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    10 June 2014, Volume 33 Issue 6
    Geographic distribution of Larix gmelinii natural forest in China and its climatic suitability.
    YANG Zhi-xiang1,3, ZHOU Guang-sheng1,2**, YIN Xiao-jie1,3, JIA Bing-rui1
    2014, 33(6):  1429-1436. 
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    It is necessary to accurately assess the geographic distribution of Larix gmelinii natural forest and its climatic suitability for forest management. There were eight potential climatic factors influencing L. gmelinii forest’s geographic distribution, including mean temperature of the coldest month (Tc), mean temperature of the warmest month (Tw), annual range of monthly mean temperature (DTY), accumulated temperature no less than 5 ℃ (GDD5), annual precipitation (P), precipitation in autumn and winter (Pa&w), moisture index (MI) and solar radiation(RAD). We confirmed the dominant climatic factors using the MaxEnt model and Jackknife analysis method. The results showed that Tc, DTY, RAD and GDD5 were the dominant climatic factors for the distribution of L. gmelinii natural forest, and the cumulative contribution rate of these factors reached 87.8%. This indicated that thermal factors (temperature and solar radiation) were the key factors rather than water conditions. The relationship between the distribution of L. gmelinii forest and the dominant climatic factors was developed by the MaxEnt model, whose accuracy reached the “excellent” level with an AUC value of 0.956. Furthermore, the distribution of L. gmelinii natural forest in China mainly located in low and moderate climatic suitability zones. The thresholds of the four dominant climatic factors were given by their relationship with the geographic distribution probability of L. gmelinii, i.e., -28.8 ℃≤Tc ≤-19.5 ℃; 39.0 ℃≤DTY≤46.2 ℃; 2871.7 MJ·m-2≤RAD≤3519.8 MJ·m-2; 1000.0 ℃·d≤GDD5≤ 2100.0 ℃·d.
    Biomass allocation characteristics of the main forest ecosystems in the Great Xing’an Mountains, Heilongjiang Province.
    WANG Xiao-li1,2,3, CHANG Yu1**, CHEN Hong-wei1, HU Yuan-man1, FENG Yu-ting4, WU Wen1,3, JIAO Lin-lin1,3
    2014, 33(6):  1437-1444. 
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    The Great Xing’an Mountains is one of the most important regions with abundant forest resources. Its large amounts of forest biomass and carbon stocks have significant implications for maintaining the carbon balance of Northeast China. Based on field investigation data, the forest biomass and its allocation characteristics as well as the quantitative relationships among biomass of each component of forest ecosystems at the stand level in the Great Xing’an Mountains were analyzed. Furthermore, the plots surveyed were divided into seven community types by ordination axes clustering analysis with the software of CANOCO 4.5 on species composition, and the biomass allocation characteristics of each of the community types and the relationship with environmental factors were elucidated. The results showed that the total forest biomass in the Great Xing’an Mountains ranged from 17.83 to 283.93 t·hm-2, and the average biomass density of each vegetation type was in the order of Quercus mongolica forest > larch forest > Pinus sylvestris var. mongolica forest. Compared with Q. mongolica forest, the percentage of underground biomass or litter biomass in coniferous forests was larger. Meantime, the differences of geographical distribution of plant community as well as biomass allocation characteristics were obvious along the elevation gradient.
    Short- and long-term effects of fire on soil properties in a Dahurian larch forest in Great Xing’an Mountains.
    KONG Jian-jian1,2,3, YANG Jian1**
    2014, 33(6):  1445-1450. 
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    Wildfire is an important component in boreal forest ecosystems, and accelerates biogeochemical processes of forest ecosystems. In this study, we investigated the shortterm and long-term effects of wildfire on soil physicochemical and microbial indicators in boreal Dahurian larch forests that were burned respectively in 2010 and 2000 at the Huzhong Natural Reserve in the Great Xing’an Mountains. Our results showed that wildfire significantly decreased soil moisture, organic matter depth, soil C/N and microbial biomass in the plots burning in 2010, but significantly increased soil pH, ammonium and nitrate contents, compared with the control plots. However, 11 years after the wildfire, no significant differences were observed in these soil properties between burned and control plots except for soil microbial biomass, which was significantly lower than the control. This suggests that postfire soil physicochemical properties can rapidly recover to prefire levels, but the effect of fire on soil microbial biomass may last for a long time. This research provided a basis for managing the nutrients of postfire Dahurian larch forests.
    Rainfall redistribution by crown layer and variation characteristics of nitrogen and phosphorus in Pinus massoniana plantations.
    ZHANG Jie, LIU Yang, ZHANG Jian**, OU Jiang, CUI Ning-jie
    2014, 33(6):  1451-1458. 
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    In order to investigate the distribution of precipitation and nitrogen, phosphorus characteristics by canopy interception of Pinus massoniana plantations, the rainfall, throughfall, stemflow and their nitrate (NO3-), ammonium (NH4+) and total phosphorus (TP) concentrations were measured in 18 and 32 years old Pinus massoniana plantations at Laifu Town of Yibin City. The results showed that, according to the variations of monthly precipitation, the rain and dry seasons could be defined as from July to November and from January to April, respectively. Canopy interception and nitrogen, phosphorus concentrations were influenced by the rainfall class. Rainfall, interception of throughfall and stemflow were positively correlated with the rainfall class, and the interception in the dry season was less than in the rain season. The monthly average concentrations of TP, NO3--N, NH4+-N in the dry season were significantly higher than in the rain season, and there were significant differences between months, whereas there were no significant differences in canopy interception of TN and TP concentrations between the two plantations. The result indicated that there were significant negative correlations between nitrogen and phosphorus concentrations with rainfall, throughfall and stemflow, and the nitrogen and phosphorus concentrations declined significantly with increasing the rainfall.
     
    Correlation of leaf lifespan of major evergreen trees with herbivory frequency in Baohuashan, Jiangsu Province. 
    WANG Rui-xue, ZHANG Guang-fu**, SUN Jing-jing
    2014, 33(6):  1459-1466. 
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    The study of correlation between leaf lifespan and herbivory plays a significant role in reflecting their life history features and ecological adaptive mechanisms. The methods of static life table and field observation were applied to analyze the leaf lifespan and herbivory frequency of five major evergreen broad-leaved species sampled from Baohuashan Nation Forest Park, Jiangsu Province; meanwhile their leaf traits were also measured indoors. The results were as follows: 1) The leaf lifespan of the five species was different (P<0.05), varying from 1.26 to 2.47 years with an average of 1.80 years. 2) The herbivory frequencies of the five species were different, with an average of 34.74%. Moreover, for each species, the herbivory frequencies of extant leaves on one branch increased with increasing the leaf age class. 3) There was a significant positive correlation between the herbivory frequency and the leaf lifespan (P<0.05). Significant correlations were found between leaf toughness, thickness, water content and LMA (leaf mass per area). Principal component analysis on those leaf traits showed that the first principal component could explain 92.57% of the total variance. Furthermore, the herbivory frequency had a significant negative correlation with the first component (P<0.05). Therefore, it is concluded that the longer the leaf lifespan, the higher the herbivory frequency for woody evergreen species in evergreen and deciduous broadleaved mixed forests in subtropics, and that the herbivory frequency is not only correlated with abundances of tree species, but also with a range of leaf traits (rather than a single one).
