Chinese Journal of Ecology

Community composition, plant species diversity and soil nutrient content of endangered plant Tetraena mongolica Maxim.

DU Zhong-yu, HE Yi-ming, FANG Peng-peng, DUAN Yi-zhong, LU Ke

2020, 39(11): 3537-3548. doi:10.13292/j.1000-4890.202011.016

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Tetraena mongolica Maxim. is a relict and endangered monotypic genus species from the ancient Mediterranean flora and a second-degree endangered species in China. It is one of the dominant species in plant community in arid and semiarid regions of Northwest China, and thus plays an important role in maintaining ecosystem structure and function. Based on field investigation of natural T. mongolica community in Northwest China, we analyzed species composition, species diversity, and the correlation between species diversity and soil physicochemical properties. The results showed that: (1) T. mongolica community features simple composition structure and low species diversity. With a total of 64 species, 42 genera and 15 families recorded, most species are subshrubs and perennial herbs from Asteraceae, Poaceae and Chenopodiaceae. There were significant differences in species diversity among different T. mongolica plant communities (P<0.05). Plant species richness, Shannon index and Simpson index of Qianligou community were the highest (24.00, 2.92 and 0.93, respectively). The Pielou index in Qianlishan community was the highest (0.98). (2) There were significant differences in soil nutrient contents among different T. mongolica plant communities (P<0.01). Soil available nutrients (available nitrogen, available phosphorus, available potassium) of Haibowanqu and Hainanqu were higher than that of other communities. Soil organic content in Qianlishan was the highest, whereas soil moisture was the highest in Qianligou. Species diversity ofT. mongolica community was significantly positively correlated with soil available phosphorus (P<0.05). Our results provide scientific support for understanding the T. mongolica plant community and theoretical basis for protecting the germplasm of relic T. mongolica.

Spatiotemporal distribution characteristics of temperature on the surface layer of cutting gap of Phyllostachys edulis forest.

SHEN Jing-xin, FAN Shao-hui, LIU Guang-lu, CHEN Ben-xue, WU Chang-ming, CAO Bi-feng

2020, 39(11): 3549-3557. doi:10.13292/j.1000-4890.202011.024

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We analyzed the temporal and spatial distribution of the near-surface temperature in cutting gaps of moso bamboo (Phyllostachys edulis) forest in different slope directions near the Yong’an Bamboo Forest Ecological Positioning Observation and Research Station in Fujian Province. Nine observation locations were set up in the center of the forest gap and in the four directions of the south, north, east, and west through the center. The Kestrel 3000 portable weather monitor was used to measure surface temperature and air temperature at a height of 1.5 m at each site. The results showed that the spatial distribution of temperature in cutting gaps of different slope directions was significantly different, showing asymmetry in the spatial distribution of temperature. The hightemperature areas in the gaps of two slope directions were distributed on one side of the gap, while the distribution directions of hightemperature areas of two slope directions were also different. The difference between surface temperature and temperature at 1.5 m height promoted heat transfer in forest gaps. The daily variation of temperature in gaps of the two slope directions was singlepeak type, with the highest temperature at noon. The average temperature in gaps of the two slope directions was significantly different (P<0.01), with temperature on the west slope being higher than that on the north slope. Our results indicated that surface temperature and temperature at 1.5 m height within gaps varied with slope directions, positions within gaps and time. Heat transfer in the gaps enhanced environmental heterogeneity, thus affecting bamboo shoot emergence in the gaps. Our results provide evidence for understanding the recovery of logged moso bamboo forest.

Effects of root characteristics of shrub community on soil anti-scourability in the Jiajin Mountains, Sichuan Province.

ZHANG Rong, DONG Hong-jun, ZHOU Run-hui, YU Fei-yan, WANG Min, CHEN Cong-lin, YU Jing, HAO Jian-feng

2020, 39(11): 3558-3566. doi:10.13292/j.1000-4890.202011.012

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We examined the impacts of shrub community roots on soil antiscourability in alpine gorge area in Jiajin Mountains of Sichuan Province. The Ward cluster analysis method was employed to divide communities into different types. Field sampling and undisturbed soil erosion experiment were conducted to analyze the root distribution characteristics of different community types and their effects on soil erosion resistance. The results showed that shrub communities in Jiajin Mountains could be divided into four types, with root length density and root surface area density following the order ofQuercus semicarpifolia+Salix wallichianaFragaria vesca community (type Ⅳ) > Rhododendron vernicosumLigularia fischeri community (type Ⅰ) >R. tatsienense+Cotoneaster subadpressusPteridium aquilinumvar. latiusculumcommunity (type Ⅱ) >Q. semicarpifolia+C. subadpressusP. aquilinumvar. latiusculum community (type Ⅲ); (2) Each community was dominated by roots of <1 mm diameter, while community type Ⅳ had the highest root biomass; (3) Results of the undisturbed soil erosion test showed that soil sand content in each community type decreased over time and then tended to be gentle, while the soil antiscourability coefficient was fluctuatingly increased with erosion time. The soil of type Ⅳ had stronger antiscourability; (4) Results of correlation analysis showed that roots of 0.5-1 mm diameter, total root weight density and total root volume were the main factors influencing soil anti-scourability of shrubs in Jiajin Mountains. Our results provide a basis for studies of soil erosion pattern of shrub community in the alpine gorge area.

Quantitative analysis of the socioeconomic development impacts of the Three-North Afforestation Program on Horqin Sandy Land.

WU Jin-zhou, ZHENG Xiao, GAO Tian, SONG Li-ning, ZHANG Ting

2020, 39(11): 3567-3575. doi:10.13292/j.1000-4890.202011.018

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The Three-North Afforestation Program (TNAP), the earliest ecological afforestation program in China, aims to improve the ecological environment and promote the socioeconomic development in the ThreeNorth region (TNR). While most previous studies focused on the effects of ecological programs on the ecological environment, few studies have quantified their effects on the socioeconomic development. In this study, the structural equation model was used to quantify the relationships among the TNAP, economic growth, and social development from 2000 to 2016 in eight counties of the Horqin Sandy Land, the critical construction area of the TNAP. The results showed that: (1) the TNAP in this area increased forest area by 370000 hm² and forest cover by 8.52% following a direct investment of 987 million yuan; (2) the TNAP accounted for about 55% contribution of the local social development by improving employment structure and electricity consumption over the 17 years. Moreover, the TNAP increased economic growth with a direct contribution of 4% and an indirect contribution of 52%, which have changed the patterns of employment and industry and increased farmers’ income. All these changes have a positive influence on poverty alleviation. Our results could provide scientific support for further construction of the TNAP and reference for further studies on the effects of ecological programs on socioeconomic development.

Effects of alterations in litter inputs on soil respiration of Pinus tabuliformis forests at different ages.

