Table of Content

10 September 2019, Volume 38 Issue 9

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Small-scale spatial patterns of Kobresia humilis and Stipa purpureain typical plant communities from east to west across the northern Tibetan Plateau.

LI Xin-e, MENG Fan-dong, JIANG Li-li, ZHANG Li-rong, JIA Shu-gang, WANG Shi-ping, CUI Xia, Lü Wang-wang

2019, 38(9):  2577-2584. 

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The small-scale spatial pattern of plant species, such as aggregation, random and dispersion distribution, varies with environmental conditions, reflecting the ecological adaptation strategies of plant species. From east to west, it gradually transits from the semi-humid region of sub-frigid zone to the temperate arid region on the northern Tibet Plateau, with great variation of plant species diversity and species composition. From July to August 2012, eight typical grassland plant communities in different sites were selected from east to west in northern Tibet Plateau for field investigation. The species composition and species diversity of communities and smallscale spatial pattern of two populations of Kobresia humilisand Stipa purpurea were analyzed. The results showed that species richness and relative coverage of K. humilis were significantly positively correlated with precipitation. From east to west, the distribution of K. humilis changed from dispersion to random pattern, while that of S. purpurea changed from random to dispersion. There was a spatial segregation relationship between both populations with the lowest precipitation. Our results indicate that significant changes in small-scale spatial pattern of species are an important mechanism driving species coexistence in the communities along the transect on the northern Tibet Plateau.

Distribution and influencing factors of soil total nitrogen in alpine grassland of upper Yellow River.

GOU Zhao-jun, LI Ying-nian, LIU Feng-gui, CHEN Rui-jie

2019, 38(9):  2585-2594. 

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Alpine grassland is a unique ecosystem in the Qinghai-ibet Plateau, whose quality is determined by the distribution of total nitrogen content. Based on monitoring data, we analyzed the relationship between soil total nitrogen content and geographical factors of alpine grassland in the headwater region of the Yellow River. We used Geodetector to examine the effects of single or multiple geographical factors on the spatial distribution of soil total nitrogen. The results showed that: (1) There were obvious differences in total nitrogen content among different vegetation types, that is, Kobresia capillifolia meadow>K. pygmaea meadow>Stipa purpurea steppe>K. tibetica and Carex cinerascens meadow>Orinus kokonoricaStepp>S. aliena steppe>K. pygmaea and K. humilis meadow, which corresponded to meadow soil, chernozem, dark felty soil, alpine meadow soil and chestnut soil, respectively. (2) Soil total nitrogen content was positively correlated to altitude, slope, aspect, topography and vegetation type, and was negatively correlated to annual rainfall, ≥0 ℃ accumulated temperature, annual average temperature and soil type. Meanwhile, altitude, slope, and annual average rainfall functioned most with the coefficient 1, while the ≥0 ℃ accumulated temperature, annual average temperature, slope, vegetation, and soil type had coefficients of 0.72, 0.74, 0.59, 0.88 and 0.17, respectively. (3) The relationships between mean annual temperature, soil type, topography, and vegetation type, between topography, vegetation type and soil type, and between vegetation and soil type had nonlinear increasing effects on total nitrogen content, while the relationship among other factors had nonlinear decreasing effects. We conclude that the spatial heterogeneity of total nitrogen content is affected by the variety and complexity of environment factors.

Effects of heavy grazing on the interspecific relationship of main plant species and community stability in a desert steppe.

LIU Ju-hong, WANG Zhong-wu, HAN Guo-dong

2019, 38(9):  2595-2602. 

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Interspecific relationship is a characteristic of community succession, which is often represented by interspecific association. In this study, variance ratio method was used to calculate the overall association of the main plant species. Based on χ²test, association coefficient, percentage of co-occurrence, Ochiai index, and Dice index, the temporal stability and species asynchrony of plant community were calculated. The interspecific association of seven main species in a Stipa breviflora desert steppe was studied under no grazing and heavy grazing to understand the effects of heavy grazing on the interspecific relationship and community stability. The results showed that: (1) Under no grazing, the overall association was non-significant negative association among the main species. The proportion of negative association pairs (33.3%) was the largest. Under heavy grazing, however, the overall association was significant positive association. The proportion of positive association pairs (57.1%) was the highest. Heavy grazing changed the relationship of main species from competition to mutual facilitation. (2) Co-occurrence percentage, Ochiai index, and Dice index were all decreased under heavy grazing, indicating that the relationship between the main species was looser under heavy grazing than under no grazing. (3) The temporal stability and species asynchrony of the community under heavy grazing areas decreased, indicating that plant community was in a relatively unstable state with heavy grazing. The effects of heavy grazing on community stability were closely related to the change of interspecific relationship. The closer the interspecific relationship was, the more stable the community was.

Carbon, nitrogen and phosphorus stoichiometry in the coarse roots of 45 desert plant species in relation to environmental factors across the deserts in Xinjiang.

HE Mao-song, LUO Yan, PENG Qing-wen, YAN Zheng-bing, YANG Si-qi, LI Kai-hui, HAN Wen-xuan

2019, 38(9):  2603-2614. 

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We explored the relationship between C, N and P stoichiometry of coarse roots in 45 species of desert plants and environmental factors from 44 sites in Xinjiang. The results showed that coarseroot C, N and P concentrations of these species were 440±73, 9.86±3.84, and 0.82±0.48 mg·g^-1, respectively, and C∶N, C∶P and N∶P averaged 51±21, 707±388, and 15±10, respectively. Significant differences in nutrient concentration existed among three plant lifeforms. Specifically, coarseroot C concentrations decreased in the order of trees, shrubs and herbs, while root P showed an opposite trend. The coarse-root N concentration was the highest in shrubs. Only C vs P and N vs P in roots showed allometric growth relationships, with power exponents being -0.460 and 0.699, respectively. There were nonlinear relationships of coarse-root C, N and P with longitude, latitude, mean annual temperature (MAT), and mean annual precipitation (MAP). In comparison with life-form and soil nutrient content, climatic factors (MAP, MAT) had greater effects on the stoichiometric characteristics of C, N and P in the coarse roots of desert plants, which reflects water limitation for plant growth in deserts.

Phenotypic traits of Bromus inermis on the northern slope of Tianshan Mountains.

GONG Ke, JIN Gui-li, LI Chen-jian, YUE Yong-huan, WANG Hui-ning, HAN Wan-qiang

2019, 38(9):  2615-2621. 

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To reveal the phenotypic variation of Bromus inermis, we analyzed 13 phenotypic traits of 450 Bromus inermis individuals collected from five regions on the northern slope of Tianshan Mountains. The results showed variation in phenotypic traits of Bromus inermison the northern slope of the Tianshan Mountains, but with small coefficient of variation (0.294).  The variation of phenotypic traits among regions was greater than that within regions. The variation of phenotypic traits in the middle section of the northern slope of the Tianshan Mountains was significantly different from that in the eastern and western sections. The variation in the middle section increased with altitude, whereas that in the eastern and western parts showed an opposite pattern.  The 13 traits had a wide range of variation among regions, with the variation of tiller number being the largest. The trait indicators were positively correlated with the longitude and latitude. The mean annual temperature and mean annual precipitation were significantly correlated with a few traits such as ear length and root length.  The differences in phenotypic traits among regions were mainly presented in the reproductive branch height, spike length, leaf length and leaf width.  There was a large plant stature in the middle section of the northern slope of the Tianshan Mountains, and the large plant stature mainly came from the low altitude. In summary, climate in the middle section of the northern slope of the Tianshan Mountains was more suitable for the growth of Bromus inermis. The growth of Bromus inermis at low-altitude was better than those of the other two altitudes.

Vertical distribution and physiological senescence characteristics of fine roots in Castanopsis hystrix Miq. plantations at different ages.

WU Min, DENG Ping, ZHAO Ying, ZHONG Dao-fa, ZENG Ling-xin

2019, 38(9):  2622-2629. 