    Relationship of leaf shape change and leaf nutrient contents in Populus euphratica.
    FENG Mei, HUANG Wen-juan, LI Zhi-jun**
    2014, 33(6):  1467-1473. 
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    Through field observation and laboratory analysis, this study investigated the leaf growing pattern in Populus euphratica and its relationship with developmental stages and leaf nutrient contents. The results showed that the individual leaf index (leaf length/width ratio) had a significant negative correlation (P<0.01) with DBH (diameter at breast height), tree height and leaf area. Leaf shape index decreased with the increase of canopy level at all development stages, and decreased with the increase of number of minor branch nodes at different canopy levels of the same individuals. The total N, P and organic C contents of individual leaf were positively correlated with tree height and DBH; total K content had a significant negative correlation with tree height and DBH (P<0.01); leaf index had a significant negative correlation with the total P content (P<0.05) and a significant positive correlation with the total K content (P<0.01). These results suggested that leaf index in P. euphratica changed not only at different developmental stages, but also at different levels of the same canopy and at different nodes of the branches. Total N, P, K and organic C contents of the leaves mainly changed at different developmental stages. With the increase of DBH, leaf index decrease and leaf area increase, the total P, K contents of the leaves have an increase trend.
    Short-term effects of pruning on stem surface and soil CO2 effluxes in a Chinese fir plantation.
    LIU Lan-lan1,2,3, WANG Si-long1,2**, YANG Qing-peng1,2
    2014, 33(6):  1474-1479. 
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    Carbon dioxide releases from stem surface and soil are important parts of forest ecosystem carbon cycle, but how pruning treatment impacts stem surface and soil CO2 effluxes is unclear. In this paper, we examined the effect of photosynthate supply on stem surface and soil CO2 effluxes in a Chinese fir plantation forest by pruning branches (CK, light pruning, and heavy pruning). Stem surface and soil CO2 effluxes were measured with the LI-6400-09 portable photosynthesis system for a month. The results showed that pruning had no significant effect on stem surface CO2 efflux, although the maximum sap flow velocity decreased slightly. Pruning treatment decreased soil CO2 efflux slightly, with reductions by 11.8% and 17.9% for light and heavy pruning treatments, respectively compared to the control. However, there was no significant difference among the three treatments. Our results indicated that shortterm effects of pruning on stem surface and soil CO2 effluxes were negligible in the Chinese fir plantation forest.
    Effects of simulated nitrogen deposition on soil active organic carbon in poplar plantations along Northern Jiangsu coast.
    XU Kai1, XU Yu1, ZHANG Meng-shan1, XU Chang-bai2, CAO Guo-hua2, GE Zhi-wei1**, RUAN Hong-hua1
    2014, 33(6):  1480-1486. 
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    The impacts of nitrogen deposition on soil labile carbon at different age poplar plantations were examined in this study. Beginning in May 2012, we conducted a field experiment to simulate nitrogen deposition with five treatments at Dongtai Forest Farm in Jiangsu Province. In June 2013, the soil samples were taken to analyze the variations of soil labile organic carbon. The results indicated that soil microbial biomass carbon decreased after an initial increase with the increasing nitrogen level in the 5 and 9 years old poplar plantations, and increased with the increased nitrogen level in the 15 years old poplar plantation. Increasing the level of nitrogen enhanced the content of soil dissolved organic carbon in all poplar plantations. There was a significant correlation between the soil MBC and DOC. Furthermore, the soil MBC and DOC were significantly correlated with the soil TN, MBN, DON, NH4+-N, NO3--N. Our results imply that nitrogen deposition might enhance the content of soil labile organic carbon, and thus affect the dynamics of soil organic carbon in the poplar plantations.
    Effects of artificial vegetation types on soil quality in loess hilly area in Northern Shanxi Province.
    WANG Gai-ling1**, WANG Qing-chu2
    2014, 33(6):  1487-1491. 
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    Based on the runoff plots located in Yanggao County, Shanxi Province, the effects of different vegetation types, including bare land, wasteland, Caragana korshinskii, Hippophae rhamnoides, Pinus tabuliformis and Medicago sativa, on soil quality in loess hilly area in North Shanxi Province were assessed by principal component analysis. The results showed that eight soil physicochemical indicators (soil texture, porosity, capillary porosity, organic matter, total nitrogen, alkalihydrolysis nitrogen, available phosphorus and available potassium) could be represented by three common types of soil quality factors, which were organic matter factor, soil texture factor and pore factor. The scores of both the organic matter factor and pore factor under the four artificial vegetation types were all higher than in the wasteland. Except for M. sativa, soil texture factor scores under the artificial vegetation were also higher than in the wasteland. Scores of all three common quality indicators in the bare land were the lowest. Soil integrated assessment scores for M. sativa, C. korshinski, H. rhamnoides, P. tabuliformis, wasteland, and bare land were 0.596, 0.584, 0.495, 0.481, 0.305, and 0.194, respectively. This meant that the four types of artificial vegetation could improve soil quality and M. sativa and C. korshinskii were more effective than others. Bare land led to soil degradation.
     
    Effects of Flaveria bidentis invasion on soil ammonia-oxidizing bacterial community structure and diversity.
    ZHAO Xiao-hong1,2, YANG Dian-lin2, QU Bo1, WANG Hui2, LIU Hong-mei2, LAI Xin2, HUANGFU Chao-he2**
    2014, 33(6):  1492-1500. 
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    Invasive plants usually change invaded soil microbial communities which have an important regulatory role in soil nutrient cycling and interspecies competition. Thus, it is important to investigate the effect of invasive plants on native soil microbial communities so as to assess their effect on native ecosystems and the microbial mechanisms involved. In this study, the effect of Flaveria bidentis, an invasive plant, on soil ammonia-oxidizing bacteria (AOB) community was investigated by using polymerase chain reactiondenaturing gradient gel electrophoresis (PCRDGGE). The results showed that most identified AOB were Nitrosospira sp., Nitrosation vibrio, uncultured Nitrosomonas and uncultured AOB in the studied soils, with the domination of Nitrosospira and uncultured AOB. The Shannon indexes of AOB were in order of invaded rhizosphere soil > non-invaded soil > invaded bulk soil, and the soil potential nitrification rate followed the same pattern. Also, both nitrate and ammonium nitrogen contents were correlated closely with the Shannon index. It was concluded that AOB community diversity was reduced following the invasion of F. bidentis with the rhizosphere effect detected, suggesting that F. bidentis might promote its spreading by boosting N-cycling in rhizosphere in the invasion process.
    Joint effects of galaxolide and cadmium on actinomycetes quantities in soils.
