Orchard recycling improves climate change adaptation and mitigation potential of almond production systems

WOR increased the formation and stability of large macroaggregates and preserved a larger quantity of intra-aggregate SOC relative to other aggregate fractions. The incorporation of woody biomass may provide sorption points for the formation of aggregate-scale microbial habitats while providing substrate for microbial growth, thereby providing energy and a favor- able environment for particle aggregation and protection of soil C. A significant positive corre- lation between the SOM content, SOC, and aggregate MWD further confirms this trend, which was in accordance with the results reported by Fonte et al. [49], who found that macro- aggregates were a large reservoir of organic C. A large input of plant residues in this system is likely one of the main factors underlying the improved content and stability of macroaggre- gates within the surface soil layer, resulting in more protection of soil C pools and longer turn- over periods of sequestered C. Labile carbon pools (POxC and MBC) also increased after biomass reincorporation. Differ- ences in total SOC content of orchard soils were correlated to MBC, as well as BG and NAG activity potential, indicating that increased microbial biomass and C cycling under WOR had benefits for SOC storage. These results are in accordance with the observations of Bonanomi et al. [50], who found that high enzyme activities were mainly attributable to the relatively higher SOC and to energy sources and nutrients that sustain growth and activity of soil microbes. An increase in mineralization of organic substances from woody biomass decompo-

sition may have in turn contributed to promoting the cementation of soil particles, forming Fig 3. Effect of Grind and Burn treatments on (a) Proportion of soil aggregate fractions, (b) mean weight diameter (MWD), (c) water retention curves, and (d) infiltration rate. (�) indicate significant differences at P �0.05. https://doi.org/10.1371/journal.pone.0229588.g003 PLOS ONE Whole orchard recycling PLOS ONE | https://doi.org/10.1371/journal.pone.0229588 March 27, 2020 12 / 22