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Li Y.,Chinese Academy of Agricultural Sciences | Yu H.Q.,Chinese Academy of Agricultural Sciences | Zhou N.,Chinese Academy of Agricultural Sciences | Tian G.,Environmental Monitoring and Research Division | And 3 more authors.
Plant and Soil

Aims: The forestland understory vegetation reduces concentrated overland flow through infiltration improvement by roots and raindrop interception by surface cover. However, little has been done to quantify the linkages between understory vegetation cover, roots, and channel erosion, and such information can help assessing the role of the reforestation in soil erosion control. In this study, we evaluated the relationships between channel density, root density, and vegetation cover in forested hillslopes of southwestern China.Methods: Twelve locations (four slopes and three positions) of forested hillslopes with a wide range of understory degradation due to litterfall extraction and livestock grazing were selected for the study. Channel density as a measure of rill and (small) gully erosion, root density of different diameter classes, and vegetation cover of all types were determined using field measuring, soil coring and the line transect method, respectively. Soil loss rates were estimated using the caesium-137 (137Cs) technique.Results: Rills (depth < 0.3 m) with a width of 0.05–0.1 m were the dominate channel erosion in all hillslopes with understory-degradation, and small gullies (depth > 0.3 m) with a width 0.5–1.0 m were found at the locations of hillslopes with high understory-degradation. Channel density and soil loss rate increased with the increase in understory-degradation in the forested hillslopes. Simple correlation analysis indicated that channel density was negatively correlated with fine root density (diameter < 1 mm and 1–2 mm) and grass and shrub covers, but not with coarse roots (diam. 2–5 mm and 5–10 mm) and mulch and tree covers. The principal component regression revealed fine root density (diam. <1 mm), shrub and grass covers were the most important predictors for channel density in the forested hillslopes. Tree cover, mulch cover and coarse root density were found to have much less influence on channel density. For the model established from this study using principle component regression, vegetation variables could explain 82 % variance of channel density.Conclusions: We conclude that fine root density and grass and shrub covers are the most important factors in controlling soil erosions in forested hillslopes. These parameters should be taken into consideration in assessing reforestation for soil erosion control in hilly areas such as that in southwestern China or other similar regions. © 2014, The Author(s). Source

Chen T.-H.,Taiwan Forestry Research Institute | Tian G.,Environmental Monitoring and Research Division | Chiu C.-Y.,Academia Sinica, Taiwan
Applied Soil Ecology

Moso bamboo (Phyllostachys edulis) is the fastest growing vegetation in the world, and it is widely distributed from low- to medium-elevation mountains in Taiwan. To understand how microbial activity and microbial community change with the elevation in bamboo plantations, we investigated soil microbial biomass, enzymes, and composition of bacteria and fungi in five moso bamboo plantations along an elevation gradient (600, 800, 1000, 1200 and 1400m asl) in central Taiwan. The soil microbial community structure was determined by analysis of the phospholipid-derived fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) profiles. The soil microbial biomass C (Cmic) and biomass N (Nmic) increased along the elevation gradient. Similarly, the activities of soil enzymes, such as cellulase, xylanase and urease, increased along the elevation gradient. The proportion of PLFAs that were attributed to total bacteria, Gram-positive (G+) bacteria, and Gram-negative (G-) bacteria also increased with the increase in elevation. However, the ratio of G+/G- bacteria decreased along the elevation increase, indicating that bamboo plantations at low elevations (600m, 800m and 1000m) contained less active soil organic matter than those at high elevations (1200m and 1400m). The results coincided with the availability of labile organic matter in bamboo plantation soils with lower Cmic/Corg and Nmic/Ntot in lower compared to higher elevations. Principle component analysis of PLFA content separated the low-elevation plantations from the high-elevation plantations. The DGGE analysis revealed that changes in both bacterial and fungal community structures were associated with the elevation gradient. Temperature changes along the elevation gradient contributed to variations in the soil microbial community in the bamboo plantations. © 2015 Elsevier B.V.. Source

Huang C.-Y.,Academia Sinica, Taiwan | Jien S.-H.,National Pingtung University of Science and Technology | Chen T.-H.,Taiwan Forestry Research Institute | Tian G.,Environmental Monitoring and Research Division | Chiu C.-Y.,Academia Sinica, Taiwan
Journal of Soils and Sediments

