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Monthly phytolith-occluded organic carbon (PhytOC) content in living leaves and litterfall of Moso bamboo (Phyllostachys edulis) were measured for a year. The PhytOC sequestration rate in living leaves of different months were compared with that in annual litterfall to determine the optimum sampling time of living leaves for estimating PhytOC sequestration rate of Moso bamboo. The contents of phytoliths and PhytOC in living leaves of Moso bamboos were 23.45-101.07 g·kg -1 and 0.73-1.98 g·kg -1 , respectively, with significant difference among different months. The monthly PhytOC sequestration rates of living leaves of Moso bamboo in different months ranged from 0.75 to 7.68 kg·hm -2 ·a -1 . The maximum and minimum rates of the PhytOC sequestration occurred in December and April respectively, with significant difference between them. There was no difference between the PhytOC sequestration rate in living leaves of Moso bamboos in February or December and that of litterfall in the whole year. Therefore, February or December should be the optimal month of sampling living leaves for estimating the PhytOC sequestration rate of Moso bamboo stands.

A pot experiment was conducted in a greenhouse on one-year-old clonal seedlings of Cunninghamia lanceolata. Five treatments were designed including control, conventional fertilization and three exponential fertilization treatments, with N application rates of 0, 0.5, 0.5, 1.0 and 2.0 g·seedling -1 , with N applied at 20 times at 10-day interval. The height, ground diameter, biomass, chlorophyll fluorescence and N absorption were measured after 210 days of N application. The results showed that fertilization significantly promoted the seedling height, ground diameter and biomass with the optimal values of 59.0 cm, 6.0 mm, 52.99 g·seedling -1 , in exponential fertilization treatment of 1.0 g N·seedling -1 . Chlorophyll fluorescence in exponential fertilization treatments was significantly higher than that in conventional fertilization. The photochemical quenching, PS2 electron transport rate and photochemical efficiency of PS2 in exponential fertilization treatments increased first and then decreased, with the optimal values of 0.89, 35.79 and 0.71 in 1.0 g N·seedling -1 treatment. N contents in different organs of C. lanceolata clonal seedlings were in the order of leaf > root > stem. Compared with the CK, the N contents in root, stem and leaf increased by 39.6%, 16.6% and 41.1% in the conventional fertilization treatment, and by 22.6%-81.4%, 27.3%-152.6% and 73.6%-135.5% in exponential fertilization treatments. N contents in root, stem and leaf in the exponential fertilization treatments of 1.0 and 2.0 g N·seedling -1 were significantly higher than those in the conventional fertilization treatment. P and K contents were not significantly different among the different organs. Considering the characteristics of seedling growth, chlorophyll fluorescence, the contents of N, P and K, the exponential fertilization treatment of 1.0g N· seedling -1 was the best in cultivating C. lanceolata clonal seedlings in this experiment.

Land consolidation has become a main means of achieving the intensive use of land resources, which ensures the dynamic equilibrium and requisition-compensation balance of the total cultivated land in China. However, the intensive disturbance during the land consolidation may affect the soil quality. In order to investigate the effect of land consolidation on soil microbial diversity, we studied the changes of soil microbial community diversity after 1-year and 4-year land conso-lidation by using PLFA method. The results indicated that compared with no consolidation (Z0), for land consolidation after 1a (Z1a), the soil pH value increased by 14.6%, the soil organic carbon content decreased by 65.4%, the phospholipid fatty acids content and relative abundance of all the microflora decreased significantly (P<0.05) by 43.4%-63.7% and 25.2%-53.9%, respectively, and the ratio of fungi/bacteria (F/B) decreased significantly by 35.9% (P<0.05), while the ratio of Gram-positive bacteria/Gram-negative bacteria (G + /G - ) increased significantly by 56.1%. These were significantly related to the increased pH value and the decrease of organic carbon content. The Shannon index and evenness index (E) of soil microbial diversity were significantly decreased, with significant differences observed among Z0 and Z1a, Z4a. After 4-year land consolidation, the indices characterizing soil microbial community diversity were improved compared with those after 1-year land consolidation. In summary, the land consolidation could significantly affect the composition of soil microbial communities, and decrease the stability of the soil ecosystem.

