of Carex tussock, which would maintain the long-term health and stability of tussock wetland.

Fractal dimension characteristics of soil particle size distribution under different vegetation patches in desert steppe and its relationship with soil nutrients

DU Ya-xian, FAN Jin, LI Shi-yao, NIU Yu-bin, YU Hai-long, HUANG Ju-ying

2019, 30(11):  3716-3724.  doi:10.13287/j.1001-9332.201911.004

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Soil samples from four vegetation mini-patches (Artemisia scoparia, Glycyrrhiza uralensis, Sophora alopecuroides, Astragalus melilotoides) in a desert steppe in central Ningxia were collected. Soil physico-chemical properties including soil particle-size distribution, organic matter, pH, EC, total N, total K, total P of three depths were measured. The fractal dimension of particle size distribution characteristics of soils derived from four different vegetation mini-patches and their correlations with soil physico-chemical properties were examined. The results showed that patch vege-tation distribution affected the distribution of soil particle size, with the A. melilotoides mini-patch being the highest (D=2.51) and G. uralensis mini-patch being the lowest (D=2.46). There were significant positive correlation between fractal dimensions and the contents of clay and silt, and nega-tive correlation between fractal dimensions and sand content. Fractal dimensions were positively correlated with pH value and EC, negatively correlated with the contents of soil organic matter and total N, and had no correlation with the contents of soil total K and total P. The patchy vegetation distribution had potential trends of salinization and degradation.

Effects of elevated CO₂ concentration on grain filling capacity and quality of rice grains located at different positions on a panicle.

HU Shao-wu, ZHANG Xin, JING Li-quan, LAI Shang-kun ,WANG Yun-xia, ZHU Jian-guo, WANG Yu-long, YANG Lian-xin

2019, 30(11):  3725-3734.  doi:10.13287/j.1001-9332.201911.022

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The rising atmospheric CO₂ concentration affects spikelets development, grain filling process, and rice quality. However, it is unclear that whether such effects are related to grain positions on rice panicle. By using a rice FACE (Free-Air CO₂ Enrichment) platform, we grew a japoni-ca rice cultivar Wuyunjing 23, characterized with high yield and good quality, under ambient (Ambient) and elevated CO₂ concentrations (+200 μmol·mol^-1, FACE). The effects of increased CO₂ concentration on spikelet density, grain filling capacity, the appearance and eating quality of rice grains were examined and the association of such effects with grain positions on rice panicle were investigated. The results showed that CO₂ enrichment increased grain yield of Wuyunjing 23 by 18.3%. The panicle number per unit land area and filled-grain weight increased by 21.4% and 9.4%, respectively; whereas the number of spikelets per panicle and filled-grain percentage decreased by 9.0% and 2.2%, respectively. The decreased filled-grain percentage of rice grown under FACE treatment was mainly related to the increases of empty-grain percentage in all parts of rice panicle. The decrease of rice spikelets number per panicle by FACE treatment was mainly due to the substantial decrease of surviving spikelets of secondary branches in upper and middle parts of rice panicles instead of other positions. The CO₂-induced changes of filled-grain weight and filled-grain percentage were similar among grains located at different positions on rice panicle. FACE treatment reduced the green grain rate and increased the grain length and width, with the grains at different positions on rice papnicle showing similar responses. FACE significantly increased chalky grain percentage by 59% and chalkiness degree by 55%, with the increases for both parameters following the order of primary branches>secondary branches and upper part>middle part>lower part. FACE treatment slightly increased amylose content while decreased peak viscosity, hot viscosity, breakdown, final viscosity and setback, but most of these effects were nonsignificant. The gelatinization temperature of rice also reduced by 5% under FACE, and the decrease of inferior spikelets was greater than that of superior spikelets. In summary, the yield increase of Wuyunjing 23 under high CO₂ concentration was mainly related to the increases of panicle number and individual grain weight, while the panicle size was reduced. Elevated CO₂ concentration reduced green grain percentage but increased grain chalkiness, and had little effect on cooking and eating quality. The grain positions on rice panicle affected the responses of spikelets development, grain filling capacity and grain quality of rice to elevated CO₂ concentration, but the effects varied across different indices.

Effect of different levels of elevated CO₂ concentration on leaf chlorophyll fluorescence cha-racteristics of Japonica rice

FAN Pei-pei, FENG Fang, LIU Chao, SUN Wen-juan, YU Ling-fei, KE Hao-nan, CHEN Shu-tao, HU Zheng-hua

2019, 30(11):  3735-3744.  doi:10.13287/j.1001-9332.201911.030

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To examine the effects of elevated CO₂ concentrations on chlorophyll fluorescence of rice leaf, a field experiment was conducted with automatic control system of CO₂ concentration in open top-chambers (OTCs). There were three treatments, including atmospheric CO₂ concentration (CK), CK+80 μmol·mol^-1 CO₂ (T₁), and CK+200 μmol·mol^-1 CO₂ (T₂). The fast chlorophyll fluorescence induction dynamic curves of flag leaves were measured using the plant efficiency analyzer at the main growth stages of rice. The results showed that T₁ treatment significantly increased quantum yield for electron transfer (φ_Eo), maximum photochemical efficiency (F_v/F_m), and performance index (PI_ABS), but decreased quantum yield for energy dissipation (φ_Do) at the flowe-ring, milk grain, ripening, and full ripeness stages. The values of φ_Eo, F_v/F_m, and PI_ABS were increased by 7.3%-23.3%, 3.1%-7.1%, and 46.2%-93.0%, respectively. The φ_Do values were decreased by 10.3%-20.5%. T₂ treatment significantly decreased φ_Eo, F_v/F_m, PI_ABS by 68.7%, 41.4%, and 93.4%, respectively, but increased φ_Do by 78.4% at the jointing stage. T₂ treatment significantly increased φ_Eo, F_v/F_m, PI_ABS by 11.6%-19.8%, 4.8%-6.8%, and 53.0%-72.6%, respectively, and decreased φ_Do by 7.7%-19.4% at the flowering, milk grain, and ripening stages. Our results suggested that elevated CO₂ concentration (80, 200 μmol·mol^-1) would promote photosynthetic electron transport of PSⅡ in flag leaves of rice.

