Chinese Journal of Ecology

Effects of exogenous nitric oxide on drought-resistance of poplar seedlings with different drought-tolerance.

FU Shi-lei^1,2; ZHOU Yong-bin³; HE Xing-yuan¹; CHEN Wei¹

2007, 26(07): 967-971 .

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Taking the seedlings of Populus pseudo-simonii Kitag and Populus × euramericana cv. “74/76”as test materials, this paper studied the effects of nitric oxide (NO) donor, sodium nitroprusside (SNP), on their drought-resistance under drought stress. The results indicated that after treated with SNP, the sensitivity of leaf water potential to drought stress, stomatal conductance, and transpiration rate of the two poplar seedlings decreased, while the relative water content and water retention ability of their leaves increased. The contents of soluble sugar and soluble protein in poplar leaves also increased. All of these indicated that SNP could decrease the relative conductance of leaves, increase the drought-resistance of poplars, and alleviate the effects of drought stress. Furthermore, SNP might confer more increased tolerance to P. × euramericana cv.“74/76” than to P. pseudo-simonii, suggesting that this NO donor might be better for drought-sensitive poplar.

Spatial distribution pattern and interspecific association of Populus euphratica and Tamarix ramosissima seedlings populations along desert inland river.

ZHAO Feng-xia^1,2; YIN Lin-ke¹

2007, 26(07): 972-977 .

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In this paper, the methods such as V/m ratio t-test, negative binomial parameter, clump index, mean crowding intensity, index of patchiness, dispersion coefficient, and two-term local variance (TTLV) were used to analyze the spatial distribution pattern and interspecific association of Populus euphratica and Tamarix ramosissima seedlings populations in the middle and lower reaches of the Tarim River. The results showed that the spatial distribution pattern of the two populations all presented significantly aggregative at a block size of 16 m². Based on 2×2 contingency table, the interspecific associations of the two species were examined by means of χ²-test, together with the association coefficient and percentage co-occurrence. The results indicated that the two species showed significantly positive association. It was suggested that the two populations in the study area were in stable distribution pattern, and the two species coexisted and held the common ecological niche.

Changes of plant diversity, biomass, and soil nutrients in cutting slash of artificial sand-fixation forest after fallowing and natural restoration.

WU Xiang-yun; LU Hui; WANG Xiao-jiao

2007, 26(07): 978-982 .

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The vegetation composition and diversity in the process of natural restoration on the clear-cutting forestland of Pinus sylvestris var. mongolica plantations in Zhanggutai district of Liaoning Province were studied by sampling method. The results showed that in the naturally restored plant communities, there were 49 species, belonging to 26 families, and the composite family and grass family took up the most part of the whole. As for the one-year, two-year, three-year and five-year clear-cutting forestlands, the Simpson diversity index of plant communities was 0.681, 0.792, 0.845 and 0.870, respectively, and the Shannon-Wiener index and Pielou index had the similar changing trend as the Simpson index. The total biomass of the naturally restored vegetation increased from 1.351 t·hm^-2 in the first year to 9.745 t·hm^-2 in the fifth year. Litter production started from the second year, and increased from 0.824 t·hm^-2 to 1.403 t·hm^-2 after 5 years. The contents of organic matter, N, P and K in 0-15 cm soil layer increased markedly, in comparing with those prior to clear-cutting. Fallowing played an important role in the early litter production and nutrients accumulation on sandy land.

Relationships between plant community characteristic index and soil factors in Alice Lake wetland.

ZHANG Jiang-ying^1,2; ZHOU Hua-rong¹; GAO Mei^1,2

2007, 26(07): 983-988 .

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In this paper, TWINSPAN and CCA analyses were wsed to study the relationship between plant community characteristic index and soil factors in the Alice Lake wetland of Xinjiang arid area. The results showed that the major 29 plant species in the wetland belonged to 27 genera, 12 families and 4 ecological species groups, and most species had low abundance. Populus euphratica, Tamarix hispida, Phragmites australis and Nitraria sibirica were the most common species. TWINSPAN analysis showed that 25 sampling plots could be classified into three groups. Group 1 contained 6 sites, Group 2 contained 18 sites, and Group 3 contained 1 site, which represented three habitats with different contents of soil organic matter, total nitrogen, and total phosphorus. The results of CCA analysis were basically consistent with those of TWINSPAN analysis, indicating that the major environment variables affecting the plant coverage in Alice Lake wetland were soil organic matter, total nitrogen and total phosphorus.