HAN Shang-jun, HAN Hai-rong, CHENG Xiao-qin, DONG Ling-ling, CAI Meng-ke, SHANG Tian-xiong

2020, 39(11): 3576-3587. doi:10.13292/j.1000-4890.202011.037

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To explore the relationship between litter inputs and soil respiration in different aged forests, we carried out a leaf litterfall manipulation experiment in Pinus tabuliformis forests inLiaohe River, Northern China. We examined the sensitivity of soil CO₂ emissions to alteration in litter inputs. There were nine experimental plots with three stand ages (middle-aged, nearly mature, and mature stands). Treatments included adding (by doubling) of aboveground litter (DL) (including leaf, twig, bark), removing all aboveground litter (NL), removing aboveground litter and root (NI), and control (CK). Soil respiration was measured with a LI-8100 infrared gas analysis. The results showed that alterations in litter inputs significantly affected soil temperature and moisture in middle-aged stand. Soil temperature was significantly increased in NL treatment in middle-aged and mature stands, whereas soil moisture was significantly-reduced in NL treatment in middle-aged and nearly mature stands. Alterations in litter inputs did not affect soil temperature in nearly mature stand and soil moisture in mature stand. Soil respiration rate was significantly increased in DL treatment, whereas soil respiration rate was significantly decreased in NL treatment. The magnitude of increment in soil respiration in DL treatment was greater than that of the decline in NL treatments. The relative contributions of different soil respiration components to total soil respiration following the order mineral soil respiration > litter respiration > root respiration in middle aged and nearly mature stands, and following the order of mineral soil respiration > root respiration > litter respiration in mature forest. The contribution of mineral soil respiration decreased with increasing stand age, but an opposite pattern for the contribution of root respiration. Mineral soil respiration and root respiration were significantly differentbetween middleaged stand and mature stand. Litter removal had significant effects on soil microclimate, which affected soil respiration. Soil respiration in DL treatments was mainly affected by soil temperature. The combined effects of soil temperature and moisture explained 60.2%-77.5% of the variation of soil respiration in different aged P.tabuliformis forests. Soil respiration under different treatments had a significant positive correlation with fine root biomass. The responses of soil respiration to the alteration in litter inputs depended on stand age. Our findings indicate that alterations of litter inputs should be considered in predicting soil respiration under climate changes.

Soil physical characteristics in different types of Pinus tabuliformis mixed forest.

DU Man-yi, ZHANG Lian-jin, PEI Shun-xiang, FA Lei, FENG Huan-ying, GUO Jia, WU Di, XIN Xue-bing

2020, 39(11): 3588-3595. doi:10.13292/j.1000-4890.202011.021

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Long-term and large-scale Pinus tabuliformis pure plantations have many ecological problems. Choosing tree species with harmonious interspecific relationships is the key for successful stand conversion from pure forests to mixed forests. To provide scientific support for the rational configuration of tree species and sustainable forest management, we explored soil physical properties in different mixed stand types, including P. tabuliformis pure forests, P. tabuliformis and Quercus wutaishansea mixed forests, and P. tabuliformis and P. armandii mixed forests in South Shanxi. Results showed that (1) tree species mixture changed soil bulk density and soil porosity. The mixture ofP. tabuliformis and Q. wutaishansea significantly reduced soil bulk density and increased total soil porosity, capillary porosity, and non-capillary porosity, whereas such changes were negligible in the P. tabuliformis and P. armandii mixed forest. (2) Tree species mixture changed soil water retention characteristics. The maximum moisture capacity, capillary moisture capacity, and field water-holding capacity increased dramatically in the P. tabuliformis and Q. wutaishansea mixed forests, but not for P. tabuliformis and P. armandii mixed forests. (3) Tree species mixture had greater effects on physical properties of topsoil than deeper soil layer, including soil bulk density, porosity, and water holding characteristics. (4) Tree species mixture did not change the vertical patterns of soil properties. With increasing soil depth, soil bulk density increased, whereas total porosity, capillary porosity, non-capillary porosity, maximum moisture capacity, capillary moisture capacity, and field water-holding capacity reduced across different mixed forests.

Diversity of mistletoes along elevation gradient in western Hubei.

HE Zhan, ZHOU You-bing, GAO Rui-ru

2020, 39(11): 3596-3604. doi:10.13292/j.1000-4890.202011.029

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The distribution of mistletoe species (Loranthaceae) correlates to specific host plants and habitats. Here, we investigated the distribution of mistletoe species over 292 plots (20 m×20 m) of subtropical forest community with three transects along an elevation gradient (175-3106 m) in western Hubei. Results showed that there were seven species parasitizing 40 different host plant species. Mistletoes were distributed between the elevation of 194 m and 2011 m. Species diversity increased and then decreased with increasing elevation, and concentrated from 600 m to 1000 m, showing a unimodal pattern. The parasitic intensity of different mistletoes on host plants depended on specific species, with mistletoes being generally found on the tall deciduous trees. The “mid-elevation peak” in mistletoe diversity was observed along the elevation gradient in western Hubei, which may be related with host availability and diversity.

Effects of groundwater depth on biomass allocation and growth of Populus euphratica seedlings in desert riparian forest in the middle reaches of Shule River.

BAI Xue, ZHAO Cheng-zhang, KANG Man-ping

2020, 39(11): 3605-3612. doi:10.13292/j.1000-4890.202011.017

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Plant biomass allocation pattern has important ecological and evolutionary significance for plant adaptation strategies, functional trait construction, and reproductive regeneration model. In this study, the standardized major axis (SMA) method was used to examine biomass allocation and allometric relationship of Populus euphraticaseedlings in desert riparian forest along a moisture gradient in the middle reaches of Shule River. Three plots were selected based on the distance from the river bank: near water area (plot I), medium water area (plot II) and far water area (plot III). The results showed that, with decreasing groundwater depth, the height of Populus euphratica seedling community increased (P<0.05) but the density decreased (P<0.05), and the coverage first decreased and then increased. In plot I and plot II, root-shoot ratio was greater than 1, and the increase rate of aboveground biomass was lower than that of belowground biomass. In plot III, the root-shoot ratio was close to 1, and the increase rate of aboveground and belowground biomass was almost isometric relationship. The leaf biomass fraction and root biomass fraction exhibited a decreasing trend (P<0.05), while the branch biomass fraction showed a gradually increasing trend (P<0.05), and the twig number, leaf number, crown, root length, root average diameter, root surface area and fractal dimension were significantly increased (P<0.05). The biomass allocation patterns and growth characteristics of Populus euphratica seedlings in riparian forests of Shule River reflected the environmental plasticity mechanism of plant functional traits in heterogeneous habitats, providing a theoretical basis for understanding the habitat adaptability of plants in desert riparian forest.

Species composition, flora and invasion hazard of alien plants in Huangjinhe National Wetland Park.

XIE Yong, XU Yong-fu, YOU Jian-rong, LI Jia-xiang, XIONG Lei, LI Chang

2020, 39(11): 3613-3622. doi:10.13292/j.1000-4890.202011.005

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The impacts of alien species invasion on wetlands are an important issue in ecological research, but there are few reports on reservoir wetlands. Based on field investigation of 10 sampling transects across five landuse types, we analyzed species composition, flora characteristics and hazard degree of alien plants in Huangjinhe National Wetland Park in Pingjiang, Hunan Province. The results showed that: (1) A total of 46 alien plant species belonging to 37 genera and 17 families were recorded, with the dominant growthform of annual and biennial herb (33 species) accounting for 71.74% of the total alien species. Asteraceae (9 species) and Poaceae (7 species) were the most speciesabundant families, accounting for 19.57% and 15.22% of the total species richness, respectively. (2) South America and North America were mainly the origins of alien species, indicating that alien plants originated from American continent have better adaptability in the park. (3) The proportions of tropical families and genera were significantly higher than those of temperate families and genera, indicating that flora of the alien plants had a strong tropical nature. (4) 42 alien plant species showed different degrees of invasive hazards. The species (32 species) with the first three levels of invasive hazards accounted for 69.57% of the total species, five species out of which, including Bidens frondosa,Eichhornia crassipes, caused the malignant invasive hazards. (5) America was the main origin of alien plants in the park and in other wetlands (Dongting Lake, Nanjishan and Xuanmenwan) from the same latitude. Plant species of Compositae and annual herbs were most dominant. The similarity coefficients of species between Huangjinhe and other wetlands decreased with the increases of distance, with the highest similarity being with Dongting Lake. The proportion of species only found in Huangjinghe was 32.61% (15 species). The long history of human disturbance, diverse land use types and complex habitat characteristics are the main reasons for the composition and invasion hazards of alien plants in reservoir wetlands. To prevent and control the invasion of alien plants, it is suggested to combine strict control of human introduction and timely treatmentaccording to different habitat types.