Light energy utilization and distribution characteristics of flag leaf ¹³C assimilate in different spike-type wheat varieties and their responses to supplementary irrigation

LU Xiao-lan, YU Zhen-wen, ZHANG Yong-li, SHI Yu

2019, 30(11):  3745-3752.  doi:10.13287/j.1001-9332.201911.025

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To clarify the differences in light energy utilization and distribution characteristics of flag leaf ¹³C assimilate in different spike-type wheat varieties and their responses to supplementary irrigation, we set three water treatments in a field experiment, including no irrigation during growth duration of wheat (W₀), water-saving irrigation (W₁, irrigating at jointing and anthesis of wheat to keep the relative moisture of 0-40 cm soil to 65% and 70%), full irrigation (W₂, irrigating at jointing and anthesis of wheat to keep the relative moisture of 0-40 cm soil to 85% and 90%) with the medium-spike wheat cultivars Jimai 22 and Qingnong 2, large-spike wheat cultivars Shannong 23 and Shannong 30 as test materials. The effects of different water treatments on canopy light energy utilization and ¹³C assimilate distribution characteristics of two spike-type wheat varieties were examined. The results showed that leaf area index, canopy light interception rate, and light energy utilization rate of the two varieties at 2, 11, 20 and 31 days after anthesis were significantly higher than W₀ treatment, but there was no significant change in each index when the irrigation increased to W₂ treatment. The distribution of flag leaf ¹³C assimilates of Jimai 22 and Shannong 23 of W₁ in grain was 159.34 and 171.1 g·hm^-2 higher than W₀, respectively, and the distribution ratio was 6.5% and 6.5%, with no significant difference compared with W₂. The grain yields of both varieties under W₁ were significantly higher than that under W₀, but with no significant difference with W₂. Under water-saving irrigation, the medium-spike cultivars had higher canopy photosynthetically active radiation interception and utilization ability at 2 and 11 days after anthesis and large-spike cultivars at 20 and 31 days after anthesis. The distribution amount and ratio of ¹³C assimilates in the grain of medium-spike variety Jimai 22 flag leaf were 6.8% and 2.7% lower than that of the large-spike variety Shannong 23.

Effects of exogenous 6-BA on the yield of wheat after rice in the Jianghan Plain under diffe-rent shading treatments

LI Liu-long, WEI Ming-mei, LI Xiu, WANG Xiao-yan

2019, 30(11):  3753-3761.  doi:10.13287/j.1001-9332.201911.024

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The long duration of rainy weather in the Jianghan Plain leads to low light stress to wheat during the growing season. We examined the effects of shading at booting stage (S₁) and anthesis (S₂) on grain yield and physiological traits of two main wheat cultivars in Jianghan Plain, Zhengmai 9023 (ZM 9023) and Yangmai 23 (YM 23). 6-BA was sprayed before shading treatment (S₁+6-BA, S₂+6-BA) to explore the mitigation effect of low light stress by 6-BA. The results showed that 45% shading of full solar radiation at booting and anthesis stages significantly reduced grain yield, with greater effect at anthesis than that at the booting stage. Dry matter accumulation of grain during 14-21 days after anthesis was significantly decreased by shading. Shading at both growth stages reduced dry matter accumulation at maturity and changed the proportion of dry matter redistribution in vegetative organs. Consequently, grain yield was more dependent on the storage of photosynthetic assimilates of vegetative organs before anthesis, which resulted in a decline of grain yield in shading treatment. The grain yield of spraying 6-BA before anthesis was significantly greater than that of shading treatment, suggesting exogenous application of 6-BA could delay the senescence of flag leaf, grain filling rate and grain weight to mitigate the negative effect of shading. In addition, spraying 6-BA increased dry matter accumulation in the shading treatment at anthesis, and the translocation of post-anthesis assimilates. Grain weight of S₂+6-BA was higher than that with S₂, which ultimately increased grain yield as compared to the shading treatment. In conclusion, the negative impact of shading on wheat grain yield at anthesis was greater than that at booting stage. The application of exogenous 6-BA before shading at anthesis could mitigate yield loss of the shading treatment.

Root respiration and its temperature sensitivity at various growth stages of winter wheat in the Loess Plateau, Northwest China

ZHANG Yan-jun, DANG Shui-na, GUO Sheng-li

2019, 30(11):  3762-3770.  doi:10.13287/j.1001-9332.201911.029

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Understanding the effects of crop growth stage on root respiration (R_A) and its temperature sensitivity (Q₁₀) has important theoretical and practical significance for enriching the carbon cycle theory of cropland. In a rain-fed agricultural ecosystem on the Loess Plateau, soil respiration rates were in situ measured in adjacent bare soil (soil microbial respiration, R_H) and non-fertilized winter wheat (soil respiration, R_S=R_A+R_H) with an automated CO₂ flux system from 2009 to 2014 to investigate the effect of growth stage on R_A and Q₁₀. The results showed that net photosynthetic rate in the seedling, elongating, filling, and the ripening stage was 5.9, 14.4, 12.0, and 4.4 μmol·m^-2·s^-1, and the corresponding root activity was 51.0, 100.8, 84.4, and 31.8 μg·g^-1·h^-1, respectively. R_A differed significantly among different growth stages, which was 0.26, 0.67, 0.91, and 0.56 μmol·m^-2·s^-1. The variation of R_A was closely related with soil moisture, soil temperature, net photosynthetic rate, and root activity, which presented parabolic, exponential, linear, and linear models respectively. Furthermore, Q₁₀ in each stage was 2.61, 4.88, 2.26, and 6.93, respectively, the variation of which was closely related with net photosynthetic rate, root activity, and soil moisture, with the contribution rate of root respiration being 29%, 53%, 46% and 31%, respectively. In conclusion, in addition to environmental factors, growth period of winter wheat was an important factor affecting R_A and Q₁₀.

Effects of nitrogen application rate on grain filling characteristics and nutritional quality of summer maize.

YU Ning-ning, REN Bai-zhao, ZHAO Bin, LIU Peng, ZHANG Ji-wang

2019, 30(11):  3771-3776.  doi:10.13287/j.1001-9332.201911.021

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Suitable nitrogen application rate can significantly increase grain filling rate and yield and improve nutritional quality. Denghai 518 (DH518) and Zhengdan 958 (ZD958) were used as experimental materials in this study. A field experiment with four treatments, no nitrogen treatment (N₀), decrement nitrogen application rate (N₁, 129 kg N·hm^-2), suitable nitrogen rate (N₂, 184.5 kg N·hm^-2) and excessive nitrogen rate (N₃, 300 kg N·hm^-2), was conducted to explore the effects of nitrogen fertilization on grain filling parameters and nutritional qualities of summer maize. Results showed that grain filling characteristics, grain dry weight, and yield in N₀ treatment was decreased. With increasing nitrogen application rate in the suitable range, average filling rate, grain dry weight, and yield increased. Grain yield of two hybrids in N₁ and N₂ treatments was higher than that of N₀ by 16.4%-57.2% and 35.8%-65.1%, respectively. Grain protein, soluble sugar, starch contents and the ratio of amylopectin and amylase contents were lower and crude fat content was higher in N₀ treatment. Grain protein content, soluble sugar content and starch content in N₂ of DH518 were higher than that of N₀ and N₁ by 32.5% and 6.5%, 19.9% and 9.5%, 8.9% and 5.2%, and the ratio of amylopectin and amylose contents was increased. Grain protein, soluble sugar and starch contents in N₂ of ZD958 were higher than that of N₀ and N₁ by 16.9% and 7.8%, 30.5% and 14.8%, 11.5% and 5.7%, and the ratio of amylopectin and amylase contents was increased. Crude fat content in N₂ of both hybrids decreased significantly by 4.8%-12.3% than that of N₀ and N₁. However, yield and nutritional quality was increased in N₃ treatment than that of N₂. Our results suggested that suitable nitrogen rate could enhance grain filling, grain weight, and grain nutritional quality.

