Table of Content

10 December 2018, Volume 37 Issue 12

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Pollen assemblages in surface soil and their relationships with vegetation and climate in northern Xinjiang.

WU Hui-xian, XU Hai, LAN Jiang-hu, ZHANG Ji-xiao, YAN Dong-na, ZHOU Kang-en, WANG Tian-li, YE Yuan-da

2018, 37(12):  3499-3507. 

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By comparing pollen assemblages in surface soil and cow dung samples in the dessert steppe and typical steppe in northern Xinjiang, we found similar pollen assemblages in both types of samples. The concentrations of tree pollen for most samples were lower than 10%, those of shrubs were on average 5.6%, and those of herbs were generally higher than 70%. Chenopodiaceae and Artemisia were the most important components of the pollen assemblages. The species number of pollen in cow dung samples was lower than that of surface soil samples. The pollen content of trees in cow dung (2.04%) was lower than that of surface soil (3.78%). The cow dung samples were produced in most recent months while the formation time of the surface soil samples was uncertain. It is likely that the pollen assemblages of cow dung should be more relevant to the modern vegetation types. We thus proposed that the cow dung could be used as a new archive of modern vegetation types in the dessert steppe and typical steppe. Furthermore, the pollen concentration of trees increased and that of the shrubs and herbs decreased in surface soil from dessert steppe to typical steppe. However, the pollen assemblages of cow dung showed an opposite trend, which is probably related to the diet of cows. Moreover, the principal component analysis of the main pollen assemblages (Rosaceae, Poaceae, Umbelliferae, and Leguminosae) and environmental factors revealed that the pollen assemblages had the strongest correlation with the mean precipitation during June-August and the mean annual precipitation, and the secondary strong correlation with the mean temperatures of the coldest and warmest months, but weak correlation with the mean annual temperature. Our results suggest that precipitation is likely the most important factor controlling vegetation distribution in northern Xinjiang.

Impacts of climate and topography on the treeline position across the Tibetan Plateau.

WANG Ya-feng, LIU Bo

2018, 37(12):  3508-3515. 

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Nonthermal factors, such as terrain, may influence treeline position. Such a fact would explain the uncoupling relationship between recent treeline dynamics and climate warming. Here, we tested this idea by analyzing juniper and sprucefir alpine treelines across the Tibetan Plateau which were located on sunny and shady slopes, respectively. We tested if slope aspect modulated the relationships between treeline elevation and climate on the Tibetan Plateau. Herein, treeline variables (elevation, topography) were collected from published investigations performed on the Tibetan Plateau to assess the impacts of slope aspect on treeline elevation. Temperature conditions at treeline sites were estimated using global climate database. We evaluated the relative contribution of different variables on treeline position including thermal (growingseason air temperatures) and nonthermal (aspect, precipitation) factors. The minimum temperature in July was the most important predictor of Tibetan Plateau treeline elevation, explaining 40% of the variation of treeline elevation, whereas slope aspect accounted for 7% of the variation. We concluded that treeline position across the Tibetan Plateau was mainly driven by the minimum temperature in July, whilst slope aspect played a second role. Our results provide insight into the mechanistic explanations for alpine treeline formation.

Effects of long-term nitrogen addition on litter production of Pinus tabuliformis forests in the Taiyue Mountain.

YANG Lu, ZHAO Bo, CHEN Ping, ZHAO Xiu-hai

2018, 37(12):  3516-3524. 

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To reveal the effects of long-term nitrogen (N) addition on litter production of Pinus tabuliformis forest, a 7-year N addition experiment was carried out in natural and planted forests in Taiyue Mountain, Shanxi Province, which included four levels of N addition (CK, 0; LN, 50; MN, 100; HN, 150 kg N·hm^-2·a^-1). Litter components were divided into leaves, branches, fruits, flowers, barks, and miscellaneous (animal debris, bud scales, and other debris). Litter biomass was monitored monthly from 2015 to 2016. The results showed that N addition significantly increased mean annual litterfall biomass in the natural forest, with the order: HN (3.69 t·hm^-2·a^-1) > MN (3.12 t·hm^-2·a^-1) > LN (3.02 t·hm^-2·a^-1) > CK (2.68 t·hm^-2·a^-1). In the plantation, the mean annual litter production increased but then decreased with the increasing N gradient, with the order: LN (3.11 t·hm^-2·a^-1) > CK (3.08 t·hm^-2·a^-1) > MN (2.92 t·hm^-2·a^-1) > HN (2.60 t·hm^-2·a^-1), indicating that excess N application can reduce the litter biomass in the plantation. The proportion of mean annual leaf biomass was among 68.3%-75.4%, and fruit biomass ranged from 6.7% to 17.8%. Nitrogen addition significantlyaffected litter biomass of leaf, fruit and bark. The temporal variation of total litter biomass was a doublepeak pattern with peaks in June and October. In conclusion, litter production was significantly increased with increasing N level in the natural forest (P<0.001), but no significant effect was found in the plantation (P>0.05).

Effect of nitrogen addition on leaf nitrogen resorption of Larix principis rupprechtii plantations with different ages.

ZHANG Wen, YAN Tao, CHANG Wen-jing, ZENG Hui

2018, 37(12):  3525-3532. 

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Under the context of increasing nitrogen (N) deposition, studies on the effects of N addition on leaf N resorption of plantations with different ages could improve our understanding of the response of forest ecosystems to climate changes. In this study, we explored the effects of different N addition levels (no N added as control, CK; 20 kg N·hm^-2·a^-1 as low N addition, N20; 50 kg N·hm^-2·a^-1 as high N addition, N50) on leaf dry mass, leaf volume, leaf N concentration and N resorption efficiency (NRE) of Larix principisrupprechtii with different ages (i.e. S11, S20 and S45 represented 11-, 20- and 45-year-old stand, respectively). The results showed that the dry mass of both green and senescent leaves decreased with increasing stand ages (P<0.05). During the leaf senescence, the loss of leaf dry mass in S20 was significantly greater than those of S11 and S45 (P<0.01). The loss of leaf volume in S45 was significantly lower than those in S20 and S11. N addition significantly decreased the volume of green leaf in S11 before senescence (P<0.05). Leaf N resorption efficiency of S11 was significantly lower than those of S20 and S45 (P<0.001). Furthermore, the reduction of NRE caused by N addition in S11 was significantly larger than the corresponding values in S20 and S45 (P<0.01). Our results areimportant for accurate assessment of N cycle in forest ecosystem and better understanding of growth strategies of forest ecosystems.

Effect of community structure adjustment of pure Populus tomentosa planataion on soil carbon in the semi-arid Loess Plateau of China.

MAN Zhou, HU Chan-juan, FENG De-xian, ZHAO Rong-qin, GUO Lei, HUANG Jia

2018, 37(12):  3533-3540. 

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Understanding the responses of soil carbon to forest structure adjustment is an important issue concerning vegetation restoration in semi-arid regions. In this study, total carbon, organic carbon, and inorganic carbon in soils of three different plantations (Populus tomentosa plantation, Populus tomentosaplantationtransformed with Pinus tabuliformis for 5 years, and Populus tomentosaplantation transformed with Pinus tabuliformisfor 10 years) were analyzed in a typical semi-arid loess watershed. The results showed that: (1) The temporal changes of soil total carbon and soil organic carbon concentration were similar. Concentrations of soil total carbon and soil organic carbon increased over time. Soil organic carbon storage in both mixed plantations was significantly higher than that in pure plantation. There was no difference in soil total carbon and inorganic carbon storage among the three plantations. (2) Soil carbon concentrations were significantly correlated with soil moisture, bulk density, and pH in different plantations. Increased soil moisture and decreased pH and bulk density had a synergistic effect with increasing soil carbon. Our results can provide scientific guidance to vegetation restoration and the enhancement of ecosystem services in the semiarid Loess Plateau.

