Abstract Detail


Laughlin, Daniel [1].

The afterlives of plants: root decomposition rates of New Zealand tree species are driven by traits on the conservation gradient.

Fine root traits have recently been shown to span two independent axes of variation that delineate a root economic space. The first axis is a trade-off between root diameter and specific root length, where thick-rooted species are associated with greater mycorrhizal colonization, whereas thin-rooted species are associated with a do-it-yourself strategy of nutrient acquisition. The second axis is a trade-off between root tissue density and nitrogen concentration, where conservative species exhibit dense longer-lived roots and acquisitive species exhibit faster metabolic rates. These axes influence rates of resource acquisition, but many questions remain about how these axes of trait variation affect ecosystem functions, especially rates of decomposition that are critical to carbon and nutrient cycling. I predicted that low density tissue with high root nitrogen should lead to faster decomposition rates. I measured decomposition rates of 63 indigenous tree species in Aotearoa New Zealand in a common garden setting. Three replicates per species were placed in mesh bags and percent mass loss was measured after 6 months. Decomposition rate was significantly phylogenetically conserved (lambda=0.71, P<0.0001), exhibiting slower rates in podocarps and southern beech species and faster rates in laurels and asterids. The conservation axes was most strongly correlated with decomposition rates: root tissue density was negatively correlated (P<0.0001) and root nitrogen was positively correlated with decomposition rate (P<0.0001). However, a phylogenetically informed regression indicated that root diameter was also positively correlated with decomposition rates (P<0.01). The strongest predictor of decomposition rate was the lignin-to-N and lignin-to-P ratios, where species with the most labile carbon decomposed the fastest. These results suggest that decomposition rate is driven by more than just the conservation gradient alone, and that the collaboration gradient may also be influencing decomposition, possibly due to large-rooted species obtaining access to nutrients through mycorrhizal collaboration. It is also clear that traits beyond the four core traits that delineate the root economic space must be considered when modeling belowground decomposition rates. The traits of fine roots determine their fate in the afterlife.

1 - University Of Wyoming, Department Of Botany, 1000 E University Ave, Laramie, WY, 82071, United States

economic spectrum
fine root
temperate rainforest
ecosystem function
phylogenetic conservatism
plant traits.

Presentation Type: Oral Paper
Number: EC12004
Abstract ID:161
Candidate for Awards:None

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