Compensation effect of re-watering after different drought stresses on source-sink metabolism during tuber expansion period of potato.

LIU Yi-jian, REN Jian-hong, YIN Li-na, DENG Xi-ping, KE Qing-bo, WANG Shi-wen

2019, 30(11):  3777-3786.  doi:10.13287/j.1001-9332.201911.023

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The compensation effect of re-watering after drought has been widely reported in various crops during different growth stages. It is considered as an important self-regulation mechanism for plants to resist abiotic stresses and also an efficient utilization of limited water resource. In this study, two rounds of re-watering after drought treatments were carried out during tuber expansion period of potato, to investigate the drought threshold of potato and explore the potential mechanisms of compensation effect with source-sink aspect. We used virus-free plantlets of “Atlantic” potato as experimental materials. Four treatments were included: sufficient water supply (W), re-watering after mild drought (D₁-W), re-watering after medium drought (D₂-W) and re-watering after severe drought (D₃-W). The results showed that potato yield exhibited an over-compensation effect after two rounds of D₁-W treatment, with water use efficiency and yield being increased by 17.5% and 6.3%, respectively, compared with the sufficient water supply. D₂-W treatment had no significant effect on potato yield, but water use efficiency was increased by 8.4%, indicating a near-equivalent compensation effect. On the contrary, D₃-W treatment did not show any compensation effect in yield. In addition, leaf chlorophyll content, net photosynthetic rate, and leaf area were all reduced after drought treatment, indicating a reduction in “source” size and activity. After re-watering, D₁-W and D₂-W treatments showed over-compensation and compensation effects through improving source supply capacity. Meanwhile, re-watering after moderate drought increased the sink activity through significantly enhancing the activities of key enzymes in tubers (sink), thus increased the average weight of tubers. In conclusion, re-watering after moderate drought stress during potato tuber expansion period had compensation and over-compensation effects on both source and sink, and thus could compensate for the drought-induced yield loss and improve water use efficiency.

The effects of sesame/peanut intercropping on photosynthetic fluorescence characteristics in functional leaf of sesame.

WANG Fei, SUN Zeng-guang, JIAO Nian-yuan, XU Yong-hui, CHEN Yue, PING Fei, LYU Meng

2019, 30(11):  3787-3794.  doi:10.13287/j.1001-9332.201911.014

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To unravel functional leaf photosynthetic mechanisms underlying enhanced yield of sesame in sesame/peanut intercropping, a field experiment was carried out in 2017 and 2018 with four treatments including (1) three-row sesame intercropped with six-row peanut (IC 3:6), (2) two-row sesame intercropped with four-row peanut (IC 2:4), (3) sole cropped sesame (SS), and (4) sole cropped peanut (SP). We measured the parameters of gas exchange, characteristics of photosynthetic response curve to light and CO₂, and characteristics of chlorophyll rapid fluorescence induction kinetic curves of the functional leaves of sesame. The results showed that the partial land equivalent ratio of intercropped sesame was greater than 1/3. The light saturation point (I_sat), maxi-mum net photosynthetic rate (P_{n max}), maximum electron transport rate (J_max), triose phosphate utilization rate (TPU), maximum carboxylation rate of Rubisco (V_{c max}) were increased significantly under intercropping. Further, absorption energy flux per CS (ABS/CS_o), trapping energy flux per CS (TR_o/CS_o), number of active reaction centers per CS (RC/CS_m), and electron transport flux per CS (ET_o/CS_o) in intercropped treatments were enhanced compared to that under sesame monoculture. However, the ratio between variable fluorescence F_k to amplitude F_j-F_o (W_k) and ratio between variable fluorescence F_j to amplitude F_p-F_o (V_j) in functional leaves of intercropped sesame were significantly decreased. The efficiency of converting light energy into electricity of PSⅡ reaction center (Ψ_o), electron transfer efficiency from PSⅡ to end acceptor of PSⅠ (Ψ_Ro), electron transfer efficiency of the electron transport chain (δ_R), PSⅠ photochemical activity, and the coordination between PSⅡ and PSⅠ in functional leaves of intercropped sesame were increased. The net photosynthetic rate (P_n), stomatal conductance (g_s), transpiration rate (T_r), P_{n max}, J_max, V_{c max}, TPU, Ψ_o, Ψ_Ro and δ_R were significantly higher in IC 3:6 than those in IC 2:4. We conclude that intercropping improves net photosynthetic rate and yield of sesame by increasing light absorption, electronic transmission, activity of PSⅡ donator/receptor sides, and CO₂ fixation, with stronger effects in IC 3:6 than IC 2:4.

Effects of environmental stresses on soil functional stability under different water management measures in a paddy field

JIN Miao-miao, HU Zheng-kun, ZHU Bai-jing, LIU Man-qiang, JIAO Jia-guo, LI Hui-xin, CHEN Xiao-yun, HU Feng

2019, 30(11):  3795-3803.  doi:10.13287/j.1001-9332.201911.028

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With the increase of global environmental changes and intensive anthropogenic activities, it is important to maintain and improve soil function. Here, we evaluated the effects of environmental stress (i.e., drying, high temperature and the combination of drying and high temperature) on soil functional stability (resistance and resilience) under three kinds of water management mea-sures, which included conventional-flooded cultivation, non-flooded with uncovered cultivation and non-flooded with straw mulching. Results showed that, compared to single environmental stress (drying or high temperature), combined stress led to lower soil fungal biomass, bacterial biomass, basal respiration, and soil functional resistance, and higher contents of dissolved organic carbon (DOC) and NH₄⁺-N after one day treatment of stress. Combined stress significantly decreased soil functional resilience after 56 days treatment of stress. Results from the correlation analysis showed that bacterial and fungal biomass were significantly related to soil resistance and resilience. Different water management measures could regulate the effects of environmental stress on soil functional stability. Non-flooded with straw mulching treatment significantly increased the contents of soil DOC, NH₄⁺-N, fungal biomass and bacterial biomass, resulting in higher soil functional resistance and resilience compared with conventional-flooded cultivation and non-flooded with uncovered cultivation under both single and combined stress. In summary, non-flooded with straw mulching could improve soil functional stability under environmental stress, and it could be a suitable agricultural management for non-continuously flooded rice cultivation under multiple stresses.