Samples of fresh leaves and leaf litter, as well as soils taken from 0-10 and 10-30 cm layers, were collected in four types of typical forest ecosystems both in subtropical (Phyllostachys pubescens, Pinus massoniana, Cycloba lanopsisglauca, and Cunninghamia lanceolata stands) and in tropical climates (Vatica mangachapoi, Musa basjoo, Heveabrasiliensis, and Acacia mangium stands) for measurement of PhytOC (phytolith-occluded organic carbon) contents. The phytoliths in both leaves and soil samples were extracted by a microwave digestion method and their PhytOC contents were determined by alkali dissolution-spectrophotometry method. It was found that, among the four types of subtropical forests, the PhytOC contents of leaves, litter and 0-10 cm soil layer were the highest in P. massoniana stand (230.24, 229.17 and 20.87 g·kg -1 ), the lowest in P. pubescens stand (30.55, 37.37, and 3.38 g·kg -1 ), and the PhytOC content of the 10-30 cm soil layer was the highest in C. glauca stand (18.54 g·kg -1 ), and the lowest in P. pubescens stand (2.90 g·kg -1 ). For the four tropical forests, A. mangium stand (377.66 g·kg -1 ) and V. mangachapoi stand (46.83 g·kg -1 ), respectively, deposited the highest and lowest contents of PhytOC in the leaves, while the highest and lowest contents of PhytOC in the litter were observed in H. brasiliensis stand (218.23 g·kg -1 ) and M. basjoo stand (27.66 g·kg -1 ), respectively. Also among the tropical forests, the highest PhytOC contents in the 0-10 cm and 10-30 cm soil layers were observed in A. mangium stand (23.84 and 24.90 g·kg -1 ), while the lowest values occurred in M. basjoo stand (3.89 and 3.93 g·kg -1 ). The PhytOC contents in transitioning from leaves to soils (0-10 cm layers) decreased by 97.4% for C. lanceolata, 94.9% for C. glauca, 90.9% for P. massoniana, and 88.9% for P. pubescens in the subtropics, and by 95.9% for H. brasiliensis, 93.7% for A. mangium, 93.3% for M. basjoo, 63.7% for V. mangachapoi in the tropics. There was no significant difference in PhytOC contents between leaves and litter for the following five forest types: P. pubescens, P. massoniana, C. lanceolata, V. mangachapoi and H. brasiliensis. However, significantly higher PhytOC contents in leaves than in litters were measured in C. glauca, M. basjoo, and A. mangium. The findings that significantly lower PhytOC contents occurred in soils than in fresh leaves and leaf litter regardless of type of forest ecosystem suggested that phytolith was not stable during the pathway from plants to soil via the forest litter.

Soil CO2 effluxes in natural broad-leaved forest and the conversed Chinese fir plantation in Linglong Mountains Scenic of Zhejiang Province were evaluated by using static closed chamber and gas chromatography method. The results showed that soil CO2 efflux showed consistent seasonal dynamics in natural broad-leaved forest and Chinese fir plantation, with the maximums observed in summer and autumn, the minimums in winter and spring. Soil CO2 effluxes were 20.0-111.3 and 4.1-118.6 mg C . m-2 . h-1 in natural broad-leaved forest and Chinese fir plantation, respectively. The cumulative soil CO2 emission of natural broad-leaved forest (16.46 t CO2 . hm-2 . a-1) was significantly higher than that of Chinese fir plantation (11.99 t CO2 . hm-2 . a-1). Soil moisture did not affect soil CO2 efflux. There was a significant relationship between soil CO2 efflux and soil temperature at 5 cm depth. There was no significant relationship between soil CO2 efflux of natural broad-leaved forest and water soluble organic carbon content, while water soluble organic carbon content affected significantly soil CO2 efflux in Chinese fir plantation. Converting the natural broad-leaved forest to Chinese fir plantation reduced soil CO2 efflux significantly but improved the sensitivity of soil respiration to environmental factors.

CO2, N2O and CH4 are important greenhouse gases, and soils in forest ecosystems are their important sources. Carya cathayensis is a unique tree species with seeds used for high-grade dry fruit and oil production. Understory vegetation management plays an important role in soil greenhouse gases emission of Carya cathayensis stands. A one-year in situ experiment was conducted to study the effects of understory removal on soil CO2, N2O and CH4 emissions in C. cathayensis plantation by closed static chamber technique and gas chromatography method. Soil CO2 flux had a similar seasonal trend in the understory removal and preservation treatments, which was high in summer and autumn, and low in winter and spring. N2O emission occurred mainly in summer, while CH4 emission showed no seasonal trend. Understory removal significantly decreased soil CO, emission, increased N2O emission and CH4 uptake, but had no significant effect on soil water soluble organic carbon and microbial biomass carbon. The global warming potential of soil greenhouse gases emitted in the understory removal. treatment was 15.12 t CO2-e . hm-2 a-1, which was significantly lower than that in understory preservation treatment (17.04 t CO2-e . hm-2 . a-1).