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The vertical distribution, morphology, biomass and aging physiological indicators of fine roots of Castanopsis hystrix Miq.in different ages (7, 14 and 25 years old) and soil depths (0-20 and 20-40 cm) were examined using soil coring method, to better understand the tree growth and development and thus provide scientific basis for sustainable management of C. hystrixplantations. C. hystrixplantations were selected in the Guidong and Guinan, Guangxi Zhuang Autonomous Region. The results showed that fine root length density, root surface area density, biomass, specific surface area, vigor and the contents of soluble sugar and soluble protein of fine roots in the same soil layer significantly increased with the increases of stand age, while specific root length, the contents of free proline and malondialdehyde (MDA) of fine roots significantly reduced. Under the same stand age, specific root length, specific surface area, vigor and the content of osmotic adjustment substances of fine roots enhanced with increasing soil depth, while root length density, root surface area density, biomass and MDA content of fine roots significantly decreased. The interaction between stand age and soil layer had a significant effect on biomass, the contents of soluble sugar, soluble protein and MDA of fine roots. There were significant positive correlations between root length density, root surface area density and fine root biomass and soil factors. In contrast, a significant negative correlation was found for free proline content of fine roots and soil factors. Meanwhile, vigor, soluble sugar and soluble protein content of fine roots were significantly positively correlated with soil water content and available nitrogen concentration. Fine roots of young forest (7 years old) were more prone to senescence, followed by 14 years old stand, and then 25 years old stand. Furthermore, fine roots in the topsoil (0-20 cm) had high metabolism, fast turnover rate and short lifespan.

 

Characteristics of different forest communities invaded by Ageratina adenophora in central Yunnan, China.

SONG Zi-ling, PENG Ming-jun, WANG Chong-yun, PENG Ming-chun, LI Zi-gang, ZHU Shou-yin, PENG Xiao-chang, LIU Peng-ju

2019, 38(9):  2630-2637. 

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Invasion of exotic species Ageratina adenophora into forest communities has great impacts on species diversity. Here, we examined the relationships between A. adenophora invasion and the species diversity of different forest communities in Haikou Forest Farm, Kunming City, Yunnan. Our results showed that the coverage and species abundance of native plants in the tree layer were significantly negatively related to the height and coverage of A. adenophora, and the invasion was not related to that of shrub and herb species, suggesting that the tree layer exhibited greater effects on the invasion of A. adenophora. According to the CCA, the forest communities in this area could be divided into two groups: (a) natural forests and secondary forests with less disturbance, and (b) plantation forests and secondary forests with stronger disturbance. The distance from the roads of the forests was a major factor affecting the distribution of A. adenophora. The importance value of A. adenophora showed a nonsignificant difference between the two groups. In addition, the importance value of A. adenophora was negatively correlated with the Simpson dominance index, Pielou evenness index, and Alatatlo evenness index, but was not correlated with the Shannon index. Therefore, A. adenophora’s invasion had notable impacts on the species diversity of the invaded forest communities. The primary forests had relatively high resistance to the invasion of A. adenophora, which was also related to the comprehensive characteristics of the communities, the distance from the roads, and the degree of human disturbance.

Stoichiometry of topsoil in Malus sieversii community in Xinjiang, China.

MA Zi yi re a·NUERHAILATI, TAO Ye, ZHOU Xiao-bing, ZHANG Yuan-ming

2019, 38(9):  2638-2647. 

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Malus sieversiiis a Tertiary relict tree species and valuable resource of wild fruit tree. In recent years, M. sieversii community is undergoing serious degradation. Whether the degradation of plant community would lead to change in soil stoichiometry is still unclear. This study explored the spatial characteristics of nutrients in the topsoil in M. sieversii communities in response to variation of environmental factors such as elevation in Yili Valley and Tacheng regions. Within the two regions, a total of 60 soil samples (0-10 cm depth) in M. sieversii communities were taken from six counties. The contents of soil organic carbon (C), total nitrogen (N), total phosphorus (P), total potassium (K), available nitrogen (AN), available phosphorus (AP) and available potassium (AP) were measured and their stoichiometric ratios being calculated. Environmental factors including slope, latitude, altitude and precipitation were investigated to study their relationships with soil stoichiometric characteristics. Our results showed that soil C, N, P, and K concentrations of M. sieversiicommunities in Yili were 68.66, 6.64, 1.14, 20.92 g·kg^-1, respectively. The AN, AP, AK concentrations were 562.10, 10.02, 474.50 mg·kg^-1, respectively. Soil C∶N, C∶P, C∶K, N∶P, N∶K, P∶K, AN∶AP, AN∶AK and AP∶AK were 10.22, 59.83, 3.32, 5.80, 0.32, 0.05, 62.00, 1.31 and 0.02, respectively. Except for the values of K, AP, AK and N∶P, stoichiometric values in Yili region were significantly higher than those in Tacheng region, while Tacheng region had a lower coefficient of variation. Soil nutrient contents and their stoichiometric ratios differed significantly among the six counties. Significant linear correlations were found between C and N content, and between C and P content, and significant nonlinear correlations were observed between N and P content, AP and AK content. Canonical Correlation Analysis (CCA) results showed that slope, latitude, altitude and precipitation were the main factors driving the stoichiometric characteristics of soil nutrients in M. sieversii communities.

Effects of simulated karst soil habitat stresses on photosynthetic characteristics and dry matter allocation of Robinia pseudoacaciaseedlings.

HANG Hong-tao, WU Yan-you, ZHANG Kai-yan, TAN Dai-jun, LU Na-na, MIN Xiao-ying, GUO Tao, CHEN Lei

2019, 38(9):  2648-2654. 

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To explore the adaptability of Robinia pseudoacacia to different karst environments and its configuration in ecosystem construction, four kinds of karst soil habitat stresses, including drought, highcarbonate, lownutrient, and phosphorusdeficiency, were artificially simulated under indoor hydroponic experiment. We measured the photosynthetic characteristics, carbonic anhydrase activity, δ¹³C value and dry matter allocation of seedlings under different karst habitat stresses. The results showed that under  drought environment, the seedlings of R. pseudoacacia were the most sensitive and inhibited in the short term (10 days). Although the rootshoot ratio and water use efficiency were increased, the seedlings could survive in a longer term (20 days). Under the high bicarbonate environment, R. pseudoacacia seedlings increased the utilization of HCO₃^- by increasing the activity of carbonic anhydrase due to the decrease of stomatal conductance, thereby improving dry matter allocation to stems and leaves and maintaining normal growth for a longer term. Under low nutrient environment, stomatal factor was the main limitation for the growth of R. pseudoacacia in a short term (10 days). R. pseudoacacia increased the utilization of HCO₃^- in the solution by increasing the activity of carbonic anhydrase in the longer term (20 days), and increased dry matter allocation to roots. However, the growth was still limited by the concentration of inorganic elements in the solution. Under phosphorusdeficient environment, the R. pseudoacacia seedlings increased the utilization of HCO₃^- in the solution by up-regulating the activity of carbonic anhydrase, increased dry matter allocation to roots, and maintained the high growth capacity. The adaptation strateiges of R. pseudoacacia seedlings differed under different karst environments. The results of comprehensive evaluation showed that the adaptation of R. pseudoacacia to four simulated karst soil stresses was in the order of high carbonate, phosphorus deficiency, low nutrition, and drought.

Effects of different nitrogen forms and ratios on the growth of Phyllostachys edulis and Quercus glauca seedlings.

WANG Xing-meng, CHEN Zhi-hao, LI Yong-chun, WU Jia-sen, LI Yong-fu, ZHONG Bin, LIANG Chen-fei, XU Qiu-fang

2019, 38(9):  2655-2661. 

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To test the preference of Phyllostachys edulis and Quercus glaucaseedlings for nitrate-N (NO₃^--N) and ammonium-N (NH₄⁺-N), we grew their seedlings in hydroponic culture with five different NH₄⁺-N∶NO₃^--N ratios (100∶0, 75∶25, 50∶50, 25∶75, 0∶100), and measured SPAD values of the leave, root morphology, and root nitrate reductase activity (NRA). The results showed that both nitrogen forms and ratios significantly affected growth characteristics of P. edulis and Q. glauca seedlings. SPAD values, root length, root surface area and NRA of P. edulis seedlings were higher in the 75∶25 treatment than in the other treatments (P<0.05). Root length and root surface area of Q. glauca seedlings were higher in the 25∶75 treatment than in the other treatments (P<0.05). The SPAD values of Q. glauca leaves were higher in the 0∶100 treatment with nitrate as the sole nitrogen source than in the other treatments (P<0.01). The NRA in roots of Q. glauca correlated positively with nitrate concentration in nutrient solution, but not forP. edulis seedlings. Our findings indicate that P. edulisprefers ammonium at seedling stage, while Q. glaucaprefers nitrate.

