Table of Content

10 June 2013, Volume 32 Issue 6

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Responses of soil carbon mineralization potential to the succession of artificially sand-binding vegetation in Shapotou region of Tengger desert, North China.

ZHOU Yu-yan1,2, JIA Xiao-hong2,3**, ZHANG Xuan-ming1, MA Jin-qin1, CHEN Feng-ming1, GAO Yan-hong2

2013, 32(6):  1371-1377. 

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Soil respiration is one of the important biochemical processes related to the mineralization and decomposition of soil organic matter (SOM) and the release of inorganic nutrients. In this study, an incubation experiment was conducted to study the mineralization potential of SOM in the re-vegetation area with an age sequence in Shapotou region of Ningxia. After 103 days of incubation, the released soil CO₂-C was in the age sequence of 55 years > 47 years > 30 years > 24 years > 21 years > mobile dune. Meanwhile, the released CO₂-C decreased along the soil profile 0-5 cm, 5-10 cm, and 10-20 cm in re-vegetation area, but increased along the soil profile in moving sand dune. There existed significant differences (P<0.05) in the soil carbon mineralization potential, total nitrogen, organic carbon, and electrical conductivity among the age sequence. All the variables increased with age sequence but decreased with soil depth. Correlation analysis showed that the soil carbon mineralization potential was significantly correlated to the soil organic carbon, total nitrogen, C/N ratio, soil temperature, soil water, pH, and electrical conductivity (P<0.01), and all the soil variables were significantly correlated each other (P<0.01). The soil nutrient contents increased obviously with age sequence, and the improvement of soil nutrient status was in accordance with the enhancement of soil carbon mineralization potential. It was suggested that the establishment of artificial vegetation promoted the activities of soil microbes, which was implied by the soil respiration, whereas the vegetation recovery and litter accumulation mitigated soil wind erosion, increased SOM input, and contributed to C sequestration.

Spatial heterogeneity of soil respiration in Populus balsamifera plantation at different developmental stages.

YAN Mei-fang1,2**, ZHANG Xin-shi2, ZHOU Guang-sheng2

2013, 32(6):  1378-1384. 

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The spatial heterogeneity of soil respiration plays an important role in accurately evaluating soil carbon balance. Based on the observations of the soil respiration, soil environmental factors, and fine root biomass in poplar (Populus balsamifera) plantations at three developmental stages in Yili of Xinjiang, Northwest China, this paper analyzed the spatial variation of soil respiration and related affecting factors. In the whole growth period of P. balsamifera, the coefficient of variation (CV) of soil respiration ranged from 5.7% to 42.6%. The average soil respiration rate for 2-, 7-, and 12-year old P. balsamifera stands was 5.74, 5.10 and 4.71 μmol·m^-2·s^-1, and the CV was 28.8%, 22.4% and 19.6%, respectively, with a significant difference in the spatial variation of soil respiration among the three age classes. Multiple regression analysis suggested that the temperature at soil depth 5 cm and the nitrogen content and fine root biomass in upper soil layer were the main factors determining the spatial heterogeneity of soil respiration, responsible for 86% of the variation in soil respiration. In addition, the factors such as soil temperature and fine root biomass changed with the distance from measurement position to tree stem, which could also lead to the spatial variation of soil respiration. It was suggested that the spatial variation of soil respiration at different developmental stages of P. balsamifera should be taken into consideration when evaluating the soil carbon emission in poplar plantations.

Seasonal dynamics of soil water-soluble organic carbon in secondary forests and Chinese fir plantations in hilly region of northwest Zhejiang Province, East China.

LIU Rong-jie, LI Zheng-cai**, WANG Bin, WU Ya-cong, CHENG Cai-fang, MA Shao-jie, GERI Le-tu

2013, 32(6):  1385-1390. 

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In order to understand the content and seasonal dynamics of forest soil water-soluble organic carbon (WSOC) in the hilly region of northwest Zhejiang Province, the secondary forests and Chinese fir plantations were chosen as the test objects to study the WSOC content in 0-10 cm and 10-20 cm soil layers in four seasons. No significant differences were observed in the WSOC content in 0-10 cm and 10-20 cm soil layers between the secondary forests and Chinese fir plantations. The seasonal dynamics of soil WSOC in the secondary forests and Chinese fir plantations had the same trend, and followed the order of winter > spring > autumn > summer. The WSOC content in 0-10 cm and 10-20 cm soil layers in the secondary forests and Chinese fir plantations had significant negative correlations with soil temperature and precipitation, less correlation with soil moisture content, and positive correlation with litter biomass (especially for the WSOC content in 0-10 cm soil layer).

Responses of soil nitrogen transformation process to freezing-thawing cycle in a riparian zone under three different vegetation types.

LI Sheng-nan1,2, FAN Zhi-ping3**, LI Fa-yun3, YAN Jia-liang2, GAO Hong-cui1,2

2013, 32(6):  1391-1398. 

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Riparian zone is a hot spot region of nitrogen (N) biogeochemical cycle in terrestrial-aquatic ecotone, while the freezing-thawing cycle resulted from the temperature change during spring snow-melt is one of the important factors affecting soil N transformation process and N loss. In this paper, a laboratory simulation experiment was conducted to study the responses of soil dissoluble N and net N mineralization rate to different freezing temperature and freezing-thawing frequency in a riparian zone under the vegetation types of Sorbaria sorbifolia, Larix gmelinii, and cropland. The results showed that freezing-hawing frequency had significant effects on the soil dissoluble N concentration, and there was a similar variation trend of the dissoluble N concentration under the three vegetation types, i.e., peaked after the first freezing-thawing cycle and became stable after the tenth freezing-thawing cycle. The soil inorganic N concentration under the three vegetation types increased significantly under freezing-thawing conditions (P<0.05). Freezing temperature had significant effects on the soil net N mineralization rate (P<0.05),  with the maximum after the first freezing-thawing cycle and decreased gradually with increasing freezing-thawing cycle. As affected by freezing-thawing cycle, the soils under the three vegetation types all had the risk of N loss. Due to the higher background value of soil inorganic N and the lack of plant N absorption in spring, cropland had a higher risk of soil N loss with snowmelt runoff, as compared to the other two ecosystems.

Effects of soil moisture condition and freeze-thaw cycle on soil respiration of  different land-use types in Horqin Sandy Land.

CHU Jian-min1, WANG Qiong2,3**, FAN Zhi-ping2,3, LI Fa-yun2, SUN Xue-kai3

2013, 32(6):  1399-1404. 

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In Horqin Sandy Land, a semiarid region of Northeast China, soil freeze-thaw caused by the temperature change in late autumn, winter, and early spring has significant effects on soil CO₂ emission, and thus, it is of significance to study the effects of the interaction between soil moisture content and freezethaw on soil respiration. Taking the silvopasture system, cropland, and grassland in Horqin Sandy Land as test objects, a simulation experiment was conducted to study the effects of soil moisture condition and freeze-thaw cycle on the soil respiration under different land use patterns. The results showed that soil moisture condition, freeze-thaw cycle, and land use pattern all had significant effects on soil respiration. Before freeze-thaw, the soil respiration rate was significantly higher in grassland than in silvopasture system and cropland. During freezethaw, soil respiration rate was higher in silvopasture system than in cropland. After freeze-thaw, soil respiration rate was significantly higher in grassland than in silvopasture system. When the soil moisture content was 80% of water-holding capacity (WHC), soil respiration rate was significantly higher than that when the soil moisture content was 60% of WHC. During the whole incubation period (20 days), the amount of soil CO₂ emission from silvopasture system, cropland, and grassland under 60% of WHC was 21.535, 19.908, and 25.037 g CO₂·m^-2, and that under 80% of WHC was 26.407, 29.447, and 36.246 g CO₂·m^-2, respectively.

