Table of Content

15 June 2022, Volume 33 Issue 6

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Special Features of Stable Isotope Ecology

Theory, method and application advance of isotopic flux partitioning of ecosystem photosynthesis and respiration

CHEN Chang-hua, WANG Jing-yuan, WEI Jie, WEN Xue-fa

2022, 33(6):  1441-1450.  doi:10.13287/j.1001-9332.202206.007

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Photosynthesis and respiration are two important components of net ecosystem exchange (NEE). NEE can be directly observed by eddy covariance (EC) technique, and statistically separated into ecosystem assimilation and respiration based on the statistical flux partitioning of temperature response function or light-response curves. However, these methods would result in auto-correlation between assimilation and respiration, and overestimate daytime respiration. Recently-developed isotope ratio infrared spectroscopy permits high-resolution measurement of atmospheric CO₂ and its stable carbon isotope composition (δ¹³C) under field conditions, and achieves diurnal and seasonal partitioning of ecosystem photosynthesis and respiration by matching with NEE measurements from EC. We expounded the fundamental theories and assumptions of isotopic flux partitioning of ecosystem photosynthesis and respiration, elaborated the development and application advance of techniques in isotopic flux measurement, summarized the advance of isotopic flux partitioning to provide new insight into the assimilation and respiration processes, and prospected the uncertainty of isotopic flux partitioning theory and the necessity of comparative researches of various methods.

Characterization of greenhouse gas emissions and stable isotopic composition of ammonia during industrial composting process

LIU Dong, SUN Jian-ping, WANG Ying-ying, SONG Lin-lin, LI Jin, ZHAO Xing-han, LIU Chang, QUAN Zhi, FANG Yun-ting

2022, 33(6):  1451-1458.  doi:10.13287/j.1001-9332.202206.009

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Carbon dioxide (CO₂), nitrous oxide (N₂O), methane (CH₄) and ammonia (NH₃) emitted during the composting of livestock and poultry waste are important gaseous atmospheric pollutants. However, most previous studies on compost-related anthropogenic emissions of these gases were based on small reactor composting. Our understanding of their in situ emissions during industrial composting remains extremely limited. In order to explore the influence of gas produced by industrial composting on regional environment, we monitored CO₂, CH₄, N₂O and NH₃ emissions during industrial composting for 19 days and characterized the isotopic composition of emitted NH₃. On average, the emission rates of CO₂, CH₄, N₂O, and NH₃ during the composting cycle were 86.8 g CO₂-C·d^-1·m^-2, 9.8 g CH₄-C·d^-1·m^-2, 3.7 mg N₂O-N·d^-1·m^-2 and 736.6 mg NH₃-N·d^-1·m^-2, respectively. The contribution of CH₄ to daily global warming potential (GWP) was the highest (65%), followed by CO₂, NH₃(indirect), and N₂O. Moreover, ammonia emitted from industrial compost had a mean δ¹⁵N value of -11.6‰±1.2‰ (range: -21.8‰--7.2‰). Overall, this study provided useful information for understanding greenhouse gas emission dynamics and characterizing atmospheric NH₃ sources during composting process in livestock and poultry breeding areas.

Isotopic characteristics and vapor sources of atmospheric precipitation in the loess region of North Shaanxi, China

LI Jia-qi, HUANG Ya-nan, SHI Pei-jun, LI Zhi

2022, 33(6):  1459-1465.  doi:10.13287/j.1001-9332.202206.011

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To explore the hydrogen and oxygen stable isotopes and vapor sources of atmospheric precipitation in the loess region of north Shaanxi, we collected 107 samples of precipitation during 2018 to 2020 in the Dingbian County, Shaanxi Province. After measuring δ¹⁸O and δ²H of precipitation, we analyzed the isotopic characteristics and vapor sources of precipitation in different seasons. There was obvious seasonal variability in δ¹⁸O and δ²H, in that they were more depleted in the wet season (June-September) but more enriched in the dry season (April-May, October-November). In addition, the deuterium excess values were high in the dry season but low in the wet season. The local meteoric water line was regressed as δ²H=7.35δ¹⁸O+4.19 (R²=0.96, P<0.01) with slope and intercept lower than that of the global meteoric water line, indicating an impact of evaporation on isotope fractionation. There was temperature effect in the precipitation isotopes for the whole year and for the dry season, while the precipitation isotopes in the wet season were affected by the combined effects of temperature and rainfall amount. The HYSPLIT model showed that the dry season water vapor mainly came from the Atlantic Ocean and the polar Arctic Ocean, while the wet season vapor mainly came from the Indian Ocean and Pacific subject to the Westerly.

Variations of δ¹³C in water-soluble compounds during spring phenology of typical tree species in the warm temperate zone

ZHAO Xu, LU Shao-wei, LI Shao-ning, XU Xiao-tian, ZHAO Na

2022, 33(6):  1466-1474.  doi:10.13287/j.1001-9332.202206.012

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In this study, we examined the regularity of phenological rhythmical change of plant water-soluble compound δ¹³C (δ¹³C_wsc) in spring for two typical tree species in the warm temperate zone of China, Pinus tabuliformis and Robinia pseudoacacia. The δ¹³C_wsc in each organ of those two species in the spring phenological period were measured to explore the relationship between δ¹³C_wsc and related environmental factors. The results showed that there were significant differences in δ¹³C_wsc values of each organ between P. tabuliformis and R. pseudoacacia, with higher δ¹³C_wsc(-25.03‰±0.01‰) in the new shoot of P. tabuliformis. The δ¹³C_wsc value in the non-photosynthetic organs were 0.83‰-1.8‰ higher than that in the photosynthetic organs, while the δ¹³C_wsc value in the aboveground part was generally lower than that in the underground part. As spring progressing, different carbon storage strategies were found between two species. When the terminal bud of P. tabuliformis opened, the carbon was obtained from the proximal old leaves. At the beginning of leaf development, photosynthetic products accumulated by old leaves could not meet the growth requirements for new leaves and roots, with 90% of which depending on the carbon reserve in branches and stems. When full leaf having developed, the photosynthetic function of both new and old leaves recovered and the carbon consumed by branches and stems was gradually replenished. For R. pseudoacacia, at the beginning of leaf bud opening and leaf spreading, branches were the main carbon source for new leaves and roots. When leaves were fully unfolded, mature leaves with high capacity of carbon sequestration became the primary carbon source. Results of principal component analysis showed that temperature during observation period, ≥10 ℃ accumulated temperature, sunshine duration and solar radiation were the main factors influencing δ¹³C_wsc, which could explained 86.3% of the total variation. The δ¹³C_wsc values of both species was negatively correlated with temperature and relative humidity, but positively correlated with the difference of saturated water pressure, ≥10 ℃ accumulated temperature and sunshine duration. The main environmental factors affecting plant δ¹³C_wsc varied during the phenological process. Our results could provide a reference for more accurate estimation of spring organ carbon distribution pattern of regional typical tree species, and also a theoretical basis for formulating scientific and reasonable forest management strategy.

