Table of Content

18 May 2012, Volume 23 Issue 05

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Articles

Disease resistance signal transfer between  roots of different tomato plants through common arbuscular mycorrhiza networks.

XIE Li-jun, SONG Yuan-yuan, ZENG Ren-sen, WANG Rui-long, WEI Xiao-chen, YE Mao, HU Lin, ZHANG Hui

2012, 23(05):  1145-1152. 

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Common mycorrhizal networks (CMNs) are the underground conduits of nutrient exchange between plants. However, whether the CMNs can serve as the underground conduits of chemical communication to transfer the disease resistance signals between plants are unknown. By inoculating arbuscular mycorrhizal fungus (AMF)Glomus mosseae to establish CMNs between ‘donor’ and ‘receiver’ tomato plants, and by inoculating Alternaria solani, the causal agent of tomato early blight disease, to the ‘donor’ plants, this paper studied whether the potential disease resistance signals can be transferred between the ‘donor’ and ‘receiver’ plants roots. The real time RT-PCR analysis showed that after inoculation with A. solani, the AMF-inoculated ‘donor’ plants had strong expression of three test defenserelated genes in roots, with the transcript levels of the phenylalanine ammonia-lyase (PAL), lipoxygenase (LOX) and chitinase (PR₃) being significantly higher than those in the roots of the ‘donor’ plants only inoculated with A. solani, not inoculated with both A. solani and AMF, and only inoculated with AMF. More importantly, in the presence of CMNs, the expression levels of the three genes in the roots of the ‘receiver’ plants were significantly higher than those of the ‘receiver’ plants without CMNs connection, with the connection blocking, and with the connection but the ‘donor’ plants not A. solaniinoculated.  Compared with the control (without CMNs connection), the transcript level of the PAL, LOX and PR₃ in the roots of the ‘receiver’ plants having CMNs connection with the ‘donor’ plants was 4.2-, 4.5- and 3.5-fold higher, respectively. In addition, the ‘donor’ plants activated their defensive responses more quickly than the ‘receiver’ plants (18 and 65 h vs. 100 and 140 h). These findings suggested that the  disease resistance signals produced by the pathogen-induced ‘donor’ tomato plant roots could be transferred to the ‘receiver’ plant roots through CMNs.

Effects of extraneous inorganic nitrogen forms on the dynamics of soil amino sugars.

LI Xiang1,2, HE Hong-bo1, ZHANG Wei1, LU Hui-jie1,2, ZHANG Xu-dong1,3, ZHENG Li-chen1, TIAN Fu-lin4, LI Hong4

2012, 23(05):  1153-1158. 

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Substrate availability affects microbial growth, whereas extraneous nitrogen forms can significantly affect microbial metabolic processes. As for soil amino sugars, the stable residues in microbial cell wall, their synthesis, decomposition and turnover are closely related to the availability of extraneous carbon and nitrogen. Using isotope tracing technique to study soil amino sugars can further understand the substrate utilization profiles by soil microorganisms. In this study, two incubation tests were conducted, with glucose plus ¹⁵Nlabelled NH₄⁺ or NO₃^-as the substrates, respectively. The ¹⁵N enrichment in each kind of soil amino sugars was identified by gas chromatography/mass spectrometry (GC/MS) to trace the dynamics of soil ¹⁵Nlabelled and native amino sugars. During the incubation, the content of soil ¹⁵Nlabelled amino sugars increased significantly, and the transformation rate from NH₄+ to amino sugars was significantly higher than that from NO₃^-, suggesting the preferred utilization of NH₄⁺ than NO₃^- by soil microorganisms. Significant changes in the amounts of soil unlabelled amino sugars were observed. The amount of unlabelled glucosamine increased with NH₄⁺ addition, but decreased gradually with NO₃^- addition. The content of unlabelled muramic acid decreased gradually, especially with NO₃^-addition. Either the increase or the decrease of galactosamine did not exceed 20% to the original value. These compoundspecific changes showed that the heterogeneous microbial residues played different roles on the turnover and stabilization of nitrogen in soil matrix. Fungal cell wall residues were easily accumulated in soil matrix, which benefited the stabilization of soil organic matter, while bacterial cell wall residues were easily degraded, playing an important role in the turnover of soil organic matter.

Characteristics of dominant tree species stem sap flow and their relationships with environmental factors in a mixed conifer-broadleaf forest in Dinghushan, Guangdong Province of South China.

HUANG De-wei1,2, ZHANG De-qiang1, ZHOU Guo-yi1, LIU Shi-zhong1, Otieno Dennis1, LI Yue-lin1

2012, 23(05):  1159-1166. 

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By the method of Granier’s thermal dissipation probe, the stem sap flow density of four dominant tree species (Pinus massoniana, Castanopsis chinensis, Schima superba, and Machilus kwangtungensis) in a mixed coniferbroadleaf forest in Dinghushan Reserve of South China was continuously measured in the dry season (November) and wet season (July) in 2010, and the environmental factors including air temperature, relative humidity, and photosynthetically active radiation (PAR) were measured synchronically, aimed to study the characteristics of the stem sap flow of the tree species in response to environmental factors. During the dry and wet seasons, the diurnal changes of the stem sap flow velocity of the tree species all presented a typical single-peak curve, with high values in the daytime and low values in the nighttime. The average and maximum sap flow velocities and the daily sap flow flux of broadleaved trees (C. chinensis, S. superba,and M. kwangtungensis) were significantly higher than those of coniferous tree (P. assoniana), and the maximum sap flow velocity of P. massoniana, C.  valueschinensis, S. superba,and M. kwangtungensis was 29.48, 38.54, 51.67 and 58.32 g H₂O·m^-2·s^-1, respectively. A time lag was observed between the sap flow velocity and the diurnal variations of PAR, vapor pressure deficiency, and air temperature, and there existed significant positive correlations between the sap flow velocity and the three environmental factors. The PAR in wet season and the air temperature in dry season were the leading factors affecting the stem sap flow velocity of the dominant tree species.

Profile distribution of soil aggregates organic carbon in primary forests in Karst cluster-peak depression region.

LU Ling-xiao1,2，3, SONG Tong-qing1,2, PENG Wan-xia1,2, ZENG Fu-ping1,2, WANG Ke-lin1,2, XU Yun-lei1,2, YU Zi4, LIU Yan4

2012, 23(05):  1167-1174. 

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Soil profiles were collected from three primary forests (Itoa orientalis, Platycladus orientalis, and Radermachera sinica) in Karst clusterpeak depression region to study the composition of soil aggregates, their organic carbon contents, and the profile distribution of the organic carbon. In the three forests, >2 mm soil aggregates were dominant, occupying about 76% of the total. The content of soil total organic carbon ranged from 12.73 to 68.66 g·kg^-1, with a significant difference among the forests. The organic carbon content in <1 mm soil aggregates was slightly higher than that in >2 mm soil aggregates, but most of soil organic carbon was stored in the soil aggregates with greater particle sizes. About 70% of soil organic carbon came from >2 mm soil aggregates. There was a significant positive relationship between the contents of 2-5 and 5-8 mm soil aggregates and the content of soil organic carbon. To increase the contents of 2-8 mm soil aggregates could effectively improve the soil carbon sequestration in Karst region. In Itoa orientalis forest, 2-8 mm soil aggregates accounted for 46% of the total, and the content of soil total organic carbon reached to 37.62 g·kg^-1, which implied that Itoa orientalis could be the suitable tree species for the ecological restoration in Karst region.

