Table of Content

20 May 2008, Volume 19 Issue 05

Previous Issue    Next Issue

Articles

Sensitivity of parameters in net primary productivity model of broadleaf-Koreanpine mixed forest.

ZHOU Chun-hua^1,3;HAO Zhan-qing¹;HE Hong-shi^1,2;ZHOU Dan-hui^1,3

2008, 19(05):  929-935 . 

Asbtract ( 2143 )   PDF (415KB) ( 1033 )  

PnET-Ⅱ (photosynthesis and evapotranspiration) model is an ecosystemprocess model, which requires extensive input parameters, including vegetation parameters, soil parameters and climate parameters, to simulate net primary productivity (NPP). This study estimated the total and wood (stem and branch) NPPs of Korean pine and broadleaf species in Fenglin Natural Reserve, and examined the responses of the NPPs to the variations of the input parameters in PnET-II model. The simulation results indicated that among the vegetation parameters in PnET-Ⅱ model, the variation of canopy parameters had greater effects on the simulated NPPs of Korean pine and broadleaf species, and the response of Korean pine’s total NPP to vegetation parameters was larger than that of broadleaf species’. The variation of soil water holding capacity (WHC) had smaller effects on the NPPs of Korean pine and broadleaf species, and the response of Korean pine’s NPP to the WHC was somewhat smaller than that of broadleaf trees’. In climate scenarios, the variation of air temperature had the greatest effects on the simulated NPP of Korean pine and broadleaf trees, followed by precipitation and radiation.Different climate scenarios had different effects on the predicted results. Thetotal and wood NPPs of Korean pine and broadleaf trees had different responses to the input parameters.

Construction and application of a coupled slope surface-subsurface flow model for forested watershed.

ZHENG Kan^1,2;JIN Chang-jie¹;WANG An-zhi¹;GUAN De-xin¹;PEI Tie-fan¹

2008, 19(05):  936-941 . 

Asbtract ( 2217 )   PDF (1037KB) ( 998 )  

A coupled slope surface-subsurface flow model which can be solved by finite difference method was constructed with saturated infiltration theory, SaintVenant equation, and Richards-equation, and a series of slope runoff generation experiments under conditions of different slope grades and rain intensities were conducted in laboratory. The results showed that the simulated and observed processes of surface-subsurface flow accorded well, with the relative errors of peak time, flow duration, peak flow, and gross flow being mostly less than 10%. This precise and practicable model could be used in further studying the mechanisms of subsurface flow and in providing theoretical basis for improving rainfall-runoff watershed models.

Climate change characteristics in Chinese boreal forest region from 1954 to 2005.

WANG Yu¹;ZHOU Guang-sheng¹;JIA Bing0rui¹;NA Ji-hai²

2008, 19(05):  942-948 . 

Asbtract ( 2153 )   PDF (1232KB) ( 998 )  

In this paper, the change characteristics of air temperature and precipitation in Chinese boreal forest (Larix gmelinii) region from 1954 to 2005 were analyzed, based on the data from eight meteorological stations. The results showed that from 1954 to 2005, the mean annual air temperature in the region increased in a rate of 0.38 ℃·(10 a)^-1, being significantly higher than the global average value during recent 50 years (0.13 ℃·(10 a)^-1). The increasing trend of the temperature appeared in all four seasons, but was only significant in winter and spring (P<0.01). Both the maximum and the minimum mean annual temperatures increased significantly (P<0.01), and the increasing rate was about 0.37 ℃·(10 a)^-1 and 0.54 ℃·(10 a)^-1, respectively. The annual precipitation varied obviously among years, but no significant trend was observed at yearly and seasonal scales. Precipitation days increased but not significantly in spring, autumn and winter, while decreased significantly in summer (P<0.05). The precipitation intensity increased in all four seasons, and was only significant in summer (P<0.05) and winter (P<0.01).

Effects of different forest management alternatives on Sciurus vulgaris habitat.

JIN Long－ru^1,3；HE Hong－shi^1,2；ZONG Cheng⁴；ZHOU Yu－fei^1，3； BU Ren－cang¹

2008, 19(05):  949-955 . 

Asbtract ( 2267 )   PDF (601KB) ( 963 )  

A spatially explicit landscape model LANDIS was applied to simulate the forest landscape changes under four management alternatives (no cutting, clear cutting, selective cutting Ⅰ and Ⅱ) in Youhao Forestry Bureau located in Small Xing’an Mountain from 2000 to 2200. The outcomes from LANDIS were combined with a landscapelevel habitat suitability index (HSI) model in a GIS environment to assess Sciurus vulgaris habitat quality. The results showed that the increase of suitable habitat area and the decrease of marginally suitable area were the fastest under no cutting scenario, and the slowest under clear cutting scenario. Suitable habitat area increased faster while marginally suitable area decreased more slowly under selective cutting Ⅰ scenario than under selective cutting Ⅱ. Overall, the optimal management alternative of S. vulgaris habitat was in the sequence of no cutting, selective cutting Ⅰ, selective cutting Ⅱ, and clear cutting.

Stem respiration of dominant tree species in broad-leaved Korean pine mixed forest in Changbai Mountains.

WANG Miao¹;WU Yao-xiang²;WU Jing-lian¹

2008, 19(05):  956-960 . 

Asbtract ( 2088 )   PDF (634KB) ( 1283 )  

By using soil respiration chamber, the stem respiration of dominant tree species Pinus koraiensis, Quercus mongolica, Fraxinus mandshurica and Tilia amurensis in broad-leaved Korean pine mixed forest of Changbai Mountains was measured from April to October 2003. The temperature on the stem surface and in the forest was determined simultaneously. The results demonstrated that the stem respiration rate of test tree species had an obvious seasonal variation, with the maximum occurred in July and the minimum in October. The diurnal variation of the stem respiration rate was in a ‘S’ curve, with the minimum at 6:00 for all test tree species, and the maximum at 18:00, 20:00, 16:00, and 14:00 for P. koraiensis, Q. mongolica, F. mandshurica, and T. amuremis, respectively. The response of stem respiration to temperature differed with tree species, and the Q₁₀ value ranged from 2.24 to 2.9, which were decreased in the order of F. mandshurica>Q. mongolica>P. koraiensis>T. amurensis.

Foraging behavior of various tree species in heterogeneous nutrient environment related to light condition.

MA Xue-hong; ZHOU Zhi-chun; ZHANG Yi; JIN Guo-qing

2008, 19(05):  961-968 . 

