[Effects of Balanced Fertilization and Straw Mulching on Soil Nutrients and Stoichiometry in Purple Soil Slope].

To explore the effects of long-term balanced fertilization and straw mulching on soil nutrients and stoichiometric ratios in purple soil sloping cropland, nine plots (length 7 m×width 3 m) were established in Dianjiang County as the research sample area of long-term farmland nitrogen and phosphorus loss monitoring. The following three treatments were set up:conventional mode (CK), balanced fertilization mode (M1), and balanced fertilization+straw mulching mode (M2), with three replications for each treatment to compare the contents of carbon (C), nitrogen (N), phosphorus (P), and potassium (K) and their stoichiometric changes under different treatments from 2018 to 2020. The results showed:K contents showed significant differences among the three treatments in 2018, in the order of CK>M2>M1. NO3--N and NH4+-N contents showed significant differences among the three treatments in 2019, both in the order of M1>M2>CK. Other nutrient contents showed no significant difference among different treatments each year. Soil C and N contents showed non-significant differences among different years. The total K contents of CK, M1, and M2 in 2018 were significantly higher than that in other years and were 78.26% and 98.79%, 19.13% and 35.4%, and 54.49% and 41.76% higher than that in 2019 and 2020, respectively. The total P content in the CK and M2 treatments decreased with years, and that of CK and M2 in 2018 was 20.29% and 10.67% and 39.68% and 17.33% higher than that in 2019 and 2020, respectively. The available potassium (AK) content of the three treatments showed non-significant differences among different years, whereas the contents of nitrate nitrogen (NO3--N), ammonium nitrogen (NH4+-N), and available phosphorus (AP) showed significant differences among the different treatments, with all being the highest in 2020. Soil C:P, C:K, N:P, N:K, and P:K ratios of each treatment showed significant differences among different years (P<0.05). Soil C:K, N:K, and AN:AP ratios all showed significant differences among different fertilization modes in 2018 and 2019, respectively (P<0.05). There was a significantly linearly positive relationship between soil C and N concentration and soil P and K concentration. There were very significant linear positive correlations between soil C:K and C:P, N:K, N:P, and P:K; N:K with C:P, P:K, and N:P; and N:P with C:P, N:P, and C:P. Soil P concentration was highly significantly linearly negatively correlated with C:K and N:K ratios. There were significant positive correlations between soil NO3--N, NH4+-N, AN:AP, and AN:AK; NH4+-N, AN:AP, and AN:AK; and AN:AP and AN:AK. The results suggested that balanced fertilization and straw mulching was a more suitable management mode for purple soil sloping cropland.

[Characteristics of Runoff-related Total Nitrogen and Phosphorus Losses Under Long-term Fertilization and Cultivation on Purple Soil Sloping Croplands].

To elucidate the effects of long-term fertilization and cultivation on runoff rates and runoff-related nitrogen (N) and phosphorus (P) losses, the following five treatments were established on sloping purple soil cropland:① no fertilizer with downslope tillage (CK), ② combined application of manure and fertilizer with downslope tillage (T1), ③ chemical fertilizers with downslope tillage (T2), ④ chemical fertilizer with increasing fertilization with downslope tillage (T3), and ⑤ chemical fertilizer with contour tillage (T4). The runoff rate, runoff-related total N (TN), and total P (TP) concentrations and their loss rates from 104 erosive rainfall events were determined for the period 2008-2019. Results showed that although runoff rates were not significantly different among the fertilization treatments (P>0.05), runoff was markedly lower in fertilization treatments than in the CK treatment (P<0.05). Runoff-related TN concentrations were significantly higher in the CK compared to the fertilization treatments (P<0.05), while there were no significant differences among the T2, T3, and T4 treatments, which had higher concentrations than the T1 treatment. Runoff-related TP concentrations were significantly higher from the T1, T2, and T3 treatments than the CK treatment (P<0.05), and were significantly lower in the T4 than the CK treatment (P<0.05). TN loss rates were not significantly different among the fertilization treatments (P>0.05), but were all lower than the CK treatment (P<0.05). Furthermore, TP loss rates were not significantly different among the downslope treatments (P>0.05), but were all higher than the contour treatment (P<0.05). Runoff rates showed no significant relationships with TN and TP concentrations in the CK, T1, and T2 treatments but were significantly negatively linearly correlated in T3 (P<0.05) and significantly positively linearly correlated in T4 (P<0.05). These results potentially provide scientific guidance for the prevention and control of agricultural non-point source pollution on sloping croplands in the purple soil area.

[Stoichiometric Characteristics of Purple Sloping Cropland Under Long-term Fertilization and Cultivation].