Temporal variation of plant height, plant cover and leaf area index in intercrop ped area of Sichuan, China.

LIN Chao-wen; CHEN Yi-bing; HUANG Jing-jing; TU Shi-hua

2007, 26(07): 989-994 .

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To study the plant parameters of intercropped crops, the temporal variation of plant height, plant cover, and leaf area index in intercropped area of Sichuan was investigated in 2005. The results showed that the plant height, plant cover, and leaf area index all varied greatly with time. For corn, its maximum plant height was 177 cm, maximum plant cover was 86% occurring at flowering stage, and maximum leaf area index was 1.96. For sweet potato, its maximum and minimum plant height was 22 cm and 12 cm, respectively, maximum plant cover was 73% occurring at tuber expanding stage, and maximum leaf area index was 1.79. When intercropped with corn, all the test plant parameters of sweet potato were strongly affected by corn. In this intercropping system, the most dangerous erosion period was from the corn being harvested to the sweet potato growing up where soil surface uncovered by harvesting corn.

Characters of forest landscape patterns in Linkou Forestry Bureau of Heilongjiang Province.

GAO Rui-xin; YIN Yan-bao; WANG Feng-you

2007, 26(07): 995-1001 .

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With the forest type map (1∶50000) of Linkou Forestry Bureau as the basic information, and by using ArcView 3.3 and Fragstats, this paper analyzed the landscape patterns in this Bureau from the aspects of overall landscape properties, landscape fragmentation index, landscape shape index, perimeter-area fractal dimension, and mean nearest neighbor distance. The results showed that the overall landscape was dominated by forests (56.74%), and residence and farmland also had a high proportion of area. Swamps, shrubs, wastelands, rivers, harvested (and burned) areas, and bare lands were distributed sparsely. Artificial coniferous forest (40.47%) and natural Mongolian oak forests (20.96%) dominated the forest landscapes, with relatively lower fragmentation, comparatively complicated patch shapes, higher perimeter complexity, and comparatively centralized patch distribution. The area of plantation landscapes was nearly equal to that of natural forests, but the plantation landscapes had a higher degree of fragmentation, simpler patch shape, and relatively concentrated patch distribution. Softwood forest patches and hardwood forest patches occupied 11.89% and 7.38%, respectively. The forest landscape in this Bureau was heavily disturbed by anthropogenic activities, and stand structure was unreasonable. Patch structures should be adjusted to meet the need of sustainable forest management.

Quantitative characters of soil microbes and microbial biomass under different vegetations in alpine meadow.

WANG Qi-lan; CAO Guang-min; WANG Chang-ting

2007, 26(07): 1002-1008 .

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By using dilute plate counting and chloroform fumigation methods, this paper studied the quantitative characters of soil microbes, microbial biomass, and organic matter under the vegetations Kobresia tibetica, K. pygmaea, K. humulis, grass, forb, and Potentilla fruticosa shrub in alpine meadow ecosystem. The results showed that in 0-40 cm soil layer, the numbers of bacteria and actinomyces and the contents of microbial biomass C and organic matter were the highest in K. tibetica meadow, while the fungal number was the highest in P. fruticosa shrub meadow. The microbial biomass C and organic matter contents in K. tibetica meadow were obviously higher than those in the other five meadows. Path analysis indicated that there were varied degrees correlations among different bio－environmental factors, and the numbers of soil microbes as well as the contents of soil microbial biomass C and organic matter had significant correlations with soil moisture content, indicating that soil moisture could be a key factor regulating the metabolism of soil microbes and the transformation of substances in alpine meadow ecosystem.

Effects of different fertilization on red soil microbial biomass C in tea garden

XU Hua-qin^1,2; XIAO Run-lin²; YANG Zhi-jian¹;SONG Tong-qing²; XIA Yan-jun¹; LUO Wen¹; LI Sheng-hua³

2007, 26(07): 1009-1013 .

