Eucalypt harvest residue management influences microbial community structure and soil organic matter fractions in an afforested grassland
Introduction
The ever-increasing global wood demand requires sustainable intensification of production forestry. Plantation forests have expanded globally at an annual rate of ∼4.4 Mha over recent decades (Payn et al., 2015), particularly with exotic species managed as short-rotations in tropical and subtropical regions. Eucalyptus trees are the most widely planted hardwood and occupy an estimated area of 25 million ha across 90+ countries (Zhou et al., 2020). Eucalypt plantations cover 5.6 Mha in Brazil, and the high growth rates of these plantations favor expansion and place the country as a prominent supplier of pulp and industrial timber (Colodette et al., 2014). The rapid accumulation of carbon (C) in their biomass exerts a critical role in mitigating greenhouse gas emissions by acting as an efficient C sink and reducing pressure over native forests (Sanquetta et al., 2018). Additionally, active management of plantation forests may result in longer-term C sequestration through increasing soil organic matter (SOM) levels (Mayer et al., 2020), which is critical to the sustainability of production forestry in the tropics and subtropics (Gonçalves et al., 2013).
Short-rotation eucalypt plantations generate considerable amounts of plant litter and residues at harvest (Gatto et al., 2010). Retaining harvest residues (HR) in the field is considered an option to recycle C and nutrients back into the soil (Laclau et al., 2010; Oliveira et al., 2018). Nonetheless, the fate of HR in the soil is still unclear. Manipulating the intensity of harvesting changes the amount and quality of HR that remain in the field. The gross biomass of eucalypt HR is lignin-rich and has a high C:nitrogen (N) ratio (Ferreira et al., 2018b), but different components (i.e., leaves, branches, bark, treetops, and roots) may decompose at different rates because of differences in biochemistry (Walela et al., 2014). Particularly, tree bark is assumed to be recalcitrant because of its abundance in polymeric compounds (e.g., lignin, tannins, terpene) (Lima et al., 2013), so manipulating the presence of bark is expected to alter the decomposition of HR (Adamczyk et al., 2015; Souza et al., 2016) and to influence soil organic carbon (SOC) dynamics (Cotrufo et al., 2013; Souza et al., 2020). However, the relationship between litter quality, decomposition, and SOC accumulation is complex due to the interactive effects on biological process (Fanin et al., 2011; Keiblinger et al., 2010), including shaping microbial community structure (Baumann et al., 2009), and remains uncertain.
High productivity eucalypt plantations are commonly N fertilized at planting. Changes in N availability will likely alter HR decomposition, with possible implications for SOC storage (Du et al., 2014; Oliveira et al., 2018). Specifically, higher N availability alleviates C:N stoichiometric constraints (Koranda et al., 2014) and might accelerate decomposition in early stages (Wang et al., 2011), but inhibit the decomposition of lignin-rich compound during late stages (Carreiro et al., 2000). However, the response of HR decomposition and SOC dynamics to N addition may differ with different harvesting intensities. For instance, lignin and carbohydrate concentrations, which are abundant on eucalypt HR but differ between its components (Ferreira et al., 2018b), have interactive effects with N on soil microbial structure, e.g., soil fungal and bacterial proportions (Baumann et al., 2009). There is little information on how the microbial community responds to HR management practices and N availability in eucalypt plantations, and the lack of studies linking the soil microbial community and SOC dynamics in this increasingly common land use represents a major knowledge gap (Mayer et al., 2020).
In this study, we tested two hypotheses to investigate the effect of HR management and N availability on the dynamics of SOM pools:
- 1)
the bark retention induces changes in microbial community structure and increases SOC concentrations by increasing HR quantity and complexity;
- 2)
increasing N availability through mineral-N addition stimulates HR decomposition rates and favors soil microbial biomass and SOC accrual by ameliorating the effect of HR low N concentration during early stages of decomposition.
Isolating the HR-derived C (HR-C) from C sources of aboveground litter and root turnover originating during a multiyear rotation represents a technical research challenge in perennial crops (Binkley et al., 2004; Ferreira et al., 2018a). Thus, to test our hypotheses, different harvesting intensities and N additions were simulated in a field experiment in a recently eucalypt afforested grassland (C4-dominated), and differences in the 13C natural abundance were used to assess SOM changes (Maquere et al., 2008). Incorporation of HR-C (C3-C source) into phospholipid fatty acids (PLFA) and particle size fractions of the native C4-SOC topsoil was determined using 13C isotope mass spectrometry over one year, i.e., during early decomposition stages.
