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Table of Content

    18 November 2011, Volume 22 Issue 11
    Articles
    Effect of opening degree regulation on diameter and height increment and aboveground biomass of Korean pine trees planted under secondary forest.
    2011, 22(11):  2781-2791. 
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    Taking mixed forest of artifical Pinus koraiensis and natural broad-leaved trees  as test material, among which the P. koraiensis was 15 (stage I) and 22 (stage Ⅱ) years old respectively, and was in the same succession layer, the height and diameter increment during 4 years experimental period and the aboveground biomass (AGB) at the 4th experimental year for P. koraiensis were measured in the opening degree (K=1.0, 1.5, 2.0) regulation experiment. The periodic increment of basal diameter (BD)/diameter at breast height (DBH), tree height and AGB of P. koraiensis trees were highest in the opening degree K=1.0 treatment. The opening degree K=1.5 and K=2.0 treatments promoted the annual increment of P. koraiensis, with the effect increased along with the experimental period elongation and approached or exceeded that of K=1.0 treatment. The stem biomass proportion of P. koraiensis trees was significantly higher in K=1.0 treatment than that in the other treatments and the control in stage I, but no significant difference among treatments was found in stageⅡ. The ratio of branch to needle biomass in all opening degree treatments was also significantly higher than that in control in stage I, but no significant difference in stage Ⅱ. The proportion and distribution of needles in different ages differed in the two stages. It was concluded that opening degrees of 1.0-2.0 were all suitable for the growth of P. koraiensis of 15-22 years old trees planted  under secondary forest.
    Spatial structural characteristics of natural Populus davidiana - Betula platyphylla secondary forest.
    2011, 22(11):  2792-2798. 
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    This paper analyzed the spatial structural characteristics of natural Populus davidiana - Betula platyphylla secondary forest in a 4 hm2 plot of Mulan Paddock, based on the diameter distribution and the spatial structure parameters mingling degree, neighborhood comparison, and angle index. In the forest, the diameter distribution of the stands presented as an inverse ‘J’ curve, the average mingling degree was 0.4, with the individuals at weak and zero mingling degree reached 51.6%, and the average mingling degree of P. davidiana and B. platyphylla was 0.25 and 0.39, respectively. The neighborhood comparison based on the diameter at breast height (DBH) and tree height was almost the same, suggesting that the P. davidiana and B.platyphylla were in the transition state from subdominant to middle. The horizontal distribution pattern had a close relation to the minimum measured DBH, being clustered when the DBH was ≥1 cm and <6 cm, and random when the DBH was ≥6 cm.
    Spatial distribution pattern of Picea schrenkiana var. tianshanica population and its relationships with topographic factors in middle part of Tianshan Mountain.
    2011, 22(11):  2799-2806. 
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    By the method of point pattern analysis, this paper studied the spatial distribution patterns of different age class individuals in the Picea schrenkiana var. tianshanica forest in middle part of Tianshan Mountain and the influence of topographic factors on the distribution patterns. It was observed that the density of different age class individuals in the forest decreased with the increasing DBH of the individuals, and except old trees which presented a random distribution at the scale of 0-12 m, the saplings and the small, medium, and big trees were in aggregative distribution at all scales. With the increase of age class, the scale at which the individuals presented the highest aggregation degree increased, whereas the aggregation intensity declined. At small scale (0-16 m), different age class individuals appeared negative association, and the greater difference the tree age, the more significant the negative association presented. Altitude had significant positive effects on the number of medium, big, and old trees but had little effects on the number of saplings and small trees. Slope grade had significant positive effects on the number of saplings and small and medium trees, significant negative effects on the number of old trees, but little effects on the number of big trees. Concavo-convex had significant negative effects on the number of saplings and small and medium trees but had little effects on the number of big and old trees.
    Dynamics of Quercus variabilis seed rain and soil seed bank in different habitats on the north slope of Qinling Mountains.
    2011, 22(11):  2807-2814. 
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    In order to explore the dynamics of Quercus variabilis seed rain and soil seed bank in different habitats on the north slope of Qinling Mountains, three kinds of micro-habitats (understory, forest gap, and forest edge) were selected, with the seed rain quantity and quality of Q. variabilis, seed amount and viability in soil seed bank, as well as the seedling development of Q. variabilis studied. The seed rain of Q. variabilis started from mid August, reached the peak in mid September-early October, and ended at the beginning of November, and there existed differences in the dissemination process, occurrence time, and composition of the seed rain among the three micro-habitats. The seed rain had the maximum intensity (39.55±5.56 seeds·m-2) in understory, the seeds had the earliest landing time, the longest lasting duration, and the highest viability in forest gap, and the mature seeds had the largest proportion in forest edge, accounting for 58.7% of the total. From the ending time of seed rain to next August, the total reserve of soil seed bank was the largest in understory and the smallest in forest edge. In the three habitats, the amount of mature and immature seeds, that of seeds eaten by animals, and the seed viability in soil seed bank all decreased with time. In contrast, the number of moldy seeds increased. The seeds were mainly concentrated in litter layer, a few of them were in 0-2 cm soil layer, and few were in 2-5 cm soil layer. The density of the seedlings varied with habitats, being the largest in forest gap, followed by in forest edge, and the least in understory, which suggested that forest gap was more suitable for the seed germination and seedling growth of Q. variabilis, and thus, appropriate thinning should be taken to increase forest gap to provide favorable conditions for the natural regeneration of Q. variabilis forest.
    Phosphorus characteristics in rhizosphere soil of Cunninghamia lanceolata, Pinus massoniana and their mixed plantations.
    2011, 22(11):  2815-2821. 
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    In 2007-2010,a comparative study was conducted on the phosphorus characteristics in the rhizosphere soil of Cunninghamia lanceolata, Pinus massoniana and C.  lanceolata-P. massoniana mixed plantations in a forest farm in Nanping City of Fujian Province, East China. In the rhizosphere soil of pure C. lanceolata and P. massoniana plantations, the content of available P was higher than that in non-rhizosphere soil. As compared with non-rhizosphere soil, the rhizophere soil in the three plantations had lower pH and O-P content but higher Al-P and Fe-P contents, and its P adsorption capacity was lower while the P desorption rate and desorbed P were in adverse. In the rhizophere soil of pure P. massoniana plantation, the contents of available P, Fe-P, and Al-P, their desorption rates, and desorption capacity were higher, but the O-P content and the adsorbed P were lower, as compared with those in the rhizophere soil of pure C. lanceolata plantation. In the mixed plantation, the P activation in rhizophere soil was further improved, being more obvious under C. lanceolata, which suggested that mixed plantation of C. lanceolata and P. massoniana could promote the phosphorus nutrition of C. lanceolata.
