Table of Content

15 August 2019, Volume 30 Issue 8

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Spatial variability of plant community characteristics and its influencing factors in a small watershed of wind-water erosion crisscross region on the Loess Plateau, China

ZHANG Kai, CHEN Li-ru, XU Hui-min, LI Yang-yang

2019, 30(8):  2521-2530.  doi:10.13287/j.1001-9332.201908.001

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The small watershed is the basic unit of soil erosion control on the Loess Plateau. Consequently, the study of the spatial distribution and influencing factors of vegetation is the basis of vege-tation restoration and reconstruction in this region. A small watershed in the wind-water erosion crisscross region with the most serious soil erosion in the Loess Plateau was selected to investigate the changes of vegetation distribution and soil properties. The spatial variability of plant community characteristics and its main driving factors were studied by geo-statistical method and redundancy analysis (RDA). The results showed that there were 27 plant species in the small watershed, belonging to 12 families and 25 genera. Leguminous, Gramineous and Compositae plants were dominant families, contributing 59.3% of the total species. In general, the community structure was simple and the organization level was low. The aboveground biomass (AGB) and coverage (C) of the community reached 205.7 g·m^-2 and 57.7%, which was higher than the mean value of grassland in northern China, but the level of species diversity was lower. There were medium spatial correlation in AGB, but stronger spatial correlation for C, Patrick richness index (R), Shannon diversity index (H), Simpson dominance index (D) and Pielou evenness index (J). The spatial distribution of AGB was mainly patchy and striped, which was highest at the semi-shady slope and near the outlet of watershed. Other community characteristics were relatively fragmented, and R, H and J were higher at the top of the semi-shady slope. AGB and C were mainly affected by soil organic carbon, mineral nitrogen, total nitrogen, soil water content, and altitude, while R, H, D and J were mainly affected by soil saturated hydraulic conductivity, bulk density, sand content, and silt content. The results are helpful for vegetation restoration and evaluation of ecosystem structure and function in the wind-water erosion crisscross region.

Distribution of soil moisture and salt of Tamarix ramosissima plantation in desert saline-alkali land of Hexi Corridor Region, China

WANG Shi-lin, CAO Wen-xia, WANG Xiao-jun, LI Wen, LI Xiao-long, WANG Jin-lan

2019, 30(8):  2531-2540.  doi:10.13287/j.1001-9332.201908.002

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Soil salinization is a global problem. Afforestation is a major improvement practice for desert saline-alkali land. To examine ecological improvement effects and spatial distribution of soil moisture and salinity in Tamarix ramosissima plantation with the age of 10 years in desert saline-alkali land, soil moisture and salt content between rows and under shrubs with row distance of 2, 4, 6, and 8 m were measured. The structural equation model was used to quantify the effects of soil water and salt changes on plant growth. The results indicated that soluble salt in shallow soil (0-40 cm) of T. ramosissima plantation was significantly lower than that outside the plantation, but soil moisture under shrubs was higher than that between rows. Among different row distances, the maximum values of height and canopy size of T. ramosissima and coverage and biomass of vegetation under the shrubs were found in row distance of 6 m. The enrichment degree of soil cations around taproot was in order of Na⁺>K⁺>Ca²⁺>Mg²⁺ and anions were enriched with Cl^->HCO₃^->SO₄^2-. There were five kinds of salts in soil, with MgSO₄ being the most abundant, followed by CaCl₂, NaCl and MgCl₂, and the lowest being KHCO₃. Soil moisture had the strongest effects on vegetation, followed by soil salinity, and the lowest was soil pH, with values of 50.6%,29.5% and 19.9%, respectively.

Changes of non-structural carbohydrates in Caryopteris mongolica seedlings during the process of drought-induced mortality

SHEN Chao, JI Ruo-xuan, YU Xiao, BAI Xue-qia, CHANG Yuan, LIU Chao

2019, 30(8):  2541-2548.  doi:10.13287/j.1001-9332.201908.005

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The changes and distribution of non-structural carbohydrate (NSC, including soluble sugar and starch) content in different organs of one-year-old Caryopteris mongolica seedlings were investigated under suitable water condition (CK), slow-dying drought stress, and fast-dying drought stress. There was no significant difference in soluble sugar content of all organs between slow-dying drought stress and CK. With the extended duration of drought, the soluble sugar content in stem increased firstly and then decreased, while starch and NSC contents decreased. The soluble sugar content in coarse roots decreased, while starch and NSC contents increased. The soluble sugar content in leaves increased, while starch and NSC contents of leaves decreased. The NSC content of leaves, stems, coarse roots and fine roots were 6.2%, 7.8%, 8.3% and 7.4% at the death time (80 days), respectively. Under fast-dying drought stress, soluble sugar content in all organs was higher than that in CK, while starch and NSC contents were lower than that in CK. With the increasing time, soluble sugar content of roots decreased, while starch and NSC contents increased. The soluble sugar, starch and NSC contents in stems increased. The soluble sugar content of leaves increased, while starch and NSC contents decreased. The NSC content of leaves, stems, coarse roots and fine roots were 5.9%, 6.6%, 8.9% and 7.7% at lethal time (30 days), respectively. Under different drought stress, non-structural carbohydrates among different organs of C. mongolica seedlings showed different dynamics. Under slow-dying drought stress, NSC gave priority to allocate energy for maintaining physiological metabolism of organs. Under fast-dying drought stress, NSC mainly maintained plant metabolism in the form of soluble sugar, regulated osmotic potential, promoted water absorption, and coped with drastic drought stress.

Distribution characteristics and edge effect of soil water and salt in silvopastoral system of the Yellow River Delta, China

SUN Ruo-jun, CHEN Wei-feng, SONG Xi-liang, LUO Yan-feng, LIU Li-jun

2019, 30(8):  2549-2557.  doi:10.13287/j.1001-9332.201908.003

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We measured soil water and salt distribution characteristics at 0-40 cm soil depth in a silvopastoral system of Fraxinus chinensis and Robinia pseudoacacia mixed forest × Medicago sativa, which is located in Land Use Scientific Observation Field Base of Ministry of Land and Resource in Wudi, Shandong Province, China. The moving split-window technique was used to analyze the internal-system edge effect. The results showed that both soil water and salt contents in this system heterogeneously distributed in the horizontal direction. The variation of soil water was greater and that of soil salt contents was the smaller when closer to the soil surface. With the mixed forest tree row as the boundary line, the contents of soil water and salt on both sides showed similar change trend. With the decreases of distance to the tree row, soil water content reduced first and then increased but the salt contents had a stable fluctuation at 0-10 cm soil layer. Soil water content showed a trend of decrease-flat-decrease but the salt contents first enhanced and then reduced at 10-20 cm soil layer, respectively. At the deeper soil layer (20-40 cm), the water content fluctuated stably but the salt content continued increasing. Both the contents of soil water and salt in the vertical direction increased significantly with soil depth. Except HCO₃^- and K⁺, there was a similar change trend between ions and total salt content in the soil of silvopastoral system, and the correlation between these ions and total salt content was Na⁺>Cl^->SO₄^2->Mg²⁺>Ca²⁺. Based on the technique of moving split-window, the edge effect zone of soil water in the silvopastoral system was 2.5 m from the east side of the tree row to 2 m from the west side. Soil salinity in the silvopastoral system was mainly affected by the tree row within the range of 1.0 m, and by both of the tree row and M. sativa within the range of 1.0-3.0 m.

Stoichiometric characteristics of Artemisia sacrorum communities under different site conditions and their correlation with soil nutrients

WU Hui-feng, WANG Jing-jing, SONG Li-juan, LI Gang, WU Shui-juan, HAO Wen-fang

2019, 30(8):  2558-2566.  doi:10.13287/j.1001-9332.201908.026

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We explored the stoichiometric characteristic of Artemisia sacrorum communities and its correlation with soil characters by considering the aspect and slope position, and variation of soil nutrient in Yangqingchuan catchment of Wuqi. Our results showed that total carbon, total nitrogen, total phosphorus contents and C:N ratio in A. sacrorum (both shoot and root) in the top of hillock>sunny slope>semi-shady slope>shady slope. The C:P ratio in shoot and the N:P ratio in root decreased consistently. The N:P ratio in shoot and the C:P ratio in root decreased first and then increased. While the total nitrogen and total phosphorus in shoot, and the organic carbon in root increased first and then decreased with the decreases of slope position, the C:N ratio and N:P ratio in shoot decreased first and then increased. The stoichiometric characteristic of A. sacrorum communities was positively correlated with the soil stoichiometric characteristics. However, the C:N ratio, C:P ratio and N:P ratio of A. sacrorum and the total phosphorus of root were negatively correlated to corresponding soil indices. The correlation between shoot nutrition and soil was greater than that between soil and root nutrition. In conclusion, middle position of shady slope was optimal for the growth of A. sacrorum. The stoichiometric characteristics of plants were significantly correlated with soil nutrient condition. Aspect and slope position had a significant effect on the stoichiometric cha-racteristics of A. sacrorum community and soil. Proper A. sacrorum community could help restore soil nutrition.