    LU Ze1,2, HU Xiao-min1**, AN Jing2, WEI Wei3
    2014, 33(6):  1501-1507. 
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    HHCB is one of the most significant PPCPs pollutants concerned by environmental scientists. Meanwhile, Cd is one of the most important heavy metal pollutants existing widely in environment. Combined exposure of HHCB and Cd is possible in the soil ecosystem. However, few studies have been reported regarding the impacts of joint pollution of these two pollutants on soil microbes. In this paper, the joint toxic effects of HHCB and Cd on actinomycetes were studied using soil microcosm for a 10 week duration. Results showed that single and joint effects of HHCB and Cd on actinomycetes quantities in soils were markedly significant (P<0.01). The inhibitory effect of actinomycetes quantities in soils increased with the increase of HHCB concentration under both single and combined treatments of HHCB and Cd. The doseeffect relationship between HHCB and the inhibitory rate of actinomycetes quantity in soils was logarithmic. The EC50 value was the least in the 3rd week after treatment.  In the first 5 weeks of incubation, the EC50 values were not more than 10 mg·kg-1. It was suggested the joint effects of HHCB and Cd were antagonistic. It could be concluded that the input characteristics of HHCB to soils should be considered for selecting a suitable EC50 value for assessing its ecological risks in soils.
     
    Effects of plant community composition on microbial community in constructed wetlands.
    LI Xin, DU Li-ping, XU Ting-ting, ZHANG Lin-lin, YING Jie, ZHANG Chong-bang**
    2014, 33(6):  1508-1514. 
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    Aquatic plant species greatly differ in the capacities to excrete oxygen and execute organic compounds into the rhizosphere environment. Accordingly, the difference in plant species and community composition may affect microbial community differently. In order to test this hypothesis mentioned above, the current study established five plant species richness levels (0, 1, 2, 3 and 4 species/microcosm unit) in vertical flow microcosm wetlands using a completely random block design, and irrigated the microcosms with Hoagland inorganic nutrient solution. The results showed that the microcosms monocultured with Rumex japonicus or Oenanthe hookeri showed a greater capacity of microbial communities to utilize amines/amides or miscellaneous compounds than the microcosms monocultured with Phalaris arundinacea or Reineckia carnea. Plant species richness not only increased microbial biomass carbon and nitrogen as well as dehydrogenase activity in the microcosms, but also enhanced the capacities of microbial communities to utilize carbohydrates and amino acids. Furthermore, the presence or absence of O. hookeri, P. arundinacea or R. carnea within a given plant community affected the capacity of microbial communities to utilize carbohydrate, miscellaneous and amines/amides.
     
    Effects of water quality and substrate type on seed germination of Vallisneria spiralis L.
    HAN Cui-min1, HU Geng1, WU Tao1, YOU Wen-hua2**
    2014, 33(6):  1515-1519. 
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    The effects of water quality and substrate type on the seed germination of Vallisneria spiralis L. were investigated, with the goal to explore its strategies of seed germination under eutrophic water condition. The results showed that the seed germination percentage of V. spiralis was 40%-69% under natural temperature and light conditions. Water bodies had little effect on the seed germination of V. spiralis. However, compared to the other two waters, the cumulative germination percentage and total germination percentage were relatively higher, the germination rate was faster and the mean germination time was shorter in the water of Taihu. Substrate types significantly affected the seed germination of V. spiralis, which was the best in the loess and the worst in the sand. In the substrate of loess, the total germination percentage was 20% higher, the germination rate doubled, and the mean germination time was 11 days shorter than those in the sand. The seed germination percentage in the water (64%) was greatly higher than in the sediment (50%), while the seed germination efficiency was significantly lower in the water than in the sediment (germination rate 5% lower and mean germination time 11 days longer). This study provides a theoretical basis for vegetation restoration in eutrophic lakes using the V. spiralis seeds.
    Effects of elevated atmospheric CO2 on photosynthesis of Gracilaria lemaneiformis and Ulva conglobata grown at low and high N supplies.
    DENG Ya-yun1,2, ZOU Ding-hui1,2**
    2014, 33(6):  1520-1527. 
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    This study adopted two species of marine macroalgae, Gracilaria lemaneiformis and Ulva conglobata as experimental materials, which were cultured under outdoor conditions. The treatments were designated as ambient (390 μL·L-1) and elevated (800 μL·L-1) CO2 concentrations, and low (10 μmol·L-1) and high N (150 μmol·L-1) availability, in order to examine the effects of elevated CO2 on growth and photosynthesis in marine macroalgae grown at different N supplies. During the cultivation, the biomass of the algae was measured. After culture for 18 days, the photosynthesis was examined with seawater in equilibrium with ambient (390 μL·L-1) air and CO2enriched (800 μL·L-1) air, respectively. The results showed that elevated CO2  significantly enhanced the relative growth rate (RGR) in both the macroalgal species regardless of the N levels in culture. However, the enhancement of growth was more pronounced in G. lemaneiformis, but less pronounced in U. conglobata, under low than high N conditions. Shortterm exposure to CO2 enrichment stimulated photosynthesis of both the macroalgal species. Such stimulation of photosynthesis in G. lemaneiformis could be fully remained with prolonged growth with enrichedCO2. However, long-term growth condition of CO2 enrichment had an inhibitory effect on photosynthesis in U. conglobata. Additionally, the enriched N supply significantly increased photosynthesis and respiration in both the macroalgal species, regardless of the CO2 concentration in culture.
    Photosynthetic capacity of three common species of macroalgae and the application in coral aquarium.
    YANG Xiao-zhou1,2, ZHENG Xin-qing1**, LIN Rong-cheng1, HUANG Ding-yong1, SHI Xiao-feng1, NIU Wen-tao1
    2014, 33(6):  1528-1533. 
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    This study investigated the difference of photosynthetic capacity in three macroalgae species (Ulva lactuca, Enteromorpha clathrata, and Caulerpa mexicana) commonly used for nutrient removal in coral aquariums. The photochemical efficiency (Fv/Fm), parameters relevant to rapid light curve (RLC) and nonphotochemical quenching (NPQ) in the macroalgae were measured by underwater saturation pulse modulated chlorophyll fluorometer (Diving-PAM). The results showed that Fv/Fm was 0.808±0.004 for U. lactuca and 0.816±0.009 for E. clathrata, which were higher than that for C. mexicana. Higher maximum relative electron transfer rates (rETRmax) (17.52±2.92 and 19.59±4.43 μmol e·m-2·s-1) and halfstarved value of light intensities (Ik) (53.41±8.18 and 59.71±13.52 μmol photons·m-2·s-1) were observed in U. lactuca and E. clathrata than that in C. mexicana (13.72±5.41 μmol e·m-2·s-1 for rETRmax and 32.67±14.06 μmol photons·m-2·s-1 for Ik), indicating that U. lactuca and E. clathrata have stronger photosynthetic capacities, photoprotection capacities and tolerance to higher intense light than C. mexicana. A significantly lower RLC initial slope α in C. mexicana implied that this algal species has a higher photosynthetic capacity under weak light condition. With increasing the light intensity (0-373 μmol photons·m-2·s-1), however, C. mexicana had a limited increase of NPQ (0-0.2), the maximum of which was equivalent to 38.1% of that in U. lactuca and 62.5% of that in E. clathrata. These results indicate that the photosynthesis of E. clathrata may be more easily limited by intense light. Our study suggests that the selection of algal species for nutrient removal in a coral aquarium should be adapted to the light intensity. Single species or the combination of different species of macroalgae can be selected according to the illumination of the coral aquarium in order to maximize the efficiency of nutrient removal.