Effects of hydromulching on soil water availability.

YIN Guang-hua1**, HAO Liang1,2, ZHAO Yong-hong3, GU Jian1, LIU Zuo-xin1

2013, 32(6):  1405-1411. 

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A field micro-plot experiment with peanut was conducted to study the soil water content, plant elongation rate, leaf area index, photosynthetic rate, water use efficiency, and economic yield under hydromulching. By using subordinate function, the soil water availability was analyzed. Hydromulching increased the soil water content by 103%-167%, and improved the soil water availability. The peanut water consumption differed significantly with soil layer, being the greatest for 20-40 cm soil layer. Under hydromulching, the photosynthetic rate increased by 1.9%-15.6%, leaf area index raised by 0.3%-26.4%, and plant morphology was improved. In considering all indices, high concentration of hydromulching type 3 had the most obvious effect.

Community diversity and its seasonal dynamics of soil fauna in Fukang oasis of Xinjiang, Northwest China.

ABLIZ Omar1**, NURMAMMAT Gulbostan2, TURSUN Abudurusul1, HAJIM Mukaram1, WU Song-lin1

2013, 32(6):  1412-1420. 

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In order to understand the community diversity and its dynamic changes of soil fauna in different habitats of Fukang oasis, a field investigation was conducted in April, July, September, and mid November, 2010. Seven different habitats including timber forest, shelter forest, nursery, cropland, saline-alkaline land, shrub land, and desert grassland were chosen, and hand-sorting and modified Tullgren and Baermann methods were adopted to isolate the soil fauna in 0-20 cm layer, with the community structure, distribution characteristics, and seasonal dynamics of soil fauna analyzed. A total of 11098 individuals were collected, belonging to 35 groups, among which, Nematoda, Rotifera, and Collembola were the dominant groups. There existed significant differences in the individual number, group number, and community diversity of soil fauna among different habitats and seasons (P<0.05). In the seven habitats, the Shannon diversity index was in the order of timber forest > shelter forest > shrub land > cropland > salinealkaline land > nursery > desert grassland. The spatiotemporal distribution analysis of soil fauna in different habitats indicated that there was an obvious surface gathering, and the distribution had significant differences among seasons and soil layers (P<0.05). The individual number was the largest in autumn, followed by in spring and winter, and the least in summer. The Jaccard similarity index of the soil faunal communities in different habitats was 0.25-0.50, belonging to medium dissimilarity. The results of the betweengroups clustering and sorting showed that the seven habitats could be divided into four types, i.e., artificial forest habitat, anthropogenic disturbance habitat, shrub habitat, and desert habitat. These findings suggested that there existed obvious habitat and seasonal differences in the community composition and diversity of soil fauna in different habitats of Fukang oasis.

Mammalian species diversity in Baishanzu National Nature Reserve, Zhejiang Province of East China based on G-F index.

CHEN Xiao-rong1, XU Da-ming1, BAO Yi-xin2**, ZHANG Shu-sheng2

2013, 32(6):  1421-1427. 

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By the methods of interview survey and field survey in combining with historical literatures, an investigation was conducted on the terrestrial mammal resources in the Baishanzu National Nature Reserve, Zhejiang Province of East China from August 2010 to June 2012. A total of 55 mammal species were recorded, belonging to 20 families and 8 orders. The oriental species were dominant, and there were 3 and 11 classes I and II nationally protected species, respectively. A comparison between the Baishanzu Reserve and the other 5 nature reserves also located in Zhejiang Province showed that there were no significant differences in the mammalian familyindex (Findex) and genusfamily index (G-F index) among these reserves. Especially, the Baishanzu and Fengyangshan reserves had highly similar mammalian F index and G-F index values, possibly due to the geographic proximity and habitat composition. No significant difference was observed in the species distribution density among the six reserves, but Niutoushan Nature Reserve, due to its smaller area, had a higher species distribution density.

Migration behavior of cotton bollworm in Xinjiang of Northwest China based on the ovarian development characteristics of adult females.

ZHANG Juan1,2, MA Ji-hong1, XU Yang-cheng1, WANG Xin3, WANG Pei-ling3, OMAR Guzalnur4, LU Zhao-zhi1**

2013, 32(6):  1428-1432. 

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Cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is a nocturnal pest capable of long-distance migration. To explore whether the H. armigera in Xinjiang has migratory activity, the ovarian development and mating frequency of the H. armigera were monitored in the Shihezi reclamation area of northern Xinjiang (Regiment 146 and Regiment 147), Wusu, Akesu region of southern Xinjiang (Akesu City, Awati County, and Regiment 12), and Maigaiti. The results showed that mating occurred when the moth ovaries developed to the first grade, and the mating frequency was significantly positively correlated with the development grade of moth ovaries. The individuals of the third generation H. armigera in Regiment 146, Regiment 147, Wusu, and Akesu and those of the third and forth generations H. armigera in Awati, whose ovarian development was at the third grade or above, occupied 65% or more, indicating that the cotton bollworm populations were immigrated from other places. In the peak mating period, the average mating rate and mating frequency of adult females were 81.63% and 1.96, respectively. At all of the monitoring sites, the mating rate and male/female ratio of the adult females were in correspondence with the physiological characteristics of immigrant populations, indicating that cotton bollworm immigration had occurred at all experimental sites in Xinjiang. These observations on the migration and mating of H. armigera in Xinjiang could provide basic information for the control of this pest in this region.

Reproductive allocation of Saussurea hieracioides (Asteraceae), a common species in eastern margin of Qinghai-Tibet Plateau.

Sonamtso1,2, WANG Yi-feng1**, LI Mei1, YUE Yong-cheng1, LI Mao-xian3

2013, 32(6):  1433-1438. 

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Saussurea hieracioides (Asteraceae) is a wide spread species in the eastern margin of Qinghai-Tibetan Plateau. This paper studied the reproductive allocation (RA) strategy of the 18 S. hieracioides populations in 6 altitudinal belts along the elevation from 3200 to 3850 m. The results showed that with increasing altitude, the plant individual size and vegetative input decreased, but the reproductive input increased. The number of disk florets and matured seeds per individual declined, while the weight of disk florets and 100-grain increased with increasing altitude, and there was a tradeoff between the number and weight of both disk florets and matured seeds at individual level. The RA was negatively correlated with the plant individual size among all the populations. It was suggested that in the resources-limited environment, S. hieracioides could increase its tubular floret weight and 100-grain weight at the expense of reducing the number of both tubular floret and seed as one of the strategies to guarantee the success of sexualreproduction.

Interspecific relationships of dominant species in tree layer of natural Pteroceltis tatarinowii community in Lishan, Shanxi Province of China.

LI Hao1, LI Yu2, ZHANG Zhi-feng1, DU Yong-hai1, FENG Fei1, LI Xiao-li1, BI Run-cheng1**

2013, 32(6):  1439-1444. 