Stability characteristics of soil organic carbon pool following development of sand-fixing forest in Mu Us sandy land, China

JIANG Xiao-dong, ZHENG Si-rui, YANG Mi-mi, WAN Jia-ming, HUANG Yue, YU Ke, TONG Xiao-gang

2019, 30(8):  2567-2574.  doi:10.13287/j.1001-9332.201908.008

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The study aimed to reveal the cumulative effects and stability characteristics of soil organic carbon (SOC) during forest development at the Mu Us sandy land, China. Using space for time substitution, surface soil samples were collected from semi-fixed sandy lands and restored arbor and shrub lands with the ages of 22, 32 and 53 years in the Yulin sand control region in Northern Shaanxi Province. The content of total organic carbon (TOC), oxidizable labile organic carbon, and resistant carbon and the characteristics of mineralized carbon emission and decomposition ratio were analyzed. The results showed that the increment of TOC for 22 to 53 years shrub and arbor lands from resistant carbon were 3.5-6.2 g·kg^-1 and 3.2-7.7 g·kg^-1, and from oxidized labile carbon were 2.8-3.4 g·kg^-1 and 1.3-2.8 g·kg^-1, respectively, compared with semi-fixed sand land. The ratio of soil oxidizable labile carbon in shrub land and arbor land were stable and maintained at 37.0% and 26.8%, respectively. However, the ratio decreased to 25.7% and 17.4% after incubated at a constant temperature for 60 days. The mineralization rate of shrub and arbor lands with 22-53 years was not significant at the ending of soil incubation. Carbon losses from oxidized liable carbon were 76.9%-98.7%, and only 1.3%-23.5% from resistant carbon in all sand-fixing forest plots. Compared with the maximum carbon emission rate, the soil cumulative carbon release exhibited a higher correlation with soil enzyme activities of β-glucosidase and dehydrogenase, but the enzyme activities did not change from 32-53 years. In conclusion, SOC pool showed stable characteristics of lower emission and higher sequestration with the increases of sand-fixing forest stand age. The carbon fixation effect of arbor sand-fixing forest was better than that of shrub sand-fixing forest.

Effects of weeding and fertilization on soil nitrogen mineralization and leaching in the mixed forest of Dalbergia odorifera and Santalum album

LI Xiao-fei, YANG Zeng-jiang, XU Da-ping, CUI Zhi-yi, LIU Xiao-jin

2019, 30(8):  2575-2582.  doi:10.13287/j.1001-9332.201908.004

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The mixed plantation of precious tree species Dalbergia odorifera and Santalum album is an important model for the development of plantations in South China. Based on an experiment with four treatments, i.e., CK (without any treatment), weeding, fertilization, weeding+fertilization, we investigated the effects of weeding and fertilization on soil net mineralization rate, net nitrification rate, net ammonification rate, and nitrogen leaching rate. Among the four treatments, the maximum net nitrogen mineralization rate in the 0-10 cm soil layer was 18.92 and 18.13 mg·kg^-1·month^-1 in spring and autumn, respectively; the maximum nitrification rate was 20.35 and 18.85 mg·kg^-1·month^-1in spring and autumn, respectively; the maximum ammonium mineralization rate was 0.22 and 0.26 mg·kg^-1·month^-1 in summer and winter, respectively; the maximum nitrogen leaching was 15.98 mg·kg^-1·month^-1 in autumn and 86.69 mg·kg^-1·year^-1 in the whole year. The treatments of weeding, fertilization, weeding+fertilization reduced net mineralization rate and net nitrification rate. The annual nitrogen mineralization decreased by 26.2%, 16.1% and 6.3%, respectively, and the annual nitrogen nitrification decreased by 17.1%, 16.6%, and 1.4%, respectively. Moreover, the treatments of weeding, fertilization, weeding+fertilization inhibited soil ammonium accumulation and reduced annual nitrogen leaching by 25.2%, 8.6%, and 6.1%, respectively. Compared with weeding, fertilization and weeding+fertilization, seasonal factors had more significant effects on soil nitrogen mineralization and leaching. Weeding, fertilization and weeding+fertilization decreased soil nitrogen nitrification and ammonification to a certain extent, reduced soil nitrogen mineralization and leaching loss, which contribute to the preservation of soil fertility and nitrogen accumulation.

Responses of tree growth to artificial intervention on micro-topography in degraded woodland on hillslope

WANG Zhen, WANG Ke-qin, ZHAO Yang-yi, PENG Shu-xian, WANG Shuai-bing, LI Kai

2019, 30(8):  2583-2590.  doi:10.13287/j.1001-9332.201908.006

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We explored the effects of microtopography changes from artificial intervention of soil and water conservation (contour reverse-slope terrace, CRT) on tree growth in a degraded woodland on hillslope in water resource area of Songhua dam in Kunming City. The differences of the diameter at breast height (DBH), tree height, new branch increment, and leaf area index (LAI) of dominant tree species in different plots were compared through dynamic monitoring. Then, the causes of differences were analyzed by combining the soil water availability. The results showed that the maximum and mean values of DBH and height of Pinus yunnanensis (dominant species) in contour reverse-slope terrace plot were larger than those in control plot (CK), and the proportion of small-sized and low-dwarf trees in degraded forest community was higher, which indicated that the growth potential of new and seriously degraded forest was stimulated. The annual variation rate of the ave-rage new branch length and diameter of P. yunnanensis in different plots reached 72.4% and 39.1%, respectively. The changes of new branch growth of P. yunnanensis, LAI of plots, and the new branch growth rate were greater in CRT than those in CK. Soil water content was significantly correlated with both the new branch growth and LAI. The ratio of available water in plot (64.2%) was higher than that in CK (54.7%). During the rainy season (from May to September), the available water in CRT existed longer, which was conducive to tree growth and the improvement of plant community structure in degraded woodland.

Effects of topographic factors on leaf traits of apricot in the Loess Plateau, Northwest China

WANG Xue-yan, CAO Jian-jun, ZHANG Xiao-fang, KONG Ying-ying, TIAN Hong, LI Meng-tian, XU Xue-yun, GONG Yi-fan

2019, 30(8):  2591-2599.  doi:10.13287/j.1001-9332.201908.027

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As important topographic factors, slope aspect and gradient affect plant growth and leaf functional traits by regulating the combination of water and heat. Exploring the response of leaf functional traits to topographic factors is helpful for understanding plant adaptation strategies. We investigated the effects of sunny slope (including half sunny slope) and shady slope (including half shady slope) and three slope gradient (15°-20°, 21°-25°, and 26°-30°) on the leaf functional traits of apricot (Prunus armeniaca L.), the main afforestation tree species on the Loess Plateau. The results showed that: 1) Slope aspect and gradient exerted significant effects on all functional traits. Except leaf water content (LWC), other leaf functional traits were not affected by the interaction of slope aspect and gradient. 2) The leaf area (LA) under the sunny slope was equivalent to that under the shady slope. Leaf dry matter content (LDMC) and LWC (0.27 g·g^-1 and 67.0%, respectively) were significantly higher under the shady slope than under the sunny slope (0.24 g·g^-1 and 59.6%, respectively), while specific leaf area (SLA) (163.05 cm²·g^-1) was significantly lower under the former than under the latter (183.72 cm²·g^-1). 3) At different slope gradients, SLA and LA reached a maximum value at 15°-20° (184.04 cm²·g^-1) and 26°-30° (21.14 cm²), respectively. 4) Except no difference in soil water content (θ) between 15°-20° and 26°-30°, it differed significantly between two slope aspects and among other slope gradients. The θ was one of the main factors causing the differences in functional traits, especially in the 0-10 cm soil layer. 5) SLA was negatively correlated with LWC and LDW and positively correlated with LA. LDW was positively correlated with LWC and negatively correlated with LA. θ was positively correlated with LWC but not with other leaf functional traits.

Effects of drought stress and recovery on photosynthesis and physiological characteristics of Hibiscus hamabo

SHI Qin, BAO Xue-wen, HUA Jian-feng, YU Chao-guang, YIN Yun-long, LU Zhi-guo

2019, 30(8):  2600-2606.  doi:10.13287/j.1001-9332.201908.020

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A greenhouse experiment was conducted to examine the photosynthetic and physiological responses of two-year-old cuttings of Hibiscus hamabo to the drought stress (20 days) and subsequent rewatering (21 days). The results showed that after 20-day drought, all individuals were survived in spite of the 5.9% soil water content. Drought stress drastically reduced net photosynthetic rate of H. hamabo, with the highest value only being 1.1 μmol·m^-2·s^-1. Drought stress declined the maximum photochemical efficiency to 84.3% compared with the control plants. Under drought stress, H. hamabo could stabilize cell osmotic potential and eliminate the drought-caused lipid peroxidation by coordinating the accumulation of soluble protein and antioxidant enzymes. After rewatering for seven days, net photosynthetic rate of treated H. hamabo recovered to 57.3% of that under control treatment. Meanwhile, the activities of superoxide dismutase and catalase decreased with the decline of malondialdehyde content. After rewatering for 21 days, no significant differences in the activities of antioxidant enzymes, soluble protein and relative water were found between the treated and control treatment. At harvest, the total biomass of treated H. hamabo decreased, while the root-shoot ratio remarkably increased when compared with control plants. In short, our results indicated strong drought tolerance of H. hamabo, which could play important roles in landscape improvement and greening in coastal areas.