    Food web structure of the East Lake Taihu by analysis of stable carbon and nitrogen isotopes.
    LI Yun-kai1,2,3**,GONG Yi1
    2014, 33(6):  1534-1538. 
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    Stable isotope analysis is an effective tool in studying mass and energy dynamics in aquatic ecosystem. Stable carbon isotope ratios (δ13C) are commonly used to trace consumers’ forging location; while stable nitrogen isotope ratios (δ15N) are used to estimate the trophic position of organism in the ecosystem. In this study, the food web of East Lake Taihu was constructed using stable isotope analysis with the aim of quantifying the trophic relationships among species and providing policy-makers scientific information for ecosystem-based management in Lake Taihu. Results showed that two trophic pathways were found in East Lake Taihu: the planktonic pathway and the littoralbenthic pathway, with phytoplankton and macrophytes as their carbon sources, respectively. The littoral-benthic pathway supports most of the fish populations. The top predators, carnivorous fishes such as culters, mandarin fish and catfish, dominate the highest trophic level.
    Toxic effect of \[OMIm\]Br on Chlorella pyrenoidosa.
    YANG Zhao-ren, ZHOU Zuo-ming**
    2014, 33(6):  1539-1545. 
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    The toxicity of 1-octyl-3-methyimidazolium bromide (\[OMIm\]Br) ionic liquid on Chlorella pyrenoidosa was investigated by acute toxicity tests The results showed that under \[OMIm\] Br stress for 96 h, algal biomass (algal cell density, chlorophyll and protein contents) changed with the \[OMIm\]Br dosage in a positive correlation. The concentration for 50% of maximal effect (EC50) of \[OMIm\]Br to C. pyrenoidosa was 14.95 mg·L-1. The activities of superoxide dismutase (SOD) and peroxidase (POD) decreased, whereas the malondialdehyde (MDA) content increased with the increasing \[OMIm\]Br dosage. The direct harm of \[OMIm\]Br to protein and antioxidant system was the main cause of toxicity to C. pyrenoidosa. It was proved that, owing to the damage of \[OMIm\]Br revealed by flow cytometry (FCM) detection, C. pyrenoidosa cell cycle stopped at S phase and G2/M phase, and [OMIm]Br resulting in necrosis. The degree of cell retardation and necrosis was positively correlated with the \[OMIm\]Br dosage.
    Purification of greenhouse turtle breeding wastewater by different hydroponic systems.
    CHEN Chong-jun1,2, ZHANG Rui1, WU Wei-xiang1,3**
    2014, 33(6):  1553-1558. 
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    Turtle aquaculture is a major Chinese aquaculture industry in rural areas especially in the Yangtze River Delta. The discharge of greenhouse turtle breeding wastewater has brought negative influences on the living and production water quality and safety for the surrounding residents. In this study, we used a static hydroponic system to treat greenhouse turtle breeding wastewater and a dynamic hydroponic system to treat the tail water discharged from the biological aerated filter. The results indicated that both of the hydroponic systems could efficiently remove pollutants. The removal efficiency of COD and TN was better in the static hydroponic system than in the dynamic hydroponic system, while there was no difference in TP removal. In addition, the uptake of N by Ipomoea aquatica accounted for 14.1%-17.5% of TN removal during the entire experiment, while the uptake of P accounted for 12.2%-13.0% of TP removal in the two systems. The I. aquatica static hydroponic system had advantages of easy operation and low cost, being suitable for the greenhouse turtle breeding wastewater purification. In order to decrease the Cr and Pb concentrations in the I. aquatica, the pretreatment should be strengthened. The results provided an important technical support for the application of I. aquatica hydroponic system for treating greenhouse turtle breeding wastewater in China.
    Zooplankton investigation and water quality evaluation in Beiyun River.
    LI Xue-jun1**, BAO Zhan-meng1, GAO Cai-feng1, MAO Zhan-po2
    2014, 33(6):  1559-1564. 
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    In order to protect river environment rationally, we investigated zooplankton and water quality in Beiyun River four times during 2009 and 2010, and analyzed the species composition, density, biomass, diversity index, and water physicochemical character. The results showed that there were 79 species of zooplankton in Beiyun River, including 12 species of Protozoa, 34 species of Rotifers, 23 species of Cladocera, and 10 species of Copepods. Rotifers dominated in spring, summer and winter, while Protozoa in autumn. The dominant species of the zooplankton were Rotifers and pollutiontolerant Cladocera species. The water quality in Beiyun River was generally poor. The total nitrogen, ammonium nitrogen and total phosphorus were the major pollutants in Beiyun River, with their contents 2.12-9.79 times higher than the standards of grade V national surface water environment quality of China. Most of sections in Beiyun River were moderately polluted, some sections were heavily polluted, and the water quality was at the middleheavy pollution level.
     
    Inter-annual dynamics of fish community structure in the Jiangjin section of the upper Three Gorges Reservoir.
    YANG Zhi, TANG Hui-yuan, WAN Li, XU Wei, ZHU Di, CHEN Xiao-juan, QIAO Ye**
    2014, 33(6):  1565-1572. 
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    To understand the impact of the impoundments of the Three Gorges Reservoir on the fish community structure in the Jiangjin section, the commercial catch surveys were conducted from 2006 to 2012. In total 3 orders, 10 families, 45 genera and 67 species were identified. Cluster analysis (CA) separated the different annual species composition into two groups. One group was comprised of the data from the year 2006/2007/2008/2010, and the other group contained the data from 2011/2012. The number of species declined after the operation of the 175 m sluice of the Three Gorges Reservoir in 2010. No significant difference between the two groups was observed by the method of oneway ANOSIM (R=0.96, P=0.07). The fish community structure data for the six years were divided into two groups by using CA and non-metric multidimensional scaling (NMDS) methods. No obvious difference between these two groups (R=1.00, P=0.07) was found by the oneway ANOSIM analysis. The similarity percentage (SIMPER) analysis showed that abundances of the Cobitidae and Homalopteridae decreased, while the abundances of fish adapting to the static or slow flow increased. In brief, the 175 m sluice of the Three Gorges Reservoir brought the greater impact on the fish community structure in the Jiangjin section than the other previous sluices.

     
    Long-term changes in the mean trophic level of the finfish fishery in the Southern Ocean.
    ZHU Guo-ping1,2,3,4**
    2014, 33(6):  1573-1579. 