Effects of forest types on soil organic carbon in semi-arid area: A case study of Huining County.

LI Meng-tian, QIN Yan-yan, CAO Jian-jun, XU Xue-yun, GONG Yi-fan

2018, 37(12):  3541-3548. 

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Exploring the effects of forest types on soil organic carbon (SOC) is critical for facilitating sustainable forestry management. Here, we compared SOC contents of three forest types, including apricot forest, poplar forest, and willow forest, in Huining County in central Gansu Province, China. The results showed that, under similar site conditions, SOC contents of all the three forest types decreased with increasing soil depth. SOC content of the apricot forest ranged from 2.85 g·kg^-1 to 19.05 g·kg^-1, while for the poplar forest and willow forest, it ranged from 1.67 g·kg^-1 to 11.9 g·kg^-1, and from 1.80 g·kg^-1 to 16.05 g·kg^-1, respectively. The apricot forest had significantly higher SOC content than the poplar forest and willow forest, but lower water conservation capacity than the poplar forest. SOC content was significantly negatively correlated to soil bulk density and pH across the three forest types. Soil water content was the dominant factor affecting SOC content of the poplar forest, pH and soil water content were the dominant factors in the willow forest, while pH and soil bulk density were the dominant factors in the apricot forest. Our results suggest that during implementing afforestation in semi-arid areas, the poplar should be the preferred species if only considering the benefits of soil and water conservation. If only considering the potential of carbon sequestration, however, the apricot forest is particularly important for reducing emission and enhancing carbon sink.

Self-healing of mechanical properties of Salix cheilophila straight roots under different damage conditions.

WANG Bo, LIU Jing, LI You-fang, ZHANG Xin, LI Qiang, LIU Jia-wei

2018, 37(12):  3549-3555. 

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Salix cheilophila, a common shrub in arid and semi-arid areas, is usually used for vegetation restoration in Inner Mongolia. To clarify the effects of exogenous mechanical damage on self-healing of root mechanical properties, changes of mechanical properties of straight roots with diameter of 1-4 mm under different damage degrees and different recovery durations were examined in situ using the HG100 digital push and pull tester and self-developed experimental installation. The results showed that: (1) There were significant differences in tensile force and tensile strength among undamaged roots with different diameters. Tensile force was positively correlated with the diameter (power function), with average tensile force being 77.14±38.23 N for roots with diameter of 1-4 mm. Tensile strength was negatively correlated with root diameter, with an average of 15.22±2.85 MPa. (2) Exogenous mechanical damage could impede the regular growth and development of plant roots. Such inhibitory effects differed with the degree of damage to the roots. Severe damage had a stronger inhibitory effect on root diameter growth than mild damage. After self-healing for three and five months， comparing with control, the severe damage could decrease the growth rate of root diameter by 25.19% and 29.96% respectively, and the mild-damage for 18.76% and 26.89%.  (3) Tensile force and tensile strength of roots were significantly decreased after mechanical damage, with such effects being gradually eliminated with the help of root selfhealing mechanism. The longer the root recovery time, the greater the recovery rate of mechanical properties. The average recovery rates of tensile force after self-healing for three and five months were 37.63% and 48.13% respectively. The degree of damage also affected the self-healing of mechanical properties. The recovery rates of mechanical properties for severe damage roots were significantly lower than those for mild-damage roots under the same recovery durations.

The therapy effects of four forest environments based on animal behavior.

SONG Yang, WANG Cheng, DUAN Wen-jun, HAO Ze-zhou, XU Xin-hui, WANG Zi-yan, HAN Dan, XU Shan-shan, DU Qian, WANG Han

2018, 37(12):  3556-3565. 

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An open-field experiment was conducted to analyze the impacts of the environment on the behavior of mice. We observed the behavior of mice in four different forest environments,including bamboo forest, conifer and broadleaf mixed forest, Cunninghamia lanceolata forest, and broad-leaved forest. The results showed that the total movement distance of the mice in each forest type was over 45% higher than that of indoor environment (CK), with no significant difference among the four forest types. The central grid movement distance of the four groups was over 50% higher than that of the CK. The four treated groups spent 63% more residence time in the central grid than that in the CK. There was no significant difference in central grid entering frequency among the four groups and the CK. The four groups had 8% higher standing frequency than the CK. There was no significant difference in body mass between the four groups and the CK. The CK group had the highest number of fecal particles (169.3), and the mixed coniferous and broad-leaved forest had the lowest (112.3). Relative humidity had a positive correlation with the number of fecal particles and body mass. Air pressure was positively correlated with the total movement distance, and significantly negatively correlated with the number of fecal particles. Wind speed was negatively correlated with the number of fecal particles and central grid entering frequency. Negative air ions were positively related to the total movement distance. In conclusion, the four forest environments promoted the behaviors of mice with different degrees of promotion. Conifer and broad-leaved mixed forest had the best effect on mice’s exploring ability and relieving pressure.C. lanceolata forest had the strongest effect on improving mice vitality. We suggest that people should choose forest environment for health care activities according to their needs.

Responses of soil fauna to ecological restoration of desertified alpine grasslands.

MA Jin-hao, WU Peng-fei

2018, 37(12):  3566-3575. 

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In September 2015, two different ecological restoration measurements were conducted by adding yak manure on soil surface of moderately desertified grasslands (MDG) and integrating the application of yak manure + seeds + plowing with 0-20 cm soil depth for severely desertified grasslands (SDG) in Zoigê. Soil arthropods, nematodes, plant communities and soil physical properties were investigated in ecological restoration plots of SDG, MDG, and corresponding control (CK) plots in September 2016. The results showed that plant community structure in SDG and MDG plots recovered and soil physical properties improved significantly after one year restoration compared to the CK. The community structure of soil arthropods and nematodes in the SDG and MDG plots differed from that of the CK, and the abundances were significantly higher than those of the CK (P<0.05). The taxonomic richness of soil arthropods and Shannon index increased and Simpson index decreased due to restoration treatments in SDG and MDG, but significant differences were only observed for SDG (P<0.05). The taxonomic richness and Shannon index of soil nematodes in restored SDG and MDG increased (P<0.05), and Simpson index significantly decreased (P<0.05). Results from regression analysis showed that the height and coverage of plant community were significantly related to the abundance and diversity of soil fauna communities. These results suggested that the community structure and diversity of soil fauna in desertified alpine grasslands were sensitive to ecological restoration treatments, with the soil nematode communities being more sensitive than soil arthropods. The responses of nematodes and arthropods were influenced by desertification degree of alpine grasslands.

Plant species abundance distribution patterns in Hulunbuir meadow steppe.

YANG Yang, ZHANG Feng, QIAO Ji-rong, JIA Li-xin, ZHAO Tian-qi, ZHAO Meng-li

2018, 37(12):  3576-3583. 

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Based on field survey, plant species abundance distributions under different utilization modes of the Hulunbuir meadow steppe were analyzed by mathematical models. The purpose of this study is to use mathematical models with different ecological significances to fit the true distribution of plant species under different ecological processes in meadow steppe. Chi-square (χ²), Akaike information criterion (AIC) and Bayesian information criterion (BIC) were used for verification. The results showed that the best fitting model of species abundance distribution in grazing, clipping, and enclosing grasslands was the broken stick model (BSM), with χ²=92.99, AIC=373.58, and BIC=378.49 for grazing grassland; χ²=98.51, AIC=307.76, and BIC=312.67 for clipping grassland; χ²=186.57, AIC=303.13, and BIC=307.53 for enclosing grassland. The fitting results of the niche overlap model (ONM) could also be accepted (χ²=422.69, AIC=409.25, BIC=414.16) in grazing grassland, but the effect was worse than that of BSM. Meanwhile, there were great differences in fitness among ONM, nichepredominance model (NPM) and random allocation model (RAM). Our results indicated that the application of multiple SDP models and verification methods would be beneficial to select the best model and better understand the ecological processes of grassland community under different utilization regimes.