Time lag of stem sap flow and its relationships with transpiration characteristics in Quercus liaotungensis and Robina pseudoacacia in the loess hilly region, China

YANG Jie, LYU Jin-lin, HE Qiu-yue, YAN Mei-jie, LI Guo-qing, DU Sheng

2019, 30(8):  2607-2613.  doi:10.13287/j.1001-9332.201908.013

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Using Granier-type thermal dissipation probes (TDP), we measured stem xylem sap flow of the natural dominant species Quercus liaotungensis and a reforestation species Robinia pseudoacacia from July to September in 2016 in the semiarid loess hilly region. Meteorological factors and soil water content were simultaneously monitored during the study period. Using cross-correlation analysis, time lag between diurnal patterns of sap flux density and vapor pressure deficit (VPD) was quantitatively estimated. Differences in the time lag between the two species and possible influence by different diameter classes and soil water contents were analyzed. The results showed that the diurnal courses of sap flux density were similar to those of meteorological factors, with daily peaks ear-lier than VPD. The peak of VPD lagged behind the sap flux densities of Q. liaotungensis and R. pseudoacacia 118.2 min and 39.5 min, respectively. The peak of PAR lagged behind the sap flux density of Q. liaotungensis 12.4 min, but was 68.5 min ahead of that for R. pseudoacacia. Time lag between sap flux density and VPD significantly varied between tree species and was affected by soil water content. Those during higher soil water content period were about 32.2 min and 68.2 min longer than those during the period with lower soil water content for the two species, respectively. There was no correlation between time lag and tree diameter classes. The time lag between VPD and sap flux density for R. pseudoacacia was about 21.4 min longer in smaller diameter trees than in larger trees, which was significantly different under the lower soil water content. Our results suggested that the time lag effect between VPD and sap flux densities in the two species reflected their sensitivities to driving factors of transpiration, and that higher soil water content was favorable to sap flux density reaching its peak early. The lower soil water content might lead to lower sensitivity of the trees to meteorological factors. R. pseudoacacia was more sensitive to changes of soil water content.

Tree architecture variation of plant communities along altitude and impact factors in Maoer Mountain, Guangxi, China

TAN Yi-bo, SHEN Wen-hui, TIAN Hong-deng, FU Zi, YE Jian-ping, ZHENG Wei, HUANG Shan-qi

2019, 30(8):  2614-2620.  doi:10.13287/j.1001-9332.201908.014

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Three typical plant communities (evergreen broad-leaved forest at low-altitude 1100 m, evergreen and deciduous mixed broad-leaved forest at mid-altitude 1500 m, and evergreen conife-rous and broad-leaved mixed forest at high-altitude 1900 m) in Maoer Mountain, Guangxi, China were surveyed along an altitude gradient. We measured the tree layer plant architecture and environmental factors, to analyze the variation of plant architecture traits among the three communities and its influencing factors. The results showed that the tree layer canopy area, basal diameter at 45 cm height, diameter at breast height (DBH), and leaf convergence increased with increasing altitude, whereas tree height, branch height, and canopy thickness first increased and then decreased. Horizontal branches occurred more often in communities at lower altitude , less frequent at high altitude, and the least frequent in middle altitude communities. Correlations among tree layer plant architecture traits were stronger in the mid-altitude community than that in the other altitude communities. Results from the redundancy analysis showed that soil organic matter and total solar radiation were the main factors driving the variation of plant architecture traits in the tree layers, accounting for 39.6% and 23.9% of the total variation, respectively. Soil organic matter had a greater positive impact on canopy area and branch height, whereas total solar radiation was more influential on the DBH and 45 cm basal diameter. In conclusion, tree layer architecture of communities along the altitude gradient in Maoer Mountain was divergent, with soil organic matter and total solar radiation as the main driving forces.

Spatial distribution patterns and association of Loropetalum chinense population in karst hills of Guilin, Southwest China

TU Hong-run, LI Jiao-feng, LIU Run-hong, LIANG Shi-chu, LAN Ze-nan, ZHANG Xin-yi, KANG Xin-dan, JIANG Yong

2019, 30(8):  2621-2630.  doi:10.13287/j.1001-9332.201908.016

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The spatial distribution and association of populations can reflect succession patterns and its adaptation strategies to the change of environmental factors, with important significance for vegetation restoration, reconstruction, and biodiversity conservation. We used the point-pattern analytical method to examine the spatial distribution and its association of the Loropetalum chinense population in karst hills of Guilin, China, based on field surveys. On the basis of Ripley K function, we used the pair-correlation function statistic derived to explore difference in the distribution patterns.We used Ripley L function to examine the spatial associations among the three diameter classes. The results showed that the diameter class structure of the population exhibited an irregular inverted “J” type, with the small diameter class occupying a large proportion, indicating an increased population structure with good regeneration capability. The individuals of the three diameter classes had a clumped distribution at the small scale. With the increases of spatial scales, the aggregation intensity gradually weakened and tended to be randomly distributed. There was an independent spatial association between individuals among the three diameter classes at small scale. As the scale increased, the spatial association between individuals with different diameter classes became positive or negative association. The greater the difference in diameter class of L. chinense population, the weaker their spatial correlation was, which might gradually turn into negative association. Our findings contributed to a clearer understanding of the ecological strategies and scale-dependent cha-racteristics of species coexistence and underlying mechanisms during the growth and development of L. chinense population in karst hills of Guilin, providing reference for the restoration, reconstruction, protection and management of forest in karst hills.

Latitudinal variation in soil carbon, nitrogen and phosphorus pools across island forests and shrublands in eastern China

TUO Bin, TIAN Wen-bin, GUO Chao, XU Ming-shan, ZHENG Li-ting, SU Tian, LIU Xiang-yu, YAN En-rong

2019, 30(8):  2631-2638.  doi:10.13287/j.1001-9332.201908.017

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Despite its monotonous structure, sea-island plays a crucial role in sustaining biodiversity and ecosystem functioning. The objectives of this study were to explore the altitudinal variation of soil carbon (C), nitrogen (N), and phosphorus (P) pools in forests across 14 islands spanning temperate zone (TZ), northern subtropical zone (NSZ), mid-subtropical zone (MSZ), and sou-thern subtropical zone (SSZ) in eastern China. The relationships of soil C and nutrient pools with climatic factors and plant species diversity were examined across islands. Our results showed that soil C, N and P pools differed significantly across climatic zones. Soil C and N pools were the lowest in TZ (49.35 and 1.08 t·hm^-2) and the highest in NSZ (137.25 and 4.63 t·hm^-2). Soil P pool was the lowest in SSZ (1.3 t·hm^-2) and the highest in NSZ (5.19 t·hm^-2). There were significant difference in soil C, N and P pools among vegetation types. Soil C, N and P pools in deciduous forests were significantly higher in subtropical than in temperate islands. Soil C and N pools in evergreen broadleaved forests did not differ among sub-climatic zones, and soil P pool was lower in SSZ than that in NSZ and MSZ. The interactions across mean annual temperature, mean annual precipitation, soil water content, and plant species diversity positively affected latitudinal variation in soil C, N, and P pools. Plant species diversity positively associated with soil N pool, but negatively linked with soil P pool. In conclusion, the latitudinal trend of soil C pool is different, but that of soil N and P pools are identical between sea-island and mainland. The main abiotic and biotic dri-vers of soil C, N and P pools are water availability, temperature and plant species diversity across sea-islands in eastern China.

Color change analysis and water content inversion of young sandalwood in multi-angle under water stress

CHEN Zhu-lin, WANG Xue-feng

2019, 30(8):  2639-2646.  doi:10.13287/j.1001-9332.201908.024

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Drought and waterlogging are two main abiotic stresses for plants, with serious impacts on plant physiological activities. In this study, the vertical and canopy leaf images of young sandalwood were obtained by SLR camera, with leaf segmentation algorithm being used to extract leaves and color features. We examined the color change of sandalwood leaves and water content inversion in different angles under two stress conditions. The results showed that leaf brightness decreased while the green component increased in the early stage (the first six days) of drought stress. After that, the brightness began to increase and green component began to decrease. Under water stress, the brightness of leaves decreased and yellow component increased in the whole stress cycle. The changes of control group was similar to that of the drought group, but the inflection point appeared later. Under the range of 50% to 70% for water content of leaves, the value of R, G, B channel of color images would decrease with the increases of water content. When the water content of leaves was less than 40%, the R channel value was larger than the G channel value. When using the extreme learning machine to retrieve the water content index, the corrected color components improved the fitness and the prediction accuracy. The vertical image was more suitable for retrieving water content of leaves, with the error of determination coefficient and average absolute percentage being 0.8352 and 2.3%, respectively. The canopy images were more accurate in expressing the equivalent water thickness of blades, with the above indices of 0.7924 and 9.3%, respectively.

