Table of Content

18 March 2011, Volume 22 Issue 03

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Articles

Ecological memory and its potential applications in ecology: A review.

2011, 22(03):  549-555. 

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Ecological memory (EM) is defined as the capability of the past states or experiences of a community to influence the present or future ecological responses of the community. As a relatively new concept, EM has received considerable attention in the study of ecosystem structure and function, such as community succession, ecological restoration, biological invasion, and natural resource management. This review summarized the definition, components, and categories of EM, and discussed the possible mechanisms and affecting factors of EM. Also, the potential applications of EM were proposed, in order to further understand the mechanisms of community succession and to guide ecological restoration.

Vegetation above-ground biomass and its affecting factors in water/wind erosion crisscross region on Loess Plateau.

2011, 22(03):  556-564. 

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Field investigations were conducted in Liudaogou small watershed in late September 2009 to study the differences of vegetation above-ground biomass, soil moisture content, and soil nutrient contents under different land use patterns, aimed to approach the vegetation above-ground biomass level and related affecting factors in typical small watershed in water/wind erosion crisscross region on Loess Plateau. The above-ground dry biomass of the main vegetations in Liudaogou was 177-2207 g·m^-2, and that in corn field, millet field, abandoned farmland, artificial grassland, natural grassland, and shrub land was 2097-2207, 518-775, 248-578, 280-545, 177-396, and 372-680 g·m^-2, respectively. The mean soil moisture content in 0-100 layer was the highest (14.2%) in farmlands and the lowest (10.9%) in shrub land. The coefficient of variation of soil moisture content was the greatest (26.7%) in abandoned farmland, indicating the strong spatial heterogeneity of soil moisture in this kind of farmland. The mean soil water storage was in the order of farmland > artificial grassland > natural grassland > shrub land. Soil dry layer was observed in alfalfa and caragana lands. There was a significant positive correlation (r=0.639, P<0.05) between above-ground dry biomass and 0-100 cm soil water storage, and also, a very significant positive correlation between above-ground fresh biomass and vegetation height. The above-ground biomass of the higher vegetations could potentially better control the wind and water erosion in the water/wind erosion crisscross region. Vegetation above-ground biomass was highly correlated with soil moisture and nutrient contents, but had no significant correlations with elevation, slope gradient, slope aspect, and soil bulk density.

Relationships between initial chemical composition of forest leaf litters and their decomposition rates in degraded red soil hilly region of Southern China.

2011, 22(03):  565-570. 

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A pot experiment with litter bags was conducted to study the relationships between the initial chemical composition of 8 kind forest leaf litters and 4 kind mixed leaf litters and their decomposition rates in degraded red soil hilly region of Southern China. Comparing with needle-leaf litters, broad-leaf litters had significantly higher contents of N, P, K, and Mg, but significantly lower contents of lignin and C. The decomposition rates of test litters were significantly positively correlated with the litters initial contents of N, P, K, and Mg (P<0.05), and negatively correlated with the initial contents of lignin and C as well as the lignin/N, lignin/P, and C/P ratios (P<0.05). The lignin content explained 54.3% of the variation in litter decomposition rates, being the key affecting factor. Litters C, N, and P contents also had close correlations with the decomposition rates, and together with lignin content, contributed 81.4% of the variation. It was suggested that in the process of vegetation restoration in degraded red soil hilly region of Southern China, introducing broad-1eaf trees with lower lignin and higher N and P contents would benefit the acceleration of forest litters decomposition and the restoration of soil fertility.

Magnolia liliiflora whole-tree sap flow in response to multiple environmental variables in Beijing.

2011, 22(03):  571-576. 

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In order to clarify the environmental factors affecting the water use of typical urban tree species Magnolia liliiflora, an investigation was conducted on the responses of M. liliiflora whole-tree sap flow to the air temperature, air relative humidity, radiation, wind speed,  soil temperature and water  content, and precipitation in Beijing from April to October, 2008. The eight environmental factors affecting M. liliiflora whole-tree sap flow could be divided into three categories, i.e., evaporative demand index, soil index, and precipitation index. The evaporative demand index (air temperature, air relative humidity, total radiation, wind speed, and vapor pressure deficit) could explain 60% of the variation in the sap flow of individual trees, which presented S-type change trend, i.e., the sap flow reached an asymptote where higher light and evaporative demands could not cause sap flow to increase further. Soil index (soil temperature and water content) and precipitation index (precipitation amount) had little influence on the sap flow.

Spatiotemporal differentiation of construction land expansion in a typical town of south Jiangsu Province.

2011, 22(03):  577-584. 

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Choosing Xinzhuang Town in south Jiangsu Province as study area, and by using 1980, 1991, 2001, and 2009 high-resolution remote sensing images and GIS spatial analysis technology, an integrated expansion degree index model was established based on the existing indicators of construction land expansion, and the general and spatiotemporal differentiation characteristics of construction land expansion in the Town in three time periods of 1980-2009 were quantitatively analyzed. In 1980-2009, with the acceleration of rural urbanization and industrialization, the area of construction land in the Town increased significantly by 19.24 km2, and especially in 2001-2009, the expanded area, expanded contribution rate, and expansion intensity reached the maximum. The construction land expansion had an obvious spatial differentiation characteristic. In 1980-1991, the newly increased construction land mainly concentrated in town area. After 1991, the focus of construction land gradually spread to the villages with developed industries. Most of the increased construction lands were converted from paddy field and dry land, accounting for 88.1% of the total increased area, while the contribution from other land types was relatively small.

Interaction between |pest and fire disturbances in Huzhong area of Great Xing’an Mountains: Long-term simulation.

2011, 22(03):  585-592. 

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Forest pest and forest fire are the two major disturbances of forest ecosystem, and there exists definite interaction between the disturbances at large spatial and temporal scales. In this paper, the spatially intuitional landscape model (LANDIS) was adopted to simulate the long-term (300 years) interaction between forest pest and forest fire in Huzhong area of Great Xing’an Mountains. The results showed that  pest disturbance decreased the fine fuel load, increased the coarse fuel load at the early (0-100 a) and middle (100-200 a) stages of simulation course, and decreased the fire frequency at the early and middle stages. The fire frequency under different forest pest disturbance scenarios was similar at the later stage (200-300 a) of simulation course. Pest disturbance decreased the fire intensity and fire risk class at the early and later stages, but increased the fire intensity and fire risk class at the middle stage. Fire suppression could increase the occurrence area of forest pest, and thus, it was suggested that forest managers should take appropriate measures to prevent insect pest, not solely with the focus on fire suppression but also adopting the forest fire management measures such as taking off coarse fuel and implementing prescribed fire to ensure the sustainable development of forest ecosystem.

¹³⁷Cs profile distribution character and its implication for soil erosion on Karst slopes of Northwest Guangxi.

2011, 22(03):  593-599. 