    Altitudinal patterns of flower plant biomass on alpine and subalpine meadow in Balang Mountains.
    2011, 22(11):  2822-2828. 
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    A field survey was conducted to study the altitudinal patterns of flower plant biomass on alpine and subalpine meadow in Wolong Nature Reserve in Balang Mountains, and the soil factors were analyzed. With the increase of altitude, the aboveground biomass, including the biomass of flower-fruit, stem, and leaf, varied in unimodal and peaked at 3500 m a.s.l., the belowground biomass varied in U-shape, the soil acidity and the contents of soil hydrolyzable N and total K increased significantly, whereas the contents of soil organic matter, total N, and available P had a significant decrease. The aboveground biomass of the flower plants increased significantly with increasing soil pH and soil total N and available K contents, and the belowground biomass of the plants increased significantly with increasing soil organic matter and available P contents but decreased significantly with increasing soil total K and hydrolyzable N contents.
    Responses of Cynodon dactylon population in hydro-fluctuation belt of Three Gorges Reservoir area to flooding-drying habitat change.
    2011, 22(11):  2829-2835. 
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    This paper studied the population density, morphological characteristics, and biomass and its allocation of Cynodon dactylon at different altitudinal sections of the hydro-fluctuation belt in Three Gorges Reservoir area, based on located observations. At the three altitudinal sections, the population density of C. dactylon was in the order of shallow water section (165-170 m elevation) > non-flooded section (above 172 m elevation) > deep water section (145-150 m elevation), the root diameter and root length were in the order of deep water section > shallow water section > non-flooded section, the total biomass, root biomass, stem biomass, leaf biomass, and stem biomass allocation ratio were in the order of the shallow water section > non-flooded section > deep water section, and the root biomass allocation ratio, leaf biomass allocation ratio, and underground biomass/aboveground biomass were in the order of deep water section > shallow water section > non-flooded section.The unique adaption strategies of C. dactylon to the flooding-drying habitat change in the shallow water section were the accelerated elongation growth and the increased stem biomass allocation, those in the deep water section were the increased node number of primary and secondary branches, increased number of the branches, and increased leaf biomass allocation, whereas the common strategies in the shallow and deep water sections were the accelerated root growth and the increased tillering and underground biomass allocation for preparing nutrition and energy for the rapid growth in terrestrial environment.
    Effects of drought stress and re-watering on the active oxygen scavenging system of Cupressus funebris seedlings in Karst area.
    2011, 22(11):  2836-2840. 
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    This paper studied the active oxygen scavenging system of Cupressus funebris seedlings under drought condition and the recovery capability of the system after re-watering, aimed to understand the adaptation mechanisms of C. funebris to the ‘drought and re-watering’ environment in Karst area. With the increasing time of drought stress, the seedling’s relative water content (RWC) decreased, soluble protein concentration increased first and decreased then, and malondialdehyde (MDA) content increased consistently. The MDA content recovered to the level of the control (CK) when re-watering was implemented within 2 weeks of drought, but could not when the re-watering was made after 4 and 6 weeks of drought. Under drought stress, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) increased consistently. After re-watering, the SOD activity had somewhat decrease but still remained at a higher level than the CK, and the POD and CAT activities decreased to the CK level when suffered mild stress but had less decrement when suffered severe stress. It was concluded that C. funebris seedlings could resist mild drought stress via increasing their soluble protein concentration and inhibiting membrane lipid peroxidation, but could not resist severe drought stress because of the irreversible damage of their membrane structure.
    Effects of altitudinal gradient on Salix atopantha foliar δ13C.
    2011, 22(11):  2841-2848. 
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    In 2010,measurements were conducted on the foliar δ13C, photosynthesis,CO2 diffusive conductivity, nitrogen content, photosynthetic nitrogen use efficiency (PNUE), and special leaf area (SLA) of Salix atopantha at different altitudes (2350 m, 2700 m, 3150 m, and 3530 m) in Wolong Natural Reserve. With the increase of altitude, the foliar nitrogen content (especially the nitrogen content per unit leaf area, Narea) and the PNUE increased, and the foliar δ13C had a significant increase, with an increment of 1.4‰ per 1000 m altitude. The stomatal and mesophyll CO2 diffusion conductance also increased with increasing altitude, which had definite negative effect on the increase of foliar δ13C, but the effect was not strong enough. Comparing with CO2 diffusion conductance, carboxylation capacity was a more important factor limiting the Pc/Pa, and even, the foliar δ13C. At altitude 2350-2700 m, air temperature was the main factor affecting the allocation of nitrogen in S. atopantha photosynthetic system, whereas at altitude 2700-3530 m, light could be the main affecting factor. No significant difference was observed in the SLA at different altitudes.
    Regulation effects of short sunlight on two electron transport pathways in nectarine flower bud during dormancy induction.
    2011, 22(11):  2849-2854. 
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    Taking the nectarine variety ‘Shuguang’ (Prunus persica var.nectariana cv. Shuguang) as test material, and by using respiration inhibitors KCN and SHAM, this paper studied the cytochrome electron transport pathway and the alternative respiration pathway in nectarine flower bud during dormancy induction under the effects of short sunlight. Both the total respiration rate (Vt) and the cytochrome electron transport pathway respiration rate (ρ’Vcyt) presented double hump-shaped variation. Short sunlight brought the first-hump of Vt and ρ’Vcyt forward and delayed the second-hump synchronously, inhibited the ρ’Vcyt, but had no significant effects on the Vt. The capacity (Valt) and activity (ρValt) of alternative respiration pathway also varied in double hump-shape, and the variation was basically in synchronous. Short sunlight made the first climax of Valt and ρValt advanced, but had little effects on the later period climax. The inhibition of cytochrome electron transport pathway and the enhancement of alternative respiration pathway were the important features of nectarine flower bud during dormancy induction, and according to the respective contributions of the two electron transport pathways to the total respiration rate, the cytochrome electron transport pathway was still the main pathway of electron transport, whereas the alternative respiration pathway played an auxiliary and branched role.
    Transcriptional levels of AQPs genes in peach floral buds during dormancy.
    2011, 22(11):  2855-2860. 
