Table of Content

10 June 2010, Volume 29 Issue 06

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Articles

Carbon storage and sequestration of tree layer in subtropical evergreen broadleaf forests in Ailao Mountain of Yunnan.

2010, 29(06):  1047-1053. 

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In order to understand the tree layer carbon storage and sequestration in the subtropical evergreen broadleaf forests in Ailao Mountain, an analysis was made on the tree layer carbon storage and sequestration in three dominant forests in the Mountain, based on the field surveys in 2005 and 2008. The tree layer carbon storage in the primary evergreen broadleaf forest, secondary Populus bonatii forest, and secondary Alnus nepalensis forest in the Mountain was 257.90, 222.95, and 105.39 t C·hm^-2, respectively. The tree layer carbon storage of the primary evergreen broadleaf forest was mainly contributed by the trees with DBH ≥91 cm (34.68%), while that of the two secondary forests was mainly contributed by the trees with DBH from 21 cm to 41 cm (77.29% for P. bonatii secondary forest, and 69.28% for A. nepalensis secondary forest), suggesting that the tree layer of primary evergreen broadleaf forest played an important role in the carbon storage in Ailao Mountain. The tree layers of the three forests all had the capability of carbon sequestration. The mean annual increment of tree layer carbon sequestration in primary evergreen broadleaf forest was 2.47 t C·hm^-2·a^-1, and that in the two secondary forests was about two times of the primary evergreen broadleaf forest, suggesting a great potential of carbon sequestration in secondary forests. Based on the above-mentioned results,it was estimated that the mean annual increment of tree layer carbon sequestration within the Ailao Mountain National Nature Reserve was 8.52×10.4 t C·a^-1.

Relationships between fir community characteristics and ecological factors in Miyaluo forest area of West Sichuan.

2010, 29(06):  1054-1060. 

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Fir forest is the zonal vegetation in West Sichuan alpine valley area. Based on the forest inventory data in Miyaluo, this paper analyzed the relationships between the tree height, DBH, volume, and distribution of fir forest and the ecological factors in the area, and discussed the most suitable habitats for the forest. It was shown that with increasing altitude, the tree height and DBH changed in single peak curve, while the volume had a fluctuated increase, which could be related to the characteristics of micro-environment and human disturbances. The suitable habitat of the fir forest was at an altitude ranged from 3500 to 4000 m a.s.l., with a soil depth from 50 to 79 cm, and a slope degree from 40° to 49°. In addition, the fir trees preferred the half-shady side of slope, or the superior shady side of mid- or top-slope. A large proportion of the fir forest concentrated within an altitude range from 3800 to 3900 m a.s.l.. Slope position was the most fundamental ecological factor affecting the fir forest community characteristics, followed by soil depth, slope, and aspect.

Ecological characteristics and areal types of permafrost wetland plants in Great Hing’an Mountains.

2010, 29(06):  1061-1067. 

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An investigation was made on the ecological characteristics and areal types of the plants in 24 permafrost wetlands in the Great Hing’an Mountains. There were 201 plant species, belonging to 40 families and 121 genera. The species of Compositae and Rosaceae were dominant, occupying 26.8% of the total. In five  life forms, hemicryptophytes occupied 71%, phanerophytes and geophytes occupied 13% and 12%, and chamaephytes and therophytes occupied 2%, respectively. In four hydro-ecotypes, mesophytes occupied 61%, and hygrophytes, helophytes, and xerophils occupied 28%, 8%, and 3%, respectively. In four areal types, the plants of temperate zone were the most. Due to the high altitude and high latitude, the plants of sub-frigid and frigid zones took second place. All the results indicated that the study area had a short summer and a long and cold winter, and the soil moisture tended to be moderate. This study would have important value to further studies on the environmental change and the degeneration of permafrost wetlands in the Great Hing’an Mountains.

Spatiotemporal expansion pattern and potential spread of invasive alien plant  |Erigeron annuus (Asteraceae) in China.

2010, 29(06):  1068-1074. 

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To understand the spatiotemporal expansion pattern of invasive species is of significance for the control of alien species invasion and spread. The aim of this research is to reconstruct the invasion and expansion processes and to predict the potential spread of Erigeron annuus, one of the threatening invasive plant species in China, and to identify and determine the possible modes of this species early introduction, subsequent expansion route, and potential spread. The reconstruction of the historical invasion processes of E. annuus in China showed that E. annuus first invaded Shanghai in 1886. After a lag phase of 50 years (1880s-1930s), this species expanded its distribution from China eastern coastal area toward inland, and until 2000, invaded 21 provinces. E. annuus would continue its expansion in China. Most areas in China, except Qinghai, Tibet, Inner Mongolia, Guangdong, Guangxi, and Heilongjiang, are likely to be invaded, and their adjacent areas, e.g., southern Hebei, northern Henan, Shanxi, Shaanxi, western-central Liaoning, and western Jilin, are most liable to be invaded, where urgent measures should be adopted to prevent further invasion of this species.