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Based on the quadrat survey and the analysis of Pteroceltis tatarinowii community structure in Lishan, this paper measured the interspecific covariation coefficients of dominant species, and, in combining with canonical correspondence analysis and cluster analysis, approached the interspecific relationships between P. tatarinowii and other species. In the study area, the A class frequency (1%-20%) of P. tatarinowii community occupied the absolute superiority. P. tatarinowii occupied the dominant position in the community, but the dominance in succession layer and regeneration layer was inferior to that of other species. The results of Spearman rank correlation analysis and Pearson correlation analysis were basically consistent, i.e., the number of positive covariation couplets in tree layer was lower than that of negative covariation couplets, the negative covariation between the couplets P. tatarinowii and Diospyros lotus was the highest, and in all of the significant or positively significant covariation couplets that contained P. tatarinowii, the P. tatarinowii and another species were always in significant or very significant negative correlation. Slope, soil moisture content, and litter thickness had strong correlations with 3 ordination axes, the classification of 18 dominant tree species along the second axis was more consistent with the characteristics of the species, and soil moisture content was the dominant factor affecting the distribution of P. tatarinowii. Cluster analysis showed the dominant tree species in the tree layer of P. tatarinowii community could be divided into three categories.

Genetic diversity of endangered wild Cypripedium japonicum populations: An AFLP analysis.

QIAN Xin1, LI Quan-jian1,2, LIAN Jing-jing1, WANG Cai-xia1, TIAN Min1**

2013, 32(6):  1445-1450. 

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Cypripedium japonicum is a rare and endangered terrestrial orchid. To explore and formulate the pertinent conversation strategies of this species, this paper analyzed the genetic diversity and genetic structure of six natural C. japonicum populations in Zhejiang Province of East China by the method of AFLP. A total of 377 distinct bands were amplified by 7 pairs of selected primers. The percentage of polymorphic loci was 20.95%, Nei’s genetic diversity index was 0.0512, Shannon information index was 0.0417, genetic differentiation coefficient was 0.5178, and gene flow was 0.4655, indicating that there was a relatively low genetic diversity within the C. japonicum populations, and a certain degree of genetic divergence  existed among the populations. The analyses of UPGMA clustering and Mantel test showed that there was no significant correlation between the geographical distance and genetic distance (r=0.16, P=0.242). Some conservation strategies were proposed based on this study and the biological properties of C. japonicum.

Population structure  of endemic species Beilschmiedia tungfangensis  in Hainan of South China.

YANG Huai1, LI Yi-de1**, XU Han1, CHEN Ren-li1, LUO Tu-shou1, CHEN De-xiang1, MIAO Ning2, SHENG Da-yong3

2013, 32(6):  1451-1457. 

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To approach the characteristics of endemic species Beilschmiedia tungfangensis population structure in Hainan, a 20.4hm² experimental site was installed in Jianfengling forest region of Hainan, with the population diameter structure, static life table, survival curve, and spatial distribution pattern analyzed. The diameter class distribution of the B. tungfangensis population showed a reverse “J” type, suggesting that this population was of increasing type. The life expectancy was the highest at the third stage (DBH: 10-15 cm), and showed a decreasing trend to both the big and the small age classes. The survival curve was a concave one, similar to Deevey type III, whereas the mortality rate curve and hazard rate curve showed “V” type. The analyses with different methods all showed that the spatial distribution pattern of the B. tungfangensis population tended to be aggregated, and the aggregation intensity was strong. The patchiness index showed “sine or cosine” curve with diameter class.

The flora in Qinglong River Nature Reserve and its surrounding areas, Liaoning Province of Northeast China.

YU Meng-fan1, YU Qi-yin1, LIN Tian-miao2, XING Shao-hua1**, YIN Jun-wu3, ZHANG Chun-lei3, ZHANG Kejia3, ZHANG Liang3

2013, 32(6):  1458-1464. 

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Qinglong River Nature Reserve lies in western Liaoning Province, the crunodes of Liaoning, Hebei, and Inner Mongolia, and is the connection of Yanshan Mountain, Qilaotu Mountain, and Nuluerhu Mountain. For protecting the plant diversity in North and Northeast China, it is of significance to study the floral composition in Qinglong River Nature Reserve and its adjacent nature reserves. Based on the investigation data from 95 sampling plots in the Qinglong River Nature Reserve, this paper analyzed the floral composition and distribution type of vascular plants in the Reserve, and a comparison was made with the flora in adjacent nature reserves. In the Reserve, a total of 656 vascular plant species were recorded, belonging to 108 families and 362 genera, among which, 21 species were of fern plants, belonging to 14 families and 16 genera, 2 species were of gymnosperm, belonging to 2 families and 2 genera, and 633 species were of angiosperms, belonging to 92 families and 344 genera. The genera of seed plants in the Reserve could be divided into 15 distribution types. The floristic characteristics were ancient origin, abundant species, and obvious temperate feature. The comparison of the flora in Qinglong River Nature Reserve and in five adjacent reserves showed that the proportion of the floral composition in a reserve was greatly associated with its geographical location. Overall, the floral composition was affected by latitude (temperature), i.e., the higher the latitude, the higher the proportion of the temperate floristic composition, and also, affected by the distance to the ocean. The proportion of the floral composition in Qinglong River Nature Reserve had great relevance to the latitude.

Leaf and stem traits of current-year twigs vary with different functional types of woody plant. 

GUO Qing-xue, CHAI jie, QIAN Feng, ZHANG Teng-da, LIU Wen-dan, TAO Jian-ping**

2013, 32(6):  1465-1470. 

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The current-year twigs of 20 and 26 woody plants were collected from Jinfo Mountain and Jinyun Mountain in Chongqing City of Southwest China, respectively, to study their leaf and stem traits, aimed to explore the differences in the functional traits of current-year twigs between deciduous and evergreen species, and between trees and shrubs. The results showed that the leaf thickness was smaller for deciduous species and trees than for evergreen species and shrubs, while the leaf area and total leaf area showed an opposite trend. However, there was no significant difference in the leaf number among these different functional types of woody plants. The stem cross-sectional area, stem length, and stem dry mass were all significantly larger for deciduous species and trees than for evergreen species and shrubs, but no significant difference was observed in the stem density. Deciduous species and trees had higher leaf area ratio than evergreen species and shrubs, but less difference appeared in leaf intensity. At twig scale, evergreen species allocated more biomass to their leaves, as compared with deciduous species.

Effects of red and far-red light ratio on the flower bud differentiation of greenhouse cut chrysanthemum cultivar ‘Jingba’.

PENG Xiao-dan1, YANG Zai-qiang1,2**, LI Ling-li1, ZHANG Ji-bo1

2013, 32(6):  1471-1475. 

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An experiment with LED light source irradiation of 4 ratios (0.5, 2.5, 4.5, and 6.5) of red light (R: 660±10 nm) to far-red light (FR: 730±10 nm) was conducted to study the effects of red/far red light ratio (R/FR) on the flower bud differentiation, relative growth rate, and inflorescence diameter of Chrysanthemum morifolium cv. ‘Jingba’. In treatment R/FR=6.5, the duration needed by the ‘Jingba’ to complete its flower bud differentiation was the shortest, being shortened by 34 days as compared to treatment R/FR=0.5. The larger the R/FR, the higher the relative growth rate for the flower bud differentiation would be. When the flower bud differentiation completed, the relative growth rate in treatment R/FR=6.5 was as twice as that in treatment R/FR=0.5. Similar to the flower bud differentiation, the dimension of inflorescence diameter was in the order of treatment R/FR 6.5 > R/FR 4.5 > R/FR 2.5 > R/FR 0.5. This study indicated that the R/FR ratio of 6.5 could promote the chrysanthemum flower bud differentiation and the inflorescence diameter growth significantly.