Asbtract ( 2462 )   PDF (281KB) ( 879 )  

A factorial combination pot experiment was designed to study the growth response and foraging behavior of three South China forestation species Pinus massoniana, Schima superba and Liriodendron chinense under heterogenous nutrient envionment and different light conditions. The results demonstrated that under full light, the plant height and biomass of P. massoniana and S. superba were enhanced in heterogenous nutrient environment, with the root biomass increased by 99.5% and 66.7%, respectively, compared with that in homogenous environment; while L. chinense exhibited singnificant growth benefits in homogenous environment. The root scale, foraging precision, and nutrient uptake of S. superba reduced markedly under shading, which in turn decreased the growth benefits in heterogenous nutrient environment. The influence of shading was weaker on P. massoniana than on S. superba, still with some growth benefits for P. massoniana due to its root proliferation and enhanced nutrient uptake in nutrient rich patch. There was a slight influence of shading on the foraging precision and sensitivity of L. chinense root, with no growth response pattern change to heterogenous nutient environment occurred. It was concluded that three tree species not only differed in the inheritance of root foraging mechanism and behavior, but also varied in the response pattern to light condition. Therefore, different measures should be adopted in forestation with the three tree species to enhance the forest productivity.

Niches of plant species in wetlands of the Yellow River Delta under gradients of water table depth and soil salinity.

HE Qiang;CUI Bao-shan;ZHAO Xin-Sheng;FU Hua-ling

2008, 19(05):  969-975 . 

Asbtract ( 2441 )   PDF (510KB) ( 1270 )  

Ordination methods were used to arrange in turn the 19 plant species in wetlands of the Yellow River Delta under gradients of water table depth and soil salinity, and to classify them into three ecological species groups, i.e. low, medium, and high water table depth/soil salinity ecological species groups. Their niche breadths and niche overlaps under the two gradients were also analyzed. The results indicated that for the gradient of water table depth, the species in medium water table depth ecological species group, such as Phragmites australis and Suaeda salsa, occupied a broad niche breadth, and those in high water table depth ecological species group, such as Typha orientalis and Myriophyllum spicatum, occupied the narrowest niche breadth. For the gradient of soil salinity, the species in high soil salinity ecological species group, such as Suaeda salsa and Tamarix chinensis, occupied a broad niche breadth, while those belonging to the medium and low soil salinity ecological species groups occupied a narrow niche breadth. The niche overlaps changed regularly along the gradients of water table depth and soil salinity. In general, the niche overlaps between the plant species of the same ecological species groups were large, whilst those between the plant species of different ecological species groups were small. Niche differentiations of the plant species under the gradients of water table depth and soil salinity might promote species coexistence, and contribute to the explanation of plant zonation mechanisms in this Delta.

Effects of lanthanum on the plant growth and leaf anti-oxidative enzyme activities of cucumber seedlings under nitrate stress.

GAO Qing-hai;WANG Xiu-feng;SHI Qing-hua;YANG Feng-juan;WEI Min

2008, 19(05):  976-980 . 

Asbtract ( 2083 )   PDF (696KB) ( 1108 )  

The study with water culture showed that nitrate stress had significant inhibitory effects on the plant growth, especially the shoot growth of cucumber seedlings. On the 7th day under nitrate stress, the shoot fresh mass per plant decreased by 12.77 g, leaf SOD, POD and CAT activities increased, while leaf APX, DHAR and GR activities decreased significantly, compared with the control. The addition of low concentration (0.05 mmol·L^-1) LaCl₃ increased the shoot fresh mass per plant by 35%, enhanced the leaf thermally stable protein content and SOD, POD, CAT, APX, DHAR and GR activities, and decreased the leaf MDA content and electrolytic leakage, resulting in a definite alleviation of the inhibitory effects of nitrate. However, an addition of high concentration (0.5 mmol·L^-1) LaCl₃ had no obvious alleviation effect. It was concluded that the addition of certain concentration LaCl₃ could alleviate the nitrate stress on cucumber via increasing anti-oxidative enzymes activities and thermally stable protein content.

Effects of maize-peanut intercropping on economic yield and light response of photosynthesis.

JIAO Nian-yuan^1,2;ZHAO Chun³;NING Tang-yuan¹;HOU Lian-tao⁴;FU Guo-zhan²;LI Zeng-jia¹;CHEN Ming-can²

2008, 19(05):  981-985 . 

Asbtract ( 2210 )   PDF (337KB) ( 1161 )  

A field experiment was conducted to study the effects of maize-peanut intercropping on the economic yield of the two crops and the light response of their functional leaves’ photosynthesis. The results showed that maize-peanut intercropping had an obvious yield advantage, with the total economic yield being 2 896 kg·hm^-2 in 2004 and 2 894 kg·hm^-2 in 2005, and enhanced the land utilization rate by 14%-17%. For maize’s functional leaves, the intercropping enhanced their light saturation point, compensation point, and photosynthetic rate under strong light; while for peanut’s functional leaves, it reduced their light saturation point and compensation point but nhanced the apparent quantum yield of photosynthesis and photosynthetic rate under weak light, indicating that maize-peanut intercropping enhanced the utilization efficiency of strong light by maize and that of weak light by peanut, making this intercropping system present an obvious yield advantage.

Effects of slow/controlled release fertilizers on the growth and nutrient use efficiency of pepper.

TANG Shuan-hu;ZHANG Fa-bao;HUANG Xu;CHEN Jian-sheng;XU Pei-zhi

2008, 19(05):  986-991 . 

Asbtract ( 2190 )   PDF (231KB) ( 1218 )  

Pot trails were conducted from 2003 to 2005 to study the effects of slow/controlled release fertilizers on the growth and nutrient use efficiency of pepper. The results indicated that in comparison with conventional splitting fertilization (T₁), basal application of polymercoated controlled release fertilizer (T₂) enhanced the single fruit mass and vitamin C concentration, improved the root activity, and increased the fruit yield by 8.4%, but no significant effect was observed on the dissoluble sugar concentration in fruit. NH₄MgPO₄coated controlled release fertilizer (T₃) increased the dissoluble sugar concentration by 5.67%, but had less effect on single fruit mass and vitamin C concentration. Under the application of T₃, the root system had a vigorous growth at early stages but became infirm at later stages, resulting in a lower yield. Comparing with T₁, the application of 3 slow release fertilizers increased the dissoluble sugar concentration in fruit, enhanced the root activity, but had less effect on the yield. All test slow/controlled release fertilizers increased the use efficiency of N, P, and K significantly, with an exception for T₂ which increased the use efficiency of N and K but decreased that of P. It was demonstrated that an appropriate application of slow/controlled release fertilizers could enhance pepper’s root activity and improve nutrient use efficiency.

Monitoring of wheat leaf pigment concentration with hyper-spectral remote sensing.

FENG Wei;ZHU Yan;YAO Xia;TIAN Yong-chao;YAO Xin-feng;CAO Wei-xing

2008, 19(05):  992-999 . 