Altitudinal variation of floral organs in Saussurea przewalskii and its relationship with the number and mass of seeds

QI Ru-lin, MA Wen-mei, QI Bai-yuan, CAO Jia-hao, YANG Ya-jun, MA Hai-rong, WANG Yi-feng

2019, 30(8):  2647-2653.  doi:10.13287/j.1001-9332.201908.012

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We examined the variation of floral organs of Sausssurea przewalskii along altitude and its relationship with the number and mass of seeds from 12 populations in the northeastern edge of Qinghai-Tibetan Plateau, China. At the altitude of 3500-4500 m, the filament length, anther length, column length and style branch length were 0.52-1.01, 0.23-0.63, 0.74-1.58, and 0.11-0.22 cm, respectively. All the indices significantly increased with altitude, while the number of pollens (26.5×10⁴-73.5×10⁴) significantly decreased. There was a significant negative correlation between the lengths of filament, style, column branches and pollen numbers, and a significant positive correlation between column length and filament length. The number of seeds was negatively correlated with the lengths of filament, column and style branches, but positively correlated with the number of pollen. The hundred kernals weight was positively correlated with the length of the filament, column and style branches, and negatively correlated with the number of pollen. With the increases of altitude, S. przewalskii extends the length of flower organs to increase the pollen carrying capacity and input of insects in the flowering period, and produces large seeds with more competitive advantage and survival rate in fruiting stage to improve its fitness.

Population dynamics of Artemisia scoparia in heterogeneous habitats in the desert steppe

CHEN Lin, SU Ying, LI Yue-fei, SONG Nai-ping, WANG Lei, YANG Xin-guo, QIU Kai-yang, LIU Bo

2019, 30(8):  2654-2666.  doi:10.13287/j.1001-9332.201908.019

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To understand the intra- and inter-annual population dynamics of Artemisia scoparia in the desert steppe, we set up three treatments, i.e., increasing the precipitation by 30%, reducing the precipitation by 30%, and the control (CK) in each soil habitat of aeolian sandy soil, sierozem soil, and bedrock weathered sedimentary soil. We drew up the dynamic life table to produce population survival and death curves and analyzed the population dynamics of A. scoparia in different habitats. Results showed that the survival curve of A. scoparia was approached to Deevey-Ⅰtype. The survival rate was high in the early growth stage and tended to be relatively stable. The mortality rate maintained at a low level, but rose fast at the end of the growth stage. The individual survival number of A. scoparia in all habitats fluctuated at the early stage and declined at the later stage. The mortality rates of A. scoparia in habitats of both aeolian sandy soil and sierozem soil fluctuated greatly. There was no significant difference in the effects of increased and decreased precipitation treatments on the mortality rate of A. scoparia. Soil types had significant effects on all parameters, including the plant height, crown width, density, cover, and biomass of A. scoparia. Precipitation treatments had significant impacts on plant height, crown width and coverage of A. scoparia, and had no significant effect on plant density and biomass. The interactions between soil type and precipitation treatments had only a significant impact on plant height and crown width. The plasticity index of biomass in the habitat of bedrock weathered sedimentary soil was significantly higher than that in habitats of aeolian sandy soil and sierozem soil, while the plasticity index of plant coverage in the habitats of both sierozem soil and bedrock weathered sedimentary soil were significantly higher than that in the habitat of aeolian sandy soil. The density plasticity index of increased precipitation treatment was significantly higher than those of CK and the decreased precipitation treatments. The plasticity index of plant height and crown width were higher than other parameters, indicating that A. scoparia could respond to habitat changes by giving priority to these two parameters under different habitat pressures.

Effects of nitrogen and plant growth promoter addition on the growth and competitiveness of Leymus chinensis

BU Dong-dong, LI Ang, WANG Yin-liu, WANG Chang-hui, HUANG Jian-hui

2019, 30(8):  2667-2674.  doi:10.13287/j.1001-9332.201908.015

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With a greenhouse pot experiment, we investigated the effects of nitrogen (N) and plant growth promoter (brassinolide, BR) addition on the growth and competitive ability of three common plant species of typical steppe in Inner Mongolia, including Leymus chinensis, Astragalus adsurgens and Stipa krylovii. We added N at rates of 0, 0.1, 0.2, 0.4, 0.8 mg·g^-1 soil and BR at rates of 0 and 0.005 mg·g^-1 soil during plant growth in monoculture or with L. chinensis being planted in mixing with other two species, respectively. There were significant effects on biomass of L. chinensis and A. adsurgens, but not on that of S. krylovii with increase of N and BR addition. The effects of N addition on the growth of L. chinensis varied with accompanying plant species. Nitrogen addition increased aboveground biomass production of L. chinensis when growing in monoculture and mixed with A. adsurgens, but decreased its belowground biomass when growing mixed with S. krylovii. With increasing soil N availability, plant biomass allocation of L. chinensis showed significant decrease in root-shoot ratio when it was in monoculture or mixed with S. krylovii, but similar changes were not found when it was planted in mixing with A. adsurgens. The significant effects of BR addition on plant growth appeared occasionally. BR addition significantly reduced belowground biomass of A. adsurgens in its monoculture and significantly increased aboveground biomass of L. chinensis when it was planted in mixing with A. adsurgens. The results indicated that the appropria-tely combined addition of N and BR could effectively enhance biomass production of specific species combinations in grasslands, which has application prospects in the restoration of degraded grassland.

Responses of plant species with different genome size to water and nitrogen addition in Inner Mongolia Grassland, China

ZHAO Fang-yuan, WEI Cun-zheng, LYU Xiao-tao, HAN Xing-guo

2019, 30(8):  2675-2681.  doi:10.13287/j.1001-9332.201908.018

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Plant genome size (GS) varies greatly over 2400-fold in angiosperms. Genome sizes are closely related to plant traits from cellular to individual level, which would have far-reaching ecolo-gical implications. Genome size may shape the interspecific responses of plants to changes of resource availability in Inner Mongolia grassland which is co-limited by water and nitrogen availabi-lity. We tested the role of genome size in structuring plant community composition after single and combined water (W) amd nitrogen (N) addition in a typical grassland of Inner Mongolia. Plant genome sizes were estimated by flow cytometry. We found that the response of plant aboveground net primary production (ANPP) to change in water availability was significantly affected by genome size. Water and NW addition significantly increased ANPP of small GS plants, instead of large GS species. Nitrogen addition had no effects on ANPP of both small and large GS plants. We found no effects of all the treatments on plant species richness. Results showed that GS modulated the response of grassland plant species to changes in water rather than nitrogen availability in Inner Mongolia. Since GS is a relatively constant trait with substantial interspecific variation, the application of GS in ecological studies would be of great significance to better understanding of ecosystem structure and function under global change.

Spatial variation and driving factors of invasive plants in Fujian Province, China

LI Zhi-peng, ZHAO Jian, CHEN Ye-bin, CHEN Hong, LIN Na, QIU Rong-zhou

2019, 30(8):  2682-2690.  doi:10.13287/j.1001-9332.201908.010

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Based on the field investigation data and the integration GIS spatial methods and geographical detector model, we analyzed the main and interactive effects of geographical and social environmental factors on the distribution of invasive plants in Fujian Province, China. The results showed that a total of 82 invasive plant species were recorded, with Compositae as the dominant family. Conyza canadensis, Ageratum conyzoides, and Alternanthera philoxeroides had the highest frequencies. There were more invasive species in coastal areas than in inland areas. Fuzhou and Xiamen were the hot areas for plant invaision. The invasive plants widely distributed at different altitudes, and the invasion reduced with the increasing altitude. The geographical detector analysis showed that rainfall as a natural environment factor and road density and people density as socio-economy factors were the major driving factors for the distribution of invasive plant species. The multi-factor interaction had a positive effect on the spatial distribution of invasive plants, implying the complexity of impact factors on the distribution of invasive plant species. In conclusion, the geographical detector could be used in the studies of invasive plants, and environmental factors could be also applied for monitoring the suitable establishment areas of invasive plants in Fujian Province. Our results provide a scientific basis for effective management of invasive plants.

