Graefe, S.; Hertel, D. & Leuschner, C. (2010): <b>N, P and K limitation of fine root growth along an elevation transect in tropical mountain forests</b>. <i>Acta Oecologica</i> <b>36</b>, 537-542.
Resource Description
Title:
N, P and K limitation of fine root growth along an elevation transect in tropical mountain forests
FOR816dw ID:
1271
Publication Date:
2010-09-01
License and Usage Rights:
PAK 823-825 data user agreement. (www.tropicalmountainforest.org/dataagreementp3.do)
It is generally assumed that tree growth in tropical low-elevation forests is primarily limited by phosphorus<br/>
while nitrogen limitation is more prominent in tropical montane forests where temperature is<br/>
lower and the soils are poorly developed. We tested this hypothesis in mountain rainforests of South<br/>
Ecuador by investigating the growth response of tree fine roots to N, P and K fertilization in ingrowth cores<br/>
exposed at 1050 m (pre-montane) and 3060 m (upper montane) elevation. Root growth into unfertilized<br/>
ingrowth cores (control treatment) was about 10 times slower at 3060 m than at 1050 m. At 1050 m, root<br/>
growth was stimulated not only by P, but also by N and K. In contrast, N was the only element to promote<br/>
root growth at 3060 m. The N concentration in fine root biomass dropped to nearly a third between 1050<br/>
and 3060 m, those of P, K, Ca and Mg decreased as well, but to a lesser degree. According to a 15NO3<br/>
15NH4<br/>
tracer study along the slope, tree fine roots accumulated nitrate and ammonium in root biomass at similar<br/>
rates between 1050 and 3060 m, despite lower temperatures higher upslope.We conclude that the nature<br/>
of nutrient limitation of tree fine root growth changes with elevation from an apparent co-limitation by<br/>
P together with N and K at 1050 m to predominant N limitation at 3060 m, which is also reflected by low<br/>
foliar N concentrations. Increasing N limitation may have caused the high fine root biomass and root/shoot<br/>
ratio in the high elevation forest, while the capability of the roots to acquire mineral N apparently was not<br/>
affected by lower temperatures at high elevations.
Keywords:
| nitrogen | phosphorus | potassium | nutrient limitation | ecuador | fine roots | 15N tracer study |