Asbtract ( 2363 )   PDF (1343KB) ( 1273 )  

In a two-year field experiment with wheat cultivars under different application rates of fertilizer N, the wheat leaf pigment concentrations were monitored with hyper-spectral remote sensing, and quantitative monitoring models were established. The results showed that the pigment concentrations in wheat leaves increased with increasing N application rate, and differed significantly among- test cultivars. With the growth of wheat, the relative concentration of chlorophyll a+b varied more obviously than those of chlorophyll b and carotenoid (Car), and the sensitive bands of the pigments occurred mostly within visible light range, especially in red-edge district. The analyses on the relationships between eight existing vegetation indices and leaf pigment concentrations indicated that the concentrations of chlorophyll a, chlorophyll b, and chlorophyll a+b were highly correlated with red edge position, and the relationships to REP_LE were better than to REP_IG, giving the determination coefficient R² as 0.835, 0.841 and 0.840, and standard error SE as 0.264, 0.095 and 0.353, respectively. However, the R² values between Car and different spectral indices decreased significantly, and the differences among the spectrum indices were very small. The tests of the monitoring models with independent datasets indicated that REP_LE and REP_IG were the best to predict leaf pigment concentrations. The R² of chlorophyll a, chlorophyll a+b, and Car for REP_LE were 0.805, 0.744 and 0.588, with the RE being 9.0%, 9.7% and 14.6%, respectively, and the R² and RE of chlorophyll b for REP_IG were 0.632 and 18.2%, respectively. It was suggested that the red-edge parameters of hyper-spectral reflectance had stable relationships with the pigment oncentrations in wheat leaves, and especially, REP_LE could be used to reliably estimate the concentrations of leaf chlorophyll a and chlorophyll a+b.

pH and ion balance in wheat-wheatgrass under salt- or alkali stress.

YANG Chun-wu;LI Chang-you;ZHANG Mei-li; LIU Jie;JU Miao;SHI De-cheng

2008, 19(05):  1000-1005 . 

Asbtract ( 2231 )   PDF (239KB) ( 1108 )  

Different intensities of salt- or alkali stress were established by mixing different concentrations of NaCl and Na₂SO₄ or NaHCO₃ and Na₂CO₃, respectively, and wheatwheatgrass (Triticum aestivum L. Agropyron intermedium) seedlings were grown under the stresses for 12 days. The pH value and the Na⁺, K⁺, free Ca²⁺, Cl^-, SO₄^2-, NO₃^-, H₂PO₄-, and organic acid concentrations in the fresh shoots of stressed wheatwheatgrass seedlings were determined, aimed to approach the characteristics of pH and ion balance in wheatwheatgrass under salt- or alkali stress. The results showed that intracellular pH was relatively stable under both stresses. Cl^- concentration increased sharply and organic acid concentration changed less under increasing intensity of salt stress, while it was, in adverse under increasing intensity of alkali stress. Under both stresses, the cations in the fresh shoots were mainly Na⁺ and K⁺, but the anions were different. Under salt stress, inorganic anions were the dominant components and contributed 61.3%-66.7% to the total negative charge, while under alkali stress, the contribution of organic acid to total negative charge increased from 38.35% to 61.6% with increasing stress intensity, and became the dominant component. It was concluded that organic acid accumulation might be a key physiological response of wheat-wheatgrass for its keeping pH and ion balance under alkali stress.

Effects of silicon on flowering Chinese cabbage’s anthracnose occurence, flower stalk formation, and silicon uptake and accumulation.

YANG Xian¹;FENG Hong-xian¹;YANG Yue-sheng²

2008, 19(05):  1006-1012 . 

Asbtract ( 2118 )   PDF (404KB) ( 1063 )  

Different concentrations of silicon (Si) were applied to flowering Chinese cabbbage (Brassica campestris L. ssp. chinensis var. utilisTsen et Lee) to study their effects on the flowering Chinese cabbage’s anthracnose occurrence, flower stalk formation, and Si uptake and accumulation. The results indicated that Si could obviously control the occurrence of anthracnose, and the effect was genotypedependant. The plants of susceptible cultivar applied with 2.5 mmol·L^-1 Si and those of resistant cultivar applied with 0.5 mmol·L^-1 Si exhibited the highest resistance to Colletotrichum higginsianum, with the lowest disease index and the highest flower stalk yield. Si application also obviously affected the quality of flower stalk. For susceptible cultivar, Si application promoted the synthesis of chlorophyll, crude fiber and vitamin C, and induced the formation of soluble sugars. The contents of chlorophyll and crude fiber increased with increasing Si level. For resistant cultivar, the chlorophyll content increased while vitamin C content decreased with increasing Si level, but Si application had less effect on the contents of crude fiber and soluble sugars. For both cultivars, Si application did not have significant effect on the contents of crude protein and soluble protein but remarkably increased the Si accumulation in plant leaves, and the leaf Si content was significantly increased with increasing Si level. The Si granules deposited in leaf tissues were not equal in size, and distributed unevenly in epidermis tissues. It was concluded that the accumulation of Si in leaves could increase the resistance of plant to anthracnose, but there was no linear correlation between the accumulated amount of Si and the resistance.

Effects of different land use types on soil nutrients in karst region of Northwest Guangxi.

XU Lian-fang^1，2;WANG Ke-lin¹;ZHU Han-hua¹;HOU Ya¹;ZHANG Wei¹

2008, 19(05):  1013-1018 . 

Asbtract ( 2143 )   PDF (423KB) ( 1202 )  

Selecting the main land use types (shrub land, secondary forest land, orchard, pasture land, and upland) at the peak-cluster depression in karst region of Northwest Guangxi as test objects, this paper studied the effects of different land use types on soil nutrients. The results showed that, the contents of soil organic matter (SOM), total N, and available N were 86%-155%, 62%-119%, and 66%-215% higher in shrub land and secondary forest land than in orchard, pasture land, and upland, respectively, i.e., increased with the decrease of land use intensity. The contents of soil total P and K were mainly controlled by their origins, but less affected by land use type. Soil available P content was mainly affected by fertilization, while soil available K content was controlled by vegetation cover and water- and soil loss. Land use type was the dominant factor affecting the contents of soil SOM, total N, and available N, P and K. Extensive cultivation could decrease soil nutrient contents and lead to the degradation of cropland soil, while ecological restoration could improve soil fertility. Therefore, in karst region, the measures as changing extensive cultivation into intensive farming, applying organic fertilizers, balance fertilization, and “Grain for Green Project” for ≥25° slope should be taken to recover and rebuild the eco-environment, and keep the sustainable utilization of land resources.

Soil nutrients accumulation and their loss risk under effects of biological soil crust in Loess Plateau of northern Shaanxi Province, China.

XIAO Bo^1,3;ZHAO Yun-ge^1,2;XU Ming-xiang^1,2;SHAO Ming-an¹

2008, 19(05):  1019-1026 . 

