Table of Content

18 May 2018, Volume 29 Issue 5

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Special Features of Stable Isotope Ecology

Latitudinal trends in foliar δ¹³C and δ¹⁵N of Quercus variabilis and their influencing factors.

LIU Jian-feng, ZHANG Yu-ting, NI Yan-yan, HUANG Yue-ning, JIANG Ze-ping

2018, 29(5):  1373-1380.  doi:10.13287/j.1001-9332.201805.010

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We aimed to reveal the latitudinal trends in foliar δ¹³C and δ¹⁵N of Quercus variabilis, a widely distributed species in East Asia, associated with two ontogenetic stages (juvenile and mature trees) along a North-South transect (26°-40° N). The results showed that mature trees had higher foliar δ¹³C and δ¹⁵N values than juveniles. Foliar δ¹³C and δ¹⁵N values of trees with both ontogenetic stages were nonlinearly increased and decreased with latitude, respectively. No interaction between ontogenetic stage and latitude for the changes of foliar δ¹⁵N and δ¹³C indicated that both ontogenetic stages across the transect consistently responded to latitudinal environmental variations. Results from the random forest models indicated that foliar δ¹⁵N of Q. variabilis was mainly affected by soil nutrient contents, e.g., soil organic matter, phosphorus, nitrogen, whereas dominated factors for foliar δ¹³C were related to moisture, such as relative humidity, precipitation of growing season.

Water utilization characteristics of the degraded poplar shelterbelts in Zhangbei, Hebei, China.

ZHANG Huan, CAO Jun, WANG Hua-bing, SONG Bo, JIA Guo-dong, LIU Zi-qiang, YU Xin-xiao, ZENG Jia

2018, 29(5):  1381-1388.  doi:10.13287/j.1001-9332.201805.026

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In Zhangbei County, Hebei Province, poplar-dominated shelterbelts are degraded to different extents. Water availability is the main limiting factor for plant survival in arid areas. The purpose of this study was to reveal the relationship between water availability and poplar degradation. Based on the hydrogen and oxygen stable isotope techniques, we explored the water sources of Populus simonii under different degradation degrees by comparing the isotopic values of P. simonii xylem water with that in potential water source, and calculated the utilization ratio of each water source. The results showed that the water sources of poplar trees varied with degradation degree. The water sources of P. simonii gradually transferred from the deep layer to the surface layer with the increases of degradation. P. simonii with no degradation mainly absorbed soil water in the range of 320-400 cm, with the utilization rate being 25.1%. P. simonii with slight degradation mainly used soil water at depth of 120-180, 180-240 and 240-320 cm. The total utilization rate of three layers was close to 50.0%, with less utilization of water from other layers. The moderately degraded P. simonii mainly used soil water at depth of 20-40, 40-60 and 60-80 cm. The utilization rate of each layer was 17.5%-20.9%, and the contribution rate of soil water under 120 cm was less than 10.0%. The severely degraded P. simonii mainly used water from surface soil layer (0-20 cm), with the utilization rate being 30.4%, which was significantly higher than that of other water sources. The water sources of poplar shelter forests were gradually shallower during the process of degradation. However, the low soil water content in the shallow layer could not meet the normal water demand of poplar, which would accelerate the degradation and even decline of poplar.

Effects of biochar addition on the mineralization of native soil organic carbon in Cunninghamia lanceolata plantation.

YIN Yan, LIU Yan, YIN Yun-feng, MA Hong-liang, GAO Ren, YANG Yu-sheng

2018, 29(5):  1389-1396.  doi:10.13287/j.1001-9332.201805.008

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Effects of addition of different biochars on soil organic carbon (SOC) mineralization were studied by the ¹³C-labelling technique for a better understanding of biomass resource utilization and carbon sequestration in subtropical Chinese fir (Cunninghamia lanceolata) plantation. An incubation experiment under 25 ℃ was performed over a period of 112 days to address how different biochar addition would affect the mineralization of native SOC. Biochars were produced from Schimasuperba or C. lanceolata litter at 350, 550 and 750 ℃, respectively. Results showed that the mineralization of native SOC was significantly accelerated during the first three days and subsequently suppressed from 7 to 112 days of incubation after C. lanceolata biochar addition compared to the control. In the S. superba biochar addition treatment, there was a significant increase in mineralization of native SOC within the first 14 days of incubation and then a rapid decrease from days 28 to 112. After 112 days incubation, all the three C. lanceolata biochar (350, 550 and 750 ℃) additions significantly inhibited the mineralization of native SOC. A similar trend was observed for the two S. superba biochar (350 and 550 ℃) additions but not for the S. superba biochar (750 ℃) addition. The decomposition rates of S. superba biochar and C. lanceolata biochar were 0.8%-2.8% after 112 days incubation and decreased with the increases of pyrolysis temperature. Under the same pyrolysis temperature, the decomposition rate of the S. superba biochar was significantly higher than that of the C. lanceolata biochar. In conclusion, both the raw material and pyrolysis temperature of biochars would be important factors driving the mineralization of native SOC and biochar degradation.

Allocation of rice photosynthates in plant-soil system in response to elevated CO₂ and nitrogen fertilization.

REN Yi-wen, XIAO Mou-liang, YUAN Hong-chao, ZHU Zhen-ke, LI Qiao-yun, GE Ti-da, SU Yi-rong, WU Jin-shui

2018, 29(5):  1397-1404.  doi:10.13287/j.1001-9332.201805.021

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To examine the allocation of rice photosynthates and its response to the elevated CO₂ (800 μL·L^-1) and N fertilization (100 mg·kg^-1) at both tillering stage and booting stage in plant-soil system, rice was continually labelled with ¹³CO₂. The results showed that the rice root biomass at the tillering stage and the shoot biomass at the booting stage were significantly increased under elevated CO₂. Elevated CO₂ increased the rice biomass and root-shoot ratio at tillering stage, but reduced it at booting stage. Under elevated CO₂, N fertilization promoted shoot biomass during rice growth, but significantly decreased the root biomass at booting stage. Elevated CO₂ significantly increased the allocation of assimilated ¹³C to the soil at the booting stage. N fertilization did not promote the elevated CO₂-induced stimulation of assimilated ¹³C allocated to the soil, and it even decreased the proportion of assimilated ¹³C in the soil. In summary, elevated CO₂ increased the photosynthetic C allocation into soil and promoted the turnover of soil organic carbon in paddy soil. N fertilization enhanced rice shoot biomass but decreased the belowground allocation of photosynthetic C.

Effects of alpine meadow degradation on soil carbon, nitrogen, and carbon stable istope in Zoige Plateau.

ZHAO Yun-fei, WANG Xia, OU Yan-sheng, HONG Miao-miao, HUANG Zheng, LI Jia, JIA Hai-xia

2018, 29(5):  1405-1411.  doi:10.13287/j.1001-9332.201805.025

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To investigate the differences of soil carbon, nitrogen, and carbon stable isotopes in Zoige wetland, we analyzed the abundance of carbon stable isotopes and the contents of carbon and nitrogen in soils of three kinds of retrogressive successional grasslands (swampy meadow, steppe meadow, and degraded meadow). The results showed that the δ¹³C values in the meadow soil of Zoige alpine wetland ranged from -26.21‰ to -24.72‰. The abundance of δ¹³C increased with the depth of soil. There was a significantly negative relationship between δ¹³C values and logarithm of soil organic carbon content across the soil profile. The δ¹³C values in the surface soil (0-10 cm) followed the order of grassland meadow>degraded meadow>swampy meadow, and the β values followed the order of grassland meadow>swampy meadow>degraded meadow. Soil organic carbon content was 105.32, 42.11 and 31.12 g·kg^-1, while nitrogen content was 8.74, 3.41 and 2.81 g·kg^-1, and C/N was 11.26, 11.23 and 10.89, in the swampy meadow, grassland meadow and degraded meadow, respectively. The soil C/N was lower in degraded meadow than that in swampy meadow and grassland meadow. The total organic carbon and nitrogen content decreased obviously with increasing soil depth. The variations of soil δ¹³C among meadows with different degradation stages were mainly restricted to the 0-10 cm soil layer. The β values and C/N were the lowest in degraded meadow among three stages, suggesting that the mineralization rate of degraded meadow soil organic matter was relatively fast.

Effects of different fulvic acid application rates on fruit yield, quality and fate of ¹⁵N-urea in ‘Red General’ apple.

