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Jia G.-M.,China Three Gorges University | Zhang B.-L.,China Three Gorges University | Niu J.-T.,China Three Gorges University | Wang L.-M.,Forestry Bureau of Zigui County | Chen F.-Q.,China Three Gorges University
Agroforestry Systems | Year: 2015

Rhizosphere carbon sequestration plays a crucial role in soil carbon dynamics. Little information is available on the dynamics of rhizosphere soil labile organic carbon fractions compared with bulk soil at different citrus stand age. Two replicate sites of three stand ages (10-, 20-, and 30-year) of citrus in the Three Gorges Reservoir area of China were studied. The results showed that rhizosphere soil organic carbon has an increases of 18.76 % under 20-year stand and 11.09 % under 30-year stand compared with bulk soil (P < 0.05), respectively. The dissolved organic C of rhizosphere soil was 31.32, 19.57 and 31.81 % higher compared with bulk soil under 10-, 20- to 30-year stands (P < 0.05), respectively, whereas readily oxidizable organic C (ROC) was 50.47, 70, and 64.54 % higher (P < 0.05). Microbial biomass (MBC) and water-soluble carbohydrate (WSCh) had no significant difference between rhizosphere and bulk soils in the 10- and 20-year stands, whereas a 9.88 % lower for MBC and a 36.47 % higher for WSCh in rhizosphere soil compared with bulk soil under 30-year stand were found (P < 0.05). Rhizosphere soil respiration showed a significantly negative relationship with ROC (r = 0.51, P < 0.05), WSCh (r = 0.60, P < 0.01) and MBC (r = 0.68, P < 0.01). The effect of the citrus rhizosphere on measured soil labile organic carbon fractions differed for each citrus stand age. © 2015 Springer Science+Business Media Dordrecht

Lei L.,Chinese Academy of Forestry | Lei L.,Chongqing Three Gorges University | Xiao W.-F.,Chinese Academy of Forestry | Xiao W.-F.,Chongqing Three Gorges University | And 7 more authors.
Forest Research | Year: 2015

Aerially seeded Pinus massoniana forest in the Three Gorges Reservoir area with different management treatments, including shrubs-cutting plus residue removal, harvest I (cutting intensity 15%, stem-only harvesting without residue removal), harvest II (cutting intensity 70%, harvest type as harvest I) and the control, were surveyed to measure the total soil respiration rates over a year by using LI-8100 system. The influence of various forest managements on soil respiration was discussed and the reasons causing the variability of soil respiration were analyzed. The results showed that: the annual soil respiration of forests with different treatments was1.82±0.07 μmol·m-2 s-1 (shrubs-cutting), 2.18±0.05 μmol·m-2 s-1 (control), 2.37±0.07 μmol·m-2s-1 (harvest I), and 2.86±0.1 μmol·m-2s-1(harvest II). The harvest intensity was positively related to soil respiration increment; soil respiration of all the harvest treatment reached the maximum in July and August. High intensity improved the soil temperature and moisture. The temperature sensitivity indexes of the control, shrubs-cutting, harvest I, and harvest II were 2.18±1.09, 1.65±0.07, 2.20 ±0.09 and 2.36±0.09 respectively. ©, 2015, Chinese Academy of Forestry. All right reserved.

Ge X.-G.,Chinese Academy of Forestry | Xiao W.-F.,Chinese Academy of Forestry | Zeng L.-X.,Chinese Academy of Forestry | Huang Z.-L.,Chinese Academy of Forestry | And 2 more authors.
Chinese Journal of Applied Ecology | Year: 2012

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.