Asbtract ( 2132 )   PDF (776KB) ( 1013 )  

The study on the soil nutrients accumulation and their loss risk under effects of biological soil crust (BSC) in a typical basin of Loess Plateau in northern Shaanxi Province showed that with the development of BSC, the nutrient contents in BSC and in 0-2 cm soil layer increased rapidly, but those in deeper layers had less change. Within the 20 years of rehabilitation, the relationship between the nutrient contents in BSC and the rehabilitation age could be described by the exponential equation (y=a［b-exp(-cx)］). The increasing rates of organic matter (OM), total nitrogen (TN), and available nitrogen (AN) in the 20 years changed less, but the contents of total phosphorus (TP), available phosphorus (AP), and available potassium (AK) increased very fast at first 5 years. The yearly average contribution of naturally developed BSC to soil nutrients was 50.15 g·m^-2 of OM, 1.95 g·m^-2 of TN, 0.44 g·m^-2 of TP, 164.33 mg·m^-2 of AN, 9.64 mg·m^-2 of AP, and 126.21 mg·m^-2 of AK. Compared with naturally developed BSC, cultivated BSC had a faster growth rate, and its contribution to soil nutrients, especially to soil available nutrients, was greater. However, the increase of soil nutrients under effects of BSC could intensify the loss risk of soil nutrients with sediments. In this study, 39.06% of increased soil nutrients by BSC were lost with sediments, and 69.04% of them were conserved. Therefore, even though the loss risk of soil nutrients was increased, their net accumulation was still significant, indicating that BSC had better effects on soil nutrients accumulation.

Effects of long-term continuous cropping of cotton and returning cotton stalk into field on soil biological activities.

LIU Jian-guo^1,2; BIAN Xin-min¹;LI Yan-bin²;ZHANG Wei²; LI Song²

2008, 19(05):  1027-1032 . 

Asbtract ( 2269 )   PDF (370KB) ( 1188 )  

The study on the effects of long-term continuous cropping of cotton and returning cotton stalk into field on the quantities of soil microbes and the activities of soil urease, invertase, catalase and diastase showed that the soil biological activities in cotton field were negatively affected by continuous cropping of cotton, but positively affected by the returning of cotton stocks into filed. The obstacle of short-term (5-10 years) continuous cropping was more obvious. After 5 and 10 years continuous cropping and stalk returning, the total quantity of soil microbes was decreased by 3654% and 25.66%, and the quantities of bacteria and actinomyces were decreased by 61.12% and 70.16%, and 67.91%, 145.89%, respectively, while the quantity of fungi was increased, compared with those after 1 year cropping. The activities of soil urease and invertase after 5 and 10 years continuous cropping and stalk returning were decreased by 0.76% and 2.52%, and 28.12% and 11.44%, respectively, and the soil catalase activity after 5 years continuous cropping and stalk returning was decreased by 9.21%, compared with those after 1 year cropping. Under long-term continuous cropping and stalk returning, soil biological properties improved, and soil biological diversity index increased. Compared with those after 5 years continuous cropping and stalk returning, the quantities of bacteria and actinomyces after 15 and 20 years continuous cropping and stalk returning were increased by 71.52% and 61.03%, and 141.74%, 240.83%, respectively, with the proportion of fungi declined and the activities of urase, catalase and invertase increased. Soil amylase activity after 5, 10, and 20 years continuous cropping and stalk returning was increased by 11.38%, 10.41%, and 31.34%, respectively, compared with those after 1 year cropping.

Influence of double rice cropping system innovation on paddy soil profile form and soil characteristics.

ZENG Xi-bai^1,2;SUN Nan³;GAO Ju-sheng³;LI Lian-fang^1,2;WANG Bo-ren³;BAI Ling-yu^1,2

2008, 19(05):  1033-1039 . 

Asbtract ( 2114 )   PDF (291KB) ( 901 )  

Field experiments were conducted on the double rice cropping paddy field in red soil area to evaluate the influence of cropping system innovation on soil profile form and related soil characteristics. Four cropping systems of rice-rice-Chinese Milkvetch (Astragalus sinicusLinn.), forage, paddy-upland rotation, and upland were substituted for the double rice cropping system. The results indicated that compared with those under double rice cropping system, the thickness of cultivated horizon under upland cropping system increased by 4 cm, that of plow pan declined by 2 cm, >2 mm aggregates in wetsieved particle-size fractions increased by 6.94%, wetsieved meanmass diameter increased by 0.37 mm, contents of humic acid carbon and fulvic acid carbon increased by 0.15 and 0.49 g·kg^-1, respectively, and quotient of aggregates water stability was 0.78 times higher. Under paddy-upland rotation, the quotient of aggregates water stability was higher (95.86), while soil nutrient contents changed a little. Under rice-rice-Chinese Milkvetch system, soil organic matter content increased by 1.3 g·kg^-1, quotient of aggregates water stability declined by 8.82, but other parameters had less changes. Under forage system, the thickness of cultivated and transitional horizons increased by 2 cm and 9 cm, respectively, quotient of aggregates water stability increased by 1.39, while the contents of soil organic matter and total potassium decreased by 5.6 and 2.8 g·kg^-1, respectively. Among all test cropping systems, forage system had the greatest changes in soil characteristics. It was completely feasible to substitute the local double rice -cropping system for paddy-upland rotation or upland cropping, particularly in the areas where full irrigation was not available. However, attention should be paid to the decrease of soil potassium content when the cropping system innovation was practiced.

Soil infiltration capacity under different vegetations in southern Ningxia loess hilly region.

YANG Yong-hui^1,3;ZHAO Shi-wei^1,2; LEI Ting-wu^1,4; LIU Han⁴

2008, 19(05):  1040-1045 . 

Asbtract ( 2316 )   PDF (428KB) ( 1008 )  

A new apparatus for measuring the run off-on-out under simulated rainfall conditions was used to study the soil infiltration capacity under different rainfall intensities and vegetations in loess hilly region of southern Ningxia, with the relationships between soil waterstable aggregate content and soil stable infiltration rate under different vegetations analyzed. The results showed that the regression equations between rainfall duration and soil infiltration rate under different vegetations all followed y=a+be^-cx, with R² ranged from 0.9678 to 0.9969. With the increase of rainfall intensity, the soil stable infiltration rate on slope cropland decreased, while that on Medicago lupulina land, natural grassland, and Caragana korshinskii land increased. Under the rainfall intensity of 20 mm·h^-1, the rainfall infiltration translation rate (RITR) was decreased in the order ofM. lupulina land>slope cropland>natural grassland>C. korshinskii land; while under the rainfall intensity of 40 mm·h^-1 and 56 mm·h^-1, the RITR was in the sequence of M. lupulina land>natural grassland>slope cropland>C. korshinskii land, and decreased with increasing rainfall intensity. After the reversion of cropland to grassland and forest land, and with the increase of re-vegetation, the amount of >0.25 mm soil aggregates increased, and soil infiltration capacity improved. The re-vegetation in study area effectively improved soil structure and soil infiltration capacity, and enhanced the utilization potential of rainfall on slope.