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The study on the dynamics of red soil microbial biomass C in tea garden after 4 years different fertilization showed that straw mulching combined with applying organic manure and chemical fertilizer, intercropping white clover, and applying chemical fertilizer could all increase the amount of soil microbial biomass C significantly. The annual variations of soil microbial biomass C all presented the tendency of low-high-low-high, and the effects of fertilization varied with different periods. The annual average of soil microbial biomass C in treatments T₁ (straw mulching+100% organic manure), T₂ (straw mulching+75% organic manure +25% chemical fertilizer), T₃ (straw mulching+50% organic manure +50% chemical fertilizer), T₄(straw mulching+25% organic manure +75% chemical fertilizer), T₅ (100% chemical fertilizer) and T₆ (intercropping white clover) were 17.05%, 32.38%, 32.05%, 24.30%, 26.23% and 24.63% higher than CK, respectively, and the differences were significant (P<0.05). Soil microbial biomass C had significant positive correlations with soil active organic matter, total nitrogen, and microbial biomass N and P, but no significant correlations with soil available nitrogen, total phosphorus, total potassium, and moisture content. In comparing with applying chemical fertilizer or organic manure alone, their combination was more advantageous in improving soil fertility.

Effects of shading at different growth stages on the growth, development and quality of tobacco.

YANG Xing-you^1,3; LIU Guo-shun¹; WU Ren-jun²; XIA Lin²; XING Xiao-jun⁴; ZHANG Jian-hui⁴; DU Wei-min²; XIE Liang-wen²

2007, 26(07): 1014-1020 .

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A pot experiment was conducted in 2004-2005 to investigate the effects of shading at different growth stages on the growth, development and quality of tobacco. The results showed that under shading, the dry matter accumulation of tobacco plant reduced, leaf blade became thinner, pigment content increased, and maturing time prolonged. The invertase activity decreased under shading, but increased after the shading removed. For flue-cured tobacco leaf, shading reduced its thickness and specific mass, increased its leaf stem and the contents of nicotine and total nitrogen and potassium, decreased its total sugar and reducing sugar contents, and increased its aromatic components. The effects of shading were decreased in the order of maturing stage>vigorous growth stage>root elongation stage.

Effects of land use type on soil organic carbon mineralization in Tiantong, Zhejiang Province.

DAI Hui; WANG Xi-hua; YAN En-rong

2007, 26(07): 1021-1026 .

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Taking Castanopsis fargesii forest as reference, different land use types including Schima superba forest, shrubs, Pinus massoniana forest, plantations of Cunninghamia lanceolat, Pseudolarix kaempferi and Phyllostachys pubescen, Phyllostachys pubescens forest, tea garden, and bare land in Tiantong, Zhejiang Province were selected to investigate their soil organic carbon (SOC) contents, and the SOC mineralization rate after incubated at 25 ℃ and 60% field water capacity over 33 days. The results showed that evergreen broad-leaved forest (Castanopsis fargesii) had the highest SOC content and mineralization rate, followed by coniferous forest, tea garden and bamboo forest, and bare land,while the CO₂-C released from the mineralization of SOC was the lowest in C. fargesii forest, suggesting that evergreen broad-leaved forest had the highest carbon-fixing ability, and the SOC content and mineralization rate would have a significant decrease when the land use type shifted from evergreen broad-leaved forest to others.

Cyanophyta in south subtropical reservoirs with different trophic levels.

LIN Qiu-qi; LEI La-mei; HAN Bo-ping

2007, 26(07): 1027-1033 .

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The distribution patterns of Cyanophyta in two subtropical reservoirs,Xinfengjiang Reservoir and Qieyeshi Reservoir, in Guangdong Province were investigated bimonthly in 2004. A total of 18 genera were identified, and most of them were filamentous and colonial. The most common genera were Pseudanabaena, Limnothrix, Microcystis and Dactylococcopsis, and the Cyanophyta abundance was 4-249 cells·ml^-1 in Xinfengjiang Reservoir and 1911-114228 cells·ml^-1 in Qieyeshi Reservoir. In eutrophic reservoir, Qiyeshi Reservoir, the abundance of Cyanophyta was several orders higher than that in oligotrophic reservoir, Xinfengjiang Reservoir. In both of the reservoirs, the maximum abundance occurred in summer, and temperature was the possible factor controlling the seasonal variation of Cyanophyta abundance. In Xinfengjiang Reservoir, Microcystis was one of the dominant Cyanophyta species, which contributed 35%-97% of the total abundance, and its maximum abundance was found in summer. In Qiyeshi Reservoir,Microcystis abundance was one order higher than that in Xinfengjiang Reservoir, but its relative abundance was lower than 3%.Pseudanabaena and Limnothrix were the dominant Cyanophyta species, and contributed more than 50% of the total Cyanophyta abundance most of the time. The stability of water body and the underwater light condition driven by water transparence seemed to be the key factors inducing Cyanophyta dominated by different ecotypes of species in the two reservoirs.