Clarification of the effects of long-term fertilization and cultivation on soil organic carbon (C), nitrogen (N), phosphorus (P), and potassium (K) contents and their stoichiometric ratios can contribute to existing research on the C and nutrient biogeochemical cycles and their interacting mechanisms. Such information is also of great significance to fertilization management and for the control of non-point pollution. Fifteen plots (8 m long, 4 m wide) were set up on a representative purple hillslope (15°). Five treatments (three replications) were used on the plots:i) no fertilizer with downslope cultivation (CK), ii) combined application of manure and fertilizer with downslope cultivation (T1), iii) chemical fertilizers with downslope cultivation (T2), iv) chemical fertilizer with increasing fertilization with downslope cultivation (T3), and v) chemical fertilizer with contour cultivation (T4). The C, N, P and K contents and their ratios in the five treatments corresponding to 0-10 cm and 10-20 cm soil depths were compared. The results showed that C, N and P contents for the different treatments were differed significant and could be ranked:T1 > T3 > T4 > T2 > CK (P<0.05). K content was not significantly different among the four fertilizations (P>0.05) but was significantly higher than the CK treatment (P<0.05), and could be ranked:T4 > T3 > T2 > T1 > CK. The C:N ratios in the five treatments were significantly different (P<0.05) at a soil depth of 10-20 cm (T4 > T3 > T1 > CK > T2). The C:P ratios in the five treatments were significantly different (P<0.05) at a soil depth of 0-10 cm (T1 > T3 > CK > T4 > T2). The C:K, N:P, N:K, and P:K ratios for the five treatments at both of the soil depths showed significant differences (P<0.05), and the C:K, N:K, and P:K were ranked as T1 > T3 > T4 > T2 > CK, whereas the N:P ratio was ranked as T1 > CK > T4 > T3 > T2. The C, N, P, and K contents and their stoichiometric ratios decreased with increasing soil depth. Soil C, N and P in the study site showed moderate variations based on their coefficient of variation (CV):37.50%, 38.91%, and 25.35%, respectively. Soil K on the other hand showed a weak variation (CV 5.03%). Soil C:N and C:P also showed a weak variation with a CV of 7.52% and 14.38%, respectively. Soil C:K, N:P, N:K, and P:K showed moderate variations, with a CV of 35.62%, 17.01%, 37.24% and 44.78%, respectively. There were significant positive interrelations among soil C, N, P, and K contents and their stoichiometric ratios (P<0.05). The average N:P ratio was 2.09, which was much lower than the average value for various soil types in China. Our results indicate that soil N is the key limiting nutrient in purple hillslope land, and that the combination of organic and inorganic fertilizers can effectively alleviate the N deficiency in the study area.

[Spatial-temporal Distribution of Nutrients in Hanfeng Lake After Official Operation].

The hydrograph of Hanfeng Lake, which is the largest pre-dam of theThree Gorges Reservoir, varied between the fluvial stage and lake stage after the lake was officially operated, resulting in large shifts in the aquatic biogeochemical processes. To explore the spatial-temporal distribution of nitrogen and phosphorus concentrations and identify their influencing factors in Hanfeng Lake, seven sampling sites were set up to monitor the changes of nutrients and other water indicators at different water depths monthly from January to December 2018. The results showed that completely vertical mixing across water profiles was observed. The nutrient concentrations were not significantly different between the top, middle, and bottom water depths (P>0.05). Total nitrogen concentration decreased from January to September but gradually increased from October to December, with a monthly average concentration of 1.52 mg·L-1. NO2--N concentration decreased in the first four months, increased sharply from May to June, and decreased from July to December with a monthly average concentration of 0.05 mg·L-1. NO3--N concentration gradually decreased from January to June, and gradually increased from July to December. NH4+-N concentration was the highest in July, with a concentration of 0.44 mg·L-1, and the change in other months was not notable, with a monthly average concentration of 0.09 mg·L-1. The concentrations of total phosphorus (TP), dissolved phosphorus, and soluble reactive phosphorus showed insignificant changes in trends throughout the year, with monthly average concentrations of 0.17 mg·L-1, 0.11 mg·L-1, and 0.05 mg·L-1, respectively. The phosphate concentration was mainly sourced from the upstream Nan River and Taoxi River, and gradually decreased from upper Zhendong to the downstream regulating dam. Of these nutrients, TP was the key factor in the growth of algae in Hanfeng Lake.

[Seasonal Variations in Nitrogen and Phosphorus Concentration and Stoichiometry of Hanfeng Lake in the Three Gorges Reservoir Area].