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    Taking the floral buds of 10 years old field-cultivated and 3 years old potted nectarine (Prunus persica var. nectarine cv.Shuguang) as test materials, and by the method of real-time quantitative PCR, this paper studied the expressions of the AQPs genes δTIP1 and PIP1;1 during dormancy and dormancy-release (September 15, 2009-January 15, 2010) and the transcriptional levels of the genes under low temperature stress. Within the period of dormancy and dormancy-release, the transcriptional level of PIP1;1 presented a persistent increasing trend, and the high level expression of PIP1;1 in January could be related to the efflux of water through cytoplasma membrane and vacuolar membrane, which protected the bud cells from ice crystal injuries. The contents of soluble sugar, soluble protein, and proline in the bud cells all peaked in January, which prevented the excessive water loss from the cells. After 2 weeks of low temperature treatment, the PIP1;1 had a high level expression, indicating that it was a cold-induced gene. The transcriptional level of δTIP1 fluctuated during dormancy,and increased significantly during dormancy-release,which might be induced by the dormancy-release signals in buds and the resumption of plant activity.After 2 weeks of low temperature treatment, the expression level of δTIP1 had no increase, indicating that δTIP1 was not a cold-induced gene.
    Assessment of rice achievable productivity and its application in rice production management division: A case study in Fuyang County of Zhejiang Province, East China.
    2011, 22(11):  2861-2867. 
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    Rice productivity is the key factor affecting rice production and its sustainable development. Based on the gradation of cultivated land quality at county-level, this paper evaluated the rice productivity in Fuyang County of Zhejiang Province, and, through selected sampling field investigation and according to the land productivity index of paddy field quality, a model for assessing rice achievable productivity was established, aimed to analyze the regional rice productivity and its achievable productivity. In the study area, there was a positive correlation between the land productivity index and rice yield. For single cropping rice, its achievable productivity was 1.70×105 t, being 1.6 times of its realistic productivity (1.04×105 t). In 2009, the realistic rice productivity per unit area was 7676 kg·hm-2, and the achievable productivity was 8831 kg·hm-2, with a production potentiality of +15%, a big potential of rice production capacity in the county. Through the analyses of rice productivity, relative superiority of rice production scale, and its growth potential index in the villages and towns, the rice production of Fuyang County was divided into three regions, i.e., key enhancement region, optimization construction region, and development protection region.
    Responses of rice-wheat rotation system in south Jiangsu to organic-inorganic compound fertilizers.
    2011, 22(11):  2868-2874. 
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    In 2006-2007, a field trial was conducted to study the effects of applying three kinds of organic-inorganic compound fertilizers \[rapeseed cake compost plus inorganic fertilizers (RCC), pig manure compost plus inorganic fertilizers (PMC), and Chinese medicine residues plus inorganic fertilizers (CMC)] on the crop growth and nitrogen (N) use efficiency of rice-wheat rotation system in South Jiangsu. Grain yield of wheat and rice in the different fertilization treatments was significantly higher than the control (no fertilization). In treatments RCC, PMC and CMC, the wheat yield was 13.1%, 32.2% and 39.3% lower than that of the NPK compound fertilizer (CF, 6760kg·hm-2), respectively, but the rice yield (8504-9449 kg·hm-2) was significantly higher than that (7919 kg·hm-2) of CF, with an increment of 7.4%-19.3%. In wheat season, the aboveground dry mass, N accumulation, and  N use efficiency in treatments RCC, PMC, and CMC were lower than those of CF, but in rice season, these parameters were significantly higher than or as the same as CF. In sum, all the test three compound fertilizers had positive effects on the rice yield and its nitrogen use efficiency in the rice-wheat rotation system, being most significant for RCC.
    Oat growth and cation absorption characteristics under salt and alkali stress.
    2011, 22(11):  2875-2882. 
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    This paper monitored the oat growth and cation absorption characteristics on a saline-alkali soil in the Baicheng region of Jilin Province under low, medium, and high levels of salt stress. No significant differences were observed in the shoot growth and yield components under the three levels of salt stress, but the root biomass and root/shoot ratio decreased significantly with increasing salt stress level. At maturing stage, the root/shoot ratio under medium and high salt stresses was 77.2% and 64.5% of that under low salt stress, respectively. Under the three levels of salt stress, the K+/Na+ and Ca2+/Na+ ratios in oat plant had significant differences at trefoil stage, but no significant differences at heading stage. With the increase of salt stress level, the cation absorption selectivity coefficient of oat at filling stage decreased significantly, but the transportation selectivity coefficient had no significant difference under the three levels of  stress. It was concluded that oat could adapt to the salt and alkali stress of soda-alkaline soil to some extent, and the adaptation capability decreased with the increasing level of stress. The decrease of oat root biomass and the stronger ion selective absorption capacity at heading stage under  salt and alkali stress could benefit the shoot growth and yield components of oat.
    Effects of NaCl stress on polyamines metabolism in vegetable soybean.
    2011, 22(11):  2883-2893. 
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    By adopting vermiculite culture, this paper studied the malondialdehyde (MDA) content and polyamines (PAs) metabolism in the seeds of two vegetable soybean cultivars with different salt tolerance under the stress of 100 mmol NaCl·L-1. NaCl stress increased the MDA contents in the seeds of the two cultivars significantly, but the increment was lower for salt-resistant cultivar ‘Lülingtezao’ (LL) than for salt-sensitive cultivar ‘Lixianggaochan 95-1’ (LX). In the whole period of NaCl stress, LL seeds had higher contents of free spermine (Spm), conjugated Spm, conjugated spermidine (Spd),  bound Spd and bound putrescine (Put), higher values of (Spd+Spm)/Put and (cPAs+bPAs)/fPAs, and lower value of Put/PAs, and had higher content of free Spd in the mid and late period (9-15 d) of NaCl stress, as compared with LX seeds. In a longer term (6-15 d) of the stress, LL seeds maintained a higher activity of arginine decarboxylase (ADC) and a lower activity of polyamine oxidase (PAO). All the results suggested that LL seeds had stronger capabilities for polyamines synthesis and for the transformation of Put to Spd and Spm and of free polyamine to conjugated and bound polyamines, which effectively inhibited the membrane lipid peroxidation, possibly being one of the important reasons for the stronger salt tolerance of LL.
    Impacts of suboptimal temperature and low light intensity on the activities and gene expression of photosynthetic enzymes in cucumber seedling leaves.
    2011, 22(11):  2894-2900. 