Distribution characteristics of active components in soil organic carbon across typical plant communities in Yancheng coastal wetlands.

XI Pan, DONG Qian, ZHANG Ya-nan, LI Xiang, XIA Wen-wen, XU Chi, LIU Mao-song

2020, 39(11): 3623-3632. doi:10.13292/j.1000-4890.202011.010

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The active components of soil organic carbon are sensitive indicators of carbon stock change, which can timely reflect the turnover and dynamics of soil organic carbon pool. In this study, soil samples at 0-10 cm (surface layer), 10-30 cm (middle layer) and 30-60 cm (deep layer) depths of four typical plant communities were collected in Yancheng coastal wetlands. The relationships between soil total organic carbon (TOC), easily oxidizable carbon (EOC), dissolved organic carbon (DOC), particulate organic carbon (POC) and soil environmental factors and aboveground biomass (AGB) were examined. The results showed that: (1) TOC content varied greatly in different plant communities, whereas the differences in soil EOC and DOC contents were relatively minor. TOC content declined with soil depths except for the Spartina alternifloracommunity, which was slightly higher in deep layers. POC content gradually decreased with soil depths. (2) Redundancy analysis results showed that AGB and soil pH had the highest single explanatory power for the variation of soil organic carbon component content in the three soil layers. With increasing soil depth, the explanatory power of total reducing substances (RS) showed an upward trend. The separate explanatory power of soil water content (SWC) in surface and middle layers was the lowest. Soil water content had little effect on the content of soil organic carbon components. (3) EOC was significantly positively correlated with total phosphorus (TP) and total nitrogen (TN), negatively correlated with pH in surface layer, and had no correlation with soil factors in the middle and deep layers. DOC was significantly positively correlated with AGB, TP, and RS in surface layer, positively correlated with TN, TP and SWC in the middle layer, and negatively correlated with pH in deep layer. POC was significantly positively correlated with AGB, TP and RS in surface and middle layers, but not in the deep layer. Our results indicated that AGB and soil pH significantly affected the contents of soil organic carbon components in the three soil layers, while the effect of soil redox status was more significant with the increasing soil depths. The relative contents of soil organic carbon components and their influencing factors were quite different, depending on community types, soil layers, and organic carbon component types.

Contrasting impacts of vapor pressure deficit on gross primary productivity in two typical grassland ecosystems in China.

MENG Ying, JIANG Peng, FANG Yuan

2020, 39(11): 3633-3642. doi:10.13292/j.1000-4890.202011.011

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Both soil water content (SWC) and vapor pressure deficit (VPD) play an important role in regulating plant photosynthesis. Relative to the SWC, the impacts of VPD on gross primary productivity (GPP) are still largely unknown. In this study, we chose a water-limited temperate steppe in Inner Mongolia (NM station) and a humid but temperaturelimited alpine shrub-meadow in Tibet (HB station) to examine the responses of GPP to VPD. According to the ratio of SWC in a specific study period to multiyear average SWC value (RSWC), data in both sites were classified into three groups: driest 25% (the top 25%), middle 50% (the middle 50%), and wettest 25% (the bottom 25%). Our results showed that there were positive relationships between VPD and GPP under three SWC levels in HB station (P<0.05), without differences under the same SWC level (P>0.05). By contrast, GPP declined with increasing VPD under the driest and middle SWC levels in NM station, whereas such negative correlation was translated into a positive one under the wettest SWC level (P<0.05). Significant differences were found in the slopes of the relationships between GPP and VPD under different SWC levels in the NM station. When only considering the effects of VPD and SWC on GPP, SWC accounted for more than 60% of the variations in GPP under low SWC level in NM station, whereas VPD accounted for 90% of the variations of GPP in HB station. Our results revealed that the waterlimited grassland may be more vulnerable to high VPD in the future relative to the humid but temperature-limited ecosystems. Our results provide an important mechanism support and reference for how the vegetation productivity model couples the atmospheric drought effect into the model and also helpful for predicting the responses and adaptations of vegetation productivity to atmospheric drought in different ecosystems.

Effects of foliar spray dose of selenium-rich nutrient solution on the yield and quality of spring wheat. #br#

LI Wen-shuan, LI Xiao-jun, LI Pei-jun, ZHANG Hai-rong

2020, 39(11): 3643-3650. doi:10.13292/j.1000-4890.202011.007

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Proper foliar spray dose of Serich nutrient solution is important for avoiding leaf damage by excessive dose of sprayed selenium (Se) and realizing Se accumulation in kernel of wheat and cost reduction. In this study, we examined the effects of foliar spray dose of Se-rich nutrient solution (Dorina) on the yield and flour quality of spring wheat (Ningchun 4, being widely cultivated in China). The results showed that 7500 mL·hm-^2 of Se-rich nutrient solution (with Se concentration of 61.5 g·hm^-2) was the best dose, which increased the yield of spring wheat to 600 kg·hm^-2 (with a 11.8% enhancement). The Se content in flour was 6.6 times higher than that in control, while zinc and protein content were increased by 5.4% and 12.4%, respectively. This dose of Serich nutrient solution (Dorina) could meet the demand of Serich wheat production. Our results provide scientific support for its wide use and the development of local selenium industry.

Insect resistance of tomato induced by exogenous methyl jasmonate to Bemisia tabaci. #br#

ZHANG Xiao-xia, HONG Bo, JING Liang-liang, CAO Shuang, JIA Yan-xia

2020, 39(11): 3651-3657. doi:10.13292/j.1000-4890.202011.026

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To clarify the roles of exogenous methyl jasmonate (MeJA) in controlling Bemisia tabaci adults on tomatoes, we measured nutrient content, secondary metabolite content and protein defense enzyme activity in tomato leaves under MeJA treatments in a pot experiment. The results showed that exogenous MeJA treatment reduced nutrient content in tomato leaves. The soluble sugar and protein contents were the lowest and the induction effect was the strongest under the treatment of 0.0225 mmol·L^-1 MeJA after five days. The exogenous MeJA treatment increased the secondary metabolites in tomato leaves, with the strongest induction effect and the highest concentrations of tannin and flavonoid being observed in tomato leaves under the MeJA treatment with application rate of 0.0225 mmol·L^-1 after five days. The exogenous MeJA enhanced the activity of defense enzymes (POD and PPO) in tomato leaves. With the extension of MeJA treatment time (0-14 days), the activity of defense enzymes showed a trend of increasing decreasingincreasing. The POD and PPO activities in tomato leaves were the highest and the induction effect was the strongest at the treatment of 0.0225 mmol·L^-1 MeJA after five days. Different concentrations of the exogenous MeJA application had different control effects on B. tabaci. After five days treatment with 0.0225 mmol·L^-1 MeJA, the best control effect on B. tabaci was observed, reaching 86.96%. In conclusion, the application of exogenous MeJA can increase the resistance of tomato to B. tabaci through reducing nutrient content, increasing secondary metabolite content and protein defense enzyme activity. Our results provide scientific basis for the prevention of B. tabaciin tomato planting and management.

Effects of long-term fertilization on soil nitrogen-transforming bacteria and phosphatesolubilizing bacteria in rainfed cropland of Loess Plateau, China.