Effects of the blended nitrogen fertilizers combined with inhibitors on soil nitrogen pools.

BAI Yang, YANG Ming, CHEN Song-ling, ZHU Xiao-qing, JIANG Yi-fei, ZOU Hong-tao, ZHANG Yu-long

2019, 30(11):  3804-3810.  doi:10.13287/j.1001-9332.201911.027

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Pot experiment with winter wheat was conducted to investigate the effects of blended nitrogen (N) fertilizer (slow-release fertilizer-N:urea-N=1:1) combined with N fertilizer inhibitor NAM on soil ammonium (NH₄⁺-N), nitrate (NO₃^--N), microbial biomass nitrogen (MBN) and fixed-ammonium (FN) contents. We analyzed dynamic characteristics of soil mineral N, MBN, FN pools under different treatments. There were six treatments, including no N fertilizer (CK), conventional urea (U), blended N fertilizer (MU), MU plus 2.5‰ NAM (MUN₁), MU plus 5‰ NAM (MUN₂), and MU plus 7.5‰ NAM (MUN₃). Our results showed that, compared to that of MU treatment, MUN₂ and MUN₃ delayed the appearance time of NH₄⁺-N peak. Averaged across the whole wheat growing period, soil mineral N content for NAM treatments decreased by 5.3%-11.7%. From tillering to maturity stage, MBN mineralization and mineralization rates were 38.96 mg·kg^-1 and 91.5%, which was higher than that of U treatment; MBN mineralization and mineralization rates for MUN₁, MUN₂ and MUN₃ treatments were 58.73 mg·kg^-1, 83.3%, 94.20 mg·kg^-1, 94.6%, 104.46 mg·kg^-1 and 96.3%, respectively. The FA mineralization release for NAM treatments were higher by 2.83-9.19 mg·kg^-1 than that of MU treatment. The results of path analysis showed that NAM addition weakened the direct effect of soil NH₄⁺-N pool on NO₃^--N pool but enhanced the indirect effects of FN pool on NO₃^--N pool through affecting NH₄⁺-N pool. The wheat grain yields of the MUN₁, MUN₂ and MUN₃ treatments were significantly higher by 31.6%, 21.5% and 22.9% than that of MU treatment. Nitrogen use efficiencies were increased by 8.1%, 13.5% and 3.1%, respectively. In summary, through double regulation for N release and transformation in soil, NAM delayed the appearance time of soil NH₄⁺-N peak and retarded its transformation into NO₃^--N, and increased the roles of MBN and FN in supplying N, thereby increased crop yield and N-fertilizer use efficiency.

Ground diameter-height models of naturally regenerated seedlings and saplings under broad-leaved mixed forest in Maoershan Mountains.

WANG Jia-hui, DONG Li-hu, LI Feng-ri

2019, 30(11):  3811-3823.  doi:10.13287/j.1001-9332.201911.003

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Based on the investigation data of seedlings and saplings from 48 plots in natural broad-leaved forest of Maoershan Experimental Forest Farm of Northeast Forestry University in Heilongjiang Province, the optimum model of ground diameter (D₀) - height (H) was selected from eight alternative models as the basic model for the main regeneration tree species, and then the stand factors were parameterized, and the mixed effect model of sampling plot level was developed. The basic model and the mixed effect model were tested by independent samples. The results showed that there was a significant positive correlation between ground diameter and tree height of seedlings and saplings and that power function or model containing power function could better fit the relationship. The introduction of stand factors [dominant height of forest (H_T), average diameter at breast height (D_g), basal area of forest (BA)] could improve the fitting effect of the model, with the residual root mean square error (RMSE) of each tree species decreasing by 1.3%-7.4% (average 3.8%), adjusted coefficient of determination (R_a²) only increasing by 0.1%-1.1% (average 0.6%) and Akaike info criterion (AIC) decreasing by 3.2%-35.2% (average 11.4%). Mixed effect models were developed for 10 tree species, such as Ulmus propinqua, Tilia and Fraxinus mandshurica. The R_a² of mixed effect models was larger than that of the basic model, with an enhancement of 0.5%-3.5% (average 2.2%). RMSE and AIC decreased by 3.9%-20.3% (ave-rage 13.9%) and 4.0%-44.4% (average 22.3%) than that of the basic model. Model test results showed that, compared with the basic model, the average absolute error (MAE) of mixed effect model was reduced by 0.0001-0.46 m, with an average reduction of 0.08 m, and the average prediction error percentage (MPSE) decreased by 0.1%-6.2%, with an average reduction of 2.0%. The mixed effect model could improve the fitting effect and prediction ability of the model. The ground diameter-height model of seedlings and samplings of main regeneration species in broad-leaved mixed forest was developed in this study, which provides a reference for structure analysis and stand growth prediction of natural broad-leaved forest.

Spatial structure optimization simulation of main forest types in Great Xing’an Mountains, Northeast China

WEI Hong-yang, DONG Ling-bo, LIU Zhao-gang

2019, 30(11):  3824-3832.  doi:10.13287/j.1001-9332.201911.019

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Based on the data from four 1 hm² permanent plots in main forest types [namely natural Larix gmelinii forest (LF), natural Betula platyphylla forest (BF), coniferous-broadleaved mixed forest (CBMF) and coniferous mixed forest (CMF)] in Great Xing’an Mountains, a comprehensive cutting index of individual tree (T), based on the commonly used spatial structure parameters [i.e., mingling (M), neighborhood comparison (U), uniform angle index (W), and competition index (CI)] and non-spatial structure parameters [tree vigor index (DC), tree stability index (DH)], was constructed using combined AHP and entropy evaluation method. The cutting process was simulated by Excel VBA to determine the best tending intensity on the basis of systematic comparison of comprehensive T-value under different tending intensities (10%, 20%, and 30%) of different forest types. The results showed that, in the initial state, the mean values of W were all 0.57, indicating a typical cluster distribution. The mean values of U ranged from 0.50 to 0.51 and the dominant degree of overall growth of trees was in a typical mean state. The mixed degree of four main forest types was generally low, with the mixed forest being obviously higher than the pure forest. The mean competition index within the stand was above 2.0, indicating higher competition pressure. The stability and growth vigor index of LF were significantly higher than those of other stands. Overall, the management urgency of BF was significantly higher than that of other stands. With regard to T-value growth rate between adjacent tending intensities, the optimal cutting intensity was 30% for LF forest and 10% for other types. The relative growth rates were 9.7%, 7.9%, 6.6% and 3.9% respectively. However, from the perspective of T-value and canopy density with different tending intensities, the optimal cutting intensity of BF was 20%, and the others were all 30%, in which the T-values were increased by 28.9%, 16.4%, 17.5% and 9.2% respectively. After simulated harvesting, stand structure was improved in various degrees and the mixed degree of tree species was increased. The horizontal distribution pattern of stand tended to random distribution. The dominance degree of dominant tree species was increased. The competition pressure of trees was decreased. DC of trees was slightly lower and the DH of trees was improved.