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    Taking the cucumber cultivar ‘Jinyou 3’ as test material, this paper studied the variations of the mRNA expression and activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), fructose-1,6-bisphosphatase (FBPase), glyceraldehydes-3-phosphate dehydrogenase (GAPDH), fructose-1,6-bisphosphate aldolase (FBA), and transketolase (TK) in cucumber seedling leaves under suboptimal temperature and low light intensity (ST+LL). In the treatment of ST+LL, the leaf area and the dry mass per plant decreased remarkably, compared with the control. On the early days of ST+LL treatment, the gene expression of Rubisco rbcL and rbcS, FBPase, GAPDH, FBA, and TK declined markedly, the activities of the enzymes except TK obviously weakened, and the photosynthetic rate (Pn) decreased rapidly. 3 days later, the gene expression of Rubisco rbcL and rbcS and the initial activity of Rubisco showed a continuous decrease but the decrement was obviously lesser, the total activity of Rubisco and the activities and gene expression of FBPase, GAPDH, FBA, and TK had an increasing trend, and the Pn ascended simultaneously. When the treating time exceeded 6 days, the gene expression and the activities of Rubisco and FBPase tended to be constant, while those of the other enzymes as well as the Pn presented a decreasing trend. These results suggested that the decline of the gene expression and activities of the photosynthetic enzymes in cucumber seedlings under suboptimal temperature and low light intensity was the important reason which led to the decrease of Pn. The adaptation of photosynthetic apparatus in cucumber seedlings to suboptimal temperature and low light intensity was related to the activation mechanisms of photosynthetic enzymes.
    Accumulation characteristics of applied cinnamic acid in cucumber seedling-soil system under NaCl stress.
    2011, 22(11):  2901-2906. 
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    Taking cucumber cultivars‘Jinlv No.5’ (salt-tolerant) and ‘Jinyou No.1’ (salt-sensitive) as test materials, a pot experiment was conducted to study the effects of applying cinnamic acid on the accumulation of applied cinnamic acid in cucumber seedling-soil system under NaCl (585 mg·kg-1 soil) stress. The concentration of applied cinnamic acid was the main factor affecting the accumulation of the exogenous cinnamic acid in the cucumber plant and soil. With the increasing concentration of applied cinnamic acid, except in the treatment of highest concentration (200 mg·kg-1 soil) cinnamic acid, the total content of cinnamic acid in cucumber plant was increased. NaCl stress enhanced the toxicity of cinnamic acid. In the treatments of low and medium concentration cinnamic acid, the cinnamic acid content in cucumber plant increased; whereas in the treatments of high concentration cinnamic acid, the decline of the seedlings growth was observed, and led to the decrease of the cinnamic acid content in the plant. The  content of cinnamic acid in ‘Jinlv No.5’ plant  decreased at the concentration of applied cinnamic acid being >200 mg·kg-1 soil, while that in ‘Jinyou No.1’ started to decrease when the concentration of applied cinnamic acid was >100 mg·kg-1 soil, reflecting the discrepancy in salt tolerance of the two cultivars. For the cucumber plant, its leaf had the highest content of cinnamic acid. In the cucumber seedling-soil system, most of applied cinnamic acid was mainly accumulated in soil.
    Effects of applying calcium on peanut physiological characteristics, its yield and kernel quality under cadmium stress. 
    2011, 22(11):  2907-2912. 
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    Taking high-oil peanut cultivar Yuhua15 and high-protein peanut cultivar XB023 as test materials, a pot experiment was conducted in both 2009 and 2010 to study the effects of applying different concentration calcium (Ca) on the vegetative growth, leaf chlorophyll content, photosynthetic rate, and protective enzyme activities, as well as the yield and kernel quality of the cultivars under cadmium (Cd) stress. Applying Ca alleviated the inhibitory effects of Cd on the height growth of peanut main stem and the length growth of the branches, resulting in the increase of plant dry mass, and mitigated the Cd damage on peanut leaf, manifesting in the increase of leaf chlorophyll content, photosynthetic rate, superoxide dismutase (SOD), peroxidase (POD), and catlase (CAT) activities, and soluble protein content, and the decrease of leaf malondialdeyde (MDA) content. Under the application of Ca, both the pod yield and the kernel yield increased, mainly because of the increase of pod number per plant and of the kernel number per pod. Applying Ca also promoted the transformation of soluble sugar into fat and protein in peanut kernel,increased the kernel fat and protein contents, and improved the kernel quality under Cd stress. Ca application decreased the kernel Cd content of the cultivars, with better effect on Yuhua15 than on XB023.
    Effects of no-tillage and stubble-remaining on soil enzyme activities in broadcasting rice seedlings paddy field.
    2011, 22(11):  2913-2918. 
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    A field experiment was conducted to study the effects of four cultivation modes (conventional tillage, no-tillage, conventional tillage + stubble-remaining, and no-tillage + stubble-remaining) on the activities of urease, acid phosphatase, protease, and cellulose in different soil layers in a broadcasting rice seedlings paddy field. Under the four cultivation modes, the activities of test enzymes were higher in upper than in deeper soil layers, and had a greater difference between the soil layers under no-tillage + stubble-remaining. In upper soil layers, the activities of test enzymes were higher in the treatments of no-tillage than in the treatments of conventional tillage, being the highest under no-tillage + stubble-remaining and the lowest under conventional tillage. In deeper soil layers, the test enzyme activities were the highest under conventional tillage + stubble-remaining, followed by no-tillage + stubble-remaining, no-tillage, and conventional tillage. During the growth period of rice, soil urease and cellulose activities were lower at tillering stage, increased to the maximum at booting stage, and decreased then, soil acid phosphatase activity was higher at tillering stage but lower at elongating stage, whereas soil protease activity peaked at tillering and heading stages.
    Change characteristics of soil available nitrogen and phosphorus and heavy metal contents after long-term cultivation of vegetables.
    2011, 22(11):  2919-2929. 
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    Soil samples were collected from three vegetable fields under different years of cultivation in Changsha suburbs of Hunan Province, South-central China to study the accumulation characteristics, risks, and sources of soil available nitrogen and phosphorus and heavy metals in the fields. With the increasing year of vegetable cultivation, the soil NO3--N, Olsen-P, and heavy metals contents in the fields increased significantly. The average contents of soil NO3--N, Olsen-P, and Cd in the vegetable fields having been cultivated for 1-2 years in Ningxiang County, 10-15 years in Changsha County, and 30 years in Kaifu District were 21.1, 31.9 and 0.33 mg·kg-1, 42.0, 146.9 and 0.52 mg·kg-1, and 49.5, 219.9 and 1.40 mg·kg-1, respectively. The cumulative index (CI) of soil heavy metals generally followed the sequence of Cd >> Cu > Pb > Ni > Zn. Principal component analysis and cluster analysis showed that compared with soil NH4OAc-extracted potassium, pH, organic matter and NH4+-N, that were dominated by natural factors, the soil Olsen-P and NO3--N had the similar accumulation characteristics with the soil heavy metals, being mainly controlled by fertilization. It was considered that the soil environment and health quality of the vegetable fields in Changsha suburbs were not optimistic. The longer the cultivation year of vegetables, the more the soil NO3--N, Olsen-P, and heavy metals accumulated in the fields. The accumulation of these elements in the fields could be primarily due to the long-term fertilization.