Water-holding characteristics of litter in five typical water conservation forests in low mountainous areas of eastern Liaoning.

YANG Xia, CHEN Li-hua, KANG Ying-li, GONG Wen-yan, ZHENG Xue-liang

2019, 38(9):  2662-2670. 

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Understanding waterholding characteristics of litter of different water conservation forests in the low mountainous areas of eastern Liaoning can provide theoretical basis for construction and management of water conservation forests. In June 2018, we investigated the thickness and stock volume of litter in pure forests (Larix olgensis, Pinus tabuliformis, P. koraiensis, Robinia pseudoacacia) and a mixed forest in stateowned Wendao Forest Farm of Fushun County, Liaoning Province. The maximum waterholding capacity, maximum waterholding rate and other indices were measured by soaking method. The relationship between waterholding capacity, water absorption rate and soaking time of litter was established. The results showed that: (1) The thickness of litter layer in five stands ranged from 3.6 to 7.8 cm, with an average value of 6.2 cm. The stock volume of litter was between 15.40 and 50.38 t·hm^-2, with an average value of 30.42 t·hm^-2. (2) The maximum waterholding capacity was between 13.61 and 27.21 t·hm^-2, with a rank of mixed forest>L. olgensisforest >R. pseudoacacia forest >P. koraiensis forest >P. tabuliformis forest. The maximum waterholding rate changed slightly, with the order of R. pseudoacacia forest >L. olgensisforest >mixed forest>P. koraiensis forest >P. tabuliformis forest. (3) The effective water storage capacity of litter was between 19.60 and 142.67 t·hm^-2, with an order of L. olgensisforest >P. koraiensisforest >mixed forest>R. pseudoacaciaforest >P. tabuliformisforest. (4) The relationship between waterholding capacity and soaking time fitted well with equation as Q=alnt+b, with correlation coefficient (R²) greater than 0.80. The relationship between water absorption rate and soaking time followed equation as V=ctn, with R² over 0.99. In conclusion, litter volume, waterholding capacity, and effective water storage capacity of L. olgensis forest and P. koraiensisforest were the highest, followed by R. pseudoacacia forest and mixed forest, P. tabuliformis forest was the worst.

Effects of soil fauna on element release during litter decomposition in Maolan karst forest.

LONG Jian, ZHANG Ming-jiang, ZHAO Chang, WU Qiu-sheng, WU Jin-nan, HUANG Bo-cong, ZHANG Ju-mei

2019, 38(9):  2671-2682. 

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To explore the effects of soil fauna on litter mass loss and the release of elements during decomposition, litters of two typical evergreen tree species, Cyclobalanopsis glauca (CG) and Kmeria septentrionalis(KS), were selected to conduct a field decomposition experiment with three different mesh sizes (5, 2 and 0.03 mm) of litterbags for one year in the virgin forest of Maolan karst area. The relationships between litter mass loss, changes of element contents and soil fauna communities were analyzed. The results showed that the contribution of soil fauna to litter mass loss of those two species ranged from 42.0% to 45.9%. Soil macrofauna had the maximum contribution to the mass loss of the mixed litter (CG+KS, with a ratio of 1:1), while meso and microfauna had the minimum contribution to the mass loss of KS litter. Soil fauna promoted or inhibited N release from the KS litter, and promoted N release from the mixed litter. Soil fauna promoted Ca release from the KS litter. The effects of soil fauna on P and K release were relatively complicated and depended on litter types. There was no effect of soil fauna on the release of C and Mg. In conclusion, the effects of soil fauna on mass loss and nutrient release were more significant in the high quality (with low C/N ratio) litter, such as that of KS. Our results provide a reference for understanding the mechanism of litter decomposition in Maolan karst forest.

Aphid resistance and volatile organic compounds in Artemisia vulgaris and Artemisia verbenacea.

LIU Chen-wei, ZHANG Kai-ge, XUE Huan-huan, JIANG Yi-fan, WANG Hai-bin, FANG Wei-min, GUAN Zhi-yong, CHEN Fa-di, CHEN Su-mei, ZHENG Li

2019, 38(9):  2683-2692. 

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The effects of Artemisia vulgaris and A. verbenacea on aphid repellency and resistance, and the components of volatiles were analyzed to discover the aphidresistant plants. We used Y-tube olfactometer behavioral trend test and indoor aphid infestation to identify the resistance of A. vulgaris and A. verbenaceato aphid. The volatile organic components were extracted via organic extraction and identified by GC-MS. Results from the Y-tube olfactometer behavior analysis showed that A. vulgaris and A. verbenacea are repellent to aphids.A. vulgaris and A. verbenaceahave an obvious inhibitory effect on the aphid population. The volatile components in the leaves, stems and roots of A. vulgaris andA. verbenacea were significantly different. The number of unique components in the leaves was significantly higher than that in the stems and roots. Furthermore, the concentrations of major common components in the leaves were higher. Eucalyptol, phytol, β-copaene and coumarin in the leaves and stems are toxic to insects. The neryl propionate is the major VOC in the roots. A. vulgaris and A. verbenacea have obvious effects on aphid repellency and resistance, and their leaves and stems contain many insect-resistant volatile components. Both species are aphid-resistant germplasms.

The effects of concentration and duration of seed soaking by GA₃ on the development of Astragalus membranaceus seedlings under severe drought and salt stresses.

WANG Nan, GAO Jing, HUANG Wen-jing, LI Bo, HE Yi-han, TANG Zhi-shu, SONG Zhong-xing

2019, 38(9):  2693-2701. 

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An experiment was conducted to explore the effects of soaking time and applied level of gibberellic acid (GA₃) on the development of Astragalus membranaceus seedlings under severe drought and salt stresses. There were five application levels (0, 50, 100, 200 and 400 mg·L^-1) of GA₃ and five duration periods (6, 12, 24, 36 and 48 h) for seed soaking, After that, the treated seeds were transferred to -0.6 and -0.9 MPa NaCl solutions respectively. Total germination percentage (TGP), mean germination time (MGT), root/shoot inhibition index (R/SII), shoot length (SL), root length (RL), shoot dry weight (SDW) and root dry weight (RDW) were measured. The results showed that, with the extension of soaking time and the increase of GA₃ application levels, TGPs of A. membranaceus were enhanced under both stresses while MGTs were substantially shortened. SL of soaking seeds with 400 mg·L^-1 GA₃ for more than 36 h under NaCl stress was significantly inhibited, while RL was significantly reduced at the level of 200 mg·L^-1 GA₃ or higher for 36 h and 400 mg·L^-1 GA₃ for 24 h (P<0.05). The significant inhibition of SL and RL under PEG stresses began at 36 h after soaking seeds at 200 mg·L^-1 GA₃ or higher level (P<0.05). The significant inhibition of GA₃ on SDW and RDW under NaCl stress began at 36 h after soaking seeds at 200 mg·L^-1 or higher, while the significant inhibition of GA₃ on SDW and RDW under PEG stress began at 48 h after soaking seeds at 200 mg·L^-1 GA₃ or higher (P<0.05). There were significant correlations among TGP, MGT, SL, RL, SDW and RDW (P<0.05). The optimum treatment combinations of 103 mg·L^-1 GA₃ for 40 h and 51 mg·L^-1 GA₃ for 48 h could contribute to the germination and seedling development under NaCl and PEG stresses, respectively.

Effects of uniconazole on photosynthetic physiology and phenotype of soybean under flooding stress.

ZUO Guan-qiang, WANG Shi-ya, FENG Nai-jie, WANG Xin-xin, MU Bao-min, ZHENG Dian-feng

2019, 38(9):  2702-2708. 