LI Chun-yue, XUE Ying-long, WANG Yi, DANG Ting-hui, SONG Yi

2020, 39(11): 3658-3667. doi:10.13292/j.1000-4890.202011.025

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Soil functional microorganisms can promote nutrient transformation in cropland ecosystems and maintain the stability of soil environment. Based on a long-term experiment in Changwu Agro-ecological Experimental Station with six typical fertilization treatments, including no fertilizer (CK), medium nitrogen fertilizer (N₁₂), high nitrogen fertilizer (N₂₄), medium phosphate fertilizer (P₁₂), high phosphate fertilizer (P₂₄), and medium nitrogen and phosphorus fertilizer (N₁₂P₁₂), we explored the effects of fertilization managements on the abundance of soil nitrogen-transforming bacteria and phosphate-solubilizing bacteria by the traditional coating plate count method. The results showed that there were significant differences in the abundance of soil microorganisms involved in nitrogen cycling under different fertilization treatments. The abundance was decreased in the order of aerobic free-living nitrogen-fixing bacteria, ammonia oxidizing bacteria, nitrite bacteria, denitrifying bacteria. Ammonia oxidizing bacteria and nitrite bacteria had a similar trend in single fertilization treatments and they were reduced with the increasing nitrogen and phosphate application levels, while aerobic free-living nitrogen-fixing bacteria showed opposite responses. Inorganic phosphate solubilizing bacteria were more sensitive to nitrogen fertilizer than to phosphate fertilizer. Phosphate fertilizer decreased the abundance of organic phosphate solubilizing bacteria and promoted organic phosphorus mineralization. There were correlations between soil nitrogen-transforming bacteria, phosphate-solubilizing bacteria and soil physical and chemical parameters. The abundance of ammonia oxidizing bacteria was significantly negatively correlated with nitrate content, while positively with pH and field water-holding capacity. The abundance of aerobic free-living nitrogen-fixing bacteria was significantly positively correlated with soil total phosphorus, available phosphorus contents and field water-holding capacity. The abundance of nitrite bacteria was positively correlated with total nitrogen content. The abundance of denitrifying bacteria was significantly positively correlated with soil water content. The abundance of inorganic phosphate solubilizing bacteria was positively correlated with total nitrogen content, but negatively with soil water content. The abundance of organic phosphate solubilizing bacteria was positively correlated with total organic carbon content. Redundancy analysis results showed that soil total phosphorus content had the strongest effect on the abundance of soil nitrogen-transforming bacteria and phosphate-solubilizing bacteria, accounting for 33.2% of the variation in soil bacterial abundance (F=13.9,P=0.002). Our results indicated that the abundance of soil nitrogen-transforming bacteria and phosphate-solubilizing bacteria was significantly affected by the long-term fertilizer management in the rainfed cropland of the Loess Plateau, and that there was a closely synergistic effect between soil nitrogen-transforming bacteria and phosphate-solubilizing bacteria.

Effects of film thickness on growth and nitrogen accumulation of peanut.

ZHANG Jun, HAO Xi, ZANG Xiu-wang, LIU Juan, ZHANG Man, TANG Feng-shou, DONG Wen-zhao, LIU Hua

2020, 39(11): 3668-3675. doi:10.13292/j.1000-4890.202011.028

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To clarify the effects of new standard thickness of film (0.01 mm) on the growth and development of peanut, we compared the effects of different film thickness on soil temperature, nutrient uptake, reproductive growth, yield and quality of peanut in a field experiment. The results showed that the new standard film could increase ground temperature. Compared with the commonly used film thickness of 0.004 and 0.006 mm, the new standard film increased the daily average ground temperature by 2.24 and 1.44 ℃, and the accumulated temperature by 196.90 and 305.05 ℃, respectively. Compared with nonmulching sowing, the new standard film increased daily average ground temperature and accumulated temperature by 4.03 and 547.97 ℃, respectively. The enhancement of film thickness increased the growth process of peanut compared with no mulching, in that 0.01 mm film mulching advanced seedling emergence for 2 days, full-bloom stage for 3 days, and emergence of fruit needles for 2 days. The number of fruit needles, the number of pods, the volume of pods, and the yield significantly were enhanced with the increased mulching thickness. Compared with no mulching, 0.01 mm mulching increased the number of fruit needles, pod volume and yield by 54.44%, 121.65%, and 31.09%, respectively. The thick film was beneficial to nitrogen accumulation and nutrient utilization. However, it will increase the cost to certain extent and has higher requirements on sowing quality.

Effects of intercropping patterns on physiological and growth traits of Coptis chinensis and rhizospheric soil physicochemical properties.

DUAN Yuan-yuan, LIU Xiao-hong, WU Jia-qi, ZHOU Wu-xian, GUO Xiao-liang, YOU Jing-mao, TANG Tao, WANG Fan-fan, GUO Jie

2020, 39(11): 3676-3685. doi:10.13292/j.1000-4890.202011.034

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We investigated the effects of intercropping patterns on physiological and growth traits of Coptis chinensis and rhizospheric soil physicochemical properties under three intercropping systems \[Magnolia officinalis-C. chinensis (CC),M. officinalisFritillaria hupehensis-C. chinensis (FH-CC), andM. officinalis-Scrophularia ningpoensis-C. chinensis (SN-CC) cropping systems\]. Results showed that plant height, fresh weight, leaf area and peroxidase activity ofC. chinensis in the intercropping modes (SN-CC system and FH-CC system) were (19.56%, 14.70%),(91.38%, 4.86%), (28.86%, 16.63%) and (47.10%, 37.46%) higher than those in the CC system, respectively. The physiological/growth comprehensive index of C. chinensis under SN-CC system and FH-CC system was 0.413 and 0.007, respectively. Growth traits of C. chinensis in the intercropping systems were better than those in the monoculture. The intercropping systems were beneficial to the growth ofC. chinensis, with SN-CC system being the optimal. Soil physicochemical properties significantly affected the physiological and growth traits of C. chinensis. Enzymeactivities ofC. chinensis rhizosphere soil significantly affected soil nutrient contents. Sucrase activity, available potassium content and alkaline phosphatase activity were the main soil factors affecting the growth of C. chinensis, with a correlation coefficient of 0.9999, 0.9639 and 0.9094, respectively.

Contribution of photosynthetic carbon fixed by early rice to soil organic carbon in annual double rice cropping system.

FANG Xue-dong, QIN Ming-guang, ZHAN Ming, LIU Zhi-hui, HAN Yu-ling, TANG Lan-lan

2020, 39(11): 3686-3693. doi:10.13292/j.1000-4890.202011.004

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Study on influence of photosynthetic carbon of early rice on soil organic carbon under double rice cropping system at the annual scale is of great significance for understanding the mechanisms underlying cropland carbon cycling and soil carbon sequestration. The distribution of photosynthetic carbon in early rice and its contribution to soil organic carbon were examined using ¹³C pulse labeling at the panicle differentiation (PD) and grain filling stages (GF) of early rice with a pot experiment. The results showed that photosynthetic ¹³C was transferred to both aboveground and belowground after 1 d of labeling. The recovery rate of PD-labeled carbon was 74% at the harvest time of rice, which was significantly higher than that of GFlabeledcarbon (59%). Moreover, partition of PDlabeled carbon to belowground was higher than that of GFlabeled carbon. In both the early and late rice seasons, the contribution of photosynthetic carbon at early rice PD stage to dissolved soil organic carbon (DOC) was significantly higher than that of GF stage. By the late rice maturity stage, the contribution of photosynthetic carbon at early rice PD stage to DOC was up to 9.4%, being significantly higher than that of GF stage (2.6%). The contribution of photosynthetic carbon at early rice PD stage to total soil organiccarbon was significantly higher than that of GF stage at both harvests, which was 20.7 fold of that of GF stage by late rice maturity. In conclusion, compared with the early rice GF stage, the early rice PD stage can result in more photosynthetic carbon accumulation in soils, with higher contribution to soil organic carbon pool under double rice cropping system.

Growth characteristics of statolith of Sthenoteuthis oualaniensisin the Northwest Indian Ocean in spring and winter in the El Nino year.