    Effects of biochar amendment on cropland soil bulk density, cation exchange capacity, and particulate organic matter content in the North China Plain.
    2011, 22(11):  2930-2934. 
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    A 3-year field experiment with randomized block design was conducted to study the effects of biochar amendment on the soil bulk density, cation exchange capacity (CEC), and particulate organic matter C (POM-C) and N (POM-N) contents in a high-yielding cropland in the North China Plain. Four treatments were installed, i.e., chemical NPK (CK), chemical NPK plus 2250 kg·hm-2 of biochar (C1), chemical NPK plus 4500 kg·hm-2 of biochar (C2), and 750 kg·hm-2 of biochar-based slow release fertilizer (CN). Comparing with CK, treatments C1 and C2 significantly decreased the bulk density of 0-7.5 cm soil layer by 4.5% and 6.0%, respectively, and the treatments with biochar amendment increased the CEC in 0-15 cm soil layer, with an increment of 24.5% in treatment C2. Biochar amendment also increased the C (POM-C) and N (POM-N) contents in 0-7.5 cm soil layer, e.g., the POM-C and N contents in treatment C1 and C2 were 250% and 85%, and 260% and 120% higher than those of the CK, respectively. After three years of biochar amendment, the soil had obvious improvement in its physical and chemical properties, and played more active roles in soil carbon sequestration and greenhouse gases emission reduction.
    Hyper-spectral estimation of soil organic matter content based on wavelet transformation.
    2011, 22(11):  2935-2942. 
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    A total of 60 soil samples with approximate contents of N, P, and K and greatly different content of organic matter were selected by statistical analysis. Through hyper-spectral detection and analysis, the first derivative spectrum of the soil logarithmic reflectance was obtained, and was decomposed by the Bior 1.3 wavelet function. The approximative signal of the lowest frequency and the noise signal of the highest frequency were removed from the input spectrum so as to obtain the characteristic spectrum corresponding to soil physical and chemical parameters. The sensitive bands of soil organic matter were selected by correlation analysis, and the forecasting models were built by multiple regression analysis, based on the sensitive bands and the characteristic spectrum, respectively. Through comparison analysis, the optimal wavelet decomposing resolution for extracting the characteristic spectrum of soil organic matter was ascertained, and the best forecasting model was established. The best wavelet decomposing resolution was 9, followed by 8 and 10. Based on the characteristic spectrum of wavelet de composing of 9 resolutions, the model R2 reached 0.89, which was increased by 0.31 as compared to the model based on sensitive bands, and increased by 0.10 as compared to the model based on the original spectrum.
    Simulation of cropland soil moisture based on an ensemble Kalman filter. 
    2011, 22(11):  2943-2953. 
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    By using an ensemble Kalman filter (EnKF) to assimilate the observed soil moisture data, the modified boreal ecosystem productivity simulator (BEPS) model was adopted to simulate the dynamics of soil moisture in winter wheat root zones at Xuzhou Agro-meteorological Station, Jiangsu Province of China during the growth seasons in 2000-2004. After the assimilation of observed data,the determination coefficient, root mean square error, and average absolute error of simulated soil moisture were in the ranges of 0.626-0.943, 0.018-0.042, and 0.021-0.041, respectively, with the simulation precision improved significantly, as compared with that before assimilation, indicating the applicability of data assimilation in improving the simulation of soil moisture. The experimental results at single point showed that the errors in the forcing data and observations and the frequency and soil depth of the assimilation of observed data all had obvious effects on the simulated soil moisture.
    Radiometers performance attenuation and data correction in long-term observation of total radiation and photosynthetically active radiation in typical forest ecosystems in China.
    2011, 22(11):  2954-2962. 
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    Based on the total radiation and photosynthetically active radiation (PAR) observations with net radiometer (CNR1) and quantum sensor (Li-190SB) in 4 ChinaFLUX forest sites (Changbaishan, Qianyanzhou, Dinghushan, and Xishuangbanna)  in 2003-2008, this paper analyzed the uncertainties and the radiometers performance changes in long-term and continuous field observation. The results showed that the 98% accuracy of the total radiation measured with CNR1 (QCNR1) could satisfy the technical criterion for the sites except Xishuangbanna where the QCNR1 was averagely about 7% lower than QCM11, the radiation measured with high accuracy pyranometer CM11. For most sites, though the temperature had definite effects on the performance of CNR1, the effects were still within the allowable range of the accuracy of the instrument. Besides temperature, the seasonal fog often occurred in tropical rain forests in Xishuangbanna also had effects on the performance of CNR1. Based on the long-term variations of PAR, especially its ratio to total radiation in the 4 sites, it was found that quantum sensor (Li-190SB) had obvious performance attenuation, with the mean annual attenuation rate being about 4%. To correct the observation error caused by Li-190SB, an attempt was made to give a post-correction of the PAR observations, which could basically eliminate the quantum sensor’s performance attenuation due to long-term field measurement.
    Simulation of Larix gmelinii tree volume growth based on random effect.
    2011, 22(11):  2963-2969. 
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    Based on the stem analysis data of 80 sample trees in dahurian larch (Larix gmelinii) plantations of Daqingchuan Forest Farm, Dailing Forest Bureau in Heilongjiang Province and the Logistic growth model, the NLME procedure of S-PLUS software was adopted to fit the nonlinear tree volume growth models, with consideration of individual tree effect and plot effect, and the evaluation statistics such as AIC, BIC, Log Likelihood, and likelihood ratio test were used to compare the prediction precisions of the models. The results showed that the random effect models with parameters b1, b2, and b3(representing the random parameters for progressive, scale, and shape in Logistic model, respectively) had the best performance when considering individual tree effect, while the models with parameter b1 had the best performance when considering plot effect. The models considering both individual tree effect and plot effect provided better model fitting than the basic model (Logistic growth model), and the models considering individual tree effect showed more precision, as compared with those considering plot effect. The model validation indicated that random effect models not only showed the mean variation trend of individual tree volume growth, but also showed the differences among the individuals. In addition, the prediction precision of the models could be further improved through the calibration of random parameters.
    Prediction of potential distribution area of Erigeron philadelphicus in China based on MaxEnt model.
    2011, 22(11):  2970-2976. 