Vegetation gradient characteristics and soil water environment of oasis-desert transitional zone in Minqin.

2010, 29(06):  1075-1080. 

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The vegetation and soil water environment in Minqin oasis-desert transitional zone have obvious spatial heterogeneity with the increasing distance from oasis, and can be divided into 4 sections, according to the differentiation of landscapes. This paper studied the vegetation features in each of the sections, and the soil water features in the inter-dunes and shrub islands in the sections. In the transitional zone, the total coverage was about 36%, shrub coverage was 18.7%, and herbal coverage was 18.0%. The species richness was 19. From section 1 to section 4, the species composition, vegetation coverage, dominant species, and constructive species all exhibited the features corresponding to the stand conditions of each section, with a pattern of large shrub→ herb → shrub→ herb. Accordingly, the geomorphology showed the pattern of fixed →semi-shifting → semi-fixed → shifting. There were obvious differences in the vertical distribution of soil water content among the sections, and 5-60 cm soil layer was the main rainwater retention layer. Due to the occurrence of aquiclude, the soil water content appeared a second fluctuation in 60-180 cm soil layer from section 1 to section 3. The water accumulation above the aquiclude was an important supplementary to the aboveground vegetation. The soil water content in the dunes from section 1 to section 3 decreased obviously.

Correlations between numberic dynamics and reproductive characteristics of Ceratoides arborescens population in North China.

2010, 29(06):  1081-1086. 

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In this paper, the size class structure and the static life table and survival curve of Ceratoides arborescens population in North China were figured out, based on the basal diameter size and on the surviving number in each size-class and the number of filial generations. A time sequence prediction chart was established to predict the numeric dynamics of the population, and the population’s reproductive strategy was analyzed. The relationships between the numerical dynamics and reproductive characteristics of the population were also discussed. The age structure of the population showed that both young and old individuals were few, while middle-aged individuals were relatively rich. The analysis of the life tables and survival curves indicated that the survival curve of the population belonged to Deevey Ⅲ. Time sequence prediction suggested the number of old individuals would be increased at the beginning, and decreased over time. All these life-history traits suggested that the C. arborescens population in North China had some characteristics with both r-and k-strategies. Reproductive fitness played a critical role in the species’ development. The species’ reproductive strategies were related to the numerical dynamics of C. arborescens population characterized by age structure, life table, survival curve, and time sequence prediction figure. The dynamics of the population coincided with its reproductive biological characteristics, such as low efficiency of pollination system, malnutrition during embryonic development, and low conversion rate from seeds to seedlings, and the population recruitment depended severely on adult plants. Hostile environments in the habitat and human disturbance were also the main factors restricting the population development.

Population sex ratio and spatial distribution of dioecious tree species Pistacia chinensis.

2010, 29(06):  1087-1093. 

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An investigation was made on the population sex ratio and spatial distribution of dioecious tree species Pistacia chinensis within a 100 m × 140 m plot. In the plot, there were 2116 P. chinensis individuals with diameter at breast height (dbh) ≥4 cm, among which, 526 were females, 1200 were males, and 390 were undetermined. The sex ratio (males/females) was 2.28, indicating a significant male-biased sex ratio (P<0.001). The average dbh of the females and males was 7.34 cm and 7.81 cm, respectively, and the difference was significant (P<0.05). The saplings, females, and males all showed a significant clumped distribution. The saplings showed significant attraction to the females and males at small scales, while the females showed significant repulsion against the males at 0-50 m scales, i.e., the females and males exhibited spatial segregation. A significant repulsion also exhibited between different size and different sex individuals.

Responses of natural vegetation in Huangnan Prefecture of Qinghai to climate change: A study based on NPP.

2010, 29(06):  1094-1102. 

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Based on the 1981-2000 GLOPEM NPP dataset and the corresponding monthly meteorological data, this paper analyzed the variation trends of vegetation productivity and climate in four counties in Huangnan Tibetan Autonomous Prefecture of Qinghai, calculated the correlation coefficients of NPP and climatic factors, and approached the main climatic factors affecting vegetation variation. In the four counties, the average NPP increased significantly in the 1980s, and decreased with fluctuation in the 1990s. Overall, the NPP had a slight decrease in Jianzha and Tongren counties, but an increase in Zeku and Henan counties. The weather became wetter and warmer in Jianzha and Tongren counties in the 1980s and in Zeku and Henan counties in the 1990s, while drier and warmer in Jianzha and Tongren counties in the 1990s and in Zeku and Henan counties in the 1980s. Precipitation was the most important climatic factor affecting the NPP in Jianzha County, while air temperature had much stronger effects on the NPP in Henan County. Due to the different thermal-moisture conditions, the correlation between NPP and air temperature from north to south was stronger, while that between NPP and precipitation was weaker. Rainfall use efficiency increased significantly from 1981 to 2000 in Henan County, but increased slightly in the other three counties. The rainfall in April and May had an important restraining effect on NPP. Therefore, increasing water supply in spring was an effective way for increasing NPP. If the future climate change was similar to that in the 1990s, the decrease of rainfall would have negative effects on the vegetation growth in Jianzha and Tongren counties, and positive effects in southern Huangnan. In the process of vegetation restoration, the northern and southern parts of the Prefecture should pay more attention to the moisture addition and thermal preservation.