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    Based on the data provided by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) and the relevant information on the trophic level of selected fish species from Fishbase (www.fishbase.org), this paper analyzed the temporal fluctuation on the mean trophic level (TL-i) of the finfish fishery in the Southern Ocean from 1970 to 2009. The results indicated that two stages were observed in the TL-i of the finfish fishery in the Southern Ocean, i.e., the TL-i had a decreasing trend with a lower level (3.23-3.60) from 1970 to 1991; however, the TL-i (3.82-4.02) were at a higher level from 1992 to 2009. The mean asymptotic length of catch had a similar trend to the mean trophic level. The fishinginbalance (FiB) index was the highest in 1970 and maintained at a stable level after 1997.

     
    Survival rate, oxygen consumption rate and immune enzymetic activity of Mizuhopecten yessoensis at high temperature.
    HAO Zhen-lin, TANG Xue-jiao, DING Jun, BEN Yue, CHANG Ya-qing**
    2014, 33(6):  1580-1586. 
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    Different temperature heating modes were designed to study the response of twosize scallops (10 months and 46 months old) at different high temperature levels (20, 22, 24, 26, 28 ℃) and their capabilities in resisting high temperature under different heating modes (slow heating and abrupt heating), and the survival rate, oxygen consumption rate and immune enzyme activity were investigated in this paper. In the slow heating pattern, scallops reared in 15 ℃ were acclimatized to the different temperature levels 20, 22, 24, 26 and 28 ℃ (temperature increased 1 ℃ per day), and then maintained for 15 days. In the abrupt heating pattern, the rearing temperature was increased from 15 to 20, 24, and 28 ℃ at a rate of 4 ℃ per day, and maintained for 1 day. The results showed that the survival rates of scallops decreased with increasing the temperature under the slow heating mode, and the survival rates of 46 and 10monthold scallops were 96.7% and 77.3% at 28 ℃ respectively. The 46monthold scallops had a significantly higher survival rate than the 10monthold ones when they were exposed to each temperature treatment (P<0.05). The twosize scallops had similar oxygen consumption changes under the test temperature treatments, firstly the oxygen consumption increase, followed by a quick decrease with rising the water temperature. The 10monthold scallops had a significantly higher oxygen consumption rate than the 46monthold ones when they exposed to 15-24 ℃ temperature (P<0.05). When water temperature reached 28 ℃, the oxygen consumption rates of 46 and 10monthold scallops both dropped to the lowest with values at 0.482 and 0.527 mg·g-1·h-1, respectively. The related immune enzyme activities of the twosize scallops also had a similar change at the variable temperatures, however, the 46monthold scallops had a significantly higher value for the immune enzyme activities than the smallsize ones when they were in the same treatment (P<0.05). In a word, our results suggested that the larger scallops had a stronger capability in resisting high temperature compared with smaller ones under different heating modes.
    Uptake of Se and Cd in radish and their effects on growth.
    TIE Mei1, LIU Yang1, LI Hua-wei2, CHEN Zhong-lin1, ZHANG Ying1, LI Bao-rui1, HAN Jie1, XUE Shuang1**
    2014, 33(6):  1587-1593. 
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    The effects of single and compound action of different levels of selenium and cadmium on the radish growth and the absorption of selenium and cadmium were investigated using a pot experiment. The results showed that a moderate amount of selenium (2.5-5.0 mg·kg-1) promoted the growth of radish (43%), representing increases in the germination percentage, the SPAD value of leaf (22%), and biomass of radish (50%). The single pollution of cadmium significantly inhibited the growth of radish (P<0.05). Selenium with a content in the soil below 1.5 mg·kg-1 had an antagonistic action on the effect of cadmium less than 5.0 mg·kg-1, and promoted the growth of radish. The selenium content in radish increased with the increase in level of selenium in the soil and the enrichment of selenium in radish was obvious. The selenium absorption in the underground parts of radish was greater than in the aboveground parts. When the selenium content in the soil was below 5.0 mg·kg-1, the presence of cadmium with the content of 5.0 mg·kg-1 did not affect the selenium absorption of radish. Although the presence of cadmium affected the selenium absorption of radish when the selenium content in the soil ranged from 5.0 to 10.0 mg·kg-1, the selenium content in radish was still in a steady accumulation. When the selenium content in the soil was above 10.0 mg·kg-1, the presence of cadmium inhibited the selenium absorption of radish, which was more obvious for the aboveground parts than for the underground parts. Selenium significantly reduced the cadmium absorption of radish, which was more obvious for the underground parts than for the aboveground parts. Hence planting seleniumrich radish in soil with light cadmium pollution could not only produce safe, nutritious and selenium-rich food, but also realize the reuse of polluted croplands.
    Accumulation, chemical forms and molecular distribution of Cd in two water spinach genotypes. 
    WANG Jun-li1, REN Jian-guo2**
    2014, 33(6):  1594-1600. 
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    Accumulation, chemical form and molecular distribution of Cd in two water spinach varieties, viz. Taiwan308 and Qiangkunqinggu were studied with a hydroponic experiment. The results showed that Cd concentrations in leaves, stems and roots of Taiwan308 were 3.17, 3.55, 39.1 mg·kg-1, respectively, which were significantly higher than those of 2.06, 2.35, 33.5 mg·kg-1 correspondingly for Qiangkunqinggu at the treatment of Cd 1.0 mg·L-1. Cd concentrations in leaves and stems of Taiwan308 were 3.75 and 4.15 mg·kg-1 respectively, which were significantly higher than those of 2.68 and 3.43 mg·kg-1 correspondingly in Qiangkunqinggu at the treatment of 5.0 mg·L-1 Cd, while Cd concentration in roots of Taiwan308 was 55.8 mg·kg-1, and obviously less than that of 83.7 mg·kg-1 in Qiangkunqinggu. The results of Cd chemical forms showed that ethanolextractable Cd was dominant in the leaves, while in the stems and roots, the main forms were ethanolextractable and NaClextractable Cd in the two water spinach varieties. Compared with Qiangkunqinggu in leaves, stems and roots, Taiwan308 had a higher proportion of more mobile H2Oextractable Cd, but a lower proportion of less dissoluble HAcextractable and HClextractable Cd. The levels of Cd concentration and the varieties of water spinach had obvious effects on Cd chemical forms in vivo, especially in roots. The results of Cd molecular distribution showed that the majority of soluble Cd in leaves was bounded to low and high molecular weight components, while in roots Cd was bounded to phytochelatins (PCs) and some proteins of 10-20 kDa. The concentration of CdPCs in roots of Qiangkunqinggu was lower than that of Taiwan308, which would decrease the Cd translocation from root to aboveground part, finally leading to the lower concentration of the edible parts.
    Geochemical component character of groundwater of central and southern Liaoning.
    ZHOU Zhi-hua1**, WANG Hai-yan2, XUE Yan1
    2014, 33(6):  1601-1605. 