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     Erigeron philadelphicus, an alien weed originated from North America, has already invaded in Shanghai, Jiangsu, Anhui, and some other places in China, caused harm on local ecosystem and demonstrated huge potential invasiveness. By using MaxEnt model and geographic information system (GIS), this paper analyzed the environmental variables affecting the distribution of E. philadelphicus, and intuitively and quantitatively predicted its potential distribution regions in China. The prediction was verified by the ROC curve, and the results showed that E. philadelphicus had a wide potential distribution range, with the main suitable distribution area in Shanghai, Jiangsu, Zhejiang, Anhui, Henan, Hubei, Hunan and Jiangxi. At present, the actual invasive range of E. philadelphicus was far narrower than its potential maximum invasive range, and likely to be continued to spread. The ROC curve test indicated that the prediction with MaxEnt model had a higher precision, and was credible. Air temperature and precipitation could be the main environmental variables affecting the potential distribution of E. philadelphicus. More attentions should be addressed to the harmfulness of the weed. To eradicate the existing E. philadelphicus populations and to strictly monitor the invasion ofE. philadelphicus to its most suitable distribution area could be the effective measures to prevent and control the further invasion of the alien weed.
    Risk assessment of coastal ecosystem in Beibu Gulf, Guangxi of South China.
    2011, 22(11):  2977-2986. 
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    Based on the marine ecological investigation in the coastal area of Beibu Gulf, Guangxi in September 2009, a GIS-based evaluation was conducted on the present status of ecological environment quality, including seawater quality, nutrient level, biomass, primary productivity, biodiversity, and ecological buffer capacity, in the area in autumn,and the integrated ecological risk index (ERI) was adopted to assess the risk of the coastal ecosystem in the Gulf. In September 2009, the study area had a better ecological environment quality. Most of the risk indicators were at medium or lower level, and the total area was overall at low ecological risk level. The ERI showed that there was an obvious spatial heterogeneity in the distribution of the ecological risk. The nearer to the harbors, the higher the risk was.
    Integrated assessment of eco-environmental vulnerability in Pearl River Delta based on RS and GIS.
    2011, 22(11):  2987-2995. 
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    Based on the remote sensing data and with the help of geographic information system, an integrated assessment was conducted on the eco-environmental vulnerability of Pearl River Delta in 2004-2008. Spatial principal component analysis was used to generate the evaluation indicators, and analytic hierarchy process (AHP) was applied to determine the weights of the evaluation factors. The reasons causing the vulnerability of the eco-environment in Pearl River Delta were discussed. In the study area, its middle part was the most vulnerable region, occupying 34.0% of the total, eastern part was the moderately vulnerable region, accounting for 25.5%, and western part was the lightly and slightly vulnerable areas, accounting for 28.7 and 11.8%, respectively. Totally, the moderately and lightly vulnerable areas occupied 54.2%, indicating that a majority of the Delta was under moderate and light vulnerability. The natural factors affecting the eco-environmental vulnerability of the Delta were altitude, heavy rain days, water and soil erosion rate,flooded infield rate,normalized difference vegetation index (NDVI) and landscape diversity index, whereas the human factors were population density,waste discharge per unit area, exhaust emission per unit area, land use change, chemical fertilization intensity, pesticide application intensity, amount of motor vehicles possessed by ten thousands people, and index of environmental protection investment. The main characteristics of the extremely and heavily vulnerable regions were low altitude, high frequency of flood disaster, large flooded infield, serious vegetation degradation, high pollution level and low environment protection investment index.
    Abundance of archaea, crenarchaea and bacteria in selected agricultural soils of China.
    2011, 22(11):  2996-3002. 
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    Eukaryota, bacteria and archaea are the three domains of life. As the third domain of life, archaea has been found not only in extreme environments such as high-temperature, high-saline, and extremely acid habitats, but also in moderate environments including ocean, lake and soil, which implies that archaea may contribute greatly to various ecosystems. By targeting the 16S rRNA gene with real-time PCR approaches, this paper studied the abundance of archaea, crenarchaea and bacteria from two agricultural soil profiles and two long-term fertilization stations Qiyang (QY) and Fengqiu (FQ). The 16S rRNA gene copy number of crenarchaea was 1-2 orders of magnitude lower than that of archaea, and the order of these three groups was crenarchaea < archaea < bacteria. The ratios of both archaea and crenarchaea to bacteria increased with soil depth. The abundance of archaea and  crenarchaea had significantly different responses to different fertilization treatments. In QY station, the copy numbers of archaeal and bacterial 16S rRNA gene had significant positive correlations with soil pH (r=0.850, P<0.01 and r=0.676, P<0.05, respectively); in FQ station, all the 16S rRNA gene copy numbers of archaea, crenarchaea and bacteria had no significant correlations with soil pH, but significantly correlated with soil organic matter (r=0.783, P<0.05;r=0.827,P<0.05;r=0.767, P<0.05, respectively). To understand the distribution of archaea and crenarchaea in agricultural soil could provide important information to evaluate their ecological functions in soil ecosystem and element cycling.
    Distribution and characteristics of soil antagonistic actinomycetes on northern slope of Taibai Mountain,  Qinling.
    2011, 22(11):  3003-3010. 
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    Twelve representative soil samples were collected from different altitudes on the northern slope of Taibai Mountain to study the distribution and characteristics of soil antagonistic actinomyces by using agar block method. There existed a great deal of soil antagonistic actinomyces in the study area. Among the 141 actinomycete strains isolated,116 strains (82.3%) showed antagonism toward 12 target bacteria or fungi.The antagonistic strains at altitudes 800-1845, 3488,3655, and 3670 m occupied 73.7%-86.8%,81.3%, 78.9% and 82.3% of the total, respectively. 42.1% of the strains at altitudes 1200-2300 m and >3400 m showed strong and broad spectrum antagonistic activity, suggesting that there was a great potential for the isolation of actinomycete strains with strong anti-biotic capability at these altitudes.  24.1% of the antagonistic actinomycetes showed antagonism against Staphyloccocus aureu, and 2.4%, 6.9% and 11.2% of them showed activity toward Verticillium dahliae in cotton,Phytophthora sp. in strawberry and Neonectria radiciccla in ginseng, respectively. This study showed that  the soil actinomycete antagonistic potentiality (SAAP) could be used as a quantitative indicator to evaluate the potential of antagonistic actinomycete resources in soil.
    Characteristics of floor litter and soil arthropod community in different types of subtropical forest in Ailao Mountain of Yunnan, Southwest China.
    2011, 22(11):  3011-3020. 