Remote sensing quantitative retrieval of soil water content in desertification region.

FAN Wen-yi;LI Ming-ze;YING Tian-yu

2008, 19(05):  1046-1051 . 

Asbtract ( 2117 )   PDF (399KB) ( 1262 )  

An empirical model was set up by using TM data to get the reflectance of the earth surface in Naiman Banner of Kerqin Sandy Land, and the influence of vegetation on the pixel reflectance was eliminated by optical vegetation coverage model. The regression model between soil water content and earth surface reflectance was set up to retrieve soil water content, and the accuracy of the retrieved results were validated by in situ data. The results showed that the theoretical and practical precision was 81.81% and 92.17%, respectively, suggesting that the remote sensing quantitative retrieval of soil water content was scientifically available.

Distribution of water-stable aggregates and aggregate-associated C in black soil in Northeast China.

LIANG Ai-zhen^1,2;ZHANG Xiao-ping¹;SHEN Yan^1,2;LI Wen-feng^1,2;YANG Xue-ming³

2008, 19(05):  1052-1057 . 

Asbtract ( 2244 )   PDF (710KB) ( 1053 )  

The study on the distribution characters of waterstable aggregates and aggregateassociated C in 32 pairs of virgin and cultivated black soils in Northeast China showed that in virgin soils, the amount of water-stable macroaggregates (>0.25 mm) and their associated C in 0-30 cm layer were higher than those of microaggreagtes (<0.25 mm). With the increase of soil depth, the amount of macroaggregates and their associated C showed a decreasing trend, while those of microaggregates increased significantly (P<0.01). The distribution characters of aggregates in cultivated soils were in adverse to virgin soils. Compared with those in virgin soils, the amount of macroaggregates and their associated C in 0-30 cm layer in cultivated soils declined drastically, particularly for >1 mm aggregates. In virgin soils, the proportions of soil macroaggregates, especially for >1 mm aggregates, were positively correlated to soil organic carbon; but in cultivated soils, no obvious relationship was observed between them. The associated C of soil aggregates was positively correlated to soil total organic carbon in both virgin and cultivated soils (P<0.01). In cultivated soils, less C was associated with macroaggregates but 37% more C was associated with microaggreagtes, and the total soil organic carbon was decreased by 29.5%, in comparison with those in virgin soils, which suggested that soil macroaggregates played an important role in the dynamics changes of soil total organic carbon. It was indicated that soil waterstable macroaggregates were sensitive to soil management, and could be an indicator in evaluating the impacts of agronomic managements on soil fertility and soil quality.

Soil organic carbon storage and its spatial distribution in Henan Province.

YU Jian-jun¹;YANG Feng¹;WU Ke-ning²;LI Ling¹;Lv  Qiao-ling¹

2008, 19(05):  1058-1063 . 

Asbtract ( 2054 )   PDF (357KB) ( 1283 )  

By using 1∶200 000 soil database, the soil organic carbon storage in Henan Province was estimated, and its spatial distribution was analyzed. The results showed that in this province, soil organic carbon storage was about 10.27×10⁸ t, accounting for 1.15% of the total in China, and its density was 7.46 kg·m^-2 on average, being lower than that (9.60 kg·m^-2) in this country. The top four soil types in organic carbon storage were fluvo-aquic soil, cinnamon soil, skeletal soil, and yellow cinnamon soil, with the storage all being higher than 1.0×10⁸ t and totally taken up 69.65% of that in Henan. The organic carbon density was the highest in bog soil (24.54 kg·m^-2), followed by in mountain meadow soil (17.69 kg·m^-2) and brown soil (14.64 kg·m^-2). These three soil types mainly distributed in the mountainous areas of west Henan, and the sum of their organic carbon storage was only accounted for 6.34% of the total in the province. The organic carbon density was the lowest in rocky soil (1.32 kg·m^-2) and aeolian sandy soil (1.38 kg·m^-2). In general, the density of soil organic carbon in Henan Province mostly varied from 5 kg·m^-2 to 10 kg·m^-2.

Vegetation change in Shenzhen City based on NDVI change classification.

LI Yijing^1,2;ZENG Hui^1,2;WEI Jian-bing²

2008, 19(05):  1064-1070 . 

Asbtract ( 2266 )   PDF (483KB) ( 1100 )  

Based on the TM images of 1988 and 2003 as well as the land-use change survey data in 2004, the vegetation change in Shenzhen City was assessed by a NDVI (normalized difference vegetation index) change classification method, and the impacts from natural and social constraining factors were conalyzed. The results showed that as a whole, the rapid urbanization in 1988-2003 had less impact on the vegetation cover in the City, but in its plain areas with low altitude, the vegetation cover degraded more obviously. The main causes of the localized ecological degradation were the invasion of built-ups to woods and orchards, land transformation from woods to orchards at the altitude of above 100 m, and low percentage of green land in some built-ups areas. In the future, the protection and construction of vegetation in Shenzhen should focus on strengthening the protection and restoration of remnant woods, trying to avoid the built-ups’ expansion to woods and orchards where are better vegetation-covered, rectifying the unreasonable orchard onstructions at the altitude of above 100 m, and consolidating the greenbelt construction inside the built-ups. It was considered that the NDVI change classification method could work well in efficiently uncovering the trend of macroscale vegetation change, and avoiding the effect of random noise in data.

Estimation of net primary productivity in middle reaches of Yarlung Zangbo River and its two tributaries.

ZHOU Cai-ping¹;OUYANG Hua¹;CAO Yu²;PEI Zhi-yong³;YANG Ding-ding¹

2008, 19(05):  1071-1076 . 

Asbtract ( 2132 )   PDF (574KB) ( 999 )  

Based on the MODIS data and field measurement, the net primary production (NPP) in 2000 and 2006 in the middle reaches of Yarlung Zangbo River and its two tributaries in Tibet were estimated by using a mathematic model. The results showed that in study area, the NPP decreased gradually from valley to ridge, which was accorded with the gradients of precipitation and temperature. The annul NPP per unit area was averagely 86.8 g C·m^-2·a^-1, and was 2.15 g C·m^-2·a^-1higher in 2006 than in 2000. Farmland ecosystem had the highest annual NPP per unit area (243.1 g C·m^-2·a^-1), while desert ecosystem had the lowest one (36.5 g C·m^-2·a^-1). The average total NPP in the two years was 512.8×10¹⁰ g C·a^-1, with the value in 2006 being 12.7×10¹⁰ g C·a^-1 higher than that in 2000. Meadow ecosystem had the highest annual total NPP (194.4×10¹⁰ g C·a^-1), while desert ecosystem had the lowest one (30.3×10¹⁰ g C·a^-1). In 2000-2006, the NPP value in the areas with strong human disturbance (0-4 km away from road) had a decreasing trend, while that in the areas difficult for human to reach was in adverse.

