Table of Content

20 November 2009, Volume 20 Issue 11

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Articles

Dynamic changes of topsoil organic carbon in subalpine spruce plantation at different succession stages in western Sichuan Province

2009, 20(11):  2581-2587. 

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Soil samples at 0-30 cm depth were collected from the primary spruce (Picea asperata) forest and its plantations at different succession stages (22-, 47-, and 65-year-old) in subalpine zone of western Sichuan Province to study the dynamic changes of soil organic carbon stock and labile organic ca
rbon content. The soil total organic carbon (TOC) stocks in 0-10, 10-20, and 20-30 cm soil layers decreased from 95.87, 79.08, and 71.55 t·hm^-2 in 22-year-old plantation to 56.12, 34.75, and 31.06 t·hm^-2 in 65-year-old plantation, respectively, and the TOC stocks in these soil layers in 47 and 65-year-old plantations were less than those (88.08, 71.16 and 64.81 t·hm^-2, respectively) in primary forest. The easily oxidizable organic carbon (EOC) ontents in 0-10, 10-20, and 20-30 cm soil layers decreased from 35.89, 26.91, and 26.00 g·kg^-1 in primary forest to 20.25, 14.50, and 12.36 g·kg^-1 in 65-year-old plantation, the microbial biomass carbon (MBC) contents decreased from 524.44, 273.26, and 257.97 mg·kg^-1 in primary forest to 312.41, 186.95, and 152.18 mg·kg^-1 in 65-year-old plantation, and the particulate organic carbon (POC) contents decreased from 40.23, 27.10, and 19.55 g·kg^-1 in rimary forest to 12.33, 7.31, and 5.32 g·kg^-1 in 65-year-old plantation, respectively. The results suggested that within the long succession period of primary P. asperata forest to its plantations in the subalpine zone of western Sichuan Province, soil TOC and labile organic carbon were in the state of net consumption.

Effects of simulated nitrogen deposition on litter decomposition in Neosinocalamus affinis stands in rainy area of West China

2009, 20(11):  2588-2593. 

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An in situ experiment was conducted to study the effects of simulated nitrogen deposition on the litter decomposition in Neosinocalamus affinis stands in rainy area of West China. Four treatments were installed, i.e., null N (CK, 0 kg·hm^-2·a^-1), low N (LN, 50 kg·hm^-2·a^-1), medium N (MN, 150 kg·hm^-2·a^-1), and high N (HN, 300 kg·hm^-2·a^-1). Among the litters, leaf had the highest decomposition rate, followed by sheath, and twig, with a remaining rate aft
er decomposing for 15 months being 26.38%, 46.18%, and 54.54%, respectively (P<0.01). Leaf litter decomposed faster during the first 2 months and the 7^th-10^th month, while the decomposition of sheath and twig was faster from the 5^th to the 8^th month. It took 2.573 years to decompose 95% of l
eaf litter mass, 1.686 years and 3.319 years shorter than that of sheath and twig, respectively. After 15 months decomposition of leaf litter, no significant differences were observed among different treatments. To decompose 95% of sheath litter needed 2.679-4.259 years, being the longest in CK and the shortest in treatment MN. After decomposing for 15 months, the decomposition rate of twig litter was in the order MN>HN>LN>CK, and significant difference existed between treatments MN and LN. Nitrogen deposition had obvious promotion effect on the litter decomposition in the N. affinis stands, but this effect decreased with increasing deposited N concentration and time extension.

Net CO₂ exchange and carbon isotope flux in Acacia mangium plantation

2009, 20(11):  2594-2602. 

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By using stable carbon isotope technique, the leaf-level ¹³C discrimination was integrated to canopy-scale photosynthetic discrimination (Δ_canopy) through weighted the net CO₂ assimilation (A_net) of sunlit and shaded leaves and the stand leaf area index (L) in an A. mangium plantation, and the carbon isotope fluxes from photosynthesis and respiration as well as their net exchange flux were obtained. There was an obvious diurnal variation in Δ_canopy, being lower at dawn and at noon time (18.47‰ and 19.87‰, respectively) and the highest (21.21‰) at dusk. From the end of November to next May, the Δ_canopy had an increasing trend, with an annual average of (20.37±0.29)‰. The carbon isotope ratios of CO₂ from autotrophic respiration (excluding daytime foliar respiration) and heterotrophic respiration were respectively (-28.70±0.75) ‰ and (-26.75±1.3)‰ in average. The δ¹³C of nighttime ecosystem-respired CO₂ in May was the lowest (-30.14‰), while that in November was the highest (-28.01‰). The carbon isotope flux of CO₂ between A. mangium forest and atmosphere showed a midday peak of 178.5 and 217 μmol·m^-2·s^-1·‰ in May and July, with the daily average of 638.4 and 873.2 μmol·m^-2·s^-1·‰, respectively. The carbon isotope flux of CO₂ absorbed by canopy leaves was 1.6-2.5 times higher than that of CO₂ emitted from respiration, suggesting that a large sum of CO₂ was absorbed by A. mangium, which decreased the atmospheric CO₂ concentration and improved the environment.

Design of dynamic simulation system for carbon cycle in forest ecosystem

2009, 20(11):  2603-2609. 

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Modeling techniques are indispensable for the researches on the carbon cycle of forest ecosystem. In this paper, a new general simulation system FORCASS (FORest CArbon Simulation System) was designed and developed under Simulink environment, with the objectives of modeling the carbon cycle dynamics of forest ecosystems. A comprehensive analysis on the framework, design solution, and development process showed that the FORCASS was feasible. This simulation system had the characteristics of 1) it divided the carbon storage in forest ecosystem into four compartments, i.e., vegetation, litter, soil, and animal, and took into account the carbon flows between the compartments, possessing high mechanism and
easily to be comprehended, 2) it was a processbased system, taking the Richards growth function of vegetation component biomass carbon storage as the input to solve difference equations, and was easily to export the outputs such as net primary productivity (NPP) and net ecosystem productivity (NEP) at different stand ages, and 3) it had the explicit expansibility because it was developed based on a general framework for carbon cycle patterns.