Carbon density and its spatial distribution in Quercus acutissima plantations under different thinning intensities.

CHENG Xiang-rong1, YU Mu-kui1, GE Le1, ZHANG Chun-xiang2, WANG Wan1

2012, 23(05):  1175-1180. 

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Quercus acutissima is a tree species widely planted in Jianghuai hilly lands. In this study, the Q. acutissima plantations after five years of different thinning [15% (T₁₅), 30% (T₃₀), 50% (T₅₀) and unthinning (CK)] were selected, and a sampling plot investigation was made to analyze the carbon density and its spatial distribution in these plantations. In treatments T₁₅, T₃₀ and T₅₀, the tree carbon density  increased by 9.1%, 29.6% and 28.4%, respectively, as compared with CK. The carbon density in tree organs was in the order of stem > root > branch > bark > leaf. With increasing thinning intensity, the carbon density in litters decreased while that in 0-50 cm soil layer had a slight increase, but no significant difference was observed between thinning and unthinning. The total carbon density of the Q. acutissima stands under different thinning intensities was in the order of T₃₀> T₅₀> T₁₅> CK, with an increase of 16.3, 14.5 and 3.6 t C·hm^-2 in treatments T₁₅, T₃₀ and T₅₀, respectively, as compared with CK, but there were no significant differences among the treatments. In treatments T₁₅, T₃₀ and T₅₀, soil respiration was also higher than that in CK, and the difference was significant between treatments T₃₀ and CK. Overall, thinning was helpful to the enhancement of carbon storage in theQ. acutissima plantations in Jianghuai hilly lands, and 30% thinning could be the best.

Photosynthetic functions and chlorophyll fast fluorescence characteristics of five Pinus species.

QIU Nian-wei1, ZHOU Feng2, GU Zhu-jun2, JIA Shu-qin1, WANG Xing-an1

2012, 23(05):  1181-1187. 

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A comparative study was made on the needle morphological characteristics, photosynthetic rate, and chlorophyll fast fluorescence induction curves of five representative Pinus species P. parvifiora, P. armandii, P. bungeana, P. tabuliformis, and P. densiflora. Significant differences were observed in the needle morphological characteristics among the five species. P. tabuliformis had the longest needle length and highest needle density, whereasP. bungeana had the highest chlorophyll content. P. densiflora and P. parvifiora had the maximum and minimum photosynthetic rate, respectively. There was a positive correlation between the photosynthetic rate and stomatal conductance across the five species. The differences in the chlorophyll fast fluorescence induction curves of the five species were mainly manifested in J-step and I-step. Although the five species had similar values of F_v/F_m,F_v/F_o and T_fm, P. parvifiora had significantly higher values of dV/dt_o, dVG/dt_o, V_j and V_i, but lower energy flux ratio ψ_o, φ_Eoand φ_Ro,  compared with the other four species. The low PSII activity and efficiency of P. parvifiora might relate to its smallest S_m,S_m/T_fm and N.P.  densiflora and P. parvifiora had the maximum and minimum vitality indices PI_{(ABS/CSo/CSm)} and DF, respectively, and there existed significant positive correlations between the PI_(CSo) and PI_(CSm) and the net photosynthetic rate of the five species, suggesting that PI_(CSo) and PI_(CSm) could be used to estimate the photosynthetic activity of Pinus trees.

Effects of understory removal and nitrogen addition on the soil chemical and biological properties of Pinus sylvestris var. mongolica plantation in Keerqin Sandy Land.

LIN Gui-gang1,2, ZHAO Qiong1, ZHAO Lei1,2, LI Hui-chao1,2, ZENG De-hui1

2012, 23(05):  1188-1194. 

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A full factorial experiment was conducted to study the effects of understory removal and nitrogen addition (8 g·m^-2) on the soil NO₃^--N and NH₄⁺-N concentrations, potential net nitrogen mineralization rate (PNM) and nitrification rate (PNN), microbial biomass C (MBC) and N (MBN), MBC/MBN, urease and acid phosphomonoesterase activities, and Olsen-P concentration in a Pinus sylvestris var. mongolica plantation in Keerqin Sandy Land during a growth season. Understory removal decreased the soil NH₄⁺-N concentration, PNM, MBC, and MBN/MBN significantly, increased the soil Olsen-P concentration, but had little effects on the soil NO₃^--N concentration, PNN, and urease and acid phosphomonoesterase activities. Nitrogen addition increased the soil NO₃^--N concentration, PNM and PNN significantly, but had little effects on the other test properties. The interaction between understory removal and nitrogen addition had significant effects on the soil NH₄⁺-N concentration, but little effects on the soil NO₃^--N concentration. However, the soil NO₃^--N concentration in the plots of understory removal with nitrogen addition was increased by 27%,  compared with the plots of nitrogen addition alone, which might lead to the leaching  of NO₃^-  It was suggested that understory vegetation could play an important role in affecting the soil chemical and biological properties in Mongolian pine plantations, and hence, the importance of understory vegetation should not be neglected when the forest management and restoration were implemented.

Organic carbon storage in urban built-up areas of China in 1997-2006.

ZHU Chao, ZHAO Shu-qing, ZHOU De-cheng

2012, 23(05):  1195-1202. 

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With the increase of greenhouse gases emission in urban regions, urban carbon cycle plays a more and more important role in global carbon cycle. To estimate urban carbon emission and carbon storage is crucial for understanding urban carbon cycle. By using China’s statistics data and the results from recent publications, this paper estimated the organic carbon storage in China’s urban built-up areas in 1997-2006. From 1997 to 2006, the total organic carbon storage in the urban built-up areas increased from 0.13-0.19 Pg C (averagely 0.16 Pg C) to 0.28-0.41 Pg C (averagely 0.34 Pg C), and the organic carbon density increased from 9.86-14.03 kg C·m^-2 (averagely 11.95 kg C·m^-2) to 10.54-15.54 kg C·m^-2 (averagely 13.04 kg C·m^-2). The total organic carbon storage in the urban builtup areas was mainly contributed by soils (78% in 1997 and 73% in 2006), followed by buildings (12% in 1997 and 16% in 2006) and green spaces (9% in 1997 and 10% in 2006), while the carbon storage in resident bodies only accounted for less than 1%, which could be neglected.

Ecosystem service interactions and their affecting factors in Jinghe watershed at county level.

PAN Ying1, ZHEN Lin1, LONG Xin1,2, CAO Xiao-chang1,2

2012, 23(05):  1203-1209. 

