Effects of gravel on the evaluation of soil organic carbon density in Pinus massoniana plantations.

Gravel (>2 mm) is one of the main parameters for estimating soil carbon pool. To assess the effects of gravel on soil bulk density (BD) and organic carbon density (SOCD) in Pinus massoniana plantations, we estimated the BD and SOCD at the 0-10, 10-20 and 20-40 cm soil depths of 131 plots under two different conditions, with and without removing gravel. The BD of each soil layer after removing gravel was 0.58-1.57, 0.60-1.67, and 0.59-1.75 g·cm-3, respectively, which was significantly lower than that before removing gravel. Gravel increased the BD by 6.5%-6.8%. The SOCD of each soil layer before removing gravel was 8.93-65.97, 7.63-59.08, and 8.79-94.53 t·hm-2, respectively, which was higher than that after removing gravel. Overall, by neglecting the effect of gravel, SOCD was overestimated by 4.9%-11.8%. As gravel content increased, the relative deviation in the estimated BD and SOCD among different methods increased. When the gravel content was higher than 20%, the estimated SOCD at soil layer of 0-40 cm showed a significant difference between neglecting gravel and removing gravel, with the former being 29.7%-47.4% higher than the latter. In conclusion, gravel markedly affected the estimations of BD and SOCD. It was recommended that SOCD should be estimated by the method that not only uses the BD after removing gravel but also considers gravel as a correction factor (especially when gravel content is above 20.0%) to avoid overestimation of soil carbon pool.

[Effects of nitrogen addition on soil microbial biomass and enzyme activities of Pinus massoniana-Quercus variabilis mixed plantations in the Three Gorges Reservoir Area]. / æ°®æ·»åŠ å¯¹ä¸‰å³¡åº“åŒºé©¬å°¾æ¾-æ “çš®æ Žæ··äº¤æž—åœŸå£¤å¾®ç”Ÿç‰©ç”Ÿç‰©é‡å’Œé ¶æ´»æ€§çš„å½±å“.

We examined the effects of nitrogen addition (0, 30, 60, and 90 kg N·hm-2·a-1) to soil microbial biomass, enzyme activities, and nutrient contents of the Pinus massoniana-Quercus variabilis mixed plantations in the Three Gorges Reservoir Area, with the aim to provide a theoretical basis for predicting soil carbon dynamics under the background of continuously increasing atmospheric nitrogen deposition in this area. The results showed that nitrogen addition at all levels led to a significant increase of the contents of organic carbon, total nitrogen, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass phosphorus (MBP) in the forest soil, while a decrease of soil pH-value, and no significant effect on the total phosphorus content. Nitrogen addition increased the activities of ß-1-4 glucosidase (BG), cellobiose hydrolase (CB), acid phosphatase (AP), N-acetylglucosaminosidase (NAG) and peroxidase (POD), while inhibited that of polyphenol oxidase (PPO). There was a significant seasonal variation in soil oxidase activities, in which the peroxidase activity was higher in May and August, and the polyphenol oxidase activity was the highest in August. Soil enzyme activities were significantly correlated with soil moisture and the contents of soil nutrients, MBC, MBN, and MBP. The variation of soil enzyme activities was caused by the comprehensive effects of multiple factors. The redundancy analysis (RDA) showed that the contents of total soil nitrogen and MBC were the main environmental factors driving soil enzyme activities. The continuous increase of atmosphere nitrogen deposition would lead to soil acidification and promote the turnover of soil organic carbon and nutrient cycling in the Pinus massoniana-Quercus variabilis mixed plantations of the study area.

LncRNA TINCR improves cardiac hypertrophy by regulating the miR-211-3p-VEGFB-SDF-1α-CXCR4 pathway.

