Table of Content

10 September 2018, Volume 37 Issue 9

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Soil cation exchange capacity and its main impact factors in the humic layer of broad-leaved Korean pine forest in northeast China.

TIAN Sheng-xian, FENG Pan, YANG Shan, LIU He-yong, YE Ji, LI Hui, JIANG Yong, ZHANG Yu-ge

2018, 37(9):  2549-2558. 

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Broad-leaved Korean pine (Pinus koraiensis) forest, a typical zonal vegetation in northeast China, harbors high biodiversity and is an important ecological resource. This study focused on the distribution of soil exchangeable cations Ca, Mg, K and Na, effective cation exchange capacity (ECEC), and exchangeable acidity as well as its main driving factors in the humic layer of the broad-leaved Korean pine distribution zone across nine degree of latitudes in northeast China. Results showed that the humic layer soils were biologically enriched with basal elements. The concentrations of soil exchangeable cations and ECEC had no obvious latitudinal variation. The concentration of exchangeable Mg and K were related with mean annual temperature or mean annual precipitation. Soil organic matter and pH were the two driving factors with positive effects on the distributions of base cations and ECEC. Soil exchangeable acidity was negatively correlated with ECEC and pH.

Factors affecting surface fuel load of Pinus tabuliformis forest in Songshan, Beijing. 

AI Ye-bo, CUN Ying-de, FAN Ya-qian, CHENG Rui-yi, LIU Yan-hong

2018, 37(9):  2559-2565. 

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Forest surface fuel is an important causing factor for forest fire. Understanding the impact factors of forest surface fuel load can provide scientific basis for forest combustible management. In this study, we conducted correlation analysis and stepwise regression analysis between surface fuel load and topographical, forest stand and ground cover factors ofPinus tabuliformis forest in Beijing Songshan National Nature Reserve. The contribution of those three types of factors to the changes of fuel load was calculated. Results showed that: (1) The total amount of surface fuel load had a significant relationship with the herb coverage. The live surface fuel load was significantly positively correlated with altitude and shrub coverage, but negatively correlated with herb coverage. The dead surface fuel load was significantly positively correlated with canopy density, stand density, and average tree height, but negatively correlated with altitude. (2) Results of multivariable linear regression analysis showed that altitude, canopy coverage, and shrub coverage were the most significant factors affecting the live surface fuel load. The dead surface fuel load was most closely related to altitude and canopy density. (3) Among the explanatory factors of live surface fuel load, the contribution rate was in order of ground cover factor>stand factor> topographical factor, with the interaction of ground cover factor and topographical factor being the most significant, followed by interaction of ground cover factor and stand factors. For the dead surface fuel load, the contribution rate was in order of stand factor> topographical factor> ground cover factor, with the interaction of stand factor and topographical factor being significant, followed by the interaction of stand factor and ground cover factor. Affecting factors depended on the types of surface fuel. Therefore, it is necessary to differentiate affecting factors in surface fuel management, forest fire prevention, and stand regulation.

Distribution patterns of aboveground biomass of tropical cloud forests in Hainan Island.

SHAO Xiao-li, CHENG Yi-kang, WANG Xi-xi, WANG Xu, WU Yong, HONG Xiao-jiang, FANG Yan-shan, LU Yong-quan, LONG Wen-xing

2018, 37(9):  2566-2572. 

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Plant biomass, one of the most important ecosystem functions of forests, plays fundamental roles in material cycle and energy flow. The diameter at breast height (DBH) and height of plants with DBH≥1 cm were surveyed in tropical cloud forests in Jianfengling Mt., Bawangling Mt. and Limushan Mt. With forest aboveground biomass (AGB) being calculated with an allometric model, we assessed variations in AGB across different plot sizes, DBH classes, and plant height classes in the three tropical cloud forests. Results showed that AGB in the three tropical cloud forests consistently changed across plot sizes, with the AGB being significantly higher in Jianfengling Mt. and Limushan Mt. than in Bawangling Mt., due to the influences of precipitation and air temperature. AGB of Jianfengling Mt., Bawangling Mt. and Limushan Mt. were mainly distributed in trees with DBH≥30 cm, accounting for 33.0%, 32.1% and 52.8%, respectively. For the patterns of AGB across height classes, AGB was mainly distributed in plants with height ≥7 m in Jianfengling Mt. and Bawangling Mt., accounting for 79.9% and 70.1% of total AGB, respectively. ABG in Limushan Mt., however, was mainly distributed in plants with height ≥9 m, accounting for 87.7% of total AGB. Changes in AGB across the three tropical cloud forests were consistent at different DBH and height classes, with AGB being mainly distributed in large trees.

 

Distribution characteristics and influencing factors of Tithonia diversifolia, an alien invasive plant species, in Yunnan Province, China.

ZHU Feng, WANG Si-hai, CHEN Jian, LI Ning-yun, WU Chao

2018, 37(9):  2573-2580. 

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Tithonia diversifolia, an alien invasive plant species, has quickly spread along roads in Yunnan Province, China. To better understand the distribution of T. diversifolia, we investigated its community distribution along roads and analyzed the influencing factors. T.diversifoliahas invaded the tropical, and southern, central and northern subtropical regions of Yunnan, which covered 71 counties. In contrast to its distribution 10 years ago, T.diversifolia definitely extended northward and to higher altitude. At higher latitude and altitude region, the distribution of T. diversifoliawas related to climatic factors. At lower latitude and altitude region, the distribution was mainly influenced by human disturbance. The habitat types along roads substantially influenced the establishment of T. diversifolia. Grassland, economic forest, and cropland habitats with low canopy cover facilitate its invasion, whereas natural and secondary forest habitats with high canopy cover could resist its invasion. Roads obviously promoted the dispersal ofT. diversifolia. Highergrade roads with heavy traffic were in favor of the dispersal of T. diversifoliathan lower grade roads. The dense network of highways advanced its invasive process. With the rapid deve lopment of highways, the invasion of T. diversifolia speeded up in Yunnan. Population dynamics should be monitored for warning the invasion of T. diversifolia.

Anatomical structure and environmental adaptability of Vaccinium hirtum Thunb. var.koreanum (Nakai) Kitamura.

ZHANG Min, WANG He-xin, XU Guo-hui, LOU Xin, ZHAO Li-na, YAN Dong-ling

2018, 37(9):  2581-2588. 

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Vaccinium hirtumThunb. var. koreanum (Nakai) Kitamura is a rare and protected plant species in China. It is mainly distributed in the southern part of the Changbai Mountains and grows in cliffs or the place between rocks where there is sufficient sunshine but with theextreme environment such as barren and dry land with cold and strong wind in winter. We know little about the anatomy and resistance of V. hirtumvar.koreanum. In this study, the conventional paraffin section was used to observe anatomical structure of roots, stems and leaves of V. hirtum var.koreanum, aiming to reveal the relationship between anatomical structure and environmental adaptability. The results showed that the conducting tissue of perennial lateral roots in V. hirtumvar.koreanum was well developed. The epidermis and cortical cells of capillary roots were bulky. There were abundant solid inclusions in endothelial cells. In addition, a large number of mycorrhizal fungi such as ericoid mycorrhizal fungi, dark septate endophytes and arbuscular mycorrhizal fungi were found in the capillary roots. These features would help roots absorb moisture and nutrients. There was a thick stratum corneum \[(10.74±0.89) μm\] on the surface of one-year stem. There were a large amount of solid inclusions in both cortical thick-walled cells and pith cells. The cortex had a special air cavity structure, whose thickness accounted for 30% of theradius of the stem. These characters are helpful for plants to improve their water retention and adaptationto low temperature. The phloem tissue in stem was well developed, which facilitates the transport of water and nutrients. Furthermore, the upper and lower surfaces of leaves were covered with a thick cuticle \[(2.06±0.75), (2.04±0.73) μm, respectively\], and the phloem tissue of the veins was well developed, which would be beneficial to drought tolerance and water absorption. In conclusion, the anatomical structure of V. hirtumvar.koreanum helps toexplain why it can survive in drought, cold, windy, hostile environment at the top of mountain in eastern Liaoning.