Biomass allocation and allometry of wild and cultivated Gentiana rigescens Franch. ex Hemsl. (Gentianaceae).

ZHANG Ji, ZHAO Yan-li, WANG Yuan-zhong

2018, 37(12):  3584-3589. 

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Above and below-ground biomass allocation has implications for plant growth strategies. It is not clear whether below-ground biomass of herbaceous plants isometrically scales with above-ground biomass or not. Both nutrients and individual density may affect the biomass allocation in medicinal plants. Here, we compared the differences of aboveand below-ground biomass allocation between wild and cultivated Gentiana rigescens Franch. ex Hemsl. and analyzed the effects of cultivation duration and individual density on the biomass allocation of cultivated individuals. We found significant differences (P<0.05) in the allocation between the wild and cultivated plants, which might be influenced by soil nutrient level and plant competition. However, below-ground biomass isometrically scaled with above-ground biomass for both wild and cultivated plants. Density and its interaction with cultivation duration had significant effects on below-ground biomass (P<0.05). Further studies are needed to optimize the density and to clarify the effects of factors such as fertilization and soil microbes on the yield of medicinal use part (below-groundbiomass) of this species.

Biomass distribution and allometric model of two evergreen broad-leaved tree species in Shanghai.

LENG Han-bing, JING Jun, FENG Shu-cheng

2018, 37(12):  3590-3596. 

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We investigated main tree-measuring factors and the biomass of aboveground component of two major urban tree species, Cinnamomum camphoraand Magnolia grandiflora, in Shanghai by harvest method. We further analyzed biomass allocation patterns and explored optimal biomass allometric models and predictor variables by nonlinear equation. The results showed that: (1) The biomass of aboveground components of both species was characterized by stem>branch>leaf. Relative contributions of leaves, branches and stems to total aboveground biomass of C. camphoraand M. grandiflora were 17.88% vs. 27.31%, 30.48% vs. 27.93%, and 51.64% vs. 44.76%, respectively. There was no significant difference between leaves and branches for M. grandiflora. (2) Nine allometric models for biomass were developed based on three variables of diameter at breast height, tree height, and crown width. Results of fitness evaluations of the equations showed that model 8, model 3, model 4 and model 7 fit well to leaf, branch, stem, and total aboveground biomass for C. camphora, while model 4, model 9, model 2 and model 4 for M. grandiflor, respectively. Due to the difficulty of access to tree height and crown width, optimal models selected in application should meet both practical and accurate requirements on the basis of statistics and adaptation of models.

Effects of straw returning plus fertilization on crop yield and fertilizer use efficiency in rice-rapeseed rotation system.

YUAN Man-man, WU Gang, HU Run, GENG Wei, WANG Jia-biao, CAO Zhe-wei, SUN Yi-xiang

2018, 37(12):  3597-3604. 

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Rice-rapeseed rotation is one of the most important agricultural cultivation systems in China. Intensive farming in such systems would reduce soil fertility. Straw returning is one of the main ways to use straw in China. A field experiment was conducted to examine effects of straw returning plus fertilization on crop yield, nutrient accumulation, fertilizer use efficiency and nutrient balance in rice-rapeseed rotation. There were five treatments, including no nitrogen fertilizer and straw returning (CK), chemical fertilizer application without straw returning as farmer’s practice pattern (FPP) and three practices of fertilizer application mixed with rice straw returning of 3000 kg·hm^-2 (FS1, FS2 and FS3), in which nitrogen, phosphorus, and potassium fertilization levels were gradually increased from treatment FS1 to FS3. The results showed that yields of rice and rapeseed had similar patterns under different treatments of straw incorporation and fertilizer application, being SF3>SF2>SF1>FPP. However, there were no significant differences in rice and rapeseed yield between treatments SF2 and SF3. Compared with FPP, annual yield increased on average by 17.5%-28.6% under treatments of straw returning with increased fertilization levels, and the amount of nitrogen, phosphorus and potassium accumulated in rice and rapeseed increased with increasing fertilization level. Nitrogen, phosphorus and potassium accumulations in rice increased on average by 21.7%, 17.7% and 14.0%, and those in rapeseed increased by 22.4%, 19.6% and 51.8%, respectively. The enhancement of potassium accumulation in rapeseed was the highest due to returning straw and applying more potassium fertilizer. Under treatments of straw returning plus fertilization, nitrogen partial factor productivity (PFP_N) increased by 8.1% to 31.1% for rice and 4.2% to 29.3% for rapeseed respectively, compared with the treatment of FPP, similar to the results of nitrogen agronomic efficiency (NAE). SF2 had higher PFP_N and NAE, but lower phosphorus and potassium partial factor productivity.Results of nutrient balance calculation showed that phosphorus and potassium was deficient in rice, and was surplus and beyond the acceptable range in rapeseed under treatments of strawreturning with fertilizer applications. In the ricerapeseed rotation system, straw returning plus fertilizerapplication could improve crop yield, nutrient accumulation, and fertilizer use efficiency. However, the large amount of phosphorus and potassium fertilizer input and the nutrients from straw returning caused surplus of nutrients and decrease of fertilizer use efficiency. Therefore, it is necessary to further adjust the input amount of chemical fertilizer under straw returning to make more reasonable and sustainable nutrient recycle and use in crop production system.

Uniconazole spraying ameliorates salt injury to soybean seedlings by regulating anatomical structure in roots.

MENG Na, WEI Sheng-hua

2018, 37(12):  3605-3609. 

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We tested whether exogenous uniconazole (S₃₃₀₇) would ameliorate salt injury to soybean seedlings by regulating anatomical structure in roots, with Glycine max cultivar ‘Zhonghuang 13’ as the experimental material. The results showed that after spraying S₃₃₀₇ on salt-stressed soybean, the salt-induced declined parameters, including plant height, root length, dry and fresh weight of roots and shoots, relative growth rate, leaf area, and pith diameter, were markedly recovered, while the salt-induced ascended parameters, including Cl^- content, root/shoot ratio, cortex thickness and ray length, were decreased to levels between that in the control and the saltstressed seedlings. Partial deformation and invagination of salt-stressed epidermal cells recovered to the control level, with no tylosis being found in vessel elements. Spraying S₃₃₀₇ reduced the metabolic cost of roots by decreasing cortex thickness in roots, and shortened the distance of water absorption from root to vascular cylinder. Additionally, increased pith diameter was beneficial to nutrient storage, and reduced ray length shortened the lateral transport distance of nutrients in roots. Meanwhile, a significant reduction in Cl^- contents in roots and shoots could greatly relieve the chlorine toxicity to soybean seedlings under salt stress. In conclusion, S₃₃₀₇application could ameliorate salt injury by regulating anatomical structure in soybean roots.

The relationship between low temperature duration and growth recovery of rice during the vegetative growth stage.

TAO Le-yuan, LIU Zhi-lei, LIU Ting-ting, YU Cai-lian, WANG Wei, LI Yi, PENG Xian-long

2018, 37(12):  3610-3616. 