Prediction of potential distribution of Carpinus cordata in China under climate change.

ZHAO Ru-nan, HE Qian-qian, CHU Xiao-jie, LU Zhi-qiang, ZHU Zun-ling

2019, 30(11):  3833-3843.  doi:10.13287/j.1001-9332.201911.020

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Climate change seriously affects the geographical distribution of plants. Regional diffe-rences in plant response to climate change will provide important guidance for species introduction and conservation. Based on ArcGIS and MaxEnt model, we used 176 geographic information of Carpinus cordata and 13 climatic variables to reconstruct its current and future niche. The results showed that the model had a high credibility in simulating contemporary potential distribution areas. The AUC values of the test set and the training set of the model were 0.973 and 0.957, respectively. The main core suitable areas were concentrated in Qinling, Changbai Mountain and their adjacent areas, with other sporadic “island” distribution. C. cordata is not distributed in Guizhou, Jiangxi, Yunnan and Fujian, but the model predicted some suitable distribution areas in those provinces. With climate warming in the future, ecologically suitable areas of C. cordata would increase significantly, mainly as “shrinking to high altitude areas”, “expanding northward”, and “expanding eastward”. However, core suitable areas would be slightly reduced, which would be manifested as “shrinking southward”, “moderate stability”, and “expanding northward”. The response of C. cordata distribution to climate warming was obviously regional. Eastern Jiangsu, Anhui, and other places would become ecologically suitable areas for C. cordata because of their unique geographical location and climatic environment. The lower latitudes of the south, the original low-altitude areas might no longer be suitable for survival. The central Qinling region was a transition region from north to south, with strong buffer capacity, and climate warming had little effect on its distribution area. The Changbai Mountain and its adjacent areas at higher latitudes were more suitable for C. cordata.

Differences in atmospheric CO₂ concentration and δ¹³C value between green spaces and its adjacent roads as well as the influencing factors in Beijing, China.

SUN Shou-jia, LEI Shuai, QIU Lan-fen, LI Chun-you, SHU Jian-hua

2019, 30(11):  3844-3854.  doi:10.13287/j.1001-9332.201911.026

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Near-surface atmospheric CO₂ concentration and δ¹³C value in four greenspaces and on their adjacent roads in Beijing were measured by off-axis integrated cavity output spectroscopy to analyze the influence of urban greenspace on spatial distribution of near-surface atmospheric CO₂. The results showed that atmospheric CO₂ concentration and δ¹³C value varied substantially both temporally and spatially. The highest CO₂ concentration was found in the urban area, followed by the suburbs, and the lowest CO₂ concentration was in the outer suburbs. There was a clear near-surface atmospheric CO₂ dome, but a reverse pattern for δ¹³C value. During the non-growing season, the ΔCO₂ and Δ¹³C between greenspace and adjacent roads were low. The differences among the four experimental sites were not significant. In the growing season, the ΔCO₂ and Δ¹³C at the BLA&4^th RR (Beijing Institute of Landscape Architecture and 4^th Ring Road) and BOP&5^th RR (Beijing Olympic Forest Park and 5^th Ring Road) in urban areas were significantly higher than those at DP&SR (Daoxianghu Park and Sujiatuo Road) and MTG&MR (Mentougou forest experimental station and an adjacent road) in the suburbs. During the growing and non-growing seasons, CO₂ concentration of all examined sites was significantly positively related with the traffic volume, indicating that traffic volume was an important factor affecting the spatial distribution of CO₂. The δ¹³C value was significantly negatively related with traffic volume during non-growing season, but no significant relationship was found during the growing season. The ΔCO₂ concentration between the four green-spaces and their adjacent roads were significantly negatively related with leaf area index (LAI). The Δ¹³C value were significantly logarithmically related to LAI. Results from stepwise regression showed that solar radiation, temperature, and LAI significantly affected ΔCO₂ in urban areas and suburbs during the growing season, and that temperature and solar radiation were the major driving factors for Δ¹³C. During the growing season, plants in the greenspaces assimilated CO₂ via photosynthesis and thus reduced the near-surface atmospheric CO₂ concentration. Our results indicate that green-spaces play a positive role in improving ecological environment in urban areas.

Influence of greenspace landscape pattern on PM_2.5 in the center urban area of Nanchang, China

LI Qi, CHEN Wen-bo, ZHENG Jiao, XIE Tao, LU Tao-jie

2019, 30(11):  3855-3862.  doi:10.13287/j.1001-9332.201911.018

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With rapid urbanization and industrialization, more attention has been paid to atmosphere quality in China. PM_2.5, an important atmospheric pollutant, has attracted widespread public attention. Urban greenspace as a semi-natural surface landscape can affect the concentration and distribution of PM_2.5. Current studies mainly focus on micro-scale, with few on landscape scale. In this study, land use regression (LUR) model was used to densify monitoring points. Based on ordinary Kriging interpolation method, the spatial distribution of PM_2.5 concentration was simulated with high precision. We quantitatively analyzed the impacts of urban greenspace landscape characteristics and quality on PM_2.5 concentration by coupling urban greenspace interpreted by remote sensing. The results showed that PM_2.5 concentration decreased from central area to periphery. The impacts of greenspace on PM_2.5 concentration varied with greenspace types. The shape of greenspace had no effect on PM_2.5 concentration, while the area and quality of greenspace were significantly negatively correlated with PM_2.5 concentration. In general, the greenspace had an obvious PM_2.5 reduction effect in the distance of less than 100 m. Within the reduction distance, the closer to the greenspace, the lower the PM_2.5 concentration was. The reduction distance of the affiliated and park greenspace was larger than other greenspace types.

Geo-informatic spectrum analysis of land use change in the Manas River Basin, China during 1975-2015.

