TY - JOUR
T1 - Time-lagged effects of weather on plant demography
T2 - drought and Astragalus scaphoides
AU - Tenhumberg, Brigitte
AU - Crone, Elizabeth E.
AU - Ramula, Satu
AU - Tyre, Andrew J.
N1 - Funding Information:
The authors thank the 2016 Global Analysis of Plant and Animal Demography Workshop funded by the International Opportunity Development Fund, Natural Environment Research Council, for the opportunity to initiate this work. B. Tenhumberg was financially supported by the National Science Foundation (DEB 1655117), A. J. Tyre was supported by the Nebraska Agricultural Experiment Station, and S. Ramula was supported by the Academy of Finland (#285746). We would like to acknowledge that our study sites are on the traditional territory of the Blackfoot (Montana) and Shoshoni (Idaho) tribes.
Publisher Copyright:
© 2018 by the Ecological Society of America
PY - 2018/4
Y1 - 2018/4
N2 - Temperature and precipitation determine the conditions where plant species can occur. Despite their significance, to date, surprisingly few demographic field studies have considered the effects of abiotic drivers. This is problematic because anticipating the effect of global climate change on plant population viability requires understanding how weather variables affect population dynamics. One possible reason for omitting the effect of weather variables in demographic studies is the difficulty in detecting tight associations between vital rates and environmental drivers. In this paper, we applied Functional Linear Models (FLMs) to long-term demographic data of the perennial wildflower, Astragalus scaphoides, and explored sensitivity of the results to reduced amounts of data. We compared models of the effect of average temperature, total precipitation, or an integrated measure of drought intensity (standardized precipitation evapotranspiration index, SPEI), on plant vital rates. We found that transitions to flowering and recruitment in year t were highest if winter/spring of year t was wet (positive effect of SPEI). Counterintuitively, if the preceding spring of year t − 1 was wet, flowering probabilities were decreased (negative effect of SPEI). Survival of vegetative plants from t − 1 to t was also negatively affected by wet weather in the spring of year t − 1 and, for large plants, even wet weather in the spring of t − 2 had a negative effect. We assessed the integrated effect of all vital rates on life history performance by fitting FLMs to the asymptotic growth rate, log(λt). Log(λt) was highest if dry conditions in year t − 1 were followed by wet conditions in the year t. Overall, the positive effects of wet years exceeded their negative effects, suggesting that increasing frequency of drought conditions would reduce population viability of A. scaphoides. The drought signal weakened when reducing the number of monitoring years. Substituting space for time did not recover the weather signal, probably because the weather variables varied little between sites. We detected the SPEI signal when the analysis included data from two sites monitored over 20 yr (2 × 20 observations), but not when analyzing data from four sites monitored over 10 yr (4 × 10 observations).
AB - Temperature and precipitation determine the conditions where plant species can occur. Despite their significance, to date, surprisingly few demographic field studies have considered the effects of abiotic drivers. This is problematic because anticipating the effect of global climate change on plant population viability requires understanding how weather variables affect population dynamics. One possible reason for omitting the effect of weather variables in demographic studies is the difficulty in detecting tight associations between vital rates and environmental drivers. In this paper, we applied Functional Linear Models (FLMs) to long-term demographic data of the perennial wildflower, Astragalus scaphoides, and explored sensitivity of the results to reduced amounts of data. We compared models of the effect of average temperature, total precipitation, or an integrated measure of drought intensity (standardized precipitation evapotranspiration index, SPEI), on plant vital rates. We found that transitions to flowering and recruitment in year t were highest if winter/spring of year t was wet (positive effect of SPEI). Counterintuitively, if the preceding spring of year t − 1 was wet, flowering probabilities were decreased (negative effect of SPEI). Survival of vegetative plants from t − 1 to t was also negatively affected by wet weather in the spring of year t − 1 and, for large plants, even wet weather in the spring of t − 2 had a negative effect. We assessed the integrated effect of all vital rates on life history performance by fitting FLMs to the asymptotic growth rate, log(λt). Log(λt) was highest if dry conditions in year t − 1 were followed by wet conditions in the year t. Overall, the positive effects of wet years exceeded their negative effects, suggesting that increasing frequency of drought conditions would reduce population viability of A. scaphoides. The drought signal weakened when reducing the number of monitoring years. Substituting space for time did not recover the weather signal, probably because the weather variables varied little between sites. We detected the SPEI signal when the analysis included data from two sites monitored over 20 yr (2 × 20 observations), but not when analyzing data from four sites monitored over 10 yr (4 × 10 observations).
KW - carryover effects
KW - detecting weather signals
KW - drought
KW - environmental drivers
KW - matrix models
KW - plant demography
KW - space for time substitution
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U2 - 10.1002/ecy.2163
DO - 10.1002/ecy.2163
M3 - Article
C2 - 29380874
AN - SCOPUS:85042231696
SN - 0012-9658
VL - 99
SP - 915
EP - 925
JO - Ecology
JF - Ecology
IS - 4
ER -