Tian Y.-W.,Henan University of Science and Technology | Tian Y.-W.,Chinese Academy of Forestry | Huang Z.-L.,Chinese Academy of Forestry | Xiao W.-F.,Chinese Academy of Forestry | And 2 more authors.
Chinese Journal of Ecology | Year: 2015

Soil is one of the largest pools of terrestrial organic carbon. Land-use types affect not only the storage but also the depth distribution pattern of soil organic carbon (SOC), which plays important roles in global climatic change. The SOC depth distribution and its influencing factors in Lanlingxi watershed in Three Gorges Reservoir were analyzed. The results showed that land-use types significantly affected the SOC depth distribution. The SOC densities in 0-20 cm layer averaged at 8.47, 5.90, 4.65, and 2.64 kg·m-2 for forests, grasslands, shrub lands, and croplands, respectively, and the SOC densities in the 0-100 cm were 8.47, 5.90, 4.65, and 2.64 kg·m-2 respectively. The percentage of SOC in 0-20 cm layer (relative to the 0-100 cm) averaged at 69.8%, 57.6%, 50.8% and 36.2% for forests, grasslands, shrub lands and croplands, respectively. With increasing soil depth, SOC density decreased rapidly, and the decline rate was fastest in forests. The forests had a shallower SOC depth distribution. On the contrary, grasslands and shrub lands decreased slowly with soil depth, and they had a deeper SOC depth distribution. Land-use type and altitude significantly affected SOC densities in top layer (0-20 cm), but had no obvious effect on that in the deeper layers (>40 cm). Soil mechanical composition had a little effect on SOC density of surface layer (0-20 cm), but had a significant effect in deeper layers (>40 cm). The soil carbon storage was underestimated when SOC in 0-100 cm layer was considered. SOC density would be increased by 6.2%-16.5% in the study watershed with SOC storage in 0-150 cm layer being considered. © 2015, editorial Board of Chinese Journal of Ecology. All rights reserved.

Tian Y.W.,Henan University of Science and Technology | Tian Y.W.,Chinese Academy of Forestry | Zeng L.X.,Chinese Academy of Forestry | Huang Z.L.,Chinese Academy of Forestry | And 2 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2015

The pool of soil organic carbon (SOC) in a forest forms an important component in the global carbon (C) cycle. SOC plays an important role in enhancing forest productivity and mitigating the net rate of global greenhouse gas emissions. The risk of global warming has caught the attention of the scientific community as it relates to SOC stocks in forest ecosystems. The precise measurement of SOC stocks and verification of the amount of C sequestered in the soil are critical factors for the implementation of C trading programs. SOC in mineral soils generally decreases with depth; however, this decrease is non-linear and has been frequently modeled as an exponential function. We selected four forest types (boreal forest, temperate deciduous forest, subtropical mixed forest, and tropical evergreen broadleaved forest) and analyzed theexponential function for SOC mass density. We established an SOC database for layers of the soil profile by measuring the SOC in typical areas in the four forest biomes. The depth distribution models for the mass density of SOC were established by a typical sampling method. The model was calibrated using 60% of the data of the profiles, and 40% of the data was used for validation purposes. The entire evaluation for the results of model simulation consisted of determining the coefficient of determination (R2), Nash-Sutcliffe coefficient of efficiency (E), and the percentage error (PE). Next, the depth distribution models evaluated here were used to simulate the distribution of SOC deeper into the soil profile. The results showed that the simulation values for the depth distribution models of the four forest biomes and the observed values were relatively consistent. The average values of R2, E, and absolute PE were 0.88, 0.74, and 6.95%, respectively. The model simulations had a relatively high capacity (E > 0.6), and the PE of the model was simulated within a range with acceptable accuracy (PE < ±15%). The model could be used to simulate the depth distribution of forest soil organic carbon. Second, the boreal coniferous forest had a much higher density of SOC in the 0—20 cm layer than those of the tropical deciduous forest and the two other forest types. In contrast, the SOC densities in other layers of boreal coniferous forest were lower, while those of the tropical deciduous forest were higher. The regional SOC densities were lower when SOC densities in the 0—100 cm soil layers were used to characterize the regional SOC density. When compared with the SOC densities in the range of 0—200 cm in the soil profile, the SOC densities in the 0—100 cm soil layer were about 21.8% lower than the overall density. Any error in this calculation may be greater and more prominent in regions with high temperatures and precipitation rates. For rainfall events of a small magnitude, the model generally over-estimated mass density at the bottom of the soil profile, while the opposite was true; that is, for regions with large amounts of rainfall, the model generally under- estimated the surface SOC density. In general, the model performs well at simulating the depth distribution of SOC, and it can be used as a forest SOC management tool to simulate the depth distribution of SOC in some regions. © 2005, Ecological Society of China. All rights reserved.

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