Effects of drought stress on dry matter partitioning of young Robinia pseudoacacia at its different growth stages.

2010, 29(06):  1103-1108. 

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A pot experiment was conducted to study the effects of drought stress on the dry matter partitioning of young Robinia pseudoacacia at its early, vigorous, and late growth stages under five soil moisture regimes (40%, 52.2%, 70%, 87.8%, and 100% of field water-holding capacity). At any given growth stage, soil moisture regime had no significant effects on the dry matter partitioning ratio of branch and stem. Short-term (15 d), medium- and light drought stress (70% and 87.8% of field water-holding capacity) had less effects on the dry matter partitioning ratio of leaf and shoot, while long-term (45-60 d) severe drought stress (40% of field water-holding capacity) decreased this partitioning ratio significantly, and increased the course root dry matter partitioning ratio and root/shoot ratio. As affected by the inherited growth characteristics of R. pseudoacacia itself and the variation of weather conditions among seasons, drought stress had different extents of effects on the dry matter partitioning of young R. pseudoacacia at its different growth stages, with the most significant effect occurred at early growth stage and the least at late growth stage.

Effects of low temperature stress on germination of tomato seeds.

2010, 29(06):  1109-1113. 

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Three levels of low temperature stress (7 ℃/12 ℃, 5 ℃/10 ℃, and 3 ℃/8 ℃ in 24 hours) were installed in a climatic chamber to study their effects on the germination of tomato seeds. Low temperature stress did give impact on the germination. Compared with the control (18 ℃/25 ℃), the stronger the stress, the greater the impact was. When the daily minimum temperature was 5.0 ℃ or the daily average temperature was less than 10.0 ℃ (corresponding to treatment 7 ℃/12 ℃), the impact was more severe; and when the low temperature stress was encountered earlier, the impact was greater. When the low temperature stress was encountered within three days after sowing, the germination potential, germinating index, and germination rate of tomato seeds all had a sharp decrease. However, when the low temperature stress was encountered six days after sowing, the three indices were less affected. Low temperature induced the decrease of tomato seed α-amylase activity and the increase of relative ion leakage, and thus, decreased the degradation of seed starch and enhanced the permeability of seed cell membrane, which could be the main reasons for the impact of low temperature stress on tomato seed germination.

Threshold values of cobalt toxicity to vegetables.

2010, 29(06):  1114-1120. 

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By the methods of water culture and soil culture, this paper studied the threshold values of cobalt (Co) toxicity to vegetables. Water culture was performed to select the most Co-sensitive vegetables from the 18 vegetable species commonly cultivated in Fujian Province, and soil culture was conducted to determine thethreshold values of soil Co toxicity to the selected vegetable species. Under water culture, low concentration (0.01 and 0.1 mg·L^-1) Co stimulated vegetable growth, while high concentration Co had toxic effects. Based on the apparent symptoms and the EC₂₀ values (effective concentration causing a 20% decrease of shootbiomass), Chinese cabbage (Brassica pekinensis) and cucumber (Cucumis sativus) were the most sensitive vegetables. In the followed soil culture with cucumber, no obvious stimulating effects of Co were observed. With the increasing concentration of added Co, the shoot biomass of cucumber decreased significantly. Based on the EC₁₀ (effective concentration causing a 10% decrease of shoot biomass) and the regression between soil DTPA-Co and total Co in the field, the threshold values of soil Co toxicity were estimated to be 2.7 mg·kg^-1 (DTPA-Co) and 98 mg·kg^-1(total Co).

Release characteristics of heavy metals in Pb/Zn tailings under acid leaching and the effects of leachate on plant seedlings growth.

2010, 29(06):  1121-1126. 

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A leaching experiment was conducted to study the release characteristics of heavy metals in the Pb/Zn tailings from Hezhang County of Guizhou Province, and the effects of the leachate on the growth of plant seedlings. With the increasing time of leaching, the contents of Cu, Zn, Pb, and Cd in the leachate had a decreasing trend, with their concentrations being 0.038-2.509, 0.0001-0.850, 0.040-0.605, and 0.004-0.021 mg·L^-1, respectively. Cd and Pb were the main components in the leachate. At early stage (days 1-5), the leachate had significant inhibitory effects on the growth of seedling’s roots and buds; but at late stage (days 20-25), the inhibitory effects decreased. Among the test plants, cabbage had the strongest resistance capability, followed by rape, and ryegrass.

Relationships of medium and micro elements contents between soil and flue-cured tobacco.

2010, 29(06):  1127-1134. 

