Abstract:
Tropical montane forests of the Andes belong to the hotspots of biodiversity. But these nutrient poor ecosystems are simultaneously threatened by increased element inputs of nitrogen and phosphor in nutrient cycles. NUMEX-Projekt simulates the expected nutrient inputs in the for-ests and quantifies the changes of this ecosystem. In line of this study litter samples were collected by littertraps during a working period from February till May 2016. Leaf litter produc-tion, parameters of leaf morphology (leaf area and specific leaf area) and litter nutrients of nitrogen and phosphor were determined. Additionally, the parameters of herbivory (leaf mass loss and leaf area loss) were calculated by measuring holes area. The variation of these pa-rameters along an altitudinal gradient from 1.000 m.a.s.l. to 3.000 m.a.s.l. was investigated. Besides the variation after nitrogen and/or phosphor addition was explored. Furthermore, the extend of nutrients, lost through herbivory, was identified for the stand level. Terminatory the influence of two soil parameters (C/N ratio and Presin) was discussed.
There is a significant influence of altitude (p<0,05) on leaf morphology (leaf area: 1.000 m.a.s.l: 26,4±1,6 cm², 3.000 m.a.s.l: 7,4±1,0 cm², specific leaf area: 1.000 m.a.s.l: 99,7±4,1 cm²·g-1, 3.000 m.a.s.l: 56,1±6,6 cm²·g-1), leaf nutrients of nitrogen (1.000 m.a.s.l: 15,3±0,5 g·kg-1, 3.000 m.a.s.l: 6,6±0,7 g·kg-1) and phosphor (1.000 m.a.s.l: 0,54±0,03 g·kg-1, 3.000 m.a.s.l: 0,25±0,03 g·kg-1) and also on the parameters of herbivory: holes area (1.000 m.a.s.l: 1,8±0,2 cm², 3.000 m.a.s.l: 0,3±0,1 cm²) and leaf area loss (1.000 m.a.s.l: 6,8±0,4 %, 3.000 m.a.s.l: 3,6±0,6 %).
Nutrient addition did not lead to distinct results according to the variation of measured param-eters. NP fertilization had a positive effect on leaf area and P fertilization a positive effect on specific leaf area. Leaf nutrients showed various answers. For this parameter, NP fertilization causes significantly raised nitrogen and phosphor concentrations in litter in each site. Leaf litter production in 1.000 m.a.s.l site significantly decreased through NP fertilization. Referring to herbivory only a little number of significant effects were detected. Holes area increased on 2.000 m.a.s.l site by NP addition while leaf area loss in 1.000 m.a.s.l site – as well as leaf area production – decreased. On stand level, there was no variation of leaf area loss.
Soil parameters have a higher impact on measured parameters on stand level. Specific leaf area and leaf area loss correlate positively with soil C/N of upper mineral soil. Correlations of these parameters with plant available phosphor Presin is negative.
Nutrient losses on stand level decrease with altitude. There was a negative effect of NP addition on nitrogen loss in 1.000 m.a.s.l site and a positive effect of NP addition on phosphor loss in all sites.