Effects of nitrogen application rates and soil water contents on ryegrass decomposition and nitrogen release in red soil.

YANG Wen-ting, WANG Xiao-wei, XU Jian-cheng, JIAO Qi-qi, LU Mei-juan, HUANG Guo-qin

2018, 37(9):  2589-2595. 

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Green manure returning is one of the main strategies of organic fertilization in cropland. External nitrogen and soil water content are important factors affecting the decomposition of green manure. An incubation experiment with two factors and three levels was conducted to investigate the effects of soil water contents (15%, 30%, 45%) and nitrogen (N) application rates (0, 60, 120 mg·kg^-1) on decomposition and N release rate of ryegrass (Lolium multiflorum Lam.) during returning into red soil. Under the same soil water content level, increased N fertilization rate did not promote the decomposition of ryegrass and inhibited the decomposition at 7-21 days, N application limited N release rate at 7-13 days after ryegrass returning. With the same N application rate, the increases of soil water content improved the decomposition rate of ryegrass and promoted N release rate during ryegrass returning. Increasing soil water content enhanced N release rate of ryegrass under ambient N condition compared to under N application in the late stage (57-91 days) of ryegrass returning. At the 91st day, the treatment with 45% water content and 60 mg·kg^-1 N application rate had the highest decomposition rate, being up to 0.889, while the treatment of 45% water content and 120 mg·kg^-1 N application rate had the highest rate of N released during ryegrass returning, being up to 0.885. The results of twoway ANOVA showed that soil water content had significant effects on the decomposition rate and N release rate of ryegrass. In conclusion, reasonable chemical N fertilization rate (60 mg·kg^-1) and soil water content (30%) could inhibit the decomposition and N release during the early stage, while increasing soil water content (45%) could accelerate decomposition and N release during the late stage, and thus improve N uptake and utilization of the succeeding crops.

Responses of Scirpus mariqueter andSpartina alterniflora tosimulated salt stress and salt-tolerance thresholds.

LI Wei, YUAN Lin, ZHANG Li-quan, ZHAO Zhi-yuan, LI Hui, ZHU Xiao-jing, PAN Jia-lin, CHEN Ya-hui

2018, 37(9):  2596-2602. 

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As one of the key environmental factors, salinity affects survival, growth, and distribution of salt marsh plants. Given the projected sea level rise and saltwater intrusion, coastal wetland ecosystems are subject to higher salt stress, thus shifting in structure and function. Here, we focused on two vascular plants, a native species Scirpus mariqueterand an invasive species Spartina alterniflora in the Yangtze Estuary, aiming to explore the survival, growth, and reproduction of these two dominant species under a series of salinity stress. The responses of S. mariqueterand S. alterniflorato salinity were compared, and the salinity thresholds for survival of both species were calculated. The results showed that: (1) Survival rate of both species decreased as salinity increased, whereas the survival rate of S. alterniflora surpassed that ofS. mariqueter under the same salinity (P<0.05). (2) Growth of both species was significantly curtailed by increasing salinity (P<0.05); plant height, aboveground and belowground biomass of S. mariqueterdecreased as salinity increased, but those of S. alterniflora increased first then decreased when salinity reached >10‰. (3) Number of tillers and percent seed setting of both species decreased as salinity increased, suggesting an inhibited reproductive potential as affected by salinity; (4) S. mariqueter (with a salinity threshold of 21‰) was more susceptible to salinity than S. alterniflora(a salinity threshold of 43‰); (5) Being more salt-tolerant, the invasive S. alterniflora would overwhelm the native S. mariqueter under scenarios of sea level rise and saltwater intrusion.

Effects of ecological water conveyance on the composition, diversity and stability of plant community in the lower reaches of Tarim River.

XU Qiao, YE Mao, XU Hai-liang, WANG Xi-yi, ZHAO Xin-feng

2018, 37(9):  2603-2610. 

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The maintenance of structure and stability of plant community is of importance for environmental protection in arid areas. In this study, the characteristics of plant communities along four sections in the lower reaches of Tarim River were investigated using transect methods. The survey data in 2000, 2004, 2008, 2012, and 2016 were used to examine the changes of plant species composition at different distances from the river. Moreover, Shannon index, Alatalo index and ecological dominance were selected to analyze species diversity and evenness. The results showed that species richness increased from 17 to 31 with the implementation of the ecological water conveyance. The proportion of trees and shrubs declined, and the proportion of understory herbaceous species increased, resulting in more balanced collocations of treeshrub grass. In general, the Shannon index and Alatalo index of plant community increased significantly, while the ecological dominance decreased, indicating that plant communities were more speciesrich and homogeneous. The stability of plant community has increased gradually since the beginning of ecological water transport, but it is unstable.

Response of vascular structure of a lakeside dominant plant species Hippuris vulgaris L. to simulated warming in Napahai wetland of Northwestern Yunnan.

GUAN Dong-xu, TIAN Kun, WANG Zhi-bao, ZHANG Yi-nan, FENG Chun-hui, SUN Mei

2018, 37(9):  2611-2618. 

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Vascular structure is the main transport structure of plants, which plays an irreplaceable role in the processes of plant photo-accumulation, growth and development, adaption to changes, reproduction and dispersal. Temperature is an important environmental factor affecting vascular structure. How temperature affects the vascular structure of wetland plants, however, is not well understood. In this study, we studied the responses of vascular structure of a lakeside dominant plant species Hippuris vulgaris L. to simulated warming, by using open-top growth chambers (OTCs) in Napahai basin. Napahai basin is a typical plateau wetland in Northwestern Yunnan and belonged to the temperature-sensitive area. The results showed that warming had greater effects on the vascular structure of the aboveground stem, but had less influence on that of the underground stem. For the aboveground stem, warming significantly promoted the number and size of catheters and screens, and the size of vascular bundle, but with minor effects on the density of catheters and screens. In contrast, warming significantly reduced the size of conduits and screens in underground stem, but both traits didn’t show significant differences between the two warming treatments. Warming had no effects on other traits of vascular structure in underground stem. The mean annual temperature (MAT) and mean daily temperature (MDT) were the main factors affecting vascular traits, both of which had positive correlations with all the vascular traits. Our results indicated that climate warming obviously affected the transmission capacity of vascular structures of lakeside dominant plants in the plateau wetland of Northwestern Yunnan, which may lead to changes in physiological functions of plants and thus facilitate plant adaption to the warming environment.

Characteristics of moss bog plant community and interspecific relationships of dominant species in Niangniang mountain wetland, Guizhou.