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To clarify the alleviating roles of uniconazole as a plant growth regulator on stresses, we examined the effects of uniconazole on photosynthetic rate, intrinsic property, chlorophyll parameters, and phenotype of soybean cultivar “Kenfeng 14” under flooding stress. The results showed that flooding stress at flowering stage (R1) decreased maximum net photosynthetic rate at seedfilling stage (R6) of soybean, but had no effects on the chlorophyll contents, the maximum electron transport rate, eigenabsorption crosssection of photosynthetic pigment molecule from ground state i to excited state k as a result of light illumination, and minimum average lifetime of photosynthetic pigment molecules in the excited state. Spraying uniconazole increased the chlorophyll contents and the effective light absorption crosssection of lightharvesting pigment molecules, but decreased the minimum average lifetime of photosynthetic pigment molecules in the excited state which made more photosynthetic pigment molecules in the ground state. Compared to the floodingstressed plants received no uniconazole, spraying uniconazole increased the electron use efficiency by 45.5%, maximum net photosynthetic rate by 79.0%, and the maximum electron transport rate by 39.2%. The flooding stress decreased the chlorophyll fluorescence parameters of F_v/F_o and F_v/F_m, whose values were improved by the application of uniconazole. Both flooding stress and uniconazole treatments decreased the height, leaf area and digital biomass of soybean. However, the application of uniconazole enhanced the values of leaf hue and NDVI, and improved the growth of soybean. In conclusion, the application of uniconazole effectively alleviated the adverse impacts of flooding stress on soybean and improved the flooding tolerance of soybean.

Effects of exogenous melatonin on photosynthesis and physiology of soybean during podding stage under drought stress.

ZOU Jing-nan, CAO Liang, WANG Meng-xue, JIN Xi-jun, REN Chun-yuan, WANG Ming-yao, YU Qi, ZHANG Yu-xian

2019, 38(9):  2709-2718. 

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To understand the effects of 100 μmol·L^-1 exogenous melatonin on photosynthesis and physiology of soybean during podding stage under drought stress, a pot experiment was carried out with soybean cultivar ‘Suinong 26’. The results showed that, compared to normal water supply, drought stress inhibited the growth and decreased the pod number of soybean, and consequently reduced the yield. Drought stress continuously decreased the photosynthesis and chlorophyll fluorescence, with antioxidant enzyme activity and osmotic adjustment substances being increased first and then decreased, membrane lipid peroxidation levels being increased. Exogenous melatonin increased the fresh weight, dry weight, plant height, leaf area and pod number in the podding stage of soybean under drought stress and thus increased yield, alleviated the decline of photosynthesis and chlorophyll fluorescence, increased the activities of antioxidant enzyme (SOD, POD, CAT, APX) and the contents of osmotic adjustment substances (soluble sugar, soluble protein, proline) in leaves, and regulated membrane lipid peroxidation balance (MDA, H₂O₂ and relative conductivity). Meanwhile, melatonin treatment increased the P_n,T_r and G_s of soybean leaves under drought stress by 14.1%-30.0%, 7.3%-19.6%, 12.4%-20.3%, respectively; increased F_v/F_o, F_v/F_m, Φ_PSII and ETR by 3.5%-15.5%, 5.4%-9.4%, 2.6%-5.9%, and 3.0%-18.2%, respectively. Compared with drought stress, the fresh weight of grain, dry weight of grain, grain number, pod number and plant height under melatonin treatment increased by 37.5%-51.4%, 35.2%-150.0%, 23.4%-42.1%, 6.6%-28.7%, 2.6%-9.6% respectively; the number of pods per plant, the number grain of per plants, the grain weight per plant and the 100-grain weight increased by 8.6%, 7.1%, 10.5% and 6.5% respectively. In conclusion, exogenous melatonin can enhance photosynthesis and antioxidant enzyme activities and alleviate growth inhibition under drought stress, which enhances the resistance of soybean to drought and increases its yield.

Effects of high temperature on potato photosynthetic and antioxidant properties during tuber formation period.

FENG Peng-bo, MU Yu, SUN Jian-bo, WU Jia-rui, WANG Yue-ning, LIU Qiang-juan, WU Na, KANG Jian-hong

2019, 38(9):  2719-2726. 

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High temperature during tuber formation is an important factor affecting the yield and quality of potatoes in mountainous areas of southern Ningxia. A 2year field experiment was conducted to investigate the effects of normal temperature (CK), low temperature and high temperature on the photosynthesis and antioxidant enzyme activities of potato cultivar ‘Qingshu 9’ during the initial, middle, and late stages of tuber formation, stage of tuber expansion, and main stage of starch accumulation. The results showed that net photosynthetic rate (P_n), fluorescent composite index (P_I), maximal efficiency of light energy conversion (F_v/F_m), and potential photochemical activity (F_v/F_o) in potato decreased significantly under high temperature compared with normal temperature and low temperature. In the late stage of tuber formation, P_n at high temperature decreased by 34.55% and 53.15% compared to normal and low temperature respectively, while P_I at high temperature decreased by 42.22% compared to low temperature. At high temperature, root activity, and the activities of protective enzymes such as superoxide dismutase SOD and POD significantly decreased, whereas malondialdehyde (MDA), proline (Pro) and catalase (CAT) increased in varying degrees. The yield of potato was negatively correlated with CAT activity, MDA and Pro concentrations in the antioxidant system, while it was positively correlated with other measured variables, especially the root activity. High temperature in the middle stage of tuber formation was not conducive to the photosynthesis in functional leaves of potatoes, which reduced P_n,P_I and other photosynthetic indices. Meanwhile, the antioxidant system of functional leaves was damaged in a certain extent, resulting in a yield decline.

Physiological effects of ammonium nitrogen and phytoplankton on Myriophyllum spicatum.

DAI Liang-liang, LI Li-jie, GUO Liang-liang, LI Gen-bao

2019, 38(9):  2727-2733. 

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To examine the relationships among ammonium nitrogen (NH₄⁺-N), phytoplankton and submerged macrophytes, an outdoor simulation experiment was conducted on the shores of Dianchi Lake. Theeffects of NH₄⁺-N on the growth and physiological characteristics of Myriophyllum spicatumwere investigated at different NH₄⁺-N concentrations (0, 0.05, 0.15, 0.50, 1.50, 5.00 mg·L^-1) and 100 μg·L^-1 of the initial chlorophylla. The growth and physiological indices of M. spicatum were measured. At the NH₄⁺-N concentration of 1.50 mg·L^-1, the height and biomass of M. spicatum were significantly higher than those under other treatments, while the total chlorophyll concentration, photosynthetic activity, and soluble protein concentration of M. spicatum could maintain the initial level. In contrast, these indices decreased in other treatments. Under combined conditions of NH₄⁺-N and phytoplankton, 1.50 mg·L^-1 of NH₄⁺-N was beneficial to the growth of M. spicatum whereas high concentration of NH₄⁺-N (5.00 mg·L^-1) and N deficiency (NH₄⁺-N≤0.50 mg·L^-1) were not beneficial to the growth of M. spicatum. When the NH₄⁺-N concentration reached 5.00 mg·L^-1, the massive phytoplankton blooms could bring some correlative effects, including the increases of water turbidity and the decreases of underwater light intensity, which resulted in the lower tolerance threshold of M. spicatumcompared with single pollution of NH₄⁺-N. Meanwhile, the inhibitory effects of submerged plants on phytoplankton would be relieved, leading to algae blooms, in which the chlorophyll-a concentration reached up to (948.1±313.0) μg·L^-1.

Toxicity of lead sulfate nanoparticles to Chlorella vulgaris.

SUN Hong-yu, ZHANG Si-yu, ZHAO Bing, YANG Chen, ZHAO Qing, ZHANG Xue-jiao, LI Hai-bo

2019, 38(9):  2734-2740. 