Construction and application of probability distribution model for mixed forests tree measurement factors

2009, 20(11):  2610-2616. 

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Aiming at the deficiencies in the researches about the probability distribution model for mixed forests tree measurement factors, a joint maximum entr
opy probability density function was put forward, based on the maximum entropy principle. This function had the characteristics of 1) each element of the function was linked to the maximum entropy function, and hence, could integrate the information about the probability distribution of measurement factors of main tree species in mixed forests, 2) the function had a probability expression of doubleweight, being possible to reflect the characteristics of the complex structure of mixed forests, and accurately and completely reflect the probability distribution of tree measurement factors of mixed forests based on the fully use of the information about the probability distribution of measurement factors of main tree species in mixed forests, and 3) the joint maximum entropy probability density function was succinct in structure and excellent in performance. The model was applied and tested in two sampling plots in Tianmu Mountain Nature Reserve. The fitting precision (R²=0.9655) and testing accuracy (R²=0.9772) were both high, suggesting that this model could be used as a probability distribution model for mixed forests tree measurement factors, and provided a feasible method to fully understand the comprehensive structure of mixed forests.

Effects of soil moisture condition and phosphorus supply on the seedlings growth and phosphorus efficiency of Schima superba provenances

2009, 20(11):  2617-2623. 

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Taking four representative Schima superba provenances from Longquan in Zhejiang, Jian’ou and Youxi in Fujian, and Ji’an in Jiangxi as test materials, and with the S. wallichii from Guangxi as the contrast, a pot experiment was conducted to study their seedlings growth and physiological responses under effects of different soil moisture condition and phosphorus supply. Significant differences were observed in the seedlings growth, root morphological parameters, and phosphorus absorption efficiency among the provenances under different soil moisture
 condition and phosphorus supply. The provenances from Jian’ou in Fujian and Longquan in Zhejiang exhibited larger growth increment, more developed root, and higher phosphorus absorption efficiency, compared with those from Youxi in Fujian and Ji’an in Jiangxi, while the S. wallichii from Guangxi Province remained its original characteristics of fast growing and drought and infertility resistance. Soil moisture condition and phosphorous supply had significant effects on the growth and development of S. superba. The seedlings growth, dry matter accumulation, root parameters, and phosphorus absorption efficiency were 18.5%-105.6% higher under appropriate soil moisture condition than under drought stress, and 37.5%-286.2% higher under high phosphorus than under low phosphorus supply. However, under drought stress and low phosphorus supply, S. superba seedlings allocated more photosynthetic products to their roots, and had higher phosphorus use efficiency, which could be an important physiological mechanism of the adaptation to drought stress and low phosphorus supply. Relative to the significant independent effects of provenance, watering level, and phosphorus supply, no significant interactive effects of the three factors were observed. 

Seasonal changes of main water parameters of Reaumuria trigyna in different habitats

2009, 20(11):  2624-2631. 

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By using pressvolume technique, this paper studied the seasonal changes of water potential at saturated point (Ψ_s^sat), water potential at turgor loss point (Ψ_s^tlp), relative osmotic water content at turgor loss point (ROWC^tlp), relative water content at turgor loss point (RWC^tlp), relative content of apoplastic water (AWC) , bound water/ free water (V_a/V_o), and the difference between Ψ_s^sat andΨ_s^tlp (ΔP) of Reaumuria trigyna growing on heavy solonchack, nonsalinized soil, and saline soil. The seasonal changes of Ψ_s^sat and Ψ_s^tlp were in order of May>July>September, while those of AWC, V_a/V_o, andΔP were in opposite sequence, indicating that the water deficit resistance ability of R. trigyna enhanced with season, being consistent with its growth rhythm. Comparing with other xerophytes, R. trigyna had very low Ψ_s^sat and Ψ_s^tlp, presenting its strong ability of maintaining high osmotic pressure and low water potential. Based on the water parameters measured in three months, and by using the subordination function of fuzzy mathematics, the water deficit resistance ability of R. trigyna was evaluated, which was the strongest on heavy solonchack, followed by on nonsalinized soil, and on saline soil.

Water physiological characteristics of four perennial plant species around Cele Oasis in Xinjiang

2009, 20(11):  2632-2638. 

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The water physiological characteristics of four perennial plant species (Populus euphratica, Tamarix ramosissima, Calligonum caputmedusae, and Alhagi sparsifolia) around Cele Oasis in Xinjiang were studied through their vegetation growth period. No signs of serious drought stress were observed in any of the test perennial species during their vegetation growth, and irrigation had little effects on the water status of the plants (P＞0.05). The seasonal variation characteristics of water physiological parameters differed with the plants. A. sparsifolia had the highest predawn water potential (PWP) and daily mean sap flow, but the lowest mean water use efficiency (WUE); C. caputmedusae had the highest mean WUE, and its PWP and sap flow were stable and had less seasonal change; T. ramosissima had the lowest PWP during its growth, and had better adaptation ability to the environment; and P. euphratica had relatively stable water physiological characteristics during its growth. The four perennial plant species had deep root systems to access underground water to satisfy their large demands for water, and thus, well adapted to the harsh environmental conditions around Cele Oasis. 

Spatialtemporal variation of soil organic carbon and its relations to soil physical properties in degraded alpine grasslands

2009, 20(11):  2639-2645. 

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By using grid sampling method, the spatialtemporal variation of soil organic carbon (SOC) and its relations to soil physical properties in degraded
alpine grasslands in North Tibet were studied. The SOC content and its density both in surface (0-10 cm) and in subsurface (10-20 cm) layers decreased in  order of slightly degraded grassland > normal grassland > moderately degraded grasslands > seriously degraded grasslands, and the differences of SOC content and its density between the two layers showed the same variation trend. An opposite trend was observed in the annual variation rates of SOC content and its density in different grasslands, and the variation was larger in surface than in subsurface layer. The annual accumulation rate of SOC in 0-10 cm layer in not degraded and slightly degraded grasslands was 0.018 and 0.003 g·kg^-1, being 6.0 and 2.0 times of that in 10-20 cm layer, while the annual loss rate of SOC in 0-10 cm layer in moderately and seriously degraded grasslands was 0.150 and 0.231 g·kg^-1, being 2.3 and 2.2 times of that in 10-20 cm layer, respectively. The total annual loss of SOC in moderately and seriously degraded grasslands was 3.8 times of the total annual accumulation of SOC in not degraded and slightly degraded grasslands. The degraded alpine grasslands in North Tibet had an average annual SOC loss of 7.87×10.⁷ t C·a^-1, and a greater potential to further loss in the future. The SOC content was significantly positively correlated with the contents of 5.0-1.0 mm, 1.0-0.5 mm, and 0.5-0.25 mm soil aggregates, soil bulk density, and soil moisture content.