YANG Ai-min, ZHU Lei, CHEN Shu-huang, JIN Han, XIA Xin-xin

2019, 30(11):  3863-3874.  doi:10.13287/j.1001-9332.201911.017

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Geo-informatic spectrum analysis method was used to understand the complex geogra-phical phenomena concisely in graphic language. It is important for the integration research on spatial pattern and temporal process of land use change over multiple temporal and space scales. Based on remote sensing images in 1975, 1990, 1995, 2000, 2005, 2010 and 2015, we built the geo-spectrum of land use/cover change (LUCC) and quantitatively analyzed both the process and rend of LUCC in Manas River Basin. Results showed that the range of land use change in this basin was gradually decreasing, and land use structure tended to be simplistic, then tended to stable in later stage during 1975-1990. At the same period, the area of grassland increased greatly, which was mainly derived from unused land. The area of cultivated land expanded from 1990 to 2015, which mainly converted from unused land, forestland, and grassland. The geo-spectrum of land use change model showed that prophase change type, anaphase change type and continuous change type accounted for 1.3% of the total basin area. The overall characteristics of geo-spectrum unit were dominated by unused land converted to cultivated land, forestland and grassland. The land use change process was relatively stable. The Manas River Basin was covered 61.2% by region with comparatively stable spatial pattern. The most frequent way of land use change was increasingly expanding of cultivated land, which was displayed as: Liumaowan Bay Town of Shawan County and Liuhudi Town of Manas County were the center, then expanded to the two sides and spread to the Gurbantunggut Desert. The construct geo-spectrum of LUCC enriched the LUCC spatial-temporal analysis method system and provided an effective approach for the future research of LUCC under multiple temporal and spatial scales.

Evaluation of ecosystem services of the Thousand-Island Lake, Zhejiang, China.

XIANG Chen, YAN Li-jiao, HAN Yi-cai, WU Zi-xu, YANG Wen-jie

2019, 30(11):  3875-3884.  doi:10.13287/j.1001-9332.201911.031

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We quantitatively evaluated Thousand-Island Lake’s aquatic ecosystem service value and analyzed its developing trend at the whole lake scale. We built an index system to evaluate the ecosystem service of Thousand-Island Lake, which included 16 indicators of 10 categories. The results showed that the total value of ecosystem services of Thousand-Island Lake was 49.3 billion and 57.2 billion yuan in 2007 and 2017, respectively. The highest value of Thousand-Island Lake’s ecosystem service was its regulating function, which played an absolutely dominant role. Ranked according to their values, different functions of the final ecosystem services were in a descending order of floodwater regulation, surface water regulation, carbon sequestration (reduction), oxygen generation, tourism, water purification, fishing, energy saving through water source heat pump, water for hydropower, agriculture, forestry and animal husbandry uses of water resources, ecological and public use of water resources, water source for industrial use, volume of freight transportation, water source for city resident use, water circulation cooling, and passenger transportation. Thousand-Island Lake provided a total ecosystem services value of 86.0 million and 99.8 million yuan·km^-2, which was 47.6 and 17.3 times as the GDP per area in Chun’an County in 2007 and 2017.

Impacts of Shenzhen basic ecological control line on landscape ecological risk

CHEN Bi-kai, ZHAO Yu-hao, WU Jian-sheng

2019, 30(11):  3885-3893.  doi:10.13287/j.1001-9332.201911.015

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The Shenzhen Basic Ecological Control Line (SZBECL) has been in operation for more than ten years since its implementation in 2005, which has a significant protective effect on the ecological space. Landscape ecological risk refers to the possible adverse consequences caused by the natural or human-induced interactions between landscape pattern and ecological processes. The scien-tific management of ecological risk is an important prerequisite for the sustainable development of human beings. Therefore, it is of great significance to explore the changes of landscape ecological risk inside and outside the SZBECL. Combining two indicators (ecological sensitivity and landscape vulnerability), we comprehensively evaluated the landscape ecological risk of Shenzhen in 2005 and 2015. The difference-in-difference method was used to explore the impacts of the SZBECL on the landscape ecological risk inside the line. Results showed that the landscape ecological risk in Shen-zhen presented a spatial structure of “high west and low east”, which decreased by 13.5% during 2005 to 2015. Inside and outside the SZBECL, the declines of the landscape ecological risk were 0.7% and 14.4%, respectively. For the five subzones, declines were more significant outside the SZBECL, except for the eastern coastal zone. After controlling the effects of other variables, at the municipal level, there was 1.8% higher landscape ecological risk inside the line compared with the region outside the line. Furthermore, at the subzone level, there was 1.6%, 1.6%, 1.4%, and 1.9% higher landscape ecological risk inside the line in the central urban zone, the western coastal zone, the middle zone, and the eastern zone, respectively. There was no significant difference between the inside and outside of the line in the eastern coastal zone. With the implementation of SZBECL, habitat quality and landscape vulnerability inside the line were lowered, but NDVI and population density did not change.

Screening, identification and characterization of a broad-spectrum antagonistic strain in banyan rhizosphere soil

LI Jian, LI Xiao-he, HOU Wen, ZHENG Shen, ZHU Xiang-dong

2019, 30(11):  3894-3902.  doi:10.13287/j.1001-9332.201911.037

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Rhizosphere soil samples were collected from an ancient banyan tree grown in the Wanli period of Ming Dynasty in Ji’an City, Jiangxi Province. Twenty-three kinds of indicator bacteria were used to screen soil actinomycetes by cylinder-plate method and mycelium growth rate method. A broad-spectrum antagonistic strain AHF-20 with stable passage was obtained. According to the morphological observation, physiological and biochemical tests, and molecular biological identification, the antagonistic strain was identified as Streptomyces. We examined the antibacterial active substance of the strain. The results showed that the fermentation products of Streptomyces AHF-20 had antagonistic effects on all the 23 test indicator bacteria. The antibacterial ability was stable, tolerant to temperature, light, ultraviolet, acid and alkali. Antibacterial activity still existed after heating at 121 ℃ for 20 min. The fermentation product was extracted with n-butanol according to the polarity of the active substance. The obtained crude n-butanol extract was diluted to 1 μg·mL^-1, which still had inhibitory effect for Escherichia coli. The results indicated that it has well utilization potential for biocontrol and developing new microbial drug.

Effects of nitrogen and phosphorus inputs on soil nematode community in a degraded grassland.