Distribution and sequestration of straw carbon in surface and deep soil aggregates under different fertilization treatments

DUAN Jia-ru, WANG Shu-ying, LI Xiao-hong, XU Xiang-ru, MEI Xiu-wen, AN Ting-ting, WANG Jing-kuan

2022, 33(6):  1475-1481.  doi:10.13287/j.1001-9332.202206.013

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Long-term fertilization causes the differences in water, heat, nutrients and microbial activities between topsoil and deep soil, with consequences on the decomposition and turnover of straw carbon (C) in soils. At a long-term positioning experimental station in Shenyang Agricultural University, we mixed the topsoil (0-20 cm) and deep soil (40-60 cm) samples from different fertilization treatments with ¹³C-labeled straw for in-situ incubation. We analyzed the content of organic C and its δ¹³C value in soil aggregates, compared the difference in the distribution of straw C between topsoil and deep soil aggregates, and explored the effects of fertilization on the sequestration of straw C in soil aggregates. Compared with fertilization treatments (i.e., single chemical nitrogen fertilizer application and combination of organic manure with nitrogen fertilizer application), the treatment without fertilization increased the content of straw C of <0.053 mm aggregate in the topsoil by 106.7% and that of >0.25 mm aggregate in the deep soil by 34.2%. The contribution percentage of straw C to organic C of >0.053 mm aggregate in the deep soil was about two times of that in the topsoil. About 22.6% and 11.4% of straw C was distributed into the >0.25 mm and <0.25 mm aggregates of topsoil, and about 29.4% and 8.8% of straw C was distributed into the >0.25 mm and <0.25 mm aggregates of deep soil, respectively. In conclusion, straw addition promoted the regeneration and sequestration of carbon in deep soil macroaggregates and increased the carbon sequestration potential of deep soil.

Application of Pu isotope tracing technique in soil erosion research

HAO Yong-pei, SONG Xiao-wei, XU Yi-hong

2022, 33(6):  1482-1488.  doi:10.13287/j.1001-9332.202206.008

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As an essential form of material migration on the surface of the earth, soil erosion is one of the primary causes of soil fertility reduction and environmental degradation. Quantifying soil erosion rate is the precondition and foundation for regional soil erosion control. The Pu isotopes produced by atmospheric nuclear tests have a long half-life after settling into the soil and could be easily adsorbed by clay minerals and organic matter. In recent years, Pu isotopes have become principal trace elements in the quantitative studies of soil erosion rate, especially with the development of mass spectrometry technique. The measurement time of Pu isotopes has been shortened, and the sensitivity of Pu isotopes has been improved, both of which help improve the radionuclide tracing technology for soil erosion. Here, we summarized the distribution characteristics as well as the adsorption and migration behavior of Pu isotopes in soil. We described the basic principles for the application of Pu isotopes in tracing soil erosion, and elaborated the research progress concerning relevant applications. Moreover, we compared the applicability of Pu isotope and ¹³⁷Cs tracing techniques in soil erosion research and proposed research directions in the future. This review would provide a reference for the scientific applications of Pu isotope tracing technique in soil erosion research.

Analysis of food sources of Eriocheir sinensis in rice-crab integrated ecosystem based on stable isotopes in saline-alkali land of the Yellow River Delta

MIAO Jing, LIU Feng, YAN Fa-jun, LI Xian, DONG Jun, ZHU Yong-an, WANG Xin-jun, DONG Xiao-liang

2022, 33(6):  1489-1496.  doi:10.13287/j.1001-9332.202206.010

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To explore food composition of Chinese mitten crab (Eriocheir sinensis) in rice-crab integrated ecosystem in saline-alkali land of the Yellow River Delta, we analyzed carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N) in the crab and that in food sources, including plants (Elodea, Potamogeton crispus, Ceratophyllum demersum, Lemna minor, Oryza sativa stem and leaf, rice grain), animals (benthos, zooplankton), organic debris and artificial feed (compound feed, corn meal) in Kenli District, Dongying, Shandong Province in June to October of 2020. Substantial differences in δ¹³C and δ¹⁵N were found among food sources. The δ¹³C and δ¹⁵N values of different food sources were in a range of -30.09‰--11.24‰ and 0.03‰-12.78‰, respectively, while those of the crab muscle were in range of -24.61‰--20.08‰ and 4.74‰-9.21‰, respectively, indicating diverse food sources for the crab. During the experiment, the contribution rate of different food sources followed the order: plant (46.7%-57.1%)>animal (21.5%-24.5%)>artificial feed (10.9%-21.3%)>organic detritus (7.1%-7.9%). It suggested that the natural bait of the paddy field could meet the feeding needs of Chinese mitten crabs in saline-alkali land. Even the crabs were fed with non-animal artificial feed, the contribution rates of the main food sources were not altered.

Original Articles

Changes of leaf functional traits of Pinus tabuliformis in burned areas with different fire severities

GU Ze, WANG Bo, CHEN Si-fan, WANG Yi-wen, SUO Ao-li, LIU Xiao-dong, CHEN Feng

2022, 33(6):  1497-1504.  doi:10.13287/j.1001-9332.202206.001

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The response of leaf functional traits to forest fire is one of the research hotspots in the forest fire ecology. Studying post-fire changes in leaf functional traits of Pinus tabuliformis can reveal its growth strategies to adapt to fire environment and provide reference for the post-fire recovery. We analyzed the changes of leaf functional traits in burned areas with different fire severities (unburned, light burn and moderate burn) in Qinyuan County burned area of Shanxi Province, and studied the variation characteristics of leaf economic spectrum in different burned areas. The results showed that there were significant differences in burned areas with different fire severities for all leaf functional traits except N/P. Among them, the difference of leaf area was the most obvious, which was the most sensitive trait. With the increases of fire severity in burned areas, leaf area, leaf thickness, leaf dry matter content, leaf nitrogen content and leaf phosphorus content increased, while specific leaf area and leaf organic carbon content decreased. There were significant correlations among some leaf functional traits, with the correlations being distinct in burned areas with different fire severities. The leaf economic spectrum moved from ‘unburned-light burn-mode-rate burn’ to the resource trade-off strategy of ‘rapid investment-return type’ along the fire environment. The recovery of P. tabuliformis would be accelerated in burned area with low fire severity.

Effects of CO₂ concentration and soil water content on short-term water-use efficiency at whole-plant level

ZHANG Yong-e, ZHAO Yang, LU Wei-wei, YU Xin-xiao, ZHANG Xiao-ming, WANG Zhao-yan, LIU Bing, XIN Yan

2022, 33(6):  1505-1510.  doi:10.13287/j.1001-9332.202206.002

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Uncovering the variations of short-term water-use efficiency (WUE_p) at whole-plant level in response to CO₂ concentration (C_a) and soil water content (SWC) can improve the understanding of plant survival strategies under climate change. In this study, Platycladus orientalis saplings were cultured in simulated climate chambers.There were totally 15 treatments, including C_a of 400 (C₄₀₀), 600 (C₆₀₀) and 800 (C₈₀₀) μmol·mol^-1 and SWC of 35%-45% field water holding capacity (FC), 50%-60%FC, 60%-70%FC, 70%-80%FC and 95%-100%FC. The WUE_p was measured by mini-lysimeters, weighting method, and static assimilation chamber. The results showed that both daytime (0.12-1.87 mol·h^-1) and nighttime transpiration rates (0.01-0.16 mol·h^-1) at whole-plant level reached the maximum at C₄₀₀×70%-80%FC, while the whole-plant daytime net photosynthetic rate (2.12-22.10 mmol·h^-1) reached the maximum at C₈₀₀×70%-80%FC. In contrast, nighttime respiration rate (0.84-4.41 mmol·h^-1) increased with increasing SWC, but decreased with increasing of C_a, reaching the maximum at C₄₀₀×95%-100%FC. For WUE_p (5.37-24.35 mmol·mol^-1), it reached the maximum at C₈₀₀×50%-60%FC, indicating that plants could use less water and fixed more carbon by adjusting adaptation strategies under high C_a and drought conditions. In addition, leaf instantaneous water-use efficiency was a good predictor of WUE_P when the canopy structure was similar.

