Plant Growth and Arthropod Assemblage Metrics on Sapindus saponaria Fertilized With Dehydrated Municipal Sewage Sludge

Intensive agriculture can degrade soils and lead to land abandonment, threatening ecosystem functions. Arthropods play important ecological roles but are often overlooked in restoration studies. We conducted a multivariate reanalysis of a previously collected dataset to evaluate the effects of dehydrated municipal sewage sludge on Sapindus saponaria development and associated arthropod assemblage metrics in a degraded area of Montes Claros, Minas Gerais, Brazil. The experiment comprised 48 plants arranged in two treatments, with and without sewage‐sludge application, and monitored for 24 months. Monthly plant measurements were averaged separately for each individual plant, whereas repeated arthropod observations were pooled by plant over the study period. We analyzed leaves per branch, branches per plant, ground cover, cumulative arthropod observations, and species richness. Sewage‐sludge application significantly increased branches per plant and ground cover, whereas leaves per branch did not differ between treatments. Cumulative observations and species richness of chewing insects, phytophagous Coleoptera, Diptera, spiders, and total predators were significantly greater on fertilized plants, whereas Orthoptera metrics did not differ significantly. Exploratory principal component analysis summarized covariation among plant and arthropod variables, but many apparent plant‐arthropod relationships weakened after accounting for treatment and block, indicating that pooled associations partly reflected parallel responses to sewage‐sludge application. Dehydrated municipal sewage sludge therefore affected plant structure and selected arthropod assemblage metrics under the conditions evaluated, but the present data do not demonstrate that plant development directly mediated arthropod responses.