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Taking the multiple ecosystem services (grain supply, meat supply, fuelwood supply, water resource conservation and soil retention) as test objects, this paper analyzed the interactions among these services, the interaction modes and the possible affecting factors in 31 counties of Jinghe watershed. At the county level, there existed great differences in the interactions among different pairs of the ecosystem services. The grain supply showed significant positive correlation with meat supply  but negative correlation with soil retention, whereas the water resource conservation showed significant positive correlations with fuel-wood supply  and soil retention. As for the interaction modes of the ecosystem services, 24 counties were primarily of regulation services, 3 counties were of supply and regulation services in balance, and 4 counties were primarily of grain supply. The total ecosystem service index of the interaction modes in each county varied greatly, with 5.1 times of difference between the maximum (Jingyuan County) and the minimum value (Yanchi County). The total ecosystem service index was significantly positively correlated with precipitation  and soil total nitrogen, and negatively correlated with solar hours. The increase of farmland had negative effects, while that of shrub land and grassland had great positive effects on the total ecosystem service index, but the increase of forestland had less effects.

Responses of vegetations in Minqin desert area to climate change.

CHANG Zhao-feng1,2,3, HAN Fu-gui1,2,3, ZHONG Sheng-nian1,2,3

2012, 23(05):  1210-1218. 

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Based on the phenological data in 1974-2009 and the  plot vegetation data  in 2002-2010 as well as the meteorological data, this paper analyzed the responses of the vegetations in Minqin desert area to climate change. In 1961-2010, the air temperature and air humidity in the study area increased, and the increasing rate of the mean annual air temperature was greater than the global level and China’s level over the past century. The responses of the vegetations to the air temperature change were mainly manifested in the advance of spring phenology, delay of autumn phenology, and lengthening of growing duration, whereas the responses of the vegetations to precipitation change were mainly manifested in the decrease of vegetation coverage and pure coverage with the decreasing precipitation. The plant density and richness fluctuated with the variation of precipitation, and the vegetation coverage and pure coverage were positively correlated with the annual precipitation firstly, and the precipitation in Jun-July and in April-May secondly. The plant density and richness were positively correlated with the precipitation in September. The advance of the spring phenology was in the order of bud-expansion > budopening > beginning of flowering > beginning of leaf-extension and leaf flourish > flower-bud appearance > flower flourishing > end of flowering > fruitmaturity, whereas the delay of autumn phenology was in the order of full leaf-discoloration > beginning of leaf-fall > beginning of leafdiscoloration > end of leaf-fall. As compared with the increase of air temperature in autumn, the increase of air temperature in spring had greater effects on the plant phenology in Minqin desert area.

Spatiotemporal differentiation of land cover change and grassland degradation pattern in Yangtze River headwaters area.

GUO Luo1, DU Shi-hong2, XUE Da-yuan1, CAI Liang1

2012, 23(05):  1219-1225. 

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Based on field survey data, remote sensing images and statistical data, this paper analyzed the spatiotemporal differentiation of land use and grassland degradation patterns in Yangtze River headwaters area in 1987-2007, and discussed the main natural factors (elevation, position and slope) leading to the changes of this area’s grassland ecological environment. In 1987-2007, the fragmentation  of this area’s landscape patterns had an increasing trend, and natural environment and climate change were the main driving forces of land use pattern change. There existed significant differences in the areas of grassland degradation at different altitudes. Grassland degradation mainly occurred at altitudes 4800-5100 m. The grassland degradation area tended to increase with increasing elevation, and the proportions of the degradation area varied greatly over different slopes and aspects. The climate in the study area became warm and dry, and the spatial structure of regional land cover changed obviously. The distribution patterns of grassland degradation at different elevation, position and slope coincided with alpine environment and human disturbances, suggesting that alpine environment and climatic change were the decisive factors to the grassland ecosystem pattern in Yangtze River headwaters area.

Effects of snow cover on the decomposition and nutrient dynamics of Sibiraea angustata leaf litter in western Sichuan plateau, Southwest China.

HU Xia1,2, WU Ning1, WU Yan1, ZUO Wan-qing1, GUO Hai-xia1, WANG Jin-niu1

2012, 23(05):  1226-1232. 

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Soil-borne bag method was adopted to study the decomposition and nutrient dynamics of Sibiraea angustata leaf litter under different depths (0, 30 and 100 cm) of snow cover in western Sichuan plateau in January-May, 2010. In snow-free plot, the mass loss rate of the litter over the five months was 29.9%; in the plots with 30 and 100 cm snow cover, the litter mass loss rate was 33.8% and 35.2%, respectively. During the decomposition, definite N enrichment in the litter was observed, while the P enrichment fluctuated. The C content and C/N ratio of the litter decreased sharply at the early stage of decomposition, but increased gradually after then. Snow cover greatly contributed to the rapid decomposition of litter and the N enrichment in the litter, but had little effects on the litter C and P contents. In western Sichuan plateau, durable snow cover with a depth of >30 cm could alter the litter decomposition pattern, and substantially affect the soil nutrient turnover and plant community composition.

Effects of controlled alternate partial root-zone drip irrigation on apple seedling morphological characteristics and root hydraulic conductivity.

YANG Qi-liang1,2，ZHANG Fu-cang2, LIU Xiao-gang1,2, GE Zhen-yang1

2012, 23(05):  1233-1239. 

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To investigate the effects of alternate partial rootzone drip irrigation (ADI) on the morphological characteristics and root hydraulic conductivity of apple seedlings, three irrigation modes, i.e., fixed partial rootzone drip irrigation (FDI, fixed watering on one side of the seedling root zone), controlled alternate partial rootzone drip irrigation (ADI, alternate watering on both sides of the seedling root zone), and conventional drip irrigation (CDI, watering cling to the seedling base), and three irrigation quotas, i.e., each irrigation amount of FDI and ADI was 10, 20 and 30 mm, and that of CDI was 20, 30 and 40 mm, respectively, were designed. In treatment ADI, the soil moisture content on the both sides of the root zone appeared a repeated alternation of dry and wet process; while in treatment CDI, the soil moisture content had less difference. At the same irrigation quotas, the soil moisture content at the watering sides had no significant difference under the three drip irrigation modes. At irrigation quota 30 mm, the root-shoot ratio, healthy index of seedlings, and root hydraulic conductivity in treatment ADI increased by 31.6% and 47.1%, 34.2% and 53.6%, and 9.0% and 11.0%, respectively, as compared with those in treatments CDI and FDI. The root dry mass and leaf areahad a positive linear correlation with root hydraulic conductivity. It was suggested that controlled alternate partial root-zone drip irrigationhad obvious compensatory effects on the root hydraulic conductivity of apple seedlings, improved the soil water use by the roots, benefited the equilibrated dry matter allocation in seedling organs, and markedly enhanced the root-shoot ratio and healthy index of the seedlings.

Identification of plant species based on DNA barcode technology.

PEI Nan-cai

2012, 23(05):  1240-1246. 