Based on the seasonal changes in the nitrogen and phosphorus concentrations in Hanfeng Lake from March 2017 to February 2018, the nutrient limitation status was evaluated by the stoichiometric molar ratio of nitrogen and phosphorus. The results showed that the average concentrations of TN, DN, and NO3--N were 1.60, 1.25, and 0.91 mg·L-1 in Hanfeng Lake, respectively. The seasonal changes of those indicators were similar, showing the highest concentration in winter and lowest in summer. NO3--N accounted for TN significantly in the water body, and the concentrations of NH4+-N and NO2--N remained at low levels and changed steadily. The average concentrations of TP, DP, and PO43--P were 0.13, 0.09, and 0.06 mg·L-1, respectively. The changes in the concentrations of TP and DP were similar, showing a trend of increasing in spring and summer, and then decreasing in autumn and winter, while the PO43--P concentration showed the trend of fluctuated decrease. TN/TP varied from 11.07 to 56.02, with an average value of 29.23. TN/TP changed seasonally, with the highest value occurring in winter and the lowest value in summer. The conditions of the water body were conducive to growth and reproduction of algae for most of the time during sampling months. The water body was occasionally nitrogen limited and rarely phosphorus limited. The seasonal variation in TN/TP ratio was affected by several factors such as rainfall runoff, fertilizer use, sewage discharge, and aquatic biological activities. Further, protection strategies were proposed for the improvement of the water body in terms of present water quality characteristics in Hanfeng Lake.

[Analysis of the Characteristics of Nitrogen and Phosphorus Emissions from Agricultural Non-point Sources on Hanfeng Lake Basin].

To understand the status of agricultural non-point source pollution and to find out the primary pollution sources and the key control areas in the Hanfeng Lake Basin, the discharges of total nitrogen (TN) and total phosphorus (TP) from farming, livestock and poultry breeding, and rural living in thirty-two counties in 2015 were estimated using the pollutant discharge coefficient method. The spatial distribution characteristics of the quality and intensity of the TN and TP emissions from these sources were investigated using the GIS spatial analysis method. Pollution evaluation and source analysis were also carried out using the equivalent pollution load method. The results show that the total loads of TN and TP in the Hanfeng Lake Basin are 2721.42 t and 492.04 t, respectively. The discharge of pollutants is the largest in the Nanhe Basin and the smallest in the area around Hanfeng Lake. The total pollutant loads from the agricultural non-point sources varied greatly, with fertilizer application and livestock and poultry breeding being the main sources. The contribution from fertilizer application is 76.92%, which represents the primary source of TN and TP pollution in the Hanfeng Lake Basin. Among the townships, the equivalent pollution loads of Dunhao, Tieqiao, and Baiqiao are higher than 350 m3·a-1; thus, these are the key control towns. According to the results of the equivalent pollution method and cluster analysis, the 32 counties were divided into four types of pollution areas. These areas are planting-livestock breeding dominant area, fertilizer-livestock breeding dominant area, fertilizer dominant area, and heavily polluted planting dominant area.

[Hanfeng Pre-reservoir Commissioning Time Variation Feature of the Hydrology and Water Quality in Three Gorges Reservoir].

Hanfeng Pre-reservoir is very rare in the world which is specially designed to reduce the impact of Fluctuating Zone, and it is formed in Hanfeng Lake of Three Gorges reservoir. The Hanfeng Pre-reservoir has many special hydrological characteristics and ecological environment features based on its unique "pre-reservoir" control mode, the wide seasonal wetland of Fluctuating Zone, the huge life pollution and agricultural pollution, and the pressure of huge city and excessive population. HanFeng Lake has a variety of morphological features such as lakes, rivers, and other backwater bay, for the effect of water level regulation in Three Gorges, since the successful commissioning of the Hanfeng Lake pre-dam system in 2015. The change of Hanfeng Lake hydrology and water quality during the commissioning was divided into four periods by combining Hydrological and Morphological Variation characteristics with Water quality indicators time clustering analysis:May to August as T1 (river period); January, March and November to December as T2 (lake period); February, April and September as T3 (water level fluctuation period); October as T4 (algal blooms period) in 2015. Principal component analysis and stepwise regression analysis showed that Eutrophication of Hanfeng Lake was dominated by different dominant components at different times and the water quality index factor which has a significant effect on the Chl-a was also different. Cumulative contribution rates of principal components were 82.93%, 77.61%, 78.32%, 88.40% for each period, respectively. The main water quality indicators of T1 (river period) were DP, TP, SD, pH and the significant influencing index of Chl-a was PC2, so Chl-a was mainly affected by water nitrogen content. The main water quality indicators of T2 (lake period) were TN, DN, DP, TP, NO3--N and the significant influencing index of Chl-a was PC1, so Chl-a was mainly affected by water eutrophication including nitrogen and phosphorus nutrient status. The main water quality indicators of T3 (water level fluctuation period) were SD, NH4+-N, DN, T and the significant influencing index of Chl-a was PC3. so Chl-a was mainly affected by water level fluctuation. The main water quality indicators of T4 (algal blooms period) were TN, DN, DO, NH4+-N, pH, permanganate index, H, NO3--N and the significant influencing index of Chl-a was PC3. so Chl-a was mainly affected by flow rate and hydrodynamic conditions. As mentioned in the review, the frequent and significant water level changes during the commissioning of Hanfeng Lake were the important factors influencing the change of hydrological and water quality characteristics.