Cardiac hypertrophy is a common cardiovascular disease that is found worldwide and is characterized by heart enlargement, eventually resulting in heart failure. Exploring the regulatory mechanism of cardiac hypertrophy is beneficial for understanding its pathogenesis and treatment. In our study, we have showed TINCR was downregulated and miR-211-3p was upregulated in TAC- or Ang II-induced models of cardiac hypertrophy. Dual luciferase and RIP assays revealed that TINCR served as a competitive endogenous RNA (ceRNA) for miR-211-3p. Then, we observed that knockdown of miR-211-3p alleviated TAC- or Ang II-induced cardiac hypertrophy both in vivo and in vitro. Mechanistically, we demonstrated that miR-211-3p directly targeted VEGFB and thus regulated the expression of SDF-1α and CXCR4. Rescue assays further confirmed that TINCR suppressed the progression of cardiac hypertrophy by competitively binding to miR-211-3p, thereby enhancing the expression of VEGFB and activating the VEGFB-SDF-1α- CXCR4 signal. Furthermore, overexpression of TINCR suppressed TAC-induced cardiac hypertrophy in vivo by targeting miR-211-3p-VEGFB-SDF-1α- CXCR4 signalling. In conclusion, our research suggests that LncRNA TINCR improves cardiac hypertrophy by targeting miR-211-3p, thus relieving its suppressive effects on the VEGFB-SDF-1α-CXCR4 signalling axis. TINCR and miR-211-3p might act as therapeutic targets for the treatment of cardiac hypertrophy.

Catheter-Based Radiofrequency Renal Sympathetic Denervation Decreases Left Ventricular Hypertrophy in Hypertensive Dogs.

This study explored the effects of renal sympathetic denervation (RDN) on hyperlipidity-induced cardiac hypertrophy in beagle dogs. Sixty beagles were randomly assigned to the control group, RDN group, or sham-operated group. The control group was fed with a basal diet, while the other two groups were given a high-fat diet to induce model hypertension. The RDN group underwent an RDN procedure, and the sham-operated group underwent only renal arteriography. At 1, 3, and 6 months after the RDN procedure, the diastolic blood pressure (DBP) and systolic blood pressure (SBP) levels were markedly decreased in the RDN group relative to the sham group (P < 0.05). After 6 months, serum norepinephrine (NE) and angiotensin II (AngII), as well as left ventricular levels, in the RDN group were statistically lower than those in the sham group (P < 0.05). Also, the left ventricular mass (LVM) and left ventricular mass index (LVMI) were significantly decreased, while the E/A peak ratio was drastically elevated (P < 0.05). Pathological examination showed that the degree of left ventricular hypertrophy and fibrosis in the RDN group was statistically decreased relative to those of the sham group and that the collagen volume fraction (CVF) and perivascular circumferential collagen area (PVCA) were also significantly reduced (P < 0.05). Renal sympathetic denervation not only effectively reduced blood pressure levels in hypertensive dogs but also reduced left ventricular hypertrophy and myocardial fibrosis and improved left ventricular diastolic function. The underlying mechanisms may involve a reduction of NE and AngII levels in the circulation and myocardial tissues, which would lead to the delayed occurrence of left ventricular remodeling.

Parity and carotid atherosclerosis in elderly Chinese women.

BACKGROUND: The relationship between parity and atherosclerosis has been reported in some ethnic populations. However, results regarding Chinese women are still lacking. This study aimed to investigate the association of parity and carotid atherosclerosis, which has a predictive value of subsequent atherosclerotic events in elderly Chinese women. METHODS: A total of 2, 052 participants from the medical examination center of the Third Xiangya Hospital were enrolled in the study. A standardized, structured questionnaire was administered to collect information on subjects' demographic characteristics, socioeconomic status, and cardiovascular risk factors. High-resolution ultrasound was used to examine carotid plaques and carotid intima-media thickness (IMT). RESULTS: The mean age of participants was 66.1 ± 5.5 years. Women with more birth appeared to have a higher risk of carotid artery plaques. A multivariate-adjusted model yielded an odds ratio of 1.38 (95% CI: 12%-70%, P = 0.003) per birth. A positive association was observed between parity and common carotid IMT (ß ± SE: 0.029 ± 0.006, P < 0.001), and internal carotid IMT (ß ± SE: 0.011 ± 0.005, P = 0.03) in a univariate model; however, these associations became non-significant in multivariate-adjusted models. When common carotid IMT was classified into an IMT ≥ 1 mm group and an IMT < 1 mm group, higher parity was associated with more obvious thickening both in the unadjusted model (OR = 1.61, 95% CI: 1.29-2.00, P < 0.001) and in the fully adjusted model (OR = 1.43, 95% CI: 1.09-1.88, P = 0.01). CONCLUSIONS: There is a positive association between parity and risk of carotid plaques, as well as between parity and risk of obvious thickening for common carotid IMT in elderly Chinese women, indicating multiparous women might experience more atherosclerotic challenges.

