Abstract
| Original language | English |
|---|---|
| Pages (from-to) | 2061-2071 |
| Number of pages | 11 |
| Journal | Journal of Biogeography |
| Volume | 39 |
| DOIs | |
| Publication status | Published - 2012 |
| Externally published | Yes |
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Causes of tree line stability: stem growth, recruitment and mortality rates over 15 years at New Zealand Nothofagus tree lines. / Harsch, Melanie; Buxton, Rowan; Duncan, Richard; Hulme, Philip; Wardle, Peter; Wilmshurst, Janet.
In: Journal of Biogeography, Vol. 39, 2012, p. 2061-2071.Research output: Contribution to journal › Article
TY - JOUR
T1 - Causes of tree line stability: stem growth, recruitment and mortality rates over 15 years at New Zealand Nothofagus tree lines
AU - Harsch, Melanie
AU - Buxton, Rowan
AU - Duncan, Richard
AU - Hulme, Philip
AU - Wardle, Peter
AU - Wilmshurst, Janet
PY - 2012
Y1 - 2012
N2 - Aim Abrupt tree lines are relatively rare world-wide and are poorly understood. We studied demographic processes at abrupt tree lines to better understand the factors governing their dynamics. Location Five Nothofagus-dominated tree line sites across the South Island, New Zealand. Methods All Nothofagus stems at or above the tree line were tagged and their spatial locations and heights recorded on three occasions over 15 years at each site. We estimated rates of stem height growth, recruitment and mortality, and used these data to evelop a demographic model to project stem numbers into the future. Results Stem numbers had increased above the tree line at most sites over the last 15 years, but with little evidence of tree line advance. Growth, mortality and recruitment rates, modelled as a function of stem size, showed variation through time and among sites. Using a demographic model to project the numbers of stems above tree line 15 years into the future suggests that stem number will continue to increase, but that these tree lines are unlikely to advance at the rate predicted by recent climate warming. Across sites, variation in the rate of change in the number of stems above the tree line was most strongly related to variation in recruitment rates. Main conclusions Forest expansion at the abrupt Nothofagus tree line in New Zealand appears to be limited primarily by a lack of recruitment of new stems, which may be due to a paucity of suitable sheltered microsites for seedling establishment. Based on past demographic rates, our results suggest that these tree lines are relatively unresponsive to recent climate warming and are unlikely to show substantial upslope movement if past demographic trends continue.
AB - Aim Abrupt tree lines are relatively rare world-wide and are poorly understood. We studied demographic processes at abrupt tree lines to better understand the factors governing their dynamics. Location Five Nothofagus-dominated tree line sites across the South Island, New Zealand. Methods All Nothofagus stems at or above the tree line were tagged and their spatial locations and heights recorded on three occasions over 15 years at each site. We estimated rates of stem height growth, recruitment and mortality, and used these data to evelop a demographic model to project stem numbers into the future. Results Stem numbers had increased above the tree line at most sites over the last 15 years, but with little evidence of tree line advance. Growth, mortality and recruitment rates, modelled as a function of stem size, showed variation through time and among sites. Using a demographic model to project the numbers of stems above tree line 15 years into the future suggests that stem number will continue to increase, but that these tree lines are unlikely to advance at the rate predicted by recent climate warming. Across sites, variation in the rate of change in the number of stems above the tree line was most strongly related to variation in recruitment rates. Main conclusions Forest expansion at the abrupt Nothofagus tree line in New Zealand appears to be limited primarily by a lack of recruitment of new stems, which may be due to a paucity of suitable sheltered microsites for seedling establishment. Based on past demographic rates, our results suggest that these tree lines are relatively unresponsive to recent climate warming and are unlikely to show substantial upslope movement if past demographic trends continue.
KW - Climate change
KW - demographic model
KW - dispersal
KW - growth
KW - mortality
KW - Nothofagus menziesii
KW - Nothofagus solandri
KW - recruitment
KW - Southern Alps
KW - tree line.
U2 - 10.1111/j.1365-2699.2012.02763.x
DO - 10.1111/j.1365-2699.2012.02763.x
M3 - Article
VL - 39
SP - 2061
EP - 2071
JO - Journal of Biogeography
JF - Journal of Biogeography
SN - 0305-0270
ER -