LU Hua-jie, WANG Hong-hao, LIU Kai, CHEN Xuan-yu, HE Jing-ru, CHEN Xin-jun

2020, 39(11): 3694-3703. doi:10.13292/j.1000-4890.202011.036

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Statolith is one of the most important hard tissues in Cephalopods. It is an important material for studying age, growth, population structure, and life history of Cephalopods. The morphological growth characteristics of statolith in Sthenoteuthis oualaniensis were examined based on samples collected in the Northwest Indian Ocean from February to May of 2019 (the period of El Nino occurrence) by the Chinese light falling-net fishery fleets. The results showed that wing dome of the statolith was large, while dorsal dome and rostrum were relatively small. The results of principal component analysis showed that total statolith length (TSL), wing length (WL), lateral dome length (LDL) and maximum width (MW) could be used as morphological indicators for the morphological growth of statolith. The analysis of covariance (ANCOVA) showed significant sex differences in the relationships between these morphological characteristic parameters versus mantle length (ML) and body weight (BW). Based on the results of the Akaike’s information criterion (AIC), logarithm function best described the relationships between ML and TSL or WL, while linear function for the relationships between ML and LDL or MW for males. The relationships between ML and TSL, LDL or MW were best described by logarithm functions for females. The relationships between BW and TSL or WL were best described by logarithm functions but power function for LDL, MW for males. The relationships between BW and TSL, WL, LDL, MW were best described by logarithm functions for females. The absolute growth rate of statolith increased while the relative growth rate decreased with individual growth. Our results provide scientific basis for understanding population structure and life cycle of Sthenoteuthis oualaniensis and the effects of extreme weather on growth characteristics of hard tissues of Cephalopods.

Spatiotemporal variation and impacts of high temperature heat damage on river crab in Jiangsu Province. #br#

2020, 39(11): 3704-3714. doi:10.13292/j.1000-4890.202011.027

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River crab industry is one of the most prominent special aquatic industries in Jiangsu Province. It is extremely important to effectively avoid the main meteorological disasters in crab production and breeding. In this study, based on meteorological data, as well as observations and yield data of river crabs, at the daily scale, we determined the key meteorological factors influencing the growth of river crabs during the process of high-temperature heat damage. The daily high-temperature heat damage index of river crabs was constructed by applying membership model. At the annual scale, the synthesis index of high-temperature heat damage of river crabs was constructed. Furthermore, the relationships between high temperature heat damage index and yield loss of river crab were analyzed, and the high temperature heat damage was divided into five grades following the damage degrees. The interdecadal characteristics of hightemperature heat damage were analyzed. On this basis, the occurrence features of typical high temperature heat damage and yield reduction rates of river crab in 2018 were evaluated quantitatively. The results showed both temporal and spatial variations in the occurrence frequency and intensity of different grades of heat injury for river crab during the period from 1981 to 2018. In terms of the synthesis index, the occurrence frequency of moderate and above heat hazards showed a spatial distribution pattern of “more in the south and less in the north”, appearing an upward trend over time, with the largest increase during the period from 2001 to 2010. The spatial distribution of heat damage intensity showed a feature of “heavy in the south and light in the north”, with an aggravated trend over time. The high-value area was significantly extended from sporadic distribution in southern Jiangsu to the southern Huaihe River basin during 2011 to 2018. According to the daily index, the intensity of different levels of heat damage had little change at the inter-decadal time scale, while the frequency of occurrence had an upward trend with time, having a backward trend of its peak. Generally, indices of high temperature heat damage at different time scales could better reflect the impacts of disaster on the production processes and yields of river crabs from two aspects.

Effects of cadmium on antioxidant properties of Schizothorax prenanti

SHI Yan-ping, LI Yan-hong, LIAO Mao-wen, ZHANG Fei-fei, HUANG Li-juan, WU Ying-long

2020, 39(11): 3715-3721. doi:10.13292/j.1000-4890.202011.032

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The aim of this study was to examine the effect of cadmium on antioxidant properties in Schizothorax prenanti. Fishes were randomly divided into four groups, including control (0 mg·L^-1 Cd), low Cd concentration group (0.05 mg·L^-1), medium Cd concentration group (0.1 mg·L^-1), and high Cd concentration group (0.25 mg·L^-1). All groups were exposed for 14 days to measure antioxidant indices and biochemical indices of liver and serum. The results showed that the content of malondialdehyde (MDA) in the liver of S. prenanti was significantly increased (P<0.05) in all tested groups than those in the control, but the activity of alkaline phosphatase (ALP) was decreased (P<0.05). The liver superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activities and glutathione (GSH), triglyceride (TG) levels ofS. prenant were significantly decreased (P<0.05) at the low concentration of Cd compared with the control. The activities of liver aspartate aminotransferase (AST), alanine aminotransferase (ALT), acid phosphatase (ACP), superoxide dismutase (SOD) and the levels of triglyceride (TG), total cholesterol (TC), nitric oxide (NO) in S. prenanti were significantly increased (P<0.05) in the medium concentration of Cd than those in the control, whereas glutathione peroxidase (GSH-Px) activity was significantly decreased (P<0.05). The liver alanine aminotransferase (ALT), acid phosphatase (ACP) activities and nitric oxide (NO), total cholesterol (TC) levels were significantly increased (P<0.05) at high concentration of Cd than those in the control, but superoxide dismutase (SOD), aspartate aminotransferase (AST) activities and glutathione (GSH) level inS. prenanti were significantly decreased (P<0.05). Compared with the control, the serum malondialdehyde (MDA) level and nitric oxide (NO) level in S. prenant increased (P<0.05) in all test groups, the level of glutathione (GSH) was significantly decreased (P<0.05), the serum glutathione peroxidase (GSH-Px) activity ofS. prenanti was significantly decreased (P<0.05) at the medium and high concentrations of Cd. The serum superoxide dismutase (SOD) activity inS. prenantiwas significantly increased (P<0.05) at low concentration and decreased at high concentration of Cd. These results indicate that cadmium concentrations invoke a stress response in S. prenanti, which has caused the change of antioxidant indices and biochemical indices in liver and serum.

Identification and protection measures for the distribution hotspots of protected wildlife in Shenzhen.

DONG Xiao-yu, HUANG Tao, PAN Xue-lian, SUN Fang-fang

2020, 39(11): 3722-3737. doi:10.13292/j.1000-4890.202011.003

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Urban biodiversity has been seriously threatened by rapid urbanization. Distribution hotspots of important species in cities should be identified firstly to effectively protect urban biodiversity. We explored the degradation mechanism of urban protected wildlife in Shenzhen, a densely populated megacity. We used maximum entropy model (MaxEnt) to identify the distribution hotspots of protected wildlife, and analyzed the relationships between wildlife distribution and environmental factors by Jackknife test and response curves created by single corresponding variables. The distribution hotspots were overlaid with the protected area using ArcGIS to analyze the effectiveness of current biodiversity conservation measures. Based on all the analyses, we put forward the protection measures of urban protected wildlife. The results showed that the distribution hotspots accounted for 12.43% of total land area, mainly on the hilltop far from the built-up area, coincided with the native habitats of different wildlife, and being strongly overlapped with protected area. The results of Jackknife test showed that the dominant factors affecting wildlife distribution are land cover type, distance to city, vegetation type, maximum temperature of the warmest month, and diurnal difference of mean temperature. We suggest that urban biodiversity could be protected by maintaining the habitats of wildlife hotspots, restoring the habitats of potential distribution area, and constructing multi-level ecological space management system.

Distribution patterns and its environmental associations of beetle species diversity in Ningxia in Northwest China.