[Effects of Fertilization on the Nitrogen Residual Amounts and Leaching from Citrus Orchard Soil in the Three Gorges Reservoir Area].

This experiment has the citrus orchard soil in the basin of the Zigui County Ecological Station in the Three Gorges Reservoir Area as its research object. Leaching tests of an undisturbed soil column at 0-20, 0-40, and 0-60 cm depth were performed in a citrus orchard. The effects of nitrogen leaching and residual amounts in the soil were studied. Four kinds of fertilization treatments were set up in the experiment:no fertilization treatment (CK), low nitrogen fertilization treatment (T1:250kg·hm-2), medium nitrogen fertilization treatment (T2:500kg·hm-2), and high nitrogen fertilization treatment (T3:750kg·hm-2). The results showed that:① The main form of nitrogen leaching in citrus orchard soil was nitrate nitrogen (NO3--N), accounting for 36.93%-60.07% of total nitrogen (TN) leaching. The ratio of TN to ammonium nitrogen (NH4+-N) was 4.40% to 5.79%. The ratio of NO3--N residues in soil to TN residues was 11.31‰-45.66‰, and the ratio of NH4+-N residues to TN residues was 1.051‰-2.07‰. ② Nitrogen leaching and residual amounts in citrus orchards at the same depth showed significant positive correlation with the amount of fertilizer applied. The leaching losses and residual amounts of TN in soil at different fertilization rates were 11.35-30.11 kg·hm-2and 0.30-1.86 g·kg-1, respectively. Among them, the ratio of leaching losses of NO3--N and NH4+-N to TN leaching amounts peaked under T2 treatment, and the peaks of NO3--N and NH4+-N residues in TN residual amounts appeared in T1 and T2 treatment, respectively. ③ Given the same fertilization amounts, the leaching amounts and residual amounts of different forms of nitrogen in the soil were greatly affected by soil depth. After fertilization, the peaks of NO3--N leaching and residual amounts appeared at 20 cm and 40 cm, respectively, and the peaks of NH4+-N leaching and residual amounts mainly appeared at 20 cm depth. Inferred from the results of the experiment, the neutral nitrogen treatment in the 0-40 cm soil column is more conducive to the conversion of fertilizer nitrogen to inorganic nitrogen for plant absorption, and reduces the risk of nitrogen leaching after fertilization.

[Characteristics of Nitrogen and Phosphorus Output in Runoff and Rainfall Runoff in Lanlingxi Watershed, Three Gorges Reservoir Area].

The small watershed of an agroforestry system in the Lanlingxi watershed in the Three Gorges Reservoir area was studied by performing continuous monitoring of nitrogen and phosphorus output and concentrations and analyzing the changes in the output of nitrogen and phosphorus in runoff and its response to different rainfall conditions. The results showed that:①The total runoff loss was 50.92×104 m3 in this watershed during the rainy season, with 52.43 kg·hm-2 lost by total nitrogen, including nitrate nitrogen (30.26 kg·hm-2) and particulate nitrogen (21.61 kg·hm-2), and 0.06 kg·hm-2 and 0.10 kg·hm-2 lost by ammonium nitrogen and total phosphorus; ②The distribution of rainfall has the characteristics of stage and strong rainfall during the wet season was the main driving force of soil nutrient output. Rainfall runoff contributed to 88% of total nitrogen loss and 90% of total phosphorus loss in the rainy season; ③The main path of nitrogen and phosphorus loss in the rainy season was the surface runoff caused by rainfall, accounting for 68% of total nitrogen loss and 74% of total phosphorus loss; ④Nitrate nitrogen concentrations showed a negative correlation with rainfall runoff and the output was mainly distributed in the later runoff process. Ammonium nitrogen and total phosphorus concentrations were positively correlated with rainfall and both were mainly distributed in the early stage of the runoff process; ⑤The concentrations of total nitrogen in this watershed exceeded the standard values. The water quality in the rainfall and the non-rainfall period was worse than Grade Ⅴ.

