Biology subjects

Takimoto, G.

Publications and source records attributed to Takimoto, G..

3 recordsLinked to original sources

bioRxiv2022

Abrupt shifts in the plant species richness and community composition along an aridity gradient in the Mongolian grasslands

Aridity, edaphic variables related to aridity, and livestock grazing are major drivers of plant community composition across dryland grasslands. With accounting these factors, little is known about differences in determinants and changing patterns along aridity gradients with different average of aridity. Thus, the comparative investigations of communities without and with grazing in semi-arid and arid regions are suitable to clarify the difference in compositional responses along aridity gradients between potential vegetations and degraded ones with grazing. We investigated compositional changes of communities without/with grazing in semi-arid (north) /arid (south) regions across Mongolia. The compositional changes based on Bray-Curtis dissimilarity were investigated by generalized dissimilarity modeling, including geographic distance, aridity, soil pH, and sand and clay contents as independent variables. The determinants and changing patterns of community composition were compared among the four groups. Aridity had significant impacts on community composition regardless of the regions and the absence/presence of grazing. However, without the dependency on grazing, the difference in response patterns was observed between the regions. The compositional change was steeper especially at the upper edge of aridity rather than the lower edge in the arid region. This indicates the vulnerability of plant communities to aridity shifts due to future climate change in desert steppe of Mongolia. In addition, regardless of the regions, the effects of soil pH on community composition were eliminated by grazing. Because soil pH indirectly affected by aridity shifts can have impacts on community composition of potential vegetations without grazing, the long-term monitoring of vegetation dynamics needs observations of both of communities without and with grazing.

ecology↗

bioRxiv2019

Timing and duration of phenological subsidies: toward a mechanistic understanding of impacts on community structure and ecosystem processes in stream food chains

Phenological resources are common across many ecological communities, and can strongly affect community dynamics. Recent field manipulation experiments in stream food chains found that seasonal timing and duration of terrestrial prey inputs affected the feeding behavior, growth, and maturation of fish predators, caused predator-mediated indirect effects on aquatic prey, and modified trophic-cascading effects on litter processing. These experiments described impacts of resource phenological changes over a few month period, and long-term impacts of continued changes in resource phenology are unknown. Here we develop a mathematical model to extrapolate long-term predictions about the effects of changes in resource phenology from the results of field manipulation experiments. The model predicts that advanced timing generally decreases aquatic prey and litter processing and prolonged duration will either increase or decrease aquatic prey and litter processing depending on the total amount and pre-disturbed timing and duration of terrestrial prey inputs. Importantly, our modeling approach clarifies the mechanisms by which stage-specific responses of life history processes in fish, such as growth, maturation, and reproduction, respond to phenological changes in terrestrial prey inputs and mediate indirect effects on aquatic prey and litter processing. Stage-specific responses of life history processes are an integral part of the mechanisms with which to predict the consequences of phenological species interactions at the community and ecosystem levels.

ecology↗

bioRxiv2019

The effects of resource subsidy duration on detritus-based stream ecosystems: a stream mesocosm experiment

Most of the resource subsidies are temporally variable, and studies have revealed that ecological processes can be mediated by the temporal attributes of subsidies, such as timing and frequency. Less studies have, however, examined the effects of the subsidy duration, an another major temporal attribute, on consumer populations, communities and ecosystem functions. Using an outdoor mesocosm experiment, we demonstrated that, even with the same total amounts, the prolonged subsidy let large-stage fish effectively monopolize the subsidy over small-stage fish, while the pulsed subsidy allowed small-stage fish to increase the ingestion rate of the subsidy. This effect resulted in causing weaker indirect positive effects on in-situ benthic prey and a leaf breakdown rate with the prolonged subsidy than with the pulsed-subsidy although it depended on dominant benthic prey species having different edibility. Increasing evidences have shown that global warming would not only advance, but also prolong the growing seasons, which may, in turn, make subsidies more prolonged. The ecological significance of the subsidy duration might be common in nature, and should be incorporated to better understand ecological processes in spatially and temporally coupled ecosystems.

ecology↗