Eurasian species respond to climatic changes were very individual. There was a global decline in terrestrial N availability over Holocene due to N being locked up in tree biomass (McLauchlan et al 2013)
There were bottom up drivers of change during the LGM -Holocene period through changing climate and atmosphere, which then affected vegetation and then megafauna. There were top-down controls via megafaunal hunting. Can we separate these?
Looks are British and Irish ecosystem dynamics from two lakes, during the period of woody encroachment at the glacial-Holocene transition
Lough Nadourcan: heathlands transition to birch woodland
Megaherbivore biomass increased (dung fungi), increase in biomass, decline in N availability. Birch consumed more by large herbivores and susceptible to burning, but does end up locking up N. For birch biomass, climate was most important, for the heathlands herbivore biomass was most important.
Quidenham Mere: grasslands to deciduous woodlands
Herbivore biomass decreased, decrease in fire. N availability also increased. The abiotic factors were most important but herbivore biomass contribution to that interaction.
Any evidence of direct impact of large herbvores on N availability? Negative relationship in herbivores, were site was dominated by cervods In English site there was a positive relationship, and there was a much more diverse assemblage of herbivores.
Conclusions
Guild-specific response of herbivores to woody plant encroachment
Climate and fire were direct drivers of tree expansion, herbivores had indirect effects
Impacts of herbivores on N availability depends on herbivore assemblage, soil properties (a finding similar to Elisabeth Bakker earlier). No simple generic relationship between herbivory and nutrient supply.
There were bottom up drivers of change during the LGM -Holocene period through changing climate and atmosphere, which then affected vegetation and then megafauna. There were top-down controls via megafaunal hunting. Can we separate these?
Looks are British and Irish ecosystem dynamics from two lakes, during the period of woody encroachment at the glacial-Holocene transition
Lough Nadourcan: heathlands transition to birch woodland
Megaherbivore biomass increased (dung fungi), increase in biomass, decline in N availability. Birch consumed more by large herbivores and susceptible to burning, but does end up locking up N. For birch biomass, climate was most important, for the heathlands herbivore biomass was most important.
Quidenham Mere: grasslands to deciduous woodlands
Herbivore biomass decreased, decrease in fire. N availability also increased. The abiotic factors were most important but herbivore biomass contribution to that interaction.
Any evidence of direct impact of large herbvores on N availability? Negative relationship in herbivores, were site was dominated by cervods In English site there was a positive relationship, and there was a much more diverse assemblage of herbivores.
Conclusions
Guild-specific response of herbivores to woody plant encroachment
Climate and fire were direct drivers of tree expansion, herbivores had indirect effects
Impacts of herbivores on N availability depends on herbivore assemblage, soil properties (a finding similar to Elisabeth Bakker earlier). No simple generic relationship between herbivory and nutrient supply.