Effects of tree species identity and diversity on young tree growth in a south subtropical plantation

HU Jia-jia, WANG Hui, LIU Shi-rong, WANG Jian, SONG Zhan-chao, LI Zhao-ying, MING An-gang, CHEN Hai

2022, 33(6):  1511-1517.  doi:10.13287/j.1001-9332.202206.003

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To select the tree species assembly model for improving the productivity in south subtropical plantations, we carried out an experiment following a random block design with eight native tree species across a richness gradient of 1, 2, 4, and 6 species. The effects of tree species diversity and species mixing with different functional identities on the young tree growth were investigated in the 5th year of the experiment. The results showed that tree growth was not positively correlated with tree species richness. The growth of fast-growing tree species (Pinus massoniana and Mytilaria laosensis) in the monoculture was 2.5-4.5 times of the valuable broadleaved tree species (Castanopsis hystrix and Erythrophleum fordii) monoculture. Tree growth was significantly increased by 51.5%-132.8% in the conifer and broadleaved tree species mixing plantations and in the fast-growing and nitrogen fixation tree species mixing plantations, when two tree species or four tree species were mixed. There was no significant difference in tree growth among different tree species mixed types, when six tree species were mixed. The contents of soil nitrogen, phosphorus and organic matter were the main factors affecting tree growth. The results indicated that young tree growth could be improved through the selecting conifer and broadleaved tree species mixing, fast-growing and nitrogen fixation tree species mixing in south subtropical plantations.

Changes of non-structural carbohydrates and nitrogen contents of needles and twigs in Pinus sylvestris var. mongolica plantations along an aridity gradient

ZHAI Pei-feng, GUAN Jia-xin, HE Peng, LIU He-yong, MAN Liang, JIANG Yong, MA Cheng-cang

2022, 33(6):  1518-1524.  doi:10.13287/j.1001-9332.202206.005

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With six Pinus sylvestris var. mongolica plantations (Huinan, Xifeng, Fujia, Zhanggutai, Naiman and Wulanaodu) along an aridity gradient in the Horqin sandy land, we examined the changes in non-structural carbohydrates (NSCs) and nitrogen (N) contents of current and one-year-old needles and twigs, to explore the carbon supply and demand status as well as the nutrient accumulation strategies of P. sylvestris var. mongolica under drought. The results showed that the contents of NSCs and soluble sugars in needles and twigs of P. sylvestris var. mongolica plantations significantly decreased with increasing aridity. From the most humid site (Huinan) to the most aridity site (Wulanaodu), the soluble sugar contents in current and one-year old needles of P. sylvestris var. mongolica decreased from 12.8% and 12.5% to 9.0% and 9.5%, respectively. The soluble sugar contents in current-year old twigs decreased from 15.6% to 9.2%. With increasing aridity, the starch contents in needles and twigs remained relatively stable, soluble sugars/starch ratio in current and one-year old needles decreased, the N contents in current and one-year old twigs significantly increased. The P. sylvestris var. mongolica plantations in the Horqin sandy land consumed soluble sugar storage under drought, resulting in a risk of mortality from ‘carbon starvation’. P. sylvestris var. mongolica tended to maintain stable starch storage and accumulate N in twigs to cope with long-term drought stress.

Spatial-temporal variation of vegetation water use efficiency and its relationship with climate factors over the Qinghai-Tibet Plateau, China

CUI Xi-lin, HE Yun-ling, LI Zong-shan

2022, 33(6):  1525-1532.  doi:10.13287/j.1001-9332.202206.024

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Water use efficiency (WUE) is an effective index to study the coupling of land carbon and water cycle. The Qinghai-Tibet Plateau is the most important ecological security barrier in China. Understanding the characteristics and mechanism of WUE is important for the carbon cycle and water resources rational utilization in the plateau. Based on MODIS data of gross primary productivity (GPP) and evapotranspiration (ET), we analyzed the spatial-temporal variations of WUE over the Qinghai-Tibet Plateau and the effects of climate factors. The results showed that WUE in the Qinghai-Tibet Plateau had an upward trend under the combined action of GPP and ET during 2001-2020. The southeast and northeast of the Plateau had the highest WUE value, while the central part had the lowest WUE value. WUE of grassland, marsh and alpine vegetation showed an increasing trend, while that of shrub land, broadleaved forest and coniferous forest showed a decreasing trend. There was a significant positive correlation between WUE and annual air temperature, and the sensitivity increased with the increases of air temperature. The relationship between WUE and annual precipitation was non-linear. When precipitation was less than 700 mm, the sensitivity of WUE to precipitation decreased with the increases of precipitation. When precipitation was more than 700 mm, the sensitivity of precipitation increased with the increases of precipitation. However, WUE was negatively correlated with precipitation in more than 75% of regions, and was affected by precipitation in a larger area. In the future, warm and humid climate would lead to a decrease in WUE.

Temporal and spatial variations of net primary productivity (NPP) and its climate driving effect in the Qinghai-Tibet Plateau, China from 2000 to 2020

LIU Jie, JI Yu-he, ZHOU Guang-sheng, ZHOU Li, LYU Xiao-min, ZHOU Meng-zi

2022, 33(6):  1533-1538.  doi:10.13287/j.1001-9332.202206.025

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Qinghai-Tibet Plateau is a “climate change laboratory” for China and the world. Driven by climate change, net primary productivity (NPP) in the Qinghai-Tibet Plateau has significant variations. Using the data of normalized difference vegetation index, digital elevation, annual precipitation, and annual temperature, we explored the temporal and spatial variation characteristics of NPP and its correlation with climate factors on the Qinghai Tibet Plateau from 2000 to 2020. The results showed that NPP of the Qinghai-Tibet Plateau increased significantly from 2000 to 2020, with an increase rate of 1.67 g C·m^-2·a^-1. The NPP was significantly positively correlated with temperature and precipitation. The climate trend of warming and wetting was an important driving force to promote the significant increase of NPP. The increases of NPP would continue if the climate become warmer and wetter.

Relationship between surface dead fuel loadings and environmental factors in southern Jiangxi, China

WU Qing-yun, WU Zhi-wei, Robert E. Keane, LIN Shi-tao, LI Shun, SHAN Yan-long

2022, 33(6):  1539-1546.  doi:10.13287/j.1001-9332.202206.021

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The distribution pattern of forest fuel loading is driven by the interaction of environmental factors, such as terrain and vegetation. Based on field sampling data of surface dead fuels of seven main forest types in southern Jiangxi Province, and according to the classification standard of different time-lags, we constructed structural equation models to explore the relationship between surface fuel loadings and environmental factors such as terrain and vegetation etc. We analyzed the influence path of each factor and its direct, indirect, and total influence. The results showed that the coniferous and broad-leaved mixed forest had the highest loadings and the Phyllostachys heterocycla pure forest had the lowest loadings for all the 1, 10, and 100 h time-lag fuels. The influencing coefficient of environmental factors for 1 h time-lag fuels were ranked as: slope (0.40) > crown height (0.07) > tree species (-0.03) > canopy closure (0.01). For the 10 h time-lag fuels, the environmental factors were ranked as: diameter at breast height (0.15) >tree species (-0.09) > aspect (-0.08) > canopy closure (-0.06). For the 100 h time-lag fuels, the environmental factors were ranked as: aspect (0.25) > diameter at breast height (0.19) > canopy closure (-0.08) > tree species (0.02). The influencing coefficient of environmental factors for the total fuels were ranked as: slope (0.22) > tree species (-0.04), canopy closure (-0.04) > crown height (-0.01).