Effects of low potassium stress on the photosynthesis and photosynthate partitioning of cotton. 

XIA Ying1,2, JIANG Cun-cang3, WANG Xiao1, CHEN Fang1,4**

2013, 32(6):  1476-1482. 

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Taking two cotton cultivars of high efficient genotype (HG) and low efficient genotype (LG) as test objects, a field experiment was conducted to study their photosynthesis and photosynthate accumulation and partitioning under low potassium (K) stress. Low K stress decreased the leaf net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), and plant biomass, promoted the partitioning of photosynthates to vegetative organs but decreased the partitioning ratio to reproductive organs, and thus, decreased the harvest index. There existed differences in the photosynthetic parameters between the two cotton cultivars. Whether K was applied or not, HG cultivar had higher P_n, T_r, G_s, and C_i, as compared with LG cultivar. There also existed differences in the biomass partitioning between the two cotton cultivars. The HG cultivar partitioned less biomass to vegetative organs but more to reproductive organs, and maintained a higher harvest index, while LG cultivar was in adverse, regardless of the K condition. The biomass of the two cotton cultivars had no significant difference at seedling stage and squaring stage, but the biomass of HG cultivar was higher than that of LG cultivar at bolling stage and boll opening stage. Moreover, the K use index of HG cultivar was higher than that of LG cultivar at bolling stage and boll opening stage. This study indicated that K application could improve the photosynthetic function of cotton leaf and the partitioning efficiency of photosynthates.

Effects of soaking with Tibetan sheep rumen fluid on the seed germination of 11 plant species on alpine meadow of Qinghai-Tibetan Plateau, China.

DUAN Chun-hua, YU Xiao-jun**, XU Chang-lin, ZHANG De-gang

2013, 32(6):  1483-1489. 

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To clarify the effects of soaking with Tibetan sheep rumen fluid on the seed germination characteristics of the plants on the alpine meadow of Qinghai-Tibetan Plateau, the seeds of 11 common plant species in the northeastern part of Qinghai-Tibetan Plateau were collected and soaked with the fresh rumen fluid from Tibetan sheep, and a germination test was conducted after the seeds were soaked in the rumen fluid for 12, 24, 36, 48, 60, and 72 h, respectively. The seeds were incubated at 25 ℃ for 8 h and at 15 ℃ for 16 h under natural light conditions. The results showed that the seed germination was affected by soaking time, seed coat treatment, and plant species. As compared with the control, the germination percentages of the scarified seeds of Oxytropis ochrocephala, coatcut seeds of Carex enervis, and coatcut or intact seeds of Anemone rivularis were increased significantly after soaking for 12 h, 12 h, and 12-36 h, respectively. The germination percentages of both the scarified and the intact seeds of Elymus nutans, Pedicularis kansuensis, Achnatherum inebrians, Poa crymophila, and Medicago ruthenia var. inschanica were declined significantly by any exposure to rumen fluid. The seed germination percentages of Kobresia humilis, Rumex acetosa, and Polygonum sibiricum were not affected by short duration treatment, but inhibited with increasing processing time. The germination of scarified seeds was more sensitive to the soaking, as compared to the intact seeds, and the latter was relatively stable. The germination index (GI) of the coatcut seeds of A. rivularis and O. ochrocephala and of the scarified seeds of C. enervis was increased significantly in short duration treatments of 12-24 h, 12 h, and 12 h, respectively, but decreased gradually with the extension of processing time. It was suggested that the seed germination of the plant species on alpine meadow performed differently (enhanced, inhibited, or not affected) under the treatments of soaking with Tibetan sheep rumen fluid, which might affect the seedling recruitment, interspecific competition, and plant community structure on alpine meadow.

Bacillus atrophaeus  strain’s colonization in wheat plant and its inhibition efficiency to Fusarium head blight.

XIN Hai-feng1, MENG Yan-yan1, LI Jian-hong1**, MA Hong-xiang2, ZHANG Xu2

2013, 32(6):  1490-1496. 

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An antagonism strain XM5 which can strongly inhibit Fusarium graminearum was isolated from wheat leaves at jointing stage. The strain was identified as Bacillus atrophaeus by 16S-23S internal transcribed spacer (ITS) nucleotide sequences. To track the XM5 colonized in wheat plant, a dualantibioticmarker resistant to rifampicin and streptomycin was induced by gradually increasing the concentration of antibiotics in the medium for XM5. Meanwhile, the ITS sequence of XM5 was used as a DNA marker. A pair of specific primers L6SF and L6SR was adopted for PCR test. With the double labels of the dual antibiotic resistance and the specific PCR test, the amount of XM5 colonized in wheat plant was measured. The results showed that XM5 could colonize in wheat plant for a long time, but the amount of XM5 in seedlings decreased with time. To measure the biocontrol efficiency of XM5 to Fusarium head blight (FHB), the XM5 cell suspension and cultured broth (with cells) were sprayed on the heading wheat, respectively, and the amount of endophytic XM5 in wheat ear and the resistance efficiency against FHB were surveyed. In the two treatments, the amount of XM5 on the surface of wheat ear decreased with time, only less than 5% XM5 being survived 10 days later, but in the cell suspension treatment, the amount of colonized XM5 in wheat ear increased unceasingly from 5.2×10³ to 4.8×10⁴ cfu·head^-1, and the biological control efficiency to FHB reached 68.3% after 7 days.

Effects of deep plowing and mulching in summer fallow period on dryland wheat yield and water- and nitrogen use efficiency.

BAI Dong, GAO Zhi-qiang**, SUN Min, ZHAO Wei-feng, DENG Yan, LI Qing

2013, 32(6):  1497-1503. 

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A field experiment was conducted to study the effects of deep plowing at different time and of mulching with different materials in summer fallow period on the nitrogen absorption, translocation, and allocation, and on the water- and nitrogen use efficiency of dryland wheat. As compared with the deep plowing and mulching after 15 days of previous wheat harvest, the deep plowing and mulching after 45 days of previous wheat harvest improved the plant nitrogen content at elongation, booting, and mature stages, increased the plant nitrogen accumulation and nitrogen uptake at each growth stage, increased the nitrogen transfer amount and transfer rate in pre-anthesis, increased the contribution rate of nitrogen transfer to grain nitrogen in pre-anthesis under liquid film mulching and no-mulching, and increased the accumulation amount and rate of grain nitrogen while decreased the accumulation rate of nitrogen in leaf, steam, and glume + spike stem, with the better effects under seepage plastic mulching. Deep plowing and mulching after 45 days of previous wheat harvest, as compared with that after 15 days of previous wheat harvest, increased the yield and water use efficiency and the nitrogen uptake efficiency and production efficiency. In sum, deep plowing and mulching after rain in fallow period increased the plant nitrogen uptake and accumulation, and was conducive to the transfer of pre-anthesis stored nitrogen to grain, increased the accumulation of grain nitrogen, decreased the nitrogen accumulation of vegetative organ, and ultimately, improved the yield, water use efficiency, nitrogen uptake efficiency, and nitrogen production efficiency. Among the mulching measures, seepage plastic mulching had better effects.