Changes in plant communities and soil microbial physiological groups of artificial grasslands established for different years in headwater region of Yangtze River and Yellow River

2009, 20(11):  2646-2651. 

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An investigation was made on the plant communities of artificial grasslands established for different years in headwater region of Yangtze River and Y
ellow River, and the related soil physical and chemical properties and soil microbial physiological groups were analyzed. With the increase of establishment years, most of plant communities on the grasslands showed a “V” type change trend in their quantities, i.e., high-low-high, but the forbs biomass had a “Λ” type change trend and the sedge biomass increased gradually. Soil nutrients presented a “V” type but soil bulk density presented a “Λ” type change trend, while soil pH presented a decreasing trend. Most of soil microbial physiological groups and microbial biomass carbon showed a “V” type change trend, phosphorusdissolving bacteria showed a “Λ” type change trend, denitrifying bacteria decreased gradually, while cellulosedecomposing bacteria showed an increasing trend. The numbers of soil microbes had a close relationship with tested soil factors, and the soil microbial physiological groups were directly or indirectly affected by the soil factors. All the results indicated that the establishment of artificial grassland and the positive succession of vegetation could effectively improve soil physical and chemical properties, which benefit for the beneficial microbes to settle down and propagation, while proliferation of the nonbeneficial microbes was inhibited.

Effects of tillage and mulching on orchard soil moisture content and temperature in Loess Plateau

2009, 20(11):  2652-2658. 

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A field experiment was conducted to study the effects of different tillage system (no-tillage, rotary tillage, and plow tillage) and mulching (straw
mulch, sod mulch, and film mulch) on the orchard soil moisture content and temperature in Loess Plateau. Under different tillage system, the soil moisture content in 0-1 m layer differed significantly in May, with the sequence of no-tillage (14.28%)>rotary tillage (14.13%)>plow tillage (13.57%)
, but had less difference in September. Straw mulch induced significantly higher soil moisture content than sod mulch, film mulch, and no-mulch. Among the treatments tillage plus mulching, no-tillage plus straw mulch resulted in the greatest soil water storage. The average soil temperature at daytime was in order of film mulch>no-mulch>sod mulch>straw mulch, and the change range of soil temperature was no-mulch>film mulch>sod mulch>straw mulch. Soil water storage under different mulching treatments was not always negatively correlated with soil temperature, but depended on the water conservation effect and heatpreserved capacity of mulching material. Above all, the main conservation tillage system for the orchards in Loess Plateau would be no tillage plus straw mulch.

Effects of irrigation with regenerated water on the growth and quality of alfalfa

2009, 20(11):  2659-2664. 

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A pot experiment was conducted to study the effects of irrigation with regenerated water on the growth, nutrient uptake, and quality of alfalfa. Four
treatments were installed, i.e., irrigation with fresh water (Q), irrigation with regenerated water (Z), mixed irrigation with regenerated water and fresh water (Z+Q), and rotational irrigation with regenerated water and fresh water (Z/Q). Comparing with treatment Q, treatment Z increased the stem length, lateral branch number, and plant biomass significantly, but decreased leaf area. Treatments Z, Z+Q, and Z/Q increased plant soluble protein content by 78.43%, 83.68% and 72.53%, respectively, but treatment Z decreased plant soluble sugar content. Treatment Z increased plant Ca and Mg contents by 27.78% and 26.61%, and treatments Z and Z+Q decreased plant Fe content by 28.71% and 10.09%, respectively. Treatments Z, Z+Q, and Z/Q increased the cadmium content in aboveground part of alfalfa by 98.6%, 89.5%, and 59.0%, respectively, but the cadmium and lead contents were still lower than the thresholds of National Sanitation Standard (GB 13078-2001). It was suggested that regenerated water could be used as a source of irrigation water in alfalfa growth, but its longterm effect should be concerned.

Effects of limited supplemental irrigation with catchment rainfall on potato growth in rainfed areas of western Loess Plateau

2009, 20(11):  2665-2670. 

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Field experiments were conducted to study the effects of limited supplemental irrigation with catchment rainfall on the growth of potato cultivars Dax
iyang and Tongshu 23 in rainfed areas of western Loess Plateau. Supplemental irrigation with catchment rainfall at seedling stage increased the potato yield significantly, and the increment was higher for Daxiyang than for Tongshu No.23. Supplemental irrigation at tuber expanding stage increased the yield of Tongshu 23, but decreased the yield of Daxiyang. Low amount of supplemental irrigation (45 mm) increased the water use efficiency (WUE) and irrigation water use efficiency (IWUE) of Tongshu 23. For Daxiyang, its WUE and IWUE were higher when the supplemental irrigation was made at seedling stage than at tuber expanding stage. Supplemental irrigation increased the tuber yield and the percentages of bigger and medium tubers of Tongshu 23, but the percentages of green and blet tubers were also increased. As for Daxiyang, supplemental irrigation increased the percentages of bigger and smaller tubers, as well as the percentage of blet tuber.

Effects of regulated deficit irrigation on water consumption characteristics and water use efficiency of winter wheat

2009, 20(11):  2671-2677. 

