Cultivar Differences and Impact of Plant-Plant Competition on Temporal Patterns of Nitrogen and Biomass Accumulation

Abstract

Current niche models cannot explain multi-species plant coexistence in complex ecosystems. One overlooked explanatory factor is within-growing season temporal dynamism of resource capture by plants. However, the timing and rate of resource capture are themselves likely to be mediated by plant-plant competition. This study used Barley ( Hordeum sp.) as a model species to examine the impacts of intra-specific competition, specifically inter- and intra-cultivar competition on the temporal dynamics of resource capture. Nitrogen and biomass accumulation of an early and late cultivar grown in isolation, inter- or intra- cultivar competition were investigated using sequential harvests. We did not find changes in the temporal dynamics of biomass accumulation in response to competition. However, peak nitrogen accumulation rate was significantly delayed for the late cultivar by 14.5 days and advanced in the early cultivar by 0.5 days when in intra-cultivar competition; there were no significant changes when in inter-cultivar competition. This may suggest a form of kin recognition as the target plants appeared to identify their neighbors and only responded temporally to intra-cultivar competition. The Relative Intensity Index found competition occurred in both the intra- and inter- cultivar mixtures, but a positive Land Equivalence Ratio value indicated complementarity in the inter-cultivar mixtures compared to intra-cultivar mixtures. The reason for this is unclear but may be due to the timing of the final harvest and may not be representative of the relationship between the competing plants. This study demonstrates neighbor-identity-specific changes in temporal dynamism in nutrient uptake. This contributes to our fundamental understanding of plant nutrient dynamics and plant-plant competition whilst having relevance to sustainable agriculture. Improved understanding of within-growing season temporal dynamism would also improve our understanding of coexistence in complex plant communities.

Plant-plant competition influences temporal dynamism of soil microbial enzyme activity

“…Leucine aminopeptidase root associated area also demonstrated a delay in activity but only when Proctor was in intra-cultivar competition. This delay in leucine aminopeptidase root associated area when in intra-cultivar competition echoes a similar trend to the delay of 14.5 days in Proctor peak above-ground nitrogen accumulation rate found in a previous study (Schofield et al, 2019). The mechanism that links these two observations is not clear.…”

“…where sampling occurred in the first month of growth, the period prior to peak nitrogen accumulation rate in these barley cultivars (Schofield et al, 2019). This is likely to be a period of soil microbial community priming to mine for nitrogen within soil organic matter and may account for the differences between Ma et al's and our study.…”

“…Enzyme activity was measured three times at weekly intervals between 18 and 39 days after planting. This is the period prior to peak barley nitrogen accumulation rate found in our previous study (Schofield et al 2019). Areas away from the competition zone between the two plants were visually identified and labelled on the rhizobox rim to ensure measurements of soil enzyme activity occurred at a consistent location throughout the study.…”

“…The intensity of competition between plants for nutrients can vary spatiotemporally (Caffaro et al, 2013); this can alter the temporal dynamics of nitrogen accumulation (Schofield et al, 2019) when plants are in competition compared to isolation, with potential consequences for the temporal dynamics of soil microbial community enzyme activity. The temporal dynamics of nitrogen and biomass accumulation have been studied in barley (Hordeum vulgare) (Schofield et al, 2019). A delay in peak nitrogen uptake was found when the Proctor cultivar was grown in intra-cultivar competition but not inter-cultivar competition.…”

Temporal differentiation of resource capture and biomass accumulation as a driver of yield increase in intercropping

“…The study of Trinder et al (2012) was conducted with perennial grassland species, and annual crop species might react differently to neighbor presence. For example, a study using two barley cultivars – one early and one late - grown as isolated single plants and in either intra- or inter-specific competition (Schofield et al 2019b) found peak N accumulation was advanced by 0.5 days for the early and delayed by 14.5 days for the late cultivar when in intra-specific competition, while no shifts were observed in inter-specific competition. This suggests crop species may have enough temporal plasticity to avoid competition with kin but not with other species.…”