Applicability of mixed effect model in the prediction of forest fire

ZHANG Zhen, YANG Song, ZHU He, WANG Guang-yu, GUO Fu-tao, SUN Shuai-chao

2022, 33(6):  1547-1554.  doi:10.13287/j.1001-9332.202206.026

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Fire is an important influencing factor in forest ecosystems. Establishing an accurate forest fire forecasting model is important for forest fire management. We used different meteorological factors as predictors to construct a forest fire prediction model in Fujian Province, based on Logistic regression and generalized linear mixed effect model. We compared the fitness and prediction accuracy of the two models, judged the applicability of the mixed effect model in forest fire forecasting. The results showed that the AUC and accuracy values of the Logistic base model were 0.664 and 60.4%, respectively. Models considering random effects gave better fitting and validating statistics. Among them, the two-level mixed model containing both area and altitude difference effects performed best, with increases of 0.057 and 6.0% for the AUC and accuracy values, respectively. By applying the model to predict the probability of forest fires in Fujian Province, we found that the middle-incidence and high-incidence areas of forest fires distributed in northwest and south Fujian, whereas the low-incidence areas of forest fires distributed in southwest and east Fujian, which was consistent with the observed data. The data fitting and forest fire prediction of the mixed effects model was better than those of the Logistic basic model. Therefore, it could be used as an important tool for forest fire prediction and management.

Effects of mowing regime on community characteristics and forage yield and quality in Hulun Buir, China

ZHANG Xiao-jing, MA Wang, WANG Zheng-wen

2022, 33(6):  1555-1562.  doi:10.13287/j.1001-9332.202206.004

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In order to select a best mowing regime for natural grassland in Hulun Buir with highly efficient hay-making and sustainable utilization, we conducted an experiment to examine the effects of mowing time (July 31, August 10, August 20, August 30, and September 9), stubble height (3, 9, and 15 cm), and their interaction on grassland community characteristics and forage yield and quality in a grassland of Hulun Buir from 2019 to 2021. The results showed that late mowing and low stubble-height mowing significantly reduced community-level height and coverage in the next year. Low stubble-height mowing reduced community aboveground biomass in the following year, but the effect of mowing time was not significant. The relative biomass of grasses and sedges first increased and then decreased with the delay of mowing time, forbs showed an opposite pattern, and legumes showed no signi-ficant change. Low stubble-height mowing could enable higher hay yield in the same year, but resulted in substantial reduction in the next year. When mowing on August 30 with 3 cm high stubble left, the hay yield reached maximum value of 469 g·m^-2, which was 361.5% of the minimum value. The crude protein content of forage reached the maximum at the mowing time of August 30, which was higher than the minimum value by 6.5%, and the content was higher at high stubble-height mowing. The contents of acid and neutral detergent fiber increased gradually over the growing season, with those from mowing on September 9 being 8.0% and 5.9% higher than those from mowing on July 31 respectively, and were decreased with the increases of stubble height. We found that the reasonable mowing regime of Hulun Buir grassland as the mowing implemented from August 20 to 30 with about 9 cm high stubble left. Long-term mowing experiments are needed to draw a more reliable and objective conclusion.

Effects of chamber characteristics on CO₂ and CH₄ flux at the water-air interface measured by the chamber method

JIA Lei, ZHANG Mi, PU Yi-ni, ZHAO Jia-yu, XIE Yan-hong, XIAO Wei, LIU Shou-dong, SHI Jie

2022, 33(6):  1563-1571.  doi:10.13287/j.1001-9332.202206.019

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The chamber method is widely used to measure CO₂ and CH₄ flux in inland water. However, the designs of chamber used in various studies are different and lack unified standards, which would affect the observation results. To clarify the impacts of chamber characteristics, including light transmittance, air pressure difference inside and outside the chamber, and gas mixing degree in the chamber, on CO₂ and CH₄ flux measurements at the water-air interface, we compared the effects of transparent/opaque chamber, the chamber with/without air pressure equalizing device and fan on CO₂ and CH₄ flux measurements in the aquaculture pond, based on the multi-channel closed dynamic chamber system. The results showed that, during the daytime in summer, compared with the transparent chamber which could measure the actual CO₂ flux, when CO₂ was emitted from the pond, the opaque chamber overestimated the CO₂ flux by 90%; when CO₂ was absorbed by the pond, the opaque chamber underestimated the CO₂ flux by 50%. The CH₄ diffusion flux measured by the opaque chamber was 40% lower than that measured by the transparent chamber. There was no significant difference between CO₂ and CH₄ flux measured by the chamber with and without air pressure equalizing device. CO₂ flux observed by the chamber without fan had poor representativeness, being 20% higher than that observed by the chamber with fan. Moreover, CH₄ flux emitted through different pathways could not be distinguished using the chamber without fan. Therefore, when the chamber method was used to observe the CO₂ and CH₄ flux at the water-air interface, the chamber shall be transparent and be installed with fan.

Temporal and spatial variations of annual precipitation and meteorological drought in China during 1951-2018

LU Chang, MA Long, LIU Ting-xi, HUANG Xing

2022, 33(6):  1572-1580.  doi:10.13287/j.1001-9332.202206.022

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Exploring the temporal and spatial variations of precipitation and drought is an important topic in hydro-logy. Based on the precipitation data of 619 meteorological stations in China from 1951 to 2018, we used anomaly percentage method and Morlet wavelet analysis to analyze the temporal and spatial variations of annual precipitation and drought. The results showed that annual precipitation in China showed a stepwise decreasing trend from southeast to northwest during the study period, and that the intensity of annual precipitation change was on the contrary. The precipitation near the boundary of the second and third steps showed a downward trend, and the abrupt change of precipitation occurred mainly in the 1960s and 1970s. The rest region was on the rise, with substantial changes in the 1990s. The main period of precipitation was short in the regions with temperate continental climate and temperate monsoon climate. From 1960s to 2010s, the area of arid land in China had decreased, while that of the semi-arid area and semi-humid area had increased gradually, especially in the recent decade. An aridity boundary was found between 30° N and 40° N, with drought frequency in its north being much more than the south. On the whole, the frequency and scope of drought events showed a decreasing trend and its interdecadal shift direction was from the central part of northwest China to the southern part of North China and then to the northern part of North China.