[Long-term changes of land use/cover in the Three Gorges Reservoir Area of the Yangtze River, China.] / 长江三峡库区土地利用/覆盖的长期变化.

Understanding the temporal and spatial dynamics of land use/cover (LUC) can contri-bute to reveal the impacts of climate change and human activities on ecosystems and thus be an important prerequisite for ecosystem management. As an ecologically vulnerable area in China, the Three Gorges Reservoir Area (TGRA) of the Yangtze River presented significant complexity in the response to environmental changes. However, there is a general lack of understanding in the underlying mechanism. In this study, we interpreted the time series remote sensing images derived from the Landsat sensors to map the LUC of the TGRA, and aimed to analyze the long-term changes in the distribution and structure of LUC and elucidate the evolution process of LUC, which could provide a scientific basis to understand the complexity of ecosystem changes and regional ecosystem management in ecologically fragile regions. The results showed that the TGRA presented the significant changes in spatial heterogeneity of LUC structure from 1990 to 2015. Meanwhile, the landscape changed from farmland to woodland (forest and shrubland). Farmland decreased from 66.2% to 40.4%, but woodland increased from 31.3% to 53.5%, buildings and water area increased gradually. Forest gradually spread to the middle of the TGRA, while the buildings presented a scattered expansion. In the altitude zone of 500-1000 m and slope zone of 15°-25°, woodland increased noticeably, and the coniferous forest, mixed forest and shrubland had a higher growth rate. In the study period, due to the urban construction and the various ecological restoration projects in the TGRA, the LUC structure varied with the dam's impoundment and was characterized by the ecosystem restoration. Ecological restoration projects were helpful to reduce the negative impacts of urban construction and economic development on the environment.

[Land Use Structure Change and Its Control Effect of Nitrogen Output in a Small Watershed of Three Gorges Reservoir Area: A Case Study of Lanlingxi Watershed].

The nitrogen (N) output in Lanlingxi watershed of Three Gorges Reservoir Area in 2015 was monitored and the current land use map was investigated. Cluster analysis and correlation analysis were used to identify the major sources of pollutants and to discriminate the source and the sink land use types. The effects of land use on N exports were quantitatively analyzed by stepwise regression analysis. The results showed that: ① After the returning farmland to forest project the land use structure of this area changed dramatically. The area proportions of forest land and garden plot increased to 76.85% and 13.87% respectively, and the proportion of cultivated land dropped to 1.16%. Cultivated lands were stellate distributed and garden plots in some catchments were flake distributed. ② The content of TN in some monitoring points surpassed the Class V standard of the national groundwater environmental quality. The ammonium-N (NH4+-N) concentrations ranged 0.089-0.214 mg·L-1, 2.925-13.203 mg·L-1 for nitrate-N (NO3--N) and 3.561-14.572 mg·L-1 for total-N (TN). And NO3--N accounted for more than 80% of TN. ③ There were significant positive correlations between garden plot, residential land and N loss, and negative correlations between forest land, unutilized land and N export, which indicated that the former were N sources and the latter were sinks. ④ Forest land area should be increased and garden plot should be controlled, and the area ratio of residential land should be kept below 5% when adjusting land use structure of this watershed. Moreover, forest-tea and forest-fruits modes should be applied to change single land use type of garden plot in some catchments.

[Control of Soil Nutrient Loss of Typical Reforestation Patterns Along the Three Gorges Reservoir Area].