PENG Ling, LIU Xiao-xia, HE Liu, TIAN Meng, GE Shun-feng, JIANG Yuan-mao

2018, 29(5):  1412-1420.  doi:10.13287/j.1001-9332.201805.024

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To explore the effects of different fulvic acid application rates on ¹⁵N-urea absorption, utilization, residue amount, loss and fruit yield and quality, fifteen-year-old ‘Red General’/ Malus micromalus Makino was selected as experiment material by using the ¹⁵N-labeled tracer technique. Five treatments were established: single urea (CK), combination of urea and fulvic acid with varied rates (NF₁, NF₂, NF₃ and NF₄ represented 75, 150, 300 and 450 kg·hm^-2 fulvic acid application rates, respectively). The main results were as follows: the ¹⁵N derived from fertilizer (Ndff) in root, one-year-old branch and leaf were displayed with an order of NF₃>NF₄>NF₂>NF₁>CK at the fruit maturity stage, and significant difference was observed in Ndff value among the five treatments. The total N content and ¹⁵N absorption amount were highest in NF₃, followed by NF₄, and lowest in CK. Compared with CK, the ¹⁵N utilization rate in NF₁, NF₂, NF₃ and NF₄ was increased by 14.2%, 33.5%, 64.2% and 50.0%, and the ¹⁵N loss rate was decreased by 9.1%, 18.5%, 37.1% and 28.7% respectively. The residue amount of ¹⁵N-urea varied across different treatments, and that in 0-60 cm soil layer under combination of urea and fulvic acid was significantly higher than CK, with the highest value occurred in NF₃, while it was lower than CK in 60-100 cm soil layer. In comparison with CK treatment, the largest increment of yield per plant and net income appeared in NF₃, with an enhancement of 15.8% and 20.2%, respectively. In addition, the fruit hardness, soluble solid and sugar-acid ratio reached the highest value in NF₃. Considering the responses of fruit yield and N utilization efficiency, the suitable fulvic acid application rate was 326.41-350.61 kg·hm^-2.

Effects of controlled-release nitrogen fertilizer and bag-controlled release fertilizer on utilization of ¹⁵N-urea in ‘Orin’ apple and its accumulation in soil.

SHA Jian-chuan, WANG Fen, TIAN Ge, YU Bo, GE Shun-feng, JIANG Yuan-mao

2018, 29(5):  1421-1428.  doi:10.13287/j.1001-9332.201805.022

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Taking a six-year old ‘Orin’ apple tree plantation (‘Orin’/SH6/ Malus micromalus Makino) as test material, the effects of common urea treatment (CU), bag-controlled release ferti-lizers treatment (BCRF) and controlled-release nitrogen fertilizer treatment (CRNF) on ¹⁵N-urea absorption, utilization, loss and accumulation dynamics of nitrogen content in 0-80 cm soil layer were investigated by ¹⁵N labeled tracer method. The results showed that compared with CU treatment, both CRNF and BCRF treatments increased the inorganic nitrogen content in soil at the late stage of apple growth, the leaf SPAD value, leaf nitrogen content, net photosynthetic rate and ¹⁵N derived from fertilizer (Ndff value) of different organs at fruit maturity stage, with CRNF showing stronger effects than BCRF. The amount of ¹⁵N residue in 0-40 cm soil layer showed a decreasing trend in different phenological stages. The amount of ¹⁵N residue was the highest in CRNF, followed by BCRF, and the lowest in CU, among which CRNF declined gently with ¹⁵N residue mainly concentrated in the 0-40 cm soil layer. ¹⁵N residue in 40-80 cm soil layer showed an increasing trend in different phenological stages, which was the highest in CU, followed by BCRF, and the lowest in CRNF, and that of CRNF increased gently. The ¹⁵N fertilizer utilization rate of CRNF was 32.6% at fruit maturity stage, which was 1.11 and 1.56 times as high as that of BCRF and CU, whereas its ¹⁵N loss rate was 21.6%, being obviously lower than BCRF (35.6%) and CU (59.6%). CRNF significantly improved fruit yield and quality and increased economic benefits.

Nitrogen application technology in dwarfed apple trees.

CHEN Qian, DING Ning, PENG Ling, ZHU Zhan-ling, GE Shun-feng, JIANG Yuan-mao

2018, 29(5):  1429-1436.  doi:10.13287/j.1001-9332.201805.027

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¹⁵N trace technique was used to explore the characteristics of ¹⁵N-urea absorption, utilization, loss and fruit quality of eight-year-old ‘Yanfu3’/M26/Malus hupehensis Rehd. seedlings. There were three different nitrogen fertilization treatments: one-time nitrogen application in spring (Ⅰ), two times nitrogen application (Ⅱ), the intensive technique of nitrogen application with several times application and reduction in amount (Ⅲ). The results showed that leaf area, chlorophyll content (SPAD value), photosynthetic rate (P_n), total N content of leaves and the total biomass per plant (except fruit), as well as the root-shoot ratio of treatment Ⅲ were obviously higher than those in the treatments of Ⅰ and Ⅱ. Treatment Ⅲ significantly increased the protective enzymes (SOD, POD and CAT) activities and decreased the malondialdehyde (MDA) content in leaves. Significant differences were found on the ¹⁵N derived from fertilizer (Ndff value) of different organs, with the fruit Ndff showing the highest, followed by the one-year-old branches, leaves and roots of the three treatments. The Ndff values of each organ were the highest in the treatment Ⅲ. At fruit maturity stage, total N content of plant in treatment Ⅲ was 93.0 mg·kg^-1, which was obviously higher than that in the treatments Ⅰ (70.2 mg·kg^-1) and Ⅱ (81.9 mg·kg^-1). ¹⁵N nitrogen utilization ratio of treatment Ⅲ was 33.6%, which was obviously higher than that in the treatments Ⅰ (20.4%) and Ⅱ (26.0%). The ¹⁵N loss rate was 46.9% in treatment Ⅲ, being obviously lower than that in the treatments Ⅰ (56.5%) and Ⅱ (52.9%). There were significant differences of fruit mass, soluble solid, fruit firmness, soluble sugar content, titratable acids and sugar-acid ratio among different treatments, with the highest values in the treatment Ⅲ and the lowest values in treatment Ⅰ.

Effects of different phosphorus application rates on growth, ¹⁵N-urea absorption, and utilization characteristics of pear rootstocks.

SHA Jian-chuan, XIA Ying, LIU Song-zhong, LIU Jing-jing, LIU Xiao-xia, JIANG Yuan-mao, GE Shun-feng

2018, 29(5):  1437-1442.  doi:10.13287/j.1001-9332.201805.023

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Three kinds of potted one-year-old pear rootstocks (Pyrus calleryana, P. pashia, and P. xerophila) and ¹⁵N trace technique were used to examine the effects of different phosphorus application rates (P₀, P₁, P₂, P₃ and P₄ equivalent to 0, 50, 100, 150 and 200 kg·hm^-2 P₂O₅, respectively) on plant growth and the characteristics of ¹⁵N-urea absorption and utilization. The results showed that, with the increases of phosphorus levels, plant height, ground diameter, dry mass, root surface area, root length, number of root tips, root activity, root respiration rate, Ndff values, and nitrogen use efficiency of rootstocks first increased and then decreased. However, the range of rise and fall of different rootstocks were distinct, and each index reached the highest level at different phosphorus levels. The plant height, diameter, dry mass of P. xerophila were the highest under the same phosphorus level, followed by P. pashia, and P. calleryana was the lowest. The root architecture parameters and root respiration rate showed the same trend, but Ndff values and nitrogen use efficiency performed different. Under different phosphorus levels, each index of P. xerophila reached the highest level at P₃, but those of P. pashia and P. calleryana appeared at P₂ and P₁ rates, respectively. The Ndff values in stem were the highest among different organs of rootstocks at diffe-rent phosphorus levels, and the highest nitrogen use efficiency of P. xerophila, P. pashia and P. calleryana was 9.6%, 8.9% and 8.3%, respectively. The variations of plant growth and N absorption and utilization of different pear rootstocks across different phosphorus levels indicated that phosphorus fertilizer should be carry out reasonably in practice and give full consideration of phosphorus demands of plants.

Characteristics of absorption, utilization, and distribution of ¹⁵N-urea for Korla fragrant pear in spring.

WANG Qian-deng, CHEN Bo-lang, YUSUFUJIANG Yusuyin, WANG Cheng, CHAI Zhong-ping

2018, 29(5):  1443-1449.  doi:10.13287/j.1001-9332.201805.009

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Six-year-old Korla fragrant pear trees were fertilized with ¹⁵N-labelled urea before early bud stage to examine the absorption, distribution, and utilization of urea. Results showed that there was a significant difference of ¹⁵N distribution rate in organs at different growth stages. ¹⁵N was pre-ferentially distributed in the roots , with Ndff (¹⁵N amount absorbed from the fertilizer contribution rate of the total nitrogen organ) being the highest in roots following by new shoots at full-bloom stage. During new shoot growing and fruit expanding stages, ¹⁵N absorbed in roots preferentially moved to new organs (leaves and new shoots), with ¹⁵N distribution rate to roots being continuously decreased. Fruits became the new distribution center with highest Ndff at harvest stage. The amounts of absorbed ¹⁵N in fruits accounted for 19.8% of total absorbed ¹⁵N in the tree. The utilization rate of ¹⁵N-labelled urea at current season increased gradually with the growth stages. The maximum value of utilization rate was 18.5%, which was observed at harvest stage.