Establishment of indices for soybean low temperature damages in key growth stage in high cold region

LYU Jia-jia, ZHU Hai-xia, QU Hui-hui, GAO Xi-ning, LI Yu-dong, WANG Liang-liang, YAN Ping, JIANG Li-xia

2022, 33(6):  1581-1588.  doi:10.13287/j.1001-9332.202206.035

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Establishment of indices for low temperature damage of soybeans is important for systematically analyzing the adaptation strategies to climate change and collaborative adaptation technology for disaster prevention and mitigation and other stresses in high cold region. Based on historical data of low temperature damage and phenophase of soybean from 1980 to 2020 and daily temperature data from 78 meteorological stations in Heilongjiang Province, we used GIS to match the phenophase and meteorological data, by considering the accumulated temperature anomaly in different growth stages, and constructed a comprehensive soybean low temperature damages index (CSCDI) in high cold region. Using K-S distribution fitting test and the lower limit value of confidence intervals, we constructed the level index of soybean low temperature damage. The results showed that the CSCDI lower limits of mild, moderate and severe low temperature damage were 0.061, 0.115 and 0.237 from sowing to emergence stage, were 0.072, 0.152 and 0.312 from emergence to flowering, and 0.133, 0.245 and 0.412 from flowering to maturity, respectively. The time distribution of soybean low temperature damage inversed by CSCDI in Heilongjiang Province was consistent with the historical disaster records. The spatial distribution showed obvious latitude characteristics, with the frequency of low temperature damage increasing gradually from south to north.

Using the environmental justice approach to evaluate equitable allocation of urban parks: A case study of main urban area of Nanjing, China

XU Yu-xi, CHEN Yi-xin, SU Jie, YIN Hai-wei, CHENG Long, ZENG Hui

2022, 33(6):  1589-1598.  doi:10.13287/j.1001-9332.202206.027

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Urban parks have broad benefits in promoting public health of urban residents and advancing urban sustainable development. The equity of urban park spatial allocation has a great significance for maintaining environmental justice. However, the current researches on the equity of urban park spatial allocation still focus on the quantity and geographical equality but pay less attention on the equity of quality and accessibility of spatial allocation. Based on the approach of environmental justice, with the main urban area of Nanjing as an example, we comprehensively analyzed the equity pattern of urban park spatial allocation from the three dimensions (six parameters), including park accessibility, area and quality. Integrated analysis methods were adopted, including internet map service for accessibility analysis, subjective and objective comprehensive quality evaluation, spatial autocorrelation and non-parametric test. The results showed that the spatial allocation pattern of urban parks in the study area had obvious core-edge characteristics. There was a certain degree of inequity in park accessibility, area and quality, with a relatively significant pattern of environmental injustice. There were significant differences in the inequity of six parameters in the three dimensions, with the accessibility score and accessible park area showing the most prominent inequity. The minimum time required to reach the park and the quality of the nearest urban park took the second place in inequity. The quantity of high-quality urban park and minimum time required to reach the high-quality urban park showed relatively small difference. The average values of accessibility score, total area and quality of urban parks accessible to high-income communities were 3.7, 2.7, and 1.6 times that of low-income communities, respectively. The results indicated that high-income communities enjoyed better accessibility, larger area and higher quality in terms of urban parks. Middle-income communities enjoyed the most prominent advantage of green space, while most low-income communities were unable to reach a high-quality urban park within 30 min’s walk. Our results could provide a decision-making basis and planning reference for the optimal configuration and rational planning of urban parks in China.

Spatial relationship between landscape ecological risk and ecosystem service value in Fujian Province, China during 1980-2020

ZHU Run-miao, CHEN Song-lin

2022, 33(6):  1599-1607.  doi:10.13287/j.1001-9332.202206.023

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Understanding the relationship between landscape ecological risk and ecosystem service value (ESV) is important for building an ecological security pattern and enhancing human well-being. Taking Fujian Province as the research area, based on the remote sensing monitoring data of land use in 1980, 2000, and 2020, we carried out a grid resampling size of 5 km × 5 km in the study area, quantitatively evaluated the landscape ecological risk and ESV, and analyzed the spatio-temporal variations. The spatial correlation between landscape ecological risk and ESV was investigated by using the bivariate spatial autocorrelation analysis and the spatial regression models. The results showed that the landscape ecological risk level in Fujian Province changed from medium level to low level, with the situation being improved. The landscape ecological risk level was generally higher in the east region and lower in the west region. ESV generally declined. The functional structure of each ecosystem was relatively stable. ESV spread from high to low with high value area as the core. There was a significant negative spatial correlation between landscape ecological risk and ESV. Landscape ecological risk had a negative effect on ecosystem total ser-vice value, with the strongest impact on the supply function.

Dynamic monitoring and evaluation of ecological environment quality in Zhouqu County, Gansu, China based on Google Earth Engine cloud platform

YUE Yi-fan, CHEN Guo-peng, WANG Li, YANG Jun, YANG Ke-tong

2022, 33(6):  1608-1614.  doi:10.13287/j.1001-9332.202206.036

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Zhouqu County is located in the transition region from the Qinghai-Tibet Plateau to the Qinba Mountains, and is an important part of the ecological barrier in the upper stream of the Yangtze River. In this study, we used the Google Earth Engine cloud processing platform to perform inter-image optimal reconstruction of Landsat surface reflectance images from 1998-2019. We calculated four indicators of regional wet, green, dry, and hot. The component indicators were coupled by principal component analysis to construct remote sensing ecological index (RSEI) and to analyze the spatial and temporal variations of ecological environment quality in Zhouqu County. The results showed that the contribution of the four component indicators to the eigenvalues of the coupled RSEI were above 70%, with even distribution of the loadings, indicating that the RSEI integrated most of the features of the component indicators. From 1998 to 2019, the RSEI of Zhouqu County ranged from 0.55 to 0.63, showing an increasing trend with a growth rate of 0.04·(10 a)^-1, and the area of better grade increased by 425.56 km². The area with altitude ≤2200 m was dominated by medium and lower ecological environment quality grade, while the area of better ecological environment quality grade area increased by 16.5%. The ecological and environmental quality of the region from 2200 to 3300 m was dominated by good grades, increasing to 71.3% in 2019, with the area of medium and below ecological and environmental quality grades decreasing year by year. The area with altitude ≥3300 m was dominated by the medium ecological quality grade. The medium and below ecological quality grades showed a “U” shape trend during the study period. The trend of ecological environment quality in Zhouqu County was becoming better, but with fluctuations. It is necessary to continuously strengthen the protection and management of ecological environment in order to guarantee the continuous improvement of ecological environment quality.

Allergenic risk analysis of street trees of urban alleys in Qingyang District, Chengdu, China

TANG Yu-qian, WU Xiao-yi, ZONG Hua

2022, 33(6):  1615-1621.  doi:10.13287/j.1001-9332.202206.020

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We examined the pollen allergy risk of street trees in urban alleys, with 410 urban alleys in Qingyang District, Chengdu as an example. On the basis of recording the characteristics of street trees, we calculated the index of allergenicity of urban green zones (I_UGZA) values and overlay the regional population density map, and finally obtained the pollen allergy risk map of urban alleys in Qingyang District. The results showed that there were 32461 street trees in 410 urban alleys, belonging to 27 families, 41 genera, and 52 species. The distribution of tree species was extremely uneven, with excessive plantation of Ficus concinna (31.8%), Ginkgo biloba (12.9%) and Cinnamomum camphora (8.5%). The risk of pollen allergy in urban alleys was high, with an average I_UGZA value of 2.61 and spring as the primary risk season. Among them, 175 alleys were at the most low allergy degree (I_UGZA=0-1), 174 alleys at low degree of allergy (I_UGZA=1-5), and 6 alleys at extremely high risk of allergy (I_UGZA=15-20). Results of correlation analysis showed that mean tree height and canopy-to-street area ratio were the key factors affecting I_UGZA of street trees in urban alleys. After superimposing the population density map, Shaocheng Street, Caoshi Street, Xiyuhe Street, Funan Street, and Supo Street had a high risk of pollen allergy.