CUI Hai-jun, ZHANG Yong, ZHANG Yin-feng, TIAN Kun, XIAO De-rong, WANG Kai, GUO Ying, LI Long-jiang

2018, 37(9):  2619-2626. 

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Plant community monitoring can provide theoretical guidance for the scientific management of wetland parks. We compared plant community characteristics between Sphagnum bog and Polytrichum bog and explored the interspecific relationships of dominant species and the mechanism underlying community composition. The results showed that characteristics of plant communities in Polytrichum bog showed a good efficiency of natural recovery, with the recovery of community composition and structure. The dominance of Polytrichum commune had a quadratic curve relationship with that of Pteridium aquilinum, in that P. aquilinumwith lower dominance (less than 40%) promoted the growth of P. commune and higher dominance (more than 40%) inhibited the growth of P. commune. P. aquilinum had an advantage of light competition, inhibited the growth of graminoid and forb species, and then significantly affected plant community diversity. Forb species played an important role in the maintenance of plant community diversity. In wetland park management, reasonable control of P. aquilinum growth is conducive to wetland water conservation function and plant diversity conservation.

Effects of phospholipase Dδ and 9-lipoxygenase on jasmonic acid synthesis and seed germination ofArabidopsis thaliana under drought stress.

CHEN Lu, LIU Bo, AN Yan-huang, ZHAO Min, WANG Yue-xuan, YANG Ning

2018, 37(9):  2627-2636. 

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Using Colombia wild Arabidopsis thaliana (WT), phospholipase Dδ (PLDδ) deletion mutant (pldδ) and 9-lipoxygenase (9-LOX) deletion mutants lox1 and lox5 seedlings as materials, we examined the effects of PLDδ and 9-LOX on biosynthesis of jasmonic acid (JA) and seed germination ofA. thalianaunder drought stress (0.3 mol·L^-1 mannitol). The results showed that drought stress markedly increased the activities of PLD and LOX and the gene expressions of PLDδ and LOX1. Under drought stress, the LOX activity and JA content in pldδ seedlings were significantly lower than those in WT. Both LOX and JA significantly increased after phosphatidic acid (PA) addition and were higher than those in WT. Drought stress significantly inhibited seed germination of pldδ, lox1 andlox5 mutants, with the strongest inhibitory effect on lox1. Under drought stress, the enhancement of PLD activity was related to PLDδ expression while the increasing activity of LOX was related to LOX1 andLOX5 expressions, with the dominant role from LOX1. PLDδ/PA was located at the upstream of 9-LOX and involved in the JA synthesis. All PLDδ, LOX1 and LOX5 participated in seed germination of A. thaliana under drought stress, with a dominant role of LOX1 in this process. Both PLDδ and 9-LOX were involved in PA and JAmediated seed germination.

The effect of compound inoculation of Suillus luteusand Trichoderma virens on the interannual changes of the bioactivity ofPinus sylvestris var.mongolica rhizosphere.

YIN Da-chuan, QI Jin-yu, SONG Rui-qing

2018, 37(9):  2637-2641. 

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To investigate the effects of compound inoculation on interannual changes of bioactivity of Pinus sylvestris var.mongolica rhizosphere soil, a pot experiment was carried out to examine the interannual variations of soil enzyme activities (catalase, urease, and alkaline phosphatase), the quantity of microorganisms (bacteria, fungi, and actinomycetes), and soil nutrient concentrations (total nitrogen, available phosphorus and available potassium) in the rhizosphere of P. sylvestris var. mongolica seedlings after inoculated with ectomycorrhizal fungi Suillus luteus N94 and Trichoderma virens T43. The results showed that the compound inoculation of N94 and T43 exhibited a synergistic effect, with the soil enzyme activities, microbial quantity, and soil nutrients of rhizosphere being enhanced. All measured variables (except for total soil nitrogen in 2013) performed better in the compound inoculation treatment than in the single inoculation treatment. Such better performance consisted, but with significant interannual variations. Our results provide a reference for improving soil biological activity of probiotics and the growth of seedlings.

Effect of the endophytic fungus Piriformospora indicaon the growth and drought tolerance of rice seedling under drought stress.

WEI Qiao, WU Mei-yan, ZHANG Wen-ying, XU Le, CHEN Jian-fang, PAN Rui, TIAN Xiao-hai

2018, 37(9):  2642-2648. 

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By Petri dish culture, an experiment of simulated drought stress was carried out by 20% polyethylene glycol (PEG 6000), to examine the effects of endophytic fungus (Piriformospora indica) on the growth and drought resistance of upland rice. The results showed that the biomass of rice seedlings significantly increased after colonization with P. indica for 23 days, with two-folds in total root length and total root surface area, and four-folds in the number of root tips. Under 20% PEG drought stress, the progress of leaf wilting and curling was slowed down, and the leaf temperature raised in the treatment with P. indicainoculation. With the extension of drought stress duration, the difference of leaf temperature in the treatment with P. indica inoculation was greater than that in the non-inoculated treatment. The expression levels of responsive genes related to drought stress, including OsMYB2, OsCIPK3,OsCDPK7 and OsCATB, were up-regulated in leaves of upland rice induced by P. indica with the extension of drought stress duration. In conclusion, P. indica inoculation could promote the growth and enhance the drought tolerance of upland rice.

Diversity of Acidobacteria in rhizosphere soils of common trees in Wuxi.

WEI Zhi-wen, LI Yun-ya, JIANG Wei, LIAO Xiang-ru

2018, 37(9):  2649-2656. 

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We evaluated the effects of plant types and soil physicochemical properties on the distribution of Acidobacteria in the rhizosphere soil. Soil samples were collected from the mixed evergreen and deciduous forest of Mey Blossom Garden, Wuxi City. The Illumina MiSeq high-throughput sequencing technology was adopted to analyze the relative abundance and subgroup distribution of Acidobacteria. The results showed that Acidobacteria was the second most abundant bacterial group, accounting for 15.4%-28.78% of the total. We obtained 20 acidobacterial subgroups from seven soil samples. The Gp1, Gp2, Gp3, Gp4, Gp5, Gp6 were the dominant acidobacterial subgroups, accounting for 80.23%-94.85% of the acidobacterial sequences. Gp1, Gp2 and Gp3 were the predominant subgroups in the evergreen tree rhizosphere soils, while Gp4, Gp5 and Gp6 were dominant in the deciduous tree soils. The subgroup Gp14 was only found in the rhizosphere soils of evergreen trees, while Gp9, Gp18, Gp20 and Gp22 were merely found in the deciduous tree soils. The results indicated that the plant types could affect the distribution of acidobacterial subgroups in rhizosphere soils. Among the soil physicochemical indices, the abundance of Acidobacteria was significantly influenced by total nitrogen content (P<0.05), and the distribution of soil acidobacterial subgroups was significantly affected by soil pH (P<0.01). The results suggested that the acidobacterial community composition and diversity were predominantly affected by soil pH, total nitrogen content, and tree types. Soil pH was the key factor influencing acidobacterial diversity.

Influences of EM application with organic material input on soil physicochemical properties and peach photosynthetic characteristics.

WANG Zhi-yuan, ZHANG Guang-na, YU Jun-xiang, ZHENG Ya-qin, CHEN Xiu-hui, GUAN En-hua

2018, 37(9):  2657-2662. 