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This paper studied the profile distribution characters of ¹³⁷Csand soil organic carbon (SOC) on the Karst slopes and in the fissures in typical peak-cluster depression in Northwest Guangxi, aimed to approach the applicability of ¹³⁷Csmethod on Karst slopes and the implication of ¹³⁷Csfor the characteristics of slope soil erosion. In all test profiles, there was a significant correlation between ¹³⁷Cs and SOC, indicating that both of them might have the same loss pathway. On the slopes under secondary forests, ¹³⁷Cs mainly existed within the depth 0-24 cm. On the upper middle and middle slope sites, ¹³⁷Cs had an exponential decrease with depth, indicating no or slight surface erosion; while on the foot slope site, the distribution pattern of ¹³⁷Cs indicated severer erosion. On the slopes with cultivated lands, ¹³⁷Cs distributed uniformly within the plough layer. In the upper middle and middle slopes profiles, ¹³⁷Cs mainly existed in the depth around 15 cm and far less than the background value, indicating severe soil erosion; while in foot slope profiles, ¹³⁷Cs was aggraded to the depth 45 cm. A discontinuous distribution of ¹³⁷Cs in the profiles was detected on the foot slopes under secondary forests, on the upper middle and foot slopes of cultivated lands, and in the fissures, indicating that the soil particles on Karst slopes had a trend of losing with rainwater to the underground, but the loss quantity was negligible, compared with surface erosion.

Soil heterotrophic respiration and its sensitivity to soil temperature and moisture in Liquidambar formosana and Pinus massoniana forests in hilly areas
 of southeast Hubei Province, China.

2011, 22(03):  600-606. 

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Field monitoring was conducted to study the annual dynamics of soil heterotrophic respiration and soil temperature and moisture in Liquidambar formosana and Pinus massoniana forests in hilly areas of southeast Hubei Province, China. At the same time, laboratory experiment was performed to study the heterotrophic respiration rate along soil profile, and the sensitivity of surface soil (0-5 cm) heterotrophic respiration to soil temperature and moisture. Then, a model was established to valuate the potential effects of warming change on the soil heterotrophic respiration in study area. In L. formosana and P. massoniana forests, the soil heterotrophic respiration rate in 0-5 cm layer was 2.39 and 2.62 times, and 2.01 and 2.94 times of that in 5-10 cm and 10-20 cm layers, respectively, illustrating that soil heterotrophic respiration  mainly occurred in 0-5 cm surface layer. The temperature sensitivity factor (Q₁₀) of soil heterotrophic respiration in 0-5 cm, 5-10 cm, and 10-20 cm layers was 2.10, 1.86, and 1.78 in L. formosana forest, and 1.86, 1.77, and 1.44 in P. massoniana forest, respectively. The relationship between surface soil heterotrophic respiration and temperature (T) well fitted exponential function R=αexp (βT), and that between surface soil heterotrophic respiration and moisture (W) well fitted quadratic function R=a+bW+cW². Therefore, the relationship of surface soil heterotrophic respiration with soil temperature and moisture could be described by the model lnR=a+bW+cW²+dT+eT², which suggested that the response of soil heterotrophic respiration to soil moisture was depended on soil temperature, i.e., the sensitivity decreased with decreasing soil temperature. The calculation of the annual soil heterotrophic respiration rate in the two forests with the established model showed that the calculated respiration rate was a slightly higher in L. formosana forest but close to the measured one in P. massoniana forest, illustrating the applied importance of the model. Our results suggested that the soil heterotrophic respiration in the L. formosana and P. massoniana forests in hilly areas of southeast Hubei Province would have an obvious increase under the background of global warming.

Energy balance and evapotranspiration in broad-leaved Korean pine forest in Changbai Mountains.

2011, 22(03):  607-613. 

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Based on the continuous measurements of an open-path eddy covariance system, this paper analyzed the characteristics of energy balance components and evapotranspiration in a broad-leaved Korean pine forest in Changbai Mountains in 2008, as well as the differences of  energy balance components and evapotranspiration between growth season and dormant season. For the test forest, the year-round energy balance closure was 72%, being at a medium level, compared to the other studies in the Fluxnet community. The energy balance components had significant differences in their diurnal and seasonal variations. In growth season, turbulent energy exchange was dominated by upward latent heat flux, accounting for 66% of available energy; while in dormant season, the turbulent energy exchange was dominated by upward sensible heat flux, accounting for 63% of available energy. The accumulated annual evapotranspiration in the study site in 2008 was 484.7 mm, occupying 87% of the precipitation at the same time period (558.9 mm), which demonstrated that evapotranspiration was the main water loss item in temperate forests of Northern China.

Soil heavy metals concentration in different type plantations in Harbin City.

2011, 22(03):  614-620. 

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In order to understand the soil heavy metals characteristics in different type plantations in Harbin City, 0-10 cm and 10-30 cm soil samples were collected from eight mono-cultured plantations (Larix gmelinii, Pinus sylvestris var. mongolica, Pinus tabulaeformis var. mukdensis, Phellodendron amurense, Juglans mandshurica, Fraxinus mandshurica, Betula platyphylla, and Quercus mongolica) and one mixed plantation (P. sylvestris var. mongolica + F. mandshurica + Pinus koraiensis + P. amurense + B. platyphylla) established in the Urban Forestry Demonstration Research Base of Northeast Forestry University in the 1950s to analyze the concentrations of Cu, Zn, Cd, Ni, Pb, and As, and the comprehensive pollution index was used to assess the soil heavy metals pollution in the plantations, based on the background values of black soil in the City. There existed significant differences in the heavy metals concentration in the same soil layers among different type plantations. In the test plantations, the concentrations of soil heavy metals except As and Ni tended to decrease with soil depth. In the same soil layers, Zn had the highest concentration (62.29-126.35 mg·kg^-1), while Cd had the lowest one (0.06-0.47 mg·kg^-1). The abundance and accumulation tendency of test heavy metals in the plantations was in the order of Zn>Pb>Cu(Ni)>Ni(Cu)>As>Cd, and Cd＞Pb＞Zn＞Cu＞Ni＞As, respectively. There existed positive correlations among soil Cu, Zn, Pb, and Cd concentrations in the plantations except F. mandshurica, and the concentrations of these four heavy metals in the plantations except F. mandshurica and Q. mongolica  were positively correlated with soil organic matter, N, P, and K. The concentrations of soil Cd, Pb, Zn, and Cu were higher than the background values, suggesting the anthropogenic inputs; while those of Ni and As were similar to or lower than the background values, suggesting the origin from soil materials. The soil comprehensive pollution index of the plantations was decreased in the order of F. mandshurica >P. amurense >mixed plantation >J. mandshurica >P. sylvestris var. mongolica >P. tabulaeformis var. mukdensis >L. gmelinii >B. platyphylla > Q. mongolica.

Vegetation net primary productivity in Northeast China in 2000-2008: Simulation and seasonal change.