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Low temperature during vegetative stage would inhibit rice growth. It is still not clear whether such an inhibition is caused by direct action of low temperature or the result of prolonging growth period. Therefore, it is of great significance to answer this question for taking targeted measures to reduce damage induced by low temperature. Here, a water culture experiment was conducted with different low temperature durations (5, 10, 15 d at 15 ℃ and nitrogen application levels (40 and 80 mg·L^-1), to examine the changes of rice dry weight, nitrogen accumulation and growth period length. Results showed that low temperature inhibited the accumulation of dry weight and nitrogen. The longer low temperature lasted, the stronger impact it would have. When the temperature was recovered to normal level at the 10.5leaf age, the duration less than 5 d did not affect the growth period of rice, but theduration longer than 10 d delayed the growth period for 3-6 d. The dry matter weight could recover to normal level. Nitrogen application did not have significant effect on dry matter accumulation. When the duration was less than 5 d, nitrogen accumulation of the temperaturesensitive variety was 12.25% lower than that at the normal temperature, and nitrogen application could promote nitrogen uptake. However, the low temperature had limited effect on temperatureinsensitive varieties. Both the temperaturesensitive varieties and the insensitive ones could recover the nitrogen accumulation to normal level when the duration was longer than 10 d, and increased nitrogen application promoted nitrogen uptake significantly. Therefore, the effect of low temperature at vegetative stage on rice growth is mainly due to the delay of growth period. Resistant varieties with shorter growth period should be selected in practice, which has important significance in enhancing low temperature resistance of rice.

Effects of nitrogen application on the abundance and community of soil microbes in paddy field under the condition of no returning Chinese milk vetch.

NIE Jiang-wen, WANG You-juan, WU Bang-kui, LIU Zhang-yong, ZHU Bo

2018, 37(12):  3617-3624. 

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Understanding the impacts of long-term fertilization regimes on soil microbial ecology in paddy field can provide theoretical basis for optimal fertilization and farming. Here, an 8-year experiment was conducted to examine the effects of N application levels (N0, N100, N200) under the condition of no returning milk vetch in winter on the abundance and structure of soil microbial community during the flowering of milk vetch in a double cropping system in Hunan Province. Soil microbes were quantified using Illumina MiSeq high-throughput sequencing platform and fluorescence quantitative PCR technique. The results showed that soil pH, nitrate content and soil C/N ratio significantly decreased with increasing N application level under the condition of no returning milk vetch in winter. Moreover, N fertilization significantly increased the contents of total N, soil organic carbon and ammonium N in paddy soil. The microbial quantity in paddy field was 1.66×10⁸-1.23×10¹⁰ copies·g^-1 dry soil. N fertilization increased the 16S rDNA gene abundance, and the copy number of 16S rDNA gene in N0, N100 and N200 fertilization treatments was 1.0, 72.4 and 32.6 times of that in CK, respectively. The diversity index (Shannon index and Simpson index) and species richness index (Ace and Chao1) of the three N fertilization treatments were higher than those of CK, among which N200 had the highest diversity index and N100 hand the highest species richness. Three major taxonomic groups of 16S rDNA in different samples were Proteobacteria, Chloroflexi and Nitrospirae, which accounted for 33%-44.4%, 17%-22.3% and 9%-10% of the total OTU, respectively. The relative abundance of Proteobacteria and Nitrospirae in N0, N100 and N200 soil samples was lower than that of CK, while the relative abundance of Chloroflexia in N0, N100 and N200 was 1.2, 1.3 and 1.2 times of CK,respectively. Correlation analysis showed that the copy number of bacterial 16S rDNA gene was significantly correlated with soil organic carbon, total N and ammonium contents. There was a close correlation between soil bacterial groups and soil chemical properties. In conclusion, planting Chinese milk vetch in winter without returning to field and N fertilizer application significantly increased the yield of rice and the abundance of soil microbes in the flowering period of Chinese milk vetch, changed soil microbial community structure, and improved soil chemical properties, which is of guiding significance for planting green manure scientifically and reasonably in double cropping rice area of Hunan Province.

Spatiotemporal distribution of drought condition in different growth stages of sugarbeet in northern Xinjiang based on crop water deficit index.

KANG Li-juan, Batur Bake, XUE Ya-rong, WANG Meng-hui, LUO Na-na

2018, 37(12):  3625-3632. 

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Among many extreme climate events, drought is one of the most influential and most serious natural disasters, which affects the growth and development of crops and the formation of yield and thus seriously restricts the development of agricultural economy. We evaluated the drought condition during sugarbeet growth period in northern Xinjiang with the crop water deficit index as a drought index. Drought grade index of sugarbeet in northern Xinjiang was determined by selecting typical drought years and drought index in combination with drought data of Xinjiang over several decades. The spatial and temporal distribution of drought intensity, drought station ratio and drought frequency in different growth stages of sugarbeet in northern Xinjiang in the past 56 years were analyzed. The results showed that drought intensity and the ratio of dry stations in each growth stage of sugarbeet showed a significant downward trend. Among them, the ratio of severe drought stations substantially decreased, the ratio of extreme drought stations showed a trend of no significant decrease, the ratio of light drought stations showed a trend of no significant increase, while the ratio of nondrought stations showed a trend of significant increase. The occurrence frequency of extreme drought in the middle growth stage of sugarbeet was lower than that in the early and late growth stages, and the frequency of mild drought and severe drought was larger than that in early and later stages. The frequency of severe drought in the northern part of northern Xinjiang was higher than that in other regions in the early stage of sugarbeet growth, but it was lower in the later stage. The mild drought in the three stages of sugarbeet growth in most areas of northern Xinjiang occurred more frequently than other grades of drought.

The changes of leaf morphology and some enzyme activities of forage mulberry seedlings under flooding stress.

CUI Xue, RAO Liang-yi, ZHOU Qi-ling

2018, 37(12):  3633-3639. 

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Mulberry is one of the suitable species for vegetation restoration in the hydro-fluctuation belt due to its strong resistance of water-logging. To clarify the mechanism of forage mulberry to adapt to submergence in the water-level-fluctuating zone of the Three Gorges Reservoir area, a flooding simulating pot experiment was conducted to examine the changes of leaf morphology,activities of anaerobic respiration enzymes (PDC, ADH, LDH) and antioxidant enzymes (SOD, POD, CAT) in leaves of 2-year-old forage mulberry seedlings under different flooding time and depths. The results showed that the leaf damage degree in the root submergence group was not serious during flooding. While the leaves of deep submergence group appeared wilting and yellowing on the 15th day, the leaves were almost rotten and fall off after flooding. In the deep submergence group, new shoots could still sprout on the 75th day. The recovery growth of some plants in the root submergence group was fine. Under the same flooding time, the activities ofanaerobic respiration enzymes and antioxidant enzymes in leaves showed a significant rising trend with increasing flooding depth (P<0.05). The activity of SOD significantly increased on the 60th day of flooding, and decreased by 3.49% and 9.22% respectively in the control group and root submergence group on the 90th day, while the activity of POD and CAT reached the maximum level on the 90th day of flooding. Compared with the 30th day of flooding, the activities of both enzymes under three treatments on the 90th day of flooding significantly increased by 8.03%, 15.70%,10.23% and 12.05%, 6.45%, 9.15%, respectively (P<0.05). Our results indicate that mulberry seedlings responded to flooding stress through increasing the activities of anaerobic enzymes and antioxidant enzymes and coordinating the three antioxidant enzymes. In conclusion, forage mulberry seedlings have good adaptability to flooding stress and can be used for vegetation restoration in the water-level-fluctuating zone of the Three Gorges Reservoir area.

Variation of floral scent composition of Amomum villosum before and after pollination and its ecological significance.

ZHANG Ting, YANG Pei, GUO Yan-wei, ZHAO Rong-hua, PENG Yan-qiong

2018, 37(12):  3640-3646. 