Section snippets
Site description
The study was conducted in a commercial eucalypt plantation located at São Gabriel, Rio Grande do Sul (RS) state, southern Brazil (30°26’S; 54°31’W). The site is representative of the region where eucalypt expansion has been occurring on Pampa native grasslands. The Pampa biome covers 63% of the RS state and holds a diversity of soils and a complexity of plants with the prevalence of C4 grassland species (Overbeck et al., 2007). The local climate is humid subtropical without a dry season and
Respiration rates as influenced by HR management
The mean respiration rates of treatments with HR removal (-R) were similar at 3 and 6 months (9.23 mg CO2-C kg soil-1 day-1), which were higher than the rate observed at 12 months (3.16 mg CO2-C kg soil-1 day-1) (Fig. 2; Table A.1). In both +R/-B and +R/+B, respiration rates increased from 3 to 6 months but had the lowest rate after 12 months of decomposition (∼6.30 mg CO2-C kg soil-1 day-1). The presence of HR (+R) stimulated respiration throughout the experiment; +R/+B caused an additional
Influence of bark management and N-addition on decomposition rates of eucalypt HR and respired CO2
Simulating typical HR management options in a recently afforested site wherein eucalypt species-specific decomposer communities are yet absent or transitioning could impact the decay rate of HR (home-field advantage (HFA) hypothesis; Ayres et al., 2009). However, HFA remains controversial in forest ecosystems (Bachega et al., 2016; Gama-Rodrigues and Barros, 2002; Veen et al., 2015). In our site, the average HR t0.5 was 483 days, which is within the range reported in second-rotation eucalyptus
Conclusion
Building and maintaining SOM is critical to the sustainability of production forestry. Manipulating harvesting intensity can reduce C and nutrient export and provide multiple benefits to forest soils. Our study suggests that understanding biological interactions with HR may offer a new tool for managing C cycling in eucalypt-afforested soils. Our results revealed contrasting dynamics between SOM pools with different mean residence times, particularly the sensitivity of the soil microbial
Funding
This work was supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES Finance Code 001 and grant number BEX 3725/14-6); UK Biotechnology and Biological Science Research Council (BBSRC) (project number BBS/E/C/00005214) and NUTREE research group.
Declaration of Competing Interest
The authors declare no conflict of interest.
Acknowledgments
Thanks are due to the CMPC Celulose Rio Grandense for providing access to experimental area and assistence in the fieldwork. We also thank the following colleagues for their help with this work: Claire Horrocks and Adrian Joynes (technical support with PLFA analysis) and Dan Dhanoa (advice on statistical analyses) at Rothamsted Research, and João Milagres and Lucas Guimarães (technical support with SOM analyses) at Federal University of Viçosa.
References (69)
- et al.
Monoterpenes and higher terpenes may inhibit enzyme activities in boreal forest soil
Soil Biol. Biochem.
(2015) - et al.
Home-field advantage accelerates leaf litter decomposition in forests
Soil Biol. Biochem.
(2009) - et al.
Decomposition of Eucalyptus grandis and Acacia mangium leaves and fine roots in tropical conditions did not meet the Home Field Advantage hypothesis
For. Ecol. Manage.
(2016) - et al.
Residue chemistry and microbial community structure during decomposition of eucalypt, wheat and vetch residues
Soil Biol. Biochem.
(2009) - et al.
Priming effects in Chernozem induced by glucose and N in relation to microbial growth strategies
Appl. Soil Ecol.
(2007) - et al.
Microbial community structure mediates response of soil C decomposition to litter addition and warming
Soil Biol. Biochem.
(2015) - et al.
The variable response of soil microorganisms to trace concentrations of low molecular weight organic substrates of increasing complexity
Soil Biol. Biochem.
(2013) - et al.
Impacts of organic residue management on the soil C dynamics in a tropical eucalypt plantation on a nutrient-poor sandy soil after three rotations
Soil Biol. Biochem.
(2015) - et al.
Does variability in litter quality determine soil microbial respiration in an Amazonian rainforest?
Soil Biol. Biochem.
(2011) - et al.
Temporal decomposition sampling and chemical characterization of eucalyptus harvest residues using NIR spectroscopy and chemometric methods
Talanta
(2018)
Nutrient release from decomposing Eucalyptus harvest residues following simulated management practices in multiple sites in Brazil
For. Ecol. Manage.
Integrating genetic and silvicultural strategies to minimize abiotic and biotic constraints in Brazilian eucalypt plantations
For. Ecol. Manage.
The influence of microbial communities, management, and soil texture on soil organic matter chemistry
Geoderma
Organic residue mass at planting is an excellent predictor of tree growth in Eucalyptus plantations established on a sandy tropical soil
For. Ecol. Manage.
