|LI, CHENHUI - Texas Tech University|
|FULTZ, LISA - Louisiana State University|
|MOORE-KUCERA, JENNIFER - Natural Resources Conservation Service (NRCS, USDA)|
|KAKARLA, MAMATHA - Texas Tech University|
|WEINDORF, DAVID - Texas Tech University|
Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2017
Publication Date: 3/20/2018
Citation: Li, C., Fultz, L.M., Moore-Kucera, J., Acosta Martinez, V., Kakarla, M., Weindorf, D. 2018. Soil microbial community restoration in conservation reserve program semi-arid grasslands. Soil Biology and Biochemistry. 118:166-177. https://doi.org/10.1016/j.soilbio.2017.12.001.
Interpretive Summary: The Conservation Reserve Program (CRP) is known to play a crucial role in reducing soil erosion. Texas leads the nation in land area enrolled in this program; however, little is known about the restoration of its soil biological component, which is crucial to promote soil health. For this purpose scientists from ARS (Lubbock, TX), Natural Resource Conservation Service, Texas Tech University and Louisiana State University conducted an evaluation of the soil health of 26 sites under CRP on the Texas High Plains (THP) was done in 2012 and 2014 in two soil depths of 0-4 inches and 4-12 inches with an increase in fungal abundance through the initial 15 years of CRP and then a decline thereafter. Overall, on the THP the CRP is an effective practice to restore overall soil microbial biomass, re-establish the soil microbial community, and improve soil microbial functions related to nutrient cycling and C sequestration.
Technical Abstract: The Conservation Reserve Program (CRP) in the Southern High Plains (SHP) is known to play a crucial role in maintaining ecosystem health by reducing soil erosion. However, the restoration of its soil biological health (biological community and its function) over time have not been clearly elucidated. The objective of this study was to describe the changes in the soil microbial community composition over years of establishing CRP using a CRP chronosequence. Soil samples (0-10 cm and 10-30 cm) were collected in 2012 and 2014 from 26 fields across seven counties within the SHP and included seven croplands (representing 0 y in CRP), 16 CRP fields of varying ages (8-28 y as of 2014), plus three rangelands (representing no disturbance for > 30 y). Multiple regression analysis was conducted to evaluate the impacts of CRP restoration on soil microbial biomass. Shifts in soil microbial community composition, according to fatty acid methyl ester (FAME) profiles, with increasing CRP restoration years were explored using multivariate ordination. Total microbial biomass (using total FAME content as a proxy) increased with CRP years at 10-30 cm in 2012 and both depths in 2014. Although different environmental conditions were present during the two sampling years (2012 followed a record extreme drought in 2011 with conditions improving in 2014), the physiological stress of microbial community indicated by ratios of saturated to monounsaturated FAME biomarkers (sat:mono) consistently decreased with CRP restoration years in both sampling years and both depths. A shift in microbial community composition was measured during CRP restoration at 0-10 cm in both sampling years (and at 10-30 cm in 2012) with an increase in relative fungal abundance through the initial 15 years of CRP and then a decline after 15 years. The overall increase in soil microbial biomass and decrease in microbial physiological stress indicators with increasing years under CRP illustrates how this is a valuable restoration program for building soil health in the fragile, sandy SHP soils. The mechanisms underlying the decline in fungal abundance in years 15 to 28 are unclear and the associated reduction in the fungal to bacterial ratio does not necessarily reflect reduced soil health. A high fungal abundance is desirable at the beginning of the grassland and soil microbial community restoration period in order to reap the multiple, well-known benefits of a robust fungal community, such as facilitating plant productivity and soil processes such as C sequestration. Therefore, enhancing fungal support at the beginning of CRP grass establishment might be a promising strategy to maximize soil health restoration benefits.