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It is crucial for the studies of taxonomy and biodiversity by using DNA barcode technology to fast and accurately make species identification in the forests across tropics and temperate zones. In this study, the 183 plant species in a 20 hm² subtropical forest plot in Dinghushan (DHS) National Nature Reserve of South China were sampled and sequenced, and the matK, rbcL, and psbA-trnH were employed to generate multilocus barcodes. For the plot, the psbA-trnH possessed the highest integral success rate, i.e., the product of sequencing recovery and correct species identification (75%), followed by matK (70%), and rbcL (56%). A combination of three-locus barcode (matK,rbcL and psbA-trnH) could identify greater than 87% of the total species, followed by two-locus barcode (85% for matK+psbA-trnH, 83% forrbcL+psbA-trnH, and 81% formatK+rbcL). A comparison was made with the previously published results from one subtropical forest plot (LFDP in Puerto Rico, 143 species) and two tropical forest plots (BCI in Panama, 296 species; and NRS in French Guiana, 254 species) to evaluate the universality and species identification correctness of the proposed DNA barcodes for these four forest plots. For the plots in tropics and subtropics, the sequencing success rate ofrbcL,psbA-trnH and matK were 93% and 95.1%, 91.5% and 94.6%, and 68.5% and 79.7%, respectively. The combination ofmatK+rbcL showed a high identification capacity in geographically restricted regions  in taxonomic groups, whereas the three-locus barcode had a high rate of correct species identification both in tropics (84%) and in subtropics (90%).

Features of calcium crystals and calcium components in 54  plant species in salinized habitats of Tianjin.

XU Jing-jing, CI Hua-cong, HE Xing-dong, XUE Ping-ping, ZHAO Xue-lai, GUO Jian-tan, GAO Yu-bao

2012, 23(05):  1247-1253. 

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Plant calcium (Ca) is composed of dissociated Ca²⁺ and easily soluble, slightly soluble, and hard soluble combined Ca salts. The hard soluble Ca salts can often engender Ca crystals. To understand the Ca status in different growth form plants in salinized habitats, 54  plant species were sampled from the salinized habitats in Tianjin, with the Ca crystals examined by microscope and the Ca components determined by sequential fractionation procedure. More Ca crystals were found in 38 of the 54  plant species. In 37 of the 38  plant species, drusy and prismatic Ca oxalate crystals dominated, whereas the cystolith of Ca carbonate crystal only appeared in the leaves of Ficus carica of Moraceae. The statistics according to growth form suggested that deciduous arbors and shrubs had more Ca oxalate crystal, liana had lesser Ca oxalate crystal, and herbs and evergreen arbors had no Ca oxalate crystal. From arbor, shrub, liana to herb, the concentration of HCl-soluble Ca decreased gradually, while that of water soluble Ca was in adverse. The concentration of water soluble Ca in herbs was significantly higher than that in arbors and shrubs. This study showed that in salinized habitats, plant Ca crystals and Ca components differed with plant growth form, and the Ca oxalate in deciduous arbors and shrubs played an important role in withstanding salt stress.

Characteristics of sediment heavy metal pollution in three water supply reservoirs in Huizhou, Guangdong Province of South China.

CHEN Xiu-kang1, ZHANG Hua-jun1, GU Ji-guang1, Hu Ren1, YANG Hao-wen2， CHEN Jing-an3

2012, 23(05):  1254-1262. 

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To understand the present status of the heavy metal (Cr, Cu, Zn, Cd, Pb and Hg) pollution of the sediments in water supply reservoirs in Huizhou, sediment cores were sampled from three representative reservoirs. The heavy metal concentrations were analyzed by ICPMS, and the pollution status was assessed by geo-accumulation index (I_geo) and potential ecological risk index (RI). In the meantime, the possible sources of the heavy metals were analyzed by the principal component analysis (PCA). In the sediments of the three reservoirs, the test heavy metals had different vertical distribution, some had less change, the others decreased or increased with depth, and the distribution patterns differed with the reservoirs. According to the I_geo, the sediments in the reservoirs were seriously polluted by Zn and Pb (Zn: 49.98-640.29 mg·kg^-1; Pb: 21.94-300.66 mg·kg^-1), reaching slight  to high pollution, and the middle or bottom part of the sediments was slightly polluted by Cu (16.85-45.46 mg·kg^-1). On the whole, the sediments were not polluted by Cr, Cd and Hg. According to the RI and the potential ecological risk coefficient [E_r(i)], the sediments in the three reservoirs were under low potential ecological risk. Based on the PCA and relevant information, the human activities such as mining and smelting, urbanization, and agriculture and forestry had great contribution to the heavy metal pollution. The Zn and Pb pollution mainly originated from mining and smelting, Pb pollution also came from motor vehicle exhaust emission and domestic wastes, and Cu pollution mainly derived from agriculture and forestry.

Effects of slope gradient on slope runoff and sediment yield under different single rainfall conditions.

HE Ji-jun1,2, CAI Qiang-guo3, LIU Song-bo4

2012, 23(05):  1263-1268. 

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Based on the field observation data of runoff and sediment yield produced by single rainfall events in runoff plots, this paper analyzed the variation patterns of runoff and sediment yield on the slopes with different gradients under different single rainfall conditions. The differences in the rainfall conditions had little effects on the variation patterns of slope runoff with the gradient. Under the conditions of six different rainfall events in the study area, the variation patterns of slope runoff with the gradient were basically the same, i.e, the runoff increased with increasing gradient, but the increment of the runoff decreased slightly with increasing gradient, which was mainly determined by the infiltration flux of atmospheric precipitation. Rainfall condition played an important role on the slope sediment yield. Generally, there existed a critical slope gradient for slope erosion, but the critical gradient was not a fixed value, which varied with rainfall condition. The critical slope gradient for slope erosion increased with increasing slope gradient. When the critical slope gradient was greater, the variation of slope sediment yield with slope gradient always became larger.

Relationships of rice canopy PAR interception and light use efficiency to grain yield.

TANG Liang, ZHU Xiang-cheng, CAO Meng-ying, CAO Wei-xing, ZHU Yan

2012, 23(05):  1269-1276. 

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Taking two rice cultivars (Liangyoupeijiu and Wuxiangjing 14) with different plant types as test materials, a 2-year field experiment was conducted to study the relationships of rice canopy photosynthetically active radiation (PAR) interception and light use efficiency to grain yield under three planting densities and five nitrogen (N) application rates. From tillering to maturing stage, the average PAR reflectance in all treatments was 3.45%. The ratio of reflected PAR to the total loss of PAR from tillering to heading stage was 10.90%, which was significanlty lower than that (22.06%) from heading to maturiting stage. The PAR conversion efficiency from tillering to maturing stage decreased with increasing planting density but increased with increasing nitrogen rate, and the conversion efficiency was significantly higher from tillering to heading than from heading to maturing stage. The PAR use efficiency from tillering to maturing stage increased with the increase of planting density and nitrogen application rate, and the average PAR use efficiency of Liangyoupeijiu (1.83 g·MJ^-1) was significantly higher than that of Wuxiangjing 14 (1.42 g·MJ^-1). Due to the longer growth period of Wuxiangjing 14, its incident PAR and intercepted PAR under midium and high planting densities were higher, as compared  with Liangyoupeijiu. The grain yield was significantly positively correlated with the canopy PAR interceptance and use efficiency at different growth stages, but less correlated with the PAR conversion efficiency. To increase the canopy PAR use efficiency and conversion efficiency on the basis of maintaining higher PAR interception rate could be an effective way to increase rice yield.

Drought resistance evaluation system for backcross lines of Dongxiang common wild rice (Oryza rufipogonGriff.).

FU Xue-qin1,2, HE Hao-hua1, WEN Piao2, LUO Xiang-dong2, XIE Jian-kun2

2012, 23(05):  1277-1285. 