Response of soil microbial biomass and microbial entropy to desertification in desert grassland

WU Xiu-zhi, LIU Bing-ru, YAN Xin, LIU Ren-tao, AN Hui

2019, 30(8):  2691-2698.  doi:10.13287/j.1001-9332.201908.009

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Using an approach of spatial sequence instead of temporal succession, we investigated the variation and driving factors of soil microbial biomass and microbial entropy in desert grasslands across four different desertification stages (grassland, fixed dune, semi-fixed dune and mobile dune) in Yanchi County, Ningxia, China. The results showed that soil microbial biomass carbon, nitrogen and phosphorus reduced by 46.1%, 80.8% and 30.0% from grassland to mobile dunes, respectively. The soil microbial entropy (qMBC, qMBN, and qMBP) decreased but soil-microbial stoichiometry imbalance (C:N_imb, C:P_imb and N:P_imb) generally increased with the development of desertification. There were significantly positive relationship between soil microbial biomass nitrogen and C:N_imb, soil microbial biomass phosphorus and C:P_imb, while negative relationship between soil microbial biomass nitrogen and N:P_imb. The RDA result showed that soil ecological stoichiometry (C:N, C:P) had the strongest negative effect on soil microbial entropy carbon (qMBC). Soil microbial biomass and microbial entropy were significantly affected by desertification in desert grassland.

Soil ecological stoichiometry characteristics under different types of biological soil crusts in the hilly Loess Plateau region, China

YANG Qiao-yun, ZHAO Yun-ge, BAO Tian-li, DING Qian , LIU Guang-liang

2019, 30(8):  2699-2706.  doi:10.13287/j.1001-9332.201908.011

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Biological soil crusts (biocrusts) play an important role in soil nutrient accumulation and cycling. We examined the relationship between soil nutrient characters and biocrusts types, with six typical types of biocrusts in the hilly Loess Plateau region, including light cyanobacterial crust, dark cyanobacterial crust, cyanobacterial with moss crust (mixed crusts), moss crust, Diploschistes spp. crust, and Nostoc commune crust. The variations of soil carbon (C), nitrogen (N), phospho-rus (P) concentrations and stoichiometric ratios of biocrustal layer and the subsoil under different types of biocrusts were investigated. The results showed that there were significant differences in C, N, P concentrations and stoichiometric ratio among different biocrusts types. The concentrations and stoichiometric ratios of C, N, P in the biocrustal layer were significantly higher than those of 0-10 cm soil beneath biocrusts. The concentrations of C and N significantly decreased with the increases of soil depth across all the biocrusts types. P content showed no variation between soil layers. The concentrations and stoichiometric ratios of C, N, P of moss crust were significantly higher than those of other biocrusts,with C, N, and P content of 27.07, 2.42 and 0.67 g·kg^-1. In soil layer of 0-2 cm, the concentrations and stoichiometric ratios of C, N, P under N. commune crust were significantly higher than those of other biocrusts.

Effects of directional planting on light environment and leaf photosynthesis of summer maize population

ZHAO Wei, XU Zheng, GAO Da-peng, AN Zhen, GAO Hui-yuan, ZHANG Zi-shan, NING Tang-yuan, LI Geng

2019, 30(8):  2707-2716.  doi:10.13287/j.1001-9332.201908.023

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To improve light environment, photosynthetic capacity, and thus the yield of maize, the effects of directional planting on light distribution in canopy and photosynthetic characteristics of ear leaves, as well as the performance of PSII that closely related with photosynthetic characteristics and reflected by the rapid chlorophyll fluorescence kinetic curves were examined in Zhengdan 958 maize variety. The results showed that the orientation of leaves remarkably affected photosynthetically active radiation (PAR) interception of ear leaves, with PAR interception of ear leaves in southward treatment being 271.8% higher than that under northward treatment. The orientation of leaves affec-ted photosynthetic light use efficiency of ear leaves under high and low light conditions. The southward treatment increased net photosynthetic rate (P_n) under saturated light in ear leaves, indicating that the use efficiency to high light was enhanced in leaves of southward treatment. In contrast, the northward treatment increased the apparent quantum yield (α) of ear leaves, indicating leaves in southward treatment adapted the light-limited environment. During the early stage after anthesis, the performance of PSII electron donor side and electron acceptor side was significantly improved, and thus enhanced the performance of PSII reaction center (PI_ABS) and fluorescence photochemical quenching coefficient (Ψ_o) in ear leaves of southward treatment. The increase of quantum yield of electron transfer (φ_Eo) indicated the enhancement of transfer performance of electrons from photosystem Ⅱ (PSII) to photosystem Ⅰ (PSI) in leaves of southward treatment. The photosynthetic performance of ear leaves showed a trend of southward > eastward > westward > northward during the early stage after anthesis. Forty days after anthesis, the use efficiency to high light decreased in ear leaves of southward treatment, but the ear leaves of southward treatment showed high use efficiency to low light, which changed the trend of photosynthetic performance of ear leaves to northward > westward > eastward > southward. In summary, northward and eastward treatments improved the light distribution in canopy, the PAR interception of ear leaves, the capacity of photosynthesis and dry matter production, and consequently increased the yield of summer maize.

Effects of elevated atmospheric CO₂ concentration on chemical composition of rice straw

SHI Meng-yuan, YU Hong-yan, ZOU Lu-yi, TENG Yue, ZHU Chun-wu

2019, 30(8):  2717-2724.  doi:10.13287/j.1001-9332.201908.041

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Rice straw is a potential material for bioenergy production. Elevated atmospheric carbon dioxide (CO₂) concentration changed the quantity and quality of rice straw, thus changing its bioenergy production potential. In this experiment, we collected rice straw from China Free Air CO₂ Enrichment Platform (FACE). Three rice varieties, Wuyunjing 27, Y Liangyou 900 and Nipponbare N16, were selected from the FACE platform (the CO₂ concentration in the experimental group was controlled at 570 μmol ·mol^-1, which was 200 μmol ·mol^-1 higher than the control group), the chemical composition of which was analyzed. The results showed that elevated CO₂ concentration significantly increased C content, C/N, and the content of non-structural carbohydrates in straw. Elevated CO₂ concentration significantly increased total sugar release by 8.8%, 6.7% and 9.9% in Wuyunjing 27, Y liangyou 900 and N16, respectively. Elevated CO₂ concentration significantly enhanced the biomass of N16 straw, but had no effect on the straw biomass of the other two rice varieties. The total sugar yield of N16 increased most significantly with elevated CO₂ concentration, reaching 19.2%. Our results indicated that elevated CO₂ concentration could improve the quality and quantity of rice straw, thereby increasing the utilization potential of biofuel.

Effects of solar radiation on CH₄ emission in paddy field

MA Li, LOU Yun-sheng, LI Jun, LI Rui, ZHANG Zhen

2019, 30(8):  2725-2736.  doi:10.13287/j.1001-9332.201908.022

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Decrease in solar radiation is one of the main components of climate change. Studies aimed at examining the effects of decreased solar radiation on CH₄ emission and estimation of CH₄ emission based on hyperspectral data in paddy fields are still scarce. A field simulation experiment was conducted to investigate the effects of shading intensity on CH₄ emission in a paddy field and rice canopy hyperspectral properties. CH₄ emission flux was estimated with rice canopy hyperspectral data. The shading intensities were set at three levels, i.e. control (CK, no shading), light shading (S₁, 60% of shading rate), and heavy shading (S₂, 84% of shading rate). The results showed that shading significantly reduced CH₄ emission. However, CH₄ emission under heavy shading (S₂) was higher than that under light shading (S₁). The reflectance of the near-infrared spectrum on rice canopy from the jointing stage to grain filling stage was in the sequence of CK>S₂>S₁. The spectral reflectance on rice canopy was significantly and positively correlated with CH₄ flux in the near-infrared band (699-1349 nm), with a correlation coefficient of 0.64 (P<0.01). The six vegetation indices were significantly correlated with CH₄ flux. The correlation coefficient between Ratio Vegetation Index (RVI) and CH₄ flux was the largest, with R²=0.84 (P<0.01). The stepwise regression model with RVI, Normalized Difference Vegetation Index (NDVI), and 507 nm original reflectance (ρ₅₀₇) parameters was the best one (fitting model R²=0.86, prediction model R²=0.85) for estimating CH₄ emission.

Effects of combined addition of organic materials with zinc fertilizer on zinc availability and transformation in calcareous soil

CHEN Yan-long, XIONG Shi-juan, DONG Jin-jin, JIA Zhou, WANG Song, WANG Shao-xia, SHI Jiang-lan, TIAN Xiao-hong

2019, 30(8):  2737-2745.  doi:10.13287/j.1001-9332.201908.038

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To investigate the changes of Zn availability and transformation in calcareous soil, orga-nic materials (maize straw, biofertilizer, fulvic acids, and chicken manure) were thoroughly mixed with the soils amended with Zn fertilizer in the nylon net bags and buried in a field. Results showed that compared with control (neither Zn nor organic materials), Zn fertilizer alone and combined addition with organic materials significantly increased soil total Zn concentration (7.2%-13.8%) and DTPA-Zn concentration (2.1-2.8 folds). For the Zn amended treatments, the contributions of organic amendments to soil total Zn and DTPA-Zn concentration decreased in the order of chicken manure > biofertilizer > maize straw > fulvic acids. The highest conversion rate of exogenous Zn into DTPA-Zn occurred in the treatments with straw and biofertilizer. In comparison with single Zn application, combination of Zn fertilizer with organic materials increased soil organic matter and stimulated more Zn weakly bound to organic matter, enhanced mobility factor and reduced distribution index of Zn in soil. The differences in soil Zn availability and transformation among the combinations of Zn fertilizer and organic materials were likely linked to the inherent properties of organic materials such as maturity degree and Zn content. Considering the environment safety and cost reduction, combining Zn fertilizer and straw return was the best practice to enhance Zn availability in the Zn-deficient calcareous soil, although its contribution to Zn availability was less than the combination of biofertilizer or chicken manure with Zn fertilizer.