Annual soil nutrient loss characteristics on typical reforestation patterns in watershed along the Three Gorges Reservoir Area were studied based on runoff plot experiment. Runoff and sediment nutrition content from May to October 2014 of typical reforestation patterns including garden plot (tea garden), forest land (Chinese chestnut) and the original slope farmland were determined and then analyzed. The results showed that: (1) After the Returning Farmland to Forest Project the quantity of annual soil nutrient (nitrogen and phosphorus, the sum of them in sediment and runoff) loss decreased. The output of total nitrogen (TN) was in the order of slope farmland (2 444.27 g x hm(-2)) > tea garden (998.70 g x hm(-2)) > Chinese chestnut forest (532.61 g x hm(-2)), and for total phosphorus (TP) loss was slope farmland (1 690.48 g x hm(-2)) > tea garden (488.06 g x hm(-2)) > Chinese chestnut forest (129.00 g x hm(-2)) . Compared with slope farmland, the load of TN and TP output of reforestation patterns decreased 68.68% and 81.75%, respectively. (2) Compared with slope farmland, available nitrogen loss decreased in reforestation patterns. Total nitrate nitrogen (NO3(-)-N) loss ranked in the order of slope farmland (113.79 g x hm(-2)) > tea garden (73.75 g x hm(-2)) > Chinese chestnut forest (56.06 g x hm(-2)) The largest amount of ammonium nitrogen (NH4(+)-N) was found in tea garden (69.34 g x hm(-2)), then in farmland (52.45 g x hm(-2)), and the least in Chinese chestnut forest (47.23 g x hm(-2)). (3) The main route of NO3(-)-N and NH4(+)-N loss was both through runoff, the quantity of NO3(-)-N and NH4(+)-N output in which accounted for 91.4% and 92.2% of the total, respectively. The quantity of TN and TP in sediment accounted for 86.6% and 98.4% of the total. TN and TP loss showed an extremely significant correlation with sediments, which showed that sediment output was the main approach of TN and TP loss.

The effects of catheter-based radiofrequency renal denervation on renal function and renal artery structure in patients with resistant hypertension.

There are no clinical studies on the effects of catheter-based radiofrequency renal denervation (RDN) on renal artery structure using 64-detector computed tomography (CT). A total of 39 patients with resistant hypertension received RDN and 38 patients received drug treatment. Mean systolic pressure and diastolic pressure in the RDN group decreased after 1, 3, 6, and 12 months of procedure (P<.05) and urinary protein level significantly decreased after 6 and 12 months (P<.05). The diameter, length, and sectional area of the renal artery; number of cases of atherosclerosis; and plaque burden of 64-detector CT renal arteriography did not change at 12 months of follow-up (P<.05), whereas the plaque burden increased significantly in the control group (P<.05). RDN significantly and persistently reduced blood pressure and decreased urinary protein excretion rate in patients with resistant hypertension and did not exhibit any adverse effect on renal function and renal artery structure.

[Effects of land use and landscape pattern on nitrogen and phosphorus exports in Lanlingxi Watershed of the Three Gorges Reservoir Area, China].

The temporal and spatial characteristics of N, P exports and effects of land use and landscape pattern on N, P exports were analyzed in the Lanlingxi Watershed of the Three Gorges Reservoir Area. The results showed that the TN, TP and NO3(-) -N were mainly generated by non-wood forest, the N, P exports in flood period (June to September) were significantly higher than the non-flood period (January to May). The NH4(+) -N export was derived from the residential area in the non-flood period, while from non-wood forest in the flood period. In addition, the performance of samples N, P exports with forest distributed were lower in both two periods. Also, the proportion of forest significantly negatively correlated with NO3(-) -N, TP in the non-flood period and TN, TP in the flood period. The residential area proportion notably positively correlated with NO3(-) -N, TN in non-flood period and NO3(-) -N, TN, TP in the flood period. The non-wood forest proportion also significantly positively correlated with NH4(+) -N, TN in the flood period. Moreover, PD closely positively correlated with N exports in non-flood period, with NO3(-) -N, NH4(+) -N in flood period. The CONT index strongly negatively correlated with N exports in flood period and TP in non-flood period. However, the proportions of farmland, unused land and the indices of ED were relatively weakened with N, P exports in both periods, while SHMN and water proportion did not show any positive or negative correlation. Moreover, the regression fitting degree of NH4(+)-N was superior to NO3(-) -N, TN and TP with the adjust R2 of 0.885 and 0.969 in two periods, while the regression relation was better than that of non-flood period. The result of redundancy analysis further demonstrated that the landscape fragmentation caused by patches types of different land uses could better explain impacts on the exports of nitrogen and phosphorus. The two canonical axes accumulated explained the 90% proportion of the variables and the highest contribution was PD, which was an important indicator for watershed water quality assessment and prediction.

[Research progress on remote sensing of ecological and environmental changes in the Three Gorges Reservoir area, China].