ZHANG Zhi-wei, HU Yan-yu, WEI Hai-wei, HOU Shuang-li, YIN Jiang-xia, LU Xiao-tao

2019, 30(11):  3903-3910.  doi:10.13287/j.1001-9332.201911.038

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Nematodes, occupying multiple trophic levels in the food web, play important roles in energy flow and nutrient cycling. Most of Chinese natural grasslands have been degraded due to long-term unreasonable utilization, such as over-grazing. External nutrient input is an important way to restore the ecological function of degraded grasslands. The main and intertative effects of nitrogen and phosphorus inputs on soil nematode abundance, trophic group composition and community structure were studied in the grasslands in Xilingol League of Inner Mongolia. Totally, 38 genera of nematodes were recorded. Tylencholaimus, Aphelenchoides, Thonus, and Scutylenchus were dominant genera in this degraded grassland. Nitrogen input decreased total abundances of soil nematodes, and that of omnivores-carnivorous nematodes and plant-feeding nematodes. Phosphorus input increased total abundances of soil nematodes, and that of fungal-feeding nematodes, omnivores-carnivorous nematodes, and plant-feeding nematodes. Nitrogen input inhibited the positive effects of phosphorus input on the abundances of total nematodes, omnivores-carnivorous nematodes and plant-feeding nematodes. Nutrient inputs had no effect on nematode diversity, which would be resulted from the stable plant community. Nitrogen input significantly increased nematode maturity index, decreased plant parasitic nematode maturity index (PPI), and greatly alleviated the negative effects of phosphorus input on PPI and Wasilewska index, indicating that nitrogen input could improve soil health condition and the stability of nematodes community. Our results would help improve our understanding of the effects of nutrient inputs on degraded grassland ecosystem from a soil biotic perspective.

Spatial niche and differentiation of major nekton species in Yueqing Bay, Zhejiang, China

ZHANG Lin-lin, JIANG Ri-jin, YIN Rui, XU Kai-da, FANG Fang, XU Yi-ping, KE Ai-ying

2019, 30(11):  3911-3920.  doi:10.13287/j.1001-9332.201911.039

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The index of relative importance (IRI), niche breadth, and niche overlap (Q_ik) of nekton species were calculated using data collected from four fishery resource surveys from May 2016 to February 2017 in Yueqing Bay, Zhejiang Province. The results showed that there were 27 major nekton species (IRI>100) with higher turnover rates across different seasons, while their niche breadth values differed greatly and showed significant positive correlation with IRI. The niche overlaps of nekton were generally low, with the highest overlap value in autumn and the lowest in spring. The total amount of species pairs with niche overlap over 0.6 (Q_ik>0.6) were 14 in the autumn and five in the spring, which represented 15.4% and 7.6% of the total pairs, respectively. Results from the redundancy analysis suggested that the distribution of main nekton species were mainly affected by temperature, salinity and turbidity, which cause ecological differentiation of nekton species.

Distribution characteristics and model establishment of microorganisms in electrokinetic remediation of organic contaminated soil.

LU Wen-jie, GUO Shu-hai, CHENG Feng-lian, LI Yu-hua, WANG Sa, WU Bo

2019, 30(11):  3921-3930.  doi:10.13287/j.1001-9332.201911.033

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Soil microorganisms would reproduce rapidly and migrate directionally under the applied electric field. In this study, tetradecane-degrading bacteria were added at different locations in soil, and 1 V·cm^-1 unidirectional DC electric field was applied to investigate the migration, distribution, and degradation characteristics of target bacteria in soil. The results showed that microorga-nisms migrated to the cathode and anode by electrodialysis and electrophoresis, respectively. The number of microorganisms migrated by electrodialysis was 3.5 times of that by electrophoresis. The application of electric field could make the soil environment spatially heterogeneous to affect the growth of microorganisms. The average number of soil microorganisms under electric field was 1.16×10⁸ CFU·g^-1(6 days), which was 2.3 times of that without electric field. S₂ to S₄ were the efficient growth areas of microorganisms, with the average number after 30-day electric treatment being 2.8-3.5 times of that on the anode and cathode, and 2.1 times of that in the control. There was a significant positive correlation between the tetradecane degradation rate and the number of microorganisms (r=0.895, P<0.05). The optimal tetradecane degradation region was near the cathode (S₄), where its degradation rate reached 94.6%. Based on these results, a model modified by environmental factors was established to simulate the spatial distribution of microorganisms under the combined effect of electrokinetic stimulation and transportation. According to the model, the number distribution of microorganisms could be deduced when exogenous bacteria were added in a fixed section. The results provide a theoretical basis for the efficient import of exogenous functional bacteria in electrokinetic-bioremediation of organic contaminated soil.

Responses of ground-active arthropod community in Caragana shrub plantations to grazing management in desertified region.

ZHANG An-ning, CHANG Hai-tao, CHEN Wei, LIU Ren-tao

2019, 30(11):  3931-3941.  doi:10.13287/j.1001-9332.201911.032

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We investigated the community structure of ground-active arthropods as well as vegetation and soil properties in Caragana shrub plantations under grazing and exclosure management across spring, summer and autumn in Yanchi County of Ningxia in northern China. The aim of this study was to uncover the responses of ground-active arthropods in shrub plantations to grazing management in desertified regions. The results showed that: 1) plant height, soil fine sand content, and soil electrical conductivity were significantly lower, whereas soil bulk density and coarse sand were significantly higher in shrub plantations under grazing than exclosure. 2) There were 40 families from 13 orders captured. The dominant groups included Formicidae and Tenebrionidae families, which comprised 68.75% of the total individuals. There were four common groups occupying 20.82% of the total individuals. The remaining 34 groups were relatively rare, only accounting for 10.44% of the total. Across the three seasons, the composition of ground-active arthropod community was significantly different between grazing and exclosure, which indicates the sensitivity and adaptability of ground-active arthropods to environmental changes including grazing management and seasonal changes. 3) There was a significant effect of grazing on total abundance of ground-active arthropods in shrub plantations, with significantly higher values under grazing than under exclosure. There was no significant effect of grazing management on group richness and diversity of ground-active arthropods in shrub plantations. 4) There was a correlation of total abundance, evenness index and the Simpson index with plant abundance, vegetation height, soil moisture, soil pH and electrical conductivity. There was a significant correlation of the Shannon index with vegetation height, soil moisture and soil fine sand. Plant density, and soil pH, soil moisture and soil temperature were the key factors driving the structure of ground-active arthropod communities in shrub plantations under gra-zing management across seasons based on the partial RDA results. It was concluded that the variations of plant height, soil pH, soil moisture and soil temperature under grazing management could result in different ground-active arthropod taxon to changing habitats. The conservation effect of shrub on ground-active arthropod could reduce the negative impacts of grazing. Spring grazing could enhance ground-active arthropod abundances in shrub plantations. It was necessary to pay attention to prevention of insects which are caused by spring grazing in shrub plantations.