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With the highyielding winter wheat cultivar Jimai 22 as test material, a field experiment was conducted in Yanzhou of Shandong to examine the effects of regulated deficit irrigation on the water consumption and water use efficiency（WUE）of the cultivar. Five treatments were installed, i.e., the soil relative moisture content at sowing, jointing, and anthesis stages being 80%, 65% and 65% (W0 ), 80%, 70% and 70% (W1), 80%, 80% and 80% (W₂ ), 90%，80% and 80% (W₃), and 90%, 85% and 85%  (W₄)， respectively. Under the condition of 228 mm precipitation in growth season, the total water consumption was higher in treatments W₁ and W₄ than in treatments W₀, W₂, and W₃, and no difference was observed between treatments W₁ and W₄. Comparing with W₄, treatment W₁ decreased the water storage in 0-200 cm soil layer and the water consumption by wheat from jointing to anthesis stages, but increased the water consumption from anthesis to maturity stages. The water consumption rates at the stages from jointing to anthesis and from anthesis to maturity in treatment W₄ were higher. Under regulated deficit irrigation, treatment W₀ had higher WUE, but the grain yield was the lowest. The WUE in other treatments increased first, and then decreased with increasing irrigation amount. Both the water consumption and the grain yield were the highest in treatments W₁ and W₄, and treatment W₁ had higher irrigation water use efficiency and irrigation benefit than treatment W₄, being the best irrigation regime of high-yielding and water-saving in our study.

Effects of controlledrelease fertilizers on summer maize grain yield, field ammonia volatilization, and fertilizer nitrogen use efficiency

2009, 20(11):  2678-2684. 

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A field experiment with colophony-coated fertilizer (CRF) and sulfur-coated fertilizer (SCF) showed that under the same application rates of N, P
and K, applying CRF and SCF increased the summer maize grain yield by 13.15% and 14.15%, respectively, compared to the application of common compound fertilizer CCF. When the applied amount of CRF and SCF was decreased by 25%, the yield increment was 9.69% and 10.04%, respectively; and when the applied amount of CRF and SCF was decreased by 50%, the yield had less difference with that under CCF application. The field ammonia volatilization rate in treatments CRF and SCF increased slowly, with a peak appeared 7 days later than that in treatment CCF, and the total amount of ammonia volatilization in treatments CRF and SCF was ranged from 0.78 kg N·hm^-2 to 4.43 kg N·hm^-2, with a decrement of 51.34%-91.summer maize; controlledrelease fertilizer; ammonia volatilization;

Alleviation effects of LaCl₃ on photosynthetic characteristics of cucumber seedlings under nitrate stress

2009, 20(11):  2685-2690. 

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By the method of hydroponic culture, this paper studied the alleviation effects of LaCl₃ on the photosynthetic characteristics of cucumber seedlings
 under nitrate (140 mmol NO₃-·L^-1) stress, with the related mechanisms discussed. Under nitrate stress, the seedlings leaf chlorophyll and carotenoids contents decreased significantly, and the leaf Mg²⁺ATPase, Ca²⁺ATPase activities also decreased. On the 7th day of nitrate stress, the decrease of seedlings photosynthetic rate was mainly due to stomatal limitation; but on the 12th day of nitrate stress, the decrease was mainly due to no-stomatal limitation. Supplement with LaCl₃ could make the cucumber seedlings keep relatively higher leaf Mg^2+-ATPase and Ca^2+-ATPase activities and chlorophyll and carotenoids contents, and applying 20 μmol·L^-1 of LaCl₃ could increase the carotenoids content significantly. LaCl₃ could also improve the leaf gas exchange, and alleviate the decrease of leaf F_v/F_m, Ф_PSII, AQY, CE, and q_p under nitrate stress, which helped the lea
ves making good use of light energy and maintaining higher CO₂ assimilation capacity. An additional 20 μmol·L^-1 of LaCl₃ could alleviate the nitrate
 stress on the photosynthesis of cucumber seedlings efficiently, but an additional 200 μmol·L^-1 of LaCl₃ only had the alleviation effect at the initia
l period of nitrate stress. Our results could benefit to the improvement of greenhouse soil.

Effects of irrigation stage and amount on winter wheat fructan accumulation and translocation after anthesis and water use efficiency

2009, 20(11):  2691-2698. 

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Field experiments were conducted in Tai’an and Yanzhou of Shandong Province in 2004-2005 and 2005-2006 to study the effects of irrigation stage and amount on the accumulation and translocation of fructan in winter wheat penult stem and sheath after anthesis and the water use efficiency. No irrigation in whole growth period promoted the translocation of fructan from penult stem and sheath to grain at late grainfilling stage. Irrigation with 60 mm water at jointing and anthesis stages increased the flag leaf photosynthetic rate and photo-assimilate accumulation after anthesis, and the contribution of the photo-assimilates to the grain. Irrigation with 60 mm water at jointing, anthesis, and grain-filling stages, and with 90 mm water at jointing and anthesis stages decreased the flag leaf photosynthetic rate at late grain-filling stage, increased the photo-assimilate accumulation before anthesis and the contribution of the photo-assimilates to the grain, and reduced the translocation of the photo-assimilates after anthesis to the grain. Excessive irrigation also increased the contents of fructan with the degree of polymerization (DP) ≥4 and =3 in penult stem and sheath at late grainfilling stage, limiting the translocation of fructan from penult stem and sheath to grain. Irrigation with 60 mm water at jointing and anthesis stages led to a higher grain yield and the highest water use efficiency, while irrigation with 60 mm water at jointing, anthesis, and grainfilling stages, and with 90 mm water at jointing and anthesis stages had little effects on the grain yield but decreased the water use efficiency.

Effects of soil moisture regime on greenhouse tomato yield and its formation under drip irrigation

2009, 20(11):  2699-2704. 