Responses of soil ammonia-oxidizing microorganisms to simulated nitrogen deposition in a natural Castanopsis carlesii forest

FENG Meng-meng, LIN Yong-xin, HE Zi-yang, LIU Xiao-fei, CHEN Shi-dong, WAN Song, DUAN Chun-jian, YE Gui-ping, HE Ji-zheng

2022, 33(6):  1622-1628.  doi:10.13287/j.1001-9332.202206.032

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Subtropical region of China is one of the global hotspots receiving nitrogen deposition. Nitrogen deposition could affect the abundance and community structure of ammonia oxidizers including ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA) and complete ammonia oxidizer (comammox Nitrospira), with consequences on soil nutrient cycling that are driven by microorganisms. There is limited understanding for the newly discovered comammox Nitrospira in the subtropical forest soils. Here, we investigated the effect of simulated N deposition on abundances of soil ammonia oxidizers in the Castanopsis fargesii Nature Reserve in Xinkou Town, Sanming City, Fujian Province, China. Soil samples were collected from the field plots which received long-term nitrogen deposition with different dosages, including: CK, no additional treatment; LN, low nitrogen deposition treatment, dosage of 40 kg N·hm^-2·a^-1; and HN, high nitrogen deposition treatment, dosage of 80 kg N·hm^-2·a^-1. After 8-year treatment, simulated N deposition decreased soil pH and organic matter content, and increased nitrate content. We failed to amplify the amoA gene of AOB in the tested soils. High nitrogen deposition increased the abundance of AOA, but did not affect the abundance of comammox Nitrospira clade A and clade B. The ratio of comammox Nitrospira to AOA decreased with N addition, indicating that N addition weakened the role of comammox Nitrospira in nitrification in the subtropical forest soils. However, there were strong non-specific amplifications for both comammox Nitrospira clades A and B, highlighting the demand for the development of high coverage and specificity primers for comammox Nitrospira investigations in the future. The abundance of comammox Nitrospira clade A was positively correlated with total nitrogen (TN) and NH₄⁺ concentration, while that of clade B was positively associated with soil organic carbon (SOC), TN and NH₄⁺ Concentration. Overall, our findings demonstrated that simulated N deposition increased the relative importance of AOA in nitrification in the natural Castanopsis carlesii forest soil. These findings could provide theoretical support in coping with global change and N deposition in these regions.

Adaptability of Broussonetia papyrifera to sewage sludge and its characteristics of nutrient and heavy metal uptake and accumulation

FENG Jia-yi, RUAN Ke-jin, SU Si-ning, ZHANG Xue-ping, WU Dao-ming, WAN Li-xin, ZENG Shu-cai

2022, 33(6):  1629-1638.  doi:10.13287/j.1001-9332.202206.030

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Broussonetia papyrifera, an important fast-growing economic tree species in China, has the advantages of strong adaptability, high-biomass, and high bioconcentration of heavy metals. Sewage sludge contains a great deal of nutrients and heavy metals. Planting B. papyrifera with sewage sludge can achieve the goals of sewage sludge remediation as well as resources production of B. papyrifera. A pot experiment was conducted to investigate growth, uptake and accumulation of nutrient and heavy metal in different organs (root, stem, leaf) of B. papyrifera, with treatments of control (lateritic red soil), 50% sewage sludge (mixed substrates of 50% sewage sludge and 50% lateritic red soil based on weight) and 100% sewage sludge. The comprehensive evaluation of capacity of uptake and accumulation was also carried out by principal component analysis and membership function. The results showed that B. papyrifera could grow normally in both 50% and 100% sewage sludge substrates, with higher plant height and biomass than that in the control, especially in 100% sewage sludge substrate. The quality index in 100% sewage sludge substrate (1.02) was 4.3 times and 2.4 times as that of the control and 50% sewage sludge substrate, respectively. The content of N in different organs and P in stem increased significantly in both 50% and 100% sewage sludge substrates. The content of K in stem and leaf was significantly decreased in 100% sewage sludge substrate, which were significant lower than that of control. The uptake of heavy metals such as Cu, Zn, Pb, Cd, Ni for B. papyrifera were mainly through roots. There was positive correlation between the content of heavy metals in root and sewage sludge ratio. The content of Pb and Cd in leaves were lower than the limit value of Hygienic Standard For Feeds (GB 13078-2017). The capacity for absorption and accumulation of Cd was better than that of other heavy metals. Compared with the control, rootretention rates of Zn, Pb and Cd significantly increased in both 50% and 100% sewage sludge substrates (57.8%-85.8%), while Cu and Ni significantly increased in 100% sewage sludge substrate (67.5% and 74.8%). Nutrient and heavy metal accumulations in total plant in both 50% and 100% sewage sludge substrates were significantly higher than that in the control, with 100% sewage sludge substrate being significantly higher than that in 50% sewage sludge substrate. Compared with 50% sewage sludge substrate, the increment rates of nutrient and heavy metal accumulations in different organs as well as total plants in 100% sewage sludge substrates were greatly increased. The rank of comprehensive evaluation scores of adaptability, element uptake and accumulation was in an order: 100% sewage sludge substrate (0.848) > 50% sewage sludge substrate (0.344) > control (0.080). With good adaptability to sewage sludge, B. papyrifera could grow normally in sewage sludge andeffectively absorb and fix nutrients and heavy metals. It is feasible to plant B. papyrifera into the sewage sludge for remediation of sewage sludge and resource production.

Ecological risk assessment of contaminated soil using improved “Weight of Evidence”approach:A case study of electroplating site in Jingjiang, Jiangsu, China

WANG Mei-e, MA Wan-kai, JIANG Rong, XIE Tian

2022, 33(6):  1639-1651.  doi:10.13287/j.1001-9332.202206.017

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Ecological risk assessment of soil in contaminated sites provides the scientific basis for accurately developing soil quality standards, confirming remediation targets, and making safe use of contaminated soil. It thus is a critical mean to protect soil health and safety. “Weight-of-Evidence” (WoE) has been widely used in ecological risk assessment due to its systematic, integrated and scientific properties. However, most current WoE approaches are poor in objectivity and comparability because they rely too much on expertise scoring in weighing and the difficulty to collect complete evidence bodies with quantitative and comprehensive information. Focusing on those issues above, we developed an improved framework of WoE approach for ecological risk assessment of contaminated site soil based on the “Four-Step” framework of EPA coupled with the concept of hierarchy. Assessment methods and procedures for each tier were unified. Weights were weighed quantitatively through multiple criteria decision analysis. The relative independence among bodies of evidence was assured by the pre-establishment of hierarchy. The “site specific” was stressed based on matrix trails and field investigation. Finally, a case study in an electroplating site in Jingjiang was conducted to verify the approach. Results of the case study suggested that the approach was practical and that the assessment results were objective, scientific, and accurate.

