Soil Fungal Dynamics In Perennial and Annual Crops of Integrated Crop and Livestock Systems.

To date only a few studies have investigated fungal diversity as affected by agroecosystem management. We amplified the Internal Transcribed Spacer (ITS) region using ITS5 and ITS2 primers with a 454 FLX pyrosequencing system to assess fungal diversity.  Soils from three integrated crop-livestock (beef) production (ICL) systems were compared to two continuous cotton (Gossypium hirsutum L.) systems (CTNc) in the semiarid Texas High Plains. The ICL systems included: 1) forage-cotton system (FRG_CTN) comprised of perennial native-grasses and a cotton-foxtail millet (Seteria italic) rotation (Mi-Ct); 2) ‘WW-B. Dahl’ old world bluestem (OWB; Bothriochloa bladhii) and bermudagrass (Cynodon dactylon) system (OWB_BER); and 3) OWB/corn (Zea Mays) rotation system (OWB_RC).  An average of 2484 OTUs per sample were identified, out of these 84% were Ascomycota (Fusarium 11%; Preussia 8%; Penicillium 2%) and 7% were Basidiomycota (Agaricomycetes 75%; Tremellomycetes 13%). The ICL systems FRG_CTN, OWB_BER, and OWB_RC were characterized by having the highest relative abundance of Hypocreales, Mortierellales, Phyllachorales, respectively.  The perennial components of the ICLs contained higher abundances of the fungal orders Glomerales and Eurotiales whereas CTNc systems had higher abundance of Pleosporales and Filobasidiales and the Mi-Ct rotation component of FRG_CTN was characterized by high abundance of Hypocreales; thus implying their significant roles in these systems. Compared to the perennial-grasses, CTNc and Mi-Ct had lower fungal diversity, which could result in the loss of functional complementarity including nutrient cycling or resistance to pathogens by competition is affected. A significant positive correlation was found between Glomerales, Microascales and Onygenales  and soil properties such as total carbon, microbial biomass carbon and enzyme activities involved in phosphorus, carbon, and nitrogen cycling. These findings provide some insights on the key fungal groups that sustain soil metabolic functioning under agroecosystems that integrated livestock and cropping.