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Field plot experiment was conducted to study the effects of soil moisture regime at different growth stages on the fruit size, fruit number, percentag
e of malformed fruit, and yield formation of greenhouse tomato under drip irrigation, and the relationships between tomato yield and irrigation amount. Moderate soil water deficit (50%-55% of field capacity) at tomato’s seedling stage increased the fruit number but reduced the fruit size, decreased t
he percentage of malformed fruit, and made the fruit maturation mainly concentrated in later picking period. Severe water deficit (less than 65% of field capacity) at flowering and fruit-developing stages promoted fruit maturation, but decreased fruit number and increased the formation of small and malformed fruits. The soil moisture content higher than 80% or lower than 65% of filed capacity at fruit maturation stage less affected fruit maturation but decreased fruit yield, and lower than 65% of filed capacity also decreased the fruit number and increased the percentage of malformed fruit. No significant effects of irrigation amount on fruit maturation were observed. The correlations of tomato yield and its water use efficiency with irrigation amount could be well described by quadratic function. The fruit number and total yield were higher while the percentage of malformed fruit was lower when the soil moisture content was controlled at 60%-65% of field capacity at seedling stage, 70%-75% of field capacity at flowering stage, and 70%-75% of field capacity at fruitdeveloping stage, which could be used as the optimal soil moisture indices for the greenhouse tomato production under drip irrigation

Shadetolerance indices of maize: Selection and evaluation

2009, 20(11):  2705-2709. 

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A field experiment was conducted to study the morphological, physiological, and yield traits of 24 maize cultivars under 50% shading. Comparing with t
he control, 50% shading decreased the plant height, stem diameter, leaf net photosynthetic rate (P_n), specific leaf weight (SLW), aboveground dry matter accumulation, ear length and diameter, axis diameter, and kernels per row. The interval from anthesis to silking (ASI) was prolonged, and the grain yield was decreased significantly. The percent changes of ASI,P_n,SLW, and kernels per row were significantly correlated with aboveground dry matter accumulation and grain yield, being able to be used as the indices to evaluate the maize shade-tolerance in field. Cluster analysis using comprehensive shade-tolerance traits as evaluation parameters indicated that 14 maize cultivars including Zhengdan 958, Xundan 20, and Denghai 602, etc. were of shade-tolerance type, and 10 cultivars (Anyu 12 and Yuyu 22, etc.) were of shade-sensitive type. It was suggested that adopting the morphological, physiological and yield traits as the indices to evaluate the shade-tolerance of maize would be more objective, simple and practical.

Distribution characteristics of soil pH, CEC and organic matter in a small watershed of the Loess Plateau

2009, 20(11):  2710-2715. 

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Soil chemical properties play important roles in soil ecological functioning. In this study, 207 surface soil (0-20 cm) samples were collected
 from different representative landscape units in a gully watershed of the Loess Plateau to examine the distribution characteristics of soil pH, cation exchange capacity (CEC) and organic matter, and their relations to land use type, landform, and soil type. The soil pH, CEC and organic matter content ranged from 7.7 to 8.6, 11.9 to 28.7 cmol·kg^-1, and 3.0 to 27.9 g·kg^-1, and followed normal distribution, log-normal distribution, and negative binomial distribution, respectively. These three properties were significantly affected by land use type, landform, and soil type. Soil CEC and organic matter content were higher in forestland, grassland and farmland than in orchard land, and soil pH was lower in forestland than in other three land use types. Soil pH, CEC and organic matter content were higher in plateau land and sloping land than in gully bottom and terrace land. Soil CEC and organic matter content were higher in dark loessial soil and rebified soil, while soil pH was higher in yellow loessial soil. Across all the three land scape factors, soil CEC and organic matter content showed the similar distribution pattern, but an opposite distribution pattern was observed for soil pH.

Stream ecosystem health assessment based on the measurement of leaf litter breakdown: A case study in Hengshishui River of Guangdong Province

2009, 20(11):  2716-2722. 

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Based on the Gessner’s model of leaf litter breakdown, the functional integrity and ecosystem health of Hengshishui River in Guangdong Province were assessed, and the breakdown rates of Castanopsis fissa and Schima superba leaf litters at the sites unpolluted and polluted by acid mine drainage were compared. The leaf litters of the two tree species had a significantly lower breakdown rate at polluted than at unpolluted sites (P<0.05). According the Gessner’s model, all polluted sites had an ecosystem health score 0, while all unpolluted sites had a score 2, indicating that the health status of polluted river reaches were severely damaged. The biological assessment of stream ecosystem health was consistent with the results of water quality analysis, indicating that the leaf litter breakdown model was a suitable index of stream status.

Agricultural eco-economic system coupling in Zhifanggou watershed in hilly-gully region of Loess Plateau

2009, 20(11):  2723-2729. 

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Agricultural eco-economic system coupling is an organic unit formed by the inherent interaction between agricultural ecosystem and economic system, and regulated and controlled by mankind moderate interference. Its status can be expressed by the circular chainnet structure of agricultural resources and agricultural industry. The agricultural ecoeconomic system in Zhifanggou watershed has gone through the process of system coupling, system conflict, system coupling, and partial conflit in high leverage, which is caused by the farmers’ requirement and the state’s macropolicy, economic means, and administrative means. To cope with the problems of agricultural ecoeconomics system coupling in Zhifanggou watershed, the optimal coupling model should be established, with tree-grass resources and related industries as the core.

Ecological compensation criterion in Gannan Tibetan Autonomous Prefecture based on minimumdata method

2009, 20(11):  2730-2735. 

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Quantitatively setting ecological compensation criterion is a focus and a difficulty in establishing ecological compensation mechanism. Based on the 1987-2007 meteorological data and the 2007 social survey data of Gannan Tibetan Autonomous Region, the supply curves of grassland ecosystem services in the Region were simulated by the methods of minimum-data, social survey, and precipitation storage estimation. The opportunity cost of implementing ecological compensation in the Region in 2007 was 503.6 yuan·hm^-2, per unit water conservation volume supplied by grassland ecosystem was 1110.7 m³·hm^-2, and ecological compensation criterion was 788.6 yuan·hm^-2. The total water conservation volume supplied by grassland ecosystem was 2.56×10.9 m³.

Extraction of structured vegetation cover index for Loess Area in North Shaanxi based on TM images

2009, 20(11):  2736-2742. 

