Forget about Plants v Zombies, what’s happening in Trees v Vines?
Bill Laurance of James Cook University in Cairns, Australia, interviewed on Science Friday, tells us how in the world’s rainforests, the age-old battle between vines and the trees that host them is starting to shift – and the vines are winning.
Logging is one of the human-created conditions that are favouring the vines. As trees are felled and the canopy disturbed, vines exposed to light put on a huge growth spurt. As well, new sapling trees with their lower branching provide handy, reachable trellises to support new vine growth. The forest quickly changes from one of tall growing canopy trees to a lower, stunted and more open version
Logging also fragments forests into smaller parcels, making more forest edges. In these high light conditions and without surrounding trees to provide competition for nutrients and water, vines quickly swamp edge-growing trees.
But vines are also increasing in undisturbed forests, which Laurance attributes to worldwide elevated CO2 levels. Although both trees and vines grow faster in higher CO2, vine growth seems to be more favoured. This could be because quickly growing trees compete even more with each other for water and nutrients. This leads to the forest becoming more dynamic, where trees both grow and die faster, leading to a higher turnover and more room for vines to take over. And of course as trees die, they release even more CO2 as they decompose.
Although many trees have defences against vines, like bark and limb shedding or even hosting predatory ants that attack epiphytes as they try to establish, the vines are winning the war.
Listen to the fascinating full interview with Bill Laurance at Science Friday