Effects of temperature on growth, survival, and reproduction of Conogethes punctiferalis feeding on corn kernels

PANG Yun-shun, LI Shao-hua, WANG Rong-cheng, CHI Hsin, LIU Xiao-yu, WANG Hong-yu, LI Xiang-dong, ZHENG Fang-qiang

2022, 33(6):  1652-1660.  doi:10.13287/j.1001-9332.202206.016

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In order to examine the effects of temperature on the growth, survival, and reproduction of Conogethes punctiferalis (Lepidoptera: Crambidae) feeding on corn kernels, the life table parameters of C. punctiferalis at 21, 24, 27, 30 ℃ were calculated based on the age-stage two-sex life table theory, and then population dynamics of C. punctiferalis was projected based on these parameters. The results showed that the life cycles of the pest could be finished at all the four temperature treatments. The developmental duration of each stage shortened with increasing temperature, and there were significant differences among treatments. The highest fecundity (116.7 eggs per female), preadult survival rate (84.7%), and proportion of female (0.46) were observed at 24 ℃. The intrinsic rates of increase at 24, 27, 30 ℃ were 0.1059, 0.1101, and 0.1045 d^-1, respectively. The finite rates of increase were 1.1117, 1.1164, and 1.1102 d^-1, respectively. There was no significant difference among the three treatments, but the r and λ values were significantly higher than those at 21 ℃. The net reproductive rates (R₀) at 21, 24, 27, 30 ℃ were 17.3, 53.7, 36.9, and 19.8, respectively. R₀ at 24 ℃ was the highest. It suggested that survival rates, fecundities and female proportions of C. punctiferalis population were high at 24-27 ℃, which was the suitable temperature range for its growth, survival, and reproduction.

Effects of Agasicles hygrophila herbivory on the clonal integration of Alternanthera philoxeroides and A. sessilis

QIN Hai-rong, GUO Wen-feng, WANG Wei, YANG Sha, LI Xiao-qiong

2022, 33(6):  1661-1668.  doi:10.13287/j.1001-9332.202206.018

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Many alien invasive plants were clonal species. Examining the relationship between clonal integration characteristics and invasiveness of alien clonal plants is important for clarifying their ecological adaptability and invasion mechanisms. Here, with the invasive plant species Alternanthera philoxeroides and its native congener A. sessilis as the studying objects, we compared the effects of clonal integration on the growth and the biomass allocation of the apical ramets, basal ramets, and the whole fragment of both species under herbivory by the biocontrol beetle Agasicles hygrophila. The results showed that under herbivory by A. hygrophila, leaf number, stolon length, and ramet number of the apical ramets as well as the ground diameter of the whole fragment of A. philoxeroides were significantly higher under clonal integration treatment compared to that without clonal integration, whereas belowground biomass and total biomass of the basal ramets and the whole fragment of A. philoxeroides were conversely decreased by 78.2%, 60.9 % and 48.7%, 37.2%, respectively, under clonal integration treatment compared to that without clonal integration. Ground diameter of the apical ramets and leaf number of the whole fragment of A. sessilis were significantly higher, but the number of basal ramets was 21.7% lower under clonal integration treatment compared to that without clonal integration. The biomass of the apical ramets, basal ramets, and whole fragment of A. sessilis did not significantly differ between clonal integration and without clonal integration treatments. The results of cost-benefit analysis showed that the ramet number and biomass of the apical ramets of A. philoxeroides as well as the ramet number of the apical ramets of A. sessilis were significantly benefited from clonal integration, but the cost-benefit of the ramet number and biomass of the basal ramets of both species were not affected by clonal integration treatment. These results suggested that clonal integration could partly alleviate herbivory pressure by A. hygrophila on the apical ramets of both species, and that the clonal integration ability of A. philoxeroides was stronger than A. sessilis. However, both species seemed not able to gain significant benefits from cloning integration at the whole fragment level.

Screening and identification of a Burkholderia strain and optimization of its phosphate solubilizing capacity

CHEN Rong-bin, ZUO Zhen-yu, HUANG Bo-hui, LI Ling-ling, MEI Yu-hang

2022, 33(6):  1669-1678.  doi:10.13287/j.1001-9332.202206.031

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In order to solve the problem that soil soluble phosphorus content in most cultivated land in China is insufficient and the plant growth is inhibited, a phosphate solubilizing microorganism (PB) was screened and identified, and its phosphate solubilizing performance was optimized. The results showed that the PB strain was belonged to Burkholderia stabilis. It had the ability of nitrogen fixation and indole-3-acetic acid (IAA) secretion, as well as a certain inhibitory effect on Escherichia coli. It could maintain high activity and phosphorus solubilizing ability at pH 8.0-10.0, indicating good alkali resistance. The results of phosphorus dissolving performance optimization showed that the phosphate solubilizing capacity of strain PB reached the best at 30℃, pH 7.0, 180 r·min^-1, using glucose as carbon source, ammonium sulfate as nitrogen source, tricalcium phosphate as phosphorus source and adding 50 μmol·L^-1 lysine. The amount of dissolved phosphorus was 569.33 mg·L^-1, which was 1.9 times of that before optimization. The strain mainly secreted citric acid, malonic acid, and glucuronic acid during metabolism. After adding lysine, the type of organic acids secreted by the strain did not change, but the content increased significantly. Results from pot experiments showed that the application of PB bacterial fertilizer could significantly improve the growth and physiological indicators of garlic seedlings, and that the promotion effect was more obvious after adding lysine. Compared with the control, the height of seedling was increased by 18.6%, seedling diameter was increased by 16.7%, aboveground fresh and dry weight were increased by 22.1% and 15.7%, and belowground fresh and dry weight were increased by 22.0% and 28.7%, respectively in PB with lysine treatment. Soil available phosphorus content was 2.1 and 2.3 times of the control in PB and PB+lysine treatments, indicating that PB could improve soil available phosphate content. Adding lysine could strengthen such function.

DNA damage in hepatopancreas cells of Haliotis discus hannai induced by P-xylene

XU Cui-ya

2022, 33(6):  1679-1685.  doi:10.13287/j.1001-9332.202206.015

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In order to examine the toxic effects of p-xylene on the hepatopancreas of Haliotis discus hannai, a subchronic toxicity test was carried out for 21 days by setting 4 concentrations (0.5, 1.0, 1.5, and 2.0 mg·L^-1) and the control group. DNA damage in hepatopancreas cells of H. discus hannai was analyzed by comet assay. The CASP analysis software was used to analyze the damage indices, including tail rate, tail length, percentage of tail DNA, and olive moment. The results showed that DNA damage in hepatopancreas cells occured in all exposed groups, with different degrees of damage. The DNA damage of hepatopancreas cells was aggravated with the increase of exposure concentration. High concentration of p-xylene could induce apoptosis, showing a certain dose-damage effect. Short-term exposure to medium concentration of p-xylene could cause DNA damage in hepatopancreas cells of H. discus hannai, and the damage degree increased with the extension of exposure time, showing a certain time-damage effect. However, the damage indices of DNA decreased after prolonged exposure, which might be related to the DNA repair mechanism of the cell and the metabolic mechanisms of the detoxification system. In conclusion, p-xylene could induce oxidative damage in hepatopancreas cells of H. discus hannai, resulting in DNA fragmentation. Prolonged exposure to high concentration of p-xylene could lead to apoptosis.