Key pathway of methane production and characteristics of stable carbon isotope of the Tuojia River waterbody.

ZHAO Qiang, LYU Cheng-wen, QIN Xiao-bo, WU Hong-bao, WAN Yun-fan, LIAO Yu-lin, LU Yan-hong, WANG Bin, LI Yong

2018, 29(5):  1450-1460.  doi:10.13287/j.1001-9332.201805.030

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This study aimed at exploring the key pathway of methane production and clarifying the composition and distribution of carbon (C) isotopes in the Tuojia River waterbody in Hunan Pro-vince. We estimated CH₄ concentrations and fluxes of four reaches (S₁, S₂, S₃ and S₄) by a two-layer diffusion model and gas chromatography. The spatial and temporal distribution of CH₄ flux and its relationship with environmental factors were examined. The key pathway of CH₄ production was investigated by stable C isotope method to analyze the distribution characteristics of ¹³C isotope (δ¹³C) of water dissolved CH₄ and seston/benthic organic matter. There was significant seasonal variability in water pH, with mean value of (7.27±0.03). The concentration of dissolved oxygen (DO) showed strong seasonal and spatial variations, with the range of 0.43-13.99 mg·L^-1. The maximum value of DO occurred in S₁ and differed significantly in summer and autumin. In addition, DO differed significantly in winter and other seasons in S₂, S₃ and S₄. The concentration of dissolved organic carbon (DOC) showed a gradual increasing trend from source to estuary. The highest concentration of DOC (8.32 mg·L^-1) was found in S₂, while the lowest was observed in S₁ (0.34 mg·L^-1). The electrical conductivity (EC) and oxidation-reduction potential (ORP) of water ranged from 17 to 436 μS·cm^-1 and from -52.30 to 674.10 mV, respectively, which were significantly different among the four reaches (P<0.05). Water ammonium nitrogen (NH₄⁺-N) and nitrate nitrogen (NO₃^--N) concentrations were in the ranges of 0.30-1.35 (averaged 0.90±0.10) mg·L^-1 and 0.82-2.45 (averaged 1.62±0.16) mg·L^-1, respectively. The dissolved concentration and diffusion flux of CH₄ ranged from 0 to 5.28 μmol·L^-1 and from -0.34 to 619.72 μg C·m^-2·h^-1, respectively, with significant temporal and spatial variations. They showed a similar trend among reaches. Their values were highest in spring, followed by in winter and lowest in summer and autumn. Spatially, the CH₄ concentration and flux followed the order of S₂>S₃>S₄>S₁. The correlation analysis showed that CH₄ flux was positively correlated with NH₄⁺-N and DOC. The pathway of CH₄ production of all reaches was dominated by acetic acid fermentation, while there were obvious differences among the four reaches. The contribution of CH₄ from acetic acid fermentation was greatest (87%) in S₁, followed by S₄(81%), S₂(78%) and S₃(76%). The mean value of the δ¹³C for dissolved CH₄, seston organic matter and benthic organic matter was -41.64‰±1.91‰, -14.07‰±1.06‰ and -26.20‰±1.02‰, respectively. There was a positive correlation between the δ¹³C of dissolved CH₄ and benthic organic matter, whereas the δ¹³C value of dissolved CH₄ was negatively correlated with CH₄ flux.

Temporal and spatial variations of hydrogen and oxygen isotopes in Tuojia River and its influencing factors.

WU Hong-bao, ZHAO Qiang, QIN Xiao-bo, GAO Qing-zhu, LYU Cheng-wen

2018, 29(5):  1461-1469.  doi:10.13287/j.1001-9332.201805.020

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The characteristics of hydrogen and oxygen stable isotopes in river is important for regional hydrologic cycle research. To uncover water supply sources in subtropical agricultural basin from a perspective of stable isotopes, field measurements were conducted in four reaches (S₁, S₂, S₃ and S₄) of Tuojia River from April to August 2017. We analyzed the spatial and temporal variations in hydrogen and oxygen isotopes and deuterium excess parameters and their relationship with precipitation, altitude and water quality. Results showed that hydrogen and oxygen isotopes and deuterium excess values ranged from -43.17‰ to -26.43‰ (-35.50‰±5.44‰), -7.94‰ to -5.70‰ (-6.86‰±0.74‰), and 16.77‰ to 23.49‰ (19.39‰±1.95‰), respectively. Under the influence of monsoon circulation, hydrogen and oxygen isotopes showed substantial seasonal variation, with spring (δD: -29.88‰±3.31‰; δ¹⁸O: -6.18‰±0.57‰) > summer (δD: -39.25‰±2.65‰; δ¹⁸O: -7.32‰±0.42‰). The spatial distribution of hydrogen and oxygen isotopes values increased fluctuantly with the position from the sampling site to the river’s source, with δD: S₁<S₄<S₃<S₂, and δ¹⁸O: S₁<S₃<S₄<S₂. The deuterium excess values had no significant temporal variation, while it spatially increased gradually with the river levels. The slope and intercept of water line in this river were smaller than that of the local meteoric water line, suggesting that precipitation was the primary water source for this river. At the seasonal scale, both δD and δ¹⁸O were significantly negatively correlated with water temperature (δD: r=-0.92; δ¹⁸O: r=-0.88) and δ¹⁸O was negatively correlated with altitude (r=-0.96). At spatial scale, δ¹⁸O had a significantly positive correlation with water temperature. The δD and δ¹⁸O had negative correlation with precipitation, but being not statistically significant.

Effects of organic and inorganic fertilizers on emission and sources of N₂O in vegetable soils.

LIN Wei, DING Jun-jun, LI Yu-zhong, XU Chun-ying, LI Qiao-zhen, ZHENG Qian, ZHUANG Shan

2018, 29(5):  1470-1478.  doi:10.13287/j.1001-9332.201805.029

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To clarify the microbial pathway of the N₂O production and consumption under different fertilizers and provide theoretical basis for the reduction of N₂O emission and rational management of fertilization in vegetable soils, we examined dynamics of N₂O flux and isotope signatures under different fertilizer treatments in the vegetable soils of Beijing, by setting up four treatments (organic-acetylene, organic-nonacetylene, inorganic-acetylene, inorganic-nonacetylene) and using the stable isotope technique of natural N₂O abundance. The results showed that the cumulative N₂O emission from organic-acetylene group, organic-nonacetylene group, inorganic-acetylene group and inorganic-nonacetylene group was (374±37), (283±34), (458±36), (355±41) g·m^-2 in cabbage growing season, respectively. N₂O fluxes were significantly lower in treatments with organic fertilizer than those with inorganic fertilizer and significantly higher in acetylene group than nonacetylene group. The degree of N₂O reduction were similar in both fertilizer treatments, and higher nitrification was found in inorganic fertilizer than organic fertilizer treatments. Acetylene only inhibited partial nitrification and partial N₂O reduction at the peak of N₂O emission. When the emission was reduced, N₂O reduction could be completely suppressed. Therefore, the inorganic fertilizer might trigger nitrification and promote higher N₂O emission. The high concentration of N₂O could withstand that acetylene to inhibite N₂O reduction. Hence, using organic fertilizers instead of some inorganic ones could effectively reduce N₂O emission in vegetable soils of Beijing. The N₂O concentration threshold should be considered when we identify N₂O source by acetylene inhibition method.

Influence of below-cloud secondary evaporation on stable isotope composition in precipitation in Northwest China.

LIU Jie-yao, ZHANG Fu-ping, FENG Qi, LI Zong-xing, ZHU Yi-wen, NIE Shuo, LI Ling

2018, 29(5):  1479-1488.  doi:10.13287/j.1001-9332.201805.028

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The precipitation isotope data and meteorological data of eight stations provided by GNIP (Global Network for Isotopes in Precipitation) and two stations from the present study, combined with HYSPLIT model and water droplet evaporation model were used to examine the spatial and temporal distribution of precipitation δ¹⁸O and d values in Northwest China. The secondary evaporative effect of existence was evaluated and then quantitatively discussed, with the sensitive factors of secondary evaporative effect being considered. The results showed that during the summer monsoon, the δ¹⁸O and d values decreased from south to north in Xinjiang, while the δ¹⁸O value increased but d values decreased from south to north and from east to west of Shaanxi-Gansu-Ningxia region. During the winter monsoon, the δ¹⁸O value decreased from east to west in whole Northwest region, while the d value increased from south to north in Xinjiang, decreased from south to north and increased slightly from east to west in Shanxi-Gansu-Ningxia. The slope and intercept (6.80, -0.07) of the atmospheric precipitation line in the summer monsoon period was significantly lower than that of annual mean (7.27, 3.37) and winter monsoon period (7.46, 6.07), indicating that the secondary evaporation was stronger during the summer monsoon. The evaporation ratio in the summer monsoon was 4.49%, which was higher than 3.65% in the winter monsoon. However, the evaporation ratio of the winter monsoon was higher than the summer monsoon around of Loess Plateau, which might closely relate to the increasing drought of the Loess Plateau in recent years. Finally, the intensity of secondary evaporation decreased with increasing relative humidity, precipitation and vapor pressure but increased with increasing temperature (greater than 0 ℃). The influences of those factors (humidity, precipitation, temperature and vapor pressure) on the secondary evaporation were dependent on the differences of ranges.

