scholarly journals Soil Organic Carbon Shapes AMF Communities in Soils and Roots of Cynodon dactylon under Anti-Seasonal Drying-Wetting Cycles

Diversity ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 197 ◽  
Author(s):  
Xie Luo ◽  
Xinhua He ◽  
Xiumei Luo ◽  
Yining Liu ◽  
Junqi Wang ◽  
...  

Anti-seasonal drying-wetting cycles since 2010 have substantially altered its soil and vegetation status in the drawdown zone of China’s Three Gorges Reservoir (TGR). Such alternations may thus affect the composition and functioning of soil microbial communities, including the beneficial arbuscular mycorrhizal fungi (AMF), which enhance plant performance. Moreover, limited information is available if AMF communities are different in soils and roots, particularly under contrasting land-use changes. By combining the Illumina Miseq sequencing with bioinformatics analyses, AMF communities in both rhizosphere soils and roots of a stoloniferous and rhizomatous C4 perennial of Cynodon dactylon were characterized under three land-use types: (1) crop cultivated, (2) non-cultivated non-disturbed, and (3) disturbed non-cultivated land. A total of 35 and 26 AMF taxa were respectively detected from C. dactylon rhizosphere soils and roots from these three land-use types, which had endured four anti-seasonal drying/summer-wetting/winter cycles. Contrasting differentiations in the AMF community composition and structure were displayed in the C. dactylon rhizosphere soils and roots, and between land-use types. Nonmetric multidimensional scaling analyses revealed that AMF communities significantly correlated to soil organic carbon in the rhizosphere soils and roots of C. dactylon, to land-use types only in rhizosphere soils, whereas to soil moisture only in roots. Our results highlight the effects of soil nutrients and land-use changes on AMF community composition and diversity under the canopy of C. dactylon in TGR. The identified dominant AMF taxa can be employed to vegetation restoration in such degraded habitats globally.

2013 ◽  
Vol 10 (11) ◽  
pp. 18359-18406 ◽  
Author(s):  
Y. Yagasaki ◽  
Y. Shirato

Abstract. In order to develop a system to estimate a country-scale soil organic carbon stock change (SCSC) in agricultural lands in Japan that enables to take account effect of land-use changes, climate, different agricultural activity and nature of soils, a spatially-explicit model simulation system using Rothamsted Carbon Model (RothC) integrated with spatial and temporal inventories was developed. Future scenarios on agricultural activity and land-use change were prepared, in addition to future climate projections by global climate models, with purposely selecting rather exaggerated and contrasting set of scenarios to assess system's sensitivity as well as to better factor out direct human influence in the SCSC accounting. Simulation was run from year 1970 to 2008, and to year 2020, with historical inventories and future scenarios involving target set in agricultural policy, respectively, and subsequently until year 2100 with no temporal changes in land-use and agricultural activity but with varying climate to investigate course of SCSC. Results of the country-scale SCSC simulation have indicated that conversion of paddy fields to croplands occurred during past decades, as well as a large conversion of agricultural fields to settlements or other lands that have occurred in historical period and would continue in future, could act as main factors causing greater loss of soil organic carbon (SOC) at country-scale, with reduction organic carbon input to soils and enhancement of SOC decomposition by transition of soil environment to aerobic conditions, respectively. Scenario analysis indicated that an option to increase organic carbon input to soils with intensified rotation with suppressing conversion of agricultural lands to other land-use types could achieve reduction of CO2 emission due to SCSC in the same level as that of another option to let agricultural fields be abandoned. These results emphasize that land-use changes, especially conversion of the agricultural lands to other land-use types by abandoning or urbanization accompanied by substantial changes in the rate of organic carbon input to soils, could cause a greater or comparable influence on country-scale SCSC compared with changes in management of agricultural lands. A net-net based accounting on SCSC showed potential influence of variations in future climate on SCSC, that highlighted importance of application of process-based model for estimation of this quantity. Whereas a baseline-based accounting on SCSC was shown to have robustness over variations in future climate and effectiveness to factor out direct human-induced influence on SCSC. Validation of the system's function to estimate SCSC in agricultural lands, by comparing simulation output with data from nation-wide stationary monitoring conducted during year 1979–1998, suggested that the system has an acceptable levels of validity, though only for limited range of conditions at current stage. In addition to uncertainties in estimation of the rate of organic carbon input to soils in different land-use types at large-scale, time course of SOC sequestration, supposition on land-use change pattern in future, as well as feasibility of agricultural policy planning are considered as important factors that need to be taken account in estimation on a potential of country-scale SCSC.


2015 ◽  
Vol 7 (1) ◽  
pp. 115-145 ◽  
Author(s):  
Y. Mohawesh ◽  
A. Taimeh ◽  
F. Ziadat

Abstract. Land degradation resulting from improper land use and management is a major cause of declined productivity in the arid environment. The objectives of this study were to examine the effects of a sequence of land use changes, soil conservation measures, and the time since their implementation on the degradation of selected soil properties. The climate for the selected 105 km2 watershed varies from semi-arid sub-tropical to Mediterranean sub-humid. Land use changes were detected using aerial photographs acquired in 1953, 1978, and 2008. A total of 218 samples were collected from 40 sites in three different rainfall zones to represent different land use changes and different lengths of time since the construction of stone walls. Analyses of variance were used to test the differences between the sequences of land use changes (interchangeable sequences of forest, orchards, field crops, and range), the time since the implementation of soil conservation measures, and rainfall on the thickness of the A-horizon, soil organic carbon content, and texture. Soil organic carbon reacts actively with different combinations and sequences of land use changes. The time since stone walls were constructed showed significant impacts on soil organic carbon and the thickness of the surface horizon. The effects of changing the land use and whether the changes were associated with the construction of stone walls, varied according to the annual rainfall. The results help in understanding the effects of land use changes on land degradation processes and carbon sequestration potential and in formulating sound soil conservation plans.


2019 ◽  
pp. 1-107 ◽  
Author(s):  
Thangavel Ramesh ◽  
Nanthi S. Bolan ◽  
Mary Beth Kirkham ◽  
Hasintha Wijesekara ◽  
Manjaiah Kanchikerimath ◽  
...  

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