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    Understanding the geochemical character of groundwater is important for regional groundwater environment protection, ecological environment monitoring and study of biogeochemical processes of earth surface. This paper discussed hydrochemistry types and formation processes of groundwater, according to the physicochemical properties, chemical composition and evolved gas composition of groundwater in the central and southern Liaoning. There were six hydrochemistry types in the research areas, i.e. NaCa-HCO3, CaMg-NO3, Na-CO3SO4, CaMg-HCO3, Ca-HCO3, and Na-SO4. Evolved gases mainly contain N2, CO2, CH4 and He, indicating that the underground water was impacted by the materials of organic source and earth deep source. The underground water in some regions had been affected by agricultural production, and the hydrochemistry type was different from that of the natural underground water. The different hydrochemistry types of underground water in different regions were jointly controlled by reservoir depth, exposed position, fracture property, grain size and lithology. This study has an important significance for protecting the ecological environment of the central and southern Liaoning, and clarifying the chemical element migration pathway and mechanism of the supergene zone.
    Spatial distribution and dynamics of lake and marsh wetlands in China.
    XU Feng-jiao1,2, ZHOU De-min1,2**, ZHANG Yi-ran1,2, NIU Zhen-guo3
    2014, 33(6):  1606-1614. 
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    Lake and marsh wetlands can authentically record the information of climate and environmental changes. The area and number changes of lake and marsh wetlands can provide evidence of spatial and temporal characteristics of water resource changes in China. The distribution and the dynamics of lake and marsh wetlands in China have different characteristics because of the differences in their natural environments. Understanding the changes in these lake and marsh wetlands in different years can help to make effective value assessment, management and protection. In this study, according to the regional differences in natural environments of the country, lake and marsh wetlands are divided into six regions: northeastern mountain and plain region, eastern plain region, Inner Mongolia-Xinjiang plateau region, Qinghai-Tibet Plateau region, YunnanGuizhou Plateau region, and the southern coastal region. Based on the historical data from “Records of Lakes in China” and “Records of Marshes in China”, as well as the current status data of lake and marsh wetlands in 2008 obtained by remote sensing technology, the regional variations and type changes in lake and marsh wetlands in recent 20 years were studied. The result shows that the distributions of national lake and marsh wetlands in different regions are unbalanced, and basically all regions have disappearing or degrading lake and marsh wetlands. However, a small part of lake and marsh wetlands expand, which are mainly distributed in the Tibetan Plateau region. Most of the lake and marsh wetlands are disappearing or degrading, and this trend, to some extent, reflects their weakening ecosystem services function, and declining economic value.
    Modeling the geographic distribution of three endangered Vitis species in China.
    JIANG Jian-fu1, FAN Xiu-cai1, ZHANG Ying1, WEI Wei2, KANG Ding-ming3, LIU Chong-huai1**
    2014, 33(6):  1615-1622. 
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    The geographic distribution patterns of three endangered Vitis species (V. yunnanensis C. L. Li, V. hui Cheng and V. wenchouensis C. Ling ex W. T. Wang) in China were investigated through analyses of their comprehensive geographic distribution information. The current distribution patterns of the three Vitis species were mapped by ArcGIS software. Their potential future distribution patterns under the impacts of present climate and potential future climate change were simulated and predicted using BIOCLIM model. The results showed that the three wild Vitis species are distributed mainly in south of the Yangtze River. V. hui is mainly distributed in northern Jiangxi Province, and V. wenchouensis in southeastern Zhejiang Province, while V. yunnanensis is distributed in a scattered pattern. The dominant factors affecting the geographic distribution of V. yunnanensis are mean temperature of the driest quarter, mean annual temperature range, and annual precipitation. Annual mean temperature, precipitation seasonality, mean temperature of the wettest quarter and mean monthly temperature range are that for V. hui; and minimum temperature of the coldest month, annual precipitation, and precipitation of the driest month are that for V. wenchouensis. Simulated present distributions of these three Vitis species by BIOCLIM model match very well their actual distribution ranges, indicating that the simulation by BIOCLIM model is accurate. The current and potential future distributions of these species are and will still remain in south China. Under the future climate scenario with a doubled CO2 concentration, these three Vitis species may all shift northward; but the ranges of the suitable zone change are not obvious.
    Predictive distribution and habitat suitability assessment of Notholirion bulbuliferum based on MaxEnt and ArcGIS.
    CHE Le, CAO Bo, BAI Cheng-ke**, WANG Juan-juan, ZHANG Lin-lin
    2014, 33(6):  1623-1628. 
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    In this study, 89 occurrence records, 28 climatic and 6 soil factors were used to predict the potential distribution and habitat suitability of Notholirion bulbuliferum in China based on the MaxEnt modeling and geographic information system. The results showed that the highly potential distribution (suitability index >0.5) mainly located in Sichuan (Aba, Ganzi and Liangshan, with an area of 51813 km2), Yunnan (Diqing and Lijiang, 15889 km2), Shaanxi (Taibai, 16131 km2), Tibet (Nyingchi, Lhoka and Shigatse, 17748 km2) and Gansu (Longnan, 12184 km2) provinces. The AUC of ROC curve was 0.979, indicating that the predictive results with the MaxEnt model were highly precise. The main environmental factors determining the potential distribution were annual average precipitation (the contribution rate, 38%), altitude (32.1%), average monthly minimum temperature of January (7.6%), average monthly precipitation of January (6.8%) and topsoil pH (H2O) (3.9%). The environmental variables in the highly potential areas were determined as annual average precipitation around 870 mm, altitude around 2550 m, average monthly minimum temperature of January around -6.3 ℃, average monthly precipitation of January around 5.3 mm and topsoil pH (H2O) around 6.77. The results will provide valuable references for wild resource conservation, plantation regionalization and standard cultivation of N. bulbuliferum in highly suitable areas.
    Simulation of Cuora galbinifrons nest predation.
    LI Min1, WANG Ji-chao1, LIU Hai-wei2, SHI Hai-tao1**
    2014, 33(6):  1629-1633. 
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    Nest predation in ovipara is a primary cause of reproductive failure. To investigate the type of nest predators, predation rates and the effect on breeding success of IndoChinese box turtle (Cuora galbinifrons) in different habitats, we buried eggs of redeared turtle (Trachemys scripta elegans) to simulate IndoChinese box turtle nests at Diaoluoshan village, Diaoluo Nature Reserve  in Hainan Island from March to May 2013. One hundred and twenty artificial nests (two eggs per nest) were evenly placed in plantation forest, secondary forest and primary forest, and triggered cameras were placed around a sample of nests to identify predators. The result indicated that 66.7% nests were depredated, and small mammals (51.3%) and ants (28.8%) were the main predators.  Predation rates in these forests were 72.5%, 62.5% and 62.5% respectively, but the differences were not significant (P>0.05, n=40). In secondary forest, the nest predation rate was higher in forest centers than in forest edges (P<0.05, n=20). No obvious differences were found in nest predation rate between forest centers and edges in plantation forest and primary forest.
    Effects of landscape changes on habitat distribution of Hainan Eld’s deer.