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    By using line transect method, an investigation was conducted on the floor litter and soil arthropod community in a mid mountain wet evergreen broad-leaved forest, a mossy dwarf forest, and a Populus bonatii forest in Ailao Mountain of Yunnan in April (dry and hot season), June (rainy season), and December (dry and cold season), 2005. In both dry and rainy seasons, the existing floor litter mass,  C storage, and C/N ratio in the three forests all increased in the order of mossy dwarf forest > P. bonatii forest > evergreen broad-leaved forest, but the N storage had less difference. In the floor litter layer of the forests, Acari and Collembola were the dominant groups of soil arthropod community, while Diptera larvae, Coleoptera, ants, and Homoptera were the common groups. The Sorenson coefficients of soil arthropod community in the three forests were extremely great. No significant differences were observed in the soil arthropod density (ind·m-2)  in the floor litter layer among the three forests, but the relative density (ind·g-1) of soil arthropods was higher in the evergreen broad-leaved forest and P.bonatii forest than in the mossy dwarf forest. In the three forests, the density of soil arthropods was significantly higher in dry season than in rainy season, but the Shannon diversity index had less difference. There were significant positive correlations between the existing floor litter mass and the individual density (ind·m-2) and dominant groups of soil arthropod communities in dry and hot season (April), but negative correlations between the existing floor litter mass and the relative density (ind·g-1) of soil arthropod communities and Acari in dry and cold season (December). The individual densities of Collembola and Coleoptera also had positive correlations with the N storage of the existing floor litter mass in the three forests. It was considered that the floor litter and the development of soil arthropod community in the litter layer of the subtropical forests in Ailao Mountain had a close relation with the vegetation structure of the forests, and the individual density and the diversity of the soil arthropod community were controlled by the floor litter, whereas the environmental factors such as temperature and moisture in the forests also had obvious effects on the seasonal dynamics of the individual density of the soil arthropods.
    Occurrence dynamics of migratory pest insects Cnaphalocrocis medinalis and Sogatella furcifera in transgenic Bt rice field in Xing’an County of Guangxi Province. 
    2011, 22(11):  3021-3025. 
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    An investigation was conducted in Xing’an County of Guangxi Province in 2010 to study the occurrence and damage characteristics of two unique migratory pest insects, rice leaffolder (Cnaphalocrocis medinalis) and white-backed planthopper (Sogatella furcifera), in a transgenic Bt rice (cv. HH1 with dual Cry1Ab+Cry1Ac genes) field, taking the corresponding non-transgenic parent (cv. MH63) field as the control. No significant differences were observed in the abundance of C. medinalis eggs and larvae in the two fields, but the percentage of fold-leaf plants and the fold-leaf rate per plant were significantly lower in transgenic Bt rice field than in the control, suggesting that transgenic Bt rice had higher resistance against the target pest insect C. medinalis. As for S. furcifera, its occurrence dynamics of nymphs, adults (including macro- and brachypterous forms), and whole population had no significant differences between the two fields, but the abundance of the nymphs and brachypterous adults at the peak stage of S. furcifera occurrence was obviously higher in transgenic Bt rice field than in the control, while the macropterous abundance was in adverse. The  sex ratio of female of the macropterous adults at the late growth stage of rice was generally lower in transgenic Bt rice field than in the control. These results suggested that under the background of large area commercial production of transgenic Bt rice, the occurrence and harm of the non-target pest insect S. furcifera could become more complicated.
    Toxicity and bioactivity of several alternative nematocides against Ditylenchus destructor.
    2011, 22(11):  3026-3032. 
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    By the methods of fumigation and contact assay, this paper determined the toxicity of four kinds of soil fumigants and six kinds of non-fumigants against Ditylenchus destructor. In the meantime, the bioactivity of the agents was evaluated by the corrected mortality rate of D. destructor after treated with the LC50 dose of each agent for different time. The LC50 values of soil fumigants dazomet, 1,3-dichloropropene, metham-sodium, and chloropicrin were 0.49, 0.89, 0.91, and 3.60 mg·L-1, and those of non-fumigants emamectin benzoate, abamectin, ethoprophos, fosthiazate, aldicarb, and carbosulfan were 31.2, 48.1, 224.3, 288.4, 632.3, and 823.9 mg·L-1, respectively. The corrected mortality rate increased with treating time. After treated with LC50 dose, the inhibitory effects of dazomet, 1,3-dichloropropene, abamectin, and emamectin benzoate kept on a higher level at the time, and the corrected mortality rate did not decline after breaking away from the treatment, but the D. destructor recovered when exposed to natural state after treated with ethoprophos and aldicarb for 48h. It was suggested that dazomet, 1,3-dichloropropene, abamectin, and emamectin benzoate were the potential alternative nematicides used for the control of D. destructor.
    Control effects of Ricinus communis extracts on Meloidogyne incognita.
    2011, 22(11):  3033-3038. 
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    Toxicity test and pot experiment were conducted to study the nematocidal activity and control effects of Ricinus communis extracts on Meloidogyne incognita. The results showed that both the ricinine and the R. communis water extracts had high nematocidal activity. The ricinine at concentration 2 g·L-1 and treated for 48 hours had the strongest nematocidal activity, leading to 91.5% of corrected mortality of M. incognita and with the LC50 being 0.6 g·L-1, whereas the R. communis water extracts at concentration 100 g·L-1 and treated for 48 hours had the strongest nematocidal activity, which led to 83.5% of corrected mortality of M. incognita, and the LC50 was 18.3 g·L-1. With the inoculation of M. incognita treated with ricinine, R. communis water extracts, and R. communis leaf powder, respectively, on tomato seedlings, the mean number of plant root-knots was 17.6±1.7, 20.6±1.5 and 22.8±3.7, respectively, being significantly lower than the control (37.4±2.3), and the root length  increased by 46.8%, 34.5% and 33.8%, and the plant height  increased by 33.5%, 22.6% and 15.8%, and the fresh mass  increased by 41.4%, 18.9% and 10.1%, respectively,  compared with the control. All the results suggested that R. communis extracts could mitigate the harm of M. incognita, and had obvious effects on potted tomato against M. incognita.
    Genetic differentiation of Isaria farinosa populations in Anhui Province of East China.
    2011, 22(11):  3039-3046. 
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    Isaria farinosa is an important entomopathogenic fungus. By using ISSR, this paper studied the genetic heterogeneity of six I. farinosa populations at different localities of Anhui Province, East China. A total of 98.5% polymorphic loci were amplified with ten polymorphic primers, but the polymorphism at population level varied greatly, within the range of 59.6%-93.2%. The genetic differentiation index (Gst) between the populations based on Nei’s genetic heterogenesis analysis was 0.3365, and the gene flow (Nm) was 0.4931. The genetic differentiation between the populations was lower than that within the populations, suggesting that the genetic variation of I. farinosa mainly come from the interior of the populations. The UPGMA clustering based on the genetic similarities between the isolates revealed that the Xishan population was monophylectic, while the other five populations were polyphylectic, with the Yaoluoping population being the most heterogenic and the Langyashan population being the least heterogenic. No correlations were observed between the geographic distance and the genetic distance of the populations.According to the UPGMA clustering based on the genetic distance between the populations, the six populations were classified into three groups, and this classification was accorded with the clustering based on geographic environment, suggesting the effects of environmental heterogeneity on the population heterogeneity.
