Effects of nitrogen deposition on the spatial pattern of biocrusts and soil microbial activity in a semi‐arid Mediterranean shrubland

Abstract

Human activities have doubled, or even tripled, the amount of nitrogen (N) fixed globally, which alters the functioning and reduces the biodiversity of terrestrial ecosystems. In this study, we used a 10‐year N addition experiment in a semi‐arid Mediterranean shrubland in central Spain to evaluate the effects of increased N deposition on biocrust cover, soil microbial enzymatic activity and their spatial patterns. We collected highly replicated, spatially explicit data to carry out Moran's I correlograms at the plot level and used linear mixed models to evaluate the effects of N addition on cover, microbial activity and Moran's I values for each distance class of correlograms. High N deposition (50 kg N ha−1 year−1) reduced the cover of the foliose lichen Cladonia foliacea, an important component of biocrusts, and generated significant alterations and losses of the spatial pattern of biocrusts and soil microbial enzymatic activity. Furthermore, we found indication that N addition altered the relationship between biocrust cover and microbial enzymatic activity, suggesting that the presence of well‐developed biocrust communities modulates the effects of high N deposition on soil microbial activity. Synthesis. Overall, our study suggests that an increase in N deposition may have important consequences for the structure and functioning of Mediterranean ecosystems and that some of these consequences may be due to alterations in the way in which different soil communities (e.g. moss‐lichen biocrusts and soil microorganisms) interact with one another. A free Plain Language Summary can be found within the Supporting Information of this article.

More drought leads to a greater significance of biocrusts to soil multifunctionality

“…The relationships between biodiversity and soil functions are critical issues in ecological research (Garibotti et al., 2018). At present, soil multifunctionality (SMF) is more representative than a single soil function in terms of the ecosystem responses to biodiversity alterations, and most studies on this topic have been conducted on terrestrial plants, bacteria, soil invertebrates and seagrasses (Benvenutto‐Vargas & Ochoa‐Hueso, 2020; Heilpern et al., 2020; Wagg et al., 2019; Zhou et al., 2020). Each trophic organism participates in the specifically ecological process, and thus, their community diversity may differentially affect SMF (Martinez‐Almoyna et al., 2019).…”

Soil extracellular oxidases mediated nitrogen fertilization effects on soil organic carbon sequestration in bioenergy croplands

“…For instance, in a California grassland, fertilization with N plus other macronutrients and micronutrients diminished spatial variability of fungal composition due to increases in antagonistic fungi, whereas bacterial and archaeal community composition showed little change in their spatial variability (Gravuer et al, 2020b). In a semi‐arid Mediterranean shrubland, high N deposition (50 kg N ha −1 year −1 ) resulted in significant losses of the spatial pattern of soil oxidase activities that was attributed to the presence of well‐developed biocrust communities mediating the effects of high N deposition on soil oxidases (Benvenutto‐Vargas & Ochoa‐Hueso, 2019). Nevertheless, microbial spatial footprint associated with higher enzyme activities and microscale pores promoted soil carbon stabilization (Kravchenko et al, 2019).…”

Biological Soil Crusts as Ecosystem Engineers in Antarctic Ecosystem

“…Biological Soil Crusts (BSCs) also participate in the incorporation of nutrients into the soil, such as P ( Baumann et al, 2017 ), and increase the concentration of other essential elements such as K, Fe, Cl, Mn, and S ( Lange et al, 1994 ; Rogers and Burns, 1994 ; Belnap and Lange, 2001 ; Harper and Belnap, 2001 ; Bowker et al, 2016 ). On the other hand, these microbial communities also promote the presence of secondary metabolites and amino acids in the soil ( Swenson et al, 2018 ) by enhancing enzymatic activity and nutrient cycling processes ( Benvenutto-Vargas and Ochoa-Hueso, 2020 ). This, in turn, can positively impact vascular plants’ germination, growth, nutritional state, physiological performance, distribution, and abundance ( Belnap et al, 2001 ; Shepherd et al, 2002 ; Zhang and Nie, 2011 ; Zhang and Belnap, 2015 ), especially in resource-limited environments.…”