    YAN Wen-bo1, ZENG Zhi-gao2**, SONG Yan-ling2
    2014, 33(6):  1634-1638. 
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    In this study, we focused on the influence of landscape change from 1950s to 1980s on the changes of suitable habitat and distribution of the Hainan Eld’s deer (Cervus eldi hainanus). Based on distribution data of the deer in 1950s and 1980s, we built two models of habitat distribution and a model of habitat distribution change. We further analyzed the main landscape factors influencing the suitable habitat distribution in the two periods, and evaluated the main landscape factors influencing the habitat distribution change from 1950s to 1980s. The results showed that the suitable habitat distribution of the deer had significant positive correlations with the forest cover and patch richness, but a significant negative correlation with the forest edge density in 1950s. However, in 1980s the suitable habitat distribution of the deer was negatively affected by the patch richness, but positively affected by the forest edge density. Road density also affected the suitable habitat distribution in the 1980s. The suitable habitat change was greatly affected by land use conversion from grassland to forest land and agricultural land, and from grassland and forest land to residential land. Moreover, the change of road density also made a contribution to the suitable habitat distribution. Our results confirmed that human disturbance greatly affected landscape change and resulted in the loss of deer habitat.
    Habitat differentiation of Tibetan antelope in cold and warm seasons in Aerjin Mountain National Nature Reserve, China.
    SU Xu-kun1, DONG Shi-kui1**, LIU Shi-liang1, SHI Jian-bin1, WU Yu1, ZHANG Xiang2, GAO Feng2, XU Dong-hua2
    2014, 33(6):  1639-1646. 
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    Aerjin (Altun) Mountain National Nature Reserve is one of three refuges for rare and endangered ungulates such as Tibetan antelope in QinghaiTibetan Plateau. As a kind of migration ungulate, Tibetan antelope’s population could be effectively protected through identifying its habitat suitability in cold (January) and warm (July) seasons. On the basis of niche theory, we used GIS and AHP jointly to build a GISbased niche model for delimiting and classifying habitat suitability in cold and warm seasons. Results showed that total areas of high suitability and moderate suitability habitats in cold and warm seasons were 12620 and 15630 km2, respectively. High suitability habitats in cold and warm seasons were located in the northeast of the reserve (the northeast of Kumkury Desert), the middle of the reserve (from Kardun inspection station to the eastern boundary of Aqqikkol Lake) and the southwest of the reserve (near Tuzihu inspection station). Moderate suitability habitats were located in the southeast of the reserve and around the high suitability habitats. The total areas of low suitability habitats were 9930 km2 in cold season and 8400 km2 in warm season. Low suitability habitats were located between moderate suitability habitats and unsuitable areas in cold season, and around Jingyu Lake and moderate suitability habitats in warm season. Unsuitable areas in cold and warm seasons were 24290 and 22810 km2, respectively, and were consisted of the north of reserve, lakes, desert, and high elevation zone. Our study indicated that habitat suitability differed in cold and warm seasons. The distribution of Tibetan antelope was predominantly limited by natural and anthropogenic factors in cold season. The distributions of Tibetan antelope were more concentrative in cold season, but more dispersive in warm season.
    Landscape dynamics along a river corridor in alpine desert region and its driving factor analysis: A case study in Altun National Nature Reserve.
    LIU Shi-liang1**, ZHAO Hai-di1, DONG Shi-kui1, SU Xu-kun1, LIU Qi1, ZHANG Xiang2
    2014, 33(6):  1647-1654. 
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    Alpine desert grassland dynamics is important for global change study. As one of the four largest “noman lands” in China, Altun Mountain National Nature Reserve is facing alpine desert grassland ecosystem changes, which may have a tremendous impact on the habitats of wild animals. Especially, the landscape along the rive corridor could be greatly affected by climate change. Based on GIS and RS technology, we selected a typical river corridor in Aya Lake Basin as the case study site and classified the landscape types using remote sensing data in 1990, 2001 and 2007. Taking advantages of landscape theories and methods, we analyzed the landscape pattern and dynamics in the region. The results showed that the areas of both water and salinealkali lands in the region increased significantly, while the grasslands with different coverage degraded due to the conversion into other land uses. The integrated pattern of landscape changed greatly. Patch density and landscape diversity index increased, while the landscape shape became simple. Largest patch index increased and the splitting index decreased. The increases of water area and salinealkali land with grassland degradation caused the decrease of the NDVI values. Climate change trend analysis suggested that the increases in precipitation and temperature were the major driving forces for the landscape change in the region. The rise of the lake water area changed the distribution of the swamp, leading to the increase of water table and the increase of soil salinization.
    Land-use scenarios simulation based on the CLUE-S model in Kunming.
    ZHANG Wei1, LIU Miao2**, QI Yu-shan1
    2014, 33(6):  1655-1662. 
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    Land-use model plays an important role in land-use change analysis, simulation and prediction. Land-use maps in 1986, 1996 and 2006 in Kunming were interpreted based on remote sensing images. The suitability of the CLUES model was estimated in Kunming with complex topography. Three scenarios were designed considering different polices and development trends for land use from 2007 to 2020. In the “historic development trend scenario”, forestland area (matrix of the landscape) would decrease constantly, while build-up land and grassland area would increase. The landscape pattern would be more fragmental. In the “planning scenario”, buildup land would increase rapidly, while farmland and forest land would decrease. The trend of landscape fragment would be less severe than that in the “historical development trend scenario”. In the “ecologypriority scenario”, forestland would increase, while farmland and grassland would decrease, and the trajectory of landscape fragment and the landscape pattern would be more optimized. The simulated results of CLUE-S model provide a scientific support for land-use planning and policymaking in Kunming.
     
    Research progress of plant leaf hydraulic conductivity.
    ZHANG Zhi-liang1,2**, LIU Guo-dong1, ZHANG Fu-cang3, ZHENG Cai-xia2, KANG Yin-hong2
    2014, 33(6):  1663-1670. 
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    Leaf water transport is a complex physiological process in the SPAC system. It is not only regulated by the plant itself, but also affected by the external environmental conditions. This paper reviews recent new progresses and developments including the role of leaf water transport in plant water balance, the definition of leaf hydraulic conductivity and its influencing factors. Internal and external environmental factors differ in affecting leaf hydraulic conductivity. This paper mainly explains the effects of soil factors, meteorological factors, plant hormones, developmental stages and anatomical characteristics on leaf hydraulic conductivity. At last, we put forward some urgent problems needing to be considered in leaf hydraulic conductivity research and made prospects for key development direction of research in the future.
    Nitrogen and phosphorus stoichiometry in plants and its application to research on medicinal plants.
    DONG Xiao-lei1, WANG Yuan-zhong2, ZHANG Jin-yu2, JIN Hang2, ZHANG Ji2**
    2014, 33(6):  1671-1677. 