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Through the analysis of the medium and micro elements contents in 30 samples of soil and flue-cured tobacco (Nicotiana tabacum L.) cultivar Honghuadajinyuan collected from Huili tobacco-growing areas of Sichuan Province, this paper studied the quantitative relationships of the elements contents between soil and flue-cured tobacco. In most soils of Huili tobacco-growing areas, the medium and micro elements contents were in suitable range; but in parts of the soils, the contents of water-soluble boron and available zinc were lower. The tobacco leaves had low contents of copper and magnesium. Multiple linear regression analysis showed there were significant relationships of the medium and micro elements contents between soil and tobacco leaves. The Mn and Zn contents in tobacco leaves were significantly affected by the contents of five medium and micro elements in soil, but the Ca content in tobacco leaves was only affected by the DTPA-Mn and exchangeable Ca contents in soil. Partial correlation and path analysis suggested that the micro elements contents in tobacco leaves were positively correlated with the corresponding micro elements contents in soil, and the direct effect coefficient was the maximum. There existed synergistic and antagonistic effects among the medium and micro elements in soil. The contents of all the medium and micro elements in tobacco leaves were most affected by the available Mn content in soil, but the Zn content in tobacco leaves was most affected by the other medium and micro elements in soil.

Effects of fertilization system on the fertility and microbial activity of aquic brown soil: A long-term field experiment.

2010, 29(06):  1135-1142. 

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Soil samples were collected from a long term experimental field to study the effects of different fertilization system on the fertility and microbial activity of aquic brown soil. Long-term fertilization, both inorganic and organic, decreased soil pH significantly. Chemical fertilization did not increase the contents of soil total carbon and nitrogen, while organic fertilization increased soil organic matter content significantly. Long term non-fertilization with chemical P and K induced the deficit of soil P and K. Organic fertilization, including manure (M), N+M, and NPK+M, increased soil microbial biomass (MB) significantly, compared with non-fertilization (CK). However, the difference in MB among treatments M, N+M, and NPK+M was not significant. No significant difference in MB was also observed between treatments NPK and CK. Soil microbial respiration was increased significantly in treatments M, N+M, NPK, and NPK+M, but had less change in treatment N. Comparing with CK, all fertilization treatments increased soil ammonification significantly, especially in treatment NPK+M. All fertilization treatments except treatment N increased soil nitrification significantly. Correlation analysis showed that soil microbial biomass C and N, microbial respiration, ammonification, and nitrification were significantly correlated with the contents of soil total carbon and nitrogen (P<0.01), suggesting that they could better reflect the changes of soil fertility, while soil microbial activity was discrepantly related to the other physical and chemical factors, suggesting that they had different responses to the changes of soil physical and chemical factors.

Effects of wheat root activity and fertilization mode on the microbial amount and enzyme activities in black soil.

2010, 29(06):  1143-1148. 

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A greenhouse pot experiment was conducted to study the effects of wheat root activity and fertilization mode on the microbial amount and urease and phosphatase activities in black soil. Under the conditions without wheat planting, the amounts of soil fungi  increased by 47.0%  in treatment NPK, and the activities of soil urease and phosphatase under fertilization increased by 17.2%-32.7%, and 21.2%-25.9%, respectively. With wheat planting, the amount of soil microbes and the activities of soil urease and phosphatase in treatment CK increased by 39.0%, 302%, and 38.5%, respectively, due to the root activity of wheat. The coupling of fertilization and wheat root activity increased soil microbial amount and soil urease and phosphatase activities significantly, with the increment being 3.3%-31.4%, 59.0%-168%, and 15.2%-26.7%, respectively. Soil phosphatase activity and the amounts of soil bacteria and fungi had significant positive correlations with the above- and belowground biomass of wheat.

Effects of different sand control engineering measures on soil fertility in Moyu County of Xinjiang.

2010, 29(06):  1149-1154. 

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A comparative study was made on the soil fertility in Moyu County of Xinjiang under effects of four sand control engineering measures. Differences were observed in the soil pH and nutrient contents under different sand control engineering measures. The soil pH value followed the order of natural sparse vegetation fencing area > grass grid and artificial forest > artificial forest > area collocated with multi-plants, and was significantly higher under natural sparse vegetation fencing area (P<0.05). The soil nutrient contents were affected by the duration of plant establishment. In the artificial forest having been established for three years, the contents of soil organic matter, total nitrogen, available nitrogen, total phosphorus, available phosphorus, and available potassium were higher than those in the newly established (half year) grass grid and artificial forest area. In the area collocated with multi-plants, the contents of soil organic matter, total nitrogen, available nitrogen, total phosphorus, and total potassium were higher, but the soil available phosphorus and potassium contents were relatively lower than those in other test engineering areas. Therefore, P and K fertilizers should be applied in the area collocated with multi-plants.

Mercury concentration in fish body in Hongjiadu Reservoir of Guizhou Province.

2010, 29(06):  1155-1160. 