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To examine the effects of effective microorganisms (EM) application with straw cover and organic fertilizer on soil physicochemical properties and peach photosynthetic characteristics, three treatments including EM-organic fertilizer (EM-O), EM-straw cover (EM-S) and control (CK) were employed in a latematuring peach orchard in Linyi City, Shandong Province. Soil physicochemical properties (soil bulk density, porosity, organic matter content, and available nutrient content) and chlorophyll content were measured. Results showed that EM-O and EM-S treatments significantly increased soil NH₄⁺-N, NO₃^--N, resin-P, available K and soil organic matter contents. Higher soil capillary porosity was found under EM-S treatment. EM-S treatment significantly increased chlorophyll a content in peach leaves. Results of stepwise multiple linear regression analysis between peach photosynthetic characteristics and soil properties showed that soil available K content was positively related with chlorophyll a content and total chlorophyll content. In conclusion, application of organic materials with EM substantially enhanced the contents of soil available nutrients, especially in 10-20 cm layer. Soil available K content had greater effects on chlorophyll content than soil organic matter, available N and available P contents.

Effects of maize cropping patterns on microbial properties in cinnamon soil.

ZHANG Gui-zong, CAI Qian, BAI Wei, LIANG Wen-ju

2018, 37(9):  2663-2671. 

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Soil microbial community composition and enzyme activities are the important and sensitive indicators of soil fertility. We investigated the effects of different cropping patterns of maize on microbial properties of cinnamon soil in northwest Liaoning. There were four treatments, including cropping patterns of equal row space (DHJ, control), double row with one space (EBK), triple row with one space (SBK), and double row at wide ridge (DLSH). The results showed that bacteria dominated in all treatments. The abundance of total PLFA, bacteria, arbuscular mycorrhizal fungi, gram-positive bacteria (G⁺ bacteria) and gram-negative bacteria (G^- bacteria) was significantly higher in SBK and DLSH than in DHJ and EBK. The activity of β-1,4-glucosidase, the abundance of saprophytic fungi (sap fungi) and the content of microbial biomass carbon (MBC) and alkali hydrolysable nitrogen (AN) were significantly higher in DLSH than in DHJ. However, the activity of acid phosphatase (AcP) was significantly lower in DLSH than in DHJ. The correlation analysis indicated that AN was positively correlated with sap fungi abundance (P<0.01) and negatively correlated with acid phosphatase activity (P<0.05). The high abundance of sap fungi in DLSH would be beneficial to excreting β-1,4-glucosidase (BG) and increasing MBC and AN content, thereby promoting soil carbon and nitrogen cycling and maize productivity.

Effect of chemical fertilizer nitrogen substitution by biogas slurry on the growth and quality of rice.

WANG Gui-liang, KOU Xiang-ming, ZHANG Jia-hong, WANG Shou-hong, XU Rong, HAN Guang-ming, TANG He-jun, ZHU Ling-yu, BI Jian-hua, WU Lei-ming

2018, 37(9):  2672-2679. 

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A field experiment was conducted to examine the effects of different rates of chemical fertilizer nitrogen substitution by biogas slurry on rice growth (development progress, plant height dynamic, population dynamic, and dry matter accumulation dynamic), yield, quality, and heavy metal content. The results showed that when the amount of nitrogen input was same, rice growth indices and yield first increased and then decreased with increasing rates of chemical fertilizer nitrogen substitution by biogas slurry, with rice growth indices and yield under the treatment with 70% chemical fertilizer nitrogen substitution by biogas slurry (70%Nbs) being the highest. Biogas slurry could improve rice quality. With the increases of the proportion of biogas slurry application, the contents of Cu, Zn, Pb and As in grains increased slightly, while the contents of Cd and Cr in grains decreased slightly. The contents of heavy metals in grains of all treatments were lower than the critical levels of contaminants in foods (GB 2762-2005). Compared with the treatment of chemical fertilizer application alone (Ncf), the rice growth indices in the treatment with 100% chemical fertilizer nitrogen substitution by biogas slurry (100%Nbs) decreased, with a risk of yield reduction. The treatment with 200% chemical fertilizer nitrogen substitution by biogas slurry (200%Nbs) could lead to rice lodging and yield reduction and increase the risk of secondary pollution, due to the prolonged growth duration and the increased basal internode length. Therefore, the optimal proportion of chemical fertilizer nitrogen substitution by biogas slurry was 70%, with the biogas slurry application level of 278.56×10³ kg·hm^-2.

Influence of enclosure on the diversity of large soil animal community in a degraded typical steppe of Inner Mongolia.

LU Kai-liang, TENG Yue, LI Jun-lan

2018, 37(9):  2680-2689. 

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To understand the influence of enclosure duration on diversity of large soil animals in degraded typical steppe of Inner Mongolia, the community composition of large soil animals at soil depths of 0-10, 10-20, and 20-30 cm in the enclosing 32 years plot (A), 19 years plot (B) and grazing grassland (C) were investigated in the Inner Mongolia Grassland Ecosystem Research Station, Chinese Academy of Sciences. A total of 984 individuals from 39 groups, belonging to two phyla, four classes and nine orders, were collected. The dominant groups were Carabidae, Chrysomelidae larva, and Cicadellidae for plot A; Cicadellidae, Carabidae, and Elateridae larvae for plot B; and Elateridae larvae, and Anthicidae for plot C. Species richness, Shannon index, evenness index and density-groups index were the highest in plot B and the lowest in plot C, while it was opposite for the dominance index. The numbers of individuals and groupsdecreased with increasing soil depth. Soil water content, pH, total phosphorus and organic matter contents were changed significantly (P<0.05) after exclosed, but no significant change was found in bulk density, porosity and total nitrogen content (P>0.05). The results of correlation analysis showed that the density, Shannon index and evenness index of large soil animals were significantly positively correlated with soil water (P<0.01). In conclusion, enclosure substantially influenced the horizontal and vertical distribution of large soil animals in the degraded typical steppes of Inner Mongolia, with greater numbers of individuals and groups than that in grazed plots. Moreover, enclosure is beneficial to the improvement of soil physicochemical properties.

Response of soil respiration to temperature and soil moisture under different land use types in a desert-oasis region, northwest China.

FU Li, ZHANG Yong-yong, ZHAO Wen-zhi

2018, 37(9):  2690-2697. 

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Clarifying the sensitivity of soil respiration to the variation of temperature and moisture in the desert-oasis region would be a great contribution to understanding soil carbon cycling in arid and semiarid areas. In this study, we measured soil respiration using LI8100 Soil Respiration Observation System as well as air temperature, soil temperature, and soil moisture under three different land use types (Haloxylon ammodendron plantation, oasis cropland, and poplar plantation) in a desert-oasis region of Northwest China. The annual mean soil respiration was in order ofH.ammodendron plantation (0.40 μmol CO₂·m^-2·s^-1) < oasis cropland (1.61 μmol CO₂·m^-2·s^-1) < poplar plantation (2.20 μmol CO₂·m^-2·s^-1), which was mainly driven by soil organic carbon content. The relationship between soil temperature and soil respiration was fitted by the Lloyd-Taylor model. Soil respiration in all those ecosystems was more sensitive to lower temperature (non-growing season) than higher temperature (growing season). At yearround scale, soil respiration in the three ecosystems was positively correlated with soil temperature (P<0.01). Furthermore, soil respiration in the H. ammodendron plantation and oasis cropland was positively correlated with soil moisture (P<0.01). Soil respiration in the poplar plantation was positively correlated with soil moisture when it was below 6%, but was negatively correlated with soil moisture when it was above 6%. Our results provide basic data for soil carbon cycling in the desertoasis region.