2011, 22(03):  621-630. 

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By using GLOPEM-CEVSA model, the spatiotemporal pattern and its affecting factors of the vegetation net primary productivity (NPP) in Northeast China in 2000-2008 were simulated, and, taking four forest ecosystem stations (Daxing’anling, Laoyeling, Liangshui and Changbai Mountains) as the cases, the seasonal changes and their main driving force of forest NPP in Northeast China were studied. In 2000-2008, the annual averaged vegetation NPP in the region was 445 gC·m^-2·a^-1, being the highest in the areas from Changbai Mountains to Xiaoxing’anling Mountains and parts of Sanjiang Plain, followed by in the areas from Changbai Mountains to Liaohe River Plain, eastern Songnen Plain, Sanjiang Plain, and Daxing’anling Mountain, and the lowest in the sparse grass and desert areas in the west. Forest ecosystem had the highest annual averaged NPP, followed by shrub, cropland and grassland, and desert. In forest ecosystem, coniferous and broad-leaf mixed forests had the highest annual averaged NPP (722 g C·m^-2·a^-1), while deciduous needle-leaf forest had the lowest one (451 g C·m^-2·a^-1). During the study period, no significant inter-annual changes were observed in the forest NPP though it was higher in 2007 and 2008 probably due to the increased air temperature (1 ℃-2 ℃ higher than that in other years). The beginning time of forest growth season in Northeast China advanced gradually from north to south, and the growth season became longer.

Effects of simulated nitrogen deposition on soil acid phosphomonoesterase activity and soil available phosphorus content in subtropical forests in Dinghushan Mountain.

2011, 22(03):  631-636. 

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An in situ field experiment was conducted to study the effects of simulated nitrogen (N) deposition on soil acid phosphomonoesterase activity (APA) an
d soil available phosphorous (AP) content in Pinus massoniana forest (PF), coniferous and broad-leaved mixed forest (MF), and monsoon evergreen broad-leaved forest (MEBF) in Dinghushan Mountain. In PF and MF, three treatments were installed, i.e., CK (0 kg N·hm^-2·a^-1), low N (50 kg N·hm^-2·a^-1), and medium N (100 kg N·hm^-2·a^-1); in MEBF, four treatments were installed, i.e., CK, low N, medium N, and high N (150 kg N·hm^-2·a^-1). The soil APA and soil AP content decreased with soil depth. The soil APA was the highest in MEBF, while the AP content had no significant difference in the three forests. The effects of N addition on soil APA differed with forest types. In MEBF, the APA was the highest (19.52 μmol·g^-1·h^-1) in low N treatment; while in PF and MF, the APA was the highest (12.74 and 11.02 μmol·g^-1·h^-1, respectively) in medium N treatment. In the three forests, soil AP content was the highest in low N treatment, but had no significant differences among the N treatments. There was a significant positive correlation between soil APA and soil AP content.

Spatiotemporal variations of aboveground biomass and leaf area index of typical grassland in tower flux footprint.

2011, 22(03):  637-643. 

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By using cyclic sampling method, the aboveground biomass and leaf area index (LAI) of typical grassland in tower flux footprint were measured at three growth stages, i.e., early July (July 2-7), late July (July 20-26), and late August (Aug. 25-30), with their spatial patterns analyzed by geostatistics. At the three stages, the aboveground biomass of the grassland kept rising, while the LAI decreased after an initial increase. Both the two variables had good spatial autocorrelation, with similar spatial pattern and temporal evolution trend, and changed from stripe to patch. From early July to late August, the C₀/(C₀+C) of the aboveground biomass and LAI all decreased significantly, indicating that the spatial autocorrelation of the two variables changed from medium to high. The change ranges of the two variables gradually decreased, presenting the decrease of spatial continuity. The fractal dimension (D) also decreased gradually, suggesting the increase of spatial dependence. Topography and field management were the main factors affecting the spatial distribution of aboveground biomass and LAI, which induced the spatial variability of water and heat, and further, affected the grass growth.

Photosynthesis and transpiration characteristics of female and male Trichosanthes kirilowii Maxim individuals.

2011, 22(03):  644-650. 

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A field research was conducted on the photosynthesis and transpiration characteristics of dioecious Trichosanthes kirilowii individuals at four key development stages. At vegetative growth stage, the photosynthesis rate, transpiration rate, stomatal conductance, and water use efficiency of male individuals were higher than those of female individuals, and hence, male individuals entered into reproductive growth stage 22 days earlier than female individuals. After entering into reproductive growth stage, male individuals had higher photosynthesis rate, transpiration rate, and stomatal conductance, but slightly lower water use efficiency than female individuals. As the female individuals started to reproductive growth, their photosynthesis rate and water use efficiency were significantly lower, while the transpiration rate and stomatal conductance were higher than those of the male individuals. The effects of climate factors on the growth and development of T. kirilowii mainly occurred at its vegetative growth and early reproductive growth stages, and weakened at later reproductive growth stages. Higher temperature and lower relative humidity benefited the growth and development of T. kirilowii, and illumination could enhance the photosynthesis rate of T. kirilowii, especially its male individuals. After entering into reproductive growth stage, the photosynthesis rate of male individuals increased significantly with increasing illumination, but that of female individuals only had a slight increase, and the transpiration rate of male individuals as well as the photosynthesis rate of female individuals all increased significantly with increasing temperature.

Effects of drought stress on physiological and biochemical parameters of Dahlia pinnata. 

2011, 22(03):  651-657. 

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Taking Dahlia pinnata ‘Fenxishi’ as test material, this paper studied its leaf physiological and biochemical responses to different degrees of drought stress and re-watering. With the increasing extent and duration of drought stress, the leaf relative water content, water potential, and chlorophyll content of D. pinnata ‘Fenxishi’ decreased significantly, leaf relative electric conductivity and malondialdehyde (MDA) content had a significant increase, plasma membrane was damaged, and massive ions were leaked out. The damage of plasma membrane was most serious under severe stress, and could not recover to the control level after re-watering. The leaf soluble sugar and proline contents also increased significantly with increasing extent and duration of drought stress. Especially for proline content, it was increased significantly in the later period of moderate and severe stresses, suggesting its lower sensitivity to water deficit. The leaf soluble protein content had a trend of down-up-down, while the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) decreased after an initial increase. There were some differences in the responses of the three enzymes to drought stress and reactive oxygen, exhibiting their coordinating role.

Soil organic carbon content and its distribution pattern in Hangzhou Bay coastal wetlands.

2011, 22(03):  658-664. 