Difference of trophic niche between Sebastiscus marmoratus and Larimichthys polyactis in marine ranching of Ma’an Archipelago, China.

LI Chao-wen, WANG Kai, CHENG Xiao-peng, ZHANG Shou-yu, ZHANG Yun-ling

2018, 29(5):  1489-1493.  doi:10.13287/j.1001-9332.201805.019

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Marine ranching is an effective way to protect and restore coastal fishery resources. In order to assess the impacts of marine ranching construction on the trophic niches and interspecific competition of Sebastiscus marmoratus and Larimichthys polyactis, we analyzed the relationship between the changes of intraspecies trophic niche and the interspecific competition, based on the carbon and nitrogen stable isotope data of these two species collected from 2013 to 2016. The results showed that the intraspecies trophic niches of both species increased significantly in marine ranching area from 2013 to 2016. The total area of the convex polygon (TA) niche increased from 1.89 to 12.43 for S. marmoratus, and increased from 0.34 and 8.86 for L. polyactis, with the interspecific niche overlap area of these two species increasing from 0.13 to 7.69. The standard elliptic trophic niche increased from 1.11 to 4.94 for S. marmoratus, and from 0.14 to 4.06 for L. polyactis, with the interspecific niche overlap area increasing from 0 to 0.26. Values of the δ¹³C and δ¹⁵N of both species showed a tendency of decreasing with time, with significant changes of δ¹³C, but non-signi-ficant for δ¹⁵N. Dietary overlap between those two species increased from 68.9% to 90.6%.

Original Articles

Inter- and intra-annual dynamics of vegetation litter at different habitats in Horqin Sandy Land, China.

WANG Xu-yang, LI Yu-qiang, LUO Yong-qing, LIAN Jie, NIU Ya-yi, GONG Xiang-wen, YANG Huan

2018, 29(5):  1494-1502.  doi:10.13287/j.1001-9332.201805.005

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As one of the important pathways of material and energy flow between plant and soil system, litterfall plays a key role in the process of vegetation and soil restoration in ecologically fragile region. To explore the inter- and intra-annual dynamics of litter production and related regulatory factors at different habitats in sandy land ecosystem, we investigated the litter production during nine continuous growing seasons, while the air temperature and precipitation were measured over mobile dune, fixed dune, and grassland in Horqin Sandy Land. The results showed that annual litter production at different habitants were in the order of mobile dune (9.01 g·m^-2) < fixed dune (67.46 g·m^-2) < grassland (119.55 g·m^-2). The inter-annual dynamics of litterfall fluctuated significantly, with a double-peak curve in fixed dune and “W” curve in grassland. The intra-annual variation of litterfall exhibited a “U” curve at all the three habitats, with peaks appearing in April and September, respectively. Precipitation and temperature had significant effects on the intra-annul dynamics of litterfall production in fixed sand dune and grassland, but had no significant effect on the inter-annual dynamics of litter production at three habitats. Temperature was the major factor affecting the dynamics of the litter fall during the growing season in Horqin Sandy Land.

Canopy transpiration of Larix principis-rupprechtii plantation and its impact factors in diffe-rent slope locations at the south side of Liupan Mountains, China.

WANG Yun-ni, CAO Gong-xiang, WANG Yan-hui, XU Li-hong, ZHANG Wen-jun, WANG Xiao-jiang

2018, 29(5):  1503-1514.  doi:10.13287/j.1001-9332.201805.006

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Based on a continuous field observation in the Larix principis-rupprechtii plantation plots, located at the upper (P₁), middle-upper (P₂), middle (P₃), middle-lower (P₄), and lower (P₅) positions, in a southeast-facing slope of the Xiangshuihe watershed of Liupan Mountains, China, the stem sap flow was observed with the thermal diffusivity probe method. The soil water potential and meteorological factors were monitored from May to October, 2014. We found significant differences among slope positions in the daily forest transpiration (T_r, mm·d^-1), with an order of P₂ (0.975)＞P₄ (0.876)＞P₃ (0.726)＞P₁ (0.653)＞P₅ (0.628). T_r was significantly positively correlated with the daily maximum temperature (T_max), daily mean solar radiation (SR), daily mean saturated vapor pressure deficit (VPD), potential evapotranspiration (PET), and daily mean soil water potential (Ψ), but negatively correlated with the daily mean air relative humidity (RH), daily precipitation (P), and daily minimum temperature (T_min). According to the upper boundary line ana-lysis, significant differences were found in the degree of T_r responding to each single environmental factor among slope positions. The degree of its responses gradually decreased for average daily air temperature (T), RH, VPD, PET and Ψ, whereas increased for the SR and daily average volumetric soil water content (VSM) from the upper position to the lower. Results from regression and partial correlation analysis showed that variation of T_r was mainly controlled by VPD, PET and RH in different slope positions. T_r was also strongly affected by Ψ and T in the upper-slope positions and by SR, T_min and VSM at the lower-slope positions. Generally, the T_r difference among slope positions was a consequence of joint contributions of soil water and meteorological factors. It is necessary to consider the changes of soil water and meteorological factors in different positions along the slope when examining slope-scale or watershed-scale forest transpiration with sap flow estimated from xylem sap flux density measurements of a particular plot.

Composition and seasonal dynamics of seed rain in Chinese fir (Cunninghamia lanceolata) plantation.

ZHU Chen-xi, LIU Zhi-gang, YU Yang-yang, LIU Qing-qing, ZHAO Chong, ZHENG Xiao-yang, WANG Zheng-ning, LIU Bo

2018, 29(5):  1515-1522.  doi:10.13287/j.1001-9332.201805.002

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Chinese fir plantation is an important part of the subtropical forests in southern China. It has a sustainable natural regeneration ability, which is the foundation of determining community succession direction and maintaining their large area. The main objective of this study was to investigate whether the seed pool was the main restricting factor for the natural regeneration of Chinese fir plantation. Mixed broad leaf-conifer forest and pure plantation of Chinese fir were selected to study the species composition, quantity and seasonal dynamics of all species and dominant species. The results showed that seeds from 21 species belonged to 13 families and 18 genera were collected in the mixed forest, while seeds from 19 species belonged to 12 families and 16 genera were collected from pure forest. Seed rain intensities of all species were 3797 and 3300 seeds·m^-2 in mixed forest and pure plantation, respectively. The number of seeds from tree species was absolutely dominant in seed rain (mixed forest 89.1%, pure plantation 86.2%). The number of Chinese fir seeds was the largest, the intact seeds intensities were 825 and 345 seeds·m^-2, respectively. The proportion of all types of seeds in both stands followed the order: the intact seeds > empty or rotten seeds > feeding seeds. The seed rain of both stands had significant seasonal dynamics, both reaching the peak in autumn. The seed rain mainly was intact seeds at the peak of seed-falling. Both mixed forest and pure plantation of Chinese fir had plenty of seeds. The results indicated that the seed rain is not the main factor that restricts natural regeneration in Chinese fir plantations.

Effects of temperature and moisture on net ecosystem CO₂ exchange over a meadow wetland in the Horqin, China.

CHEN Xiao-ping, LIU Ting-xi, WANG Guan-li, DUAN Li-min, LEI Hui-min, WANG Dan

2018, 29(5):  1523-1534.  doi:10.13287/j.1001-9332.201805.003

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Using the eddy covariance technique, the Bowen-ratio meteorological and soil monitoring system, we analyzed the CO₂ flux dynamics and its responses to temperature and moisture over a meadow wetland in the Horqin during the growing season (from May to September) in 2016. The results showed that the accumulated net ecosystem CO₂ exchange (NEE) was -766.18 g CO₂·m^-2 during the growing season. The gross primary productivity (GPP) and ecosystem respiration (R_e) were 3379.89 and 2613.71 g CO₂·m^-2, respectively. The ratio of R_e to GPP was 77.3%, indicating that this ecosystem was an obvious carbon sink. The average diurnal variation of NEE exhibited a single peak U-shaped curve with an absorption of CO₂ from May to mid August and a release of CO₂ from late August to September. Daytime NEE well fitted with the photosynthetically active radiation (PAR) by a rectangular hyperbolic function. Meanwhile, the relationship was affected by the environmental factors, including vapor pressure deficit (VPD), soil water content (SWC) and air temperature (T_a). Regression analysis showed that the VPD and SWC for the maximum daytime NEE were 1.75 kPa and 35.5%, respectively. Daytime NEE increased with T_a, and with no inhibitory effect on the daytime NEE when it reached the maximum. Nighttime NEE had an exponential relationship with soil temperature (T_s). During the entire growing season, the temperature sensitivity of the ecosystem respiration (Q₁₀) was 2.4, which was negatively related to SWC. The nighttime NEE was controlled by both T_s and SWC.