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During the process of sexual reproduction of plants, volatile compounds emitted by flowers play an important role in attracting pollinators who prompt pollination and fertilization of flowers. Amomum villosum is one of the four most famous traditional medicines in south China. The low set rate is the bottleneck of production of A. villosum. Here, the head space dynamic method was used to collect the floral scents from A. villosum before and after pollination. The chemical compositions were analyzed and identified by gas chromatography and mass spectrometry (GC-MS). The results showed that total 22 volatile compounds were found from the floral scents before and after pollination, which were mainly classified into aliphatic, terpenoids and aromatic compounds. The components of volatiles obviously differed before and after pollination. Compared with floral scents before pollination, seven chemical compounds (isopropymyristate, diethyl phthalate, nonanal, bicyclogermacrene, 2,3-dihydro-4-methyl, α-farnesene and tridecane) disappeared, while γ-elemene, β-phellandrene, D-limonene, α-pinene and 2-undecanone compound decreased after pollination. Three chemical compounds \[2-cyclohexen-1-one, 2-methyl-5-(1-methylethenyl), 1,6-octadien-3-ol,3,7-dimethyl, and bicyclo \[3.1.0\] hexane 4-methylene-1-(1-methylethyl)\] newly appeared, and benzoic acid, hexyl ester, β-myrcene, butylated hydroxytoluene and undecane, 4,7dimethyl increased after pollination. These compounds with dramatical changes before and after pollination should be the main active compounds causing the pollinator’s behavioral response. The flowers of A. villosumreleased multiple chemical compounds with different component ratios to attract potential pollinators, which performed the chemical communication of “generalization” strategy. Furthermore, screening active compounds that can effectively attract pollinators may improve the pollination and seed production ofA. villosum.

The relationship between chlorophyll and leaf area, leaf thickness of Liguaria virgaurea under density-dependent condition in Gahai wetland.

LEI Lei, ZHAO Cheng-zhang, LI Xue-ping, REN Yue, ZHANG Jing

2018, 37(12):  3647-3653. 

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The relationships among leaf traits under different densities are important for understanding the relationship between the physical construction and physiological metabolism of plant leaves. We examined the relationship between chlorophyll content and leaf area, leaf thickness of Liguaria virgaureawith different population densities in Gahai alpine wetland. The L. virgaurea populations were divided into three densities: high (I, 171-240 bundles·m^-2), medium (II, 101-170 bundles·m^-2) and low (III, 30-100 bundles·m^-2). Three plots (1 m×1 m) were established for each density to investigate plant leaf traits. The estimation analysis of standardized major axis and Pearson correlation analysis were used to examine the allometric relationship between chlorophyll content and leaf area and thickness. The results showed that, with decreasing density of L. virgaurea population, density displayed a decrease-increase trend, vegetation coverage decreased, while plant height and soil moisture increased. Leaf area and chlorophyll content decreased gradually, and leaf thickness and specific photosynthetically active radiation inside the community decreased gradually. Moreover, leaf net photosynthetic rate and transpiration rate displayed a decrease-increase trend. Chlorophyll content was significantly negatively correlated with leaf area (P<0.05) but positively correlated with leaf thickness (P<0.05). Our results indicated that L. virgaurea growing in highdensity wetland has high chlorophyll content but small and thick leaves, whereas that growing in low-density wetland has low chlorophyll content but big and thin leaves. Our results reflect the adaptation of resource use strategies and photosynthetic product accumulation pattern of plants to the heterogeneity of environmental factors such as light conditions.

Effect of longitudinal gradient on riparian plant species diversity along the mainstream of Beijiang River.

ZHAO Qing-he, JI Xiao-yu, DING Sheng-yan, XU Shan-shan

2018, 37(12):  3654-3660. 

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Riparian ecosystem is the ecotone between aquatic ecosystem and terrestrial ecosystem. It harbors high biodiversity and provides numerous ecosystem services. In this study, we examined species composition and α, β, and γ diversities of plant communities in the riparian zonealong a longitudinal gradient of elevation from downstream to upstream of the Beijiang River. The results showed that: (1) A total of 136 plant species belonging to 116 genera and 59 families were recorded. Gramineae and Compositae were dominant families. Species composition differed among plots. Many species were found with low frequency, with 48.7%-71.4% of total species occurred only once, suggesting that riparian ecosystem maintained plant species diversity through harboring different species rather than high individuals of single species. (2) The α diversity first decreased and then increased along the longitudinal gradient, with higher values observed at plots located in high altitudinal riparian zone. (3) Plant species turnover presented intense fluctuation and discontinuity from low altitudinal to high altitudinal sites or from downstream to upstream, while the similarity of plant species consistently varied. This would be related to the specific characteristics of riparian zone in maintaining biodiversity and the relative heterogeneous distribution of plants species derived by human activities, topographic, and climatic factors. (4) The γ diversity along the longitudinal gradient showed a down-up trend, suggesting that the riparian γ diversity at regional scale was simultaneously influenced by many environmental gradients. The γ diversity of high altitude was higher than that of low altitude.

Correlation between vegetation community and soil physical-chemical factors in waterlevel fluctuation zone of Xiangxi River of the Three Gorges Reservoir area.

XU Jian-xia, WANG Jian-zhu

2018, 37(12):  3661-3669. 

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Soil environment is a key factor affecting plant community structure. To address the relationship between spatial distribution of plant community and soil environmental factors in water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir area, plant community characters of 30 sampling transects in the WLFZ of Xiangxi River were analyzed using cluster analysis. Redundancy analysis (RDA) was used to examine the roles of 11 soil physicochemical factors in driving the spatial distribution and diversity of vegetation. Clustering analysis showed that the herbaceous communities could be grouped into seven types in the Xiangxi River riparian zone dominated by annual plant communities. Results from correlation analysis of RDA and environmental factors revealed that the first axis of RDA was significantly correlated with soil water content (SWC), and significantly negatively correlated with elevation (P<0.01). The second axis was negatively related to soil pH, iron-bound phosphorus (Fe-P), soil organic matter (SOM) and organic/ortho P (O-P) (P<0.05). Correlation analysis between vegetation diversity index and soil physical-chemical properties revealed that there were significant correlations between species richness (R) and elevation, soil pH as well as SOM. Plant dominance index (D) was significantly negatively correlated with elevation (P<0.01), but significantly positively correlated with SWC. Shannon diversity index (H) was significantly positively correlated with elevation, SOM and total P (TP), but significantly negatively correlated with SWC and pH. There were no significant relationships between species evenness index (E) and other environmental factors except for elevation and SWC (P<0.05). Our results indicated that the main factors affecting the vegetation distribution in the WLFZ of Xiangxi River included elevation, SWC, SOM, soil pH, soil TP, and inorganic phosphorus (O-P and Fe-P).

Impacts of wintering water birds on the input of nitrogen and phosphorus in intermittent wetlands along Shengjin Lake.

GE Fang, HUANG Tao, ZHANG Ming-hen, WANG Xiao-ang, XU Zi-u, YU Chao

2018, 37(12):  3670-3675. 

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Due to the food shortage in Shengjin Lake, many wintering water birds would forage the adjacent intermittent wetland, such as paddy and water meadow. In order to understand the impacts of wintering water bird populations on the nutrient input to these intermittent wetlands, two paddies and one water meadow inhabited by wintering tundra swan and bean geese at the west Xiaolu mouth along Shengjin Lake were selected as our study object, with ditches as control (with same water source as paddy and water meadow). During the early, middle and late wintering season of 2016-2017, surface water samples and guanos from these wetlands were collected and analyzed for the concentrations of nitrogen and phosphorus. Meanwhile, the water bird populations were also monitored. The concentrations of total nitrogen (TN) and total phosphorus (TP) in waters from water meadow were significantly higher than those in the control, indicating intense impacts from bean geese populations. In early wintering season, the concentrations of TN and TP in waters from paddy 1 were significantly higher than those in the control, indicating intense impacts from tundra swan populations. In the middle and late wintering season, the concentrations of TN and TP in waters from paddy 1 and paddy 2 showed insignificant differences compared to the control, indicating weak impacts from water birds. Other forms of nitrogen and phosphorus in wetland water samples showed different variations, due to multiple influences such as water bird activities and guano decomposition. Our results indicate that nitrogen and phosphorus status in the intermittent shallow wetlands suffer different impacts from the habitation and feeding of wintering water birds.