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Aimed to approach the possible ecological risk of fish mercury from Hongjiadu Reservoir, a newly built reservoir located in Wujiang River Basin of Guizhou Province, a total of 124 fishes belonging to 8 species were collected, with their total mercury (THg) and total methylmercury (TMeHg) concentrations measured. The THg was measured with cold vapor atomic fluorescence spectrometry (CVAFS), and the TMeHg was analyzed by digesting the samples with 20% KOH, GC separation, and CVAFS detection. The results showed that carnivorous species had higher THg and TMeHg concentrations than omnivorous species. The average concentrations of THg and TMeHg in the fishes were 0.063±0.046 mg·kg^-1 and 0.028±0.019 mg·kg^-1, respectively. There were no significant linear relationships between the THg and MeHg concentrations and fish body length or weight. The Hg concentrations in fish body were related to the feeding habits and habitat preference of the fishes. The Hg concentrations in Hongjiadu Reservoir were lower than those in the newly built reservoirs in North America and Europe. Our results suggested that the TMeHg and THg concentrations in the fishes in Hongjiadu Reservoir did not have a dramatic increase, but with the evolvement of the newly built reservoir, the MeHg concentrations in the fishes could be increased gradually due to the increase of organic matter concentration in the reservoir.

Feeding rhythms of Macropodus opercularis larvae under different light condition.

2010, 29(06):  1161-1166. 

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This paper studied the feeding rhythms of 5-,8-,and 12-day old paradise fish (Macropodus opercularis) larvae under natural illumination, successive illumination, and successive dark-Under natural illumination, all the test larvae performed a typical daytime feeding rhythm, and fed actively during 12:00-16:00.However, under successive illumination and successive dark, the larvae did not show any identifiable feeding rhythm-Under successive illumination, the larvae fed actively all the day, and their feeding amount during 20:00-next 4:00 was significantly greater than that of the larvae under natural illumination-Conversely, the larvae under successive dark had a lower feeding intensity, particularly during 8:00-16:00, compared with the larvae under natural illumination. In conclusion, M. opercularis larvae performed a typical daytime feeding rhythm, and light condition greatly affected their feeding activity during their early life stages.

Population structure and reproductive biology of Todarodes pacificus in Southern Yellow Sea.

2010, 29(06):  1167-1174. 

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Based on the data of stow net survey in Southern Yellow Sea (SYS) from November 2008 to September 2009, this paper studied the population structure and reproductive biology of   Todarodes pacificus in the area, through the evaluation of the seasonal patterns in size structure, sex ratio (r_sex), mantle length (L_M) at first maturity, and relationships between L_M and body weight. The individuals of T. pacificus were distributed in SYS all year round. In autumn and winter, T. pacificus population was mainly consisted of mature individuals, while in spring and summer, the population was mainly consisted of immature individuals. The number of females was significantly higher than that of males, with the total r_sex being 0.60. When the L_M ranged from 190-280 mm, the relationship between r_sex and L_M could be expressed as r_sex=3×10^-5L_M^1.8017. The maturity stage tended to be increased with L_M. The monthly variation of the mean value of gonado-somatic index (GSI) for T. pacificus males and females was evident. The GSI approached the peak in autumn and winter, suggesting that the spawning of T. pacificus was mainly in autumn and winter. Both the GSI and the maturity stages (except Ⅴstage) were positively related to L_M. The L_M at first maturity for females and males was 201.9 mm and 174.3 mm, respectively. The relationship between L_M and body weight differed from maturity stages. At the late development stage of T. pacificus, the increase in body weight was mainly due to gonad maturation rather than somatic growth.

Distribution of introduced red swamp crayfish (Procambarus clarkii) in permanent lentic water bodies on Zhoushan Archipelago of China and related affecting factors.

2010, 29(06):  1175-1180. 

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In order to understand the habitat selection and spatial distribution of red swamp crayfish (Procambarus clarkia) and its influence on native amphibian diversity, an investigation was made in 86 reservoirs and ponds on eight islands (Daishan, Liuheng, Xiushan, Fodu, Taohua, Xiazhi, Cezi, and Putuo Mountain) of Zhoushan Archipelago in May–August 2008 by the methods of transect line, visual encounter survey, and net catching. Based on the investigation, the distribution and density of the crayfish in the water bodies were studied, with the related affecting factors analyzed. The results showed that 83.7% (72/86) of the water bodies had the distribution of P. clarkia, and 53.5% of them had the co-occurrence of P. clarkia and American bullfrog Rana catesbeiana. The density of P. clarkia in its invaded water bodies differed  the islands. The minimum adequate model based on information criterion (AIC_c) displayed that the occurrence of P. clarkia was positively correlated  maximum water depth and R. catesbeiana density. It was suggested that the occurrence of the crayfish might have little direct effects on the native frog species richness in permanent lentic water bodies. As an important ingredient of bullfrog diet, the crayfish’s distribution could potentially promote the density of bullfrog co-occurred with the crayfish.

Genetic structure of wild Sargassum thunbergii populations along Dalian coast: An ISSR analysis.

2010, 29(06):  1181-1186. 