Carbon, nitrogen and phosphorus contents and their ecological stoichiometry in litters and soils on meadow of Wugong Mountain, Jiangxi, China at different altitudes.

LIU Qian, WANG Shu-li, DENG Bang-liang, ZHENG Xiang, HUANG Li-jun, GUO Xiao-min, ZHANG Xue-ling, ZHANG Ling

2018, 29(5):  1535-1541.  doi:10.13287/j.1001-9332.201805.007

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Carbon (C), nitrogen (N) and phosphorus (P) contents and ecological stoichiometry and their correlations of litter and soil along 1500-1900 m on Wugong Mountain meadow were studied. The results showed that litter C, N and P contents varied in the range of 397.5-458.24, 11.59-17.12, 1.05-2.19 mg·g^-1, respectively. Litter C content decreased, and the contents of N and P decreased first and then increased with the increases of altitude. Soil C, N and P contents varied in the range of 51.64-80.01, 3.30-4.77, 0.44-1.09 mg·g^-1, respectively. Soil C, N and P contents first increased and then decreased with the increases of altitude. However, soil P varied much less along the altitude gradient. Litter C:N, C:P and N:P varied in the range of 24.73-40.36, 203.65-463.08, 7.16-13.80, respectively, and first increased but then decreased with altitude. Soil C:N, C:P and N:P were 14.95-16.95, 56.87-162.52, 3.69-10.58, respectively. Soil C:N changed little with altitude. Soil C:P and N:P first increased and then decreased with increa-sing altitude, with the maximum presented at 1600-1700 m. Changes in soil C, N and P contents differed between litter and soil on Wugong Mountain meadow. The mean C, N and P contents as well as C:N, C:P and N:P in litter were higher than those in soil.

Geostatistical analysis on the spatial pattern of Quercus mongolica population in different communities.

CHEN Ke-yi, ZHANG Hui-ru, LEI Xiang-dong

2018, 29(5):  1542-1550.  doi:10.13287/j.1001-9332.201805.017

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Taking Quercus mongolica population in the secondary forest of Q. mongolica as the research object, two plots in different stages of succession (A and B) were set up in Tazigou Forest Farm of Wangqing Forestry Bureau, Jilin Province. By applying the method of adjacent grid survey, each plot was divided into 100 units of 10 m×10 m and the spatial coordinates of each tree in the unit were accurately located to survey all the basic information of trees with diameter at breast height (DBH)≥1 cm. The degree, composition, scale and pattern of spatial heterogeneity of individual tree of Q. mongolica were analyzed by means of semi-variance function and fractal dimension of geostatistics. By using Kriging interpolation method, unbiased estimation of tree attribute with spatial autocorrelation was carried out, distribution map was drawn and spatial distribution pattern was analyzed. The results showed that the best semi-variance function of tree attributes in two plots was mainly distributed in an exponential model and a spherical model with an aggregated distribution. The degree of spatial autocorrelation and continuity of plot A were higher than that of plot B. The DBH and the east-west crown (C_EW) had strong spatial heterogeneity and autocorrelation in the two plots. The tree attributes of both plots showed strong spatial heterogeneity in the north-south direction. In addition, there was strong spatial heterogeneity in the northwest-southeast direction of plot A and in the northeast-southwest of plot B. The strength of the spatial heterogeneity was higher and the scale being larger in plot A. The variations of DBH and C_EW were obvious in plot A, while the variations of C_EW and south-north crown (C_SN) were obvious in plot B. The fractal dimension and semi-variogram function showed the same result. The tree attributes of plot A were mainly patchy and stripe, and the variation trend of spatial distribution pattern was obvious. The tree attributes of plot B was broken, with complex pattern. Those results indicated that the characteristics of population, community development, spatial scale and spatial horizontal direction might affect the spatial pattern of populations. The geostatistical analysis method is helpful to quantitatively and directly describe population growth and development trend, which can provide a theoretical basis for the sustainable management of Q. mongolica secondary forests in Northeast China.

Nondestructive detection of total nitrogen content in leaves of Santalum album based on ST-PCA-BP neural network.

CHEN Zhu-lin, WANG Xue-feng

2018, 29(5):  1551-1558.  doi:10.13287/j.1001-9332.201805.004

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Nitrogen is one of the most important elements for plant growth. Producers often use a lot of nitrogen fertilizer during plant growth process. However, excessive fertilizer often cause ground-water pollution. In this study, we proposed a nondestructive testing method for total nitrogen content in leaves of sandalwood (Santalum album) based on ST-PCA-BP neural network. The results showed that, due to the wide color range of L^*a^*b^* color system and its robustness in illumination change, images obtained from the field which were converted from RGB to L^*a^*b^* color system had a satisfying segmentation result. The proposed ST-PCA-BP neural network was characterized by choosing variables through significance test (ST) and using variance inflation factor (VIF) and conditional index (CI) to analyze collinearity of results, and further using principal component analysis (PCA) to eliminate it. Such a method reduced the probability of the chance that BP neural network fell into the local minimum. Compared with the result of original data, data after ST processing, and data after PCA processing, the results of proposed method had the highest coefficient of determination, while the mean residual error and the root mean square error were the smallest. It was the best way to detect the total nitrogen content of sandalwood leaves with real-time and non-destructive method.

Influence of rainwater harvesting and soil anti-seepage on soil water infiltration, distribution and use efficiency in hilly orchard.

JIN Bo, WANG Yan-ping, MU Yan, LI Sheng-guang

2018, 29(5):  1559-1568.  doi:10.13287/j.1001-9332.201805.018

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Rainwater harvesting and soil anti-seepage technology is a new technology based on the ridge film mulching and furrow rainwater harvesting. To explore the application effects of rainwater harvesting and soil anti-seepage technology, four different treatments including control (CK), loessal soil with compacted anti-seepage treatment (L₁), red clay with anti-seepage treatment (R₁), and red clay with compacted anti-seepage treatment (R₂) were set up in a “Fuji” hillside orchard in Mizhi Demonstration Station of northern Shaanxi Province. Soil bulk density, stable infiltration rate, soil water content, fruit quality and yield, and water use efficiency were measured. Results showed that R₂ had the best anti-seepage efficiency with the highest bulk density (1.61 g·cm^-3), the minimum water holding capacity, and the least stable infiltration rate (0.02 mm·min^-1). The empirical formula of Kostiakov equation was suitable for describing water infiltration characteristics. Throughout the growing season, soil moisture for 0-60 cm soil depth in the rainwater harvesting ditch could be improved by the different anti-seepage treatments. R₂ had the highest soil water content all the time and could satisfy the suitable water content standard for growth and development of apple trees in the dry season. Under the anti-seepage treatment, there was an “low humid layer” with 20-30 cm of soil layer under 60 cm soil depth, but the variation tendency of soil water content from “low humid layer” to 200 cm soil layer was stable and slightly higher than that in CK. Rainwater harvesting and soil anti-seepage treatments could increase fruit yield and water use efficiency, and improve the quality of fruit. Compared with that in CK, the fruit yield, the rate of good fruit, and water use efficiency of R₂ treatment increased by 19.2%, 26.5%, and 24.5%, respectively. Therefore, rainwater harvesting and soil anti-seepage technology was recommended as the effective agricultural measurement in the apple production in loess hilly areas of northern Shaanxi Province.

Effects of microtopography on the pattern and association of dominant population.

LIU Min-xia, LIAN Yi-ming, LI Wen

2018, 29(5):  1569-1575.  doi:10.13287/j.1001-9332.201805.001

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Different spatial distribution patterns and correlations could reflect the adaptation strategies of plant populations to different habitats. Geranium wilfordii and Gueldenstaedtia verna are the major species in the subalpine meadow. Within a field experiment, the Ripley K function was used to analyze the relationship of spatial distribution pattern and interspecific association between G. wilfordii and G. verna in different slope aspects. The results showed that soil water content and nutrient content gradually increased, whereas soil temperature and light intensity gradually decreased along the gradient from south to north slope. The distribution of G. verna and G. wilfordii showed significant differences in three slope aspects (north, west and south slopes). G. verna showed an increa-sing trend, while G. wilfordii showed a decreasing trend from north to south slope. On the north slope, G. verna populations showed aggregation distribution at 0-1.8 m scale, while the aggregation intensity weakened and tended to be a random distribution at 1.8-5.0 m scale. G. wilfordii populations showed aggregation distribution at 0-5.0 m scale. On the west slope, G. verna population showed aggregation distribution at the 0-1.2 m scale, and tended to be a random distribution at the 1.2-5.0 m scale. G. wilfordii population showed aggregation distribution at the 0-2.2 m scale, and tended to be a random distribution at the 2.2-5.0 m scale. On the south slope, G. verna and G. wilfordii population showed random distribution at the 0-5.0 m scale. Both species showed positive correlation at the 0-1.0 m scale but not at the 1.0-5.0 m scale on the north slope. G. verna and G. wilfordii were negatively associated at the 0-2.1 m scale but unrelated at the 2.1-5.0 m scale on the west slope. On the south slope, both species showed no correlation at the 0-5.0 m scale.

