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Stress‐tolerator leaf traits determine population dynamics in the endangered N ew C aledonian conifer A raucaria muelleri
Author(s) -
Enright Neal J.,
Miller Ben P.,
Perry George L. W.,
Goldblum David,
Jaffré Tanguy
Publication year - 2014
Publication title -
austral ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.688
H-Index - 87
eISSN - 1442-9993
pISSN - 1442-9985
DOI - 10.1111/aec.12045
Subject(s) - biology , seedling , survivorship curve , population , vital rates , endangered species , ecology , botany , population growth , demography , habitat , cancer , sociology , genetics
Demographic and ecophysiological data for the endangered N ew C aledonian conifer, A raucaria muelleri ( A raucariaceae), were analysed to: (i) evaluate population viability in relation to site conditions and human impacts; and (ii) advance our understanding of how stress‐tolerator plant functional traits affect the population dynamic behaviour and conservation requirements of long‐lived tree species. Growth, survivorship and recruitment in four A . muelleri populations were monitored across 9 years. Demographic rates were analysed using stage‐based transition matrices. Leaf δ 13 C , % N and photosystem II stress ( Fv / Fm ) were measured for seedlings, saplings and trees, and leaf mass per area ( LMA ) for trees, and correlations among ecophysiological and demographic variables explored. Seedling, sapling and tree stem growth were among the slowest, and annual survivorship among the highest, reported for any tree. Transition matrix analyses yielded stable estimated population growth rates, λ , not significantly different from 1.0 for all populations. Leaf δ 13 C was positively correlated with seedling and sapling height growth, while daytime photosystem II stress ( Fv / Fm ) was high in seedlings, but low in saplings and trees. Ecophysiological measures suggest that individuals transition from moisture‐limited growth at the seedling stage to nutrient‐limited growth as adults. High levels of environmental stress result in slow stand dynamics, characterized by low recruitment and growth rates counterbalanced by equally low mortality rates. These dynamics result in populations with limited capacity to increase in size quickly, but potentially highly vulnerable to decline should the rate of adult mortality increase. This combination of traits is likely typical of extreme stress‐tolerator woody species and suggests a conservation focus on the preservation of mature individuals.