Land degradation

Soil Bacterial Community in Association with Land Degradation...317... 

Values of a soil fertility index (SFI, Moran et al. 2000) or a soil evaluation factor (SEF, Lu et al. 2002) were calculated to quantify the intensity of the land degradation. SFI showed the applicability to measuring soil quality and to predicting succession rate of secondaiy tropical forest (Moran et al. 2000). The following equation was used to calculate SFI values (Lu et al. 2002). 

Physico-chemical characteristics of the soils were summarized in Table 1. The values were comparable to that described in the previous reports about the SERS (Doi and Sakurai 2003 Doi et al. 2004 Sakurai et al. 1998). The one-way ANOVA indicated that most of the soil variables significantly reflected the land degradation with high values of bulk density, sand content and exchangeable acidity, and low values of moisture content, pH, OM, base (K, Ca, Mg) contents, EC, CEC, base saturation rate, TN and TC contents, available phosphorus and MPN on the glucose medium with no antibiotics. These results also told that the human activities induced several soil environmental gradients. 

Antibiotic resistance profiles of the bacterial communities reflected the effects of deforestation and the land degradation (Fig. 2). The degradation was significant (p=0.05) as a source of variation for the numbers of soil bacterial cells resistant to lasalocid, penicillin, spectinomycin and trimethoprim, and marginally significant (0.50 Significant differences between two average values were observed for some antibiotics. When compared with the BG soil bacterial community, the DEF soil bacterial community had more bacterial cells resistant to dapson, kanamycin, lasalocid, nafcillin, penicillin, spectinomycin, streptomycin and trimethoprim. 

PCA of the Antibiotic Resistance Profiles to Find PCs that Explain the Land Degradation... 

Multiple regression analysis between the SFI or the SEF values and the PC scores gave the following formulae that describe the land degradation gradient based on the antibiotic resistance profiles. 

The first RDA ordination axis scored an eigenvalue of 0.493, while the first CCA axis 0.003. This contrast indicated that the linear model fitted well, but the unimodal model fitted poorly. Thus, only the RDA ordination diagram was shown in Fig. 4. The diagram visualizes the land degradation gradient. Again, the DEF and the GB soils were shown to be the extremes, while the DDF soil the intermediate. Relationships between the changes in... 

The low eigenvalue for the CCA axis indicated few unimodal patterns against the land degradation gradient for the relative abundance of... 

Doi R (2004) Soil bacterial community profiling with Biolog kinetic and antibiotic resistance most probable number approaches showed multidimensionality of land degradation. Int J Agri Bio 6 284-288 Doi R, Sakurai K (2003) Soil environmental factors relating to diversity of culturable soil bacterial communities in the Sakaerat Environmental Research Station, Thailand. Tropics 12 185-200... 

Doi R, Sakurai K (2004) Principal components derived from soil physicochemical data explained a land degradation gradient, and suggested the applicability of new indexes for estimation of soil productivity in the Sakaerat Environmental Research Station, Thailand. Int J Sustain Dev World Ecol... 

Eden MJ, Parry JT (1996) Land degradation in the tropics environmental and policy issues. Global Development and the Environment series, Pinter, London, UK... 

Sterk G, Lopez MV, Arrue JL (1999) Saltation transport on a silt loam soil in northeast Spain. Land Degrad Dev 10 545-554... 

Koch M (2000) Geological controls of land degradation as detected by remote sensing a case study in Los Monegros, north-east Spain. Int J Remote Sens 21 457 173... 

Blaikie, E, and H. Brookfield (1987). Land degradation and society. New York Rout-ledge, 68. PAUL NOTES original publication by Methuen, reprinted by Routledge same year. The page numbers are from the Routledge edition. 

Blaikie, P, and H. Brookfield (1987). Land degradation and society. New York Routledge, 35. 

Barbier, E. B. (2000) The economic linkages between rural poverty and land degradation some evidence from Africa.- Journal of Agriculture, Ecosystems and Environment 82, 355-370. 

Qadir, M. Ghafoor, A. and G. Murtaza (2000) Amelioration strategies for saline soils a review.- Land degradation and development 11, 501-521. 

To maintain soil fertility and productivity and prevent land degradation, nutrients taken up by crops must be replenished through the application of fertilizers. The use of fertilizer results in many benefits to producers, consumers, and the environment, starting with... 

Sevink, J., J. M. Verstraten, and J. Jongejans. 1998. The relevance of humus forms for land degradation in Mediterranean mountainous areas. Geomorphology 23 285-292. 

Pimentel, D., Terhune, E.C., Dyson-Hudson, R., Rochereau, S., Samis, R., Smith, E.A., Denman, D., Reifschneider, D. and Shepard, M., 1976. Land degradation effects on food and energy resources. Science, 194 149—155. 

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