Assessment of the potential for urban facade greening in Xinjiekou District, Nanjing, China.

SHI Bao-gang, YIN Hai-wei, KONG Fan-hua

2018, 29(5):  1576-1584.  doi:10.13287/j.1001-9332.201805.015

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Green facade is an important strategy to improve the urban eco-environment and reduce the negative effects of human activities in central districts of cities which are land-scarce and lack green spaces. We first summarized the limiting factors for the construction of green facades locally and internationally. Then, we used the Xinjiekou District of Nanjing City in China as a case study area, and selected the wind environment, solar environment, and physical build environment that might impact the potential development of green facades as key factors to quantitatively analyze singlely by geographic information systems (GIS) and computational fluid dynamics (CFD). Finally, the potential area to develop green facades was assessed through a multi-factor overlay analysis. The results showed that 17726 m² of wall spaces in the Xinjiekou District had a high potential for facade greening, accounting for 30.8% of all exterior wall space under a height of 12 m and 17.3% of the entire study area. Sunlight was a key limiting factor in determining whether a green facade should be developed. Irrigation was identified as another important factor that might strongly affect the growth of vertical vegetation in urban environment. The spatial distribution of walls suitable for facade greening was uneven, with an “inner-high and south-high” spatial pattern. Our results would help to guide the design and development of green facades in Xinjiekou, and also provide a reference for planning and utilizing green wall space projects in other built and dense urban areas.

Long-term changes of land use/cover in the Three Gorges Reservoir Area of the Yangtze River, China.

HUANG Chun-bo, TENG Ming-jun, ZENG Li-xiong, ZHOU Zhi-xiang, XIAO Wen-fa, ZHU Jian-hua, WANG Peng-cheng

2018, 29(5):  1585-1596.  doi:10.13287/j.1001-9332.201805.012

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Understanding the temporal and spatial dynamics of land use/cover (LUC) can contri-bute to reveal the impacts of climate change and human activities on ecosystems and thus be an important prerequisite for ecosystem management. As an ecologically vulnerable area in China, the Three Gorges Reservoir Area (TGRA) of the Yangtze River presented significant complexity in the response to environmental changes. However, there is a general lack of understanding in the underlying mechanism. In this study, we interpreted the time series remote sensing images derived from the Landsat sensors to map the LUC of the TGRA, and aimed to analyze the long-term changes in the distribution and structure of LUC and elucidate the evolution process of LUC, which could provide a scientific basis to understand the complexity of ecosystem changes and regional ecosystem management in ecologically fragile regions. The results showed that the TGRA presented the significant changes in spatial heterogeneity of LUC structure from 1990 to 2015. Meanwhile, the landscape changed from farmland to woodland (forest and shrubland). Farmland decreased from 66.2% to 40.4%, but woodland increased from 31.3% to 53.5%, buildings and water area increased gradually. Forest gradually spread to the middle of the TGRA, while the buildings presented a scattered expansion. In the altitude zone of 500-1000 m and slope zone of 15°-25°, woodland increased noticeably, and the coniferous forest, mixed forest and shrubland had a higher growth rate. In the study period, due to the urban construction and the various ecological restoration projects in the TGRA, the LUC structure varied with the dam’s impoundment and was characterized by the ecosystem restoration. Ecological restoration projects were helpful to reduce the negative impacts of urban construction and economic development on the environment.

Impacts of land use change on ecosystem services in the agricultural area of North China Plain: A case study of Shangqiu City, Henan Province, China.

LIU Ya-ru, WANG Cong, YAN Li-jiao

2018, 29(5):  1597-1606.  doi:10.13287/j.1001-9332.201805.011

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Under the rapid urbanization, quantitatively assessing the impacts of land use and cover change (LUCC) on ecosystem service is of great significance for regional ecological environment construction. Based on the land use maps of Shangqiu City (as the typical agricultural area of North China Plain) in the year of 1990, 2005 and 2015, the spatio-temporal dynamics of land use and ecosystem service were analyzed, and the impacts of LUCC on ecosystem services was quantified with the impact assessment model. The results showed that, from 1990 to 2015, farmland and construction land area, which covered more than 95% of the total area of the research area, changed the most in quantity as -104.38 and 201.59 km² respectively, while forestland, grassland and water area changed the most by 79.3%, -73.7% and -24.2%, respectively. The total value of ecosystem service continuously decreased by 1.005 billion yuan, among which the value of hydrolo-gical regulation service suffered the most. The value of ecosystem service (ESV) presented an increasing trend in the west and a decreasing trend in the east. Extending from the center of the city to the outside, the value of ecosystem services was “high-low-high” in the east to west direction. The rate of farmland and water area contributed more than 95% to the total ecosystem service value, which had the greatest impact. The main drivers for the changes of land use and ESV in Shangqiu were population pressure, economic growth, regional policy, and urban planning. In the urban and rural development planning of Shangqiu City, more attention should be paid to the protection of na-tural resources and rational adjustment of the land use structure to realize sustainable development based on the harmony of economy, society and environment.

Delineation of urban development boundary based on the combination of rigidity and elasti-city: A case of Yiwu City in Zhejiang Province, China.

QIU Si-qi, YUE Wen-ze

2018, 29(5):  1607-1616.  doi:10.13287/j.1001-9332.201805.016

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Under the background of rapid urbanization, we took the contradiction between the rapid urbanization and resource environment protection as the starting point, conducted some theoretical research on urban growth boundary. Based on the definition of urban development boundary, we took Yiwu City, Zhejiang Province as a typical instance. Firstly, this study delimited the ecological boundary as ecological basic constraint area, using the methods of ecological red line discrimination and ecological sensitivity evaluation. Furthermore, the MCE-CA model was used in simulating the city size in 2020, making some adjustments to the moderate and low ecological-sensitive areas in the eco-sensitivity assessing, and delimiting the size of urban growth boundary and elastic control zones. The results showed that the ecological constraint area with a total area of385.2 km² and outside of the ecological boundary was the security line of urban development and construction. The urban growth boundary with a total area of 163.3 km² was not only the spatial boundary that could be constructed now, but also could meet the future development and construction. The district between the ecological boundary and urban growth boundary was an elastic control zone, in which urban development activities were allowed, but the size of construction could not exceed 8.5% of the total urban development boundary area. Our results delimited the urban development boundary under the rigidity and elasticity, which could guide the urban space development and provide a theoretical reference for China.

MODIS-driven estimation of regional evapotranspiration in Karst area of Southwest China based on the Penman-Monteith-Leuning algorithm.

ZHONG Hao-zhe, XU Xian-li, ZHANG Rong-fei, LIU Mei-xian

2018, 29(5):  1617-1625.  doi:10.13287/j.1001-9332.201805.014

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Karst area in southwestern China is characterized with complex topography, low soil water capacity, and fragile ecosystem. Accurate estimation of regional evapotranspiration is essential for ecological restoration and water resources management in southwestern China. Based on observed evapotranspiration and meteorological data, this study aimed to estimate spatial upscale evapotranspiration using the MOD15A2 LAI and Penman-Monteith-Leuning (PML) model, within which the stomatal conductance and soil wetness index were optimized by the least-square method. The results showed that the modeled ET well fitted with the observations, with the determination coefficient, Nash efficiency coefficient and RMSE being 0.85, 0.75 and 1.56 mm·d^-1, respectively. The ET exhibited clear seasonality and reached to its maximum in summer, coinciding with vegetation phenology. The annual ET ranged from 534 to 1035 mm·a^-1, with strong spatial heterogeneity which highly related to the precipitation. Evapotranspiration may be affected by precipitation as well as land use types.

Effect of meteorological factors on design farmland drainage modulus.

ZHU Chun-huan, LI Jian-zhu, FENG Ping, WANG Xian-ling

2018, 29(5):  1626-1634.  doi:10.13287/j.1001-9332.201805.013

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Calculation of design drainage modulus is of great importance for the safety of farmland and reduction of waterlogging loss. We investigated the effects of main meteorological factors on design farmland drainage modulus by focusing on a closed farmland area in Ninghe District of Tianjin City. To resolve the problem of limited observation, the parameter sensitivity was analyzed according to mutual information and partial rank correlation coefficient aiming at the total runoff depth based on field observation experiment. The reasonable parameters were obtained by combining with soil water content and the relative variation of groundwater level. Then, a three-source runoff yield model coupling of excess infiltration and saturation was established to estimate runoff and design drainage modulus, and the effects of meteorological factors such as precipitation and evaporation on drainage modulus were analyzed. Results showed that summer precipitation significantly reduced and evaporation varied a little during 1960-2015. The corresponding drainage modulus decreased with the reduction of precipitation. When return period increased, the magnitude of the reduction in precipitation as well as the design drainage modulus increased. However, the effects of meteorological factors on design drainage modulus was generally inapparent. Thus, we concluded that the current drainage modulus is suitable for the study area.

