The establishment of apple orchards as temperate forest garden systems and their impact on indigenous bacterial and fungal population abundance in Southern Ontario, Canada

Abstract

This research investigated soil microbial abundances affected by different ground management systems in establishing apple (Malus domestica cv. Idared, M9) orchards in Ontario, Canada. Four treatments, including forest garden systems with and without compost (FGSC and FGS), and grass understory systems with and without compost (GC and G), were assessed over two establishment years for gene copy abundance of soil arbuscular mycorrhizal (AM) fungi, total fungi and total bacteria using quantitative real-time polymerase chain reactions. Time had a greater effect on all three soil microbial abundances, with total bacterial and AM fungi decreasing and total fungal abundance increasing from spring 2013 to fall 2014. The changes were greatest between the sampling dates of fall 2013 and spring 2014, which is 1 yr after the establishment of the experimental apple plots. There were no significant differences in soil microbial abundances between treatments at any specific sampling date. Apple tree trunk circumference was greatest for FGSC and FGS after 2 yr, but no significant differences in GC and G treatments. In the last sampling period, fall 2014, FGSC plots had significantly greater trunk circumferences compared with G plots. Soil chemical properties neither changed over the 2 yr, nor did they differ between treatments at any one sampling time. We conclude that the applebased FGS treatments can benefit apple tree growth and there is a basis for future research to explore specific plantplant, plant-microbe and microbe-microbe relations in FGSs.

Impact of Cover Crops on the Soil Microbiome of Tree Crops

“…These changing soil conditions and increased organic inputs likely drive the increased microbial diversity found in soils of perennial systems planted with cover crops [11,14,58]. This increased soil microbial diversity is positively correlated with nearly all of the benefits of cover crops to production systems, including increased soil organic carbon (SOC) and total N (TN) contents and, ultimately, tree production [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] (Table 1). Changes can persist throughout the long-term management of a perennial system, as 10 and 22 years of planting a monoculture cover crop of F. macrophylla in rubber (E. urophylla) orchards increased bacterial gene abundance and diversity down to a depth of 60 cm within the soil profile compared with the no-cover-crop control treatment [35].…”

The effect of trees on arbuscular mycorrhizal fungi and nutrient acquisition of grassland plant communities in three temperate silvopastoral systems

“…Furthermore, silvopastoral systems are largely underrepresented in agroforestry literature (Miller et al, 2019). The aim of our study was to investigate the effects of apple trees (whose association with AMF is well documented (Huang et Wartman et al, 2017) on AMF colonisation and nutrient acquisition by the understory grassland plant community (GPC) of silvopastoral systems. A paired site approach was used to compare AMF biomass, AMF colonisation, GPC root biomass, and GPC nutrient acquisition between silvopastoral plots and identically managed (except for the presence of trees) adjacent treeless pastures which acted as control plots.…”