Effects of maize straw returning on arbuscular mycorrhizal fungal community structure in soil

MA Kun, SONG Li-li, WANG Ming-guo, MA Zhan-qi, AN Yuan-yuan

2019, 30(8):  2746-2756.  doi:10.13287/j.1001-9332.201908.034

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To understand the effects of agricultural management activities on soil arbuscular mycorrhizal (AM) fungi diversity, the high-throughput sequencing based on Illumina MiSeq platform, and the fatty acids fingerprints were used to examine the effects of maize straw returning on soil arbuscular mycorrhizal fungi. The relationships between AM fungal community composition, AM fungal biomass and soil factors after maize straw returning were examined for four continuous years. A total of 2430 operational taxonomic units (OTUs) of AM fungi were classified into 10 genera and 143 species, respectively, which belonged to 1 phylum, 3 classes, 4 orders, 8 families. There was no significant difference in AM fungal community richness (Chaoles index and ACE index) and diversity (Shannon, Simpson diversity indices) in different treatments. Paraglomus and Glomus were dominant genera among all AM fungal communities. With the increase of the maize straw returned amounts, the abundance of Glomus reduced. Under the treatments of 3000 and 9000 kg·hm^-2 straw returned, the abundance of Glomus and Acaulospora had significant differences with the control (0 kg·hm^-2). Compared with the control, there were significant differences between Archaeospora, Paraglomus and Glomus in the treatment of 3000 kg·hm^-2 straw returned. Results from non-metric multi-dimensional scale (NMDS) analysis showed that under 9000 and 12000 kg·hm^-2 straw returning treatments, the difference between the β diversity of soil AM fungi and the spatial distance of controls was farther apart than the other treatments. The effect of straw returning on the β diversity of AM fungi was significant. The multivariate analysis results revealed the relationship of the spatial variation between the soil physicochemical properties and AM fungi richness and diversity could be explained at 82.8% cumulative variables. The total nitrogen and available nitrogen were the most important factors driving soil microbial communities biomass marked by PLFAs and AM fungal biomass (NLFAs). The continuous maize straw returning to the field changed the genera composition of AM fungi. With the increases of straw returning amounts, the specific species of AM fungi decreased and the similarity between AM fungi community composition decreased. Straw returning increased soil AM fungi biomass and its contribution to soil total microbial biomass.

Temporal dynamics and influencing factors of soil microbes in Larix gmelinii forest soil during spring freezing-thawing period

WANG Nan, WANG Chuan-kuan, DI Xue-ying, QUAN Xian-kui

2019, 30(8):  2757-2766.  doi:10.13287/j.1001-9332.201908.040

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Soil microbial community dynamics during the spring freezing-thawing period could affect carbon and nutrient cycling in the subsequent growing season. During spring soil freezing-thawing period, we monitored temporal dynamics of soil microbial community in different soil substrates for Larix gmelinii forest using phospholipid fatty acids (PLFAs) as biomarkers every 3-7 days. The results were as followed: 1) the total PLFAs content, the PLFAs content and relative abundance of each soil microbial group, the ratio of Gram-positive bacteria to Gram-negative bacteria (G⁺/G^-), the ratio of saturated PLFAs to unsaturated PLFAs (S/NS) and the ratio of bacteria to total fungi (fungi + arbuscular mycorrhizal fungi) (B/F) all varied among sampling times; 2) soil total organic carbon (TOC) and nitrogen (TN) were the main factors affecting soil microbial community in the early stage of soil freezing-thawing period; soil moisture, TOC and TN were the main driving factors in the middle stage of soil freezing-thawing period; soil microbes were affected by soil tempera-ture, moisture, TOC, TN and C/N in the late stage of soil freezing-thawing period; 3) the total PLFAs content, the PLFAs content and relative abundance of each soil microbial group (except the relative abundance of bacteria), B/F, G⁺/G^- and S/NS all showed significant difference between soil substrates, and soil TOC, TN and C/N were the key determination factors. Soil temperature, moisture, and nutrient availability were the main factors affecting soil microbial community during the spring soil freezing-thawing period, but the degree of influence varied with the freezing-thawing stages and microbial groups.

Effects of Pseudomonas aeruginosa on root activity and leaf physiological characteristics in rice (Oryza sativa L.) seedling under cadmium stress

WANG Dun-fei, ZHENG Xin-yu, XIAO Qing-tie, WANG Wei, LIN Rui-yu

2019, 30(8):  2767-2774.  doi:10.13287/j.1001-9332.201908.037

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To reveal the physiological effects of rice alleviated by cadmium-tolerant Pseudomonas aeruginosa under cadmium stress condition, the influences of bacterial strian on the root vigor and leaf physiological characteristics were analyzed under a set of hydroponic experiments involving adding bacteria suspension, empty carrier, microbial inoculum with 20 μmol·L^-1 Cd. Cadmium-free treatment as control. The results showed that the root vigor was significantly inhibited, leaf photosynthetic rate decreased, and the contents of soluble protein, flavonoid and total phenols in rice leaves were reduced, while the contents of malondialdehyde (MDA) and superoxide anion(O₂^-·) increased significantly under cadmium stress condition. Compared with cadmium treatment, root vigors of rice were increased by 36.1%-42.5% and 49.4%-53.0% respectively in bacteria suspension and microbial inoculum additions, net photosynthetic rates in leaves were increased by 118.5%-147.1% and 137.6%-156.9%, and the contents of soluble protein were increased by 37.0%-49.3% and 37.7%-72.6%, respectively. For the bacteria suspension treatment, the activities of SOD, POD and CAT in leaves were increased by 25.8%-36.6%, 40.9%-55.9%, 24.0%-29.2%, and the activities of SOD, POD and CAT in leaves under microbial inoculum treatment were increased by 36.9%-42.6%, 82.7%-92.6% and 43.3%-52.2%, respectively, with the stimulative effects on antioxidation enzymes in rice leaves being higher than those of bacteria suspension. Compared with cadmium treatment, the contents of MDA and O₂^-· in rice leaves were reduced by 44.8%-54.7%, 29.4%-41.9% and 9.9%-10.2%, 3.0%-7.1% in microbial inoculum and bacteria suspension treatments, respectively. In contrast, the contents of flavonoids and total phenols were increased by 125.4%-135.7%, 100.8%-119.4% and 139.4%-146.7%, 115.0%-134.7%, respectively. In summary, P. aeruginosa and the microbial inoculum could promote rice seedling growth by improving root vigor and photosynthetic rate, as well as the contents of flavonoids and total phenols, which led to the fact that P. aeruginosa could significantly alleviate the stress of cadmium on rice.

Biological characteristics of bacteriophages infecting three typic rhizobia of legume

LIU Jun-jie, LIU Zhu-xiu, YU Hao, YAO Qin, YU Zhen-hua, WANG Guang-hua

2019, 30(8):  2775-2782.  doi:10.13287/j.1001-9332.201908.029

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Bacteriophages infecting rhizobia of legume leads to a significant decrease in the number of rhizobia in soil and nodulation in legume, which finally affects nitrogen fixation and remarkably reduces crop yield. However, limited studies have focused on bacteriophages of rhizobia. In this study, three typic rhizobium strains of Bradyrhizobium diazoefficiens USDA110^T, Sinorhizobium sojae CCBAU05684^T and Sinorhizobium meliloti USDA1002^T were used as the host bacteria. From each host, three rhizobiophages were isolated from an agricultural black soil with double-layer plate method. We isolated nine rhizobiophages and investigated their morphological feature and biological characteristics. The results showed that the phages of SMM (infecting Sinorhizobium meliloti USDA1002^T) and BDM (infecting Bradyrhizobium diazoefficiens USDA110^T) belonged to Myoviridae family, while phages of SSS (infecting Sinorhizobium sojae CCBAU05684^T) belonged to Siphoviridae family. The optimal multiplicity of infection for nine phages ranged from 0.001 to 1.0. The one-step growth curve showed that the latent and rising periods of BDM were remarkably longer than that of SMM and SSS, but the bust size was minimal. Nine phages had the strongest infecting activity at 30-40 ℃ and at neutral pH condition. Comparative analysis showed that the biological characteristics of phages infected with the same host were different, with the differentiation being smaller than that of phages infected with different hosts.