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A total of 79 rice materials containing Dongxiang wild rice (Oryza rufipogon Griff.) backcross lines (Dwr)/Xie-qingzao B (Xqz B)//Xqz B and their parents were chosen as the test objects to study the relationships between the drought resistance of these materials and the 31 drought resistance indices at germinating stage, seedling stage, booting stage, and mature stage. The results showed that the drought resistance index or the drought resistance coefficient of these materials were significantly correlated to the relative germination energy (RGE) under 15% PEG6000 drought stress, the germination drought resistance index (GDRI) and relative germination energy (RGE) under 20% PEG6000 drought stress, and the relative value of maximum root length (MRL), seeding height (SH), fresh root mass (FRM), dry root mass (DRM), root relative water content (RRWC), wilting rate (WR), leaf soluble sugar content (LSSC), leaf proline content (LPC), leaf MDA content (LMDAC), leaf relative water content (LRWC), level of rolling leaf (RL), plant height (PH), tiller number per plant (TNP), productive tiller number per plant (PTNP), filled spikelets per panicle (FSP), panicle density (PD), seed setting rate (SR), and 1000-grain mass (TGM) under water stress. Through stepwise regression analysis, nine drought resistance indices including the RGE under 20% PEG-6000 drought stress and the relative values of DRM, RRWC, LSSC, LPC, LMDAC, ETNP, SR, and TGM under water stress were selected. Base on these indices and their partial correlation coefficients, the drought resistance evaluation equation (D  value) and evaluation system were established, which could well assess the drought resistance of the Dongxiang common wild rice backcross lines at different growth stages.  

Canopy light distribution and its correlation with photosynthetic production in superhigh yielding cotton fields of Xinjiang, Northwest China

FENG Guo-yi1, YAO Yan-di1, LUO Hong-hai1, ZHANG Ya-li1, DU Ming-wei1, ZHANG Wang-feng1, XIA Dong-li2, DONG Heng-yi2

2012, 23(05):  1286-1294. 

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Taking the super-high yielding cotton fields (lint yield ≥4000 kg·hm^-2) in Xinjiang as the objects, this paper studied the canopy light distribution, photosynthetic rate, and dry matter accumulation at different growth stages, as well as the relationships between the characteristics of canopy light environment and the photosynthetic production. From full flowering stage to late full bolling stage, the light absorption proportion in the upper, middle and lower canopy layers in the superhigh yielding cotton fields was 2:2:1, and the canopy transmission coefficients for radiation penetration and diffuse penetration were 0.20-0.55 and 0.22-0.56, respectively, being at reasonable level. The leaves in the middle and lower canopy layers could well accept light, and the leaf photosynthetic rate had little difference among different canopy layers. Compared with high yielding (3500 kg·hm^-2) and generally high yielding (3000 kg·hm^-2) cotton fields, superhigh yielding cotton field had higher leaf area index and the highest canopy photosynthesis rate at early full bolling stage, and slowly decreased leaf area index, higher canopy photosynthesis rate, increased contribution of nonfoliar organs to photosynthetic production, and larger dry matter accumulation from early boll-opening stage to full boll-opening stage. In cotton cultivation, to adjust the canopy structure for the equidistribution of light and canopy photosynthesis capacity in vertical direction could be the important strategy for the efficient utilization of absorbed light energy and the realization of superhigh yielding.

Maize growth and its responses to heat condition in Northeast China.

YU Wen-ying, JI Rui-peng, FENG Rui, ZHAO Xian-li, ZHANG Yu-shu

2012, 23(05):  1295-1302. 

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Taking 3 maize cultivars (Danyu 39, Yuandan 29, and Longdan 13) as test materials, a field experiment was conducted to study their growth characteristics and responses to air temperature under the conditions of early, medium and late sowing. For the three cultivars, the days from sowing to seedling emergence under early, medium and late sowing were averagely 13, 11 and 8 d, respectively, and the seedling emergence rate was the fastest when the mean air temperature was about 18 ℃. Higher or lower air temperature would decrease the seedling emergence rate. The test cultivars had less difference in the days from seedling to jointing, which was slightly affected by air temperature. Compared with Danyu 39 and Yuandan 29, the latematuring Longdan 13 had an increased growth rate from jointing to mature stage, and thus, the days for mature shortened markedly. For all the three maize cultivars, the days from jointing to mature tended to decrease with increasing air temperature. The dry matter accumulation rate in whole growth period, grain yield, and 100seed mass were in the order of Danyu 39 > Yuandan 29 > Longdan 13.

Salt-alkaline tolerance of sorghum germplasm at seedling stage.

GAO Jian-ming1, XIA Bu-xian1, YUAN Qing-hua2, LUO Feng1, HAN Yun1, GUI Zhi1, PEI Zhong-you1, SUN Shou-jun1

2012, 23(05):  1303-1310. 

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A sand culture experiment with Hoagland solution plus NaCl and Na₂CO₃ was conducted to study the responses of sorghum seedlings to salt-alkaline stress. An assessment method for identifying the salt-alkaline tolerance of sorghum at  seedling stage was established, and the salt-alkaline tolerance of 66 sorghum genotypes was evaluated. At the salt concentrations 8.0-12.5 g·L^-1, there was a great difference in the salt-alkaline tolerance between tolerant genotype ‘TS-185’ and susceptive ‘Tx-622B’, suggesting that this range of salt concentrations was an appropriate one to evaluate the saltalkaline tolerance of sorghum at  seedling stage. At the salt concentrations 10.0 and 12.5 g·L^-1, there existed significant differences in the relative livability, relative fresh mass, and relative height among the 66 genotypes, indicating a great difference in the salt-alkaline tolerance among these genotypes. The genotype ‘Sanchisan’ was highly tolerant, 16 genotypes such as ‘MN-2735’ were tolerant, 32 genotypes such as ‘EARLY HONEY’ were mild tolerant, 16 genotypes such as ‘Tx-622B’ were susceptive, and genotype ‘MN-4588’ was highly susceptive to salt-alkaline stress. Most of the sorghum genotypes belonging to Sudangrasses possessed a high salt-alkaline tolerance, while the sorghum genotypes belonging to maintainer lines were in adverse.

Salt stress tolerance of cucumber-grafted rootstocks.

WANG Li-ping1,2, SUN Jin1, GUO Shi-rong1, LIU Shu-ren1, LIU Chao-jie1, TIAN Jing1

2012, 23(05):  1311-1318. 

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Taking 4 different Cucurbita maxima × C. moschata rootstocks for cucumber (Cucumis sativus) as test materials, a solution culture experiment was conducted to study their growth and antioxidative enzyme activities under the stresses of Ca(NO₃)₂  and NaCl, with the salt stress tolerance of the rootstocks evaluated by subordinate function. At 30 mmol·L_-1 of Ca(NO₃)₂ or 45 mmol·L^-1 of NaCl, the growth of the rootstock seedlings was improved; but at 60 and 120 mmol·L^-1 of Ca(NO₃)₂ or 90 and 180 mmol·L^-1 of NaCl, the growth and the antioxidative systems of the seedlings were inhibited, and the salt injury index of ‘Qingzhen No.1’ was the smallest, with the decrement of biomass and SOD, POD and CAT activities and the increment of relative conductance being significantly lower than those of the others. Under the stress of high concentration Ca(NO₃)₂, the SOD, POD and CAT activities of test rootstocks were higher, and the salt injury index and relative conductance were lower, as compared with those under high concentration NaCl, suggesting that the damage of Ca(NO₃)₂  stress to cucumbergrafted rootstock were smaller than that of NaCl stress. Among the 4 rootstocks, ‘Qingzhen No.1’ had the strongest salt stress tolerance, followed by ‘Zuomu Nangua’, ‘Fengyuan Tiejia’, and ‘Chaoba Nangua’.