Expansion mechanism of farmland at a village in Horqin steppe of northern China.

ZHANG Le^1,2;LIU Zhi-min¹

2008, 19(05):  1077-1083 . 

Asbtract ( 2020 )   PDF (510KB) ( 802 )  

Based on a multilevel model, the expansion mechanism of farmland in Horqin steppe of northern China was studied at field, household, and village levels. The results showed that there was no significant difference among households in reclaiming the steppe. The households with extra labor force and relatively higher basic education tended to reclaim steppe if they lived mainly on cultivation and animal breeding, while those with large livestock number were not favorable for farmland expansion. Corn cultivation was more sensitive to economic situations, while rice planting was more constrained by natural conditions. Therefore, relatively good basic education might favor the conversion of grassland to farmland, while transferring residual labor forces might detain the trend.

Diel rhythm of benthic macroinvertebrate’s drift in streams in Hengshishui River watershed of Guangdong, China.

DUAN Bo; LI Bin-feng;LIU Ruo-si;TONG Xiao-li

2008, 19(05):  1084-1090 . 

Asbtract ( 2352 )   PDF (955KB) ( 1436 )  

An investigation was conducted on the species composition and diel rhythm of benthic macroinvertebrate’s drift in two adjacent 3rd order streams in the Hengshishui River watershed of Guangdong, China. One of the streams was seriously polluted by acid mine drainage (AMD) discharged from the Guangdong Dabaoshan Mine, with a very low pH (3.45) and high contents of heavy metals that exceeded the Chinese National Standards for surface water, and the another adjacent was a clean stream. The results showed that the individuals and species of benthic macroinvertebrates were much more in clean stream than in AMD-polluted stream. In the drift samples from clean stream, a total of 6871 macroinvertebrate individuals belonging to 52 taxa of 10 orders were collected, among which, 99.5% were aquatic insects. However, the total drift density was dominated by a few taxa, of which, the dominant drift taxa with relative abundance in excess of 5% includedPseudocloeon morum (28.5%), Cinygmina yixingensis (13.8%), Cheumatopsyche sp. (13.2%), Serratella albostriata (7.5%), Chironomidae (6.5%), and Psephenoides sp. (5.0%). The most abundant drifter both in species and in individuals was Ephemeroptera, constituting 65% of the entire caught (dominated by Baetidiae, which represented 63% of total mayfly individuals), followed by Trichoptera (18%). The macroinvertebrate’s drift showed significant diel rhythm, i.e., the drift was strongly nocturnal, with the peaks at 21:00 and 2:00, and the average drift densities being (70.3±10.8) and (289.0±124.6) (ind·100 m^-3), respectively. No diurnal drifter was observed. Most dominant drift taxa showed slightly differences in their drift peaks, but some dominant taxa,e.g., chironomids and Psephenoidessp., showed no clear diel rhythm of drift.Polypedilum sp., an acidophilic species of Chironomidae, was the only drift animal found in AMDpolluted stream, which had three distinct drift peaks, i.e., at 19:00, 0:00 and 4:00, with the highest drift density being only (6.7±5.2) (ind·100 m^-3). It was indicated that AMD not only reduced the numbers and species diversity of drift benthic macroinvertebrates, but also altered their drift patterns.

Effects of microwave irradiation on isolation of soil actinomycetes.

YANG Bin^1,2;XUE Quan-hong²;CHEN Zhan-quan³;ZHOU Yong-qiang¹;ZHANG Xiao-lu¹;XU Ying-jun¹;GUO Zhi-ying²

2008, 19(05):  1091-1098 . 

Asbtract ( 1978 )   PDF (312KB) ( 910 )  

Dilution plate- and agar block methods were employed to study the effects of microwave irradiation on the isolation of soil actinomycetes. The results showed that: 1) Microwave irradiation could significantly increase the total quantity of isolated actinomycetes. With the increasing duration of microwave irradiation, the total quantity of actinomycetes in soils with high organic matter content tended to increase first and decrease then. This quantity on GA and HA culture medium increased by 8.3%-92.6% and 24.4%-108.5% when the irradiation lasted 3-15 minutes, but decreased by 62.1%-78.8% and 41.4%-79.8%, respectively when the irradiation lasted 18-24 minutes, in comparison with that on the control medium. Microwave irradiation showed no remarkable effects on the total quantity of actinomycetes in the soils with low organic matter content. 2) Microwave irradiation also exerted remarkable effects on the number of actinomycetes species. With the increase of irradiation duration, the actinomycetes species number in soils with high organic matter content appeared to increase first and decrease then. When the irradiation lasted 3-24 minutes, the newly identified actinomycetes species on GA and HA culture medium, which included rare actinomycete genera such as Promicromonospora and Streptoverticillium, took up 62.5%-85.7% and 66.7%-83.3% of all the actinomycetes species respectively, and the genus Streptmycete also had obvious variation. Soils with low organic matter content showed the similar tendency. 3) Microwave irradiation could exert remarkable effects on the percentages of antimicrobial actinomycetes strains to all test actinomycete strains. When the microwave irradiation lasted 6, 9, and 15minutes, the percentages of antimicrobial antinomycetes strains on the culture mediums increased by 66.7%, 66.7%, and 83.3%, and the newly identified antimicrobial antinomycetes strains made up 70.0%, 90.0%, and 81.8% of all the antimicrobial antinomycetes strains, respectively.

Development and reproduction of B-biotype Bemisia tabaci on four cucurbitaceous host plants.

XU Cai-xia^1,2;WU Jian-hui^1,2;REN Shun-xiang^1,2;WANG Xing-min^1,2

2008, 19(05):  1099-1103 . 

Asbtract ( 2032 )   PDF (395KB) ( 911 )  

The study on the development and reproduction of B-biotype Bemisia tabaci on four cucurbitaceous host plants, i.e., cucumber, hairy gourd, bitter cucumber, and sponge gourd, showed that the one generation development duration of B. tabaci was the shortest (19.3 d) on hairy gourd and the longest (29.0 d) on bitter cucumber, the survival rate from egg to adult was the highest (92.85%) on cucumber and the lowest (53.08%) on bitter cucumber, the laid eggs were the most (187.4 eggs per female) on cucumber and the least (30.0 eggs per female) on bitter cucumber, and the longevity was the longest (25.2 d) on cucumber and the shortest (10.9 d) on bitter cucumber. The intrinsic rate of increase (r_m) on cucumber, hairy gourd, bitter cucumber, and sponge gourd was 0.1453, 0.1429, 0.0616, and 0.1055, respectively. Among the test cucurbitaceous host plants, cucumber was the most suitable host plant for B. tabaci.

Characteristics in life history of Brachionus forcatus and B. caudatus: A comparative study.

