Soil-climate impacts on water cycling at the patch level

Statement of the problem These numerical experiments investigate the impacts of climate and soil physical properties including soil texture and soil depth on the cycling of water, mainly on soil water, soil tension, volumetric soil water, outflow, and leaf area index for evergreen needle-leaf forest in Chapel Hill Area.

Experimental setup (1) Dependent variables: soil water, soil tension, volumetric soil water, outflow, and leaf area index. (2) Treatments: There are six treatments in total, including two soil depths and three soil textures. For the soil depth, topsoil (0-30cm) and root-distributed profile (0-100m) are considered. For the soil textures, Sandy/silt/clay loams are considered respectively

Table 1 Treatments for Soil-climate impact on water cycling in Chapel Hill Tr. Soil Texture Depth (m) San d (%) Silt (%) Clay (%) Typical Soil Types in Chapel Hill Ch1 sandy loam Appling sandy loam Ch2 silt loam Georgeville silt loam Ch3 clay loam Hiwassee clay loam Ch4 sandy loam Appling sandy loam Ch5 silt loam Georgeville silt loam Ch6 clay loam Hiwassee clay loam

(3) Other model simulation control information in the initiation file Climate data years: ; 25 years in total, beginning with Forest type: enf (Evergreen needle-leaf forest) To write a restart worksheet: set up sim_type=1; read restart worksheet: false; and write restart worksheet: true To run daily or annual simulation: use normal simulation(sim_type=0); read restart worksheet: true; and write restart worksheet: false

Results

1. Effect of climate and soil texture on the annual total water outflow The wet years in Chapel Hill were 1989 and 1999, and the dry years were 1988 and 2001.

The maximum water outflow was occurred in 1999, which is also the wettest year in Chapel Hill There was no obvious difference in outflow between different soil textures. But soil depth affected the outflow greatly. The water outflow in top soil (0-30cm) is cm yr-1 more than those for one meter soil depth. For leaf area index, it is higher in 1m profile than 0-30 profile

Other related simulated annual results

2. Effect of climate and soil texture on the daily water cycling Simulate data of were used to analyze the effect of climate and soil physical parameters on daily water cycling, which concluded both the wet and dry years. Correlation analysis indicated that there was no significant relation between precipitation and water cycling parameters such as soil water, outflow and LAI.

Soil textures affect the water cycling greatly. For soil water and volumetric soil water, the results showed that sandy rich soil silt rich soil > clay rich soil. For the soil tension and water outflow, the result was more complex. Soil depths also have great effects on water cycling parameters. In the 0-100cm soil profile, the values of soil water, soil tension and LAI is greater than those in the top soil (0-30cm). But it has no significant effect on volumetric soil water. While the outflow in top soil was much greater than that in 0-100cm profile.

Conclusions There was no significant relationship between climate data and water cycling outputs while the highest outflow occurred in the wettest year. Water cycling parameters were affected not only by precipitation, air temperature, but also by vegetation, soil physical characters, managements and other factors; The content of sand, silt, and clay affects the physical behavior of a soil. Compared with sandy rich soil, soil water is higher in the more clay rich soils. The amount of clay affect the ability of the soil to retain moisture; Soil depths also affect the water cycling. Outflow mainly occurred in top soil.

What have I learned by this exercise? prepare the ini files and run the model; write a restart worksheet; what the parameters in the models means; how to obtain a daily or annual output; how to solve scientific problems using the model