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In order to understand the genetic structure of wild Sargassum thunbergii populations along Dalian coast, an inter-simple sequence repeat (ISSR) analysis was made on the genetic diversity and genetic relationships of six geographic populations of S. thunbergii, including five populations DC, DT, JJ, SC and YC from Dalian coast and one population PL from Penglai. 160 ISSR loci tested, 145 (90.62%) were polymorphic with 14 different ISSR primers. The values of percentage of polymorphic bands (PPB), Shannon’s index (I), and Nei’s gene diversity (H) were 41.25%-64.38%, 0.2321-0.3464, and 0.1585-0.2333, respectively. Dalian populations had higher genetic diversity than Penglai population. The analysis of molecular variance (AMOVA) showed that in the total genetic variation, the variation within populations was 35.66%, and the variation among populations was 64.34%. The value of gene flow (N_m) among the six populations was 0.7837, suggesting a limited gene flow among the populations. The UPGMA tree based on Nei’s genetic identity showed that population DC was clustered with populations DT and JJ, then with populations SC and YC, and finally with PL. All the results suggested that different reproductive mode and different growth environment might have critical roles in the genetic differentiation of S. thunbergii populations.

Macrofaunal community at three habitats in the 14th Yong intertidal zone of Nansha, Guangzhou.

2010, 29(06):  1187-1192. 

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In order to understand the community structure of macrofauna in the 14th Yong intertidal zone of Nansha, Guangzhou, an investigation was made at three different habitats, i.e., bare tidal flat, Sonneratia habitat, and Cyperus malaccensis habitat from 2007 to 2008, with the seasonal variations of the macrofaunal community structure at the habitats compared and analyzed. The species number, average biomass, and species richness index (d) in four seasons were all the highest at C. malaccensis habitat, the second at bare tidal flat, and the lowest at Sonneratia habitat; while the average density, species diversity index (H′), and evenness index (J) were the highest at bare tidal flat, the second at C. malaccensis habitat, and the lowest at Sonneratia habitat. ANOVA analysis showed that there was a significant difference in the species number and density among the habitats, but no significant difference in the biomass. MDS and cluster analysis showed that in spring and summer, the macrofaunal community at the three habitats was similar, but in winter, only the macrofaunal community at bare tidal flat and C. malaccensis habitat was similar. The causes for the differences in species composition and quantity among the three habitats were discussed.

Nest site selection and reproductive habit of Ficedula zanthopygia in man-made nest box.

2010, 29(06):  1193-1197. 

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From February 2005 to July 2006, 226 man-made nest boxes were put onto a secondary deciduous forest to study the nest site selection and reproductive habit of Ficedula zanthopygia. Twenty five of the 226 boxes were utilized by F.zanthopygia, and 96% of them were of mini-type, suggesting that F. zanthopygia had selectivity on nest box size. The clutch size of F. zanthopygia was 6.00±0.17, egg’s long size was (17.45±0.07) mm and egg’s short size was (13.20±0.06) mm, average egg weight was (1.54±0.02) g, average incubation period and nestling period were  12-14 d, hatch rate was 88.76%, and flying rate was 96.22%. The main factors affecting the nest site selection were nest sit(31.46%), concealment below nest (24.67%), illumination (15.70%), and food (11.32%). Nest site was the uppermost factor in nest site selection. Concealment  was the second, which could reduce prey probability. Illumination could elevate the temperature within nest, playing an important role in hatching. Food was an important factor in satisfying the nutrition of F.zanthopygia in its breeding season. The materials of the nest were miscellaneous and closely related to the local environment, reflecting the stronger adaptability of F. zanthopygia to habitat.

Optimization of cross-combination in lamb production in natural plateau pasture ecosystem of China.

2010, 29(06):  1198-1202. 

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To select an optimal cross-combination in lamb production in natural plateau pasture ecosystem of China, and search for a more beneficial way for using Gansu Alpine Merino germplasm resource in the plateau habitats, a cross experiment was conducted, taking the introduced breeds (Texel, Australian Merino, White Suffolk, and Bond) as the rams, and Gansu Alpine Merino as the ewes. By the method of artificial insemination, mating was conducted in November, while lambing was in next April. The birth weight, weaning weight, 6-month-old weight, and 12-month-old weight of the crossbred lambs were measured, and the slaughter trials were conducted when the lambs were weaned, 6-month old, and 12-month old. The results showed that the average birth weight, weaning weight, and 6-month-old weight of Texel F1 were 5.53, 27.86 and 31.24 kg, respectively, being significantly higher than those of the other cross combinations (P<0.05). The growth of the crossbred lambs became slow from 6-month-old to 12-month-old. When the lambs were weaned and 6-month old, the carcass weight of Texel F1 was 14.25 kg and 14.55 kg, respectively, significantly higher than those of the other cross combinations (P<0.01). The dressing percentage and carcass meat percentage of the weaned and 6-month-old Texel F1 were higher than those of the other crossbred lambs (except the dressing percentage of Australian Merino crossbred lambs when weaned), but the ratio of meat to bone was lower than that of the other crossbred lambs. From the analysis of the growth and slaughter performance, the Gansu Alpine Merino-Texel crossing model was the ideal combination for the lamb production in the natural plateau pasture ecosystem.