Habitat characteristics of Octopus ocellatus and their relationship with environmental factors during spring in Haizhou Bay, China

CUI Yan-hua, LIU Shu-de, ZHANG Yun-lei, XU Bin-duo, JI Yu-peng, ZHANG Chong-liang, REN Yi-ping, XUE Ying

2022, 33(6):  1686-1692.  doi:10.13287/j.1001-9332.202206.033

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In recent years, a variety of important fishery resources in China’s coastal waters have declined. Octopus ocellatus has the characteristics of short life cycle and rapid growth, with great contributions to fisheries of China’s coastal waters. However, we know little about the habitat distribution characteristics of O. ocellatus and its relationship with environmental factors, which is not conducive to better protection and utilization of its resources. Here, we analyzed the distribution characteristics of O. ocellatus and its relationship with environmental factors using three machine learning methods, i.e., random forest model, artificial neural network model, and generalized boosted regression models, based on the survey data of fishery resources and habitat in Haizhou Bay during spring of 2011 and 2013-2017. Among the three models, random forest model had great advantages in the fitting effect and prediction ability. The model analysis results showed that sea bottom temperature, seawater depth and sea bottom salinity had significant effects on the habitat distribution of O. ocellatus. The relative resource density of O. octopus increased first and then decreased with the increases of sea bottom temperature, seawater depth, and sea bottom salinity. Based on environmental data simulated by the FVCOM model, we predicted the habitat distribution of O. ocellatus in Haizhou Bay using random forest model and found that O. ocellatus was mainly distributed in the area between 34.5°-35.8° N and 119.7°-121° E.

Defensive characteristics of cones of Pinus armandii against seed-eating animals

FENG Da-lin,YU Jing-jing, QU Chang, ZHENG Jiao-yang, WANG Zhong-bin, ZONG Cheng

2022, 33(6):  1693-1698.  doi:10.13287/j.1001-9332.202208.031

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During the co-evolution with animals, plants evolved different defense strategies to resist predators and ensure their own survival and reproduction. We investigated the forging preference of nutcrackers (Nucifraga caryocatactes) for seeds in different parts of bending Pinus armandii cones in Southeast Tibet. We measured the morphological characteristics (length, width, thickness, and seed hull thickness) and the physical and chemical properties of concave and convex seeds of P. armandii (crude water, dry-matter at 70 ℃, crude fat, ash, protein and crude fiber). The results showed that there were significant differences in seed shell thickness, kernel percentage and empty shell percentage between the concave and convex seeds. The seed shell thickness of convex seeds (1.11±0.12 mm) was thicker than that of concave seeds (1.07±0.15 mm). The kernel weight percentage of convex seeds (24.0%) was smaller than that of concave seeds (25.4%). The empty shell percentage (11.2%), crude fat content (47.0%) of convex seeds were significantly lower than that of concave seeds (15.8% and 50.5%). The curving cones of P. armandii cause false hints to seed eaters, and protect high-quality seeds from being eaten as much as possible. Therefore, the curving cone is a defensive characteristics of P. armandii against seed predators.

Reviews

Research advances in shrub dendroecology

LIU Jie, DONG Yan-jun, LI Zong-shan

2022, 33(6):  1699-1708.  doi:10.13287/j.1001-9332.202206.006

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The ecological value of shrub-ring data has received more and more attention. The tree-ring data of shrub species have been increasingly used to reveal growth dynamics of regional shrub vegetation and its sensitivity to climate change. Up to now, nearly 70 species of shrubs have been used in the studies of shrub dendrochronology, which considerably broadened the traditional tree-ring research network, enriched the research scope and object of dendrochronology, and certainly with great significance in revealing the characteristics of regional climate fluctuation and annual dynamics of structure, function and service for shrubland ecosystems. In this study, we systematically collected dendrochronological studies based on shrub species during the 1996-2021, and reviewed research progress in four main subfields (physiology, climatology, ecology and hydrology) in dendrochronology for shrub species. The characteristics of shrub growth and xylem anatomy under different environmental stresses were expounded. The main limiting factors for shrub growth in different climatic conditions and the history of regional climate fluctuations based on shrub-ring data were revealed. The individual growth and population dynamics of shrub species driven by climate and the changes in ecosystems caused by non-climatic factors were assessed, and the reconstructions of regional hydrological histories were compiled using tree-ring data of shrub species. Under the context of global warming, dendrochronological studies of shrub species in China should pay more attention to the responses of shrub species radial growth to drought stress under different moisture conditions in the semi-arid and arid regions and the transforming feature of distribution pattern and climate response sensitivity for shrub species under the background of climate change.

Responses of arbuscular mycorrhizal fungi to elevated atmospheric CO₂ concentration and warming: A review

SONG Ge, WANG Quan-cheng, ZHENG Yong, HE Ji-zheng

2022, 33(6):  1709-1718.  doi:10.13287/j.1001-9332.202206.014

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Global changes have profound impacts on biodiversity and ecological functioning of terrestrial ecosystems. Arbuscular mycorrhizal (AM) fungi can form symbiotic associations with most terrestrial plant species and play an important role in nutrient acquisition of host plants, promotion of plant growth, and maintenance of plant diversity. In this review, we primarily focused on the responses and feedbacks of AM fungal community and functioning to elevated atmospheric CO₂(eCO₂) and warming in forest and grassland ecosystems. eCO₂ influenced AM fungi mainly through indirectly impacting host plants and soil carbon inputs. A majority of previous studies reported that eCO₂ could enhance the abundance and activity of AM fungi, and influence their diversity and community composition. Warming could have direct and indirect (via plant and/or soil pathways) impacts on AM fungi. Warming significantly altered the community compositions of AM fungi in forest soils. But the results from grassland were not consistent. We identified some outstanding problems in current studies and proposed future research topics which deserve more attentions. Our aim was to elucidate the AM fungal responses and adaptation to eCO₂ and warming and to improve our understanding of AM fungal functioning in soil ecological processes. This review could provide insights into the implications of AM fungi to mitigate global change and improve the resilience of soil functions, as well as climate change adaptation of ecosystems.

Generation mechanism and control methods of antibiotic and heavy metal resistance genes in poultry waste: A review

LI Xiao-tian, HUANG Zhuo-shen, TANG You-qian, LIN Chang-quan, WANG Chun-ming

2022, 33(6):  1719-1728.  doi:10.13287/j.1001-9332.202210.029

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As antibiotics and heavy metals are often mixed in animal feed, their excretion through animal feces would cause bacteria to produce antibiotic resistance genes and heavy metal resistance genes. The pollution of antibiotics resistance gene and heavy metal resistance gene has become a major threat to human health and ecological environment. From the perspective of bacterial evolution, we proposed the importance of bacterial long-term evolution experiments about antibiotics and heavy metals. There is a complex co-selection resistance between antibiotic resistance genes and heavy metal resistance genes, which interact with each other and collectively determine the environmental behavior of bacteria. Horizontal transfer of resistance gene increases its variability in the environment. Mobile genetic elements play an important role in horizontal transfer of resistance gene. As for resistance gene pollution control, advanced oxidation technology has a good resistance gene removal effect. The UV/TiO₂ oxidation technology can reduce the abundance of antibiotic resistance genes of 4.7-5.8 log, with an efficiency of >99.99%. Other control strategies, such as the use of Macleaya cordata extract and the combination of bacteriophage and antibiotics, are also of significance for controlling resistance genes.