Dynamics of nutrient concentration and microbial community composition during fine root decomposition in subtropical Mytilaria laosensis and Cunninghamia lanceolata plantations.

CHEN Ya-min, YU Zai-peng, WANG Min-huang, WAN Xiao-hua, LIU Rui-qiang, SANG Chang-peng, SONG Meng-ya, XIONG Jia

2018, 29(5):  1635-1644.  doi:10.13287/j.1001-9332.201805.033

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We conducted a 12-month fine root decomposition experiment under 19-year-old Mytilaria laosensis and Cunninghamia lanceolate plantations to explore the dynamics of nutrient concentration and microbial community composition. The aim of this study was to provide insights into nutrient cycling under plantations with different tree species. Our results showed that the initial concentrations of phosphorus (P) and potassium (K) were significantly higher in the fine root of M. laosensis than those in C. lanceolata, which significantly decreased with decomposition. Nitrogen (N) concentration in fine roots of both species increased with decay time. The variation of N concentration in fine root of C. lanceolata lagged behind that in M. laosensis. During the decomposition, magnesium (Mg) concentration in fine root of C. lanceolata showed no significant changes, but that of M. laosensis decreased at the initial decay stage and increased thereafter and was significantly lower than that of C. lanceolata at the 8th month. The ratio of fungi to bacteria (F/B) of both species decreased at the initial stage and then increased, with significantly higher F/B in fine root of M. laosensis than that of C. lanceolate after one-year decay. Redundancy analysis (RDA) showed that changes in N and K concentrations and C/N ratio explained 37.2%, 14.5% and 14.8% of the variations in microbial community composition of C. lanceolata fine root respectively. However, during the decay of M. laosensis fine root, concentrations of Mg and K were key factors, accounting for 35.9% and 17.6% of the variations in microbial community composition, respectively. We concluded that other nutrients beyond N, such as Mg, might also be an important factor affecting root decomposition in different tree species.

Screening and phosphate-solubilizing characteristics of phosphate-solubilizing actinomycetes in rhizosphere of tree peony.

XUE Dong, HUANG Xiang-dong, YANG Rui-xian, WANG Zu-hua

2018, 29(5):  1645-1652.  doi:10.13287/j.1001-9332.201805.035

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A strain PSPSA1 with strong phosphate-solubilizing ability was isolated from the rhi-zosphere of tree peony. This strain was identified based on morphological characteristics, physiological and biochemical experiments, and 16S rDNA sequence analysis. Furthermore, its genetic stabi-lity and phosphate-solubilizing characteristics were investigated. Strain PSPSA1 was identified as the actinomycete Streptomyces albireticuli and showed high genetic stability. The order of phosphate solubilization capacity (PSC) in different phosphorus-source culture media was calcium phosphate (158.5 mg·L^-1) > aluminum phosphate (139.9 mg·L^-1) > ferric phosphate (127.7 mg·L^-1) > lecithin (45.6 mg·L^-1). The PSC and pH were significantly negatively correlated in inorganic phosphorus solution, but were not correlated in organic phosphorus solution. When using different carbon sources, PSC was in the order of lactose > glucose > maltose > fructose > sucrose > starch > cellulose. For different nitrogen sources, PSC was in the order of peptone > ammonium nitrate > ammonium sulfate > potassium nitrate > urea. Using glucose as a carbon source and peptone as a nitrogen source, strain PSPSA1 achieved the highest PSC of 202.6 mg·L^-1. After incubated for 60 days, the available phosphorus content in soil with a single application of strain PSPSA1 increased by 68.2% compared with control, and the available phosphorus content in soil with mixed application of strain PSPSA1 and organic fertilizer increased by 76.7% compared with a single application of organic fertilizer. The results indicated that the strain PSPSA1 had a strong ability to dissolve insoluble phosphorus and its mixed application with organic fertilizer improved the phosphorus solubilization. Thus, PSPSA1 is a promising microbial resource for the production of high-efficiency biological phosphorus fertilizer.

Phyllosphere bacterial community structure of Osmanthus fragrans and Nerium indicum in different habitats.

SUN Hong, LI Hui, ZHAN Ya-guang, LI Yang

2018, 29(5):  1653-1659.  doi:10.13287/j.1001-9332.201805.036

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The diversity of phyllosphere bacteria is one of the hotspots in the research area of plant-microbial relationship. There are still a lot of controversies in the main factors influencing community structure of phyllosphere bacteria. In this study, the phyllosphere bacterial community structure of Osmanthus fragrans and Nerium indicum grown in three habitats was investigated based on high-throughput sequencing and the main driving factors were examined. The results showed that there was no significant difference in phyllosphere bacterial diversity between the two plant species grown in three habitats. For phyllosphere bacterial community of two plant species from three habitats, the dominant phyla were Actinobacteria, Bacteroidetes, Chlamydiae, Cyanobacteria, Firmicutes and Proteobacteria, and the dominant genera included Methylobacterium, Sphingomonas, Hymenobacter, Polaromonas and Spirosoma. The structure of phyllosphere bacterial community was influenced by habitats, host species identity and species-habitat interaction, among which habitat showed the strongest effect.

Effects of protease inhibitors on the activities of midgut proteases in Callosobruchus chinensis (Linnaeus) larvae.

FAN Yan-ping, CHENG Xiao-fang, WANG Hong-min, ZHANG Yao-wen, ZHANG Xian-hong

2018, 29(5):  1660-1666.  doi:10.13287/j.1001-9332.201805.040

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To clarify the effects of protease inhibitors on the activities of midgut proteases in Callosobruchus chinensis (L.) larvae, the inhibitory effects of four kinds of protease inhibitors on the activities of midgut proteases of C. chinensis larvae were examined in vitro and in feeding conditions with indoor artificial insect inoculation. The activities of total protease, trypsin-like enzyme and chymotrypsin-like enzyme in the midgut of C. chinensis larvae fed on artificial mung bean that contained different contents of mung bean types in inhibitor (MBTI) were examined. The results showed that those four protease inhibitors had significant inhibitory effects on the activities of total protease, trypsin-like enzyme and chymotrypsin-like enzyme in C. chinensis larvae. The inhibitory effect was more significant when the concentration was higher. Among those inhibitors, the inhibitory effect of 20 μg·mL^-1 MBTI on three kinds of enzyme activities was the strongest, with reduction of 62.5%, 41.2% and 38.7%, respectively. Ovomucoid inhibitor (OI) had the lowest inhibitory effect. The activities of three enzymes in the midgut were also inhibited by C. chinensis larvae fed with artificial mung bean containing different inhibitors. The activities of three enzymes increased with the prolongation of the instar after feeding, but they were significantly lower than that in control. The inhibitory effect of MBTI was the strongest. The inhibitory effect on the activities of total protease and trypsin-like enzyme was gradually enhanced with the increases of MBTI contents when C. chinensis larvae were fed with artificial mung bean with different contents MBTI. The inhibitory effect on chymotrypsin-like enzyme activity was not significant. When the content of MBTI was up to 20%, the activity of chymotrypsin-like enzyme was obviously inhibited.

Community structure of soil mites under Quercus variabilis forests in small watershed of karst area, Guizhou, China.

CHEN Hu, JIN Dao-chao, ZHANG Yan

2018, 29(5):  1667-1676.  doi:10.13287/j.1001-9332.201805.039

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To analyze the differences of community structure of soil mites between the rocky desertification environment and karst beech forests, we investigated the soil mites of Quercus variabilis forest in the Chaoying small watershed of Guizhou Province. Soil mites from 83 genera, 54 families, and 3 orders were collected in the four investigations of 2014. We analyzed the differences of genus numbers, individual numbers, individual density, Shannon diversity index (H), Margalef richness index (SR), Pielou evenness index (J), maturity index (MI) of predatory soil mites (Mesostigmata: Gamasina), community structure of the oribatid mites (MGP) and nutritional structure of mite. Results showed that Oribatida was dominant in taxonomic richness and individual abundance. Abundant genus, high individual density and diversity of soil mites were found in summer and autumn, and higher individual abundance was found in spring and autumn. Soil mites showed surface-aggregation in their distribution. Most predatory mites were K-selected in summer and r-selected in other seasons. The ecological groups of the oribatid mites were mainly P-type and O-type. Hypochthonius, Allobelba and Zygoribatula constituted the nutrient function group of the soil mites. There were significant differences in the main groups of soil mites in the beech forest and other forest types. Among all the groups, Parholaspididae, Laelapidae, Oppiidae and Haplozetidae with abundant genera composition, Multioppia, Parholaspulus, Scheloribates and Haplozetes with predominance could be used as a biological indicator for the soil environment in beech forests.

Degradation of nonylphenol in water by microorganisms immobilized on bamboo charcoal.