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In this paper, the soil organic carbon (SOC) content and its distribution pattern in the natural intertidal zones and reclaimed wetlands of Hangzhou Bay were studied, aimed to explore the effects of vegetation succession, exotic species invasion, and reclamation on the SOC in costal wetlands of the Bay. In intertidal zones, the surface SOC content ranged from 4.41 to 8.58 g·kg^-1, with an average of 6.45 g·kg^-1, and differed significantly under different vegetations, with a tendency of under Phragmites australis (8.56±0.04 g·kg^-1) > Spartina alterniflora (7.31±0.08 g·kg^-1) > Scirpus mariqueter (5.48±0.29 g·kg^-1) > mudflats (4.47±0.09 g·kg^-1); in reclaimed wetlands, the surface SOC content was 7.46±0.25 g·kg^-1 in the 1960s, 1.96±0.46 g·kg^-1 in the 1980s, and 5.12±0.16 g·kg^-1 in 2003, showing a trend of increased after an initial decrease with increasing reclamation year. The SOC in the profiles all showed a decreasing trend from the surface to the bottom. The SOC in intertidal zones and reclaimed wetlands was significantly negatively correlated with soil pH, and positively correlated with soil total nitrogen (TN), suggesting a large reserve of organic nitrogen in TN. The correlation between SOC and soil C/N ratio was not obvious in intertidal zones, but significantly positive in reclaimed wetlands, indicating that reclamation affected soil C/N ratio to a certain extent. This study showed that in the intertidal zones, soil carbon sequestration capacity increased gradually with plant community succession. However, the invasion of exotic species Spartina alterniflora might decrease the capacity of carbon sequestration in intertidal zones. It was also found that the changes of soil moisture content, particle composition, vegetation coverage, and reclamation history were the main factors affecting the SOC distribution in reclaimed wetlands.

Profile distribution of organic carbon and nitrogen in major soil types in the middle of Qilian Mountains.

2011, 22(03):  665-672. 

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This paper studied the distribution patterns of organic carbon (OC), total nitrogen (TN), NH₄⁺-N, and NO₃^--N in the profiles of brown calcic soil, grey cinnamon soil, chestnut soil, and alpine meadow soil in the middle of Qilian Mountains. In all test soils, the contents of OC, TN, NH₄⁺-N, and NO₃^--N decreased with increasing soil depth, and the accumulation and decomposition of OC and various N forms differed with soil types. The average content of OC in different soil profiles changed from 14.01 to 41.17 g·kg^-1, and was in the order of grey cinnamon soil > alpine meadow soil > chestnut soil > brown calcic soil; the average content of TN changed from 1.28 to 2.73 g·kg^-1, with a sequence of alpine meadow soil > grey cinnamon soil > chestnut soil > brown calcic soil. The C/N ratio was from 11.33 to 19.22, with the order of grey cinnamon soil > chestnut soil > alpine meadow soil > brown calcic soil. NH₄⁺-N content changed from 5.80 to 8.40 mg·kg^-1, and was in the order of brown calcic soil > alpine meadow soil > chestnut soil > grey cinnamon soil; NO₃^--N content changed from 6.57 to 15.11 mg·kg^-1, being in the order of chestnut soil > alpine meadow soil > brown calcic soil > grey cinnamon soil. The ratio of NO₃^--N to NH₄⁺-N was 1.00-2.69, with the sequence of grey cinnamon soil > chestnut soil > alpine meadow soil > brown calcic soil. The OC and N contents in the same soil types differed significantly with the conditions of climate, vegetation, and topography (e.g., slope aspect and slope position). Correlation analysis showed that there were highly significant positive correlations between OC, TN, and NH₄⁺-N, but these three items had no significant positive correlations with NO₃^--N. Furthermore, there were highly significant positive correlations between available K, NH₄⁺-N, and NO₃^--N and between available P and OC, significant positive correlations between available P, TN, and NH₄⁺-N, but no significant correlations between pH, total K, and total P and OC and N.

Effects of nitrogen application and elevated atmospheric CO₂ on electron transport and energy partitioning in flag leaf photosynthesis of wheat.

2011, 22(03):  673-680. 

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Wheat (Triticum aestivum) plants were pot-cultured in open top chambers at the nitrogen application rate of 0 and 200 mg·kg^-1 soil and the atmospheric CO₂ concentration of 400 and 760 μmol·mol^-1. Through the determination of flag leaf nitrogen and chlorophyll contents, photosynthetic rate (P_n)-intercellar CO₂ concentration (C_i) response curve, and chlorophyll fluorescence parameters at heading stage, the photosynthetic electron transport rate and others were calculated, aimed to investigate the effects of nitrogen application and elevated atmospheric CO₂ concentration on the photosynthetic energy partitioning in wheat flag leaves. Elevated atmospheric CO₂ concentration decreased the leaf nitrogen and chlorophyll contents, compared with the ambient one, and the chlorophyll a/b ratio increased at the nitrogen application rate of 200 mg·kg^-1. With the application of nitrogen, no evident variations were observed in the maximal photochemical efficiency (F_v/F_m), maximal quantum yield under irradiance (F_v′/F_m′) of PSⅡ reaction center, photochemical fluorescence quenching coefficient (q_p), and actual PSⅡ efficiency under irradiance (Φ_PSⅡ) at elevated atmospheric CO₂ concentration, and the total photosynthetic electron transport rate (J_F) of PSⅡ reaction center had no evident increase, though the non-photochemical fluorescence quenching coefficient (NPQ) decreased significantly. With no nitrogen application, the F_v′/F_m′, Φ_PSⅡ, and NPQ at elevated atmospheric CO₂ concentration decreased significantly, and the J_F had a significant decrease though the F_v/F_m and q_p did not vary remarkably. Nitrogen application increased the J_F and photochemical electron transport rate (J_C); while elevated atmospheric CO₂ concentration decreased the photorespiration electron transport rate (J₀), Rubisco oxidation rate (V₀), ratio of photorespiration to photochemical electron transport rate (J₀/J_C), and Rubisco oxidation/carboxylation rate (V₀/V_C), but increased the photochemical electron transport rate (J_C) and Rubisco carboxylation rate (V_C). It was concluded that elevated atmospheric CO₂ concentration decreased the leaf nitrogen and chlorophyll contents, while nitrogen application increased the photosynthetic electron transport rate of PSⅡ reaction center significantly, and promoted the photosynthetic electron flow towards photochemistry, making more photosynthetic electron take part in Rubisco carboxylation and leading to the significant increase of P_n.

Effects of asymmetric warming on the growth characteristics and yield components of winter wheat under free air temperature increased.

2011, 22(03):  681-686. 