Spatial management strategy of Zhujiajian Island based on island ecological vulnerability simulation

XIE Zuo-lun, LI Xiu-zhen, JIANG De-gang, YANG Bin, LIN Shi-wei, CHEN Shen-liang

2019, 30(8):  2783-2792.  doi:10.13287/j.1001-9332.201908.025

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In the past decade, the number of islands fixed link with mainland has been increasing rapidly. The construction of such projects improves the accessibility of islands, which results in a rapid increase of tourists and economic income. However, the rapid change of land use and increases of tourists will make the islands more vulnerable. It is urgent to formulate ecosystem management strategy for island ecosystems based on the scientifical prediction of the island ecological vulnerability and accurate identification of sensitive areas. Island ecological vulnerability assessment model was used to evaluate the ecological vulnerability of Zhujiajian Island. Taking 2015 as the starting date, we simulated the changes of tourists and land use, as well as the changes of island ecological vulnerability in the next 20 years. Then, the management strategy was formulated based on the vulnerability assessment and sensitive analysis. The results showed that the ecosystem of Zhujiajian Island was in good condition now, with limited area at moderate and severe vulnerable status. With the rapid increases of tourists and island development intensity, the ecological vulnerability of the island tended to more vulnerability with the increases of severe vulnerability and shrink of low vulnerability. According to the vulnerability assessment and sensitivity analysis, the Zhujiajian Island could be divided into prohibited development zones, restricted development zones and conditional development zones with different ecosystem management strategies.

Dynamics and spatial pattern prediction of lakes in the northern Tanggula Mountains, Tibet, China

ZHANG Lu, LI Bing-zhang, GUO Ke-ji, LIU Feng, ZONG Ga, LI Xin-yu, LYU Yong-lei, OUYANG Zhi-yun

2019, 30(8):  2793-2802.  doi:10.13287/j.1001-9332.201908.035

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This study assessed the dynamics of lakes in the north Tanggula Mountains in Tibet (NT area) and predicted the spatial changes. We used object-oriented classification and a spectral-angle vector change detection method to generate ecosystem distribution data for the NT area at five-year interval between 2000 and 2015. Based on this dataset, we measured the spatial pattern of lake dynamics and related geophysical and meteorological factors. A boost regression tree model was used to examine the contribution of these variables to lake area change, which were further used in a GEOMOD model to predict the distribution of lakes in 2030. The results showed that the area of lakes increased by 14.2% between 2000 and 2015, which was one of the main forms of ecosystem change in the NT area. In the study region, the area of 10 lakes out of the total 15 lakes with an area greater than 10 km² increased and that of another five lakes decreased with a relatively low shrinkage ratio. Both the mean site area and site number of lakes increased, and the percentage of large lake sites increased slightly. Lakes located in areas with high altitude, high slope, low tempe-rature, low precipitation, or near glaciers had a higher probability of size increase. Locales near the current lake sites with low temperature, precipitation, and slope tended to become new parts of extant lakes. Following the trend of the last 15 years, lakes in the NT area would increase by 119 km² by 2030, with the main form of lake expansion changing from inundation of area around large lakes to area around smaller sites.

Potential of renewable energy development on abandoned mine areas: A case study in Liao-ning Province, Norheast China

QUAN Shi-miao, XI Feng-ming, WANG Jiao-yue, YIN Yan, PEI Zhong-jian, ZHAO Fu-qiang

2019, 30(8):  2803-2812.  doi:10.13287/j.1001-9332.201908.039

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Under the background of domestic and international pressure of carbon emission reduction and the requirement of energy structure adjustment, renewable energy development is under great pressure in China. Renewable energy development on abandoned mine areas has great potential due to its large area. It has great significance to develop renewable energy on abandoned mine areas for China’s energy strategy. This study proposed the development scenarios of biomass energy and solar energy and estimated the development potential of renewable energy on abandoned mine areas in Liaoning Province. The results showed that the area of abandoned mine areas in Liaoning Pro-vince is 1227.6 km², the potential of renewable energy development is large, and the potential of renewable energy in each scenario is quite different. In scenario 1, with the goal mode of maximizing the generation of photovoltaic power, the total generating capacity is 79.4 TWh, the total coal discount is 32.1 Mt standard coal, and the carbon reduction is 79.1 Mt CO₂. In scenario 2, with the goal mode of maximizing biomass energy utilization, the total power generation from photovoltaic and biomass energy is 31.2-33.1 TWh, the total coal discount is 12.7-13.4 Mt standard coal, and the carbon emission reduction is 31.1-33.0 Mt CO₂. In scenario 3, with the goal mode of maximizing comprehensive utilization of mine energy and consideration of ecological restoration, the total gene-rating capacity from photovoltaic and biomass energy is 62.3-63.7 TWh, the total coal discount is 25.1-25.7 Mt standard coal, and the carbon emission reduction is 62.1-63.5 Mt CO₂. Under the three scenarios, the generation capacity range of is 31.2-79.4 TWh, accounting for 15.3%-38.9% of the total power consumption in Liaoning Province in 2016, which could be converted into 12.7-32.1 Mt standard coal, and contribute to a reduction of 31.1-79.1 Mt CO₂ emission. The calculations of new energy development potential on abandoned mine areas and quantification of its capacity of alternatives to fossil energy will be helpful for carbon emission reduction, energy structure adjustment, and the recovery of the mining ecosystem.

Effects of biological organic fertilizer on rhisosphere soil bacteria community and root rot diseases of continuous cropping Angelica sinensis

WANG Wen-li, LI Juan, ZHAO Xu

2019, 30(8):  2813-2821.  doi:10.13287/j.1001-9332.201908.030

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Understanding the effects of biological organic fertilizer DZF-363 on the growth, root rot diseases, and the structure and function of soil microbial community of Angelica sinensis could provide theoretical basis for the adjustment and improvement of soil environment in the rhizosphere of continuous cropping. Taking 2-year continuous cropping A. sinensis and its rhizosphere soil as test objects, with control (without any pesticides, micro-fertilizer, CK), pesticides groups (15% chlorpyrifos and 50% carbendazim, N), and DZF-363 (DZF) treatments, microbial community structure, and urease and phosphatase activities in rhizosphere soil were figured out by high throughput sequencing and colorimetric method. The results showed that the yield of DZF-363 group was 18.8% higher than CK and 6.8% higher than N. The root rot disease index in the DZF was reduced, with a control effectiveness of 52.0%. The activities of urease, neutral phosphatase and alkaline phosphatase in rhizosphere soil were significantly increased during the growing season, and the urease acti-vity increased by 52.4%, 13.9%, 10.3%, neutral phosphatase activity by 15.5%, 10.2%, 10.3%, alkaline phosphatase activity by 10.3%, 4.4%, 4.0% compared with CK during seedling and middle, and harvesting stages, respectively. The acid phosphatase activity increased by 15.6% and 8.2% at middle and harvesting stages, respectively. The proportion of Actinobacteria in CK, N and DZF groups was 11.3%, 10% and 20%, respectively. The proportion of unidentified Bacillibacteria and Actinobacteria was larger in DZF than in the CK and N groups. The Shannon index was significantly increased by DZF. There was positive correlation between Shannon and Simpson indices with the yield of A. sinensis, while negative correlation with the root rot disease. Therefore, the application of DZF-363 could strongly improve the diversity of soil bacteria in the rhizosphere, alter the soil bacterial community structure and rhizosphere soil urease and phosphatase activities, reduce the occurrence of root rot diseases, and thus increase the yield.

Trophic niche of medium-form and dwarf-form of purple flying squid Sthenoeuthis oualaniensis in the central and western South China Sea

HUANG Jia-xing, GONG Yu-yan, XU Shan-nan, CHEN Zuo-zhi, ZHANG Jun, YU Wen-ming

2019, 30(8):  2822-2828.  doi:10.13287/j.1001-9332.201908.021

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To explore the characteristics of carbon and nitrogen stable isotope and trophic niche between two forms (medium-form and dwarf-form) of the purple flying squid Sthenoteuthis ouala-niensis, we collected samples from the central and western South China Sea in August 2017 to analyze the values of carbon and nitrogen stable isotope and the changes of trophic level for different mantle lengths. We further compared the trophic niche differences of the two forms populations. The results showed that for the medium-form, the δ¹³C value ranged from -19.54‰ to -18.10‰ and the δ¹⁵N value ranged from 7.79‰ to 9.45‰. The average trophic level of medium-form was 2.90 and ranged from 2.72 to 3.21. For the dwarf-form, the δ¹³C value ranged from -19.69‰ to -18.43‰, and the δ¹⁵N value ranged from 8.02‰ to 8.99‰. The average trophic level of the dwarf-form was 2.91 and ranged from 2.79 to 3.08. There were significant differences of δ¹⁵N but no differences of δ¹³C values between the medium-form and dwarf-form of purple flying squid. The mantle length had a significant impact on δ¹³C and δ¹⁵N, with the value of δ¹⁵N increasing with the mantle length. The trophic niche breadth and the trophic level of the medium-form purple flying squid were more diverse than those of dwarf-form.