The Three Gorges Reservoir area (TGR area) , one of the most sensitive ecological zones in China, has dramatically changes in ecosystem configurations and services driven by the Three Gorges Engineering Project and its related human activities. Thus, understanding the dynamics of ecosystem configurations, ecological processes and ecosystem services is an attractive and critical issue to promote regional ecological security of the TGR area. The remote sensing of environment is a promising approach to the target and is thus increasingly applied to and ecosystem dynamics of the TGR area on mid- and macro-scales. However, current researches often showed controversial results in ecological and environmental changes in the TGR area due to the differences in remote sensing data, scale, and land-use/cover classification. Due to the complexity of ecological configurations and human activities, challenges still exist in the remote-sensing based research of ecological and environmental changes in the TGR area. The purpose of this review was to summarize the research advances in remote sensing of ecological and environmental changes in the TGR area. The status, challenges and trends of ecological and environmental remote-sensing in the TGR area were further discussed and concluded in the aspect of land-use/land-cover, vegetation dynamics, soil and water security, ecosystem services, ecosystem health and its management. The further researches on the remote sensing of ecological and environmental changes were proposed to improve the ecosystem management of the TGR area.

[Characteristics of nutrient loss of Lanlingxi watershed in the Three Gorges Reservoir area].

The water flow velocity of part of the tributaries in the Three Gorges Reservoir area has become slower after the water storage period, and agricultural non-point source pollution (AGNPS) is an urgent problem to be solved. Based on a closed catchment of Lanlingxi watershed, the process and the load of nitrogen and phosphorus loss were monitored, and the different ways of nitrogen (N) and phosphorus (P) loss under typical rainfall conditions in watershed scale were compared. The results showed that: (1) The concentration of total nitrogen (TN) gradually decreased with the increasing runoff, and slowly increased after the rain stopped, while the total phosphorus (TP) was contrary to that of TN; (2) The TN loss process had a close relation with rainfall, as TP loss was influenced by the rainfall intensity. N loss was mainly in the form of dissolvable nitrogen, while particle phosphorus was the dominant form for P loss. (3) Surface runoff was the important way of nutrient loss, as interflow greatly influenced the N loss; (4) Various forms of N and P loss showed a significant linear relationship with runoff. (5) The annual TP loss was 28.94 kg x (a x km)(-2) and TN loss was 1040.41 kg x (a x km2)(-1) in this watershed.

[Nitrogen and phosphorus loss in different land use types and its response to environmental factors in the Three Gorges Reservoir area].

The control of agricultural non-point source pollution (AGNPS) is an urgent problem to be solved for the ecological environment construction in the Three Gorges Reservoir Area. We analyzed the nitrogen (N) and phosphorus (P) loss and its response to environmental factors through monitoring the nutrient loss in different land use types after returning farmland to forest. The results showed that: 1) The variability of nutrient concentration loss was strong in different land use types under different rainfall conditions, and the variability in the concentration of available nutrient was much higher than that of total nutrient; 2) Compared to farmland, the annual phosphorus loss of different land use types was reduced by 84.53% - 91.61% after returning farmland to forest; the reduction of annual nitrogen loss was not significant except Chinese chestnut forest (Castanea mollissima) and arbor forest, and the nitrogen loss was much higher than the phosphorus loss in all land use types; 3) The particle phosphorus and nitrate nitrogen (NO3(-)-N) were the main forms of the phosphorus and nitrogen loss, respectively; 4) The nutrient loss of tea garden (Camellia sinensis) and bamboo forest (Phyllostachys pubescens) showed a good correlation with precipitation, and the correlation of phosphorus was better than that of nitrogen, but there was no significant relation with the rainfall intensity; 5) The coverage of vegetation, tree layer and litter had a great influence on the loss of total nitrogen (TN). NO3(-)-N loss was highly influenced by the ammonium nitrogen (NH4(+)-N) content in the surface soil, and P loss mainly by the total phosphorus (TP) and sand content in the soil.

[Relationships between soil nutrient contents and soil enzyme activities in Pinus massoniana stands with different ages in Three Gorges Reservoir Area].