Spatiotemporal variation patterns of climatic factors and climatic potential productivity of spring maize in eastern Gansu of Northwest China.

YIN Hai-xia, ZHANG Bo**, ZHANG Jian-xiang, SUN Li-wei, HE Xu-qiang

2013, 32(6):  1504-1510. 

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Based on the 1961-2010 weather data from 15 meteorological stations and the field observation data in spring maize growth period, and by using statistics method and geographical information system (GIS) techniques, this paper studied the variation characteristics of climatic factors and the spatiotemporal distribution characteristics of photosynthetic potential productivity, light-temperature potential productivity, and climatic potential productivity of spring maize during its growth period in East Gansu from 1961 to 2010. In the recent 50 years in eastern Gansu, the mean air temperature in spring maize growth period presented a fluctuated increase, with a mean annual increase of 0.36 ℃, while the total solar radiation declined obviously, and the precipitation showed a fluctuated descent. The photosynthetic potential productivity presented a decrease, lighttemperature potential productivity was in adverse, and climatic potential productivity showed a slight increase. The photosynthetic potential productivity increased gradually from south to north, light-temperature potential productivity was higher in the north, south, and east parts but lower in the central part, and climatic potential productivity decreased from southeast to northwest. The decrease of solar radiation led to the decline of the light-temperature potential productivity, but the greatly increased temperature compensated the negative effect of solar radiation. Due to the decrease of precipitation and its uneven seasonal distribution, the climatic potential productivity was impacted to some extent. Our results provided references in revealing the spatiotemporal variation patterns of climatic factors and climatic potential productivity of spring maize in East Gansu.

Spatiotemporal variation of reference crop evapotranspiration and related climatic affecting factors in eastern Gansu of Northwest China in 1961-2010.

WANG Yuan-yuan, ZHANG Bo**, YIN Hai-xia

2013, 32(6):  1511-1517. 

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Based on the 1961-2010 daily weather data from 15 meteorological stations, and by using climate tendency rate, partial correlation analysis, and linear regression analysis, in combining with the inverse distance weighting (IDW) method of GIS spatial analysis techniques, this paper quantitatively analyzed the reference crop evapotranspiration (ET₀) in eastern Gansu at different temporal and spatial scales, and studied the spatiotemporal variation patterns of the ET₀ and related climatic affecting factors. In the recent 50 years in eastern Gansu, the mean annual ET₀ presented a weak downward trend. The summer ET₀ decreased significantly, being the main reason for the decrease of the mean annual ET₀, the spring ET₀ increased remarkably, while the ET₀ in winter and autumn had no obvious change trend. The mean monthly ET₀ showed a unanimous single peak. Spatially, the mean annual ET₀ was larger in northern and central areas, but smaller in western areas. The spring ET₀ showed an increasing trend in most areas, the summer ET₀ showed a decreasing trend in the whole eastern Gansu, while the ET₀ in winter and autumn had no obvious change trend. The ET₀ was negatively correlated with relative humidity and precipitation, but significantly positively correlated with temperature, sunshine hours, and wind speed. Sunshine hours, wind speed, and relative humidity were the main climatic factors affecting the ET₀ in eastern Gansu.

Risk analysis and regionalization of agrometeorological drought hazard in Jilin Province of Northeast China.

LIU Yu-ying**, SHI Da-ming, HU Yi-xin, ZHANG Chen-chen, ZHANG Ting

2013, 32(6):  1518-1524. 

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Based on the 1961-2010 observation data from 50 meteorological stations and the 1981-2010 drought disasters’ and agricultural economic data, and by using the theories of natural disasters systematic analysis as well as the methods of farmland water balance and disaster risk index, this paper analyzed the dangers of drought hazardcausing factors to agricultural production, the sensitivity of drought hazard-formative environments, the vulnerability of drought hazard-affected bodies, and the capability of drought prevention and disaster mitigation in Jilin Province of Northeast China. The comprehensive risk indices of different units were obtained by using the weighting comprehensive evaluation method, and the drought hazard affecting the agricultural production of the Province was spatially regionalized based on GIS technology. In the Province, the high risk region of drought disaster-causing factors was distributed in the Baicheng and most areas of Songyuan in western Jilin, the high sensitivity region of drought hazardformative environments was distributed in the areas of Baicheng, Songyuan, north of Siping, and south of Tonghua, the high vulnerability region of drought hazard-affected bodies was distributed in the economically more developed areas, including the most parts of Songyuan and Changchun, and Siping, and the region with high capacity of drought prevention and disaster mitigation was mainly distributed in Songyuan, Changchun, Siping, Jilin City, and Tonghua urban area and its surrounding areas. In considering the integrated risk level of all the drought hazard-causing factors, the drought risk affecting the agricultural production of Jilin Province could be classified into 5 levels, i.e., high, sub-high, medium, sub-low, and low, among which, high and sub-high risks  mainly occurred in the regions of Baicheng, Songyuan, Changchun, and Siping.

 

Climate change and its impacts on extreme climate events in Liaoning Province of Northeast China.

GONG Qiang1**, WANG Hong-yu2, ZHANG Yun-fu1, WANG Ying1, CUI Yan1, ZHOU Xiao-yu1, ZHANG Hai-na1

2013, 32(6):  1525-1531. 

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Based on the 1961-2010 climate data from 55 meteorological stations, and by using linear regression and the comparison of different standard climate periods, this paper analyzed the changes in climate factors and their impacts on the extreme climate events in Liaoning Province. In recent 50 years, the mean annual air temperature in the Province had a significant increase, with an increment of 0.30 ℃ per decade. The increasing rate of the mean daily minimum air temperature (0.48 ℃ per decade) was over twice of that of the mean daily maximum air temperature (0.20 ℃ per decade). As compared with those in the first standard climate period (1961-1990), the mean annual air temperature in the nearest 30-year standard climate period (1981-2010) increased by 0.5℃, the annual sunshine duration reduced by nearly 100 h, but the precipitation had no obvious change trend. Under the background of climate warming, the summer chilling damage and the extreme cold events  still occurred. Extreme precipitation had no significant change trend, but the interannual fluctuation of the maximum daily precipitation and of the process maximum precipitation was greater than the linear trend. The extreme precipitation showed signs of expansion from eastern Liaoning to the whole province. No significant change was observed on the snow cover depth, but the top two ranks of the maximum snow depth all occurred after 2000. The frozen soil depth had a significantly  decreased trend. Under the background of climate warming, the precaution against extreme climate events should not be ignored.

Distribution and accumulation characteristics of Hg in rice (Oryza sativa L.) under different concentrations of soil Hg. 

ZHOU Jun1, LIU Hong-yan1**, WU Long-hua2, LUO yong-ming2, DU Bu-yun3, YU Ping-ping1

2013, 32(6):  1532-1538. 