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Based on the concept of structured vegetation cover index (C_s) and by using TM images as the information source, the extraction way of C_s for Loess
Area in North Shaanxi by using remote sensing techniques was explored. In study area, C_s was better than the traditional projected vegetation overage index in expressing the relationships between vegetation structure and soil erosion. The C_s was closely related to the remote sensing vegetation indices, such as green indices NDVI (Normalized Difference Vegetation Index) and MSAVI (Modified Soil Adjusted Vegetation Index), and yellow indices NDSVI (Difference Senescent Vegetation Index) and NDTI (Normalized Difference Tillage Index). The combination of the green and yellow indices could better express the effects of vegetation on soil erosion, compared with the single index. Among these remote sensing vegetation indices, the MSAVI and NDTI could be the ideal green and yellow vegetation indices for the extraction of C_s from TM images. It was possible to extract the C_s from remote sensing data through the regression analysis of C_s and remote sensing vegetation indices. However, this method was just valid
ated and applied to the study area. Whether it could be applied to other regions was needed to be further validated due to the phonological differences from one region to another.

Spatiotemporal characteristics of MODIS NDVI in Hulunber Grassland

2009, 20(11):  2743-2749. 

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Time-eries MODIS NDVI datasets from 2000 to 2008 were used to study the spatial change trend, fluctuation degree, and occurrence time of the annual NDVI_max of four typical grassland types, i.e., lowland meadow, temperate steppe, temperate meadow steppe, and upland meadow, in Hulunber Grassland. In 2000-008, the vegetation in Hulunber Grassland presented an obvious deterioration trend. The mean annual NDVI_max of the four grassland types had a great fluctuation, especially in temperate steppe where the maximum change in the mean value of annual NDVI_max approximated to 50%. As for the area change of different grade grasslands, the areas with NDVI_max between 0.4and 1 accounted for about 91% of the total grassland area, which suggested the good vegetation coverage in the Grassland. However, though the areas with NDVI_max values in (0.4, 0.8］ showed an increasing trend, the areas with NDVI_max values in (0.2, 0.4］ and (0.8, 1］ decreased greatly in the study period. Overall, the deteriorating grassland took up about 66.25% of the total area, and the restoring grassland took the rest. There was about 62.85% of the grassland whose NDVI_max occurred between the 193rd day and the 225th day in each year, indicating that this period was the most important vegetation growth season in Hulunber Grassland.

Effects of topographic correction on remote sensing estimation of forest biomass

2009, 20(11):  2750-2756. 

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Based on four commonly used models (Cosine model, C model, C+SCS model, and Minnaert model), the topographic effects in Landsat-5 image of Maoershan region in Heilongjiang Province acquired on July 21, 2007 were calibrated on the platform of IDL language. The 4 models were validated from the aspects of visual differences and quantitative statistical features of the images. After the correlation analysis on the corrected remote sensing data and the forest biomass data, the biomass retrieving models were constructed. Furthermore, the effects of different topographic factors on the estimation of forest biomass were studied. The results showed that due to its liner presumption, the topographic correction combined with K-T transformation was not suitable for forest biomass estimation, and the correlations between the remote sensing data and the forest biomass fluctuated significantly. The parameters of the transformation needed to be adjusted in accordance with the information of land surface. The information content of vegetation index was significantly increased after topographic correction, and the correlation between vegetation index and forest biomass was enhanced greatly. Among the four models, Cosine model overcorrected the shaded areas in image, C model and C+SCS model had good correction performance by using semi-empirical parameters, while Minnaert model decreased the error of biomass estima
tion and improved the precision of remote sensing retrieving models effectively.

Effects of water temperature and feeding on respiratory metabolism of juvenile Salvelinus fontinalus

2009, 20(11):  2757-2762. 

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The oxygen consumption and ammonia excretion rates of juvenile brook trout (Salvelinus fontinalus) under satiation and starvation were measured at
 different levels of water temperature ［(5.5±0.5) ℃、(8.5±0.5) ℃、(11.5±0.5) ℃、(14.5±0.5) ℃、(17.5±0.) ℃］,aimed to study the effects of water temperature and feeding on the respiratory metabolism of the fish. Under satiation, the oxygen consumption and ammonia excretion rates of juvenile S. fontinalus at the five temperature levels increased rapidly to the maximum, and then decreased gradually to the initial state. The regression equations of oxygen consumption rate (OR) and ammonia excretion rate (NR) to water temperature (t) wereOR=-0.0601t⁴+2.5542t³-39.256t²+276.26t-598.75(n=650，R²=1，4.5 ℃<t<17.5 ℃) and NR=-0.0020t⁴+0.0826t³-1.2318t²+8.6186t-18.838(n=650，R²=1，4.5 ℃<t<17.5 ℃), respectively. Under starvation, the regression equations were OR=13.723t^0.9738(n=650，R²=0.9974，4.5 ℃<t<17.5 ℃) and NR=0.1687t^1.0896(
n=650，R²=0.9977，4.5 ℃<t<17.5 ℃), respectively. The  optimal temperature range was 11.5 ℃-14.5 ℃. The juvenile S. fontinalus in starvation was heavily depended on fat and carbohydrates.

Super-cooling ability and its relations to body’s water and fat contents of overwintering Hyphantrian cunea |（Lepidoptera： Arcidae） pupae

2009, 20(11):  2763-2767. 

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The determinations of super-cooling ability and body’s water and fat contents of overwintering Hyphantria cunea pupae showed that during overwin
tering, the female and male H. cunea pupae had the similar change patterns in their cold-resistance ability, i.e., increased with decreasing air temperature, but their body’s water and fat contents, super-cooling point (SCP), and freezing point (FP) differed at different overwintering stages. The SCP was significantly lower at preand mid overwintering stages than at late-overwintering stage, while FP had less difference among the stages. The body’s water content was significantly higher at mid-overwintering stage than at pre and late-over wintering stages. Comparing with nonoverwintering pupae, the overwintering pupae had significantly lower SCP and FP, but significantly higher body’s water and total fat contents. Regression analysis showed that there was a negative relationship between the water content and the SCP of female and male pupae (P<0.05).

Calling and mating behaviors of adult Orthaga achatina |(Lepidoptera: Pyralidae)

2009, 20(11):  2768-2772. 