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Lead nanoparticles are major pollutants adsorbed to atmospheric fine particles. The phytotoxicity of lead nanoparticles is largely unknown. Here, the toxicity of lead nanoparticles to Chlorella vulgaris was investigated by taking lead sulfate nanoparticles (nano-PbSO₄) as a model. The morphology and growth inhibition of C. vulgaris exposed to nano-PbSO₄ or lead ion (Pb²⁺) were examined to elucidate the toxic effects. The concentration of Pb²⁺ in the culture medium containing nano-PbSO₄ was analyzed to probe the toxicity mechanism. The results showed that C. vulgaris cells were sunken and shrunken after being exposed to nano-PbSO₄, with visible nanoparticle aggregation on the surface. The inhibition on the growth of C. vulgaris increased with the increases of nano-PbSO₄ concentration and followed the nonlinear Logit model. The inhibition of nano-PbSO₄ to the growth of C. vulgaris was significantly lower than that of corresponding concentration of Pb²⁺, with the median effective concentration being 4.2 times of that of Pb²⁺. Only 0.31%-0.81% of the nano-PbSO₄ (0.01-1 mmol·L^-1) was dissolved into Pb²⁺ in the culture medium, indicating that the toxicity of nano-PbSO₄ was mainly attributed to the nano-effects with minor contribution of dissolved Pb²⁺. Our results provide reference for ecological risk assessment of lead nanoparticles.

Temporal and spatial distribution of microcystin in Baihua Reservoir, Guizhou Province, China.

QI Ji-qing, LI Qiu-hua, CHEN Wen-sheng, MA Xin-yang, CHEN Qian, XIONG Mei-jun, HAN Meng-shu, SUN Rong-guo

2019, 38(9):  2741-2748. 

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To understand the spatial and temporal distribution of microcystin (MC) concentrations in the reservoir, water samples were monthly collected in Baihua Reservoir, Guizhou Plateau from June 2017 to May 2018. The concentrations of MC (including two isomers of MC-RR and MC-LR), total phytoplankton abundance, cyanobacterial abundance, chlorophyll-a (Chla) concentration, nutritive salt concentration, water temperature and transparency were analyzed. The results showed that the concentrations of MC-RR and MC-LR ranged from 0.048 to 0.681 μg·L^-1 and from 0.046 to 0.964 μg·L^-1 respectively in the Baihua Reservoir. MC-RR occurred at high temperature while MC-LR occurred at low temperature. The Huaqiao sampling site had the highest number of detection and the highest concentration of MC, reaching 0.964 μg·L^-1, which did not exceed the limited value of 1.0 μg·L^-1; while dam sampling site was in the opposite. The MC-RR concentration was positively correlated with water temperature and ammonium nitrogen (NH₄⁺-N) concentration, and MC-LR was positively correlated with NH₄⁺-N concentration, nitrite nitrogen (NO₂^--N) concentration, and pH. Meanwhile, MC-RR concentration was significantly positively correlated with the abundance of Pseudanabaena limnetica and Anabaena circinalis and positively correlated with Chroococcussp. abundance, while MC-LR concentration was not significantly correlated with phytoplankton abundance.

Effects of exogenous hormones on sex determination in embryo and the primary sex characters in juvenile of Trionyx sinensis.

GONG Qiao, TANG Yao, DIAO Xiao-ming, ZHAI Xu-liang

2019, 38(9):  2749-2755. 

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Chinese soft-shelled turtle (Trionyx sinensis) belongs to the group of temperature-dependent sex determination. Here we examined the effects of exogenous 17α-methyl testosterone (MT) and estradiol (E₂) on the sex determination of embryos during the sensitive stage as well as the primary sex characters of young softshelled turtles. The two kinds of hormones were injected into embryos during the sensitive period of sex determination. Results showed that hormones treatment  significantly affected embryo survival rate. The average hatching time of embryos in the E₂ group was 5.5 days earlier than that in the control, while that of the MT group was slightly later than that in the control. Turtles in the MT and E₂ groups were all males and females, respectively, while the ratio of male to female in the control group was 3∶11. Young turtles were fed for 40 days with different concentrations of MT and E₂ after 20 days of domestication. Three treatment groups (25, 50 and 100 mg·kg^-1) for each hormone and a control group were set up. Hormones treatment had no significant effect on the survival rate but promoted the morphological development of young soft-shelled turtles. After 40 days of feeding, the sex ratio (number of male∶number of undetermined sex∶number of female) of the 50 mg·kg^-1 E₂ treatment group changed from 19∶6∶15 to 19∶0∶4. The final female ratio (17.39%) was not significantly different from the control group (16.67%), but the proportion of females in the 25 mg·kg^-1 E₂group and the 100 mg·kg^-1 E₂ group was 0. The sex ratio (number of male∶number of undetermined sexnumber of female) of the MT treatment groups were 9∶0∶0, 19∶0∶0 and 8∶0∶0 respectively, all of which were males, with the primary sex characters being more obvious than that of the E₂ group and control.

Bacterial community and function in the intestinal tracts of sea cucumber (Apostichopus japonicus) at different temperatures.

QUAN Zi-jiao, GAO Ping-ping, ZHANG Yang, WANG Luo, DING Jun, CHANG Ya-qing

2019, 38(9):  2756-2764. 

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MiSeq high-throughput sequencing technology was used to investigate the intestinal colony bacterial community structure of Apostichopus japonicus at 10, 16, 21, and 26 ℃. The results showed that bacterial phylotypes in all groups are closely related at phylum level, with Bacteroidetes, Verrucomicrobia, and Proteobacteria being the dominant phyla. The dominant genera in the intestinal tract of sea cucumber were Rubritalea, Lutibacter, and Vibrio. Lutibacter and Vibrio had the largest proportion at 10 ℃, and Rubritalea had the largest proportion at 26 ℃. The proportion of these dominant bacteria in the gut microbiota at different temperatures is different, indicating that there is certain relationship between the intestinal flora of sea cucumber and its growth temperature. Particular bacteria in the intestinal flora of sea cucumber existed at different temperatures. The bacteria in the 10 ℃ group were Luteolibacterand Colwellia, the bacteria in the 21 ℃ group was Coraliomargarita, and in the 26 ℃ group was Photobacterium. The aestivation group had the most endemic bacteria, including Sphingomonas,Aeromonasand Phenylobacterium. Sphingomonas is an animal pathogen and Aeromonas has a certain virulence to sea cucumber, which is associated with low survival rate of sea cucumber at high temperature. Results of COG and KEGG annotation analysis revealed 24 COG functions and 41 KEGG pathways, and their functions belonged to amino acid transport and metabolism, carbohydrate transport and metabolism, and membrane transport. Most of the gut microbial gene functions of sea cucumber are concentrated in amino acid metabolism, carbohydrate metabolism, energy metabolism and substance transport, replication, and repair. These functions are closely related to the growth of sea cucumber. The functional abundance was the lowest at 10 ℃ treatment.

Waterbird diversity in three reclamation regions of Poyang Lake.

HE Wen-yun, SHAO Ming-qin, ZHI Yi-jin, DAI Nian-hua, LU Ping, TU Xiao-yun

2019, 38(9):  2765-2771. 

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Waterbird diversity was investigated using the point count method in Wuxing, Henghu and Kangshan reclamation regions of Poyang Lake, China, from November 2017 to April 2018. A total of 51 species belonging to 7 orders and 12 families were recorded. Within all the recorded species, Oriental white stork (Ciconia boyciana) and Siberian crane (Grus leucogeranus) are in the first category of China’s nationally protected bird species, and five other species are listed in the second category of nationally protected bird species. In terms of settlement type, winter migrants (35 species, 68.63%) dominated the community. Of the avifauna, Palaesrctic components (33 species, 64.71%) were the most abundant. The diversity index and evenness index in the natural habitats of all three reclamation regions were higher than those in artificial habitats because the vast successive grassland and shallow water areas provided suitable habitats for many waterbirds. Across all the natural habitats, diversity index was the highest in Kangshan reclamation region (3.417), and the lowest in Wuxing (2.646). In artificial habitats, the diversity index was the highest in the Kangshan reclamation region (2.986) and the lowest in Henghu reclamation region (1.229), which was correlated to diverse micro-habitats. Our results showed that the artificial habitats of Poyang Lake reclamation regions provided a good temporary foraging ground for waterbirds such as common cranes (Grus grus) and swan goose (Anser cygnoid). Reclamation regions can alleviate resource competition of birds in natural habitat, which are a valuable supplement to natural habitat resources for birds and play an important role in the maintenance of bird diversity and the protection of rare species. The natural habitats of Poyang Lake, which play the most important role in bird conservation, should be protected.