Variations in the mean trophic level and large fish index of fish community in Haizhou Bay, China

WU Xiao-tong, DING Xiang-xiang, JIANG Xu, XU Bin-duo, ZHANG Chong-liang, REN Yi-ping, XUE Ying

2019, 30(8):  2829-2836.  doi:10.13287/j.1001-9332.201908.033

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Based on the bottom trawl surveys in spring (May) and in autumn (September to October) from 2011 to 2017 (except 2012) in Haizhou Bay, variations in the mean trophic levels (MTL) and large fish index (LFI) of fish community were examined to understand the changes of fish community structure in Haizhou Bay. The results showed that the dominant fish species were Hexagrammos otakii, Enedrias fangi, Syngnathus acus, Pseudosciaena polyactis and Saurida elongata, which had obvious seasonal variation. The mean trophic level of fish community varied significantly among different years and seasons. Generally, MTL in autumn was higher than that in spring, and the variation of which in autumn always lagged behind that in spring. The result of LFI calculation showed that the large fish resources declined and fish community structure in Haizhou Bay showed an obvious tendency of miniaturization in recent years.

The role of submerged group ecological media box in repairing black and odorous water body

GUO Wei-chao, WANG Chen-yi, LI Lin-lin, TENG Li-hua, YANG Na, WANG Feng-ling

2019, 30(8):  2837-2844.  doi:10.13287/j.1001-9332.201908.032

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As a conventional technology, the ecological floating bed has been widely used to repair waste water body. However, it can only repair the surface oxygen-enriched water, and has limited ability to repair the lower anoxic water. To meet the needs of the restoration of black and odorous water body, we designed a submersible ecological media box (submerged group) and compared it with traditional ecological floating bed (floating bed group). Water quality of black and odorous water before and after the restoration was examined, with the growth status of aquatic plants and the accumulation ability of N and P being investigated. The results showed that with the prolongation of repairing time, the removal rate of each pollutant increased gradually in both treatments. The removal ability of the submerged group for TN, NH₄⁺-N, TP was better than that of the floating bed group, but its ability to remove COD_Mn was slightly inferior than that of the floating bed group. Plants (Vallisneria natans) in the submerged group grew better than that in the floating bed group (Acorus cala-mus), with similar patterns of the absorption and accumulation capacity and removal rate of TN and TP. In addition, the plasma membrane permeability and malondialdehyde content of V. natans were lower than that of A. calamus and the chlorophyll content of A. calamus was higher than that of V. natans, indicating that V. natans is more suitable for planting in black and odorous water bodies. Thus, the submersible ecological media box is a new in-situ integrated remediation device, which is more suitable to repair the black and odorous water.

Ecotoxicological effects of transgenic mCry1Ac maize (BT799) on zebrafish

DONG Shan-shan, ZHANG Di-ni, ZHANG Zhen-hua, YU Ci-gang, LIU Yan, ZHAO Hai-ming, WANG Chang-yong

2019, 30(8):  2845-2853.  doi:10.13287/j.1001-9332.201908.031

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The safety of feed derived from genetically modified (GM) crops is one of the focuses of attention. To evaluate the ecotoxicological effects of transgenic mCry1Ac maize (BT799) on fish, zebrafish (Danio rerio) were fed extruded feeds containing either 20% GM maize (GMF) or its parental control maize (PF), GM maize meal (GMM) or its parental control maize meal (PMM), and a control commercial feed (CF), respectively. The growth performance, histopathology, reproduction, antioxidant enzyme activity and mRNA expression levels of sensitive protein in the liver were investigated over the course of a 98-day feeding trial. The results showed that transgenic mCry1Ac maize had no significant effect on growth, histopathology of the liver, brain and intestinal tract, fecundity, hatching rate of fertilized eggs, superoxide dismutase (SOD), catalase (CAT) activity, mRNA expression levels of SOD and CAT, or heat shock protein 70 (HSP70) and vitellogenin (VTG) in the liver. However, zebrafish fed the commercial feed exhibited significantly greater weight, longer length, and higher specific growth rate than those fed feeds (GMF and PF) and maize meals (GMM and PMM). The hatching rate of zebrafish in the feed groups was significantly lower than that of the maize meal groups and the commercial feed group. The mRNA transcriptional levels of VTG were significantly higher in the liver for the feed groups (3.85±0.76) than that for the maize meal groups (1.60±0.56). These results suggest that transgenic mCry1Ac maize has no ecotoxicological effects on zebrafish. However, the differences in nutrient composition and palatability between the extruded experimental feeds and the commercial feed would lead to significant diffe-rences in some parameters.

Reviews

Tree seedling distribution, regeneration mechanism and response to climate change in alpine treeline ecotone

SHAO Jia-yi, DU Jian-hui, LI Sheng-fa, HUANG Yi-xin, LIANG Wei-nuo, LIAO Jia-qiang

2019, 30(8):  2854-2864.  doi:10.13287/j.1001-9332.201908.007

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Tree seedlings are one of the important components in alpine treeline ecotone, whose regeneration is crucial to treeline migration in response to climate change. We analyzed the spatial distribution, regeneration of tree seedlings and their responses to climate change in treeline ecotone in recent decades. The spatial distribution of tree seedlings in treeline ecotone is dominated by diffuse and clustered forms, with different indicative significance for spatial dynamics of treeline. At global scale, the altitude distribution limits of tree seedlings are usually related to the length and average temperature of growing season, along with the species characteristics. However, precipita-tion plays an important role at regional scale. The initial stage of seedling recruitment is restricted by seed source, which determines seed distribution and germination to a great extent. Microenvironment facilitates seedling regeneration by providing shelter for establishment and improving their survival rate. The regeneration process is more relevant to multiple biotic, abiotic factors and their interactions. With global warming, rising temperature in treeline ecotone and more precipitation are more suitable for seedling regeneration of treeline species. The expansion of seedlings to higher elevations could be considered as the portent of timberline upwards migration. Due to species-specific adaption strategy, however, some trees only increase seedling density and timberline location is constant. In the future, it is necessary to take precise dating techniques, such as tree-ring and ¹⁴C dating, and conduct long-term in-situ monitoring and indoor simulation experiments. To provide scientific basis for mountain ecosystem restoration and conservation, we should strengthen the studies on spatial patterns and regeneration mechanism of seedlings in treeline ecotone at multiple spatio-temporal scales, the adaptation strategies of tree seedlings in different types of treeline ecotone and treeline dynamics prediction.

Microbial characteristics and eco-health implication of mineral spring water in Wudalianchi, Northeast China

GAO Si-meng, WEN Yu-juan, ZHANG Wen-qing, ZHANG Da-zhi, YANG Yue-suo

2019, 30(8):  2865-2874.  doi:10.13287/j.1001-9332.201908.036

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Mineral spring water is a top quality potable groundwater resource formed by long-term groundwater-rock interaction in aquifer. Mineral spring water is rich in minerals and trace elements which are beneficial for human health. Given the current serious water pollution and environment deterioration, it is of great significance to re-recognize the ecological and health effects of mineral water based on new scientific and technological achievement. The Wudalianchi scenic area in Heilongjiang Province has abundant mineral water and peloid resources, which supported the development of tourism and convalescence and have been used in medical and health care for more than 100 years. However, it is threatened by resource reduction, environmental pollution, and other problems. Here, we reviewed the formation process, distribution, hydro-biochemical characteristics and health effects of the Wudalianchi mineral springs, with particular focus on the advances of microbial studies in this area. We also proposed the future research prospective for the Wudalianchi mineral water. To better protect and utilize the Wudalianchi mineral water, it was recommended that a green eco-agriculture practice in reducing chemical fertilizers should be adapted in the surrounding farms of Wudalianchi. Along with the development of tourism and recuperation resources, it is necessary to establish a framework of pollution risk assessment and control, and strictly reduce potential emerging pollutants to eco-geological environment.

Distribution, diffuse, and removal of tetracyclines and sulfonamide antibiotic resistance genes in wastewater treatment plant: A review.

WANG Guo-lan, FENG Jin-lu, LUO Ling, LOU Li-ping

2019, 30(8):  2875-2882.  doi:10.13287/j.1001-9332.201908.028

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The contamination of antibiotic resistance genes (ARGs) caused by abuse of antibiotics has attracted more and more attention. Due to their low price, tetracyclines and sulfonamides are widely used. The plenty of residual tetracyclines and sulfonamides is discharged into wastewater treatment plant (WWTPs), with consequent ARGs pollution. To understand the current status of ARGs contamination and removal efficiency, we summarized the distribution and spread mechanism of tetracyclines and sulfonamides ARGs, and further emphasized the ARGs removal efficiency across different treatment technologies. Based on the current knowledge and lack of ARGs, future work were proposed, such as investigating ARGs contamination in WWTPs, improving ARGs removal technologies, exploring spread mechanisms of ARGs.