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E. Sayad 2010. Nitrogen retranclocation in pure and mixed plantations of Populus deltoides and Alnus subcordata
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Nitrogen retranclocation in pure and mixed plantations of Populus
deltoides and Alnus subcordata
Ehsan Sayad *
Natural Resources Faculty, Higher Education Complex of Behbahan, Iran
Abstract
Nutrients allocated to green leaves are recycled through 4 parallel pathways: herbivory,
throughfall, foliar resorption and litter decomposition. Nutrients recycled trough each pathway
may be of similar magnitude. Populus deltoides and Alnus subcordata were planted in five
proportions (100P, 67P:33A, 50P:50A, 33P:67A, 100A) in Noor, Iran. After 7 years, the effects
of species interactions on nutrient retranslocation were assessed. Leaves were collected from the
bottom one-third of the tree. Six representative trees (two near the center of sub-plot and one in
each corner of it) of each species were sampled for fully expanded leaves. Senescent leaves
were also collected from each species in each sub-plot. The Nitrogen retranslocations of both
species were not significantly differed between the different proportions also it was not different
between the two species. Finally, it should be implied that nutrient retranslocation was not
differed as a result of mixing these species at this age.
Keywords: Mixed plantations, Nutrient Retranslocation, Nitrogen fixing tree
1. Introduction
Tree plantations with different purposes are widespread activity all over the world. Almost all
the industrial plantations are monocultures, and questions are being raised about the
sustainability of their growth and their effects on the site (Khanna 1997). Poplars (Populus L.
spp.) are preferred plantation species, because their fast growth is expected to meet the
extensive demands of wood for poles, pulp and fuel (Kiadaliri 2003; Ghasemi 2000; Ziabari
1993). Repeated harvesting of fast-growing trees such as poplar plantations on short rotations
may deplete site nutrients.
Nitrogen losses are likely to be very important for future growth. Therefore, it is appropriate to
explore new systems of plantation management in which N may be added via fixation (Khanna
1997). Mixed plantation systems seem to be the most appropriate for providing a broader range
of options, such as production, protection, biodiversity conservation, and restoration
(Montagnini et al. 1995; Keenan et al. 1995; Guariguata et al. 1995; Parrotta and Knowles
1999).
Nutrients allocated to green leaves are recycled through 4 parallel pathways: herbivory (feces
and dead bodies), throughfall, foliar resorption and litter decomposition. Research often focuses
exclusively on decomposition, but the fraction of nutrients recycled trough each pathway may
be of similar magnitude. This fraction varies with the nutrient considered, the species and the
climatic conditions. For example, leaf nitrogen recycling is estimated to be 10% through
herbivory, 5% through throughfall, 40% through resorption and 45% through litterfall and
subsequent decomposition. Locally, the chemical and physiological characteristics of leaves
* Corresponding author. Tel.: +989161425493 - Fax: +98(671)2231662
Email address: ehsansaiad@yahoo.com
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.