Night roosting habitat selection of oriental magpie robin (Copsychus saularis) during breeding and non-breeding stages in urban green land.

PAN Yang, GAO Ji-xi, ZHOU Ke-xin, AN Shu-qing, YUAN Bao-dong

2019, 38(9):  2772-2779. 

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Night roosting site is a vital habitat for diurnal birds. Birds can show obvious preference in the selection of night roosting habitat. With the acceleration of urbanization, urban green land has gradually become a kind of habitat shelter for urban birds. How to adapt to the disturbance of urbanization and roost safely at night in the urban green land is a vital problem faced by birds. To explore the night roosting habitat selection of urban birds, we collected data on night roosting trees and 17 ecological factors related to the roosting site of oriental magpie robin (Copsychus saularis) in breeding stage and non-breeding stage, from March of 2014 to February of 2015 in Yizhou City of Guangxi Province. The results showed that oriental magpie robin selected 15 night roosting tree species. There was significant difference in the selection of tree species between breeding and non-breeding period. In both periods, the most frequently used tree species were Osmanthus fragrans, Mangifera indica and Bambusa ventricosa among the five tree species selected by oriental magpie robin. The results of principal component analysis showed that the main factors of night roosting habitat selection in breeding and non-breeding period were the concealment of roosting tree and perch and surrounding safety factors, followed by the other perch factors, water source, and food factors, and the last factor was disturbance. For nine factors, there were significant differences between the two periods, including the height of roosting tree and perch, the coverage of tree and herb, the coverage under roosting perch. Oriental magpie robin tended to select suitable night roosting habitat at different stages of life history, reflecting the high adaptability to urban environment with strong disturbance. In the future configuration and construction of urban green land, it is necessary to increase the arbor species with variable perch, tree height and coverage characteristics, and improve the diversity of shrub and herb, so as to meet the needs of night roosting habitat selection from different bird species.

Spatial distribution of soil carbon and nitrogen in green lands along an urbanization gradient.

AN Ji, LI Ting, FU Xiang, ZHANG Shi-rong, LI Zhi-ping, WEI Wei

2019, 38(9):  2780-2787. 

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Urbanization leads to the transformation of natural lands and agricultural lands to urban lands. The concentrations of soil organic carbon (SOC) and total nitrogen (TN) in urban green lands vary spatially due to frequent human disturbance. This study, conducted in a typical “central city suburban satellite city” gradient in ChengduWenjiang, aimed to evaluate the impacts of urban development on the spatial distribution of SOC and TN by using the indices of building density, road density, and distance from urban center. The results showed that mean values of SOC and TN concentrations and carbon-nitrogen ratio (C/N) were 15.80 g·kg^-1, 1.24 g·kg^-1 and 13.04, respectively. The concentrations of SOC and TN decreased from central city to suburb, and then increased from suburb to satellite city. Green land types showed no variation in the concentrations of SOC and TN (P>0.05), but the C/N in park green land soil was significantly higher than that in traffic green land (P<0.05). The concentrations of SOC and TN significantly exponentially decreased with the distance from the central city (P<0.05). Concentrations of SOC significantly linearly increased with the increases of building density and road density (P<0.05). Concentrations of TN showed no significant correlation with building density, but significantly linearly increased with the increases of road density (P<0.05). There was no significant correlation between C/N and distance from urban center, building density, and road density. Our findings reveal that urban development may result in accumulation of SOC and TN. The distance from urban center, building density and road density differentially impact the spatial distribution of SOC and TN.

Short-term effects of different cropping patterns on soil labile organic carbon fractions and yields of paddy fields.

CAO Pei, XU Ying, ZHU Jie, TIAN Yu-cong, FENG Xiang-zhao, LIU Zhang-yong

2019, 38(9):  2788-2798. 

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With the rapid development of maize and ratoon rice production recently in the middle reaches of Yangtze River, some new double cropping systems in a whole year such as spring maizelate rice, ratoon rice have been emerged. To clarify the shortterm effects of different cropping patterns of paddy fields on soil active organic carbon fractions, carbon pool management index (CPMI) at different soil layers (0-5, 5-10, 10-20 cm) and crop yield, a field experiment was conducted at the Sanhu Farm, Hubei Province in 2017. Different cropping systems were established following a design of randomized block of early ricelate rice (DR, contrast), spring maizelate rice (MR), and ratoon rice (Rr). The results showed that, compared with DR, MR treatment reduced soil total organic carbon (TOC) concentration at different layers of paddy fields to different degrees. After harvesting the first-season crops, MR treatment significantly reduced the concentration of soil dissolved organic carbon (DOC) at all soil depths compared to DR and Rr treatments. The changes of soil microbial biomass carbon (MBC) were MR > DR > Rr. The changes of soil readily oxidizable organic carbon (ROC) concentration were DR > MR > Rr. After the second-season crop harvest, there were no significant differences in soil DOC concentrations and MBC at different layers among cropping systems. Compared to the MR treatment, soil ROC concentrations were increased by 28.22% and 47.37% at the 10-20 cm soil layer under the DR and Rr treatments, respectively, being significantly higher in Rr than in MR treatment. After the harvest of second-season crops, MR treatment increased carbon pool activity (CPA) and carbon pool activity index (CPAI) of each soil layer, whereas Rr treatment increased stable carbon and carbon pool index (CPI). From the the year-round perspective in paddy field, the soil C/N difference across different soil layers showed same tendency among different cropping systems, being Rr > DR > MR. There was no significant difference in annual total yield among different cropping patterns. From the view of sustainable agricultural development, Rr pattern is an excellent double cropping pattern of the plain area of the middle reaches of the Yangtze River.

Spatial variation of agricultural soil Cd species and the nanohydroxyapatite resistance control in a typical small watershed.

CAI Tong, LIU Jing, LIU Xiao-li, WEI Xiang-dong, DU Hui-hui, TIE Bai-qing

2019, 38(9):  2799-2804. 

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Six soil samples were collected from Tieshan watershed, a typical mining small agricultural watershed in Liuyang City, which were used to analyze spatial variation of soil Cd content and its species. Effects of various nanohydroxyapatite addition doses on soil Cd availability and form transformation were examined using indoor flooding simulation experiment. Results showed that total Cd content in soils was 1.14, 1.37, 1.98, 7.44, 7.45 and 6.99 mg·kg^-1 from upstream to downstream of the watershed, with the percentage of available Cd being 51.75%, 40.15%, 39.39%, 16.40%, 28.86% and 29.76%, respectively. Spatial variation of soil total Cd and available Cd contents was highly significant in the watershed. The percentage of available Cd had significant negative correlation with soil pH. Flooding significantly decreased soil available Cd content. More available Cd transformed into the residual state with extension of flooding time. Soil available Cd content was decreased greatly with addition of nanohydroxyapatite, the effects of which were better with the increasing dose, being best at 5%. Compared with flooding alone, soil available Cd decreased by 77.97%, 83.64%, 82.05%, 77.87%, 74.88% and 73.56% in samples collected from sites S1-S6, respectively. The results can provide scientific reference for district management of safe agricultural production and control of heavy metal pollution in watershed scale of mining area in China.

Horizontal variability and autocorrelation of soil organic matter at different soil layers in estuarine wetland.

CHEN Si-ming, WANG Ning, QIN Yan-fang, ZOU Xiao-xing

2019, 38(9):  2805-2812. 

