**6.3 The soil of the riparian buffer**

The Wilbur series (Coarse-silty, mixed, superactive, mesic Fluvaquentic Eutrudepts) consists of very deep, moderately well-drained soils that formed in silty alluvium. The mean annual temperature is about 13°C and mean annual precipitation is about 1.1 m. The typical horizon sequence is Ap (Ochric)–Bw (Cambic) – Cg. The soil series generally has redoximorphic features from 0.43 to 2 m.

The sampled pedon of the Wilbur series was in a land-graded floodplain of Williams Creek in Cape Girardeau County and cultivated to a corn (*Zea mays*) – soybean (*Glycine max*) rotation. The pedon exhibited the typical Ochric – Cambic – Cg horizon sequence. All soil horizons were silt loam. Munsell soil colors are 10YR4/3 (brown) to 10YR 4/4 (dark yellowish brown) from the Ap through the Bw horizons. The Cg horizons have 10YR5/3 (grayish brown) to 10YR5/1 (gray) and 10YR4/1 (dark gray) Munsell colors, suggesting gleyed soil conditions. The Ap and Bw horizons have weak, fine to medium, granular structures, whereas the deeper soil horizons have weak, fine to medium, subangular blocky structures.

The pH is neutral in the surface horizons and acidic to very strongly acidic in the subsurface horizons (**Table 1**). The soil organic matter content was 1.2% in the Ap horizon and 0.7 in the A horizon. The Cambic horizon's soil organic matter contents ranged from 0.6 to 0.3%, whereas the Cg horizons were 0.1%. Exchangeable calcium in the dominant exchangeable cation and the cation exchange capacity is medium in the Ochric and Cambic horizons and low in the Cg horizons. Interestingly, exchangeable sodium is more evident in the Cg horizons.



*pH in water, SOM is soil organic matter by loss on ignition. Exchangeable cations by ammonium acetate (pH 7) extraction, total acidity by BaCl2-thriethanolamine (cmol charge/kg), CEC is cation exchange capacity by ammonium acetate saturation (cmol charge/kg).*

#### **Table 1.**

*Chemical properties for a pedon of the Wilbur series.*

#### **6.4 Soil changes attributed to the installation of the riparian buffer**

Soil pH was slightly more acidic in the riparian buffer, but the difference was not significant. Similarly, nitrate-N and phosphorus concentrations were not significantly different. Conversely, soil organic matter contents, sulfate-S, and ammonium-N concentrations were significantly different. Soils in the riparian buffer had greater soil organic matter contents, averaging 3.4%, whereas the production field exhibited an average soil organic matter content of 1.7%. (**Table 2**). Similarly, sulfate-S and ammonium-N concentrations were greater in the riparian buffer (**Table 2**). The riparian buffer's greater soil organic matter content was generally attributed to both detritus (particulate soil organic matter) and humus. The riparian forest vegetation created a living root web permeating the A horizon, that most likely reduced soil erosion, strengthened the soil structure, improved infiltration, and contributed to the soil organic matter accumulation. Greater sulfate-S and ammonium-N accumulations were likely attributed to greater mineralization rates.

Riparian buffers are natural-solutions, permitting soil processes to operate without human imposed stresses. Outside of the riparian buffer, subsurface and primary tillage is required because the silt loam soils exhibit compaction because of weak soil structures. However, tillage generally degrades soil structure, exposing soil organic matter to microbial activity. Establishment of the riparian buffer supported greater organic matter incorporation in the soil, a consequence likely attributable


*Note: CV is coefficient variation, CI is the confidence interval at p = 0.5. SOM is soil organic matter, P is Bray-1 phosphorus. T-test and other statistical analysis performed using Excel.*

#### **Table 2.**

*Selected surface properties in and adjacent to the riparian buffer.*

*Soil Evolution after Riparian Buffer Installation DOI: http://dx.doi.org/10.5772/intechopen.112885*

to maintenance of the soil structures and a greater net primary production. The presence of rooting activity supports the formation of micro- and macro-aggregates that act to preserved the soil organic matter. O'Brien and Jastrow [30] isolated (i) non-aggregated material, (ii) free microaggregates, (iii) macroaggregates and (iii) microaggregates-within-macroaggregates to investigate how soil organic matter contents recover in plant community restorations. Microaggregates isolated from within macroaggregates contributed the greatest quantities of C and N to whole soil; however, the soil organic matter pools may recover over various time scales. Thus, restoration will succeed, but the time spans may be lengthy.

### **7. Conclusion**

The presented literature conclusively demonstrates that the riparian buffer design criteria is predicated on which resource considerations are the most vital to address. The design criteria will vary if habitat improvement is integral to the purpose of the riparian buffer or water quality is the primary issue. Additionally, design criteria must consider the soil functionality, climate, existing and future land management, vegetation selection, and other factors.

Long-term outcomes from expertly designed riparian buffers are predicated on the selected resource considerations. However, emerging interest in riparian buffers to accumulate soil carbon and its long-term preservation are increasingly recognized as an integral design consideration. Additionally, riparian buffers are expected to sustain natural resources from increasing intense weather caused by climate change.

The study area is a riparian buffer established along Williams Creek in Cape Girardeau County, Missouri. The mixed deciduous stand increased the soil organic matter content compared to the adjacent agriculture field, a consequence attributed to increased soil carbon additions because of a greater net primary production. Sulfate and ammonium were similarly greater in the riparian buffer, a feature attributed to increased rates of mineralization. This project reflects outcomes predicted by the literature cited.

## **Author details**

Michael Aide\* and Indi Braden Department of Agriculture, Southeast Missouri State University, USA

\*Address all correspondence to: mtaide@semo.edu

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