Isolation of heat response-related gene in cucumber seedlings.

YANG Yin-gui^1,2; LOU Qun-feng¹; ZHUANG Yong¹; ZHANG Wan-ping¹; CHEN Jin-feng¹

2007, 26(07): 1034-1037 .

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To understand the molecular mechanism of cucumber’s heat tolerance or heat injury, heat-tolerant cultivar ‘Xishuangbanna’ and heat-sentitive culticar‘Erzaozi’ were selected as test materials, and their seedlings were heat treated (38 ℃) for 2 hours. The gene was isolated with cDNA-AFLP technique, and the gene expression was detected by RT-PCR technique. A specific fragment of heat response, chrr182 (cucumber heat response-related), was isolated from the cDNA of ‘Erzaozi’ under heat stress, and the results of blastx in GenBank of NCBI indicated that chrr182 was in homology with transcription-repair coupling factor gene. The expression of chrr182 was enhanced under the inducement at 38 ℃ for 2 hour. The heat tolerance or heat injure of cucumber seedlings could be related to the response of transcription-repair coupling factor gene under heat stress.

Photosynthetic physioecology characteristics of Kingdonia uniflora.

LI Yu-hua; REN Jian-yi; LIN Yue; LIU Zhe; LIU Xiao; YUE Ming

2007, 26(07): 1038-1042 .

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By using CI-301PS portable photosynthesis system, this paper studied the photosynthetic characteristics of Kingdonia uniflora under natural condition. The results showed that the diurnal change of net photosynthetic rate (P_n) presented a bimodal pattern,i. e. , reached the maximum at 13:30 and 16:30, and had a midday depression. The diurnal variation patterns of leaf transpiration rate (T_r) and water use efficiency (WUE) were also bimodal. There were significant polynomial regressive relationships between P_n and photosynthetic active radiation (PAR), T_r and stomatal conductance (G_s) (R²=0.2082, 0.2016 and 0.0582, respectively,n=129, P<0.05), while no significant correlation was observed between P_n and air temperature (T_a) (P>0.05). The light compensation point (LCP) was 14.93 μmol·m^-2·s^-1, and the light saturation point (LSP) was 215.76 μmol·m^-2·s^-1, suggesting that K. uniflora could only adapt to restricted light condition.

Effects of added concentrations of Cd and Pb on the distribution of Cd and Pb forms in black soil of northeast China and on the Cd and Pb uptake by cole.

CAO Hui-cong^1,2; WANG Jin-da¹; ZHANG Xue-lin¹

2007, 26(07): 1043-1048 .

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With pot culture and sequential extraction, this paper studied the effects of different added concentrations of cadmium (Cd) and lead (Pb) on the distribution of Cd and Pb forms in black soil and on the Cd and Pb uptake by cole plant. The results showed that with the increasing concentration of added Cd and Pb, there was a remarkable increase in the contents of exchangeable Cd and carbonate- and Fe-Mn oxide-bound Pb in soil. The exogenous Cd in soil was mainly existed in residual and exchangeable forms, while Pb was mainly in residual form but relatively low in exchangeable form. Lower concentration of added Cd and Pb had positive effects on cole growth, while their higher concentration inhibited the growth significantly. The concentrations of Cd and Pb were greater in root than in shoot, and less Pb was transferred to shoot, compared with Cd. The contents of all forms Cd and Pb in soil were positively correlated with those in cole shoot and root, but negatively correlated with cole dry mass. Among all the chemical forms of Cd and Pb, exchangeable form played an important role in the decrease of cole dry mass, and carbonate-bound form contributed most to the absorption of Cd and Pb by cole.

Air negative ion concentrations and their affecting factors in greenbelts of Guangzhou.

ZENG Shu-cai; SU Zhi-yao; CHEN Bei-guang

2007, 26(07): 1049-1053 .