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In 2007-2009, a field warming experiment was performed in Nanjing of Jiangsu Province, China to investigate the effects of asymmetric warming (all-day
 warming, AW; daytime warming from 6:00 to 18:00, DW; and nighttime warming from 18:00 to 6:00, NW) on the growth and development of winter wheat under free air temperature increase (FATI). Asymmetric warming increased the effective tillers and decreased the ineffective tillers. In CK plot, the ineffective tillers were 2.6, 1.7 and 3.5 times of those in AW, DW and NW plots, while the effective tillers were decreased by 13.7%, 3.2%, and 0.5%, respectively. Asymmetric warming also increased the plant height, flag leaf area, and the total green leaf area and green leaf ratio at flowing stage. In treatments AW, DW, and NW, the plant height was increased by 5.6%, 4.5%, and 1.3%, flag leaf area increased by 45.7%, 39.4% and 26.1%, total green leaf area increased by 25.1%, 29.8%, and 17.3%, and green leaf ratio increased by 37.7%, 43.3%, and 38.7%, respectively, compared with CK. As for the yield components, the spikelet number per panicle and the filled grain number per panicle in treatments AW, DW and NW were increased by 4.1%, 5.7%, and 1.7%, and by 2.2%, 5.3%, and 2.6 %, respectively. Though the grain/leaf ratio in treatments AW, DW, and NW was decreased by 15.3%, 8.5%, and 11.3%, the thousand-grain mass  in the treatments was increased by 6.9%, 6.2% and 11.8%, and thus, the yield per unit was increased by 27.0%, 40.1%, and 18.3%, respectively, compared to the CK. Our results suggested that under anticipated warming, the winter wheat productivity in eastern China would be further enhanced.

Effects of coated controlled release urea combined with conventional urea on winter wheat growth and soil NO₃^--N.

2011, 22(03):  687-693. 

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Field experiments were conducted to study the effects of different dosages coated controlled release urea (PCU60, 60 d release duration) combined with conventional urea (U) used as basal on the winter wheat grain yield, nitrogen (N) recovery rate, and soil NO₃^--N content, etc. Five treatments were installed, i.e., U (CK), 10% PCU60+90 %U (PU₁), 20% PCU60+80% U (PU₂), 30% PCU60+70% U (PU₃), and 40% PCU60+60% U (PU₄). In the meantime, a comparative analysis was also carried out on the PCU60 N release characteristics under field condition and in 25 ℃ static water. At the same N dosage, all the test indices in treatment PU₄ were significantly higher, with the grain yield, N recovery rate, total N accumulation amount, total tiller number and aboveground biomass at ripening stage, and economic benefit increased by 5.6%, 14.6%, 7.2%, 2.6%, 7.5%, and 984.3 yuan·hm^-2, respectively, compared with those in treatment U. The accumulation amount of NO₃^--N in 0-100 cm soil layer in all treatments ranged in 39.70-49.93 kg·hm^-2, and was the lowest (39.70 kg·hm^-2) in treatment PU₄. The N release pattern of PCU60 under field condition better fitted the N absorption characteristics of winter wheat.

Differences in water consumption characteristics and grain yield of different wheat cultivars.

2011, 22(03):  694-700. 

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A field experiment with 10 wheat cultivars was conducted to study  the water consumption characteristics at different growth stages and the differences in the grain yield of the cultivars. Three irrigation treatments were installed, i.e., no irrigation (W₀), irrigation before sowing and at jointing stage (W₁), and irrigation before sowing and at jointing and anthesis stages (W₂), with irrigation amount 60 mm each time. Based on the cluster analysis with the parameters grain yield and water use efficiency (WUE) in the three treatments, the test ten cultivars could be divided into three groups, i.e., high yield and high WUE (Group I), high yield and medium WUE (Group Ⅱ), and medium yield and low WUE (Group Ⅲ). The average values of grain yield and WUE in each group were calculated to elucidate the water consumption characteristics of the three groups. In treatment W₀, the total water consumption amount in the whole growth period, the water consumption amount from anthesis to maturing stages and its proportion to the total water consumption amount of Group I were lower than those of Group Ⅱ and Group Ⅲ, but the grain yield of Group I was the highest. In treatment W₁, the water consumption amount from jointing to anthesis stages and its proportion to total water consumption amount of Group I were lower than those of Group Ⅱ and Group Ⅲ, but the water consumption amount from anthesis to maturing stages had no significant differences among Group I, Group Ⅱ, and Group Ⅲ. In treatment W₂, the total soil water consumption amount, water consumption amount from jointing to anthesis stages and its proportion to total water consumption amount of Group I were lower than those of Group Ⅱ and Group Ⅲ, while the water consumption amount from anthesis to maturity stages and its proportion to total water consumption amount of both Group I and Group Ⅲ were lower than those of Group Ⅱ. In terms of high-yield and water-saving under the present experimental condition, it was implicated that the most appropriate cultivars might fall into the Group I with high yield and high WUE, and the most appropriate irrigation regime with high yield and low water consumption was treatment W₁, i.e., irrigated 60 mm each time before sowing and at jointing stage.

Effects of high temperature on leaf photosynthetic characteristics and photosystemⅡ photochemical activity of kernel-used apricot.

2011, 22(03):  701-706. 

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In order to explore the photosynthetic adaption mechanisms of kernel-used apricot under high temperature stress, gas exchange technique and chlorophyll fluorescence transient technique (JIP-test) were adopted to study the leaf photosynthetic characteristics and photosystemⅡ (PSⅡ) photochemical activity of 4 year-old ‘Chaoren’ (Armeniaca vulgaris × sibirica) growing on Horqin sandy land at 25 ℃, 30 ℃, 40 ℃, and 50 ℃. Within a definite temperature range, and as the temperature increased, the ‘Chaoren’ could enhance its leaf photosynthetic pigments content and ratio to maintain the light absorption, transfer, and conversion, and thereby, to ensure the function of photosynthetic apparatus. However, when the temperature exceeded the physiological adjustment threshold of leaves, the chlorophyll began to be decomposed, net photosynthetic rate (P_n) declined obviously, and intercellular CO₂ concentration (C_i) increased, indicating that the decline in photosynthesis was limited by mesophyll factor. At 40 ℃, the density of PSⅡ reaction centers per excited cross-section (RC/CS_o) dropped distinctly; and at 50 ℃, the K phase (W_k) and J phase (V_j) in the O-J-I-P chlorophyll fluorescence transients increased distinctly, indicating that high temperature damaged the oxygen-evolving complex (OEC), donor sides, and PSⅡ reaction centers. In addition, the minimum chlorophyll florescence (F_o) at 50 ℃ increased significantly by 1.26 times, compared with the control, and the maximum photochemical efficiency (F_v/F_m) and performance index (PI_ABS) reduced to 37.9% and 10.3% of the control, respectively. High temperature injured the function of the donor and acceptor sides in the PSⅡ of photosynthetic apparatus, leading to the decrease of photosynthetic efficiency, and being one of the main mechanisms for the damage of photosynthetic apparatus in kernel-used apricot leaves under high temperature stress.

Thermal dissipation pathway in cucumber seedling leaves under hypoxia stress.

2011, 22(03):  707-712. 