[Seasonal Variations of Soil Microbial PLFAs and Soil Enzyme Activity Under the Citrus Plantation in Mt. Jinyun, Chongqing].

The soil microbial community and soil enzyme activity are important parts of soil ecosystem,and they are sensitive to the ecological environment.In this study,citrus plantation in Mt.Jinyun was chosen as the research object.The phospholipid fatty acid (PLFAs) combined with principal component analysis method was used to study the effect of season changes on soil microbial quantity,community structure characteristics and soil enzyme activity at 0-20 cm soil layer under citrus forest.The results obtained from this study were as follows:① The season changes had a significant impact on soil microbes (P<0.05).Moreover,16:0,i17:0,16:1 2OH,18:0,cy19:0ω8c,i17:1ω9c or 16:0 10-methyl were found to be common in all four seasons,and the proportion of each phospholipid fatty acid was 49.57%,41.63%,35.41% and 38.05%,respectively.In various microbial species,the PLFAs content of bacteria was the highest,followed by fungi,and that of actinomycetes was the lowest.Our results revealed that all kinds of micro-organisms showed obvious seasonal variation characteristics.The total PLFAs quantity of citrus forest ranged from 6.868 to 24.085 nmol·g-1,which had a content order of spring >autumn >winter >summer.The PLFAs content of bacteria,G-,G+ and actinomycetes also showed the same variation trend.However,the PLFAs content of fungi showed a different variation trend,i.e.,autumn was the highest,followed by winter and summer,and spring was the lowest.The results suggested that season change also had a significant impact on microbial community functional diversity index.The variation trend of richness index (R) followed the order of spring >winter >autumn >summer.Moreover,the variation trend of diversity index (H') was winter >autumn >spring >summer.Furthermore,the variation trend of evenness index (J) was summer >autumn >winter >spring.The dominance index (D) increased with the change of season.2 Urease showed a change with the seasons following summer >spring >autumn >winter;Soil invertase,soil catalase and acid phosphatase activity changed obviously in autumn,followed by spring,summer,and winter.3 The principal component analysis demonstrated that the PLFAs content of bacteria,G-,G+,actinomycetes and total PLFAs made the greatest contribution to soil fertility followed by that of invertase,catalase,acid phosphatase and fungi.Moreover,our studies showed that the PLFAs content of urease made a minimum contribution to the soil fertility.

[Effect of Nitrogen Deposition on Soil Microbial Community Structure Determined with the PLFA Method Under the Masson Pine Forest from Mt. Jinyun, Chongqing].

Nitrogen deposition increases the productivity of forest-land, yet may cause environmental damage, while soil microorganisms are sensitive to the ecological environment. The objective of this study was to investigate the effects of nitrogen deposition on soil microbial communities and the relationship among soil microbial communities, soil temperature, soil moisture and the concentration of nitrogen deposition in the Masson pine forest. The results might provide a reference for further study on the effects of nitrogen deposition on forest ecosystem of Masson pine. From May 2014 to June 2015, three nitrogen application treatments and the control treatment were set up:low nitrogen [N20,20 g·(m2·a)-1], moderate nitrogen [N40, 40 g·(m2·a)-1], high nitrogen [N60, 60 g·(m2·a)-1] and control treatment [N0, 0 g·(m2·a)-1] in the Masson pine forest. Soil microbial community structure, soil temperature and soil moisture were measured by phosphorus lipid fatty acids (PLFAs) and automated soil CO2 exchange station. The results showed that:1 Seasonal variation had a remarkable effect on soil bacteria, fungi, actinomycetes and the total PLFA(P<0.05), all kinds of soil microorganisms had the highest amounts in spring and the lowest in winter. In different seasons, the response of different soil microorganisms to nitrogen deposition was different. Generally, nitrogen deposition decreased soil microorganisms in spring and autumn, while in summer and winter, nitrogen deposition had a positive effect on soil microorganisms. 2 Nitrogen deposition had a significant effect on soil microbial community structure(P<0.05). In spring and summer, low nitrogen and moderate nitrogen decreased the soil microbial richness index and diversity index, yet increased the evenness index. In the autumn and winter, low nitrogen and moderate nitrogen promoted the soil microbial richness index, diversity index and evenness index. In all four seasons, nitrogen deposition reduced the soil microbial richness index, diversity index and evenness index. 3 Correlation analysis showed that the concentration of nitrogen deposition had a very significant negative correlation with soil bacteria (P<0.01), and a significant negative correlation with total PLFA (P<0.05). Soil temperature had a significant negative correlation with soil actinomycetes. Soil moisture had a significant positive correlation with bacteria and total PLFA. In conclusion, soil microorganisms of Masson pine forest were mainly influenced by soil moisture and less affected by soil temperature in Jinyun Mountain. Nitrogen deposition had a significant effect on microbial community structure and diversity.