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By using DLY-3G air ion meter, this paper measured the air negative ion concentrations (ANIC) in the greenbelts of Guangzhou, and investigated their relations to the vegetation type, water body status, elevation above sea level, weather conditions, and human activities. The results revealed that the ANIC in Guangzhou greenbelts ranged from 103 to 3 367 ions·cm^-3, with an average of 426 ions·cm^-3 and close to those reported from Shanghai and Shenzhen. The ANIC in test greenbelts decreased in the order of bamboo plantation>Podocarpus nagi plantation > flower plantation >Eucalyptus exserta plantation > nursery ≥turf meadow > residential area, and of broadleaved stand > coniferous and broadleaved mixed stand > coniferous stand. ANIC was higher at the places near running water than near still water, and decreased significantly with increasing distance from running water. It also had an increasing trend with the increase of elevation above sea level. Sunny days had significantly higher ANIC than cloudy ones. Both the number of passers-by and that of vehicles showed significant negative correlations with ANIC.

Relationships between grasshopper occurrence in Inner Mongolia and atmospheric circulation characteristics.

BAI Yue-ming¹; LIU Ling¹; Wulanbater²; GUO An-hong¹;GAO Su-hua¹

2007, 26(07): 1054-1057 .

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To approach the relationships between grasshopper occurrence and atmospheric circulation characteristics is the foundation for establishing synoptic forecast models of grasshopper disaster. By using the principles of statistics, this paper analyzed the relationships between grasshopper occurrences in Inner Mongolia and atmospheric circulation characteristics. The results showed that the southward shift of subtropical anticyclone ridge over the West Pacific in last July was advantageous to the growth and oviposition of grasshopper imagoes, while the northward shift of the north boundary of North America subtropical anticyclone in North Africa Atlantic in February and the stronger polar vortex intensity indices in Pacific Ocean in January had negative effects on the egg mass of grasshopper in winter and its growth in summer. The grasshopper disaster grades were above the third grade when the center of the polar vortex in the Northern Hemisphere in May was located nearby 60°-90°W.

Ecological effects of land use in Poyang Lake region.

ZHANG Fu-qing¹; CHEN Wen-bo²

2007, 26(07): 1058-1062 .

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Supporting by land use geodatabase, and using regional ecological quality index and land use change ecological contribution index, a quantitative study was made on the ecological effects of land use in Poyang Lake region. The results indicated that in this region, the average regional ecological quality index was 7.60 in 1990 and 7.62 in 2002, and the overall ecological quality lay between those of shrubbery and sparse woods. From 1990 to 2002, the main driving forces leading to the improvement of regional ecological quality index were the expansion of pond and reservoir, forest, and sparse woods, while the main reasons for the degradation of regional ecological quality index were the shrinkage of paddy field and middle coverage grassland. As for the land use change ecological contribution index, the sum of the ecological contribution rates in the changes from paddy field to forest, upland to forest, paddy field to sparse woods, and paddy field to pond and reservoir was up to 52.96% of the total, which constituted the main land use change for the improvement of ecological environment, while the sum of the ecological contribution rates in the changes from forest to paddy field, forest to upland, and paddy field to rural residential area accounted for 39.89% of the total, which constituted the main land use change for the degradation of ecological environment.

Forest water conservation and its benefits in upper reaches of Minjiang River in recent 30 years.

ZHANG Wen-guang^1,2; HU Yuan-man¹; ZHANG Jing^1,2; LIU Miao^1,2; YANG Zhao-ping^1,2; CHANG Yu¹; LI Xiu-zhen¹

2007, 26(07): 1063-1067 .

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Based on the differences of physical geography, the forest in the upper reaches of Minjiang River was divided into four types,i. e. , dark coniferous forest, other coniferous forests, broadleaf forest, and shrubbery. The benefits of water conservation by these forest types were calculated by using relevant indicators such as annual rainfall, crown cover interception, runoff coefficient, and ‘shadow price’, and the variations in water conservation were analyzed according to the four remote sensing images in different times. The results indicated that in 2000, the annual water conservation by the forest ecosystems was 1.3892×10¹⁰ m³, and the economic value was 93.07 hundred million Yuan RMB. After deducting the rainfall effect, the annual water conservation and economic value were 1.3348 ×10¹⁰ m³ and 89.43 hundred million Yuan RMB in 1986, and 1.2320 ×10¹⁰ m³ and 82.54 hundred million Yuan RMB in 1995 , respectively, with the water conservation and economic value in 2000 being at the similar levels in 1995. The main reason of these variations was that in 1990s, the forest landscape in the upper reaches of Minjiang River was severely destroyed by human activities, while the policies ‘protecting natural forest’ and‘returning cultivated land into forest-and grassland’ implemented subsequently promoted the establishment of artificial vegetation, improved forest ecosystem, and gradually restored the water conservation by forest ecosystem.