Biodiversity pattern and species group classification of park birds along urbanization gradient in Shanghai.

LIU Na-na, SHOU Dan-yi, DA Liang-jun

2018, 37(12):  3676-3684. 

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Park green spaces are important habitats for birds in city. However, the effects of their surrounding environment on diversity and distribution of birds are not clear. In this study, the variations of avian diversity along urbanization gradient were investigated in 30 parks with similar acreage in Shanghai, by quantifying urbanization degree of the surrounding area of each park. The avian species groups were classified based on their distribution along urbanization gradients by indicator species analysis. The results showed that species richness, Shannon index and Pielou index of birds decreased with urbanization degree, with which richness and Shannon index significantly negatively correlated with the four selected variables indicating urbanization degree. The bird species in parks could be categorized into five groups, including urban dependent, urban adaptor, suburban adaptor, urban avoider and seasonal urban-rural migrant. Out of the 30 common species, seven and 15 species are suburban adaptor and urban avoider, respectively, indicating few species can adapt to urban environment and most of them occur in rural area to avoid urban environment. The ecological characteristic of birds responding to urbanization determines the avian biodiversity pattern along urbanization gradient.

The quantitative relationship between road traffic noise and retreat rate of thrush.

LIU Gang, LIU Fang-bo, LU Shi-wei

2018, 37(12):  3685-3690. 

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Road traffic noise forces wild birds to avoid the source of interference and to leave their original habitat. Understanding how the retreat behavior of birds quantitatively responds to the road traffic noise will provide theoretical basis for constructing the roads ecologically. By setting up retreat space in the laboratory and implementing a variable controlling approach to eliminate interference factors, we simulated road traffic noise in the wild with noise replay, examined its effects on retreat behavior of thrushes. Then, we analyzed the quantitative relationship between the distribution of thrushes in the retreat space and the sound pressure levels of noise. The results showed that: (1) Thrushes’ retreat behavior was affected by the road traffic noise. (2) There was no significant difference in the effect of traffic noise on the retreat rate between male and female individuals. (3) The relationship between thrush retreat rates (y) of thrushes and the sound pressure levels of noise (x) was well fitted as follows: y=0.071x-4.452.

Fish diversity change and fauna evolution in Jianhu Lake, Yunnan, China.

CHEN Guo-zhu, JIN Jin-jin, ZHANG Fang-fang, QIU Yu-ping, ZHANG Yun, LI Zhi-jun, LI Ze-hui

2018, 37(12):  3691-3700. 

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Fishes in Yunnan Jianhu Lake are important food sources for many migratory birds. Changes in fish species composition have significant impacts on structure and function of wetland ecosystems. In this study, we investigated fishes in Jianhu Lake to understand the composition of fish community and the homogenization of fish fauna between Jianhu Lake and its related areas. A total of 24 fish species were historically recorded in Jianhu Lake, including nine indigenous species and 15 alien species. 20 species still existed, and four indigenous species were functionally extinct. Eight alien species were recorded for the first time. It was confirmed that the endangered species Schizothorax yunnanensis was still distributed. Among all the alien species, 11 species were from the middle and lower reaches of the Yangtze River, accounting for 73.3% of the total; and 13 species originated from China, accounting for 86.7%. The genus and family diversity index (G-F) was 0.45 in the original indigenous community, but the current value was only 0.26, indicating that the fish community differentiation in the lake has changed from complex to simple with the invasion of exotic fish. The fish fauna similarity between Jianhu Lake and several adjacent plateau lakes has obviously increased. Moreover, the similarity of species composition between Jianhu Lake and main lakes in the middle and lower reaches of the Yangtze River has reached a significant level (P=0.05). The fish fauna in Jianhu Lake has evolved into one dominated by the main component of the river plain. Results from the individual ecology matrix analysis showed that the habitat requirements were similar between alien species and indigenous species, with strong competition.

Effects of temperature and individual density on resting metabolism rate of male Fejervarya multistriata.

QIN Jian-han, CHENG Bi-xia, XIE Hai, HOU Shao-bing, WU Zheng-jun

2018, 37(12):  3701-3705. 

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To examine the effects of temperature and individual density on resting metabolism rate of male Fejervarya multistriata, with open circuit instrument of animal respiration, we measured oxygen consumption of male F. multistriata under different ambient temperatures (15, 25 and 35 ℃) and individual densities (from 1 to 10) and calculated the resting metabolic rate. The results showed that body temperature significantly increased with increasing ambient temperature (F_2,27=16.958, P<0.01) and individual density (F_2,27=4.871, P=0.028). Under ambient temperature of 15 ℃ and 25 ℃, there were significant negative correlations between resting metabolic rate and individual density, with regression equations (15 ℃: RMR₁₅=-0.0078N+0.4001, R²=0.843, P<0.001) and (25 ℃: RMR₂₅=-0.0048N+0.9851, R²=0.941, P<0.001) respectively. However, under 35 ℃, there was a significant positive correlation between resting metabolic rate and individual density. The regression equation was (RMR₃₅=0.0551N+1.35, R²=0.855, P<0.001). Our results indicate that the males of F. multistriata can reduce energy metabolism through living in groups under low temperature. However, living in groups will increase energy metabolism of F. multistriata under high temperature, which is not conducive to the growth of F. multistriata.

Sulfate migration and transformation in relation to iron in acid mine drainage: A case study from the waste coal mine area, Zhijin County, Guizhou Province.

WANG Yue-zhu, ZHANG Rui-xue, WU Pan, XIA Yu, SONG Chuan-xiao, WU Yi-fan

2018, 37(12):  3706-3712. 

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Sulfate is the main component of acid mine drainage. High concentrationsulfate wastewater discharged into the environment can produce a series of pollution and ecological damages. We collected the water and sediment samples from a basin affected by acid mine drainage in a karst area of Zhijin County, Guizhou Province and investigated the migration and transformation of sulfate in the steam system. The results showed that water acidification in the study area occurred obviously. The dissolved form of sulfur in water was mainly SO₄^2-, which had obvious attenuation in the process of water migration. Meta-stable sulfur content was low in sediments, while the exchangeable sulfate (ExS) was the dominant sulfur forms, accounting for 65% of the total sulfur (TS). The content of reduced sulfur was very low in the strong oxidizing environment. The content of different forms of reduced sulfur was in order of elemental sulfur (ES) < acid volatile sulfide (AVS) < chromium reduction sulfide (CRS). SO₄^2- in water showed a positive relationship with Fe(Ⅲ). The co-precipitation of SO₄^2- and Fe(Ⅲ) into the sediment is the main cause for the reduction of SO₄^2-.

Impacts of cold-resistant mixed strains immobilized by different carrier materials on remediation of PAHs polluted soils.

GONG Chun-juan, SU Dan, WANG Xin, PU Yu, WANG Tian-jie

2018, 37(12):  3713-3720. 