Trait stability and test site representativeness of sugarcane varieties based on GGE-biplot analysis.

LUO Jun, ZHANG Hua, DENG Zu-hu, QUE You-xiong

2012, 23(05):  1319-1325. 

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Arithmetic mean method is commonly used to evaluate the yield stability and adaptability of sugarcane varieties, and variance analysis is applied to estimate the errors in regional trials. However, it is difficult to accurately evaluate the differences of the varieties due to the discrepancies across test sites and years. In this paper, GGE-biplot method was adopted to analyze the data from the regional trials with seven sugarcane varieties at five sites from 2008 to 2009, aimed to objectively evaluate the yield stability and adaptability of sugarcane varieties in China. Among the test sugarcane varieties, Funong No.30 had higher cane yield and better yield stability, Yuegan No.18 had higher sugar content and better trait stability, Funong No.28 and Yunzhe 9991 had high sucrose content and trait stability, while Yuegan No.16 had the highest cane yield and sugar content but ordinary stability. In the test sites, Zhangzhou City in Fujian Province and Suixi City in Guangdong Province had the best representativeness and discrimination. This study showed that GGE-biplot analysis provided a simple and effective method to analyze the high yield and stability of sugarcane varieties in regional trials, and supplied the basis for the approval and extension of new sugarcane varieties.

Effects of sowing date and planting density on the seed yield and oil content of winter oilseed rape.

ZHANG Shu-jie, LI Ling, ZHANG Chun-lei

2012, 23(05):  1326-1332. 

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A field experiment was conducted to investigate the effects of different sowing date and planting density on the seed yield and seed oil content of winter oilseed rape (Brassica napus). Sowing date mainly affected the seed yield of branch raceme, while planting density affected the seed yields of both branch raceme and main raceme. The seed oil content was less affected by sowing date. The proportion of the seed yield of main raceme to the seed yield per plant increased with increasing planting density, and the seed oil content of main raceme was about 1% higher than that of branch raceme. Consequently, the seed oil production per plot increased significantly with increasing planting density. In the experimental region, the sowing date of winter oilseed rape should be earlier than midOctober. When sowing in late October, the seed yield would be decreased significantly. A planting density of 36-48 plants·m^-2 could improve the seed yield and oil content of winter oilseed rape.

Effects of UV-B radiation on the growth and reproduction of Vicia angustifolia.

WANG Ying1, WANG Xing-an1, WANG Ren-jun1, QIU Nian-wei1, MA zong-qi1, DU Guo-zhen2

2012, 23(05):  1333-1338. 

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A simulation experiment with supplementation and exclusion of solar ultraviolet-B (UV-B) radiation was conducted to study the effects of enhanced and near ambient UVB radiation on the growth and reproduction of alpine annual pasture Vicia angustifolia on Qinghai-Tibet Plateau. Enhanced UV-B decreased the plant height and biomass, biomass allocation to fruit, flower number, and 100-seed mass significantly, delayed flowering stage, increased the concentration degree of flowering and success rate of reproduction, but had little effect on seed yield. Near ambient UV-B radiation made the plant height increased after an initial decrease, decreased biomass allocation to fruit and 100seed mass, but little affected flowering duration, flower number, and seed yield. Both enhanced and near ambient UV-B radiation could inhibit the growth and production of V. angustifolia, and the effect of enhanced UV-B radiation was even larger.

Genetic diversity of 21 Fusarium strains in Section Martiella based on ISSR analysis.

LI Xin-feng1, ZHANG Guang-ming1, CHANG Yin-dong1, WANG Jian-ming1, LI Rui-qian2, LI Ya-li1

2012, 23(05):  1339-1344. 

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In order to understand the genetic difference and phylogenic relationship within and among the Fusarium species in Section Martiella, the genetic diversity of 21 Fusarium strains in the section was examined by intersimple sequence repeats (ISSR). Fifteen selected ISSR primers were adopted to do amplification, and a total of 239 bands were amplified, among which, 230 (96.2%) were polymorphic, with an average of 15.3 polymorphic bands per primer. The genetic similarity ranged from 0.494 to 0.933, with an average of 0.640. All the test strains were clustered into two groups at genetic similarity of 0.593. The strains 1-17 were grouped into IG-I, belonging to Fusarium solani and F. solani var. coeruleum, while the strains 18-21 were grouped into IG-II, belonging to F. ventricosum. All the 21 strains could be entirely distinguished at genetic similarity of 0.933. The SSR loci in the Fusarium genomes were rich in polymorphism. The ISSR grouping had definite correlation with the species classification, but less correlation with the geographic origin of the strains. Within the same ISSR groups, there existed definite correlation between the genetic similarity and the geographic origin of the strains. Within the same species collected from the same regions and same host plants, there existed definite genetic difference among the strains of the same species.  

Urban heat island intensity and its grading in Liaoning Province of Northeast China.

LI Li-guang1, WANG Hong-bo1, JIA Qing-yu1, LUGuo-hong1, WANG Xiao-ying1, ZHANG Yu-shu1, AI Jing-feng2

2012, 23(05):  1345-1350. 

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According to the recorded air temperature data and their continuity of each weather station, the location of each weather station, the numbers of and the distances among the weather stations, and the records on the weather stations migration,  several weather stations in Liaoning Province were selected as the urban and rural representative stations to study the characteristics of urban heat island (UHI) intensity in the province. Based on the annual and monthly air temperature data of the representative stations, the ranges and amplitudes of the UHI intensity were analyzed, and the grades of the UHI intensity were classified. The Tieling station, Dalian station, Anshan station, Chaoyang station, Dandong station, and Jinzhou station and the 18 stations including Tai’an station were selected as the representative urban and rural weather stations, respectively. In 1980-2009, the changes of the annual UHI intensity in the 6 representative cities differed. The annual UHI intensity in Tieling was in a decreasing trend, while that in the other five cities was in an increasing trend. The UHI intensity was strong in Tieling but weak in Dalian. The changes of the monthly UHI intensity in the 6 representative cities also differed. The distribution of the monthly UHI intensity in Dandong, Jinzhou and Tieling took a “U” shape, with the maximum and minimum appeared in January and in May-August, respectively, indicating that the monthly UHI intensity was strong in winter and weak in summer. The ranges of the annual and monthly UHI intensity in the 6 cities were 0.57-2.15 ℃ and -0.70-4.60 ℃, and the ranges of 0.5-2.0 ℃ accounted for 97.8% and 72.3%, respectively. The UHI intensity in the province could be classified into 4 grades, i.e., weak, strong, stronger and strongest.

Applications of 2D and 3D landscape pattern indices in landscape pattern analysis of mountainous area at county level.