Effects of atrazine on serum estradiol content in male Carassius auratus.

CHEN Jia-zhang¹; MENG Shun-long²; HU Geng-dong¹; QU Jian-hong¹; LENG Chun-mei²

2007, 26(07): 1068-1073 .

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The acute toxicity of atrazine to Carassius auratus and the effects of low level atrazine on serum estradiol contents in male C. auratus at different affecting time and exposure concentrations were studied under laboratory conditions. The results showed that the LC₅₀ of atrazine to C. auratus in 24 h, 48 h and 96 h was 229.33, 146.17 and 105.94 mg·L^-1, respectively, and the safety concentration of atrazine to C. auratus was 10.59 mg·L^-1. Under long term (24 days) exposure, low concentration (0.1-5.0 mg·L^-1) atrazine could induce the synthesis of serum estradiol in male C. auratus. The strongest inducing effect was happened when the concentration of atrazine was 1.0 mg·L^-1, and the content of serum estradiol was increased by 84.1%, compared with the control. However, the synthesis of serum estradiol was inhibited at higher concentration (10.0 mg·L^-1) of atrazine. At 5.0 mg·L^-1 of atrazine, the serum estradiol content in male C. auratus at any affecting time was higher than the control, which was increased by 50% on the 14th day, reaching the highest value. The variation of serum estradiol content could directly affect the reproductive function of male C. auratus, and thus, the male C. auratus whose serum estradiol content had changed significantly due to the enrichment of atrazine in its body was likely to have reproductive problems to some extent.

Microsatellite DNA analysis on genetic diversity of cultured and wild Cyprinus carpio populations in Xiangjiang River.

LIU Zhen¹; LU Shuang-qing¹; KUANG Gang-qiao¹; ZHANG Jian-she¹; LIU Hong-yu²; LIU feng¹

2007, 26(07): 1074-1079 .

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By using microsatellite technology and 17 pairs of microsatellite DNA primers, the genetic diversities of cultured and wild Cyprinus carpio populations in Xiangjiang River were studied. 15 of the 17 pairs of microsatellite primers were amplified with clear bands, among which, 13 pairs presented polymorphism. 2-12 alleles per pair in the two populations were amplified, with 35 alleles coexisted in both of the two populations and 55 alleles in each population. The average number of the alleles per pair was 6.92, and the frequency of the alleles was 0.0667-0.8333. The average heterozygosity and polymorphism information contents of cultured and wild C. carpio populations were 0.5688 and 0.5152, and 0.5860 and 0.5347, and the genetic similarity index and genetic distance were 0.6762 and 0.3238, respectively, indicating that the genetic diversity of the two populations was relatively abundance, and the genetic variability was high.

Tolerance of alien species Hyriopsis schlegeli, native species Hyriopsis cumingii, and their hybrids to three ecological factors.

DONG Zhi-guo^1,2; LI Xiao-ying^1,2; LI Jia-le¹

2007, 26(07): 1080-1084 .

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The tolerance of alien species Hyriopsis schlegeli (C), native species H. cumingii (S), and their reciprocal hybrids F₁ SC and CS to low dissolved oxygen, drying condition and heavy metal Hg was studied to evaluate the ecological risk of introducing alien species H. schlegeli. The results indicated that CS had the strongest tolerance to low dissolved oxygen, with its asphyxia point being 0.92 mg·L^-1, followed by C and SC, with their asphyxia point being 1.04 mg·L^-1 and 1.10 mg·L^-1, respectively, while S had the weakest tolerance to low dissolved oxygen, with its asphyxia point being 1.31 mg ·L^-1. In this aspect, S had significant differences (P<0.01) with the others. No significant difference was observed on the tolerance to drying condition between H. schlegeli and its reciprocal hybrids F₁, but there existed significant difference between H. cumingii and the others. The tolerance to heavy metal Hg was in the order of C＞CS ＞SC＞S, judging from the median-lethal concentration of Hg²⁺. It could be concluded that alien species H.schlegelii had a stronger tolerance than native species H. cumingii, and the inspection and precaution of H. schlegeli should be strengthened to avoid its threatening the survival of H. cumingii.

Conception of secondary forest and its relation to ecological disturbance degree

ZHU Jiao-jun^1,2; LIU Shi-rong³

2007, 26(07): 1085-1093 .