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A better understanding of the spatial distribution of soil organic matter (SOM) plays a key role in further studying cycling process of elements in estuary wetland soil. We examined the spatial distribution of SOM at different soil layers in Minjiang estuarine wetland by using variogram, multifractal and spatial autocorrelation analysis. The results showed that the coefficient of variation for SOM in the layers of 0-20, 20-40 and 40-60 cm were generally similar and moderate, with values of 46.25%, 49.01%, and 50.49%. All the ratios of nugget to sill were less than 25%, suggesting that structural factors played a dominant role in spatial heterogeneity. With the increases of soil depth, the spatial fractal structures of SOM in different soil layers were different. The SOM content in 0-20 cm layer was the most uneven, suggesting a higher fractal degree and a larger spatial variability. The Moran’s I of SOM in all the three soil layers was more than 1.96, showing a significant positive spatial autocorrelation. The value of Moran’s I in layer 20-40 cm was the largest, showing a more significant spatial autocorrelation and a higher spatial aggregation degree than the other two layers. In brief, our results reveal horizontal distribution characteristics of SOM in estuarine wetlands and provide methodological support for researches on the SOM spatial distribution in similar regions.

Spatial-temporal evolution of water footprint during the production of main grain crops in Liaoning Province from 1980 to 2016.

XUE Bing, DONG Shu-heng, HUANG Yu-pu, REN Wan-xia, LU Cheng-peng

2019, 38(9):  2813-2820. 

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Under the framework of production water footprint theory, based on CROPWAT 8.0 and GIS software, we quantitatively analyzed the water footprint structure and its dynamics during the processes of maize, rice and wheat production in Liaoning Province from 1980 to 2016 and illustrated the spatial evolution of water footprint of main grain crops production in 14 cities in Liaoning Province using the data of 2000, 2005, 2010 and 2015. The results are as follows: (1) During the study period, the annual water footprint of maize, rice and wheat in Liaoning Province was about 132.00×10⁸ m³. The overall trend was fluctuating and rising, among which the green water footprint occupied a dominant position. The proportion and total water footprint of the same grain crop were obviously different in different cities, being the highest in Shenyang and the lowest in Benxi. (2) According to the characteristics of annual variation, the production water footprint of maize and rice showed a steady upward trend, while that of wheat showed a trend of inverted “U” shape. In terms of water footprint structure, the proportion of green water footprint was higher than that of blue water footprint and grey water footprint. (3) From the evolution characteristics of spatial pattern, as a whole, the water footprint of main grain crops was higher in the north than in the south, and higher in the south than in the middle, showing a decreasing trend from northeast to southwest. Therefore, the rational layout of crop planting structure can effectively improve water use efficiency and the situation of water pollution. The rational use of green water resources is the key for sustainable use of water resources.

Conservation status and priority conservation areas of natural vegetation in northeast China.

PU Zhen, ZHANG Fang-ling, GU Yuan-yang, LIANG Xiao-yu, XING Shao-hua

2019, 38(9):  2821-2832. 

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Based on the data of spatial distribution, vegetation type, and elevation of continental national nature reserves (NNRs) in northeast China, we analyzed the relationships of the distributions of NNRs and vegetation with elevation using means of overlay analysis method. The aim of this study was to provide guidance of natural vegetation conservation in northeast China from both horizontal and vertical dimensions. The results showed that: (1) The main types of the NNRs in northeast China were forests, wetlands, and habitats for conserving wild animals. With the increases of altitude, the area and quantity of nature reserves decreased. The transient phenomenon of NNRs from wetland to forest occurred in the medium altitude range (600-1000 m). (2) Natural vegetations in high altitude range (above 1000 m) were better protected compared with those in medium and low altitude (below 1000 m) ranges where protection gaps still existed. (3) The protected areas at level one priority concentrated in the central and northeastern forest areas of Changbai Mountains, Liaohe River Estuary, and the northeastern part of Tongliao and the Hulunbeier Plateau. The protected areas at level two priority mainly distributed in mountainous regions of northeast China (Greater Khingan Mountains, Lesser Khingan Mountains and Changbai Mountains), especially the junction of the Greater Khingan Mountains and Lesser Khingan Mountains, as well as the transitional areas between grassland and forest in southern Greater Khingan Mountains and Liaodong hilly area. (4) As the main type of human disturbance, cultivated crops did not receive sufficient attention, which seriously threatened inland wetland and wildlife type NNRs in Northeast China Plain. Therefore, we suggested establishing natural protected areas system based on national parks in level one priority protected areas in the central forest areas of Changbai Mountains, enlarging current NNRs and establishing new nature reserves. In the remaining level one priority protected areas in the low altitude range where natural vegetation was seriously damaged by cultivated crops, management supervision should be strengthened. Secondary natural vegetation restored after disturbance could be protected to achieve the goal of regional biodiversity conservation.

The kinetic mechanism of oasis shelter forest in mitigating hail disaster.

LIU Ming-hu, ZHANG Jian-ping, SU Zhi, GAO Jun-liang, ZHAO Ying-ming, MA Ying-bin, MAN Da, LU Zhan-dong, WANG Zhi-gang

2019, 38(9):  2833-2839. 

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We conducted an onthespot investigation on the occurrence of hail disaster in Dengkou County, Inner Mongolia on June 13, 2016, to uncover the protection and kinetic mechanism of the desert oasis farmland shelterbelt system against hail disasters. We selected typical plots to survey yield and survival rate of crops inside and outside shelterbelt network after hail disaster. We estimated the variation of the horizontal speed of hail falling near the ground (H=0-40 m), based on the damage degree of the external wall of buildings in different height. We estimated the variation of the vertical speed of hail falling near the ground (H=0.5-50 m), based on the damage degree of the roof in dust level flux analyzer in different heights. The results showed that the survival rate of corn outside and inside the shelterbelt network plots were 24% and 87% respectively. The horizontal and vertical speed of hail decreased with decreasing height, which was consistent with the declining trend of wind speed profile and subsidence flow near the ground. The kinetic mechanism of mitigating hail disaster of shelter forest is that there is a strong kinetic effect of air which serves as a medium between the oasis shelter forest and the hail. The wind break belt is strongly resistant to the nearsurface airflow movement, which curbs the sinking and divergence of the hail airflow. After entering the low wind speed zone of the shelterbelt network, the hail blocks receive greater air resistance than those in the forestless zone, and the vertical and horizontal speed are significantly lower than that outside the shelterbelt network area, thus the ability of hail disaster is apparently reduced. Our results provide scientific basis for shelter forest construction and the assessment of their disaster reduction benefit.

Research advances on the regulation of nitric oxide on plant responses to iron deficiency.

YE Yi-quan, HONG Kai, ZHANG Jia-jun, LUO Hong-yan, CAO Guang-qiu, LIN Si-zu, XU Shan-shan

2019, 38(9):  2840-2849. 

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Nitric oxide (NO) is an important signal molecule in plants, which is critical for regulating plant growth and development. It also indispensably involves in regulating plant tolerance to iron (Fe) deficiency stress. In recent years, many significant progresses have been achieved on the mechanisms underlying the regulation effects of NO on plant responses to Fe deficiency. This review emphasizes the recent advances on NO synthesis and its signal transduction pathway in regulating the responses of plants to Fe deficiency, and the interactive role between NO and other signal molecules in the regulation of Fe deficiencyinduced plant response.

Effects of nitrogen input and its interactions with other nutritional factors on coastal wetland ecosystem: Progress and prospects.

2019, 38(9):  2850-2857. 

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The effects of external nitrogen (N) inputs on coastal wetland ecosystems are not independent, but combined with other environmental factors. Previous studies mainly focused on the effects of single N inputs. Limited information of multi-factor interaction is available, especially the relationship between N and other nutrients. We summarized the interactive effects of nitrogen inputs and other nutritional factors on coastal wetland ecosystems. The results showed that the heterogeneity was presented between effects of single nutrient factor and multi-factor interaction on coastal wetland ecosystems. The interactions can be divided into three types: positive, negative, and neutral. Moreover, four important research directions should be considered in future: (1) carrying out longterm positioning observation of control experiment; (2) exploring the method of transforming small-scale control experiment to large-scale application; (3) comprehensive considering the saturation threshold of nutrient elements and maximum predicted input value to scientifically set the upper line of exogenous nutrient inputs; (4) constructing the coupling model of interaction of multiple environmental factors and plant microbe soil system.

Effects of soil fauna on the decomposition of forest litter: Mechanism and modeling.

XU Xuan, WANG Wei-feng, RUAN Hong-hua

2019, 38(9):  2858-2865. 