Tamm Review: Influence of forest management activities on soil organic carbon stocks: A knowledge synthesis
For. Ecol. Manage.
Eucalyptus globulus harvest residue management effects on soil carbon and microbial biomass at 1 and 5 years after plantation establishment
Soil Biol. Biochem.
Brazil’s neglected biome: The South Brazilian Campos
Perspect. Plant Ecol. Evol. Syst.
Changes in planted forests and future global implications
For. Ecol. Manage.
Forest residue removal decreases soil quality and affects wood productivity even with high rates of fertilizer application
For. Ecol. Manage.
Forest residue maintenance increased the wood productivity of a Eucalyptus plantation over two short rotations
For. Ecol. Manage.
Carbon input belowground is the major C flux contributing to leaf litter mass loss: Evidences from a 13C labelled-leaf litter experiment
Soil Biol. Biochem.
Nitrogen management in Eucalyptus nitens plantations
For. Ecol. Manage.
Decomposition of eucalypt harvest residues as affected by management practices, climate and soil properties across southeastern Brazil
For. Ecol. Manage.
The molecular composition of lignin in spruce decayed by white-rot fungi (Phanerochaete chrysosporium and Trametes versicolor) using pyrolysis-GC–MS and thermochemolysis with tetramethylammonium hydroxide
Int. Biodeterior. Biodegradation
The initial lignin:nitrogen ratio of litter from above and below ground sources strongly and negatively influenced decay rates of slowly decomposing litter carbon pools
Soil Biol. Biochem.
Three-source partitioning of CO2 efflux from soil planted with maize by 13C natural abundance fails due to inactive microbial biomass
Soil Biol. Biochem.
Taxonomy, physiology, and natural products of Actinobacteria
Microbiol. Mol. Biol. Rev.
Effect of N deposition on decomposition of plant litter and soil organic matter in forest systems
Environ. Rev.
First-Rotation changes in soil carbon and nitrogen in a plantation in Hawaii
Soil Sci. Soc. Am. J.
Decomposition of Nitrogen-15 labeled Hoop pine harvest residues in subtropical Australia
Soil Sci. Soc. Am. J.
Microbiota, fauna, and mesh size interactions in litter decomposition
Oikos
Particulate soil organic-matter changes across a grassland cultivation sequence
Soil Sci. Soc. Am. J.
Microbial enzyme shifts explain litter decay responses to simulated nitrogen depoisition
Ecol. Soc. Am.
Crop residue harvest for bioenergy production and its implications on soil functioning and plant growth: A review
Sci. Agric.
Cited by (8)
Logging residues promote rapid restoration of soil health after clear-cutting of rubber plantations at two sites with contrasting soils in Africa
2022, Science of the Total EnvironmentCitation Excerpt :Many studies show that logging residues have a strong impact on soil indicators related to carbon transformation. In eucalypt plantations, keeping logging residues on the soil surface after clear-cutting increased the microbial biomass in Brazil (Maillard et al., 2019; Oliveira et al., 2021) and greatly increased soil carbon respiration (Epron et al., 2015; Versini et al., 2013). Importantly, in our study the application of low (R1L1) or high (R2L1) amounts of logging residues on the soil surface did not significantly influence the restoration of carbon transformation function.
Integrating forest residue and mineral fertilization: effects on nutrient acquisition, nutrient use efficiency and growth of eucalypt plants
2021, Forest Ecology and ManagementCitation Excerpt :Importantly, this practice can positively change various soil chemical, physical and biological characteristics (Jesus et al., 2015; Ferreira et al., 2016) that in turn affect the acquisition and use of nutrients by plants. For instance, the maintenance of FHR can increase soil hydraulic conductivity (Jesus et al., 2015), increase soil organic matter (Rocha et al., 2016), reduce soil compaction (Andrade et al., 2017) and soil losses by erosion (Rocha, 2014) and increase soil biological activity (Mendham et al., 2002; Oliveira et al., 2021). Nonetheless, it is also worth mentioning that nutrient immobilization can reduce, at least temporarily, the availability of some nutrients (e.g., N and P) to plants, notably when nutrient-poor residues are maintained in the area (Ferreira et al., 2016).
Nitrogen addition-driven soil organic carbon stability depends on the fractions of particulate and mineral-associated organic carbon
2024, Nutrient Cycling in Agroecosystems
- 1
Present address: Carbon Management Center, SRUC - Scotland’s Rural College, Edinburgh, Scotland, UK, EH9 3JG; and Geography, CLES - Amory Building. University of Exeter, Exeter, UK, EX4 4RJ.