[Gray correlation analysis of the impact of land use type on soil physical and chemical properties in the hilly area of central Sichuan, China.] / å·ä¸­ä¸˜é™µåŒºåœŸåœ°åˆ©ç”¨æ–¹å¼å¯¹åœŸå£¤ç†åŒ–æ€§è´¨å½±å“çš„ç°è‰²å ³è”åˆ†æž.

A case study was conducted in a small watershed of Sichuan hilly basin. In order to eva-luate the effect of land use type on soil characteristics, the soil physical and chemical properties of the 0-10 and 10-20 cm soil layers were analyzed through comparison between bare land and four land use types i.e., slope cropland, leveled cropland, orange forest and conservation forest. The results suggested that capillary porosity, non-capillary porosity, total porosity, and contents of soil organic matter, total nitrogen, total phosphorus, alkali-hydrolysis nitrogen, available phosphorus and available potassium under the same land use type in the 0-10 cm soil layer were more than those in the 10-20 cm soil layer, while the soil bulk density was the opposite. Moreover, there was no significant difference in total potassium between the two soil layers. The orange forest had the largest capillary porosity, non-capillary porosity, total porosity, the highest contents of total phosphorus, available phosphorus and the smallest soil bulk density under the same soil layer. The content of soil organic matter was highest under the conservation forest in the 0-10 cm soil layer and highest under the orange forest in the 10-20 cm soil layer. The order of grey correlation was conservation forest (0.9441)> orange forest (0.8858)> leveled cropland (0.6300)> bare land (0.5397)> slope cropland (0.4714) for the 0-10 cm soil layer, and conservation forest (0.8919) > orange forest (0.8401)> leveled cropland (0.5773)> bare land (0.5301)> slope cropland (0.5175) for the 10-20 cm soil layer. In conclusion, conservation forest was the best type to improve soil physical and chemical properties, and slope cropland was the worst type.

[Hanfeng Pre-dam Commissioning Eutrophication Status and Control Evaluation in Three Gorges Reservoir].

To reduce the impact of Fluctuating Zone, the Three Gorges Reservoir pre-dam is rare in the world which is specially designed and is the largest artificial lake body in China. The ecological benefits of landscape, farmland and lake and the social benefits of livable city have been significantly enhanced since the successful commissioning of the Hanfeng Lake pre-dam system. The paper proposed the application of layered hydrology and water quality monitoring for analysis of Tributary runoff and lake body section in the pre-dam commissioning in the whole year, and a total of 17 measured indicators inlucding hydrological parameters such as v, H, etc, physical parameters such as T, pH, SD, DO, TSS etc. and chemical parameters such as permanganate index, Chl-a, TN, DN, NO3--N, NH4+-N, NO2--N, TP, DP, SRP etc. We found that the water quality was poor during beginning drain and impoundment period and was the worst in tributary inflow section of South River, while the best water quality was located in water section of regulating dam in February and October. The TLI Water Quality Evaluation and factor analyses performed have shown that the water body of Hanfeng Lake was slightly eutrophicated, and the main pollution indicators included DN, TN, NO3--N, TP. By the control of pre-dam in three Gorges to eutrophication in commissioning, we found that the average Chl-a reduction effect reached up to 57.73%, the average reduction rate of permanganate index was 28.12%, SRP, TP, TN, TSS, NO2--N, DN, DP etc. were on average cut down by 20.15%-22.81%, the average reduction rates of NH4+-N and NO3--N were 16.92%-18.74%, and the average eutrophic index of water body was reduced by 15.74%. The highest reduction average rate in lake form period appeared from January to March and October to December, and the lowest in river form period was during May to August.The analysis results showed that the commissioning of pre-dam was good and remarkable for controlling eutrophication, and cutting the concentrations of pollutant water storage in the Three Gorges.

