Linking soil biodiversity and ecosystem function in a Neotropical savanna

TLDR: In this article, the role of rainfall seasonality on soil biodiversity and physicochemical properties was investigated in the Brazilian savanna, and the authors found that the abundance of the Formicidae family was the most abundant with 50% of all individuals in the dry season (April to September), while in the rainy season (October to March), the Isoptera order was the largest with approximately 39% of individuals.

About: This article is published in Applied Soil Ecology.The article was published on 2022-01-01 and is currently open access. It has received 11 citations till now. The article focuses on the topics: Epigeal & Soil biology.

Figures

Fig. 3. Pearson's correlation coefficients (r) among rainfall, litter production and decomposition rates, and soil epigeic fauna community variables measured in a typical savanna ecosystem in central Brazil. Crossed squares indicate non-significance at the 95% confidence level.

Fig. 5. (a) Seasonal NMDS clustering of soil epigeic fauna communities. The stress value of the ordination is indicated. Ellipses indicate the 95% confidence interval of the group centroids. Each point indicates a plot, in a total of 12 for each season, where squares represent the dry and triangles the rainy season. (b) Seasonal NMDS including the soil epigeic fauna taxa and community metrics, litterfall and rainfall vectors significant at the 95% confidence level. (c) Principal component analysis (PCA) of annual soil epigeic fauna abundance, Shannon's diversity and Pielou's evenness, leaf and wood decomposition rates (k at 720 days), soil organic matter (SOM in dag kg-1), sum of bases (SB in cmolc dm-3), effective cation exchange (CECe in cmolc dm-3), potential acidity (H + Al in cmolc dm-3), available phosphorus (Pav in mg dm-3) and pH. Each point represents the plot averages of these variables in a total of 12 plots. PC1 (x-axis) explained 47.4%, and PC2 (y-axis) explained 19% of the total variance in the soil and litter data. (d) Annual NMDS including soil epigeic fauna taxa (total abundance per plot) and the variables from (c) significant at the 95% confidence level. The stress value of the ordination is indicated. The statistical results of the NMDS’s and PCA are listed in Supplementary Table S2.

Frequently asked questions

Q1. What are the contributions mentioned in the paper "Linking soil biodiversity and ecosystem function in a neotropical savanna" ?

Conserving the remaining savanna ecosystems in the Brazilian savanna ( Cerrado ) — a global biodiversity hotspot that stores carbon and provides water to a large portion of South America — requires understanding the ecological processes maintaining their function. This study advances their understanding of the mechanisms governing nutrient cycling in savanna ecosystems on nutrient-impoverished soils, with implications for achieving sustainable conservation and restoration goals. 

Q2. Why is understanding the soil fauna essential for ecosystem conservation practices?

Because so many processes are conducted and affected by these organisms — nutrient cycling, waste decomposition, soil aggregation, climate regulation, pathogen resistance — understanding these communities is essential for ecosystem conservation practices (Guerra et al., 2021). 

Q3. How long did the decomposition of leaf litter last?

During the dry season (from May to August – 30 to 120 days exposure), leaf and wood litter decomposition remained almost inactive, decomposing only 0.97% and 2.2%, respectively. 

Q4. What is the role of litterfall in nutrient cycling in the Cerrado ecosystem?

Considering litterfall plays such an essential role in nutrient cycling by providing a means of supplying nutrients to the soil and serving as a niche and food for soil fauna (Giweta, 2020), global climatic changes can alter nutrient cycles in Brazilian Cerrado ecosystems. 

Q5. What is the percentage of the total plant material deposited on the soil?

fractions other than leaves, especially fine wood, can make up to 30–40% of the total plant material deposited on the soil (Correia and Andrade, 2008). 

Q6. What is the relationship between leaf litter and soil epigeic fauna?

Certain soil epigeic fauna groups, like Hemiptera and Collembola, were more related to the rainy season collections, while Formicidae was more associated with the dry season collections. 

Q7. What are the essentials of soil organism classifications?

soil organism classifications are essential for the various ecological compartments and provision of essential ecosystem services such as organic matter decomposition. 

Q8. What was the method used to compare the soil fauna groups?

The authors then conducted non-metric multidimensional scaling (NMDS) ordinations (metaMDS function in vegan package; Dixon, 2003) based on Bray-Curtis dissimilarity (vegdist function in vegan package) and standardized data (Legendre, 2008) to compare: i) the mean abundances of soil epigeic fauna groups per plot between seasons, and ii) the annual abundances of soil fauna groups among plots. 

Q9. What is the link between leaf litter decay and soil mineral colloids?

Leaf litter decay is a crucial nutrient cycling process linked with soil solution P in highly-weathered soils — such as those in the studied savanna — due to strong P adsorption on soil mineral colloids (Novais et al., 2007). 

Q10. How many days did the litter have to decay?

The half-life was calculated as: Xt = X0 × e-kt, where Xt is the dry weight of the remaining litter after t days and X0 is the dry weight of litter material at t = 0, and T1/2 = ln (2) / k, where T1/2 is the number of days needed to decay 50% of the initial mass, ln is the natural logarithm and k is the decomposition rate. 

Q11. What is the role of the soil fauna in savanna ecosystems?

little is known about soil epigeic fauna communities and their links with litter decomposition and how climate drivers and soil properties can alter litter production and decomposition rates, in turn affecting those soil communities in savanna ecosystems. 

Q12. How are the decomposition rates of litter estimated?

Litter decomposition rates are generally empirically estimated through decomposition bags, where the leaf fraction is stored and left in the field to measure the decay rate (Olson, 1963). 

Q13. What are the key ecosystem components influenced by climatic conditions?

their findings highlight the close links between soils and vegetation, which are key ecosystem components influenced by climatic conditions. 

Q14. What is the correlation between litter decomposition and soil fauna activity?

Litter decomposition correlates strongly with temperature and humidity (Lavelle et al., 1993; Wall et al., 2008) as both climate variables control soil fauna activity and, consequently, decomposition rates. 

Q15. What is the main reason for the lack of studies in the Cerrado?

The scarcity of studies in the Cerrado represents a major gap in soil biodiversity knowledge and reinforces the need for future studies surveying soil fauna, especially in areas covered by native savanna vegetation undergoing chronic environmental alterations. 

Q16. What is the link between litter decay and soil fauna diversity?

This pattern can be associated with the soil epigeic fauna spatial distribution (Giweta, 2020) that leads to a slow litter decay, promoting an increase in soil organic matter and C stocks (Primavesi, 1981).