Dynamics of soil CO₂ concentration and CO₂ efflux in non-growing season of the Yellow River Delta wetland.

WANG Xian-he, WANG Xiu-jun, HAN Guang-xuan, WANG Jun-yi, SONG Wei-min, YOU Zai-jin

2018, 37(9):  2698-2706. 

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To address the issue of lacking data in the non-growing season, we conducted anexperiment in a coastal wetland of the Yellow River Delta from October 29, 2016 to February 9, 2017, by continuously monitoring soil CO₂ concentration and temperature at different soil depths (15, 30, and 45 cm). In order to understand the dynamics of CO₂ efflux and to assess its relationship with soil CO₂ concentration, we measured CO₂ efflux in March 3-5 and March 16-18, 2017. The results showed that soil CO₂ concentration significantly increased with the increases of soil depth. At the same depth, soil CO₂ concentration was significantly higher in autumn than in winter. There was strong diurnal variation in CO₂ efflux, which was consistent with the variation of surface soil temperature. The temperature sensitivity coefficients (Q₁₀) of soil respiration were 3.49-3.74. There was a significant positive correlation between CO₂ efflux and soil CO₂ concentration or soil temperature. Using the derived relationships, we estimated CO₂ efflux for the non-growing season, and found that the three models produced similar magnitudes and variations, i.e., 0.44 to 0.57, -0.18 to 0.01 and 0.09 to 0.13 μmol·m^-2·s^-1 for the maximum, the minimum and the mean values, respectively. Our results demonstrated the effects of soil carbon transformation in nongrowing season on carbon cycling of the Yellow River Delta wetland.

Responsive sensitivity of nutrients in red soil profile to land use change.

PAN Bo, DUAN Liang-xia, ZHANG Feng, ZHANG Liang, YUAN Hong, WU Le-le, SHENG Hao

2018, 37(9):  2707-2716. 

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To understand the distribution of nutrients in soil profile and their responses to dramatic land use change, four adjacent land use systems, including natural forest, the resultantly converted Chinese fir plantation, Chinese chestnut orchard, and sloping cropland, were chosen. Those ecosystems were located at an identical landscape unit in the hilly region of Daweishan Mount, northeast Hunan Province. Soil samples of 0-100 cm were collected by soil auger with a 20 cm interval. The pH, soil organic matter, total and available macro-elements (total N, P, and K, and alkali-hydrolysable N, available P and K), medium elements (exchangeable Ca, Mg), and micronutrients (available Fe, Mn, Cu, and Zn) in each soil layer were analyzed. The sensitivity of soil nutrients in response to land use change was evaluated using the sensitivity index (SI). Results showed that the contents of soil organic matter and total N at 0-100 cm depth were reduced by 9%-55% and 28%-57%, respectively, while that of total P was increased by 0.3-52 folds following the conversion of natural forest to other land use types, indicating that dramatic human activities (such as fertilization) led to losses of soil organic matter and total N but an accumulation of P in soil profile. Compared with the soil total nutrient contents (with SI ranging from -0.6 to 1.5), available nutrient contents (SI: -0.8 to 51.8) were more sensitive to land use changes. The available P (SI: -0.8 to 51.8), K (SI: -0.5 to 2.9), Fe (SI: -0.6 to 3.1), and Cu (SI: -0.8 to 2.2) mainly presented positive responses to land use changes, indicating the enhanced availability of those nutrients in soil by land use change. The SI of available nutrients, including alkali-hydrolysable N, available P, K, Mn and Zn, in subsoil was generally higher than that in topsoil, implying that results focusing on the topsoil nutrients under various land use types cannot be simply extrapolated to the subsoil. Changes in subsoil nutrients (especially for available nutrients, medium nutrients, and micronutrients) caused by land use change should be received more attention.

The ecological health assessment based on species diversity and biotic integrity of fish for Nandujiang River, Hainan Island.

YU Fan-dong, GU Dang-en, TONG Yan-nan, LI Fang-yuan, SHEN Zhi-xin, ZHU Hai, PAN Xian-hui, ZHOU Kang-qi, MA Guang-ming, WANG De-qiang, HU Yin-chang

2018, 37(9):  2717-2726. 

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Based on data collected from fish resource survey in 2016-2017, we assessed fish species diversity and the health status of Nandujiang River, Hainan Island, China. The relative importance index (IRI), Pielou uniformity index, Margalef richness index and Shannon diversity index were used to evaluate fish biodiversity. Two sets of evaluation system constructed by the fish-based biotic integrity index (IBI) were used to assess the river health status. Results showed that there were 16 dominant fish species in Nandujiang River, including Oreochromis niloticu, Aristichthys nobilis, Toxabramis houdemeri, Hemiculter leucisulus and so on. The Margalef richness index showed the same temporal trend as the Shannon diversity index, being higher in the sampling points of the source and the estuary of Nandujiang River but lower in the middle section. In contrast, the Pielou uniformity index was higher in the sampling points of the middle section but lower in the source and the river estuary. The results of fishbased biotic integrity evaluation showed that most of the historical fish were preserved in the river. The percentage indicators changed from 0.2% to 10.5%, while the change of species number ranged from 0 to 4. Among all sections of Nandujiang River, the final score of middle section was only 19 points, which was much lower than that of other sections (36-46 points). In conclusion, Nandujiang River was healthy with respect to higher fish biodiversity and biotic integrity. Among different sections of the river, the source and estuary had better biodiversity and biotic integrity than the middle section.

Seasonal variation of phytoplankton and its relationship with environmental factors in sea waters near Taishan.

HE Rui, JIANG Ran, ZHU Xiao-ping, GUO Wei, LI Zhao-xu, XU Ning

2018, 37(9):  2727-2736. 

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To provide reference for the conservation of marine ecosystems near Taishan, seasonal variation of phytoplankton community and environmental factors in sea waters near Taishan were investigated from December 2015 to September 2016. A total of 113 species were identified, belonging to 64 genera and six classes. The most diverse group was the diatoms (67 species from 31 genera), accounting for 59.2% of the total recorded species, followed by dinoflagellates (18 species, 10 genera), which accounted for 15.9% of the total recorded species. Diatoms were predominant in species composition and cell abundance. Dinoflagellates and green algae were the second and the third major group, peaking in spring and summer, respectively. The annual average cell abundance of microalgae was 7.06×10⁵ cells·L^-1, peaking in spring (2.65×10⁶ cells·L^-1), followed by summer (6.3×10⁴ cells·L^-1), autumn (5.6×10⁴cells·L^-1), and winter (5.4×10⁴ cells·L^-1). The dominant species were Leptocylindrus danicus,Chaetoceros lorenzianus,Coscinodiscus radiates,Ditylum brightwellii, Skeletonema costatum, and Phaeocystis globosa. Among them,S. costatumwas dominant in all seasons. The annual averageShannon diversityindex, Margalef diversity index, Pielou evenness index were 2.98, 3.34 and 0.69, respectively. The effects of water temperature, salinity, pH, chemical oxygen demand (COD), nitrate and active phosphate on the phytoplankton community structure varied among different seasons. Salinity, pH and nitrate were the driving factors of cell abundance peak in spring.

