| Popis: |
The association of microorganisms and soil nutrient cycles has been observed for over 200 years, and their importance in the soil phosphorus (P) cycle is well documented. In-soil trophic interactions between bacteria and bacterivorous nematodes have been implicated in increased plant access to soil organic P (Po).However, the existing data remains inconclusive and lacks detail and predictability. This work aimed to (1) assess the impact of nematodes as an additional trophic-level on Po use by plants in arable systems and (2) further understand the mechanisms of in-soil trophic interactions in improving plant acquisition of Po. To address these aims criteria based meta-analysis, glasshouse plant growth trials, in vitro and soil, and long term experimental (LTE) platforms were used. Results led to the conclusion that nematodes did not improve plant acquisition of Po per se. Time, soil P concentration and soil biological community composition had significant impacts on plant response. Although these factors were identified in two contrasting studies, their impacts on plant responses were stochastic. Complexity, which describes the average number of trophic links per species, framed an understanding of these data where they evaded predictability, specifically when considering the temporal nature of these relationships. For example, data from the meta-analysis and the plant growth trials demonstrated it was not simply the additive effect of the number of species or the addition of a specific species which resulted in predictable plant P responses. Nematode community analysis from the LTE’s yielded characteristics indicative of stability in the biotic component of systems previously considered disturbed (arable). This exposed the question of the nature of disturbance (whether natural or anthropogenic). Additionally, it highlighted the importance of which successional time-point was being studied and the impact this has on the data captured. Data collected from this long-term experiment, plant growth trials and the meta-analysis highlights the importance of the temporal resolution, and the time-point at which we are observing these dynamic systems. It is argued that in-conclusive or negative results could represent true details of these systems, where they represent points of transition between stable and/or predictable states and a usual characteristic of the complex system. Therefore, inconclusive data should not be omitted from the research library, exclusion of such data could lead to incomplete observations and incorrect assumptions. Better practices should be designed and implemented to ensure publication bias is not a barrier to our understanding of these systems. |