LU Chao1, QI Wei1, LI Le2, SUN Yao1, QIN Tian-tian1, WANG Na-na1

2012, 23(05):  1351-1358. 

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Landscape pattern indices are the commonly used tools for the quantitative analysis of landscape pattern. However, the traditional 2D landscape pattern indices neglect the effects of terrain on landscape, existing definite limitations in quantitatively describing the landscape patterns in mountains areas. Taking the Qixia City, a typical mountainous and hilly region in Shandong Province of East China, as a case, this paper compared the differences between 2D and 3D landscape pattern indices in quantitatively describing the landscape patterns and their dynamic changes in mountainous areas. On the basis of terrain structure analysis, a set of landscape pattern indices were selected, including area and density (class area and mean patch size), edge and shape (edge density, landscape shape index, and fractal dimension of mean patch), diversity (Shannon’s diversity index and evenness index), and gathering and spread (contagion index). There existed obvious differences between the 3D class area, mean patch area, and edge density and the corresponding 2D indices, but no significant differences between the 3D landscape shape index, fractal dimension of mean patch, and Shannon’s diversity index and evenness index and the corresponding 2D indices. The 3D contagion index and 2D contagion index had no difference. Because the 3D landscape pattern indices were calculated by using patch surface area and surface perimeter whereas the 2D landscape pattern indices were calculated by adopting patch projective area and projective perimeter, the 3D landscape pattern indices could be relative accurate and efficient in describing the landscape area, density and borderline,  in mountainous areas. However, there were no distinct differences in describing landscape shape, diversity, and gathering and spread  between the 3D and 2D landscape pattern indices. Generally, by introducing 3D landscape pattern indices to topographic pattern, the description of landscape pattern and its dynamic change would be relatively accurate.

Life table of Leptinotarsa decemlineata (Say) natural population and related affecting factors.

LUO Jin-cang1,2, ZHOU Zhao-xu2, LIU Chang-zhong1

2012, 23(05):  1359-1364. 

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In this study, the life table of the 2nd generation of Leptinotarsa decemlineata (Say) natural population on potato plants was constructed based on functional factor life table method, and the control effects of different factors on the population were analyzed by exclusion analysis method. It was shown that the survival rate of eggs and first instar (79.1% and 69.3%, respectively) was rather lower than that of the L. decemlineata at other growth stages, suggesting that the eggs and first instar larvae were the key stages to control L. decemlineata. Among the controlling factors, “natural death” was the most effective factor, its exclusive index of population control (EIPC) being 187, “predators and others” was in the second place, with the EIPC being 1.51, while “parasitism” had no control effect. The index of population trend  of L. decemlineata would be increased 2.8 times if all natural factors were excluded. It was concluded that natural factors had a certain but weak action on the L.decemlineata population.

Effects of temperature stress on physiological indices of Chilo suppressalis Walker (Lepidoptera: Pyralidae) diapause larvae.

QIANG Cheng-kui1,2,3, DU Yu-zhou1, YU Ling-ya4, QIN Yue-hua2,3, FENG Wu-jian2,3

2012, 23(05):  1365-1369. 

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To understand the physiological mechanisms of temperature stress on the diapause larvae of rice stem borer Chilo suppressalis Walker at physiological and biochemical levels, determinations were made on the contents of water, lipid, total sugar and low molecular mass carbohydrates and the activities of SOD, POD, CAT in the larvae after series temperature stress (STS) and gradient temperature stress (GTS). With the decrease of temperature, the water content in the larvae decreased, and the decrement  below 0 ℃was significantly larger in treatment GTS than in treatment STS. The lipid content in the larvae decreased gradually, but no significant difference was observed between treatments STS and GTS. The total sugar content in the larvae in treatment STS increased after an initial decrease, but that in treatment GTS continued to decline. Four species of low molecular carbohydrates, i.e., rehalose, glucose, glycerol and fructose were detected in the larvae. In treatment STS, the contents of glycose, glycerol and fructose in the larvae decreased after an initial increase, while the  trehalose content was in adverse. In treatment GTS, the trehalose content decreased first and increased then, the glucose and glycerol were in adverse, but the fructose content had little change. In the range from 14 to -14 ℃, the SOD and POD activities in the larvae in treatment STS were significantly lower than those in treatment GTS, but the CAT activity was in adverse. The changes of these indices reflected the physiological responses of C. suppressalisdiapause larvae to different temperature stress.  

Impacts of urbanization on the water quality and macrobenthos community structure of the tributaries in middle reach of Qiantang River, East China.

LIU Dong-xiao1, YU Hai-yan2, LIU Shuo-ru3, HU Zun-ying2,YU jian2, WANG Bei-xin1,3

2012, 23(05):  1370-1376. 

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The 59 1st-3rd order tributaries in the middle reach of Qiantang River are negatively affected by different intensities of urbanization. In April 2010, an investigation was conducted on the water bodies’ physical and chemical properties and macrobenthos communities of the tributaries, with the relationships between the tributaries’ water quality and biological communities and the percentage of ground surface impervious area (PIA), an indicator of urbanization intensity. The Spearman correlation analysis showed that the water bodies’ NH₄⁺-N, PO₄^3--P, TP, COD_Mn, conductivity, width, depth, and fine sand/ silt ratio were positively correlated with PIA, and negatively correlated with forest land area. The fitted nonlinear regression equations revealed that all the test macrobenthic invertebrate’s parameters had significant relationships with PIA, of which, the total number of taxa, Shannon diversity index, richness index, EPT (%), predators (%), shredders (%), filterers (%) and scrapers (%) were negatively correlated to PIA but positively correlated to forest land area, and the BI, ollectors (%), tolerance taxa (%) and oligochaeta (%) were positively correlated to the PIA. Our study indicated that under the impact of urbanization, these tributaries presented the common features of degradation, i.e., high concentrations of nitrogen and phosphorus, degradation of physical habitat, disappearance of pollution-sensitive macro-benthic invertebrate species, and dramatic increase of pollution-tolerant species individuals.

Macrozoobenthos community structure and its indicative significance in water quality bioassessment of Fenshuijiang Reservoir, Zhejiang Province of East China.

LIU Qi-gen1, ZHA Yu-ting1, CHEN Li-qiao2, GU Zhi-min3, JIA Yong-yi3, HU Zhong-jun1

2012, 23(05):  1377-1384. 

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A monthly investigation was conducted on the macrozoobenthos at 7 stations of Fenshuijiang Reservoir in Zhejiang Province of East China from November 2008 to October 2009. A total of 37 taxa were collected, most of which belonged to Oligocheata and Chironomidae. Limnodrilus hoffmeisteri was dominant in spring, summer and autumn, and Chironomus gr. plumosus was prevailing in winter. The  collectorgatherer was the predominant group in  species number, density and biomass. The mean annual density and biomass of the community were (488.0±48.8) ind·m^-2 and (1.86±0.49) g·m^-2, respectively.  There were no significant differences in the macrozoobenthic density among the stations and in the macrozoobenthic biomass among the stations and among the seasons, but the macrozoobenthic density had a significant seasonal variation, with the sequence of spring > summer > winter > autumn.  Water temperature and water depth were the main factors affecting the spatial distribution of the macrozoobenthos.  Shannon index and Goodnight-Whitley index were not suitable for the assessment, whereas the  Wright index, Carlander index,  Pielou index and trophic level index showed that this reservoir was slightly polluted.

