Abstract:
We analyzed the stocks of Ca, Mg, P, and S in tree rings of Cedrela montana Moritz ex Turcz in order to evaluate the dynamics of element input to a lower montane rain forest in South Ecuador. Samples were taken by a Pressler drill from the living tree (n=5). Afterwards tree rings were separated and digested with concentrated HNO3 under pressure (Heinrichs et al.,1986). Concentrations of Ca and Mg were determined by atomic absorption spectroscopy (AAS), concentrations of P and S by inductively coupled plasma optical emission spectrometry (ICP-OES), respectively. Mean element concentrations in tree rings between 1957 and 2005 were 2.2 g kg-1 for Ca, 1.1 g kg-1 for P and S and 0.4 g kg-1 for Mg. Radial distribution of element concentrations was heterogeneous with exception of the tree rings close to the phloem, where concentrations were generally higher. The pattern of annual radial increment showed significant growth peaks related to strong La Niña events. Also concentrations of P and S peaked during the La Niña events of 1989, 1996, and 2000. For Ca and Mg a similar effect was observed with a time shift of one year. Highest Ca peaks during the monitored period were associated with the 1974 La Niña event, which was also the strongest event on the record. We conclude that tree rings are a suitable tool for recording element inputs of Ca, Mg, P, and S at lower montane rain forests of South Ecuador. Furthermore we found element inputs and growth signals linked to the ENSO cycle.