Breeding ecology and nestling growth pattern of Egretta alba alba in Ebinur of Xinjiang.

2010, 29(06):  1203-1207. 

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From March to October 2009, an investigation was made on the characteristics of nests and eggs as well as the nestling growth pattern of Egretta alba alba in Ebinur (Aibi Lake) of Xinjiang. The thickness of E. alba alba nest fundus was greater than nest depth (t=6.06, P<0.01), and the outside diameter of the nests was greater than inside diameter (t=21.53, P<0.01), which guaranteed the nest stability and reduced the probability of nestling falling off the nests. The clutch size was 3-5 eggs (3.86±0.69), with the egg weight and cubage being 44.00-60.00 (53.94±3.96) g and 47.18-62.00 (55.19±4.09) cm³, respectively. Two parent birds were responsible for the incubation (26-28 d) and parents care (55-60 d). Gompertz equation was used to fit the 26-day-old growth pattern of 13 nestlings in 4 nests, which showed that the nestling growth could be divided into three phases. First, the organs of nestling came into being and the growth rate was going to increase. Second, as a phase of matter accumulation, the growth rate had a great increase and gradually transited to mid-rate. Third, matter consumption gradually exceeded matter accumulation, and young birds began to fly.

Identification and degrading characteristics of PAHs-degrading bacterial strain X20.

2010, 29(06):  1208-1212. 

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A bacterial strain X20 was isolated from a mixed microflora which can effectively degrade polycyclic aromatic hydrocarbons (PAHs). This strain was identified as Pseudomonas sp., based on its morphological observation and 16S rRNA sequence analysis. The study on the degradation of phenanthrene and pyrene by X20, and the effects of medium pH, PAHs initial concentration, and glucose content on the degradation potential of X20 showed that weak alkaline condition favored the degradation of phenanthrene and pyrene by X20, and the optimal pH was 8.0. The effects of glucose concentrations on the degradation changed as parabolic, and 0.2% was the optimal glucose concentration. When the PAHs initial concentrations were 10, 20, and 40 mg·L^-1, the degradation rates of phenanthrene and pyrene were 56.3%, 39.25% and 29.75%, and 41.8%, 29.55% and 23.50%, respectively, i.e., the inhibiting intensity of pyrene to X20 was higher than that of phenanthrene. This study provided a basis for constructing an efficient PAHs-degrading strain and improving the bioremediation effect of PAHs-  in situ contaminated soil.

Spatiotemporal variation of extreme precipitation frequency in summer over South China in 1961-2008.

2010, 29(06):  1213-1220. 

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Based on the 1961-2008 daily precipitation data from 110 meteorological stations in South China, the spatiotemporal characteristics of extremely heavy precipitation frequency in summer over South China were studied by the ways of REOF, trend coefficient, linear trend, M-K test and variance analysis, and the extremely heavy precipitation thresholds were determined, according to the 95th percentiles of non-parametric distribution for different stations. The extremely precipitation events frequency anomaly in summer over South China was negative from late 1970s to early 1990s, and was positive after mid-1990s. Six sub-regions were divided, according to the spatial characteristics of extremely heavy precipitation frequency over South China. A significant upward trend of the extremely heavy precipitation events in summer appeared over northeast Guangxi, southeast Guangxi and west Guangdong, and south Hainan. Over east Guangdong, west Guangxi, and Leizhou area, the trend of extremely heavy precipitation events in summer was on the low side in the 1980s, and on the higher side between the 1990s and the beginning of 21st century. The periodic variation of the extreme precipitation frequency in summer in the six sub-regions was significant, with 23 and 21 years in long period, 17, 16, and 12 years in mid-term period, and 5 and 4 years in short cycle. Five of the six sub-regions appeared a significant increase in extreme precipitation frequency in 1990s.

Ecosystem engineering of cushion plants in alpine plant community: A review.

2010, 29(06):  1221-1227. 

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How the plants adapt to the serious environments such as low temperature, strong solar radiation, strong wind, and poor soil fertility in alpine areas is a popular question which has becn paid much attention in alpine ecology. Cushion plants area group of representative plants in alpine areas, whose compact and huge surface structure can change their surrounding micro-environments, e.g., can regulate maximum and minimum temperature, improve soil humidity and nutrient availability, and reduce wind erosion. The changed micro-environments by cushion plants can benefit other alpine plants, and improve the species diversity of plant community. Therefore, cushion plants are called as the ecosystem engineers in alpine ecosystem, and the ecosystem engineering of cushion plants is an important way for plants to adapt alpine environments. The environmental change, such as the changes of altitude and water resources, can affect the ecosystem engineering of cushion plants, and a major research challenge is to understand the regulation mechanism and magnitude of cushion plants, which is of significance in predicting the future dynamics of alpine plant community under climate change.