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A water culture experiment was conducted to study the relationship between photosynthetic thermal dissipation and xanthophyll cycle in cucumber seedling leaves under hypoxia stress (the dissolved oxygen concentration in nutrient solution was 0.9-1.1 mg·L^-1). Under the hypoxia stress, there was a significant decrease in the quantum yield of PSⅡ photochemistry rate (Φ_PSⅡ), net photosynthetic rate (P_n) under saturation light intensity, quanta yield (AQY), and maximal photochemical efficiency (F_v/F_m), suggesting that the photoinhibition of the seedling leaves was induced. Meanwhile, the thermal dissipation (NPQ) and the allocation of dissipation energy (D) by antenna increased, but the photochemical quenching apparent (q_P) decreased, suggesting the enhancement of thermal dissipation in cucumber leaves under hypoxia stress. A positive correlation was observed between NPQ and xanthophyll de-epoxidation state (DEPS), and both of them were promoted by ascorbic acid (AsA) and inhibited by 1,4-dithiothreitol (DTT), suggesting that xanthophyll cycle was the major pathway of photosynthetic thermal dissipation in cucumber seedling leaves under hypoxia stress.

Effects of reduced nitrogen application on the yield, quality, and economic benefit of sugarcane intercropped with soybean.

2011, 22(03):  713-719. 

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A two-factor field experiment of randomized block design was conducted in Guangzhou to investigate the effects of reduced nitrogen application on the
yield, quality, and total biomass dynamic of sugarcane as well as the economic benefit of the sugarcane population under different sugarcane/soybean intercropping patterns. Neither N application nor intercropping pattern had significant effects on the yield and quality of sugarcane, and no significant differences were observed in the yield and quality of sugarcane among all treatments. The land equivalent ratio (LER) of sugarcane/soybean intercropping at different N application levels was from 1.36 to 2.12, suggesting that sugarcane/soybean intercropping had higher LER than monoculture sugarcane. The total dry matter (except root) of sugarcane in all treatments increased with plant growth, and the growth pattern fitted sigmoid function. At lower nitrogen application level, the eigenvalues of the dynamic dry matter accumulation model were more coordinative, compared with those at higher nitrogen application level, which meant that in the later case, sugarcane had an advanced peak growth time and shortened fast-growth duration
, and thereby, its yield decreased. Therefore, it was possible to reasonably adjust nitrogen application level to improve the eigenvalues of the sugarcane dynamic dry matter accumulation model, and accordingly, to achieve high yield. The population economic benefit under sugarcane/soybean intercropping was 3.2%-26.3% higher at lower than at higher nitrogen application level, suggesting the increase of the economic benefit of sugarcane population under reduced nitrogen application. Among the treatments, 1:2 sugarcane/soybean intercropping had the best economic benefit.

Yield loss model and yield loss mechanism of high-yielding summer maize infected by Physoderma maydis.

2011, 22(03):  720-726. 

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A total of 21 different disease-grading summer maize groups were formed by fixed-point natural infection of maize brown spot in the field, and mass
loss estimation models of single ear mass and 100-grain mass were constructed by stepwise regression with DPS software. The mass loss estimation models of single ear and 100-grain were Y=-4.012+0.377X₁-0.228X₂+0.694X₃-0.144X₄ and Y=-4.536+0.173X₁+0.188X₂+0.248X₃-0.034X₄, respectively, where Y was yield loss rate, X₁ was the disease index at flowering stage, X₂ was the disease index at pollination stage, X₃ was the disease index at filling stage, and X₄ was the disease index at dough stage. The measured relationships between the disease indices at differen
t growth stages and the mass loss for single ear and 100-grain coincided well with the modeling results. Maize brown spot directly affected the net photosynthetic rate of ear height leaf and the activities of RuBP carboxylase and PEP carboxylase. The higher the disease-grade, the lower the net photosynthetic rate and the activities of the two enzymes were.

Microbial diversity in rhizosphere soil of transgenic Bt rice based on the characterization of phospholipids fatty acids.

2011, 22(03):  727-733. 

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Taking non-transgenic parental rice as the control, and by using ¹³C pulse-chase labeling method coupled with phospholipid fatty acid (PLFA) analysis, this paper studied the effects of transgenic Bt rice on the microbial diversity in rhizosphere soil. The results showed that in the rhizosphere soils of
transgenic Bt rice and its non-transgenic parent, saturated  PLFAs and branched  PLFAs were the main, followed by monounsaturated  PLFAs, and polyunsaturated  PLFAs. A significantly lower amount of Gram-positive bacterial PLFAs and a higher amount of Gram-negative bacterial PLFAs were observed in the rhizosphere soil of transgenic Bt rice at its seedling, booting, and heading stages, as compared with the control. In the whole growth period of rice, transgenic Bt gene had no significant effects on the fungal and actinomycete PLFAs in rhizosphere soil, and no significant difference was
observed in the rhizosphere soil ¹³C-PLFA content between transgenic Bt rice and its non-transgenic parent. These findings indicated that the insertion of exogenous cry1Ab gene into rice only had temporary effects on the microbial community composition in the rhizosphere soil of rice.

Landscape ecological security pattern during urban expansion of Nanchong City.

2011, 22(03):  734-740. 

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Based on the theory of landscape ecological security pattern and the RS and GIS techniques, this paper analyzed the distribution of ecological security grades in Nanchong City, taking six elements including terrain condition, flood hazard, soil erosion, vegetation cover, geological disaster, and biological protection as the ecological constraints (or determinants) of urban expansion. According to the minimum cumulative resistance model, the ecological corridors and ecological nodes were built to strengthen the space contact of ecological network, and, on the basis of the protection of ecological safety, the reasonable trend of urban expansion and the optimization of space layout were investigated. The results showed that the ecological security of Nanchong City was quite good, with the regions of low ecological security mainly distributed in the west suburban mountains and the downstream region of Jialing River in the south of the City. Ecological elements were the most important constraints for the future expansion of urban space. There were more spaces for the urban expansion in the southern and northern parts of Nanchong City. To develop satellite towns would be the best selection to guarantee the ecological security of the City.

Landscape spatial pattern of typical loess hilly-gully watershed based on ALOS imagery.

2011, 22(03):  741-747. 

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Based on the ALOS satellite medium and high resolution images, seven landscape types closely related to the ecosystem restoration, farming, and living of Yan’gou watershed, a typical watershed in loess hilly-gully region, were interpreted. The landscape pattern and function of the watershed in 2007 were analyzed with the landscape indices of diversity and heterogeneity, and the landscape distribution suitability of the whole and parts of the watershed were evaluated, combined with the digital elevation model (DEM) data. The results showed that the dominant landscape types in the watershed were bush and forest, which were mainly distributed on the slopes with a gradient greater than 25 degrees. The patch fractal dimension of the watershed was 1.09, suggesting that the general landscape spatial pattern was stable. The area ratio of the three landscape functional types of eco-protection, product economy, and living service was 23:9:1. The suitability of the whole watershed landscape distribution was 0.76, suggesting that the overall landscape distribution was relatively reasonable. However, the land-use suitability of semi-shade slopes and of the areas with an altitude less than 900 m was lower, being 0.74 and 0.02, respectively.