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A pot experiment was conducted to study the distribution of Hg forms in soil and the distribution and accumulation characteristics of Hg in rice (Oryza sativa L.) plant during its various growth stages under different concentrations of soil Hg. The main Hg forms in the soil were in the order of organic bound > residual >> oxidizable >> dissoluble and exchangeable ≈ specifically adsorbed. During rice growth season, the Hg in soil presented a transformation trend from residual to organic bound, and the organic bound Hg occupied 61.7% of the total Hg, being the most important existing form of Hg in soil. The Hg concentration in different organs of rice was in the order of root > leaf > stem > ear > grain. The Hg concentrations in rice root, stem, and grain were significantly positively correlated with the concentrations of all the Hg forms in soil. However, at the late growth stages of rice, the leaf Hg concentration had less correlation with soil Hg concentration, indicating that the exchange between leaf Hg and atmospheric Hg played a major role, and changed the Hg accumulated status. With the increase of soil Hg concentration and the extension of rice growth phase, the Hg binding capacity of rice root increased gradually, and the cumulative amount and the proportion of root Hg increased, while the accumulation amount of stem and leaf Hg was relatively stable.

Effects of different ecotype Glomus mosseae isolates on arsenic uptake by Pteris vittata.

WU Fu-yong1,2**, LIU Xue-ping1, BI Yin-li3, GUO Yi-fei1, MAO Yan-li1, WONG Ming-hong2

2013, 32(6):  1539-1544. 

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Pteris vittata, as an arsenic (As) hyperaccumulator, can be colonized by arbuscular mycorrhizal (AM) fungi either in controlled conditions or at field sites. However, the physiological mechanisms of AM fungi affecting the As accumulation and translocation in P. vittata are not fully elucidated. In this study, two isolates of Glomus mosseae were obtained from the rhizosphere of P. vittata growing on an Ascontaminated site in Jinchuantang of Hunan Province (G. mosseae BGC GD01A, metalcontaminated isolate) and from the clean soil in Yunnan Province (G. mosseae BGC YN05, uncontaminated isolate). The isolates were inoculated to the rhizosphere of Ascontaminated and uncontaminated P. vittata, respectively. After 8 weeks of inoculation, a 24h water culture experiment was conducted with the P. vittata seedlings colonized by AM fungi and exposed to 100 μmol·L^-1 of As (Na₂HAsO₄·7H₂O). Both the two isolates could colonize on P. vittata roots at moderate level (25.2%-31.3%). The inoculation either with metalcontaminated isolate or with uncontaminated isolate promoted the P uptake by P. vittata roots obviously. During the 24 h culture, the inoculation with uncontaminated isolate promoted the As uptake by P. vittata roots significantly, while the inoculation with metalcontaminated isolate only had a slight effect in promoting the As uptake, showing that there was an intraspecific difference of AM fungi in their effects on the As uptake by P. vittata.

Effects of coupled stress of copper and cadmium on the photosynthesis of seagrass Thalassia hemprichii.

FENG Shao-hui1,2,3, HUANG Xiao-ping1**, ZHANG Jing-ping1,3

2013, 32(6):  1545-1550. 

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By using chlorophyll fluorescence technique, this paper investigated the photosynthetic parameters of seagrass Thalassia hemprichii under the coupled stress of Cu and Cd. Under the stress of Cd plus higher concentration (1.0 mg·L^-1) Cu, the maximum quantum yields (F_v/F_m), photochemical quenching (q_P), and nonphotochemical quenching (NPQ) declined remarkably, and the seagrass died after 5 days exposure, indicating that the photosynthesis of T. hemprichii suffered from severe damage, and the photoprotective mechanisms lost. On the contrary, after 5 days coupled stress of Cd and lower concentration (0.1 mg·L^-1) Cu, the q_P and NPQ had somewhat increase, and the F_v/F_m recovered to the preexposure level during recovery period, suggesting that the photoprotective mechanisms of T. hemprichii could be provoked and enhanced under the coupled stress of Cd and lower concentration Cu. In addition, under the coupled stress of Cu and Cd, the pigment content of the seagrass increased with increasing concentration Cd, suggesting that simply using pigment content to assess the stressed level of seagrass was inaccurate, and other indices and further analysis were needed.

Toxic effects of herbicide paraquat on different species of Lemnaceae.

WANG Lin-lin1, ZHANG Guang-fu1**, HE Xie1, GE Feng2, ZHOU Jun-ying2

2013, 32(6):  1551-1556. 

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To explore the toxic effects of herbicides on different species of Lemnaceae, the median inhibition concentration (IC₅₀) and chronic value (ChV) of paraquat to Spirodela polyrhiza, Landoltia punctata, and Lemna minor were measured, with the acute and chronic toxic effects of paraquat on these three Lemnaceae species compared. After treated for 96 hours, the IC₅₀ value of paraquat to S. polyrhiza, L. punctata, and L. minor was 17.37, 6.16, and 4.75 μg·L^-1, respectively, and there existed significant differences among the acute toxicity (P<0.05). The chlorophyll content of the three species all decreased significantly with increasing paraquat concentration, and after treated for four days, a significant negative correlation was observed between the chlorophyll content and paraquat concentration (P<0.05). The ChV of paraquat to S. polyrhiza was 3.050 μg·L^-1, and while that to both L. punctata and L. minor was 0.964 μg·L^-1. However, in light of frond features, the ChV of paraquat to S. polyrhiza was 10.780 μg·L^-1, while that to L. minor was only 3.410 μg·L^-1, implying that the chronic toxic effect of paraquat to L. minor, whether from the viewpoint of frond features or chlorophyll content, was greater than that to S. polyrhiza. Therefore, under the treatment of paraquat, the three species of Lemnaceae demonstrated obvious plant taxonomy effect, dose effect, and time lag effect.

Effects of plant species richness on nitrate removal from wastewater: A hydroponic microcosm experiment.

CHEN Zheng-xin, WU Jian-zhi, GU Bao-jing, SUN Hong-ying, LIU Yu, WANG Hai, CHANG Jie, GE Ying**

2013, 32(6):  1557-1562. 

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Previous studies have shown that the plant diversity in constructed wetlands with sand substrate can improve the removal efficiency of wastewater contaminants. However, the effects of plant diversity in the aquatic system without substrate on nitrogen removal are unknown. In this paper, 45 hydroponic microcosms (53 cm × 37.5 cm × 18.5 cm) with 1, 2, 3, and 4 plant species were installed, and periodically applied with nitrate as the sole nitrogen source at a loading rate of 548.5 g N·m^-2·a^-1 to simulate wastewater. The results showed that species richness had significant effects on the effluent nitrogen removal. The total inorganic nitrogen concentration in the effluent of four species systems (54.3 mg·L^-1) was obviously lower than that of monoculture systems (129.0 mg·L^-1). The community biomass increased significantly with the increase of species number. The total biomass in four species systems (1621.6 g·m^-2) was higher than that in monoculture systems (1032.7 g·m^-2). The average nitrogen removal rate in the hydroponic microcosms was 466.8 g N·m^-2·a^-1, not lower than that in the previously reported fullscale constructed wetlands. Meanwhile, the nitrogen removal rate in four species systems was 13% higher than that in monoculture systems, indicating that the improvement of nitrogen removal efficiency in constructed wetlands could be achieved by increasing plant diversity.

Nutrient enrichment effect of Antarctic krill (Euphausia superba) powder on the fatty acid and amino acid compositions in Artemia-nauplii.

LU Jian-xue, LIN Ting-ting, HUANG Yan-qing, GAO Lu-jiao**, GONG Yang-yang, XIA Lian-jun, HUANG Hong-liang

2013, 32(6):  1563-1570. 

