The accuracy of matrix population model projections for coniferous trees in the Sierra Nevada, California
Article first published online: 3 MAY 2005
Journal of Ecology
Volume 93, Issue 4, pages 737–747, August 2005
How to Cite
VAN MANTGEM, P. J. and STEPHENSON, N. L. (2005), The accuracy of matrix population model projections for coniferous trees in the Sierra Nevada, California. Journal of Ecology, 93: 737–747. doi: 10.1111/j.1365-2745.2005.01007.x
- Issue published online: 3 MAY 2005
- Article first published online: 3 MAY 2005
- Received 12 October 2004, revision accepted 25 January 2005 Handling Editor: Hans de Kroon
- growth autocorrelation;
- matrix models;
- population projections;
- size structure;
- tree demography
- 1We assess the use of simple, size-based matrix population models for projecting population trends for six coniferous tree species in the Sierra Nevada, California. We used demographic data from 16 673 trees in 15 permanent plots to create 17 separate time-invariant, density-independent population projection models, and determined differences between trends projected from initial surveys with a 5-year interval and observed data during two subsequent 5-year time steps.
- 2We detected departures from the assumptions of the matrix modelling approach in terms of strong growth autocorrelations. We also found evidence of observation errors for measurements of tree growth and, to a more limited degree, recruitment. Loglinear analysis provided evidence of significant temporal variation in demographic rates for only two of the 17 populations.
- 3Total population sizes were strongly predicted by model projections, although population dynamics were dominated by carryover from the previous 5-year time step (i.e. there were few cases of recruitment or death). Fractional changes to overall population sizes were less well predicted. Compared with a null model and a simple demographic model lacking size structure, matrix model projections were better able to predict total population sizes, although the differences were not statistically significant. Matrix model projections were also able to predict short-term rates of survival, growth and recruitment. Mortality frequencies were not well predicted.
- 4Our results suggest that simple size-structured models can accurately project future short-term changes for some tree populations. However, not all populations were well predicted and these simple models would probably become more inaccurate over longer projection intervals. The predictive ability of these models would also be limited by disturbance or other events that destabilize demographic rates.