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A laboratory study was made on the calling and mating behaviors of adult Orthaga achatinaat (27±1) ℃, (60±10) % RH, and 14 L:10 D photoperiod.
 The female O. achatina did not call until the start of scotophase, with the calling percentage increased sharply at the 5^th hour and reached the peak
 at the 6^th-7^th hour of scotophase. The calling percentage varied with moth age, being the highest (>70%) at the age of 2-3 d. The mating behavior could be divided into two successive periods, i.e., calling period and mating period. The mating between female and male O. achatina occurred during the 5^th-9^th hour of scotophase, with the peak at the 6^th-7^th hour into scotophase, which was in accordance with the peak time of female calling behavior. Females mated only one time during their whole life. Treatment 1♀∶2♂showed a significantly higher mating percentage, but a significantly shorter mating duration time, compared with treatment 1♀∶1♂.

Bt toxic protein expression in insect-resistant transgenic corns and its transfer to and accumulation in  Ostrinia furnacalis

2009, 20(11):  2773-2777. 

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Taking the insect-resistant transgenic corn varieties G03-2396 and G03-2739 and the conventional corn variety Suyu 16 as test materials, a bioassay in laboratory was conducted to test their resistance against  Ostrinia furnacalis. The Bt toxin expression in different tissues of the two transgenic corns, the ingestion of  Bt  toxin by the 3rd and 5th instar of O. furnacalis, and the  Bt  toxin amount in feces of O. furnacalis larvae fed with  Bt  corns were analyzed by using enzyme-linked-immunosorbent-assay (ELISA). It was found that the central leaves of both G03-2396 and G03-2739 had great toxicity to O. furnacalis larvae. After fed with the central leaves for 6 d, the survival rate of neonate larvae was less than 3%, and that of the 3rd instar larvae was less than 70%. Female ears had smaller toxicity than central leaves. The  Bt  toxic protein was detected both in the leaves and in the female ears of the two transgenic corns, but its content was higher in central leaves than in female ears. The Bt  toxic protein expression level was in  order of G03-2739 central leaf (39.6 μg·g^-1 FM) > G03-2396 central leaf (26.1 μg·g^-1 FM) > G03-2396 female ear (17.0 μg·g^-1 FM) > G03-2739 female ear (14.6 μg·g^-1 FM). When fed with central leaf or female ear, the  Bt toxic protein amount in the 3rd instar larvae was significantly higher than that in the 5th instar larvae. For the same age instar larvae, the  Bt  toxic protein content was significantly higher after fed with central leaf than fed with female ear, so did the  Bt toxic protein content in larvae feces, being the highest (10.4 μg·g^-1 FM) for the 5th instar larvae fed with G03-2739 central leaf, and the lowest (2.7 μg·g^-1 FM) for the 3rd instar larvae fed with G03-2739 female ear.

Antimicrobial activity of volatile oil from Atractylodes lancea against three species of endophytic fungi and seven species of exogenous fungi

2009, 20(11):  2778-2784. 

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In order to investigate the inhibitory effects of host plants secondary metabolites on the growth of endophytic and exogenous fungi, the volatile oil
from medicinal plant Atractylodes lancea was extracted with organic solvent extraction method, and its antimicrobial activity against three species of endophytic and seven species of exogenous fungi was determined by paper disc assay and spreadplate. The volatile oil had inhibitory effects on the growth of test endophytic fungi. It had strong antimicrobial activity against Rhodotorula glutinis and Saprolegnia, but weak activity against Rhizopus and Absidia. It suppressed the sporulation of Trichoderma viride and Aspergillus niger, but no effects on the growth of Phytophthora. Under the stress of high concentration volatile oil, the hyphal branches of test endophytic fungi increased, the distance between the branches became shorter, and the growth of aerial hyphae was inhibited. The test endophytic fungi had remarkable ability to metabolize and transform the volatile oil, and decreased the contents of its main ingredients. All the results showed that the volatile oil extracted from A. lancea had inhibitory effects on the growth of endophytic fungi, but the fungi could adapt to the volatile oil via metabolizing and decomposing it.

Relationships between temperature change and microbial amount in inactive ice wedges in Yitulihe| Northeast China

2009, 20(11):  2785-2789. 

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Ice-wedge is an indicator of paleoclimate change. The δ¹⁸O concentration in  different layers could reflect the change  of paleotemperature during ice-wedge growth. In the late 1980s, inactive ice wedges were found in Yitulihe, Northeast China, which were the south-most ones so far and were important in climatic and environmental research. In this paper, the δ¹⁸O concentration and microbial number in the inactive ice-wedges were analyzed by using stable isotope, fluorescence microscopy counting, and flow cytometer (FCM). During the ice-wedge growth in Yitulihe area, there were three short-term paleotemperature fluctuation, and three times of fluctuation in microbial amount in different ice-wedge layer. Correlation analysis indicated that there was a converging relationship between the temperature change and microbial amount in the ice-wedges. The lower the temperature when ice-wedge layer formed, the less the microbes survived in the layer.

Effects of pig manure and oxytetracycline on microbial number and activity in soils with different fertility levels

2009, 20(11):  2790-2798. 

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An incubation test was conducted to study the effects of antibiotics oxytetracycline on the microbial number and activity in three soils varied with f
ertility level under the conditions with or without pig manure application. The soils were injected with six concentrations (0, 0.1, 1, 10, 100, and 1000 mg·kg^-1) oxytetracycline, and incubated for 30 d at 25 ℃. Soil samples were collected on the 1st, 4th, and 30th day of incubation to measure the bacterial number, respiratory activity, and enzyme activity. Under no pig manure application, oxytetracycline had little effects on the soil bacterial number and activity. The EC₁₀ values of oxytetracycline based on a 10% decrement of bacterial number, respiratory activity, enzyme activity, and NO₃-N concentration in treatment without pig manure were 36-1000 mg·kg^-1, 20-1000 mg·kg^-1, and 4-1000 mg·kg^-1 for S₁, S₂ and S₃, while those in treat
ment with pig manure application were 2-56 mg·kg^-1, 2-1 mg·kg^-1, and 1-2 mg·kg^-1 for S₁, S₂ and S3, respectively. Soil fertility level had obvious effects on the dose-sponse relations between oxytetracycline and soil microbial number and activity. The effects of oxytetracycline on soil microbial number and activity increased with increasing soil fertility level, and the effects on microbial number and respiratory activity were higher than those on enzyme activity and NO₃-N concentration. The effects of oxytetracycline on soil microbial number and activity were timeepending, being the greatest on the 4th day of incubation. Overall speaking, oxytetracycline could exert temporary inhibition on soil microbes.