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Removal of polycyclic aromatic hydrocarbons (PAHs) from soils can be enhanced by inoculation of cold-tolerant mixed strains (SDR4+JDR7) at low temperature. However, the inoculated strains would get lost rapidly, being poor repeatability. Microbial immobilization technique can overcome these drawbacks to some extent. With affinity to microorganisms, adsorption ability, and bioavailability of enriched contaminants as the three important factors for the selection of immobilization carriers, corn cob (Y), peanut shell (H), vermiculite (Z) and peat soil (N) were chosen as the carriers to adsorb and immobilize the mixed strains that are highly effective to degrade PAHs. Degradation of phenanthrene (Phe), pyrene (Pyr), and benzo(a)pyrene (BaP) in the contaminated soil was examined, and Michaelis-Menton and Mond kinetic models were applied to fit the degradation results. All the immobilized strains with the four carriers Y-(SDR4+JDR7), H-(SDR4+JDR7), Z-(SDR4+JDR7), N-(SDR4+JDR7)) had better remediation abilities than the free strains after 60 days. Among them, Z-(SDR4+JDR7) presented the best degradation abilities, with removals of Phe, Pyr and BaP being 64.38%, 48.71% and 40.19%, respectively; followed by Y-(SDR4+JDR7) with removals being 58.49%, 45.91% and 37.07%, respectively. The degradation rate of Phe by Y-(SDR4+JDR7) was the highest, which was 0.60 d^-1, 7.7% higher than that by the free strains. Z-(SDR4+JDR7) showed the highest degradation rates of Pyr and BaP, which were 0.54 and 0.20 d^-1, respectively, with 11.83% and 10.85% increases compared to the corresponding free-living bacteria. Z-(SDR4+JDR7) had the shortest half-life of the high-ring BaP degradation, which was 86.64 d. Our results can provide reference for remediation of PAHs contaminated soil in northern China with cold climate.

Priority area of biodiversity conservation in Southwest China.

SHI Xue-wei, ZHANG Lu, ZHANG Jing-jing, OUYANG Zhi-yun, XIAO Yi

2018, 37(12):  3721-3728. 

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The priority area assessment can determine the prioritization object through limited resources, so as to minimize biodiversity loss. Here, 831 key species in southwest of China were chosen as indicator species, to analyze spatial distribution patterns by using mechanism habitat model. Based on systematic conservation planning theory, the MARXAN tool was applied to identity the priority areas of southwest China. The results showed that the area of protection priority area is 89.88×10⁴ km², accounting for 37% of the research area. All species except birds in the prior conservation zone have a habitat area higher than 50% of their respective habitat area. 94% of the indicator species have a more than 60% of their respective habitat area. The GAP analysis indicates that the priority areas don’t match the distribution of national nature reserve in space. We suggest that current nature reserves should be expanded. A new nature conservation system should be properly established with the help of policies such as the construction of national parks.

Changes and driving forces of landscape pattern in southern Gurbantunggut Desert during 1998-2016.

JIANG Chao-liang, WU Ling, AN Jing

2018, 37(12):  3729-3735. 

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Based on the remote sensing data in 1998, 2007, and 2016, the spatiotemporal changes of land use and landscape pattern as well as the driving forces in southern Gurbantunggut Desert in recent 19 years were analyzed from the aspects of land use structure, changing speed, and landscape patterns using ArcGIS and Fragstats software. The results showed that: (1) The proportion of sand land was the largest, but its dominance decreased. The proportion of farmland/grassland and construction land increased, while that of water area decreased. The decrease rate of other unused land was the largest. (2) At the level of landscape patch, the fragmentation degree of the sand land and other unused land increased, and the farmland/grassland area was enlarged with a more complicated and irregular shape. (3) At the overall level of landscape, the number and density of landscape patch increased, the shape was more irregular and complicated, the contagion decreased, and the degree of separation and dispersion increased. The landscape patches tended to discretely and discontinuously distribute. (4) The changes of landscape pattern were influenced by both natural and human factors, with human activities being dominant. Our results revealed that human activities had a great impact on the landscape pattern evolution in the southern margin of the Gurbantunggut Desert, which has an important guiding significance for the protection and restoration of desert vegetation in the future.

Spatiotemporal distribution of urban heat island effect based on MODIS data in Chongqing, China.

PAN Ying, CUI Lin-lin, LIU Chang-mai, CHEN Long, ZHANG Ling-feng

2018, 37(12):  3736-3745. 

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With the rapid urbanization, urban heat island phenomena are increasingly obvious. Under the background of high temperature-induced disasters in Chongqing, thermal filed intensity and thermal field intensity index were extracted from MODIS data (2001-2016). Then, we analyzed the spatial and temporal dynamics of heat island effect and its influencing factors. The resultsshowed that the average annual temperature had substantially increased in the past 66 years. The area and intensity of urban heat island had ascended in the downtown of Chongqing from 2001 to 2016. Land surface temperature was positively correlated with the average annual temperature but negatively correlated with normalized difference vegetation index. Such a result indicates that the air was heated by underlying surface and vegetation could alleviate urban heat island effect. Land surface temperatures of urban land, water, and bare land were higher than that of other land types. Our results can provide effective information for urban planning and eco-city construction in Chongqing.

Controlling factors and spatial distribution of gross N transformation rate of global forest soils.

ZHAO Ting, ZHANG Jun-hui, WANG Fang, GENG Shi-cong

2018, 37(12):  3746-3756. 

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The total transformation rate of soil N and its relative strength determine N conservation and supply capacity of soils. Studies on the controlling factors of total N transformation rate of forest soils have great significance for understanding productivity, N cycling and environmental change of forest ecosystems. Here we conducted random forest model analysis upon 36 literatures of forest soil gross N transformation. We found that critical factors influencing the gross N mineralization rate were in order of TN> SNDPPT>MAT>WWP, the critical factors influencing the gross nitration rate were in order of TN>TC> SNDPPT>CEC, and the critical factors influencing the dissimilatory nitrate reduction to ammonium (DNRA) rate were in order of CLY>AWC>WWP>CEC. Then, a random forest model of total N transformation rate in forest soils was constructed and the spatial distribution of gross soil N mineralization rate, gross nitrification rate and DNRA rate were delivered. The results showed that the gross N mineralization rate ranged 1.672-64.016 mg N·kg^-1·d^-1, the gross nitration rate was 0.866-16.984 mg N·kg^-1·d^-1, and the DNRA rate was 0.030-2.045 mg N·kg^-1·d^-1. The gross transformation rate of soil N had substantial spatial heterogeneity. Specifically, these three transformation rates were very low in most parts of the world, and the spatial distribution of the maximum transformation rates overlapped in northwestern North America, northwestern Europe, and the Eurasian Continental junction.

The impacts of Cylindrospermopsis raciborskiiinvasion on community structure and species diversity of aquatic ecosystem.

LI Hong-min, SUN Jiong-ming, ZHANG Sha-sha, JIN Yan, XU Hang-zhou, PEI Hai-yan

2018, 37(12):  3757-3768. 

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Cylindrospermopsis raciborskii has gradually spread from the tropic and subtropic regions to temperate regions due to the global warming and water eutrophication. C. raciborskii can dominate in many water bodies and develop blooms, which has received widespread attention. The massive proliferation of C. raciborskii affects community structure and species diversity of local aquatic ecosystem and destroys the balance of ecosystem. Furthermore, the toxic metabolites released from C. raciborskii will pose severe threats to human and other animals via bioaccumulation and food chain transmission. In this review, we systematically evaluated the potential impacts of C. raciborskiiinvasion and proliferation on the community structure and species diversity of local aquatic ecosystems as well as the underlying mechanism. The impacts of C. raciborskii invasion on aquatic ecosystems not only depended on the characteristics of C. raciborskii strain and its invasive situations, but also were related to the environmental factors and species composition of local aquatic ecosystems. Therefore, ecological consequences of the same C. raciborskii species’s invasion can vary spatially and temporally. Under certain environmental conditions, C. raciborskii could affect species composition and biodiversity of native aquatic ecosystems mainly through its strong interspecific competition, ecotoxicity to other aquatic organisms as well as its regulation to aquatic bacterial communities. Finally, future studies were prospected in allusion to some hotspot problems, such as the ecological consequences of invasion, the biotic interactions and the effective prevention and control, which would provide a theoretical basis for comprehensively understanding the impacts of invasion on aquatic ecosystems.