WANG Yuan, SHI Xiang-feng, YANG Gui-jun, JIA Long

2020, 39(11): 3738-3747. doi:10.13292/j.1000-4890.202011.013

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Based on the distribution information of beetles and the data of climate and habitat in Ningxia, we explored the relationship between the distribution patterns of beetle species diversity and environmental factors. The results showed that species richness and fauna differentiation intensity of beetles were higher in southern and northern areas than in central area, and higher in western area than in eastern area. Results of clustering analysis showed that the geographic distribution of beetles in Ningxia could be classified into four groups (Liupan Mountain beetle group, loess plateau beetle group, desert oasis beetle group, and HelanLuoshan Mountain beetle group). Results of GAM analysis showed that mean temperature in the coldest season, mean precipitation of wettest month, and plant species richness were the dominant factors affecting beetle distribution. Variance decomposition results showed that water, energy and habitat heterogeneity together explained 82.4% of the total variations of beetle species richness. Energy and water factors together explained 79.6% of the spatial variation in beetle species richness, with independent explanations of 19.9% and 14.0%, respectively. Habitat heterogeneity explained 26.3% of the spatial variation, with only 2.8% independently. Our results indicate that beetle species richness patterns are predominantly shaped by energy and water factors together, and that habitat heterogeneity helps enhance beetle species richness in Ningxia.

Coupling effects of nitrogen and salinity in seawater on biomass, carbon and nitrogen contents of Ulva pertusa.

YE Jia-hui, ZHANG Lu-lu, HAN Qiu-ying, SHI Yun-feng, ZHAO Mu-qiu

2020, 39(11): 3748-3755. doi:10.13292/j.1000-4890.202011.035

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Global climate change and human activities affect nitrogen nutrient and salinity in coastal waters. Ulva pertusa, a dominant species in the coastal waters of temperate zones, will grow faster under eutrophication conditions, with negative impacts on marine ecosystems. In this study, the coupling effects of nitrogen content and salinity of seawater on U. pertusa were examined in laboratory experiments. The results showed that nitrogen and salinity had significant synergistic effects on the biomass of U. pertusa. Under high salinity (40) condition, U. pertusa showed high biomass, whereas nitrogen enhancement led to lower biomass. C, N concentrations and C/N ratio in U. pertusa tissues did not correlate with seawater N concentration, but correlated with seawater salinity. Our results provide a basis for the mechanism and scientific management of macroalgae blooms in eutrophication water under the background of global climate change.

Community structure of planktonic bacteria and its driving factors along the upstream area of Qingjiang River in Lichuan City, Hubei Province.

LI Ya-li, YANG Zheng-jian, XU You, MA Jun, TIAN Pan

2020, 39(11): 3756-3765. doi:10.13292/j.1000-4890.202011.031

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To clarify the community structure and spatial distribution of planktonic bacteria in natural river without the influence of dam, five sampling sites were monitored along the upstream of Qingjiang River in Lichuan City, Hubei Province. The results showed that 35 phyla of planktonic bacteria were recorded in the research area, with Proteobacteria being the dominant phylum. At genus level, there were 447 genera, with Ainetobacterbeing the dominant genus in the headwater of Qingjiang (Site 1) and Limnohabitanbeing dominant in the other sites. ACE index, Shannon index, and specific OTU in Site 1 were much higher than those in other sites, indicating that planktonic bacterial diversity and abundance were the highest in the upstream. Total phosphorus, dissolved oxygen and water temperature were the main factors affecting planktonic bacterial community structure. The abundance of Proteobacteria was significantly positively correlated with total phosphorus and water temperature, but negatively with dissolved oxygen. Bacteroidetes and Verrucomicrobia were significantly positively correlated with dissolved oxygen. At the genus level, water temperature was the main factor driving the spatial distribution of dominant bacterial genera.

Prediction of the ecological suitability of Gentiana macrophylla Pall. under scenarios of global climate change.

TAN Yi-hong, ZHANG Xi-juan, YUAN Shu-sheng, YU Jing-hua

2020, 39(11): 3766-3773. doi:10.13292/j.1000-4890.202011.023

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Following three representative concentration pathways (RCP2.6, RCP4.5 and RCP8.5) under 2050s and 2070s, geographic information technology (GIS) and maximum entropy model (MaxEnt) were used to simulate the ecological suitability of Gentiana macrophyllaPall., a third-grade rare and endangered medicinal plant species, under current and future scenarios of global climate. The results showed that the main environmental factors affecting the distribution of G. macrophylla were annual precipitation, precipitation in the driest month, altitude, and the lowest temperature in the coldest month, which are related to the growth characteristics of G. macrophyllaincluding moisture-tolerance, cold-tolerance, and waterloggingintolerance. Current suitable area was 143×10⁴ km². Under the future climate change characterized by increasing RCP concentration, the area of suitable area will be reduced to 17.3%-41.5% of the current area. The ecological suitability level significantly changed. Its distribution center shifted from northwest China (including Shanxi and Gansu Province) to the northeastern China (such as the Greater Khingan Mountains and Hulunbuir city). Due to the drying climate in the future, some of the original suitable areas are not suitable for G. macrophylla. Based on those findings, we proposed that (1) Use in-situ conservation strategies to establish natural reserves or botanical parks within the current suitable areas, or carry out in situ plantation; (2) Adopt the idea of ex-situ conservation to breeding, and put the G. macrophylla genes into the database. Meanwhile, G. macrophylla planting industry needs to be widely developed in the current centers of suitable areas and the future suitable area.

Prediction of potential distribution area of Corylus mandshurica in China under climate change. #br#

WANG Qi, FAN Bao-guo, ZHAO Guang-hua

2020, 39(11): 3774-3784. doi:10.13292/j.1000-4890.202011.014

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Climate change influences plant geographic distribution. Studies on the influence of climate change on species geographic distribution is of great significance for protection and proper utilization of species. In this study, we adjusted multi-feature combination and magnification parameters through ENMeval packet to optimize MaxEnt model. With 221 effective distribution data of Corylus mandshurica and 16 environmental factors, we simulated and predicted its potential distribution areas under current and future climate (2050s and 2070s), and analyzed dominant environmental factors affecting its geographic distribution. The results showed that when feature combination was LQPH and regularization multiplier was 1.5, both the complexity and overfitting of the model were low and prediction accuracy was good. Under the present climate scenario, suitable distribution zones of C. mandshurica were located in Changbai Mountain, Taihang Mountain, Qin-ba Mountainous Area, and south of Gansu Province. Under future climate scenario, the suitable zones ofC. mandshurica, such as central and northern Shaanxi, southwest China and southern Gansu, will progressively decline, whereas more suitable zones will move to eastern Inner Mongolia and Heilongjiang. The center of suitable zones tended to move towards northeast. Dominant environmental factors affecting the geographic distribution of C. mandshurica wereannual precipitation, mean temperature of driest quarter, elevation and annual mean temperature, with a cumulative contribution rate of 78.8%, and their suitable condition ranges were 430-970 mm, -21 to 3 ℃, 40-2800 m and 0.8-13 ℃, respectively.

Potential suitable habitat of mangroves and conservation gap analysis in Guangdong Province with MaxEnt Modeling.

CHAO Bi-xiao, HU Wen-jia, CHEN Bin, ZHANG Dian, CHEN Guang-cheng, YU Wei-wei, MA Zhi-yuan, LEI Guang-chun, WANG Yu-yu

2020, 39(11): 3785-3794. doi:10.13292/j.1000-4890.202011.009

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Mangrove forest is a woody community occurring in the intertidal zone of tropical and subtropical coasts, with important ecological functions. Guangdong Province has the largest area of mangrove in China, and thus is critical for mangrove protection. Maximum entropy model (MaxEnt), a species distribution model, is extensively applied in biodiversity conservation. This study compiled a dataset of mangrove distribution and key environmental variables in Guangdong Province. With this dataset, a mangrove MaxEnt was built, which was used to predict the potential suitable zones of mangroves in Guangdong Province and to identify the key environmental variables influencing mangrove distribution. Outcomes of the modeling were further used to assess conservation gaps. The results showed that the most important environmental variables affecting mangrove distribution were temperature, sea surface temperature, and precipitation. The suitable range for annual mean temperature was 22.37-23.58 ℃, for mean sea surface temperature of the coldest quarter was 23.15-23.34 ℃, for annual precipitation was 1647.14-1809.61 mm, and for precipitation of driest month was 23.6-27.2 mm. The most suitable areas for mangrove in Guangdong were mainly concentrated in Pearl River Estuary to Daya Bay coast, and Leizhou Peninsula to Yangjiang coast. Conservation gaps of mangrove were mainly located in Yangjiang Port, Zhenhai Bay, Pearl River Estuary, and Red Bay. Our findings could provide a scientific basis for improving and advancing the spatial layout of mangrove protection and restoration in Guangdong Province.