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This paper studied the nutrient enrichment effect of Antarctic krill (Euphausia superba) powder at four concentrations (0, 75, 150, and 225 mg·L^-1) on the fatty acid and amino acid compositions in brine shrimp (Artemia sp.) nauplii. The nauplii samples were taken every 6 h until 18 h. As compared with the control, the nauplii fed with Antarctic krill powder had significantly higher contents of docosahexaenoic acid, total ω3 polyunsaturated fatty acids, and total polyunsaturated fatty acids at each sampling time. Except that the eicosapentaenoic acid content in the treatments of 75 and 225 mg·L^-1 of Antarctic krill powder at the sampling time of 6 h had no significant difference with the control, the eicosapentaenoic acid content in the treatments of feeding with Antarctic krill powder at other sampling time was significantly higher than that of the control. The arachidonic acid in the treatments of 75 mg·L^-1 of Antarctic krill powder at the sampling time of 18 h and of 150 mg·L^-1 of Antarctic krill powder at the time of 12 and 18 h was also increased significantly. For amino acids, the contents of essential amino acids (EAA) or total amino acids (TAA) in the treatment of 150 mg·L^-1 of Antarctic krill powder were significantly higher than those of the control. Moreover, the EAA/TAA ratio in the treatment of 150 mg·L^-1 of Antarctic krill powder was significantly higher than that in the other three treatments. A significantly higher EAA/TAA ratio was also found in the treatment of 225 mg·L^-1 of Antarctic krill powder at the sampling time 12 h, as compared to the control. In sum, Antarctic krill powder had better effect in enriching the fatty acid and amino acid compositions in Artemia sp. nauplii, and the recommended concentration and treatment time for the enrichment were 150 mg·L^-1 and 12  or 18 h, respectively.

Effects of CaCl² on the Cd accumulation and stress of Spartina alterniflora.

HE Zhen-zhen1, CHAI Min-wei1, WEI Yuan1, LIU Li-min2, SHI Fu-chen1**

2013, 32(6):  1571-1577. 

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A vermiculite pot culture experiment was conducted to study the effects of low, medium, and high concentrations of CaCl₂ on the Cd accumulation and stress of Spartina alterniflora. At 200 μg·g^-1 of CdCl₂, the S. alterniflora plant height, tiller number, catalase activity, and shoot and root dry weights decreased somewhat, while the plant proline content increased significantly. With the supplement of increasing concentration of CaCl₂, the plant height, tiller number, catalase activity, and shoot and root dry weights decreased after an initial increase, indicating that definite concentration of CaCl₂ increased the Cd tolerance of S. alterniflora. As compared with CdCl₂ stress alone, the supplement of CaCl₂ decreased the plant proline content, suggesting the mitigation effect of CaCl₂ on the toxic effect of Cd on S. alterniflora. The Cd was mainly accumulated in the underground part of S. alterniflora.  With the increasing concentration of supplemented CaCl₂, the Cd concentration in the above and underground parts of S. alterniflora and the Cd transfer coefficient increased significantly, suggesting that CaCl₂ had definite activation effect on Cd, and helped to increase the capability of S. alterniflora in absorbing Cd and transporting the Cd to the plant aboveground part.

Industrialization process and ecological risk pattern in a rich energy region of northern Shaanxi, Northwest China.

WEN Xiao-jin1, YANG Hai-juan1**, LIU Yan-xu2, JIANG Chong3

2013, 32(6):  1578-1586. 

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Ground surface habitat destruction by energy exploitation, goaf subsidence caused by underground mining, and pollutant discharge from energy and chemical enterprises are the main factors leading to the environment deterioration in energy source regions. However, in a larger scale, the mechanisms driving the interactions between the industrialization in mining area and the regional ecological pattern is rather complicated, and it is difficult to determine the spatiotemporal rhythm and scale synchronization. In this study, a rich energy region in Shaanxi under the background of ecological restoration was chosen as a case. Based on the DMSP/OLS and MODIS NDVI data, the spatiotemporal variation characteristics of the industrialization process and vegetation ecological risk pattern were analyzed, and the spatial variations of land use types, the decreasing trends of annual precipitation and runoff, and the frequency of earthquake occurrence were analyzed at different scales, aimed to explore the impacts of industrialization process on ecological risk. The results showed that whether the hypothesis that industrialization would directly increase the regional ecological pressure in mining area could be established was dependent on empirical perspective and scaling. Under the background of vegetation restoration, the role of industrialization on vegetation pattern could not appear at a larger scale analysis. Overall, the ecological environment in the energy rich region of northern Shaanxi was in a pattern of generally improved and partially deteriorated. The interaction mechanism of vegetation pattern and industrialization process was unidirectional and of asynchronization in time and space, and the small and large scale observational results were inconsistent. The industrialization process in smaller areas still strongly affected the local ecological security. It was suggested that the policy orientation of regional ecological environment construction should be considered to balance the whole and its partials.

Responses of alpine grassland ecosystem on Tibetan Plateau to climate change: A mini review. 

WANG Chang-shun1,2, MENG Fan-dong1,2, LI Xin-e1, JIANG Li-li1, BAI Ling3, WANG Shi-ping1**

2013, 32(6):  1587-1595. 

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Alpine grassland ecosystems on Tibetan Plateau are highly sensitive to climate change. How these ecosystems response to climate change is a great concern. Based on the past five years researches, this paper briefly reviewed the responses of these ecosystems to climate change from the aspects of phenology, plant productivity, and carbon cycle, and the adaptive management to climate change. There are inconsistent conclusions so far. Most of the researches indicated that warming advanced the plant phenology and increased the primary productivity of alpine meadow, while opposite trends were observed for alpine steppe, suggesting that different plant communities in different regions could have different modes in response to the temperature change in different seasons. Similarly, there are controversial conclusions about the responses of plant species diversity and carbon sink/source to climate change because of the differences in spatial and temporal scales and research methods. Therefore, further researches are needed to integrate the spatial and temporal researches and to strengthen the studies of ecological processes and mechanisms.

Effects of forest fire on forest soils. 

XU Peng-bo1,2, QU Ming3, XUE Li1**

2013, 32(6):  1596-1606. 

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Forest fire is the free spread fire in woodland ecosystems. There are two types of forest fire, i.e., prescribed (controlled) fire and wildfire. The effects and the duration of fires depend upon the fire severity. Fires can affect soil structure through the combustion of soil organic matter and the alteration of soil clay minerals, leading to the increase of soil bulk density and the decrease of soil water holding capacity. Over a long period of time,  fires can reduce soil organic matter. After burning, the increase of soil temperature and pH can promote soil respiration, while the decrease of microbial biomass, death of roots, and decrease of decomposable materials can reduce soil respiration. Forest fires consume the forest litter layer by oxidation, volatilization, leaching, and convection of ash particles, which results in soil nutrient loss. Forest fires also have important effects on soil organisms. The high temperature of burning can directly kill soil microbes, and indirectly affect soil microbe survival and microbial community structure through changing the soil physical and chemical properties and the woodland microenvironment. The effects of fires on soil animals are less obvious than on microbes because the soil animals have higher mobility to escape fires. Low and moderate severity fires indirectly affect soil enzymes by altering soil environment, whereas high severity fires could directly denature soil enzymes because of the extreme high temperature. In the future, the studies on forest fires should be focused on the longterm study with interdisciplinary cooperation, especially for the interrelationships among soil animals, microbes, and ecosystem responses after burning, and the effects of prescribed and wildfires on soil organic carbon, stability of soil nutrient pool, soil water repellency, soil and water loss, and biodiversity.