Relationship between epiphytic seaweeds and two seaweed-associated amphipods in mussel raft culture area.

LIU Shu-rong, ZHOU Xi-jie, ZHANG Shou-yu, CHENG Xiao-peng, XIANG Chen, WANG Kai

2018, 37(9):  2737-2744. 

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Seaweeds have various ecological functions in marine ecosystems. As for their conservation function, most studies have focused on their conservation effect on high trophic level, such as fish, gastropod, and mussel. However, little is known about the conservation effect of seaweeds on bait organisms. Here, we reported the conservation function of epiphytic seaweeds on seaweed-associated bait organisms such as amphipods in a raft musselculture area. Sampling was carried out in the raftmusselculture area of northwestern Gouqi Island in May 2017. A total of 32 species of epiphytic seaweeds were collected, belonging to three phyla:Rhodophyta,Phaeophyta, and Chlorophyta. Plenty of amphipods (mainly Gammaridea and Caprellidae) were observed attaching on the surface of the epiphytic seaweeds. The mean biomass of the amphipods attached on per gram of epiphytic seaweeds was 0.073±0.034 g (df=29,a=0.05), while their abundance reached as high as 7.63±4.07 ind·g^-1 (df=29, a=0.05). There were positive correlations between amphipod biomass and seaweed biomass (r=0.43,n=28,P<0.05) and between Gammarida abundance and seaweed biomass (r=0.50,n=28,P<0.01). Caprellidae abundance did not change with increasing seaweed biomass (r=0.26, n=28, P>0.1). The average individual size of Gammaridea significantly increased with seaweed richness (r=0.71, n=30, P<0.001), whereas there was no significant correlation between individual size of Caprellidaeand seaweed richness (r=-0.13, n=30, P>0.1). In conclusion, our results indicated that seaweeds are beneficial for the growth of seaweed associated Gammaridea and Caprellidae. The mechanisms of seaweed conservation effects on them are different, which may be related to the species specific functions of seaweeds and ecological habits of amphipods.

Single and synergistic effects of Ulva lactucaand Sesuvium portulacastrumon the purification of mariculture wastewater.

YING Rui, CHEN Jing-fang, GAO Shan-shan, LI Zu-fu, FENG Jian-xiang

2018, 37(9):  2745-2753. 

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We evaluated the single and synergistic effects of Ulva lactuca and Sesuvium portulacastrum on the purification of mariculture wastewater. The results showed that the water quality was significantly improved by U. lactuca with different planting densities after 12 days treatment. The treatment with a density of 2.0 g·L^-1 showed the highest removal rates of COD, inorganic phosphorus, ammonium nitrogen and total nitrogen, with values being 41.7% 76.9%, 81.8%, and 67.2%, respectively. Similarly, S. portulacastrum with different planting densities also significantly improved water quality after 12 days treatment. The planting density of 4.8 g·L^-1 had the highest removal rates of COD, inorganic phosphorus, ammonium nitrogen and total nitrogen, which were 49.0% 20.8%, 98.5%, and 55.9%, respectively. In the treatment with combined U. lactucaand S. portulacastrum, the removal rates of COD, inorganic phosphorus, ammonium nitrogen and total nitrogen reached 36.7%, 100%, 100.0%, and 88.8% respectively, indicating that their combination enhanced the purification ability. Our results suggest that both  U. lactuca and S. portulacastrumcan improve water quality, and appropriate planting density and suitable combination of plant species would promote the phytoremediation effects.

Influences of temperature on plasma corticosterone levels, immunobiochemical indices in Chinese soft-shelled turtle Pelodiscus sinensis and antibacterial effects.

SHEN Si-xian, SHI Yan, LI Wei, CHEN Chen, ZHU Xin-ping

2018, 37(9):  2754-2760. 

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We measured the levels of plasma corticosterone (CORT) from three samples of Pelodiscus sinensis (12, 18 and 24 months after hatching) under normal growth condition. The effects of different temperatures (10, 20 and 33 ℃) on CORT levels, immune biochemical indicators and antibacterial effects were examined, with (28 ± 2) ℃ (constant temperature) as control. The results showed a significant difference in CORT levels between 12 and 24month-old individuals (P<0.05). The CORT level in each group showed a tendency of first rising and then decreasing over time. The CORT level in the 10 ℃ and 20 ℃ groups was significantly different from the control after treated for four and six hours (P<0.05). The enzyme activity and protein content of each temperature treatment first increased and then decreased over time. There was no significant difference compared to the control (P>0.05). The antibacterial effect of plasma was negatively correlated with CORT level. Our results indicated that sudden changes in temperature caused stress response for P. sinensis, which increased the CORT level, changed the immune biochemistry, and reduce the antibacterial effect, with a negative effect on organism immunity.

Egg shape allometry and egg size number trade-off in the steppe racerunner (Eremias arguta).

LIANG Tao, SHI Lei

2018, 37(9):  2761-2767. 

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The trade-off between egg size and number is a key trait of life history. The physiological constraint hypothesis predicts that the energy storage of a female affects the energy allocation to individual egg. Nonetheless, the morphological constraint hypothesis proposes that female body size is linked to egg number and size. Here, we analyzed the morphological traits and reproduction-related parameters of the female Eremias arguta, to test the above hypotheses. Our results showed that egg width increased with the increases of female tail base width. Egg length, egg volume, and clutch size increased with the increases of axilla groin length. Both egg mass and number increased with increasing body condition index. A significantly positive relationship but no trade-off was found between egg size and number, indicating that females improve their reproductive outputs by increasing both egg size and number. An allometry existed between egg shape and female morphological trait, and the allometric slope of female morphological trait was steeper than that of egg shape. After the effect of clutch size being eliminated by calculating residual scores from the separate regressions of egg length and egg width on clutch size, there was no difference in the allometric slope between egg shape and female morphological trait. We found evidence that morphology of female E. arguta constrains egg size and number and females with a better body condition producing larger and more eggs. There is no trade-off between egg size and clutch size, and allometry in egg shape might be due to morphological constraints.

The composition and distribution of heritage trees in Guizhou ethnic minority areas: A case study of Wuchuan County.

TIAN Li-juan, HUANG Li, ZHOU Li-hua, CHEN Ting-yue, QIAN Shen-hua, YANG Yong-chuan

2018, 37(9):  2768-2775. 

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Heritage trees, important carriers of traditional culture, are important components of terrestrial biodiversity. Understanding species composition and distribution of heritage trees will provide valuable insights into heritage tree conservation. Here, we investigated the species composition and distribution of heritage trees in Wuchuan County, a minority autonomous county in Southwest China. A total of 5105 heritage trees were recorded, belonging to 79 species, 65 genera, and 38 families. The dominant families were Fagaceae, Lauraceae, Ulmaceae and Leguminosae. The dominant species were Cupressus funebris,Ginkgo biloba, Liquidambar formosana andPhoebe zhennan.Among those species, 10 were nationally protected species, including Ginkgo biloba, Liriodendron chinense, Taxus wallichianavar. chinensis, Liriodendron chinense and Nyssa sinensis.The majority of the heritage trees were concentrated in the DBH sizeclass of 50-100 cm, and the height-class of 18-26 m, and the crown sizeclass of 3-9 m. Heritage trees were mainly distributed at two types of topographic positions, with 50.49% in the valleys and 41.84% on the slopes. For habitats, 59.33% of the individuals were distributed in the villages, 13.82% were in the residential sides, and 12.14% were in the cemeteries. Heritage trees were generally well protected (more than 90% of the individuals are healthy ones). The most frequentlyoccurring damaged tree species were Cupressus funebris, Ginkgo biloba, and Cunninghamia lanceolata. Among the three species, C. lanceolata suffered the most severe damages.Overall, heritage trees in Wuchuan County with high conservation values were abundant and were relatively wellprotected.