Landscape connectivity of urban parks in the downtown of Chengdu.

LUO Yan-yun, LI Chun-rong, XIE Yu-song, WANG Qian-na

2020, 39(11): 3795-3807. doi:10.13292/j.1000-4890.202011.022

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As an important component of urban green space system and space carrier of park city construction, urban parks play an important role in ecological and social benefits in high-density downtown. However, as one of the core indicators for ecosystem function and ecological pattern, landscape connectivity is rarely examined in urban parks. Using remote sensing image data of 2015, based on the Morphological Spatial Pattern Analysis (MSPA) and landscape connectivity index analysis, we evaluated the structural connectivity and functional connectivity of 32 main urban parks in the downtown of Chengdu. The aim of this study was to further optimize the overall ecological pattern of the city, improve the urban living environment, and promote the park city construction in Chengdu. The results showed that the overall landscape matrix of the urban parks behaved well. The top three mean proportions of network structure elements were the large core (48.15%), the edge (23.36%), and the bridge (10.83%). The parks were diverse in composition characteristics. Compared with corridors, urban parks had obvious advantages in patch elements. The classification results of dIIC value showed significant spatial distribution differences in the importance of landscape connectivity among urban parks. Urban parks were dependent on each other with respect to structural connectivity and functional connectivity. It is recommended to strengthen the protection of important patches and parks between the 3rd ring road and the 4th ring road, pay attention to the transition and connection of large, medium and small cores inurban parks, and improve landscape connectivity of urban parks in combination with relevant strategies and actions.

Distribution characteristics of soil iron in estuary wetland under fossil oil pollution.

YAN Guo-hui, ZHU Bin, ZHAO Wen-bin, CHI Guang-yu, CHEN Xin

2020, 39(11): 3808-3816. doi:10.13292/j.1000-4890.202011.002

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The distribution and transformation of iron in estuarine soil plays an important role in wetland nutrient cycling and organic pollutant degradation. To explore the distribution characteristics of iron in estuarine soil under fossil oil pollution can provide a reference for understanding the distribution of petroleum hydrocarbons and iron transport and transformation in estuarine wetlands. Soil samples were collected from natural wetlands of Liaohe River estuary and wetlands around fossil oil wells with different exploitation years, and then were measured for total petroleum hydrocarbon (TPH), total organic matter (TOC), Eh, pH, total iron (Fe_t), acid soluble Fe²⁺, Fe³⁺, free iron oxide (Fe_d) and amorphous iron (Fe_o). The results showed that: (1) The petroleum hydrocarbon content of the surface soil layer around the oil well with an exploitation age of 10 years was significantly higher than that of the other layer soils. More petroleum hydrocarbon was accumulated in the 20-30 cm soil layer around oil wells with an exploitation age of more than 10 years, and oil pollution facilitated the increase of total organic matter content and pH in soil. (2) There were positive correlations between petroleum hydrocarbon and soil organic matter (P<0.01), and between soil organic matter and soil Fe²⁺ (P<0.05). (3) In natural wetland, soil Fe²⁺ content increased with soil depth, while in oil-contaminated soil, the Fe²⁺ content of upper soil layer (0-30 cm) was relatively higher, and soil oxidation gradually decreased with increasing soil depth. The distribution of soil Fe_d was affected by Fe_t. The invasion of petroleum hydrocarbon enhanced Fe_d production. There was no significant difference in the distribution of Fe_o in soil with different mining years.

Mercury release flux and its influencing factors from urban tidal flat of young Kandelia candel plantation.

YE Yu-ting, SUN Lu-min, ZHOU Liang, LU Chang-yi, YAO Yi, CHEN Wei-jia

2020, 39(11): 3817-3828. doi:10.13292/j.1000-4890.202011.006

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Coastal tidal flat is an important ecological resource of coastal cities, the protection and restoration of which are important for its ecological function. In this study, we measured the mercury release flux of forest land and forest edge bare flat with an improved dynamic flux box system and Tekran 2537B mercury analyzer in the restored Kandelia candel plantation in Haicang Bay, Fujian Province, during the daily low and flat tide period in summer and winter from 2018 to 2019. The results showed that the concentrations of atmospheric mercury and surface sediment mercury in the plots were at low levels. The tidal flat/atmospheric mercury flux was generally positive. The release of mercury in the daytime was more obvious than that at night. The release intensity in summer was greater than that in winter. Compared with the bare flat, forest land showed a significant inhibitory effect on mercury release from tidal flat to the atmosphere. Temperature, light, wind speed, topsoil temperature, and atmospheric mercury concentration were positively correlated with mercury flux. The influencing factors of mercury flux could be classified into two categories: atmospheric factor and ground surface factor. The mercury flux prediction models of forest land and bare flat were obtained by regression analysis. By comparing the regression coefficients of both models, it was found that the impact capacity of atmospheric factor on mercury flux was significantly inhibited by forest. Our results confirmed the inhibition ability and control factors of mangrove to mercury release from the tidal flat to the atmosphere, and provide a scientific basis for assessing the ecological value of mangrove replanting on bare flat in coastal zone in terms of mercury storage.

Research on soil organic matter in forest ecosystems: Status and challenge.

WANG Qing-kui, TIAN Peng, SUN Zhao-lin, ZHAO Xue-chao

2020, 39(11): 3829-3843. doi:10.13292/j.1000-4890.202011.033

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Soil organic matter (SOM), an important organic component in soils, plays a key role in maintaining soil fertility, food security and global change. Globally, soil scientists have made longterm and great efforts to improve our understanding of SOM cycling, particularly its formation and decomposition. There are much difficulty and challenge in the global environmental change context. Here, we reviewed the research advances in soil microbial residues, influence of plant litters on SOM cycling, priming effect and temperature sensitivity of SOM decomposition, deep SOM and responses of SOM cycling to environmental change in forest ecosystems. First, in laboratory and field-based long-term experiments, the simulated experiment conditions were different from the natural conditions, which may lead to deviation in the observations or results.Second, soil microbes, as the key driver of SOM cycling, control both SOM formation and decomposition. The microbial process and SOM cycling should be linked in further research, to ascertain the roles of microbes in SOM cycling. Third, multifactorial impacts of global environmental change on SOM should be addressed with an efficient, broadly applicable experimental design due to the coupling effects of multiple factors. Finally, the coupled linkages between above andbelow ground ecological processes from an ecosystem perspective should be strengthened by adopting the theories of multiple disciplines and advanced analytical techniques. Overall, this review would help improve our understanding of SOM cycling in terrestrial ecosystems, especially in forest ecosystems, and also has implications for researchers in grassland, agricultural and wetland ecosystems.