A review of soil mass cracks characteristics and their eco-environmental effects in coal mining area.

LI Ye-xin, WANG Dao-han, Lü Gang, DIAO Li-fu, DONG Liang, DU Xin-peng

2018, 37(12):  3769-3779. 

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Soil mass cracks caused by coal resource exploitation are the most intuitive, widely distributed, and harmful geological disasters. They could destroy the continuity of land, threaten the mine geological environment, and lead to productivity reduction and water pollution. Moreover, they may also threaten the safety of mine electrical and mechanical facilities and workers. We reviewed recent research progress of soil mass cracks in formation mechanism and evolution pattern, shape characteristics and influencing factors, determination methods and eco-environmental effects in coal mining area. The shape characteristics of soil mass cracks in coal mining area should be further studied, the preferential flow effect and its contribution rate of soil mass cracks should be revealed by field study and laboratory simulation. Furthermore, the characteristics of soil mass cracks in dumping sites and its quantitative effects on slope stability should be clarified.

Discrimination of “secondary invasion” and plant secondary invasion.

XU Guang-yao, LI Hong-yuan, MENG Wei-qing, MO Xun-qiang

2018, 37(12):  3780-3786. 

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Plant secondary invasion reduces the efficiency of invasive plants controlling and hinders the restoration of invaded ecosystems. Studies on plant secondary invasion are still rare in China, so it is urgent to strengthen international communications and learn from foreign experience. The English term “secondary invasion” is highly inconsistent, which brings obstacles for scientific communication. In this review, different definitions of “secondary invasion” were sorted out and discriminated, and the mechanisms of secondary invasion were summarized. Four common definitions of “secondary invasion” mainly include secondary expansion, secondary diffusion, inducing invasion, and secondary invasion. Provenance effect, control sideeffect, legacy effect, and global climate change are the mechanisms underlying secondary invasion. In the future, more comprehensive control strategies are needed, that is, it should simultaneously suppress the possible secondary invasive plants and strive to alleviate the legacy effects of the target plants, and add local plants to improve system resilience and inhibit secondary invasion.

Plant economics and non-economics spectra in relation to litter decomposition: A review.

ZHANG Hai-yan, GUO Xiao-cheng, KONG De-liang

2018, 37(12):  3787-3794. 

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Terrestrial plants have evolved an important functional trait spectrum, i.e., plant economics spectrum, which reflects the costbenefit tradeoff in resource acquisition. The plant economics spectrum was initially found in organs of mature plants. In recent years, mounting studies focus on the relationship between plant economics spectrum and litter decomposition. While there is a significant relationship between plant economics spectrum and litter decomposition, the strength of such correlation varies greatly across different studies. Such variations have been seldom addressed. Some trait spectra, e.g., hydraulics spectrum and chemical defense spectrum, are independent of plant economics spectrum, and are defined here as the non-economics spectrum. We reviewed the relationship between plant economics spectrum and litter decomposition. Furthermore, we proposed the view of non-economics spectrum from which we can understand the differences of different empirical studies in the strength of correlation between plant economics spectrum and litter decomposition rate. Then, we explored the potential ways by which non-economics spectra would affect litter decomposition, and consequently the relationship between plant economics spectrum and litter decomposition. In addition, we compared the difference between roots and leaves in terms of the relationships of abovementioned spectra with litter decomposition. Finally, several promising fields were proposed for future studies that aim to examine the role of non-economics spectra in accounting for the difference of the correlations between plant economics spectrum and litter decomposition among different studies.

The application of ultrasonic telemetry in the study of spawning ground of Eriocheir sinensis.

GENG Zhi, FENG Guang-peng, ZHAO Feng, ZHANG Tao, YANG Gang, ZHUANG Ping

2018, 37(12):  3795-3801. 

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Based on an external fixation method of the ultrasonic transmitter, we investigated the horizontal and vertical activities of gravid Eriocheir sinensis by the ultrasonic telemetry. There was no significant effects of external fixation of ultrasonic transmitters on the death rates of mitten crabs (P<0.05). A total of 14 tagged mitten crabs being gravid were released in December 2014, and 10, 12, 13, 9, 9, 9, 9, 6, 4, and 2 tagged crabs were tracked from late December 2014 to early May 2015, respectively. The tagged crabs were mainly distributed near north and south dams of the deepwater channel, with a trend of moving eastward. The presence frequency of tagged crabs in the midstream of the deepwater channel was greater than that in the downstream in January (P<0.05) and was greater in the downstream than in the midstream in April (P<0.05). There was significant difference between habitat depth in different months (P<0.01). The tagged crabs migrated from habitats with depth 8.25±3.35 m to that with depth 11.10±2.64 m from early January to early February, mainly inhabited in the area with depth 6.35 m from late February to early April, and inhabited in waters with depth 9.89±2.59 m in late April. Our results provide technical support for studying ecological habits and habitat locating of aquatic animals.

Extracting temporal and spatial distribution features of Lake Taihu from MODIS-EVI data by empirical orthogonal function analysis.

ZHANG Heng-gan, GU Ke-jun, ZHANG Si-mei

2018, 37(12):  3802-3808. 

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Lake Taihu is the second largest lake in China, providing much of the irrigation and domestic water in the plains of the middle and lower reaches of the Yangtze River. However, cyanobacteria blooms in this lake have occurred frequently and seriously in recent years, which make harmful to local residents. To solve the problem, researchers have taken efforts to understand its external performance and internal reasons, including the spatiotemporal distribution. Due to the lack of continuous, regular, and longterm observation data, the knowledge is rather scarce. Here, a spatiotemporal MODIS-EVI dataset from 2000-2016 was constructed with MOD13Q1 (one of MODIS products) as data source, followed by the empirical orthogonal function (EOF) analysis and corresponding time coefficients calculations. After North test, the first four EOFs were chosen for further time series analysis, the time coefficients of which were decomposed by classical seasonal decomposition method. The first four EOFs accounted for 46% of the total variance (21.3%, 4.9%, 4.7% and 2.7% for EOF1 to EOF4 respectively), and their spatial patterns matched well with results in previous literatures, but being more accurate, robust and simple. In the time dimension, the trend and seasonal components of time series of the four EOFs had different patterns, which could be used to discriminate the sources of variation of EOF. Our results indicate that EOF method is suitable for extracting the spatiotemporal distribution of EVI in Lake Taihu.

Measurement and spatial heterogeneity of land use eco0efficiency and the optimal allocation of land resources.

HUANG Xin, CHENG Wen-shi, JIAO Li-min

2018, 37(12):  3809-3816. 

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The eco-efficiency of land use reflects the ecological impacts produced by economic activities of land use, which is a critical factor to monitor economic development and to achieve the control of ecological cost. On the basis of defining the connotation of the eco-efficiency of land use, we examined the efficiency situation, spatial differentiation, availability of resource allocation and output efficiency of 31 provincial administrative units in China in 2005, 2010, and 2015, based on C₂R model of data envelopment analysis, spatial statistics analysis and grey target model. The results showed that the eco-efficiency of land use was generally low except Tibet Autonomous Region. The spatial distribution was basically high in the west and north and low in the east and south. There was a significant spatial autocorrelation of eco-efficiency of land use at the provincial level, with an obvious change in partial places. The northwestern part had high-high cluster, and a lowlow cluster was mainly distributed in southeast coasts of Guangdong and Fujian. The availability of resource allocation in the east part was lower than that in the west part, indicating an obvious input surplus in the east part. The output efficiency was significantlyincreased in China from 2005 to 2015, and the regions with low values were clustered to the radiating regions of BeijingTianjin-Hebei, Yangtze River Delta and Pearl River Delta as cores.