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With the past century’s continued destruction of primary forests, secondary forests became the major forest resources in China and all over the world . There is a considerable ambiguity or confusion with regard to the conception of ‘secondary forest’ in different countries or regions, although this term has been used worldwide for more than a century. This fact is inconvenience for the researches in ecology and forest science. Additionally, the imprecise definition could be a major impediment in communicating with general public and decision-makers. Based on a wide range of literature collection on the conception of secondary forest, as well as the practices and researches of ecology and management of secondary forests, this paper analyzed the uncertainties of the conception of secondary forest, and considered that secondary forests were the forests regenerated through natural regeneration, or through natural processes with minor assisted natural regeneration after the destructive disturbances of original forest vegetations by human beings or by extremely natural causes, and the forests display significant differences in forest structure, canopy species composition, and/or functions with respect to the primary forests. However, there are still many uncertainties in the definition of secondary forest, e. g. , how to define the destructive disturbances of human beings and the extremely natural causes, what degrees of the changes of forest structure, canopy species composition or functions are the significant changes for secondary forest formation, and how to determine the contribution of human activity in the artificially assisted natural regeneration. The definition of secondary forests was put forward by the specialists on plant succession, without taking the duration of disturbance into consideration. In fact, whether the primary forests or secondary forests, they are both in some stages or states in the successional series of forest community. Therefore, if the concepts of forest disturbance degree, forest naturalness, or forest ecosystem maturity can be applied in defining secondary forest to express the state of current forests, the uncertainties of the term of secondary forest may be avoided. In order to discuss the issues related to the concepts of secondary forest with ecologists or foresters, the primary concepts of forest naturalness, forest ecosystem maturity, or forest disturbance degree were mentioned, but related research and practice still need to be strengthened.

Nitrogen source and its uptake by plants in terrestrial ecosystems.

LUO Xu-qiang^1,2; WANG Shi-jie¹; LIU Xiu-ming¹

2007, 26(07): 1094-1100 .

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Nitrogen is a necessary nutritional element, and also, a main limiting factor in plant growth. The nitrogen source and its uptake by plants in terrestrial ecosystems are controlled by their types and habitats. The change of environments can change the plant nitrogen supply through changing the nitrogen form, concentration and distribution, and may lead to the change of soil quality, water regime, and illumination condition. These changes often bring coupling phenomena, and affect plant physiological and ecological characteristics, which subsequently affect the nitrogen uptake and utilization by plants. Moreover, these changes also lead to the variations of plant populations and biological diversity, and hence, directly affect the function and evolution of ecosystem. This paper mainly summarized the nitrogen sources in higher plants growing in terrestrial ecosystems, and analyzed the affecting factors during their nitrogen uptake and utilization. The prospect in this research field was discussed.

Research progress in ecological processes in dune slacks.

ZHANG Le^1,2; LIU Zhi-min¹

2007, 26(07): 1101-1106 .

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As a key protected habitat type in the International Conservation Agenda, dune slack has received much attention in recent 50 years. From the aspects of vegetation processes, soil processes, hydrological processes, effects of scale on ecological processes, as well as biodiversity conservation and ecological restoration, this paper reviewed the main research contents and progress in ecological processes in dune slakes. In recent decades, the related researches are being undergone the shifts from single scale to multi-scale or cross-scale. To elucidate the mechanisms of different ecological processes, the transition from observational study to manipulation experiment has also become one of the characteristics. However, the effects of scale on ecological processes in dune slacks should be further approached, and the influences of dune slack landscape pattern on ecological processes should be better understood. For the future, the studies on the ecological processes in dune slacks in semi-arid region would be in progress, and the theories and methodologies of disturbance ecology and landscape ecology would be applied extensively.

Research advances in assessment of green GDP indicator.

XIU Rui-xue¹; WU Gang¹; ZENG Xiao-an^1,2; SUN Jian-guo³;YU De-yong¹

2007, 26(07): 1107-1113 .

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The study of green GDP and green national accounting systems area hotpot issues in ecology and economy, which play an important role in boosting the sustainable development of economy, society and environment. This paper introduced the concepts of green GDP, its intrinsic meanings, and theoretical foundations of how they came into being. The measuring pathways of green GDP and several indicators, such as genuine saving (GS), index of sustainable economic welfare (ISEW) and genuine progress indicator (GPI) were put forward, which could distinguish the economic activities being able to improve or impaire the sustainability of development. The applications of green GDP indicators in China and abroad at national and municipal levels were analyzed, and the relations of green GDP with ecological footprints and ecosystem services valuation were summarized. Suggestions on green GDP study were made, focusing on the resources and environment valuation methods. Some problems existing in the measurement of green GDP still need to be solved and improved in the future.