Dynamics of tea planting areas in Anxi County based on CA-Markov model.

ZHENG Peng, LIN Hai-rong, ZHAN Xin, PAN Wen-bin

2018, 37(9):  2776-2785. 

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Anxi County is a representative and successful example of mountain tea economy. Understanding the spatial and temporal expansion of tea planting area in Anxi County is of great significance to the development mode of mountain tea economy in China. Here, we interpreted remote sensing images of Anxi County in 1991, 1998, 1999, 2006, 2007, 2010 and 2015, and analyzed the expansion of tea planting area at different periods. Land use change in 2015 was simulated using CA-Markov model and Logistic regression model. Compared with the interpretation data of 2015, Kappa coefficient of the simulated results was 0.787, indicating that the simulated results were credible. Then, land use change in 2020 was simulated. The results showed that the tea planting area in Anxi County showed gradual rise in three stages, which were from 1991 to 1999, 1999 to 2007 and 2007 to 2015. Overall, tea planting area changed slowly, and the land use dynamic index of tea plantations was 14.88%. Spatially, tea plantation area in Anxi County was expanded from the northeast to the entire county, and would further expand to the southwestern part, with the scattered smallarea tea plantations merging into some largearea plantations. Our results may provide guideline for planning layout of future teaplanting in the county.

Genotoxicity of rare-earth element cerium on zebrafish (Danio rerio) livers.

HE Yan-bin, TAI Pei-dong, SUN Li-zong, GUO Cheng, LIU Zhi-hong, CONG Shi-long

2018, 37(9):  2786-2793. 

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Cerium (Ce) is the most abundant rare-earth element. Using RAPD-PCR (random amplified polymorphic DNA-PCR) and MSAP-PCR (methylation-sensitive amplified polymorphism-PCR), the effects of Ce on genomic DNA damage and DNA methylation in zebrafish (Daniorerio) were examined. The results showed that, after the fish was exposed to different concentrations of Ce³⁺ (0, 5, 10 and 20 μmol·L^-1) for 28 days, Ce³⁺ was mainly enriched in the liver (bioconcentration factors BCF: 5.49-9.33), followed by gill (BCF: 3.58-4.49) and muscle (BCF: 0.13-0.25). The results of RAPD-PCR showed that Ce³⁺ (>10 μmol·L^-1) could induce DNA damage in zebrafish livers. The results of MSAP-PCR showed that the change rates of total genomic DNA methylation of zebrafish livers caused by Ce³⁺ stress were 8.93% (CK), 9.12% (5 μmol·L^-1), 15.56% (10 μmol·L^-1), and 28.83% (20 μmol·L^-1), respectively. The demethylation (D) of genomic DNA in zebrafish livers significantly increased under the low concentration of Ce³⁺, while the methylation (M) significantly increased under the high concentration of Ce³⁺. Meanwhile, the methylation polymorphism increased with the increases of Ce³⁺ concentration. Results from sequencing analysis showed that these specific bands had high homo logy with the genes of zinc finger protein STZ/ZAT10, ABC transporter 1, and cell cycle control phosphatase superfamily protein. Compared to RAPD markers, DNA methylation markers were highly sensitive to Ce³⁺ stress. These results contribute to our understanding of the biological effects of rare earth elements.

Remote sensing retrieval and spatial-temporal differentiation of land surface temperature in Guizhou Province.

HU Ze-yin, WANG Shi-jie, BAI Xiao-yong, LI Qin, WU Lu-hua, QIAN Qing-huan, XIAO Jian-yong, CHEN Fei, ZENG Cheng

2018, 37(9):  2794-2807. 

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Land surface temperature (LST) is a crucial parameter for global change investigation, which is significant to ecosystem and biogeochemical researches. However, studies on LST of complex terrain areas are limited. Guizhou Province is a typical karst landform with complex terrain and fragile ecosystems. Based on multi-year MODIS remote sensing data combined with meteorological data in Guizhou Province, the temporal and spatial changes of LST were studied by using correlation analysis, trend analysis, R/S analysis and geographic detector. The results showed that: (1) The MODIS LST displayed a linear correlation with near surface temperature; (2) LST showed a spatial distribution of the south-high and north-low; (3) The interannual fluctuation of LST was large with the maximum difference of 2.06 ℃·a^-1, while the annual variation was mainly in unimodal distribution; (4) LST decreased with increasing elevation in the regains with >800 m above sea level, and exhibited a nonlinear relationship with elevation in the regions with <800 m above sea level; (5) There were significant differences in LST among different land-use types, with a maximum difference of 1.3 ℃. In summary, the spatial distributions of LST in the study area were relatively consistent with that of latitude, which was impacted by elevation and latitude and was related to land-use types.

Risk zonation of chilling injury of Hevea brasiliensis in Hainan Island.

ZHANG Ya-jie, ZHANG Jing-hong, CHEN Sheng-bei, HUANG Hai-jing

2018, 37(9):  2808-2814. 

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Chilling injury is one of the main meteorological disasters to Hevea brasiliensis in Hainan Island. Risk zonation of chilling injury would effectively improve the prevention capability ofH. brasiliensis from chilling injury. With the meteorological data from 1964 to 2016, H. brasiliensis cultivation area, yield, and social economic data from 1988 to 2016, four factors of chilling injury (chanciness of disaster-causing factors, sensitivity of disaster inducing environment, vulnerability of disaster affected bodies, and capability of disaster prevention and reduction) were selected to construct the risk assessment model of chilling injury on H. brasiliensis based on the risk formation mechanism. The risk index of chilling injury to H. brasiliensis was calculated and five grades of risk were classified following the natural breakpoint method. The results indicated that the risk of chilling injury was higher in northwestern and central parts than in other coastal areas. Lingao area had the highest risk, followed by Wuzhishan mountain area in central part. The coastal areas of Dongfang and Ledong of southwestern parts, and Haikou and Wenchang in north part had the lowest risk. There was no chilling injury risk in Sanya and Lingshui.

Metacommunity theory and its application in community assembly of soil animals.

GUO Yu-xi, GAO Mei-xiang, LIU Jie, WU Dong-hui

2018, 37(9):  2815-2824. 

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A metacommunity is defined as a set of local communities that are linked by diffusion of multiple potentially interacting species. The fundamental issues of the metacommunity studies are the mechanism of multiple species coexistence in the same system and the causes and maintenance of biodiversity. To solve these classic questions, four classical paradigms of the metacommunity theory were proposed by Leibold, namely patch dynamics, species sorting theory, neutral theory, and mass effect. The metacommunity theory can be used in the field of soil animal research and to solve spatial distribution pattern and driving mechanism of soil animals at different spatial scales. This review sorted out the four core directions and research hotspots of metacommunity since 1992 by using biliometric analysis, such as the theory, structure, driving force and the mechanism of metacommunity based on functional traits. In addition, in combination with the current research status of soil animal community theory, we proposed further studies on spatial and temporal dynamics of soil animal diversity at multiple scales, aiming to provide technical support for the management of soil biodiversity.