TAO Li-xiang;XI Yi-long;HU Cun-bing

2008, 19(05):  1104-1109 . 

Asbtract ( 2062 )   PDF (377KB) ( 895 )  

By the method of individual culture and with 3.0×10⁶ cells·ml^-1 of Scenedesmus obliquus as the food, a comparative study was made on the characteristics in life history of Brachionus forcatus and B. caudatus at 18 ℃, 23 ℃, 28 ℃ and 33 ℃. The results showed that at 18 ℃ and 23 ℃, both the reproductive stage and the mean lifespan of B. caudatus were longer than those of B. forcatus, and the number of eggs produced by B. caudatus in its whole life was larger than that by B. forcatus. At 28 ℃, there were no significant differences between B. forcatus and B. caudatus in the durations of their main development stages, mean lifespan, and the number of eggs produced. At 33 ℃, the reproductive and postreproductive stages and the mean lifespan of B. forcatus were longer than those of B. caudatus, and the number of eggs produced by B. forcatus in its whole life was larger than that by B. caudatus. At 18 ℃, the life expectancy at hatching, net reproductive rate, and intrinsic rate of population increase were all larger for B. caudatus than for B. forcatus; but at 23 ℃ and 28 ℃, only the life expectancy at hatching was larger for B. caudatus than for B. forcatus. When the temperature reached 33 ℃, the generation time, life expectancy at hatching, net reproductive rate, and intrinsic rate of population increase were all larger for B. forcatus than for B. caudatus. There also existed differences between B. forcatus and B. caudatus in the responses of the durations of their main development stages, mean lifespan, number of eggs produced in whole life, generation time, life expectancy at hatching, net reproductive rate, and intrinsic rate of population increase to increasing temperature. B. caudatus was more adaptable to lower temperature, while B. forcatus was in adverse.

Seasonal and semi-lunar changes in fish community structure in low salinity intertidal area of Yangtze estuary.

ZHANG Heng^1,2;HE Wen-shan¹;TONG Chun-fu¹;LU Jian-jian¹

2008, 19(05):  1110-1116 . 

Asbtract ( 2228 )   PDF (744KB) ( 1092 )  

Based on the survey of the fishes in low salinity intertidal area of the Yangtze estuary from spring (May) 2006 to winter (February) 2007, the seasonal and semilunar changes of fish species and abundances were analyzed. A total of 53 fish species were collected, most of which belonged to Cyprinidae, followed by Gobiidae, and few of other families. The fish species and average abundance were higher in spring, summer, and autumn than in winter and lower in low tides than in high tides in four seasons. Shannon-Weaver (H′) value had a greater fluctuation in a tidal cycle, and was appreciably lower in low tides than in high tides. The fish species and abundance were clustered into two groups, i.e., that of winter, and of the other seasons. As for the whole year, the abundance had the highest positive correlation with water temperature, then with tide height, and lowest with water salinity.

Differences of inherent optical properties of inland lake water body in typical seasons.

SUN De-yong;LI Yun-mei;WANG Qiao;LE Cheng-fen; HUANG Chang-chun;WANG Li-zhen

2008, 19(05):  1117-1124 . 

Asbtract ( 2122 )   PDF (1069KB) ( 1016 )  

Inherent optical property is one of the important properties of water body, which lays the foundation for the establishment of water color analytical models. By using quantity filter technology (QFT) and BB9 backscattering meter, the absorption coefficients of chromophoric dissolved organic matter (CDOM) and total suspended matters (TSM) and the backscattering coefficient of TSM in the water body at Meiliang Bay of Taihu Lake were measured in summer and winter. Based on the spectral comparison of the absorption and backscattering coefficients, their differences between the two seasons were demonstrated, and the reasons that caused these differences were also explored in the context of their relations to the changes in water quality. Consequently, water environment condition could be revealed by using the inherent optical property. The relationship between the backscattering coefficient and the TSM concentration was established, which could provide supporting coefficients to the analytical models to be developed.

Aluminumresistance of AHA1 transgenic Arabidopsis thaliana: Physiological analysis.

WU Yan; SHEN Hong; CHEN Jian-hong

2008, 19(05):  1125-1130 . 

Asbtract ( 2110 )   PDF (441KB) ( 1118 )  

As one of the major genes encoding plasma membrane H⁺ATPase, AHA1 gene plays an important role in regulating plant development and resistance to adverse stress. Taking AHA1 transgenic and wild type Arabidopsis thaliana as test plants, the nutrient uptake, resistance to oxidative stress, and organic acid secretion of the plants under aluminum (Al) stress were examined. The results showed that Al decreased the uptake of nitrogen (N), potassium (K), calcium (Ca) and magnesium (Mg), but increased the phosphorus (P) uptake by A. thaliana roots. AHA1 transgenic plant could accumulate more P and less Al than wild type plant. Al stress induced the increase of plant SOD and POD activities, but no significant difference was observed between AHA1 transgenic and wild type A. thaliana. Al triggered the secretion of organic acids significantly, and AHA1 transgenic plant secreted more organic acids than wild type plant. Vanadate, an inhibitor of plasma membrane H⁺ATPase, could inhibit the secretion of organic acids significantly, while Zn²⁺ and Mg²⁺ could promote the Al-induced secretion, and partially improve the inhibitory effects triggered by vanadate. It was suggested that AHA1 transgenic A. thaliana could increase its Al resistance via enhanced P uptake and organic acid secretion.

Growth vitality and pollutants－removal ability of plants in constructed wetland in Beijing region.

WANG Qing-hai^1,2;DUAN Liu-sheng¹;WU Ju-ying²;YANG Juan³

2008, 19(05):  1131-1137 . 

Asbtract ( 2037 )   PDF (713KB) ( 1205 )  

Nine aquatic plant species commonly found in northern China were transplanted in a horizontal subsurface flow constructed wetland in Beijing region to study their growth vitality in the wetland and their removal ability to the pollutants in domestic sewage. The results showed that the wetland’s front unit had greater contribution to the COD, TN and TP removal than the rear ones, and all test plant species could grow well in the wetland. After growing for 112 days, different plant species had significant differences in their N and P contents and total biomass (P<0.05). For most species, the N and P contents were higher in underground than in aboveground part, and the biomass ratio of under/aboveground part (U/A) was close to or exceeded 1. The accumulated N and P in the plants ranged from 1.36 to 7.89 g·m^-2 and from 0.19 to 1.07 g·m^-2, respectively, and the N and P accumulation in plants were more affected by plant biomass than by its N and P contents. Among the test plant species, Iris pseudacorus ranked the first in setting up the constructed wetland, followed by Typha angustifolia, Acorus calamus, and Triarrhena sacchariflora, whereasAlisma plantago aquatica and Arundo donax were not recommended due to their sensitivity in cold winter in northern China.