Niches and interspecific association of dominant shrimp species in the offshore waters of southern Zhejiang Province, China

DING Peng-peng, GAO Chun-xia, PENG Xin, TIAN Si-quan, GOU Xin

2019, 30(11):  3942-3950.  doi:10.13287/j.1001-9332.201911.035

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Based on data from November of 2015 (autumn), February (winter), May (spring), and August (summer) of 2016 in the offshore waters of southern Zhejiang Province, the relationships between major shrimps species were examined by niche breadth, niche overlap, variance ratio, chi-square test, association coefficient and species pair co-occurrence percentage. The results showed that temporal niche breadth of Atypopenaeus stenodactylu was the largest, spatial niche breadth of Solenocera crassicornis was the largest, and A. stenodactylu had the largest spatio-temporal niche breadth. The temporal niche overlap between Parapenaeus fissuroides and Parapenaeopsis tenella was the highest. The spatial niche overlap between Solenocera koelbeli and Penaeus chinensis, P. fissuroides and Heterocarpoides laevicarina were the highest. The spatio-temporal niche overlap between S. koelbeli and P. chinensis was the highest. The analysis of variance ratio showed that the main shrimp species were significantly positively correlated. Positive correlation existed in 13 pairs (χ²≥3.841). Results from the association coefficient (AC) and co-occurrence percentage (PC) indicated that the interspecific association tended to be positive. Our results provide supports for exploring niche breadth and niche overlap of major shrimp species and improving niche differentiation.

Reviews

Research progress of root exudates collection technology

GUO Wan-ji, ZHANG Zi-liang, LIU Qing, YIN Hua-jun

2019, 30(11):  3951-3962.  doi:10.13287/j.1001-9332.201911.040

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Root exudates play an important role in mediating the exchange of substrates, energy and information within the rhizosphere in terrestrial ecosystems. Constructing accurate and applicable sampling system of root exudates to precisely collect the characters including the component and concentration of root exudates and their responses to changing environments are a critical link and prerequisite to understand ecological processes and information exchanges across the root-soil interface. While both traditional and novel techniques for collecting root exudates aim to explore the diversity and concentration of root exudates, current exudate-collection methods could hardly avoid the damage of root system, the adsorption and release of root exudates by soil particles, and distur-bance from microbial metabolism, largely because plant roots are highly associated with the surrounding substrates and environments supporting their growth. Therefore, all root exudate collection methods have their own merits and shortcomings. We systematically reviewed the widely-used traditional and novel root exudates collection techniques and compared their advantages and disadvantages. Furthermore, considering the significance and authenticity of field study on the rhizosphere ecological processes in forest ecosystems, we proposed three frontier research directions regarding the construction of techniques for collecting root exudates in forest ecosystems according to the limits of current studies, aiming to provide foundation for related studies in the future.

Research and application progresses on rice water quality (RICEWQ)model.

HE Wen-yan, MAO Meng

2019, 30(11):  3963-3970.  doi:10.13287/j.1001-9332.201911.016

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Rice production presents a unique environmental condition, with the diseases, insects and weeds being serious during production process. Many kinds of pesticides are used with high frequency. Some pesticides will leach into surrounding water, which shows a high risk for pollution. With the increasing costs of pesticide monitoring and field experiments, mathematical models have become an indispensable part during the process of pesticide registration. As the most reliable and widely used model for pesticide exposure assessment in European paddy fields, rice water quality (RICEWQ) model was mainly used to predict pesticide concentrations in flooded paddy fields and water, and had been preliminarily applied in China. In this review, system structure, the main processes of pesticide fate involved, input and output of RICEWQ model were briefly introduced, and the research progress at home and abroad were summarized. This review would promote the application of RICEWQ model in China and provide reference for related research.

Research advances in species diversity of arbuscular mycorrhizal fungi in terrestrial agro-ecosystem

YANG Wen-ying, SUN Lu-ying, SONG Feng-bin, YANG Xiao-qin, ZHANG Meng-jie, LI Shu-xin, ZHU Xian-can

2019, 30(11):  3971-3979.  doi:10.13287/j.1001-9332.201911.036

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Arbuscular mycorrhizal fungi (AMF) are ancient and ubiquitous soil microorganisms, which can form mutually beneficial association with most terrestrial plants. Within the symbiotic relationship, AMF helps their host plants to absorb nutrients such as nitrogen and phosphorus while obtains carbon from the hosts. AMF plays an important role in agricultural ecosystem, including promoting plant growth, improving crop quality, increasing plant stress resistance, stabilizing soil structure, keeping ecological balance, and maintaining a sustainable agricultural development. We summarized the research advances of AMF in terrestrial agro-ecosystem in recent years, by focusing on AMF species diversity, spatial and temporal distribution, and influence factors of AMF biodiversity in terrestrial agro-ecosystem of China. Further research works were also prospected.

Research progress on the bioweathering and controlling of stone cultural relics

ZHANG Yong, WU Fa-si, SU Min, HE Dong-peng, MA Wen-xia, WANG Wan-fu, FENG Hu-yuan

2019, 30(11):  3980-3990.  doi:10.13287/j.1001-9332.201911.034

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The bioweathering of stone cultural relics is a ubiquitous problem. Weathering prevention is an escalating challenge under the increasing global climate and environmental changes. Here, the mechanisms of lichen-microorganism mediated weathering of stone materials and their relationships with climatic and environmental factors were reviewed. The biological protection of lichens and the evaluation of the efficacy of biocides in lichen-control were discussed. The potential research directions in this field were proposed. Research on lichen-rock interfaces suggested that biological weathe-ring could be mainly attributed to physical and chemical weathering which represented by mycelium penetration and calcium oxalate formation. Bioweathering of outdoor stone cultural relics is closely related with the whole ecosystem encompassing factors, such as stone matrix, surrounding environment, and climate factors. Lichens have both biological weathering and protection effects on stone heritage. For the restoration of bioweathered stone cultural relics, environmental conditions for pre-servation of stone cultural relics should be improved step by step. The related industry regulations and national standards for evaluating biological weathering and control efficiency should be established to promote the efficient development of scientific protection.

Research progress on application of landscape ecology in landscape architecture.

CHANG Qing, SU Wang-xin, WANG Hong

2019, 30(11):  3991-4002.  doi:10.13287/j.1001-9332.201911.009

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As one of the three basic theories of landscape architecture in China, landscape ecology provides a powerful tool for leading landscape architecture in the way from experience- to evidence-based. By systematically reviewing literatures, we explored the advantages and necessity of applying landscape ecology theories and methods in landscape architecture, and summarized the interdisciplinary research hotspot and progress, including research subject, scientific foundation of planning or design, and the landscape performance for improving human wellbeing. We proposed the prior topics on the combination of landscape ecology and landscape architecture to meet the needs of planning and design in practice, including studying the landscape connotation and classification system to serve the multi-disciplinary and multi-sectors, evaluating landscape performance and quantifying the planning and design parameters for the decision-making, studying the coupling system of landscape pattern and ecological processes for solving environmental problems of human settlement and to decrease uncertainties of planning and design, studying how to enhance the capacity of landscape service for human wellbeing. We proposed to promote the application of landscape ecology comprehensive researches into practice, to consolidate the scientific basis of planning and design in landscape architecture, and to construct a practice-oriented scientific research system to bridge the gap between theory and practice.