Morphological and quality difference of adult Anguilla japonica under three aquaculture models.

WANG Zhi-zheng1, YANG Lei-1, ZHU Wei-dong2

2012, 23(05):  1385-1392. 

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Anguilla japonica adults with a snout-vent length of (25.91±3.26) cm were randomly sampled fromtheponds of monoculture A. japonica (M₁) and olyculture A. japonica and Macrobrachium nipponense(M₂) and the proliferation site in reservoir (M₃) to compare the morphological and quality indices of the adults under the three aquaculture models. Discriminant analysis, cluster analysis, and factor analysis were applied to reveal the differences among the individuals of these three cultured populations. Among the test 21 biological traits and 23 morphological and quality indices, there were significant differences in 15 biological traits and 14 morphological and quality indices between M₁ and M₂, 19 and 18 between M₁ and M₃, and 11 and 8 between M₂ and M₃, respectively. The Euclidean distance between M₁ and M₂, M₁ and M₃, and M₂ and M₃ was 1.433, 3.516, and 2.167, respectively, and the differences were significant. The accumulative variance percentage of the first five〖JP2〗 principal components was 82.1%, and the eigenvalues of these components were all larger than 1. The principal components 1 and 2 could be regarded as fatness factor and movement factor, the other three principal components could be regarded as wellbeing factor, and the three populations could be clearly separated each other by principal component 1. In discriminant analysis, the five principal components, i.e., body width / anal length, body length / anal length, net volume coefficient, swim bladder coefficient, and liver coefficient, were served as independent variables to establish discriminant functions of the populations, which could clearly distinguish the populations, with the discriminant accuracy and synthetic discriminant accuracy being 100%.

Effects of nutritional condition on the competitive parameters of Prorocentrum donghaiense and Skeletonema costatum.

WANG Fang1, GE Wei2, CHAI Chao1, WANG Jin-ye3, ZHAO Xiu-fen1

2012, 23(05):  1393-1399. 

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By the methods of pure culture and mixed culture in laboratory, this paper studied the effects of different substrate nitrogen and phosphorus concentrations on the population growth and interspecific competitive parameters of two kinds of microalgae, Skeletonema costatum and Prorocentrum donghaiens. With the increasing concentrations of substrate nitrogen and phosphorus, the maximum biomass of the two kinds of microalgae increased, and their specific growth rate was higher in pure culture than in mixed culture. In mixed culture, S. costatum was dominant at the beginning, while P. donghaiensebecame dominant later. The time period when this change happened was related to the nutritional conditions, and the inflection point forS. costatum and P. donghaiense was about 0-2.6 and 0.5-4.9 d, respectively. Under the test nutritional conditions, the competitive parameter of P. donghaienseto S. costatum (β) was higher than that of S. costatum toP. donghaiense (α). When the substrate nitrogen and phosphorous concentrations were 128 μmol N·L^-1  and 32 μmol P·L^-1, the competitive capability of P. donghaiense was 3.8 times of that of S. costatum, presenting the most obvious difference.

Water-saving mechanisms of intercropping system in improving cropland water use efficiency.

ZHANG Feng-yun1,2,3， WU Pu-te1,2, ZHAO Xi-ning1,2, CHENG Xue-feng3

2012, 23(05):  1400-1406. 

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Based on the multi-disciplinary researches, and in terms of the transformation efficiency of surface water to soil water, availability of cropland soil water, crop canopy structure, total irrigation volume needed on a given area, and crop yield, this paper discussed the water-saving mechanisms of intercropping system in improving cropland water use efficiency. Intercropping system could promote the full use of cropland water by plant roots, increase the water storage in root zone, reduce the inter-row evaporation and control excessive transpiration, and create a special microclimate advantageous to the plant growth and development. In addition, intercropping system could optimize source-sink relationship, provide a sound foundation for intensively utilizing resources temporally and spatially, and increase the crop yield per unit area greatly without  increase of water consumption, so as to promote the crop water use efficiency effectively.  

Roles of soil dissolved organic carbon in carbon cycling of terrestrial ecosystems: A review.

LI Ling1, QIU Shao-jun2, LIU Jing-tao1, LIU Qing1, LU Zhao-hua1

2012, 23(05):  1407-1414. 

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Soil dissolved organic carbon (DOC) is an active fraction of soil organic carbon pool, playing an important role in the carbon cycling of terrestrial ecosystems. In view of the importance of the carbon cycling, this paper summarized the roles of soil DOC in the soil carbon sequestration and greenhouse gases emission, and in considering of our present ecological and environmental problems such as soil acidification and climate warming, discussed the effects of soil properties, environmental factors, and human activities on the soil DOC as well as the response mechanisms of the DOC. This review could be helpful to the further understanding of the importance of soil DOC in the carbon cycling of terrestrial ecosystems and the reduction of greenhouse gases emission.

Research advances in control of N₂O emission from municipal solid waste landfill sites.

CAI Chuan-yu1,2, LI Bo1,3, LU Hao-hao2,3, WU Wei-xiang1,2

2012, 23(05):  1415-1422. 

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Landfill is one of the main approaches for municipal solid waste treatment, and landfill site is a main emission source of greenhouse gases nitrous oxide (N₂O) and methane (CH₄). As a high-efficient trace greenhouse gas, N₂O has a very high warming potential, with a warming capacity 296 times of CO₂, and has a long-term stability in atmosphere, giving greater damage to the ozone layer. Aiming at the researches in the control of N₂O emission from municipal solid waste landfill sites, this paper summarized the characteristics and related affecting factors of the N₂O emission from the landfill sites, and put forward a series of the measures adaptable to the N₂O emission control of  present municipal solid waste landfill sites in China. Some further research focuses on the control of N₂O emission from the landfill sites were also presented.

Measurement model of carbon emission from forest fire: A review.

HU Hai-qing, WEI Shu-jing, JIN Sen, SUN Long

2012, 23(05):  1423-1434. 

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Forest fire is the main disturbance factor for forest ecosystem, and an important pathway of the decrease of vegetation and soil carbon storage. Large amount of carbonaceous gases in forest fire can release into atmosphere, giving remarkable impacts on the atmospheric carbon balance and global climate change. To scientifically and effectively measure the carbonaceous gases emission from forest fire is of importance in understanding the significance of forest fire in the carbon balance and climate change. This paper reviewed the research progress in the measurement model of carbon emission from forest fire, which covered three critical issues, i.e., measurement methods of forest fire-induced total carbon emission and carbonaceous gases emission, affecting factors and measurement parameters of measurement model, and cause analysis of the uncertainty in the measurement of the carbon emissions. Three path selections to improve the quantitative measurement of the carbon emissions were proposed, i.e., using high resolution remote sensing data and improving algorithm and estimation accuracy of burned area in combining with effective fuel measurement model to improve the accuracy of the estimated fuel load, using high resolution remote sensing images combined with indoor controlled environment experiments, field measurements, and field ground surveys to determine the combustion efficiency, and combining indoor controlled environment experiments with field air sampling to determine the emission factors and emission ratio.