The influence of rubber-based agroforestry system on regulating resource use and ecological services. #br#

QI Dong-ling, YANG Xiao-bo, XIE Gui-shui, WU Zhi-xiang

2020, 39(11): 3844-3852. doi:10.13292/j.1000-4890.202011.030

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Plantation forest is an important part of forest ecosystems, which plays an important role in global forest resources. Plantation forests have positive contributions to the supply of material products, the service and improvement of ecological environment, the construction of ecological landscape and response to global changes. In this study, we analyzed the function and stability of plantation forest, and the function and mechanism of rubberbased agroforestry system in the regulation and utilization of resources, including light, heat, water, nutrient, land, and space. We examined the influence of rubber-based agroforestry system on ecological services, including water conservation and the enhancement of system stability, micrometeorological environment, soil quality, and biodiversity. After that, we proposed that future research should focus on the formation mechanism and regulation of productivity of rubber-based agroforestry system, the maintenance mechanism of rubber agroforestry system, the multifunctional service and regulation of rubber agroforestry system, and the response of rubber agroforestry system to global climate change.

Phenotypic plasticity and the successful invasion of alien plants.

XIONG Yun-qi, ZHAO Cai-yun

2020, 39(11): 3853-2864. doi:10.13292/j.1000-4890.202011.019

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Biological invasion is the second major driver for biodiversity loss. Understanding the invasion mechanism can improve our ability to control invasive species. Phenotypic plasticity, which has a genetic basis, is considered as one of the most important mechanisms for the successful invasion of alien plants. In the past 30 years, the research on phenotypic plasticity has been surging. To explore the phenotypic plasticity mechanism of successful invasion of alien plants, the combinations of field investigations and transplantation experiments, crossdisciplinary research of macroecology and molecular ecology have been used. We reviewed the phenotypic plasticity of alien plant invasion from the concept, the research and development of phenotypic plasticity and its ecological significance in plant invasion. Perspectives in future researches of phenotypic plasticity of invasive plants were also proposed. The ecological role of phenotypic plasticity is a hotspot in current research. Phenotypic plasticity, along with genetic differentiation, is an important strategy for alien species to adapt to new environment, which enhances adaptability and intrusion capability. In the future, comprehensive multidisciplinary research is the trend for studies on phenotypic plasticity. The research of the invasion mechanism of alien plants is expected to combine environmental factors, such as climate change and land use, with phenotypic plasticity, applications of the methods of genomics and molecular biology, and quantitative analysis and comparison of phenotypic plasticity across individuals, populations, and species.

Decomposition of wetland plant residue and its influencing factors: A review.

XU Ce, ZHAO Wei, YU Xiu-bo

2020, 39(11): 3865-3872. doi:10.13292/j.1000-4890.202011.008

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The decomposition of plant residue plays a pivotal role in material cycling in wetland ecosystems, which is regulated by a range of biotic and abiotic factors. Here, we reviewed therecent researches on the decomposition of wetland plant residue and the biotic and abiotic factors influencing the processes, especially related studies on the effects of water level. The effects of water level on wetland plant residue decomposition cannot be neglected, as it is one of the key natural driving factors in wetland ecosystems with substantial fluctuation of water level. Furthermore, suggestions and research prospect concerning photodegradation of plant residues, quantification of the contribution of key factors as well as direct and indirect influences of these factors on residue decomposition are proposed.

Impacts of alternate wetting and drying irrigation on rice production and the mitigation of greenhouse gas emission in paddy fields.

ZHANG Xian-xian, ZHOU Sheng, SUN Hui-feng, ZHANG Ji-ning, WANG Cong

2020, 39(11): 3873-3880. doi:10.13292/j.1000-4890.202011.001

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Rice production consumes large amount of water resource and is an important greenhouse gas (GHG) source. Water management in paddy fields is the key factor controlling GHGemission. As an important agricultural practice for water saving and GHG emissions reduction, alternate wetting and drying (AWD) irrigation has been commonly applied in many Asian countries, such as China, Philippines, Vietnam, and India. We analyzed the effects of AWD irrigation on GHG emissions mitigation and other ecological efficiency, including water saving potential and rice yields. AWD significantly decreased methane (CH₄) emission and increased nitrous oxide (N₂O) emission. The global warming potential (GWP) mitigation was dependent on the increases of N₂O emission. Coupling with fertilizer management, such as optimizing the fertilizer type and application method, AWD is conducive to the CH₄ and N₂O mitigation. Rice yield was affected by the water stress threshold of AWD. Mild water stress (field was re-flooded when soil water potential dropped to -15±5 kPa) could reduce irrigation water inputs and maintain rice yield, while severe water stress (field was re-flooded when soil water potential dropped to -30±5 kPa) significantly reduced yield. AWD improved soil aeration and microbial activities, with positive impacts on decomposition of soil organic matter. Encouraging farmers to develop watersaving and efficient agriculture scientifically would be beneficial to cost reduction and income increase.

Multisource land-cover data category accuracy evaluation and the difference of landscape patterns: A case study of Beijing-Tianjin-Hebei region.

SHAO Ming-chao, SONG Hong-li, SHANG Ming, HE Hong-tao, SHI Yi-meng

2020, 39(11): 3881-3889. doi:10.13292/j.1000-4890.202011.020

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Remote sensing data of land cover is the basic information for largescale landscape pattern research. Land-cover data from different research teams adopt different data sources and classification methods, which leads to inconsistent results of landscape pattern research. Quantitative analysis of the consistency of land-cover data and its impacts on landscape pattern research is of great significance. Here, with two sets of global scale 30m resolution landcover remote sensing data GlobeLand30 and FROM-GLC as the research objects, we compared their differences in soil and water conservation areas in Beijing-Tianji-Hebei Region from two aspects of landcover type and landscape pattern index. The results showed that: (1) In the mountainous and hilly water conservation and soil conservation region in the eastern part of Taihang Mountains, theagreement in area size between the two datasets was the highest, with a consistency value of 96.8%. By contrast, the consistency was the lowest in the mountainous and hilly sand control and water conservation region in the northwestern Taihang Mountains, with a value of 3.6%; (2) The spatial consistency of those two datasets in the Jin-Yi-Lu Bohai Bay ecological maintenance area was the highest, with a spatial consistency value of 73.6%. In the mountainous and hilly area of the northwestern Taihang Mountains, the spatial consistency of sand control and water conservation area was the lowest, with a value of 25.17%; (3) In terms of landscape pattern, the complexity of GlobeLand30 dataset in the six ecological functional areas of BeijingTianjinHebei was lower than that of the FROM-GLC dataset, indicating that diversity of landscape in GlobeLand30 dataset was lower, and homogeneity of surface landscape categories was stronger, while surface landscape heterogeneity and fragmentation degree of FROM-GLC dataset were stronger.

Effects of tillage and cropping modes on soil properties in oasis irrigation area.

HE Ru, ZHANG Shuang-yu, YANG Cai-hong, WANG Li

2020, 39(11): 3890-3902. doi:10.13292/j.1000-4890.202011.015

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A field experiment was conducted to investigate the effects of tillage methods and crop rotation models on soil enzyme activities and physicochemical properties during different growth periods in an oasis irrigation region of Northwest China. There were three crop rotation models, including wheat/maize intercropping (W//M), wheat and maize rotation (WM), and wheat after planting winter rape in rotation with maize (WGM), with two tillage methods (30cm stubble and no tillage, NT; conventional tillage, CT) being applied for each rotation model. Results showed that the activities of soil sucrase and amylase increased first and then decreased under different treatments, while the activities of urease and protease gradually increased. Soil enzyme activity of NTW was increased by 13.00%, 7.50% and 30.61% than that of NTM, NTW-G-M and NTSM, respectively. Soil total nitrogen and phosphorus concentrations were 59.52%-87.14% and 20.00%-66.67% lower at maize maturity than at wheat sowing, respectively. Soil bulk density was the lowest at wheat sowing, being 3.47%-11.03% lower than that at maizematurity stage. Soil porosity was negatively correlated to soil bulk density. There was no significant difference (P>0.05) in maize yield among different treatments. NTW//M treatment had the best performance in soil structure and nutrient status. Therefore, wheat/maize intercropping with no-tillage straw returning should be a useful method for maintaining land productivity, which is worth popularizing in oasis agricultural area.

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