[Seasonal Effect of Simulated Nitrogen Deposition on Soil Respiration and Soil Enzyme Activity in Masson Pine Forest in Mt. Jinyun, Chongqing, China].

Soil enzymes involved in the conversion of soil carbon and nitrogen, meanwhile the availability of soil carbon and nitrogen is the base of soil enzymes, yet atmospheric N deposition influences the release of soil CO2 by reduce the activities of soil enzyme. The objective of this study was to investigate the effect of different nitrogen deposition on soil respiration and soil enzymes, and explore the relationship among soil respiration, soil temperature, soil moisture and soil enzymes in the Masson pine forest. The results might provide a reference for further study on the effects of nitrogen deposition on pine forest ecosystem. From May 2014 to July 2015, three nitrogen application treatments and a control treatment were set up: low nitrogen [N5, 20 g·(m2·a)-1], moderate nitrogen [N10, 40 g·(m2·a)-1], high nitrogen [N15, 60 g·(m2·a)-1] and control treatment [N0, 0 g·(m2·a)-1) in the Masson pine forest. We measured soil respiration, soil temperature, and soil moisture simultaneously by using the Automated Soil CO2 Exchange Station (ACE, UK). The results showed that: 1 Soil enzymes and soil respiration had obvious seasonal variation, soil respiration of N0, N5, N10 and N15 was the highest in Summer, followed by the Spring and Autumn, and the lowest in Winter, and no consistent change rule was found in soil enzymes. 2 Generally, nitrogen deposition suppressed soil respiration and soil enzymes, and these inhibitory effects were strengthened with increasing levels of nitrogen deposition. The only exception in which nitrogen deposition enhanced soil respiration was in the Masson pine forest in Winter, In Spring, Summer and Autumn, nitrogen deposition suppressed soil enzymes, while there was difference among Ure, Ive, CAT and ACP in Winter. 3 stepwise regression showed that in control treatment and low nitrogen treatment, T, Ure and Ive made great contributions to the Rs, and Rs rapidly increased with the increase of T, Ure and Ive. In middle nitrogen treatment, T, Ure and CAT made great contributions to the Rs, and Rs increased with the increase of T, Ure and CAT. In high nitrogen treatment, Rs decreased with the increase of Ure, yet Rs increased with the increase of CAT and W.

[Canonical correspondence analysis of summer phytoplankton community and its environmental factors in Hanfeng Lake].

The phytoplankton community in Hanfeng Lake Reservoir, located in the Three Gorges Reservoir Areas of Yangtze River, was investigated from Jun to August 2013. The results showed that 72 species belonging to 7 phyla of phytoplankton were detected in the water. The dominant species were Synedra, Navicula, Melosira, Cocconeis, Scenedesmus, Pseudoanabaena and Merismopedia. The phytoplankton at the entrance of Donghe River was mainly composed of Bacillariophyta, while that at the entrance of Nanhe River was dominated by Cyanophyta and Chlorophyta. Canonical correspondence analysis was applied to investigate the relationships between the distribution of phytoplankton and the environmental factors. The results showed that the species of phytoplankton at the entrance of the Donghe River were influenced by the physiochemical properties of the water, while those at the entrance of Nanhe River were affected by the nutrient status of the water. The key factors influencing the distributions of phytoplankton were temperature, dissolved oxygen (DO), pH, total nitrogen (TN), dissolved nitrogen (DN) and dissolved phosphorus (DP).

[Temporal variation of trophic status in drawdown area of Hanfeng Lake in the storage period of Three Gorges Reservoir in China].