The change characteristics of soil organic carbon and microbial function diversity in Chinese hickory Carya cathayensis stands with different intensive-management durations (5, 10, 15 and 20 years) were studied. The results showed that soil total organic carbon (TOC), microbial biomass carbon (MBC), water-soluble organic carbon (WSOC) decreased significantly, while the stability of soil C pool increased significantly after the conversion from evergreen and deciduous broadleaf forest to intensively-managed forest (IMF). TOC, MBC and WSOC in the hickory forest soil decreased by 28.4%, 34.1% and 53.3% with 5-year intensive management, and by 38.6%, 48.9% and 64.1% with 20-year intensive management, respectively. The proportions of carboxyl C, phenolic C and aromatic C in the hickory forest soil all increased significantly, and the aromaticity of soil organic C increased by 23.0%. Soil microbial functional diversity decreased greatly af- ter intensive management of Chinese hickory forest. Significant differences in average well color development (AWCD) were found between the 0- and 5-year treatments and the 10-, 15- and 20- year treatments. The microbial diversity indexes (H) and evenness indexes (E) in the 0- and 5-year treatments were much greater than in the 10- and 20-year treatments. Correlation analysis showed that there were significant correlations among soil TOC, WSOC, MBC, AWCD, H and E.

To investigate the effects of different forest stands in subtropical China on the communities of soil ammonia-oxidizing microorganisms, we characterized the abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB), and the community structure of AOA in soils under stands of broad-leaved (BF) , Chinese fir (CF) , Pinus massoniana (PF) and moso bamboo (MB) forests using real-time quantitative PCR and denaturing gradient gel electrophoresis (DGGE). The results showed that the AOA gene copy numbers (1.62 x 10(6)-1.88 x 10(7) per gram of dry soil) were significantly higher than those of AOB genes (2.41 x 10(5)-4.36 x 10(5) per gram of dry soil). Significantly higher soil AOA abundance was detected in the MB than that in the CF (P < 0.05), and the latter was significantly higher than that in the BF and PF soils (P < 0.05). There were no significant differences in the soil AOB abundance among the four forest stands. As indicated by DGGE pattern, soil AOA species varied among the four forest stands. There was a difference in the soil AOA communities between the CF and MB stands. The AOA demonstrated a competitive advantage over the AOB in the soils under these major subtropical forests. Soil pH, concentrations of soil available potassium and organic carbon as well as the forest type were the main factors that influence the variation of AOA community structure and diversity.

The samples of different age (1-4 years old) Phyllostachys praecox plants and their organs (leaf, branch, and culm) were collected from their main production area in Lin' an County, Zhejiang Province of East China to study the contents and the uptake and accumulation characteristics of silicon and other nutritional elements, as well as the interrelations between Si and other nutrient elements. In the P. praecox plants, the C content in aboveground part was in the order of culm > branch> leaf, whereas the Si, N, P, K, Ca, Mg, Al, Fe and Mn contents were in the order of leaf > branch > culm. Mn was mainly accumulated in leaf, while the other nine nutrient elements were mainly accumulated in the culm of 1-year old plants. The average Si content in the aboveground part of 3-4 year old plants was 13.66 g x kg(-1), suggesting that P. praecox belonged to Si accumulation plant. The leaf N, P, K, and Mg contents decreased, while the C, Al, and Mn contents increased with increasing plant age. The Si uptake by the aboveground part was mainly occurred in the second year (57.1%), while the N and K uptake was mainly in the first two years (67.7% - 93.7%). Thereafter, the N and K flowed out from the aboveground part, with the outflow rates reached 19.1% - 39.1% of the total accumulated amounts. The Si in P. praecox was significantly correlated with Ca, Al, and Mn, and negatively correlated with N, P, K, and Mg.

To investigate the effects of the conversion from native shrub forest (NF) to Chinese chestnut plantation (CP) on the soil carbon (C) and nitrogen (N) pools, soil samples were collected from the adjacent NF and CP in Anji County of Zhejiang Province, with their water-soluble organic C (WSOC), microbial biomass C (MBC), readily oxidizable C (ROC), water-soluble organic N (WSON), and microbial biomass N (MBN) determined. The spectral characteristics of soil organic C were also determined by using nuclear magnetic resonance (NMR) technique. After the conversion from NF to CP, the soil alkalyzable N, available phosphorus, and available potassium contents increased significantly, while the soil WSOC, MBC, ROC, WSON, and MBN were in adverse. The soil organic C in both NF and CP was dominated by alkyl C and O-alkyl C, but the proportions of O-alkyl C and carbonyl C in soil organic C decreased while the proportions of alkyl C and aromatic C as well as the alkyl C/O-alkyl C ratio and the aromaticity of soil organic C all increased significantly after the conversion from NF to CP, indicating that this conversion increased the stability of soil organic C pool significantly. In conclusion, the conversion from NF to CP and the intensive management of CP decreased the contents of soil labile C and soil N but increased the stability of soil C pool significantly.