Analysis on sustainable development of marine economy in Jiangsu Province based on marine ecological footprint correction model.

2011, 22(03):  748-754. 

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Based on the theories and methods of ecological footprint, the concept of marine ecological footprint was proposed. According to the characteristics of marine environment in Jiangsu Province, five sub-models of marine ecological footprints, including fishery, transporation, marine engineering construction, marine energy, and tidal flat, were constructed. The equilibrium factors of the five marine types were determined by using improved entropy method, and the marine footprints and capacities in Jiangsu Province from 2000 to 2008 were calculated and analyzed. In 2000-2008, the marine ecology footprint per capita in Jiangsu Province increased nearly seven times, from 36.90 hm² to 252.94 hm², and the ecological capacity per capita grew steadily, from 105.01 hm² to 185.49 hm². In 2000, the marine environment in the Province was in a state of ecological surplus, and the marine economy was in a weak sustainable development state. Since 2004, the marine ecological environment deteriorated sharply, with ecological deficit up to 109660.5 hm², and the sustainability of marine economy declined. The high ecological footprint of fishery was the main reason for the ecological deficit. Tidal flat was the important reserve resource for the sustainable development of marine economy in Jiangsu Province.

Coupling analysis of agro-ecolomic system in gully area of Loess Plateau in 1949-2008: A case study in Changwu County of Shaanxi Province.

2011, 22(03):  755-762. 

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Based on the analysis of the coercing and dynamic evolution relationships between agro-economic system and agro-ecological system, and by using modified entropy method, the weight of each evaluation index for the agro-ecolomic system in Changwu County of Shaanxi Province was determined, and, by employing coupling degree model, the coupling processes of agro-ecolomic system in the gullyarea of Loess Plateau were investigated. From 1949 to 2008, the agro-ecolomic system in the County experienced three stages of “traditional extensive agriculture”, “agricultural mechanization”, and “agricultural pre-modernization”. In corresponding to the implement of national macro policies, the coupling degree of the agro-ecolomic system reached two peaks standing for utmost increasing phase and three valleys standing for coordinate development phase. Periods 1955-1961 and 1984-1992 were the utmost increasing phases of the coupling degree; periods 1962-1965 and 1981-1983 were the rapid transition periods responding to the national-wide policies controlling; while periods 1949-1954 and 1966-1980 were the low-level coordinated development phases. Since 1993, the system had been in the harmonious phase by a spiral development. At present, the system had a potential risk of changing from the harmonious phase to the utmost development phase. Appropriate agricultural policies and better external environment could promote the stable development of the agro-ecolomic system on a harmonious level; otherwise, a retrogressive system might be expected.

Changes of China agricultural climate resources under the background of climate change. Ⅲ. Spatiotemporal change characteristics of agricultural climate resources in Northwest Arid Area.

2011, 22(03):  763-772. 

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By using the 1961-2007 daily weather data from 78 meteorological stations in Northwest Arid Area, this paper analyzed the spatiotemporal characteristics of agricultural climate resources,i.e., heat, light, and precipitation, in the area, both in the whole year and in temperature-defined growth seasons of chimonophilous and thermophilic crops. In 1961-2007, the mean annual temperature in the area had an increasing trend, and the climate tendency rate was 0.35 ℃·(10 a)^-1. The accumulated temperature in temperature-defined growth seasons of both chimonophilous and thermophilic crops also had an increasing trend, and the climate tendency rate was 67 and 50 ℃·d·(10 a)^-1, respectively. The annual sunshine hours in most stations of the research area had an obvious decreasing trend, but the sunshine hours during the temperature-defined growth seasons of chimonophilous and thermophilic crops had an increasing trend, except that in most regions of Xinjiang and east Ningxia Plain. The annual reference evapotranspiration in most regions of the study area tended to decrease, while the reference evapotranspiration during temperature-defined growth seasons of chimonophilous and thermophilic crops tended to decrease in the west but increase in the east. Compared with that in 1961-1980, the precipitation both in the whole year and in temperature-defined growth seasons of chimonophilous and thermophilic crops in 1981-2007 increased, and the increment reduced progressively from the northwest to the southeast.

A long distance colonization event of Chinese endemic bat Myotis davidii.

2011, 22(03):  773-778. 

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In order to reveal the population phylogenetic relationships and colonization history of Chinese endemic bat species Myotis davidii, a total of 126 samples from 14 populations in nationwide were collected in 2001-2009, taking the mitochondrial control region as the molecular marker. Based on the TCS network diagram of the mitochondrial DNA control region sequences, the 14 geographical populations were divided into three geographical regions, i.e., mid-east plain region, southwest plateau region, and south hills region. In the 53 haplotypes, the No. 14 in Zhejiang Province, No. 47 in Guizhou Province, and No. 50 in Guangdong Province were the ancestors in the three regions, respectively. Based on Geodis analysis, mismatch distribution analysis, and neutrality test, the population expansion events were found in mid-eastern plain region (76.12 and 79.17 ka BP) and southwest plateau (69.12 ka BP). In 61.24 ka BP, a long distance migration event originated from the southwest plateau region to the mid-east plain region occurred. The evidences of molecular biology, bionics, anatomy, and aerodynamics all revealed the long-distance migration capability of M. davidii.

Spatial pattern of Sitodiplosis mosellana and its egg parasitoids mixed population.

2011, 22(03):  779-784. 

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Geostatistis methods were adopted to analyze the spatial pattern of Sitodiplosis mosellana (Diptera: Cecidomyiidae) at its different development periods and of its egg parasitoids mixed population (Tetrastichus sp. and Platygaster error; Hymoneptera: Eulophidae and Platygastridae). The aggregated spatial arrangements for S. mosellana cocoon, adult, and larva and for egg parasitoids mixed population could be well described by spherical model, spherical-exponential model, linear sill model, and spherical-exponential model, respectively. The spatial dependence range of S. mosellana cocoon, adult at initial emergence period, adult at peak emergence period, and larva, and of egg parasitoids mixed population was 53.6, 190.6, 154.1, 4.2 and 280.3 m, and the aggregation intensity was 30.5%, 95.6%, 96.3%, 14.9% and 953%, respectively. The simulated maps of the spatial distribution produced by Kriging model could intuitively analyze the dynamic changes of S. mosellana at its different development periods and of egg parasitoids mixed population from the two aspects of time and space.

Self-pollution in Ruditapes philippinarum bottom-cultured area of Zhuanghe coast.

2011, 22(03):  785-792. 