Toxic effects of Hg²⁺, Cd²⁺ and Cu²⁺ on cell membrane system ofCabomba caroliniana A. Gray.

GU Wei¹; SHI Guo-xin²;CHAO Jian-guo¹;WU Qi-nan¹; ZHANG Chao-ying²;DU Kai-he²;XU Qin-song²

2008, 19(05):  1138-1143 . 

Asbtract ( 2183 )   PDF (1152KB) ( 1142 )  

By the observation with electron and confocal laser scanning microscopy and the determination of physiological and biochemical reactions, the toxic effects of Hg²⁺, Cd²⁺ and Cu²⁺ on the cell membrane system of Cabomba caroliniana A. Gray were investigated. The results showed that under the actions of the three heavy metal ions, the contents of reactive oxygen species（ROS）and malondialdehyde (MDA) in C. caroliniana leaf cells increased, activities of protective enzymes were in disorder, and lipid peroxidation happened. The cell membrane was damaged, membrane permeability increased, and plasmolysis occurred. Meanwhile, the chloroplast swelled or even disintegrated. The excitement of photosynthetic pigments on thylakoids membrane by light was inhibited, and the auto-fluoresent intensity was decreased. The cristae of mitochondria swelled and decreased, mitochondria membrane was damaged, and nuclear membrane was broken. The effects of Hg²⁺, Cd²⁺ and Cu²⁺ on the cell membrane system of C. caroliniana showed a definite dose-effect correlation, and the stability of membrane system played a key role in the resistance of C. caroliniana to the toxic effects of heavy metals. C. caroliniana was sensitive to Hg²⁺, and the lethal concentration of Hg²⁺ was ranged from 0.3 to 0.5 mg·L^-1. C. caroliniana had relatively higher endurance to Cd²⁺ and Cu²⁺, and could be used as the resistant plant for biological control.

Adsorption and desorption of Bt toxin on three kinds of minerals.

ZHOU Xue-yong^1,2; GAO Jian-bao¹;CAI Peng³;HUANG Qiao-yun³

2008, 19(05):  1144-1148 . 

Asbtract ( 1907 )   PDF (594KB) ( 929 )  

This paper studied the characteristics of the adsorption and desorption of Bt (Bacillus thuringiensis)toxin on goethite, kaolinite, and silica. The results showed that in phosphate buffer (pH 8), the adsorption isotherms ofBt toxin on the test minerals followed Langmuir equation (R²>0.9661), and the adsorbed amounts were in the order of goethite﹥kaolinite﹥silica. The Btoxin was easily adsorbed on the minerals, and the adsorption could reach equilibrium after 1 hour. Within the range of pH 6-8, the amounts of Bt toxin adsorbed on goethite, kaolinite and silica decreased with increasing pH; in the range of 10 ℃-50 ℃, the amounts of the toxin adsorbed on goethite and silica decreased by 8.39% and 47.06%, respectively, while that on kaolinite increased slightly (5.91%). The infrared absorption spectrum showed that there was only a minor alteration of Bt toxin after adsorption. The toxin adsorbed on the minerals was not easily desorbed by deionised water, with the desorption rate ranged from 28.48% to 42.04% after three times washing.

Pollution trend and environmental behavior of perfluorooctanoic acid: A review.

ZHU Ling-yan;LIN Jia-hua

2008, 19(05):  1149-1157 . 

Asbtract ( 2281 )   PDF (367KB) ( 1646 )  

As a kind of emerging persistent organic pollutant (POPs), perfluorooctanoic acid (PFOA) and its salts have caused global ecosystem pollution, and become a new research topic of POPs. Zoological tests indicated that PFOA can damage animal’s liver, reproduction, development, immunity, and gene expression, etc. In a report of U.S. EPA’s Science Advisory Board, PFOA is described as a “likely” carcinogen. The EPA has initiated a PFOA Stewardship Program to commit related industries to voluntarily reduce the contents of PFOA and its salts in their products to decrease the discharge of PEOA and its parent substances into the environment. The developed countries including European countries and the United States are also taking action to promote the risk assessment of PFOA and related substances, and to evaluate the availability of more secure alternative substances. In this paper, the research advances on the physicochemical properties, environmental sources, transportation and fate, and pollution trend of PFOA were briefly reviewed, and additional discussion was given to the priorities of future research on PFOA.

Impact of chemical fertilizers application on soil ecological environment.

LI Dong-po;WU Zhi-jie

2008, 19(05):  1158-1165 . 

Asbtract ( 2295 )   PDF (278KB) ( 1636 )  

China heads the list in the world's chemical fertilizers production and consumption. In 2006, the chemical fertilizers production in this country was 5304.8×10⁴ t, being 14.2% higher than that in 2005. At present, its chemical nitrogen application rate is averagely more than 220 kg·hm^-2, and phosphorous fertilizer application rate is more than 102 kg·hm^-2 （P₂O₅） in single growing season. Some chemical fertilizers in use contain toxic bycomponents such as heavy metals, inorganic acids and organic pollutants, and thus, a long-term application of these chemical fertilizers can possibly induce the accumulation of these by-components in soil, resulting in the worsening of soil ecological environment, and making the heavy metals, nitrate, and other harmful components in agricultural products including vegetables, grains and fruits seriously surpassed the standards. In this paper, the causes, characteristics, and consequences of soil contamination via chemical fertilizers application were discussed, and some countermeasures for the mitigation of agro-ecological environmental pollution by chemical fertilizers were put forward.〗

Correlations between leaf δ¹³C and physiological parameters of desert plantReaumuria soongorica.

MA Jian-ying^1,2,3;CHEN Fa-hu²;XIA Dun-sheng¹;SUN Hui-ling²;DUAN Zheng-hu¹;WANG Gang³

2008, 19(05):  1166-1171 . 

Asbtract ( 2021 )   PDF (995KB) ( 1086 )  

Reaumuria soongorica is a dominant species in the desert shrubbery vegetation in arid regions of northwestern China, playing an important role in the maintenance of the stability and continuity of desert ecosystem. In this paper, a total of 407 individuals in 21 natural populations ofR. soongorica were selected from its main distribution areas to measure the leaf stable carbon isotope composition (δ¹³C) and nitrogen, phosphorus, potassium, water, proline and chlorophyll contents, with the correlations between the δ¹³C value and the test physiological parameters analyzed. The results showed that leaf δ¹³C value was significantly correlated with the contents of leaf potassium, water, and proline (P<0.001), and the correlation with leaf potassium content was most profound (r=0.793), followed by that with leaf water content (r=-0.786), indicating that the variation of leaf δ¹³C value could reflect the nutritional status of the plants, and also, their water-deficient degree. The different distribution trends in leaf δ¹³C value of R. soongoricawere likely caused by stomatal conductance, rather than by nutrient-related changes in photosynthetic efficiency under extremely low available water conditions.