In order to explore the temporal variations of nutrient and biomass in drawdown area of Hanfeng Lake of the Three Gorges Reservoir region, this paper continuously observed the water quality in the storage period of 2013 October to 2014 February. And the concentrations of nutrients, water physical parameters and chlorophyll were determined. The results showed that the concentrations of nutrients and chlorophyll increased, and the nutrition degree increased after the flooding. The concentrations of TN, TP, permanganate index and Chl-a in water in February 2014 were 4.7 times, 1.0 time, 0.2 times and 3.27 times the amount in October 2013. It should be noticed that the concentrations of TN and TP were above the algae growth limit value, which would be easy to cause water eutrophication with prolonged residence time. The single-factor evaluation of Chl-a reflected that the water quality was changed from poor nutrient to eutrophic. The results of N/P showed that TN in Han Feng Lake was a factor limiting the growth of algae in different period. In October to December 2013 and February 2014, TN limited the growth of algae. In January 2014, TP limited the growth of algae. The Chl-a had a significant positive correlation to pH, DO, NH4(+) -N, NO3(-) -N, TN, permanganate index and TP, but significant negative correlations were observed with SD and TEMP. The water quality was influenced by the same source of pollution during the storage period. The result of factor analysis showed that the water quality in riparian zone of Hanfeng Lake was mainly affected by pH, DO, NO3(-)-N, TN, while Chl-a, TP, NH4(+) -N and aerobic organics pollution could not be ignored. The water had self-purification capacity in the early phase of the storage period, the eutrophication aggravated with the increase of retention time, and it should be controlled. During the storage period of the Three Gorges Reservoir, the nutrition levels of south river and east river were relatively high, and the management should be strengthened.

[Effects of Different Altitudes on Soil Microbial PLFA and Enzyme Activity in Two Kinds of Forests].

The soil microbial community is an important part in soil ecosystem, and it is sensitive to the ecological environment. Phospholipid-derived fatty acids ( PLFA ) analysis was used to examine variations in soil microbial community diversity and its influencing factors. The results showed that: there existed 48 PLFAs that were significant in the soil samples from six altitudes. The PLFAs of six altitudes with the highest contents were i16:0, 10Me17:0, 10Me18:0 TBSA. The citrus forest exhibited richer soil PLFAs distribution both in type and amount than those in masson pine. The microbial activity and functional diversity of masson pine were increased with increasing altitudes, and citrus forest gradually decreased, the PLFA content of different microbial groups in each altitude were significantly different. The richness index, Shannon-Wiener index and Pielou evenness index of masson pine in low elevation were holistically higher than those in high elevation. However, the highest richness index of citrus forest was in low altitude, the highest Shannon-Wiener index and Pielou evenness index were in high altitude. The PLFAs content of different microbial groups were closely correlated to the soil enzyme activities and environmental factors. The PLFAs of bacteria, actinomycetes, G⁻ (Gram- positive), G⁺ (Gram-negative) were positively correlated with Ure(urease) , Ive(invertase) , CAT( catalase activity) and forest type, the PLFAs of fungi was significantly correlated with Ure, Ive, CAT, the PLFAs of bacteria, fungi, actinomycetes, G⁻ , G⁺ were significantly negatively or less correlated with elevation. Ure, Ive, CAT, forest type and elevation are the pivotal factors controlling the soil microbial biomass and activities.

[Influence of different slope position and profile in Disporopsis pernyi forest land on soil microbial biomass and enzyme activity in southwest Karst mountain of China ].

Soil microbial biomass and enzyme activity are important parameters to evaluate the quality of the soil environment. The goal of this study was to determine the influence of different slope position and section in Disporopsis pernyi forest land on the soil microbial biomass and enzyme activity in southwest Karst Mountain. In this study, we chose the Dip forest land at Yunfo village Chengdong town Liangping country Chongqing Province as the study object, to analyze the influence of three different slope positions [Up Slope(US), Middle Slope(MS), Below Slope(BS)] and two different sections-upper layer(0-15 cm) and bottom layer(15-30 cm) on the soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), microbial carbon entropy (qMBC), microbial nitrogen entropy (qMBN) , catalase(CAT), alkaline phosphatase (ALK), urease(URE), and invertase(INV). The results showed that the same trend (BS > MS > US) was found for SMBC, SMBN, qMBC, qMBN, CAT and INV of upper soil layer, while a different trend (BS > US > MS) was observed for ALK. In addition, another trend (MS > US > BS) was observed for URE. The same trend (BS > MS >US) was observed for SMBN, qMBN, CAT, ALK, URE and INV in bottom layer, but a different trend (MS > BS > US) was observed for SMBC and qMBC. The SMBC, SMBN, CAT, ALK, URE and INV manifested as upper > bottom with reduction of the section, while qMBC and qMBN showed the opposite trend. Correlation analysis indicated that there were significant (P <0.05) or highly significant (P < 0.01) positive correlations among SMBC in different slope position and section, soil enzyme activity and moisture. According to the two equations of regression analysis, SMBC tended to increase with the increasing CAT and ALK, while decreased with the increasing pH. Then SMBN tended to increase with the increasing URE and INV.

[Effects of biological regulated measures on active organic carbon and erosion-resistance in the Three Gorges Reservoir region soil].

