Soil microbial diversity and soil functioning affect competition among grasses in experimental microcosms

Abstract

A gradient of microbial diversity in soil was established by inoculating pasteurized soil with microbial populations of different complexity, which were obtained by a combination of soil fumigation and filtering techniques. Four different soil diversity treatments were planted with six different grass species either in monoculture or in polyculture to test how changes of general microbial functions, such as catabolic diversity and nutrient recycling efficiency would affect the performance of the plant communities. Relatively harsh soil treatments were necessary to elicit visible effects on major soil processes such as decomposition and nitrogen cycling due to the high redundancy and resilience of soil microbial communities. The strongest effects of soil diversity manipulations on plant growth occurred in polycultures where interspecific competition between plants was high. In polycultures, soil diversity reduction led to a gradual, linear decline in biomass production of one subordinate grass species (Bromus hordeaceus), which was compensated by increased growth of two intermediate competitors (Aegilops geniculata, B. madritensis). This negative covariance in growth of competing grass species smoothed the effects of soil diversity manipulations at the plant community level. As a result, total shoot biomass production remained constant. Apparently the effects of soil diversity manipulations were buffered because functional redundancy at both, the microbial and the plant community level complemented each other. The results further suggests that small trade-offs in plant fitness due to general functional shifts at the microbial level can be significant for the outcome of competition in plant communities and thus diversity at much larger scales.

Soil biodiversity and soil community composition determine ecosystem multifunctionality

“…This suggests that the consequences of simplified soil community composition and reduced soil diversity may become progressively more inhibiting as time passes. Additionally, because plant diversity is also a driver of ecosystem multifunctionality (3-5, 23), the strong effects of soil organisms on plant diversity, observed here and elsewhere (15)(16)(17)(18)(19)(20), could indirectly influence a number of other ecosystem functions, such as nutrient availability (23) and C sequestration (26). A path analysis indeed indicated that effects of soil biodiversity and composition on measures of nutrient losses were, in part, indirect and mediated by soil biodiversity-induced changes in plant diversity and productivity (SI Appendix, Figs.…”

“…Litter decomposition was assessed with litterbags containing 15 N-labeled sterilized L. multiflorum shoots that were added to microcosms at the start of the experiment. The ability for a plant to acquire N through the mineralization of its litter is defined here as "N turnover."…”

“…This has triggered increasing concern that reduced biodiversity in soils may impair numerous ecosystem functions, such as nutrient acquisition by plants and the cycling of resources between above-and below-ground communities (6,11,13,14). However, to date research has largely focused on the effects of specific groups of organisms, such as soil microbes (15,16), mycorrhizal fungi (17, 18), and soil fauna (19,20), or on large-scale correlative analysis in the field (13). However, soil organisms interact within complex food webs, and therefore changes in diversity within one trophic group or functional guild may alter the abundance, diversity, and functioning of another (21,22).…”

Microbial Diversity: Relevance and Relationship Between Environmental Conservation And Human Health

“…Despite the continued use of land for agricultural practices, the soil may be rich in the biological point of view, since many microorganisms found in this environment are considered important in the biological control of diseases and pests of agriculture (Andreoti 2009). Thus, microbial processes play a fundamental importance in the functioning of production systems, performing tasks directly related to their productivity and sustainability (Boncowski and Roy 2005). Rice is a plant of the genus Oryza of the grass family.…”

A meta-analysis of soil biodiversity impacts on the carbon cycle

“…For example, studies have manipulated the diversity within groups of microorganisms (e.g., bacteria (Bonkowski and Roy, 2005;Griffiths et al, 2000) and mycorrhizal fungi (van der Heijden et al, 1998;Maherali and Klironomos, 2007)), soil mesofauna (e.g., microarthropods; Liiri et al, 2002), and macrofauna (Heemsbergen et al, 2004;Zimmer et al, 2005). Other studies have manipulated the diversity across groups of soil organisms that differ in body size (i.e., microbes, and micro-, meso-, or M.-A.…”