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    Composition and distribution of nitrogen (N) and phosphorus (P) in an organism are interrelated with the environment, and regulates plant nutrition and growth process. In this paper, we review the abiotic, biotic and anthropogenic effects on plant N and P stoichiometry, the influence mechanism of N and P stoichiometry on growth and metabolism of plants, and its effects on the growth, development and metabolite accumulation of medicinal plants. We suggest that N and P stoichiometry could provide new ideas for the research on medicinal plants, including analyzing the growth and metabolism responses of the plants to environmental changes, investigating the interaction between mycorrhizal fungi and the plants, and the identifying limiting nutrient(s). This review could also provide a theoretical basis for scientific planting and resource evaluation of the medicinal plants.
     
    Interactions of ozone stress and other environmental factors on plants.
    LIE Gan-wen, XUE Li**
    2014, 33(6):  1678-1687. 
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    With the development of urbanization, the concentration of tropospheric ozone has been considerably increased during the past several decades, and its phytotoxicity has attracted serious attention as a widespread pollution problem. As a highly oxidative pollutant, ozone affects terrestrial plants in a variety of ways. It may negatively affect plant growth by causing morphological and physiological damage under ozone stress. Meanwhile, the impact of ozone on plants is greatly affected by atmospheric, soil and/or light conditions. Nowadays, global climate change and the normalization of extreme climate have significantly increased the opportunity of the interactions of ozone with many other environmental factors. As a result, the conditions in the experiments with consideration of the interactions of ozone and other environmental factors are much closer to natural environmental condition. The effects of interactions of ozone and these environmental factors are quite complicated, and mostly depend on plant species, ozone concentration, time, plant sensitivity to these environmental factors and the specific climate conditions. In this paper, the effects of interactions of ozone with carbon dioxide, sulfur dioxide, acid rain, nitrogen, drought, light or ultravioletB radiation were summarized and the interaction mechanism of ozone with other environmental factors was discussed. The hotspots for future study in this area should be the interactions of ozone with other environmental factors on the underground part and rhizosphere of plants, and the interplay mechanism of their roots, root functional changes and rhizosphere processes, the interactions of ozone with other environmental factors on various forests under different climatic conditions, the interaction of ozone with climate, air pollutants, heavy metal pollutants or stress such as low temperature on plants. In this paper, several patterns of biological evolution under stresses were figured out, to provide references for reasonable selection of ozoneresistant plants. It is of great significance to improving the ecological environment.
    Foliar uptake of NH4+ in PM2.5 in seedlings of two poplar species using the technique of 15N tracing.
    SHI Jie, LIU Qing-qian, AN Hai-long, CAO Xue-hui, LIU Chao, YIN Wei-lun, XIA Xin-li, GUO Hui-hong**
    2014, 33(6):  1688-1693. 
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    Watersoluble inorganic ions such as NH4+ are the major components of fine particles (PM2.5). The absorption, distribution and utilization of NH4+ on the leaf surface of Populus tomentosa and P. deltoids × P. nigra seedlings were studied by using the 15N trace technique. Our results showed that 15NH4+ was absorbed rapidly by P. tomentosa and P. deltoids × P. nigra leaves and the rates of absorption all peaked 6 hours after solution application. Significant differences were observed in the absorption rate between two poplar species, with the maximum absorption rate of P. tomentosa being 3 times that of P. deltoids × P. nigra. The content of 15N in leaves peaked at the same time (24 hours after treatment) in the two species, but the maximum amount of 15N of P. tomentosa was about 4 times that of P. deltoids × P. nigra. Foliar application of 15Nlabeled ammonium sulfate (15NH4SO4) solution led to a significant increase of total nitrogen level in the leaves of both poplars. The leaf total N contents of P. tomentosa and P. deltoids × P. nigra were 1.26 and 1.36 times that of control 7 days after treatment, respectively. The Ndff values of different organs showed that the 15N absorbed by functional leaves was transported to both the upper and lower parts of the plants, which was mainly stored in stems of P. tomentosa, but transported to roots of P. deltoids × P. nigra. Foliar application of 15NH4SO4 enhanced the net photosynthetic rate of both poplars to varied degrees 7 days after treatment, but no significant effect on stomatal conductance was observed.
    Effect of disturbed and undisturbed soils on the carbon assimilation capacity of autotrophic microbes.
    WU Hao1,2, JIAN Yan2, GE Ti-da2, WANG Jiu-rong2, YUAN Hong-zhao2, TAN Li-min1, LI Ke-lin1**, WU Jin-shui2
    2014, 33(6):  1694-1699. 
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    Assimilation of atmospheric carbon dioxide (CO2) by autotrophic microbes is an integral process in the soil environment. However, the influence of disturbed and undisturbed soils on CO2assimilation capacity remains poorly understood. In this study, we incubated four types of disturbed and undisturbed soil samples for 110 days in a closed, continuously 14Clabeled CO2 atmosphere and measured the amount of 14Clabeled carbon (C) incorporated in the microbial biomass during this period. The allocation of 14Clabeledassimilated C in labile soil C pools such as dissolved organic C (DOC) and microbial biomass C (MBC) was analyzed over the 14Clabeling span. Significant amounts of 14C-SOC were detected in both disturbed and undisturbed soils. The assimilative rate ranged from 0.015 to 0.148 g·m-2·d-1 in the disturbed soils and from 0.007 to 0.050 g·m-2·d-1 in the undisturbed soils. A significant positive linear relationship was detected between the concentrations of 14C-SOC and 14C-MBC (R2=0.955, P<0.01). The proportions of 14C-DOC, 14C-MBC, and 14C-SOC to the total DOC, MBC, and SOC were 0.9%-4.5%, 2.2%-9.7%, and 0.09%-0.43% in the undisturbed soils, and 0.26%-1.09%, 3.6%-20%, and 2.9%-5.7% in the disturbed soils, respectively. Furthermore, the distribution and transformation of microbeassimilated C had much greater influence on the dynamics of DOC and MBC than on those of SOC. These results offer new insights into the importance of microbes in the assimilation of atmospheric CO2 and of the potentially significant contributions made by microbial autotrophy to terrestrial C cycling.
     
    Ecological system stability and diversity based on complex networks.
    LI Yi-min**, LI Xin, HUA Jing
    2014, 33(6):  1700-1706. 
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    The internal mechanism between the ecological diversity and stability has been a research hotspot. Based on the theory of complex networks, considering the species as a node, prey relationships among species as directed edges, prey on dependent predation among species as edge weight, the directed and weighted complex networks of food web are constructed in a specific broadleaved mixed forest ecosystem. Under the condition of randomly or selectively removing network nodes, the diversity and stability of system is calculated using related indicators and the correlation between them is studied. The result shows that in the broadleaved forest ecosystem, the loss of a particular species reduces the biodiversity and influences the balance of energy supply and demand in the ecosystem, causes the change of related species’ life habits, then increases the strength of predation on other species which makes the originally stable feeding relationship gradually broken. The constant rupture of prey relationships between species finally prompts the decline of the stability of the ecosystem. As a result, in the broadleaved mixed forest ecosystem, the loss of ecological diversity will reduce the stability of the system, and the diversity and stability is positively correlated.