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Soil fauna is an important component of forest ecosystems. We reviewed the contribution of soil fauna on litter decomposition in different forest ecosystems and the influencing factors, the underlying mechanisms of soil fauna affecting litter decomposition, and research advances on litter decomposition models, aiming to better understand the effects of soil fauna on aboveground and belowground ecological processes in forest ecosystems. We proposed a novel framework for modeling litter decomposition by considering the contribution of soil fauna. Soil fauna can affect litter decomposition by acting directly on litter (including moving, breaking and feeding, etc.) or indirectly on the soil (affecting litter decomposition microenvironment through shuttling and burrowing) and microorganisms (influencing the composition, quantity and activities of microbial communities which colonized in litter). Temperature and moisture are important factors affecting activities of soil fauna. The effects of soil fauna on litter decomposition in tropical forests are stronger than in subtropical forests, temperate forests and alpine/subalpine forests. Future modeling studies should focus on how to mimic the effects of soil fauna on litter decomposition and validate the modeling results using field experiment data.

Biodiversity of dominant functioning microbial communities and influencing factors during composting.

LU Xiao-lin, DAI Chuan-chao, JIA Yong

2019, 38(9):  2866-2874. 

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Compost is a complex system mediated by multiple factors. Functional microbes, which play a crucial role in composting, are regulated by environmental factors. There are obvious differences in microbial population during different composting stages. In recent years, researchers have clarified the diversity and function of dominant microbial populations, as well as the effects of environmental factors (temperature, oxygen, pH, EC, and nutrient levels) on the dominant microbial populations in different composting stages (mesophilic, thermophilic, cooling, and maturity). The interactions between the dominant microbial populations and environmental factors promote the fermentation processes of compost. This paper introduced the diversity, ecological functions and influencing factors of dominant microbial populations in different stages of composting, and proposed the problems faced by the composting research. This review provides a new perspective for the research direction and rational utilization of functional microbes in composting process.

Effects of container size and medium formula with biochar addition on the growth of Betula alnoides seedlings.

LIU Shi-ling, JIA Hong-yan, CHEN Lin, YANG Bao-guo, LEI Li-qun, PANG Sheng-jiang, ZHANG Pei

2019, 38(9):  2875-2882. 

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We examined the effects of container size and medium formula with biochar addition on the growth of Betula alnoides seedlings with three superior clones of B. alnoides (FB4, FB4⁺ and FB01) grown under three container sizes (4.5 cm×8.0 cm, 6.0 cm×9.0 cm, 8.0 cm×12.0 cm, diameter and height) and six medium formulas (different ratios of yellow soil, composted bark, sawdust, charred bark and bamboo charcoal). The optimum container size and media formula were determined by comparing seedling growth and root morphology, with a comprehensive evaluation of seedling growth. The results showed that the media formula, container size, clone and their interactions had significant effects on root collar diameter, seedling height, leaf area, leaf number, biomass, and root morphology. When considering the growth performance of all clones among different media ratios under the same medium type, the optimal growth performance occurred in the medium 4, in which the root collar diameter, seedling height, biomass, branch number, leaf area, leaf number, root length, root surface area, root volume, average root diameter were 1.01-1.36, 1.11-1.62, 1.13-2.94, 1.05-3.94, 1.05-2.86, 1.03-2.44, 1.29-2.17, 1.29-2.20, 1.32-2.44 and 1.00-1.60 times higher than those of other media formulas, respectively. With the increases of container size, root collar diameter, seedling height, leaf area, leaf number, biomass and root morphological characteristics of all clone seedlings increased, indicating that larger container facilitated seedling growth. Principal component analysis was used to analyze the growth and root morphology indexes of B. alnoidesseedlings, the results from which showed that the leaf area, root surface area, average root diameter and survival rate were comprehensive evaluation indices of seedling quality. After further calculation of the comprehensive evaluation index, the combination of clone FB4⁺, container size 3 (8.0 cm×12.0 cm) and medium 4(74.625% yellow heart soil, 24.875% bark, and 0.5% bamboo charcoal) showed the largest comprehensive evaluation index (1.566), exhibiting the strongest effects on seedling growth performance.

Evaluation and error analysis of gross primary productivity using land surface model CLM over FLUXNET. 

LI Rui, ZHANG Li, JING Yuan-shu, LI Pan, REN Xiao-li, HE Hong-lin, Lü Yan

2019, 38(9):  2883-2895. 

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Accurate estimate of gross primary productivity (GPP) is the basis for the modeling of terrestrial ecosystem carbon cycle and climate change projection. We evaluated the performance of CLM4.5 simulated GPP and analyzed the causes of errors using observed GPP data from FLUXNET, combined with  leaf area index (LAI） data. We conducted a sensitivity analysis to examine the key parameters in simulating GPP in CLM4.5 and discussed potential ways to improve the accuracy of photosynthesis simulation. Our results showed that CLM4.5 was better than CLM4 in simulating monthly and annual GPP. The mean absolute error (MAE) for the monthly and annual simulated GPP in CLM4.5 across plant functional types was reduced by 15% and 29%, respectively. However, CLM4.5 still presented a large bias in annual GPP with a MAE of 366.06 g C·m^-2·a^-1. The annual GPP bias had different seasonal variation for different plant functional types, with the bias mainly occurring in spring and summer. The GPP simulated by CLM4.5 was most sensitive to three parameters, i.e. specific leaf area, leaf carbontonitrogen ratio, and the fraction of nitrogen in Rubisco. The improvement in GPP simulation requires better modeling in phenology and leaf area index, P dynamics and C N P interactions, and a ecosystem-level photosynthetic parameter dataset.

Predicting distribution pattern and future change of Pinusmassonian a in China based on MaxEnt model.

YAN Yu-hang, CEN Yun-feng, ZHANG Peng-yan, ZHANG Yu, LIU Xin, LI Cangyu, XU Shuo

2019, 38(9):  2896-2901. 

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Climatic factor is one of the decisive factors determining species distribution. Based on the data of Pinus massoniana distribution and 19 variables of climatic factors, using software QGIS 2.18.3, ArcGIS 10.1 and MaxEnt model, the present distribution area of P. massoniana was simulated, and its future distribution was predicted. We analyzed the climatic variables affecting the distribution of P. massoniana. The results showed that: (1) Among the 19 climatic variables, the driest monthly precipitation (bio14) and the coldest season average temperature (bio11) contributed more than 70% to the distribution of P. massoniana; (2) Based on climatic data, the future distribution of P. massoniana was predicted, and its future distribution area would  increase by 35.82%; (3) Using QGIS 2.18.3 software to predict the future climate factors, the forecast results showed that climate change was consistent with the future distribution pattern of P. massoniana. Our results indicate that P. massoniana has strong adaptability, and that future climate change would have positive effects on its distribution.

Genetic structure analysis of ancient Ginkgo biloba L. populations based on SSR markers.

QI Ming, ZHOU Qi, NI Zhou-xian, WU Ya-qiong, HAN Xin, XU Li-an

2019, 38(9):  2902-2910. 

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Ginkgo biloba L., a unique species in Ginkgopside and known as the “living fossil”, has high value on economic and scientific research due to its wide usage with fruit, leaf, wood and ornament. In this study, 21 polymorphic SSR primers were used to analyze the genetic diversity and population genetic structure of G. biloba distributed in seven regions of China, with 137 alleles being detected in 214 individuals from seven ancient G. biloba populations. We observed high levels of genetic diversity (H_e=0.764) in the G. biloba populations, and the populations with highest level of genetic diversity came from Anlu (AL), Jingshan (JS) and Suizhou (SZ). The genetic differentiation coefficient (F_st=0.094) indicated that the most of the genetic variation were within population because of the high gene flow among populations (N_m=2.405). The seven populations were clustered into three major groups by STRUCTURE, PCA and phylogenetic analysis, with the population from Zhuji (ZJ) being significantly different from the others. The genotype frequencies of 21 SSR loci significantly deviated from the Hardy-Weinberg equilibrium within all populations. The imbalance of sex ratio caused by human interference might be the main reason. The abundant resources of ancientG. biloba in genetic diversity provided material basis for its use, and should be given priority in protection, especially for the male individuals of ancient G. biloba.