engleski

Differential response of ten poplar clones to fertilization and climate effects at low groundwater table

The building of new river dams for electricity production resulted in severe changes of water regime in the basin of Drava River (a tributary to Danube), stretching through Italy, Austria, Slovenia, Hungary and from northwest to northeast of Croatia. Large areas of ecologically very valuable forests are exposed to the significant lowering of the groundwater table along the river derivation channels, resulting in severe dieback, growth depression and poor natural regeneration of riparian tree species. The urgent need for selected genetic material adapted to specific conditions of alluvial soils with low groundwater levels is accompanied by the lack of a clear view on the future forest and environmental management of riparian ecosystems damaged by urban development. The trial of 10 poplar clones (6 P. deltoides clones, 2 P. x euramericana clones and 1 clone each of P. nigra and P. alba) was established in the year 2001 next to one of the derivation channels. In 2004 and 2005, a fertilization experiment was incorporated into the existing trial to test the response of clones to four nitrogen (N) fertilizer doses added annually: 0, 100, 200 and 300 kgN/ha. P and K were given uniformly on the whole experimental area at 100 at 150 kg/ha, respectively. The response of height and diameter increment percentages differed significantly among clones and N treatments, indicating insufficient, adequate or excessive N fertilization. The mass of leaves (mL) and foliar concentrations of N, S, P, K, Ca and Mg, content of N (mN), and ratios of mineral elements (particularly N/Ca) were used to explain these differences. Climate differences between 2004 and 2005 were an additional source of variability, influencing both nutrition and growth of clones.

water regime; adaptation; nutrition; growth

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