Purpose: Moso bamboo (Phyllostachys edulis), an important economic crop, is distributed from low- to medium-elevation mountains in Taiwan. Bamboo is a fast-growing herbaceous species with an extensive rhizome structure. With the hypothesis that the characteristics of soil organic matter and microbes might change after long-term bamboo plantation, we investigated different fractions of organic C and N as well as soil microbial biomass and activities in five moso bamboo plantations along an elevation gradient in Central Taiwan. Materials and methods: Five soil samples (top 10 cm of soil) were collected from each bamboo plantation (600, 800, 1,000, 1,200, and 1,400 m above sea level (asl)) in January 2011. Soil was processed and analyzed for soil total C and N contents, biologically available C, potentially mineralizable N, soil microbial biomass and soil respiration (CO2). Two extraction methods (2 M KCl and hot-water extraction) were used to estimate soil soluble organic C and N (SbOC and SbON) and soil inorganic N (NH4 + and NO3 -) concentrations to evaluate the relationship with soil organic matter and microbe characteristics in bamboo plantations. Results and discussion: Soil total C and N contents as well as soil microbial biomass and soil respiration (CO2) of the bamboo plantations increased along the elevation gradient. Temperature changes along elevation contributed to such variations observed among the selected bamboo plantations. The SbON in hot-water extracts was highest in the 1,200-m plantation, then in the 1,400-m plantation, and lowest in the low-elevation plantations (600, 800, and 1,000 m). However, SbON in 2 M KCl extracts did not differ by elevation. The SbON was strongly correlated with soil total N in both 2 M KCl and hot-water extracts, but only SbON in hot-water extracts was strongly correlated with microbial biomass N and potentially mineralizable N. SbOC was strongly correlated with soil total C content, microbial biomass C, and biologically available C in both 2 M KCl and hot-water extracts. Conclusions: Soil total C and N, SbOC and SbON, and microbial biomass characteristics increased in the moso bamboo plantations with increasing elevation. No altitudinal difference in specific soil respiration (CO2) rate suggested that the enhanced potentially mineralizable N and soil respiration (CO2) in the high-elevation plantations were associated with increased microbial biomass rather than microbial activities. © 2014 Springer-Verlag Berlin Heidelberg. Source

Chung T.-L.,Academia Sinica, Taiwan | Chen J.-S.,Yung Ta Institute of Technology and Commerce | Chiu C.-Y.,Academia Sinica, Taiwan | Tian G.,Environmental Monitoring and Research Division
Journal of Forest Research

We investigated soil organic matter in a forest of natural Hinoki cypress (Chamaecyparis obtusa) under perhumid weather conditions in north central Taiwan. Humic substances along the transect from the summit and footslope to lakeshore were characterized by use of solid-state cross-polarization, magic-angle-spinning 13C nuclear magnetic resonance spectroscopy (CP/MAS 13C-NMR). The major components of soil organic carbon in whole soil and humic substances were alkyl-C, O-alkyl-C, and di-O-alkyl-C, ranging from 60.6% to 80.7%, then aromatic-C, 7.5% to 9.8%. The degree of humification of soil organic matter, both O-alkyl-C/alkyl-C ratio and aromaticity, decreased slightly from the summit to lakeshore. The content of functional groups of polar and acidic groups, including O-alkyl-C, di-O-alkyl-C, and carboxyl-C, corresponded with the topographical effect, increasing slightly from the summit to lakeshore. However, the relatively low degree of humification in soils of this perhumid forest and low aromaticity were due to high precipitation and acidity, which appeared to hinder organic matter decomposition with topography change. © 2011 The Japanese Forest Society and Springer. Source

Chiu C.Y.,Academia Sinica, Taiwan | Tian G.,Environmental Monitoring and Research Division
Applied Soil Ecology

We used NMR spectroscopy to characterize humid acids extracted from soils that had received long-term application of 2 levels of biosolids to evaluate the soil organic matter (SOM) stability in biosolids-amended soils. The study also quantified fulvic acids (FAs), humic acids (HAs) and Fe/Al oxides. The soils were collected in 2004 from 7 fields, in Fulton County, southwestern Illinois, which received biosolids at a cumulative rate of 0 (control), 554 (low biosolids) and 1,066 (high biosolids)Mgha-1. The application of biosolids increased both FA and HA contents, but biosolids-amended soil and control soil did not differ in FA/HA ratio. Biosolids application had no effect on water-soluble organic carbon content. Biosolids application increased the presence of Fe/Al in the SOM complex and lowered its C/Fe and C/Al ratios. 13C NMR spectra showed increased alkyl C and decreased aromatic C content in soil HAs with the application of biosolids, and the extent of such changes was higher with high than low biosolids treatment. Under biosolids application, the soil HAs' C structure shifts from O-alkyl-dominant to alkyl-dominant. Biosolids application does not decrease SOM stability but rather increases the stability of soil humic substances. © 2011 Elsevier B.V. Source

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