Based on the measurements of soil nutrient contents and enzyme activities and the canonical correspondence analysis (CCA), this paper studied the relationships between soil nutrient contents and soil enzyme activities in different age Pinus massoniana stands in Three Gorges Reservoir Area. Among the test stands, mature stand had the highest contents of organic matter, total nitrogen, ammonium nitrogen, and available phosphorus in 0-20 cm soil layer, followed by middle-aged stand, and nearly-mature stand. With the increase of the stand age, soil invertase activity increased after an initial decrease, cellulase and polyphenoloxidase activities decreased gradually, while urease and peroxidase activities decreased after an initial increase. CCA analysis showed that the effects of the main soil parameters on the soil enzyme activities in the stands ranked in the sequence of total nitrogen > organic matter > pH > bulk density > ammonium nitrogen > available phosphorus. Soil invertase activity had significant positive correlations with soil organic matter, total nitrogen, and total phosphorus, while soil peroxidase activity significantly negatively correlated with soil organic matter, total nitrogen, total phosphorus, and bulk density. The soil was rich in main nutrients, invertase activity was relatively high, while peroxidase activity was relatively low. The activities of soil invertase, cellulase and peroxidase could be used as the good biological indicators in evaluating soil quality and fertility.

[Effects of litterfall and root input on soil physical and chemical properties in Pinus massoniana plantations in Three Gorges Reservoir Area, China].

An investigation was made on the soil physical and chemical properties in different-aged Pinus massoniana plantations in Three Gorges Reservoir Area under effects of litterfall and roots. The annual litter production in mature stand was 19.4% and 65.7% higher than that in nearly mature and middle-aged stands, respectively. The litter standing amount was in the sequence of mature stand > middle-aged stand > nearly mature stand, while the litter turnover coefficient was in the order of nearly mature stand (0.51) > mature stand (0.40) > middle-aged stand (0.36). The total root biomass, live root biomass, and dead root biomass were the highest in middle-aged stand, and the lowest in nearly mature stand. In middle-aged stand, soil total porosity was the highest, and soil bulk density was the lowest. Soil organic matter and total nitrogen contents were in the order of mature stand > middle-aged stand > nearly mature stand, soil nitrate nitrogen occupied a larger proportion of soil mineral N in nearly mature stand, while ammonium nitrogen accounted more in middle-aged and mature stands. In nearly mature stand, litter production was moderate but turnover coefficient was the highest, and soil nutrient contents were the lowest. In middle-aged stand, root biomass and soil total porosity were the highest, and soil bulk density were the lowest. In mature stand, root biomass was lower while soil nutrient contents were the highest. The increase of root biomass could improve soil physical properties.

[Nonpoint source pollution model, AnnAGNPS, assessment for a mixed forested watershed in Three Gorges Reservoir area].

Watershed models provide a cost-effective and efficient means of estimating the pollutant loadings entering surface waters, especially when combined with traditional water quality sampling and analyses. But there have often been questions about the accuracy or certainty of models and their predictions. The main goal of this study was to evaluate the performance of AnnAGNPS (Annualized AGricultural NonPoint Source)Pollution Model, in simulating runoff, sediment loading and nutrient loadings under Three Gorges Reservoir area. Most of model input parameters were sourced from Zigui Forest Ecology Station in Three Gorges Reservoir area, State Forestry Administration. Data year 2003 was used for calibration while data year 2004 was used for validation of the model. The whole evaluation consisted of determining the coefficient of determination (R2), Nash-Sutcliffe coefficient of efficiency (E), and the percentage volume error (VE). Results showed that the model predicted the daily runoff volume within the range of acceptable accuracy. The runoff on a daily basis was underpredicted by 5.0% with R2 of 0.93 (p < 0.05) during calibration and underpredicted by 6.7% with R2 of 0.90 (p < 0.05) during validation. But sediment loading was able to produce a moderate result. The model underpredicted the event-based sediment loading by 15.1% with R2 of 0.63 (p < 0.05) during calibration and 26.7% with R2 of 0.59 (p < 0.05) during validation. For the events of small magnitude, the model generally overpredicted sediment loading, while the opposite was true for larger events. Nitrogen loading prediction was slightly better with R2 = 0.68 (p < 0.05), and phosphorus loading performance was slightly poor with R2 = 0.65 (p < 0.05). In general, the model performs well in simulating runoff compare to sediment loading and nutrient loadings, and as a watershed management tools it can be used for Three Gorges Reservoir area conditions that with mixed types of land uses and steep slopes.