Spatiotemporal distribution of total nitrogen and total phosphorus in sediments of Xiangxi Bay, Three Gorges Reservoir

2009, 20(11):  2799-2805. 

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The spatiotemporal distribution of total nitrogen (TN) and total phosphorus (TP) in sediments of Xiangxi Bay, Three Gorges Reservoir was investigated from October 2004 to July 2006, with related affecting factors analyzed. The TN and TP concentrations in the sediments were higher in the middle stretch but lower in the two edges of the Bay. The maximum value of TN concentration (1.08 mg·g^-1) appeared in the middle part of the Bay, and the minimum (0.89 mg·g^-1) occurred at the adjacent areas to the river mouth; while the maximum value of TP concentration (1.07 mg·g^-1) appeared in the middle, and the minimum (0.80 mg·g^-1) was in the edges of the Bay. The TN concentration decreased in the sequence of autumn-winter-spring, but increased from spring to summer dramatically; while the seasonal variation of TP concentration was not very significant, with the maximum occurred in spring. Significant inter-annual variations were observed in the TN and TP concentrations. The spatial distributions of TN and TP concentrations were mainly affected by the sedimentation of suspended matter. In the regions where sedimentation rate was high, the TN and TP concentrations were also very high. The seasonal fluctuation of TN concentration was mainly affected by river discharge, while that of TP concentration was main
ly affected by point source pollution.

Effects of heavy metals pollution on paddy soil aggregates composition and heavy metals distribution

2009, 20(11):  2806-2812. 

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Topsoil samples were collected from a polluted and an adjacent non-polluted paddy field in the Taihu Lake region of China. Different particle size fractions of soil aggregates were separated by low-energy dispersion procedure, and their mass composition and Pb, Cd, Hg, and As concentrations were determined. Under heavy metals pollution, the mass composition of sand-sized fractions reduced, while that of clay-sized fractions increased. The concentrations of test metals in different particle size fractions differed, with the highest in <0.002 mm fraction, followed by in 2-0.2 mm fraction. In 0.02-0.002 mm and 0.2-0.02 mm fractions, all the test metals were relatively deficient, with an enrichment index of 0.56-0.96. The present study showed that the aggregation of fine particles could be depressed by heavy metals pollution, which in turn, led to a relative increase in the mass composition of fine particles and the associated allocation of heavy metals in weakly aggregated silt particles, and further, increased the risks of heavy metals translocation from polluted farmland into water and atmosphere. Further studies should be made on the impacts of heavy metals pollution on soil biophysical and biochemical processes and related mechanisms.

Early-warning and prediction technology of harmful algal bloom: A review

2009, 20(11):  2813-2819. 

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Harmful algal bloom (HAB) occurs frequently and causes serious damage. To study the earlywarning and prediction technology of HAB is of significance for the early-warning and prediction, ecological control, and disaster prevention and mitigation of HAB. This paper reviewed the research progress in the early-warning and prediction technologies of HAB, including transport prediction, specific factors critical value prediction, datadriven model, and ecological math model, and evaluated the advantages and disadvantages of these four types of technologies. Some new ideas were brought forward about the prediction of cyanobacterial growth rate based on cell characteristics, and the earlywarning of cyanobacterial bloom based on algal community characteristics.

Periphyton and its application in water purification

2009, 20(11):  2820-2826. 

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Periphyton widely exists in natural water bodies, with the characteristics of huge biomass generation, strong ecological function, and sensitive respo
nse to water quality. It removes the pollutants in water bodies mainly through the processes of absorption, metabolism, adsorption, and complexation, etc. Owing to its high tolerance against pollution and high removal efficiency for nitrogen and phosphorus, as well as the feasibility of recycling its cells at low cost, periphyton is a promising candidate for developing the treatment techniques of water purification. The newlydeveloped artificial periphyton systems, e.g., algal turf scrubbers, periphyton biofilm systems, periphyton aquaculture systems, have been successfully applied in treating livestock manure, aquiculture wastewater, and municipal sewage. However, further researches are needed to understand the growth patterns of periphyton, its physiological responses to pollutants concentration, and its molecular biological mechanisms in removing pollutants.

Research advances in the responses of carbohydrates in grassland plants to environmental stress

2009, 20(11):  2827-2831. 

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Carbohydrates are the main energy materials for plant metabolic activities. Enough carbohydrates stored in roots are necessary for plant regrowth, its tolerance against environmental stress, and the maintenance of  grassland ecosystem stability. This paper summarized the influences of grazing, nitrogen fertilization, salt stress, drought, low temperature, and low oxygen stress on the carbohydrates in grassland plants, and introduced the advanced methods of measuring root carbohydrates. It was suggested that the research emphasis in the future should be paid on the relationships between root soluble sugar components and root physio-ecological functions.

Topsoil application in vegetation restoration in Japan

2009, 20(11):  2832-2838. 

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Soil seed bank has the unique regional species composition and genetic characteristics, and plays important roles in maintaining species diversity and population density. Topsoil, as a kind of revegetation materials, has the potential in vegetation restoration. Based on the Japanese literatures, this paper introduced the characteristics and contents of revegetation with topsoil, and discussed the revegetation modes from the aspects of topsoil mixing ratio, slope surface condition, and topsoil collection depth. The application cases of topsoil in various habitat types such as forests, roads, wetlands, and abandoned lands were also introduced. Some suggestions to the further researches on topsoil application in vegetation restoration were proposed, e.g., to strengthen the practical research of topsoil, to determine the appropriate techniques and targets of topsoil application as well as the survey methods and applicability standards, and to develop the low cost and high-efficient new application ways of topsoil.