Effects of arbuscular mycorrhizal fungi on plant drought tolerance: Research progress.

ZHANG Zhong-feng1,2, ZHANG Jin-chi1**, HUANG Yu-qing2, YANG Hui3, LUO Ya-jin2, LUO Ai-ying2

2013, 32(6):  1607-1612. 

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Arbuscular mycorrhizal fungi (AMF) can form mutually beneficial symbiont with plant roots, having positive effects on the plant growth and stress resistance, and playing a key role in improving plant water metabolism and drought tolerance. This paper summarized the research progress in the relationships between AMF and plant water metabolism, and discussed the effects of AMF on the plant water metabolism from the aspects of photosynthesis, transpiration and stomatal conductance, water use efficiency, water conductance, osmotic regulation substances, endogenous hormone levels, and antioxidant system. The mechanisms of AMF in improving the plant drought tolerance were introduced, including the extension of root absorption surface through mycelium network, the enhancement of plant water retention and antioxidation capacity, the stabilization and improvement of soil aggregation, and the promotion of host plant nutrient acquisition. Some issues and suggestions needed to be regarded in the related researches were proposed.

Applications of stable carbon isotope to the studies of carbon biogeochemical cycle in coastal wetland: A review.

CHEN Wan, XI Min, LI Yue**, KONG Fan-long, KONG Fan-ting

2013, 32(6):  1613-1619. 

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Carbon is an important element of life, and its biogeochemical cycle is one of the core contents in the study of coastal wetland. Stable isotope technique is more and more applied in this domain, having improved the research level and promoted the research progress. This paper summarized the advances in the stable isotope research on the carbon biogeochemical cycle in coastal wetland from the aspects of organic matter production, soil organic matter traceability, transferring process of food chain, greenhouse gases emission, and dissolved organic carbon output. The mechanisms and extraneous sources of organic matter production are investigated by the measurement of plant and soil δ¹³C values, the carbon flow in the wetland ecosystem is analyzed through the comparison of the δ¹³C values of various species, and the environmental factors affecting the carbon output of wetland ecosystem are revealed via the measurement of the δ¹³C values of emitted greenhouse gases and dissolved organic carbon. By the end of this paper, the existing problems and the future directions of related studies were discussed and prospected.

Modeling spatial patterns of forest fire in Heilongjiang Province using Generalized Linear Model and Maximum Entropy Model.

LIU Sheng-ji1,2, YANG Jian1**

2013, 32(6):  1620-1628. 

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Forest fire distribution models are the powerful tools to map the spatial patterns of forest fire in larger scale, and to quantify the relative importance of the major factors controlling forest fire occurrence. Based on the forest fire ignition data in Heilongjiang Province in 1996-2006, and by using Generalized Linear Model (GLM) and Maximum Entropy Models (Maxent), this paper analyzed the factors controlling the forest fire occurrence in the Province, including topography, human activity, and land vegetation type, and compared the modeling accuracy, variable importance, and ignition probability map. Both the GLM and the Maxent had intermediate predictive performance, with the Maxent performed slightly better. Overall, the variables related to human activities were the most important predictors of forest fire ignition locations, followed by topographical variables. Despite the two models had similar modeling accuracy, the ignition probability map generated by Maxent was noticeably different from that generated by GLM. It was suggested that to make a comparison of or to selectively assemble different type models to produce integrated prediction results would be more desirable to more accurately identify the hotspots of forest fire occurrence, and thus, to provide more reasonable and higher efficient comments for forest fire prevention.

Vegetation degradation and its modeling in rock desertification area of northern Guangdong, South China. 

LU Guan-yao1,2**, LI Sen2, WEI Xing-hu1, LIANG Zhao-xiong1, XIONG Yan1, HUANG Jin-guo1

2013, 32(6):  1629-1635. 

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In this paper, site investigation and fixed position observation  were conducted in the sampling plots with four different stages of rock desertification in rocky desertification area of northern Guangdong to study  the  vegetation degradation and its modeling in rocky desertification area. With the development of rocky desertification, the plant community structure in the study area became increasingly simpler, with the dominant plant species evolved from Pistacia chinensis + Boehmeria nivea + Vitex negundo + Pueraria phaseoloides to Pistacia chinensis + Artemisia carvifolia + Dendranthema indicum to Miscanthus floridulus + Arundinella anomala + Eleusine indica to Fissidens zippelianus. The community’s layer was from 4 layers to 3 layers to 2 layers to 1 layer, and the proportion of species reduction was from 0 to 14% to 46% to 86%.  The soil organic matter, total N, available N, available P, and available K contents were all decreased significantly with the development of rocky desertification. Vegetation degradation could be described by the competition models of different species to certain kinds of resources, and thus, a model was established for the vegetation degradation in rocky desertification area of northern Guangdong.

Application of principal component analysis in comprehensive assessment of soil quality under Panax notoginseng continuous planting.

ZHANG Zi-long1**, WANG Wen-quan1, MIU Zuo-qing2, LI Shi-dong2, YANG Jian-zhong3

2013, 32(6):  1636-1644. 

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Continuous planting obstacle is a serious problem in Panax notoginseng culture, but few studies have been performed to evaluate the soil quality under P. notoginseng continuous planting. In this paper, a comprehensive assessment was made on the soil quality under P. notoginseng continuous planting by using principal component analysis and cluster analysis. Our results showed that the key factors determining the soil quality were the diversity of microorganisms, abundance and relative ratio of soil fungi, and soil phosphorus and potassium contents. The comprehensive assessment index (f _value) could better reflect the soil quality and the growth status of P. notoginseng plant, being an appropriate index for the assessment of soil quality under P. notoginseng continuous planting.

Chilling damage index of flue-cured tobacco: Its establishment and variation characteristics.

LI Meng, ZHU Yong**, ZHANG Ming-da, HUANG Wei

2013, 32(6):  1645-1652. 

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Based on the 1961-2009 daily mean and minimum temperature data from 62 meteorological stations in the fluecured tobacco planting areas of Yunnan Province, Southwest China, and by using lowtemperature indicators and weighted index, the chilling damage index model for the flue-cured tobacco was constructed, and the variation characteristics of the chilling damage index were analyzed by the methods of linear tendency and MannKendall test. In 1961-2009, the yearly variation of the provincial average chilling damage index of the flue-cured tobacco in spring, summer, and autumn presently a decreasing trend, being most obviously in spring, and with a similarity in summer and autumn. The provincial average chilling damage index of the flue-cured tobacco in spring and summer reached the maximum in the 1960s and 1970s and the minimum in 2001-2009, while that in autumn reached the maximum in the 1960s and the minimum in the 1970s. Much more stations showed a decreasing trend in the chilling damage index, and the latter changed significantly in spring and summer but less in autumn. The Mann-Kendall test showed that the yearly variation of the provincial average chilling damage index in spring was significant, with an abrupt change in 1997, but the yearly variation in summer and early autumn was not significant. Thirty percent of the stations in the Province showed a significant abrupt change in spring, and less than 10% of the stations showed the abrupt change in summer and autumn. Most of the abrupt change in each station mainly appeared in the late 1980s and 1990s.