The roles and extraction methods of extracellular polymeric substances in activated sludge wastewater treatment system.

LI Jin-pu, ZHANG Wen-wen, YANG Xin-ping

2018, 37(9):  2825-2833. 

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Activated sludge wastewater treatment system relies on microbial metabolism to clarify the sewage. Extracellular polymeric substances (EPS) of activated sludge play an important role in pollutants removal and the flocculation, settle ability and dewaterability of activated sludge, and thus affect the stability and improvement of the activated sludge process. Here, we review the role of EPS of activated sludge in wastewater treatment system and compare different extracting methods of EPS. The extraction methods can affect the EPS components and physicochemical properties of activated sludge. Researchers have tried to find the best compromise between high extraction yields and minimum cell lysis during the extraction procedure. Standardization of extraction methods is the foundation of the EPS related research. It is important to better understand the role of EPS in wastewater treatment system and improve the properties of activated sludge with research-specific extraction method of EPS.

Current situation, problems and breakthroughs of development and research of  sand sampler.

CHANG Zhao-feng, ZHAO Jian-lin, LIU Shi-zen, WANG Qi, SUN Tao

2018, 37(9):  2834-2839. 

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The observation of sand transportation flux is one of the main tasks in desertification monitoring, the research on sandstorm, aeolian sand flux and wind erosion. It is also one of the measures for eco-environment monitoring in arid desertified lands, with sand sampler being one of the main instruments. At present, there are many kinds of sand samplers. However, there are no observational standards and instruments for precise observation. In abroad, the collecting efficiency of sand samplers, as tested by the optical particle flow sensor and the isokinetic method, was below 70%. In China, the sand collecting efficiency of sand sampler was tested in the wind tunnel, and the collecting efficiency was 72%-89%. The bottleneck of developing sand sampler is how to make the velocity of the air flow in the sand sampler be equal to that in the field. The breakthrough is to invent sand sampler with the flow velocity inside being equal to that in the field. The active sand sampler is able to solve this problem. However, this kind of sand sampler is not yet applied due to power problems. It is needed to formulate a unified observation standard to improve the precise observation of sand samplers. Such an improvement will facilitate the examination of the real situation of sandstorm and aeolian sand flow, the comparison and analyzation of vertical and horizontal sand flow, and the promotion of research on desertification and sandstorm.

Selection of simulation models for seed dispersal of invasive plants by wind.

QUAN Wei, WANG Ming, SANG Wei-guo

2018, 37(9):  2840-2848. 

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Seed dispersal is an important pathway for the invasion of alien invasive plants. A clear understanding of dispersal mechanism is the basis for more effective prevention and ecological management of invasive species. Based on the analysis of the main parameters influencing the dispersal process by wind, we examined the effects of those parameters on different diffusion processes, summed up the influencing parameters which should be chosen in the simulation process of different diffusion, and explained the calculation of these parameters. Specially, we introduced the excellent simulation models of dispersal by wind and analyzed the selection basis of simulation models of dispersal in combination with the characteristics of invasive plants. Among all the influencing parameters, the height of seed release and the horizontal wind velocity have direct and obvious effects on the dispersal process by wind. For invasive herbs and shrubs, the height of plants in the invasive area is an important parameter that must be concerned. In the study of long distance dispersal, the effects of turbulence caused by leaf and horizontal wind profile within and above the canopy should be considered for trees and large shrubs. For small shrubs and herbaceous plants, the impacts of rising warm air mass caused by surface temperature should be concerned. Among the simulation models, the 2Dt model and the mixed Weibull model can more effectively describe the dispersal curves of the proximal and distal diffusers of the dispersal kernel. For more detailed selection of long-distance dispersal simulation models, it is necessary to consider different atmospheric turbulence types, disperser size, vegetation type, dispersal kernel dimension, and simulation accuracy requirements.

Application of decision tree post-classification comparison based on stable pixels in forestland change detection.

PANG Bo, WANG Hao, NING Xiao-gang

2018, 37(9):  2849-2855. 

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Forestland is the carrier and an important component of forest resources. How to accurately and quickly obtain information of forestland change is of important significance to monitoring and management of forest resources. In this study, we improved the training sample selection method in the decision tree classification to enhance the accuracy of forestland classification and change detection. The reliability of the improved method was tested with Yichun as a case. The results showed that the improved decision tree classification method outperformed traditional method with the accuracy of change detection being improved by 4.01%. Furthermore, the method improved the detection accuracy in regions with shadow, mist and arable land. Therefore, our method is more reliable for the detection of forestland changes.

The prediction model and its verification of potato late blight in northern China based on meteorological conditions.

LI Zhao, LIU Shu-tian, DING Jian, WANG Shuo-jin, HOU Xian-da, JIA Shu-gang, HOU Yan-lin

2018, 37(9):  2856-2861. 

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The occurrence or non-occurrence of diseases is a binary problem. Combined the data of late blight of potato in northern China and meteorological data, the classification model was used to explore the pathogenesis model of potato late blight. Three sample sets were created according to the distance between the weather station and the planting region. Considering the pathogenesis mechanism of late blight of potato, the meteorological data (a day length) and receiver operating characteristic curve (ROC curve) were used in the classification model to select the appropriate parameter threshold and the framework for late blight of potato. Then, the classification model was verified by historical data. The results demonstrated that the overall accuracy of the forecasting model was 78%, the sensitivity was 79%, and the specificity was 78% in the northern planting region.

Responses and modeling of canopy stomatal conductance of Platycladus orientalis to environmental factors in Hedong sandy land, Ningxia.

HAN Lei, HE Jun, QI Tuo-ye, TIAN Jia, SUN Zhao-jun, ZHAN Xiu-li

2018, 37(9):  2862-2868. 

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To understand the responses of forest canopy stomatal conductance to environmental factors and the underlying mechanism of canopy stomatal conductance controlling forest transpiration, the Granier thermal dissipation probe technology was used to monitor the sap flow of Platycladus orientalis, a typical tree species of protective forest in Hedong sandy land of Ningxia, from July to September. The microclimate variables were synchronously monitored. Based on sap flow, the continuous canopy stomatal conductance (g_c) was calculated by Penman Monteith equation. An improved Jarvis-Stewart stomatal model was used for simulating the changes of g_c. The results showed that the environmental variables such as saturated vapor pressure deficit (VPD), air temperature (T_a), relative humidity (RH) and solar radiation (R_s) were significantly correlated with g_c of P. orientalis (P<0.01). The magnitude of the influence of those factors on g_c wereT_a>R_s>VPD>RH. In sunny days, the relationships between g_c and VPD and between g_c and T_a were characterized by a hysteresis loop, with the response path being different from the rising stage to descending stage. Moreover, those relationships showed different response patterns at different time. The JarvisStewart model performed better in simulating the responses of canopy stomatal conductance to environmental factors R_s,VPD, and T_a. Results from cross validation showed that optimal parameter calibration of this model explained 84.4% of the total variation.