HUANG Qian, JIANG Meng-ying, WANG Li-xiao, LOU Li-ping

2018, 29(5):  1677-1685.  doi:10.13287/j.1001-9332.201805.032

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Bamboo charcoal is a high-quality biochar, with a large surface area, well-developed pores, and high mechanical strength. Therefore, it is one of the best choices of microbial immobilization carrier. In this study, the optimal preparation condition was examined for microorganisms immobilized on bamboo charcoal by the orthogonal test. The degradation effects of estrogen nonylphenol were compared between the bacteria immobilized on bamboo charcoal and free bacteria, and then feasibility of the reuse of immobilized bacteria was investigated. The results showed that lots of degrading bacteria could adhere to the surface and internal pores of bamboo charcoal. The optimum conditions for the preparation of immobilized microorganisms were as follows: 30 ℃, pH=7, 35-mesh bamboo charcoal. The degradation rate of nonylphenol was in good agreement with the first order kinetics equation. When the initial concentrations of nonylphenol were 30, 50, 80 and 100 mg·L^-1, the degradation rates of nonylphenol of immobilized bacteria for seven days were 100%, 75.3%, 67.3% and 78.7%, respectively, which were significantly higher than those of free bacteria (54.2%, 51.5%, 30.6% and 23.5%). After eight rounds of reuse, the degradation rate for immobilized bacteria still reached as high as 36.5%, while it was only 8.9% for free bacteria. Our results indicated that the microorganisms immobilized on bamboo charcoal had long-term reusability, and thus had good prospects in the application of organic pollutants removal in wastewater.

Effects of Suaeda glauca planting and straw mulching on soil salinity dynamics and desalination in extremely heavy saline soil of coastal areas.

ZHANG Jiao, CUI Shi-you, FENG Zhi-xiang

2018, 29(5):  1686-1694.  doi:10.13287/j.1001-9332.201805.034

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To elucidate the seasonal variations in soil salinity and its driving factors, and to explore the effects of planting Suaeda glauca and straw mulching on soil desalination and salinity controlling, a field experiment was conducted in extremely heavy saline soil of coastal areas in Rudong, Jiangsu Province. There were four treatments: control (bare land, CK), planting S. glauca (PS), straw mulching A (at 15 t·hm^-2, SM-A), straw mulching 2A (at 30 t·hm^-2, SM-2A). Climate factors (including rainfall, atmospheric temperature, sunshine duration, and atmospheric evaporation) and soil salinity dynamic changes were determined from May 2014 to May 2015. Results showed that: (1) The seasonal variation of soil salinity was obvious in the bare ground (CK), with the lowest (8.69 g·kg^-1) during June-August and the highest (26.66 g·kg^-1) during September-December. The changes of soil salinity in topsoil (0-20 cm) were more intense than that in sub-topsoil (20-40 cm), with the changes in sub-topsoil having somewhat time lag compared the topsoil. (2) Soil salinity in CK treatment had a significantly linear correlation with the cumulative rainfall and evaporation-precipitation ratio of the fifteen-day before sampling. The results from multifactor and interphase analysis indicated that the increases of rainfall would promote soil desalinization. The rise of atmospheric temperature could exacerbate soil salt accumulation in surface soil. The interaction between rainfall and atmospheric temperature would have a positive effect on soil salt accumulation. (3) PS treatment did not alter the seasonal variation in soil salinity, but it reduced soil salinity in topsoil. (4) In SM-A and SM-2A treatments, the relationship of soil desalinization rate (%, Y) and treatment time (days, X) was expressed as Logistic curve equation. Moreover, the soil desalination rate was over 95.0% in the topsoil after 90-100 days of straw mul-ching treatment and was over 92.0% in sub-topsoil after 120 days of straw mulching treatment. The soil salinity in SM-A and SM-2A treatments fluctuated below 0.60 g·kg^-1 and 1.00 g·kg^-1, respectively in topsoil and sub-topsoil. Considering the desalination and economic costs, a suitable amount of straw mulching (such as 15 t·hm^-2) before rainy season was recommended, which would promote the soil desalinization and reclamation in extremely heavy saline soil of coastal areas.

Using sequential indicator simulation method to define risk areas of soil heavy metals in farmland.

YANG Hao, SONG Ying-qiang, HU Yue-ming, CHEN Fei-xiang, ZHANG Rui

2018, 29(5):  1695-1704.  doi:10.13287/j.1001-9332.201805.037

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The heavy metals in soil have serious impacts on safety, ecological environment and human health due to their toxicity and accumulation. It is necessary to efficiently identify the risk area of heavy metals in farmland soil, which is of important significance for environment protection, pollution warning and farmland risk control. We collected 204 samples and analyzed the contents of seven kinds of heavy metals (Cu, Zn, Pb, Cd, Cr, As, Hg) in Zengcheng District of Guangzhou, China. In order to overcame the problems of the data, including the limitation of abnormal values and skewness distribution and the smooth effect with the traditional kriging methods, we used sequential indicator simulation method (SISIM) to define the spatial distribution of heavy metals, and combined Hakanson index method to identify potential ecological risk area of heavy metals in farmland. The results showed that: (1) Based on the similar accuracy of spatial prediction of soil heavy metals, the SISIM had a better expression of detail rebuild than ordinary kriging in small scale area. Compared to indicator kriging, the SISIM had less error rate (4.9%-17.1%) in uncertainty evaluation of heavy-metal risk identification. The SISIM had less smooth effect and was more applicable to simulate the spatial uncertainty assessment of soil heavy metals and risk identification. (2) There was no pollution in Zengcheng’s farmland. Moderate potential ecological risk was found in the southern part of study area due to enterprise production, human activities, and river sediments. This study combined the sequential indicator simulation with Hakanson risk index method, and effectively overcame the outlier information loss and smooth effect of traditional kriging method. It provided a new way to identify the soil heavy metal risk area of farmland in uneven sampling.

Influence of land intensive use level on main atmospheric pollutants in the central urban area of Nanchang City, China.

LIANG Zhao-feng, CHEN Wen-bo, ZHENG Jiao

2018, 29(5):  1705-1714.  doi:10.13287/j.1001-9332.201805.031

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At present, urbanization has gradually changed from denotative expansion to connotative development in China. It is urgently needed for intensive use of land resources and the construction of “compact city”. However, intensive land use means less land resources to carry more urban elements, therefore people will become more and more sensitive to environmental pollution, especially atmospheric pollution. It is of great significance to study the influence of intensive land use on atmospheric pollution. Taking the central urban area of Nanchang City as a case, this study simulated the concentration of the six main atmospheric pollutants i.e. PM_2.5, PM₁₀, SO₂, NO₂, CO and O₃ by ordinary kriging interpolation firstly. Then, sixteen intensive land use variables, including the volume ratio, building density, population density, were analyzed with the partial least squares regression and path analysis in order to reveal the effects of intensive land use level on the atmospheric pollutants. The results showed that the correlations between intensive land use level and PM_2.5, PM₁₀ were the strongest, followed by O₃ and NO₂, and the weakest correlation was between intensive land use level and SO₂, CO. The sequence of the correlation between intensive land use variables and the six main atmospheric pollutants in different sample areas was residential area> education area > business area > industrial area. The more intensive the land use was, it had greater impacts on the atmospheric pollutants. The greatest effect was on PM_2.5 and PM₁₀, followed by O₃, and the least effect was on NO₂. The direct, indirect, and integrated influences of intensive land use on atmospheric pollutants were generally equal. Overall, the direct influence of the intensive land use level was greater than the indirect one, among which the influence of the intensive land use level of the residential area was the strongest, followed by the business area, and the education area least. This study provided a new perspective on studying the influence of intensive land use on atmospheric environment, which would provide some reference to solve the atmospheric problems in compacted city.

Reviews

Research advance in allelopathy effect and mechanism of terrestrial plants in inhibition of Microcystis aeruginosa.

ZHOU Li, FU Zi-shi, CHEN Gui-fa, PAN Qi, SONG Xiang-fu, ZOU Guo-yan, LIU Ya-qin

2018, 29(5):  1715-1724.  doi:10.13287/j.1001-9332.201805.038

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The inhibition of algae reproduction and control of harmful algal bloom are the primary challenges in the ecological restoration of eutrophicated water. It is urgent to inhibit algae over-reproduction in green and effective ways, one of which is the use of plant allelopathic effect. How-ever, few study focused on allelochemicals of terrestrial plants. Here, we introduced inhibition of Microcystis aeruginosa over-reproduction by allelochemicals from three categories of terrestrial plants, including herbaceous plants (Compositae/Papaveraceae, Liliaceae, Graminaceae), woody plants, and Chinese medicine plants. The classification, separation and identification of alleloche-micals from terrestrial plants that could be used for the inhibition of M. aeruginosa were summarized. Finally, the allelopathic mechanism to inhibit M. aeruginosa was discussed in detail to support the development of algistat. We also proposed some suggestions for the further development of algistat.