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By using sediment trap and closed respirator, a year-round in situ investigation was made on the bio-deposition rate, ammonia excretion rate, and phosphate excretion rate in the Ruditapes philippinarum bottom-cultured area of Zhuanghe coast. The three test rates of R. philippinarum all showed obvious seasonal variability, with the bio-deposition rate ranged in 0.15-1.47 g·ind^-1·d^-1 (annual average 0.61 g·ind^-1·d^-1),ammonia excretion rate ranged in 0.02-0.40 mg·ind^-1·d^-1(annual average 0.17 mg·ind^-1·d^-1), and phosphate excretion rate ranged in 0.01-0.39 mg·ind^-1·d^-1 (annual average 0.13 mg·ind^-1·d^-1). Based on these, it was estimated that the annual bio-deposit production by the bottom-cultured R. philippinarum in Zhuanghe coast could reach as high as 5.46×10⁷ t dry mass, amounting to 9.07×10⁶  t organic matter (OM), 1.00×10⁶  t organic carbon (OC), or 1.18×10⁵ t organic nitrogen (ON), and the annual NH₄⁺-N and PO₄^3--P productions were 1.49×10⁴ t and 1.15×10⁴ t, respectively. Our results suggested that for the large scale and high density bivalve culture in China coasts, the potential impacts of self-pollutants by filter-feeding bivalves on the environment should not be neglected.

Abundance distribution of virioplankton in Yangtze River estuary and its adjacent East China Sea in summer and winter.

2011, 22(03):  793-799. 

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An investigation was made on the abundance distribution and its variation of virioplankton in the Yangtze River estuary and its adjacent East China Sea in summer 2006 and winter 2007. The virus direct count (VDC) was quantified by fluorescent microscopy. In summer 2006, the VDC was from 2.22×10⁶ to 9.97×10⁷ ind·ml^-1, being higher in the surface sea water of B area (122.5°-123.5° E); in winter 2007, the VDC was from 1.99×10⁶ to 2.66×10⁷ ind·ml^-1, being higher in coastal A area (120.5°-122.5° E) and decreased from nearshore waters to offshore waters. In summer, the VDC had close relationships with bacteriaplankton biomass and chlorophyll-a concentration but less relationship with nutrients concentration (P>0.05); in winter, the VDC was closely related to bacteriaplankton biomass and nutrients concentration but less related to chlorophyll-a concentration (P>0.05). The abundance distribution pattern of virioplankton showed significant seasonal variability, with the VDC significantly larger in summer than in winter (P<0.01), which was mainly decided by the distribution of the viral host, and partly by the nutrients concentration in wintertime.

Ecological effects of utilizing non-timber forest products.

2011, 22(03):  800-809. 

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Non-timber forest products (NTFPs) include all plant materials other than timber, such as seeds, flowers, fruits, leaves, roots, bark, latex, resins, and other non-wood plant parts. The significant role of NTFPs in improving local people’s lives and forest biodiversity conservation has been widely accepted. However, many studies in past decades indicated that NTFPs utilization had various ecological effects on different levels, from plant individual and population to community and forest ecosystem, depending not only on the plant parts extracted and their biological or ecological attributes, but also on the harvest forms. This paper reviewed the research progress about the effects of the utilization of NTFPs from biological and ecological aspects, and discussed some research problems and research priorities.

Ecological relationships between Bursaphelenchus xylophilus and its companion microorganisms.

2011, 22(03):  810-815. 

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Pine wood nematode Bursaphelenchus xylophilus is a notorious invasive species from North America, which can kill a large amount of pine trees and causes economic losses and ecosystem destruction. There is a close relationship and ecological interaction between B. xylophilus and its companion microorganisms. This paper listed the species of companion microorganisms, reviewed their important ecological roles in the propagation and pathogenicity of the nematode, and discussed the pine wilt disease from the viewpoint of microecosystem. The companion fungi can supply food for B. xylophilus, hold the cycle of second infection of the nematode, increase the proportions of dauer juveniles, and benefit the infection and distribution of B. xylophilus. The companion bacteria can enhance the pathogenicity of B. xylophilus, promote the propagation of the nematode, benefit the pinene degradation, and thereby, promote the adaptability of the nematode.

Recent advance in solidification/stabilization technology for the remediation of heavy metals- contaminated soil.

2011, 22(03):  816-824. 

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Remediation of heavy metals-contaminated soil is still a difficulty and a hotspot of international research projects. At present, the technologies commonly adopted for the remediation of contaminated sites mainly include excavation, solidification/stabilization (S/S), soil washing, soil vapor extraction (SVE), thermal treatment, and bioremediation. Based on the S/S technical guidelines of Unite State Environmental Protection Agency (EPA) and United Kingdom Environment Agency (EA) and the domestic and foreign patents, this paper introduced the concepts of S/S and its development status at home and abroad, and discussed its future development directions. Solidification refers to a process that binds contaminated media with a reagent, changing the media’s physical properties via increasing its compressive strength, decreasing its permeability, and encapsulating the contaminants to form a solid material. Stabilization refers to the process that involves a chemical reaction which reduces the leachability of a waste, chemically immobilizes the waste and reduces its solubility, making the waste become less harmful or less mobile. S/S technology includes cement solidification, lime pozzolanic solidification, plastic materials stabilization, vitrification, and regent-based stabilization. Stabilization (or immobilization) treatment processes convert contaminants to less mobile forms through chemical or thermal interactions. In stabilization technology, the aim of adding agents is to change the soil physical and chemical properties through pH control technology, redox potential technology, precipitation techniques, adsorption technology, and ion-exchange technology that change the existing forms of heavy metals in soil, and thus, reduce the heavy metals bioavailability and mobility. This review also discussed the S/S evaluation methods, highlighted the need to enhance S/S technology in the molecular bonding, soil polymers, and formulation of China’s S/S technical guidelines.

Cropping patterns of Bupleurum chinense in semi-arid region of Loess Plateau.

2011, 22(03):  825-828. 

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Field experiments were conducted to investigate the suitable cropping patterns of grain crops and medical plant Bupleurum chinense  in the semi-arid
region of the Loess Plateau. Three cropping patterns were designed, including corn-Bupleurum chinense intercropping (corn/Bupleurum chinense), wheat followed by soybean-Bupleurum chinense intercropping (wheat-soybean/Bupleurum chinense ), and sequential planting of Bupleurum chinense  (wheat-Bupleurum chinense ). Of the three patterns, wheat-soybean/Bupleurum chinense  was the best in economic yields and ecological benefits. Among the cultivars (cv. Lingchuan, Zuoquan and Wanrong) of Bupleurum chinense  tested, the cv. Wanrong originated from relatively high temperature region exhibited the highest yield, while the cv. Zuoquan originated from relatively low temperature region had the lowest one, indicating that introducing Bupleurum chinense  cultivars from the areas with higher temperature to lower temperature areas could increase their yield. The cropping pattern of wheat-soybean/Bupleurum chinense  was the most effective one, with the yield being 11.6% and 16.8% higher than that of corn/Bupleurum chinense and wheat-Bupleurum chinense , respectively.