Global patterns of root turnover for terrestrial ecosystems

Abstract

Root turnover is a critical component of ecosystem nutrient dynamics and carbon sequestration and is also an important sink for plant primary productivity. We tested global controls on root turnover across climatic gradients and for plant functional groups by using a database of 190 published studies. Root turnover rates increased exponentially with mean annual temperature for fine roots of grasslands (r# l 0.48) and forests (r# l 0.17) and for total root biomass in shrublands (r# l 0.55). On the basis of the best-fit exponential model, the Q "! for root turnover was 1.4 for forest small diameter roots (5 mm or less), 1.6 for grassland fine roots, and 1.9 for shrublands. Surprisingly, after accounting for temperature, there was no such global relationship between precipitation and root turnover. 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. To test whether global relationships can be used to predict interannual variability in root turnover, we evaluated 14 yr of published root turnover data from a shortgrass steppe site in northeastern Colorado, USA. At this site there was no correlation between interannual variability in mean annual temperature and root turnover. Rather, turnover was positively correlated with the ratio of growing season precipitation and maximum monthly temperature (r# l 0.61). We conclude that there are global patterns in rates of root turnover between plant groups and across climatic gradients but that these patterns cannot always be used for the successful prediction of the relationship of root turnover to climate change at a particular site.

Steady state turnover time of carbon in the Australian terrestrial biosphere

“…These turnover times were about 7, 10 and 30 years for 0 -20, 20 -50 and 50 -100 cm depths, respectively (Table 3). Similar average lifetimes of root biomass between biomes in Australia irrespective of their productivity, is consistent with the results of Gill and Jackson [2000] who found no relationship globally between root turnover times and precipitation. In Australia, precipitation (through soil moisture balance) is the primary determinant of NPP.…”

Mycorrhizal Hyphal Turnover as a Dominant Process for Carbon Input into Soil Organic Matter

“…All roots were removed from the soil, washed, dried and weighed. Root turnover was determined as a ratio between annual production and maximum standing crop (Dahlman and Kucera, 1965;Gill and Jackson, 2000).…”

Distribution of roots and arbuscular mycorrhizal associations in tropical forest types of Xishuangbanna, southwest China

“…Although it is important to understand the rooting and mycorrhizal patterns of individual plant species, it is equally important to identify root and mycorrhizal patterns among plant functional types and across large climatic gradients (Gill and Jackson, 2000). Understanding differences in the distribution of roots and mycorrhizas between different forest types might be helpful in modeling the changes in root and mycorrhizal characteristics that influence the standing vegetation, nutrient availability and nutrient dynamics.…”