Responses of river organisms to watershed landscape pattern change: A review.

2010, 29(06):  1229-1234. 

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Watershed landscape pattern change can induce the alteration of the community composition, structure, and function of river organisms. To study the responses of river organisms to this change is the focus of river ecology. This paper analyzed the ways that watershed landscape pattern change affects river organisms, summarized the research indicators, methods, and scales, and the main conclusions in previous studies. Some suggestions for future research about the choices of research indicators and scales and the arrangement of sampling points were proposed.

Factors affecting the competitive colonization of beneficial bacteria in plant rhizosphere: A review

2010, 29(06):  1235-1239. 

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Rhizosphere competitive colonization is of significance in the applications of soil beneficial microbes as biofertilizer, biopesticide, phytostimulator and bioremediator. The competitive colonization of bacteria in plant rhizosphere is a complicated process, and the factors affecting the colonization are complex and numerous. This paper reviewed the biotic factors involving in the competitive colonization, including the traits controlled by bacterial genes, e.g., flagella/motility, chemotaxis, polysaccharide, site-specific recombinase/phase variation and NADH dehydrogenase, and the root exudates and plant species, as well as the abiotic factors affecting the colonization, such as soil type, soil property, and soil temperature. The future research directions on the competitive colonization of beneficial bacteria in plant rhizosphere were also discussed.

Impacts of atrazine chronic poisoning on hemolymph DNA of Eriocheir sinensis.

2010, 29(06):  1240-1244. 

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Atrazine is one of the most widely used herbicides in China. In this paper, Eriocheir sinensis was treated with 0.01, 0.1, and 1 mg·L^-1 of atrazine for 90 days, and single-cell gel electrophoresis was used to study the impacts of atrazine chronic poisoning on the hemolymph DNA of E. sinensis. The fluorescence microscope observation and the CASP analysis of the images showed that all the three concentrations of atrazine could induced the DNA damage of E. sinensis hemolymph. With the increase of atrazine concentration, the TM value and the percentage of TailDNA increased gradually, and the impacts were most significant when the concentration of atrazine was 1 mg·L^-1, suggesting that definite concentration atrazine could induce the broken of DNA chain, and destroy the DNA structure of E. sinensis hemolymph.

Monitoring of chlorophylla concentration in Dianchi Lake based on spectral characteristics and merged MODIS images by HSV transformation.

2010, 29(06):  1245-1249. 

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By using measured hyperspectral data, the spectral characteristics of the water body in Dianchi Lake were analyzed, and a hyperspectral inversion model for the chlorophyll-a concentration in the Lake was established by statistical methods. Based on the spectral characteristics and the merged MODIS images by HSV transformation, the distribution of chlorophyll-a concentration in the Lake was monitored. It was shown that the spectral reflectance peaks of the water body were near 550 and 700 nm, and the positions and values of the peaks were very sensitive to the changes of chlorophyll-a concentration. The higher the chlorophyll-a concentration, the closer the values of the two peaks, and the reflective peak near 550 nm had an excursion to short wave while that near 700 nm had an excursion to long wave. Therefore, the difference between the values of spectral peaks near 550 and 700 nm could be used as the parameter in establishing a model for inversing chlorophyll-a concentration, and the estimation could have a higher precision. Our results indicated that the MODIS false color images achieved by HSV transformation and merging technologies could visually inverse the spatial distribution of chlorophyll-a concentration in Dianchi Lake.

Ecological security assessment of Naiman County based on desertification degree and NDVI index.

2010, 29(06):  1250-1256. 

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Ecological security assessment from the viewpoint of land use/cover is the core and base of the study on sustainable land use. With the emphasis on the impacts of desertification process, a township scale comprehensive assessment was made on the ecological security pattern in Naiman County of Inner Mongolia, according to the present status of land use/cover and corresponding NDVI value, and by the combination of analytic hierarchy process (AHP) and integrative assessment index. The ecological security situation of the County had undergone extreme un-safety–more safety–critical state between more safety and safety in 1985, 1995, and 2005. The areas of safe and more safe increased gradually from zero, and their sum accounted for two thirds of the total. Although a few townships such as Bagaborihe had a rebound trend of deteriorated – improved – deteriorated, the overall situation of ecological security in the County was improved.

Dynamic simulation of land use pattern in Guangzhou based on CLUE-S model.

2010, 29(06):  1257-1262. 

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Twenty-one driving factors, including altitude, slope, distance to river, and distance to railway, etc., were selected to simulate the dynamic land use pattern of Guangzhou based on CLUE-S model. The simulated results had a high reliability, with the Kappa coefficient being 0.8014 to the actual situation. The prediction of the land use pattern in Guangzhou in 2010 showed that the distribution of cropland and water body would be mainly affected by topography, and forestland would be more affected by altitude. In 2005-2010, the land use patch number and the landscape fragmentation in Guangzhou would be increased, the complexity of patch shape tended to be simplified, and the diversity index would have a slight increase.