Herbivory-induced mortality increases with radial growth in an invasive riparian phreatophyte

K. R. Hultine, T. L. Dudley, Steven Leavitt

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Background and Aims Under equal conditions, plants that allocate a larger proportion of resources to growth must do so at the expense of investing fewer resources to storage. The critical balance between growth and storage leads to the hypothesis that in high-resource environments, plants that express high growth rates are more susceptible to episodic disturbance than plants that express lower growth rates. Methods This hypothesis was tested by measuring the radial growth, basal area increment (BAI) and carbon isotope ratios (δ13C) in tree-ring cellulose of 62 mature tamarisk trees (Tamarix spp.) occurring at three sites in the western USA (n = 31 live and 31 killed trees across all sites, respectively). All of the trees had been subjected to periods of complete foliage loss by episodic herbivory over three or more consecutive growing seasons by the tamarisk leaf beetle (Diorhabda carinulata), resulting in approx. 50% mortality at each site. Key Results Mean annual BAI (measured from annual ring widths) in the 10 years prior to the onset of herbivory was on average 45% higher in killed trees compared with live trees (P < 0.0001). Killed trees that had higher growth rates also expressed higher (less negative) δ13C ratios compared with live trees. In fact, at one site near Moab, UT, the mean annual BAI was 100% higher in killed trees despite having about a 0.5 ‰ higher δ13C relative to live trees (P = 0.0008). Patterns of δ13C suggest that the intrinsic water-use efficiency was higher in killed than surviving trees, possibly as a consequence of lower whole-canopy stomatal conductance relative to live trees. Conclusions The results show that a likely trade-off occurs between radial growth and survival from foliage herbivory in Tamarix spp. that currently dominates riparian areas throughout the western USA and northern Mexico. Thus, herbivory by D. carinulata may reduce the overall net primary productivity of surviving Tamarix trees and may result in a reduction in genetic variability in this dominant invasive tree species if these allocation patterns are adaptive.

Original languageEnglish (US)
Pages (from-to)1197-1206
Number of pages10
JournalAnnals of Botany
Volume111
Issue number6
DOIs
StatePublished - Jun 2013

Fingerprint

herbivores
Tamarix
basal area
riparian areas
growth rings
Chrysomelidae
water use efficiency
stomatal conductance
primary productivity
leaves
isotopes
cellulose
Mexico
growing season
canopy
genetic variation
carbon

Keywords

  • Diorhabda carinulata
  • Plant mortality
  • riparian ecosystems
  • Tamarix
  • tree ring growth
  • tree-ring δC

ASJC Scopus subject areas

  • Plant Science

Cite this

Herbivory-induced mortality increases with radial growth in an invasive riparian phreatophyte. / Hultine, K. R.; Dudley, T. L.; Leavitt, Steven.

In: Annals of Botany, Vol. 111, No. 6, 06.2013, p. 1197-1206.

Research output: Contribution to journalArticle

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N2 - Background and Aims Under equal conditions, plants that allocate a larger proportion of resources to growth must do so at the expense of investing fewer resources to storage. The critical balance between growth and storage leads to the hypothesis that in high-resource environments, plants that express high growth rates are more susceptible to episodic disturbance than plants that express lower growth rates. Methods This hypothesis was tested by measuring the radial growth, basal area increment (BAI) and carbon isotope ratios (δ13C) in tree-ring cellulose of 62 mature tamarisk trees (Tamarix spp.) occurring at three sites in the western USA (n = 31 live and 31 killed trees across all sites, respectively). All of the trees had been subjected to periods of complete foliage loss by episodic herbivory over three or more consecutive growing seasons by the tamarisk leaf beetle (Diorhabda carinulata), resulting in approx. 50% mortality at each site. Key Results Mean annual BAI (measured from annual ring widths) in the 10 years prior to the onset of herbivory was on average 45% higher in killed trees compared with live trees (P < 0.0001). Killed trees that had higher growth rates also expressed higher (less negative) δ13C ratios compared with live trees. In fact, at one site near Moab, UT, the mean annual BAI was 100% higher in killed trees despite having about a 0.5 ‰ higher δ13C relative to live trees (P = 0.0008). Patterns of δ13C suggest that the intrinsic water-use efficiency was higher in killed than surviving trees, possibly as a consequence of lower whole-canopy stomatal conductance relative to live trees. Conclusions The results show that a likely trade-off occurs between radial growth and survival from foliage herbivory in Tamarix spp. that currently dominates riparian areas throughout the western USA and northern Mexico. Thus, herbivory by D. carinulata may reduce the overall net primary productivity of surviving Tamarix trees and may result in a reduction in genetic variability in this dominant invasive tree species if these allocation patterns are adaptive.

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