Abstract
In southern China, the eucalyptus plantation industry has been severely restricted by government policy over concerns on negative environmental impacts. In its place, large-scale plantations of high-value tropical tree species such as nitrogen-fixing Dalbergia odorifera and hemiparasite Santalum album have been widely cultivated including in mixed-species plantations. However, despite their poor growth, little information is available on suitable silvicultural practices of these plantations. Therefore, we subjected an 8-year-old mixed stand of D. odorifera and S. album to weeding, fertilization, weeding + fertilization, or no (CK) treatments and measured soil microbial biomass, respiration, nutrients, nitrogen mineralization and leaching and tree growth and litter production. Weeding and fertilization decreased microbial biomass but increased soil respiration, inhibited mineralization, had not effect on leaching of soil nitrogen, and improved the nutrient status of plantation soil. All practices improved the growth of D. odorifera. In the mixed plantation, fertilization increased litter production and nutrient content, but weeding and weeding + fertilization decreased growth of S. album and litter production in mixed plantation because weeding decreased the number of S. album haustoria in underground plant roots. In conclusion, fertilization is recommended; however, weeding-related practices are inappropriate for D. odorifera and S. album mixed plantations. These conclusions have important implications for managing other parasite or mixed-species plantations.
Highlights
Management practices are applied to improve the production and quality of plantation forests by increasing soil nutrient availability and regulating competition among plants (Erb et al 2018; Sida et al 2018)
Numerous studies have explored the effects of fertilizer application, especially nitrogen (N), on soil biological and biochemical processes, but results have been inconsistent; fertilizer application has significantly increased soil microbial biomass (Li et al 2010; Song et al 2020), microbial community diversity (Ramirez et al 2010) and soil respiration rate (Bowden et al 2004) and had negative or neutral effects (Samuelson et al 2009; Sun et al 2011; Wang et al 2017)
A one-way ANOVA and least significant difference tests were used to determine the statistical significance of differences at the 0.05 level in mean soil microbial biomass, soil respiration, soil nutrient, nitrogen mineralization and leaching, litter production and growth increment in height and in DBH (Increment in height or DBH = Height or DBH 1 year after treatment − Height or DBH before treatment) in response to the weeding or fertilization treatments for each sampling date
Summary
Management practices are applied to improve the production and quality of plantation forests by increasing soil nutrient availability and regulating competition among plants (Erb et al 2018; Sida et al 2018). Fertilization is commonly used to increase nutrient content and availability in the soils and improve productivity of plantations (Fox 2000). It can affect soil biological and biochemical properties processes such as soil microbial biomass, nutrient cycling and respiration rate (Lee and Shibu 2003). Numerous studies have explored the effects of fertilizer application, especially nitrogen (N), on soil biological and biochemical processes, but results have been inconsistent; fertilizer application has significantly increased soil microbial biomass (Li et al 2010; Song et al 2020), microbial community diversity (Ramirez et al 2010) and soil respiration rate (Bowden et al 2004) and had negative or neutral effects (Samuelson et al 2009; Sun et al 2011; Wang et al 2017). A better understanding of these effects will help better manage plantation ecosystem functions
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