To gain a better knowledge of characteristics of soils and provide a scientific basis for soil erosion control in the Three Gorges Reservoir Area, contents of aggregates and total soil organic carbon (SOC), as well as soil active organic carbon fractions including particulate organic carbon (POC), readily oxidized organic carbon (ROC), dissolved organic carbon (DOC), microbial biomass carbon (MBC) in the 0-30 cm soil layer under seven different biological regulated measures were studied by the field investigation combined with the laboratory analysis. Results showed that the content of the SOC and active organic carbon fractions decreased with the increasing soil depth; the content of the SOC and active organic carbon fractions in 0-10 cm was significantly higher than that in 20-30 cm. The stability of soil aggregates were also significantly influenced by biological regulated measures, the content of > 0.25 mm water-stable aggregates in seven types of biological regulated measures was in the order of Koelreuteria bipinnata + Cassia suffruticasa > hedgerows > closed forest > natural restoration > economic forest > traditional planting > control plot, moreover, the content of 0.25 mm water-stable aggregates correlated positively with the content of SOC. Soils under different biological regulated measures all demonstrated fractal features, and soil under the measure of Koelreuteria bipinnata + Cassia suffruticasa was found to have the lowest value of fractal dimension and soil erodiable K, indicating a relatively strong structure stability and erosion-resistant capacity. Negative correlation was observed when compared the content of active organic carbon fractions with the soil erodiable K. It can be concluded that properties of soil can be managed through biological regulated measures; thence had an influence on the soil erosion-resistant capacity.

[Effects of different planting modes on the soil permeability of sloping farmlands in purple soil area].

Taking bare land as the control, this paper studied the effects of different planting modes on the soil permeability of sloping farmlands in purple soil area. For the test six planting modes, the soil permeability was in the order of Eriobotrya japonica > Citrus limon > Vetiveria zizanioides hedgerows +corn >Leucaena leucocephala hedgerows + corn> Hemerocallis fulva > corn> bare land, and decreased with increasing depth. The eigenvalues of soil infiltration were in the order of initial infiltration rate> average infiltration rate> stable infiltration rate. The soil permeability had significant positive linear correlations with soil total porosity, non-capillary porosity, initial moisture content, water holding capacity, and organic matter content, and significant negative linear correlation with soil bulk density. The common empirical infiltration model could well fit the soil moisture infiltration processes under the six planting modes, while the Kostiakov equation could not.

[Fractions and adsorption characteristics of phosphorus on sediments and soils in water level fluctuating zone of the Pengxi River, a tributary of the Three Gorges Reservoir].

The sediment, one of the key factors leading to the eutrophication of water bodies, is an important ecological component of natural water body. In order to investigate the morphological characteristics and moving-transiting rule of phosphorus in the sediments of the Pengxi River, a tributary of the Three Gorges Reservoir, the distributions of different phosphorus forms on the three cross-section in the sediments and three soil types of riparian zone were investigated using the sequential extraction method. The characteristics of phosphorus adsorption on the sediments were also investigated by batch experiments. The equilibrium phosphorus concentrations at zero adsorption (EPC0) on those sediments were estimated using the Henry linear models. The results show that the total phosphorus (TP) contents of these sediments and soils of riparian zone were 0.80-1.45 g x kg(-1) and 0.65-1.16 g x kg(-1), respectively. Phosphorus in sediments and soils were divided into inorganic phosphorus (IP) and organic phosphorus (Or-P), and the inorganic phosphorus was the dominant component of TP. Of the inorganic phosphorus fractions, the percentages of phosphorus bounded to calcium (Ca-P) and occluded phosphorus (O-P) from sediments were higher than 80%, implying that the contents of phosphorus were mainly influenced by their bedrocks and the sedimentary environmental conditions, not by the activities of human beings. The fractions of Ca-P and O-P were the dominant components of inorganic phosphorus in alluvial soil and purple soil, while the fraction of O-P was the highest in the paddy soil. The EPC0 values of the sediments from the sections of Huangshi, Shuangjiang and Gaoyang were 0.08, 0.13 and 0.11 mg x L(-1) respectively, but the EPC0 values of the alluvial soil, purple soil and paddy soil located in riparian zone were 0.08, 0.09 and 0.04 mg x L(-1), respectively. Correlation analysis shows that the values of EPC0 positively related to the contents of total phosphorus and clay content, and significantly related to the content of Ca-P and pH values. According to the phosphorus concentration in the water of Pengxi River, it concludes that sediments and soils in the zone of fluctuating water level of the Pengxi river can be the sink of phosphorus in summer and autumn, while can be the source of phosphorus in the spring and winter. Therefore, the inherent phosphorus present in sediments and soils would be a major threat to the water quality and ecosystem reservation in the watershed of the Pengxi River.