    Genetic diversity of introduced natural enemy Agasicles hygrophila (Coleoptera: Chrysomelidae). 
    2011, 22(11):  3047-3052. 
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    Flea beetle Agasicles hygrophila Selman & Vogt, the most effective natural enemy of alligator weed Alternanthera philoxeroideis, is originated from South America, and has been introduced into China for more than 20 years to control the weed. In this study, the technique of  random amplification of polymorphic DNA (RAPD) was applied to assess the genetic diversity of four A. hygrophila geographic populations in Guangzhou, Chongqing, Kunming, and Fuzhou of China,and, taking the population in Florida of US as the reference, the relationships between the genetic differentiation and geographic differentiation among and within the populations were explored at molecular level. Thirteen primers that produced clear and reproducible products were selected from 111 random primers to amplify the 25 samples of the five A. hygrophila populations. The total polymorphic rate was 42.0%, and the polymorphic rate of Florida population was significantly higher than that of four China populations. The genetic differentiation among the four China populations was 25.5%. The cluster analysis by UPGMA indicated that there was a positive correlation between the genetic distance and geographic distance of different A. hygrophila geographic populations.
    Spatial distribution pattern and time series dynamics of Panonychus ulmi Koch in an apple orchard of Liaoning Province, Northeast China.
    2011, 22(11):  3053-3059. 
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    Panonychus ulmi Koch is one of the important pest insects of apple production in China. To clarify the spatiotemporal dynamics of P. ulmi on the apple tree crowns in an apple orchard of Liaoning, Northeast China, an investigation with random sampling was conducted on the pest mite number at each direction and each layer of the crowns in the whole growth season from May to November 2007. The spatial distribution pattern and time series dynamics of  P. ulmi were analyzed by calculating the indices of aggregation and using the parameters of Iwao model. In the early and mid growth periods of apple tree,  P. ulmi  within whole crown fitted negative binomial distribution, presented an aggregated pattern, and its fundamental component was the group composed of several individuals that attracted each other. The aggregation intensity showed a negative fluctuation with population density, namely, high population density but low patchiness density, and low population density but high patchiness density, and there existed definite differences at different crown directions and layers, i.e., the patchiness density was the highest in south direction and the lowest in west direction, and was higher in mid and lower layers than in upper layer, and in inner layer than in outer layer.
    Research progress in seegrass seed dormancy, germination, and seedling growth and related affecting factors.
    2011, 22(11):  3060-3066. 
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    Seagrass bed is the main primary producer in coastal areas, having highly ecological and economical values, and being one of the most important shallow-marine ecosystems. This paper reviewed the research progress in the seed dormancy, germination, and seedling growth of seagrass and related affecting factors, summarized the seed dormancy modes and durations and their affecting factors, and discussed the effects of water salinity, temperature, transparency, hormone, dissolved oxygen, and population structure on the seed germination and the seedling survival and growth. Some issues in related researches and several research directions in the future were prospected.
    Multiple functions-targeted algorithms and potential applications of Forest Simulation Optimization System (FSOS).
    2011, 22(11):  3067-3072. 
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    Forest Simulation and Optimization System (FSOS) model has been widely used in British Columbia of Canada and in Changbai Mountains of China. This model is based on the viewpoint of harmonized and balanced management of forest resources and the application of simulated annealing optimized algorithms in arranging forest management schemes, aimed to realize the sustainable and harmonized development of forest resources multiple objective management and to transform forests to their desired status. The multiple functions (or the multiple objectives) in the FSOS model include water storage and purification, carbon sequestration, wildlife habitat protection, biodiversity conservation, visual landscape quality, and timber production, and the desired forest status is comprehensively defined by experts, environmental organizations, and government policies. This paper introduced in detail the simulated annealing algorithms in FSOS, including solution representation, evaluation, and transitions,and the potential applications of the algorithms in forest ecosystem planning, aimed to provide helps to the planning and management of forest resources and to the governments to quantify, analyze, and manage the forest resources, effectively monitor forest operations, and achieve the sustainable development of forest ecosystem.
    Baseflow separation methods in hydrological process research: A review.
    2011, 22(11):  3073-3080. 
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    Baseflow separation research is regarded as one of the most important and difficult issues in hydrology and ecohydrology, but lacked of unified standards in the concepts and methods. This paper introduced the theories of baseflow separation based on the definitions of baseflow components, and analyzed the development course of different baseflow separation methods. Among the methods developed, graph separation method is simple and applicable but arbitrary, balance method accords with hydrological mechanism but is difficult in application, whereas time series separation method and isotopic method can overcome the subjective and arbitrary defects caused by graph separation method, and thus can obtain the baseflow procedure quickly and efficiently. In recent years, hydrological modeling, digital filtering, and isotopic method are the main methods used for baseflow separation.
    Effects of temperature and salinity on oxygen consumption rate and asphyxiation point of Sagitta crassa.
    2011, 22(11):  3081-3086. 
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    A laboratory test was conducted to study the effects of different temperature and salinity on the oxygen consumption rate and asphyxiation point of chaetognath Sagitta crassa. Both temperature and salinity had significant effects on the oxygen consumption rate (IO) and specific oxygen consumption rate (SO) of S. crassa. When the temperature raised from 5 ℃ to 25 ℃, the IO and SO of S. crassa increased first, and then presented an obvious decreasing trend, with the  regression function being y=0.0058x3-0.2956x2+4.415x-8.7816(R2=0.99,P<0.05) for IO and y=0.0011x3-0.0546x2+0.8161x-1.6232(R2=0.99,P<0.05) for SO. The IO and SO at different temperature were in the ranges of 6.30-11.71 μg·ind-1·h-1 and 1.22-2.16 μg·mg-1·h-1, respectively, and the asphyxiation point was 4.18-6.87 mg·L-1. When the salinity increased from 10 to 40, the IO and SO of S. crassa decreased gradually, with the  regression function being y=-0.0068x2-0.1412x+21.702(R2=0.89,P<0.05)for IO and y=-0.0013x2-0.0261x+4.0114(R2=0.89,P<0.05) for SO. The IO and SO at different salinity were in the ranges of 4.98-17.73 μg·ind-1·h-1 and 0.92-3.56 μg·mg-1·h-1, respectively, and the asphyxiation point was 4.02-6.24 mg·L-1. Based on the differences in the oxygen consumption rate and asphyxiation point between S. crassa and other aquatic animals, it was concluded that S. crassa was a stenooxybiotic zooplankton species.