Research advances in regeneration of woody plants by sprouting.

CHEN Mu^1,2; CAO Min¹; LIN Lu-xiang^1,2

2007, 26(07): 1114-1118 .

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Sprouting is one of the vegetative propagation modes of plants. This paper summarized the differences between two regeneration modes,i. e. , sprouting and seeding, the measurement of sprouting ability, the factors affecting sprouting processes, and the application of sprouting index in ecosystem assessment . Compared with seeding, sprouting regeneration shows strong ability in disturbance-resisting and vigorous growth of young ramets, which consequently accelerate the early succession of plant community. However, tree species in relatively stable habitats with fewer disturbances tend to regenerate by seeding. Sprouting shows uncertainty to some extent. There are many factors affecting sprouting, including stump height, the positions when the sprouts occur, root biomass and length, disturbance regimes and intensity, light environment, and availability of nutrient recourses. Theoretically, there is an optimum range of sprouting index in a healthy and stable forest ecosystem.

Lake ecosystem elasticity coefficient: Theory and application.

LONG Zou-xia;YU Xing-guang

2007, 26(07): 1119-1124 .

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Based on the particularity of urban lake tropic state and the progress in lake ecosystem health evaluation, it was demonstrated that the relationship between ecosystem health index (EHI) and trophic state index (TSI) of response and non-response lakes was near quadratic function. The lake ecosystem elasticity coefficient was put forward, and the EHI was improved, which could better reflect the healthy condition of various lakes, and made the theory of Xu et al. more perfect and applicable. The improved EHI might be a quantitatively computable formula, which was closest to the healthy index concept defined by Costanza as yet and applied successfully in the ecosystem health evaluation of Xiamen Xinglin Bay.

In situ capping technology for remediation of contaminated sediment.

TANG Yan^1,2; HU Xiao-zhen¹; LU Shao-yong¹

2007, 26(07): 1125-1128 .

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This paper provided an overview on the adverse effects of contaminated sediment and on the in situ capping technology,a simply operated and low cost technology for the remediation of contaminated sediment. When doing capping, some clean materials are placed on the top of contaminated sediment to control the pollution of contaminated sediment by fence, fixation and absorption. The characteristics of capping material, such as particle diameter,specific surface area, microporosity and density greatly correlate with the effect of remediation,which should be accorded with the optimum capping material selection and capping thickness determination. The advantages and disadvantages of in situ capping technology, as well as its applicable conditions and ranges were discussed. Several modes of in situ capping constructions, their excellence and shortcomings were introduced,and a great many of domestic and overseas successful in situ capping projects were illustrated. The prospects of in situ capping applied in China were analyzed.

Environmental monitoring in checking before acceptance of project construction.

GENG Xiao-mei

2007, 26(07): 1129-1132 .

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Using the example of the checks to the environmental protections of Jinshao Irrigation Project, by which executed Assessing and Auditing Center of State Environmental Protection Administration of China, with the cooperation of Liaoning Environmental Monitoring Center, this paper discussed the important role of environmental monitoring during construction item checking before acceptance and how to carry out environmental monitoring. In order to reduce environmental pollution to a minimum during construction period, to protect ecological environment and ambient human heath, it is important to execute ecological monitoring from the beginning of the item.

A modified method for measuring soil hydroxylamine reductase activity.

SHI Yun-feng^1,2; WU Zhi-jie¹; SHI Yi¹; CHEN Li-jun¹; WANG Shu-yi^1,2

2007, 26(07): 1133-1137 .

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In this paper, the traditional measuring method of soil hydroxylamine reductase activity was partially modified. The anaerobic condition needed for the measurement was created by a 3-5 cm fluid seal, which was made from the boiled water having been cooled down under airproof condition. The air above the fluid seal was exhausted with N₂ current to prevent O₂ dissolving into water. Compared with traditional methods, this method could reduce the uncertainty and the complexity in operation, and increase the maneuverability. Taking iodometric analysis as the reference, four spectrophotometric methods were adopted to determine the hydroxylamine concentration in extract, and the results showed that ammonium ferric sulfate-phenanthroline method was of high accuracy and precision, being feasible in measuring soil hydroxylamine reductase activity.

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