Global patterns of root turnover evaluated for vegetation, climatic, and physiological variables.
GILL, R.A.*, J.LORETI and R.B.JACKSON
Duke University, Durham, NC 27708 1
Root turnover is a critical component of ecosystem nutrient dynamics and carbon sequestration, and is an important sink for plant primary productivity. We tested global patterns of root turnover for plant functional groups and across climatic gradients using a database of 150 published studies. The slowest average turnover rates were observed for entire tree root systems (10% annually), followed by 34% for shrubland total roots, 53% for grassland fine roots, 55% for wetland fine roots, and 56% for forest fine roots. Root turnover decreased from tropical to high-latitude systems for all plant functional groups. We also found that root turnover was highest for tree fine roots of very small diameter and decreased with increasing root diameter increment. Root turnover rates increased exponentially with mean annual temperature for fine roots of grasslands and forests and for total root biomass in shrublands. Surprisingly, after accounting for temperature, there was no such global relationship between precipitation and root turnover. We used a database of published studies to evaluate root respiration as a potential factor influencing root turnover with increasing temperature and root diameter. We found that root respiration increases with decreasing root diameter in trees and is positively correlated with temperature, potentially supporting the hypothesis that root longevity is controlled by within-plant carbon economy. The variability in data included in our study also indicate that refining methods of estimating root turnover and understanding site-specific characteristics will be important for fully understanding controls over root turnover.
Keywords: root turnover, root respiration, meta-analysis
This abstract is being presented at: 4:00 PM in session:
Oral Session #12: Roots.