Microbial biomass and N mineralization in mixed plantations of broadleaves and nitrogen-fixing species

E L Pereira,M.S Patricio,S.A.P Santos,M Arrobas

doi:10.5424/fs/20112003-11458

E L Pereira, M.S Patricio + Show 2 more

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https://doi.org/10.5424/fs/20112003-11458

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Journal: Forest Systems	Publication Date: Dec 4, 2011
Citations: 10	License type: cc-by

Affiliation: Polytechnic Institute of Bragança

Abstract

Mixed stands with nitrogen fixing secondary species can improve the vigour and the stand environment of the targeted species. The aim of this study was to better understand the effect of the consociation of a N-fixing species (black locust) with a broadleaf quality timber production (wild cherry). The study was conducted in 11 year old plantations located in the Northeast of Portugal. The treatments considered were: pure black locust, pure wild cherry and mixture of wild cherry and black locust. Each plot had six lines with 12 trees and a buffer strip line. The samplings were collected on the plantation line within a radius of 50 to 100 cm from the tree. In each plot we measured soil N mineralization dynamic, soil microbial biomass carbon (MBC) and nitrogen (MBN), microbial quotient (MBC/Corg), metabolic quotient (qCO2), microbial respiration and dehydrogenase activity. Results showed a positive impact of the black locust species on the supply of nitrogen to the soil. The net N-mineralization rates were, at the end of this study, about three times greater in the pure black locust than in the pure wild cherry and about two times greater in the mixture than in the pure wild cherry. MBC and cumulative soil respiration were higher in the mixture than in the pure cherry plantation soil which may reflect positive changes in the soil environment.

Highlights

In Portugal, the forestation of set aside agricultural lands (EU reg. 2080/92) brought new challenges to agroforestry land use increasing the possibility of production of valuable broadleaves tree species
Physical and chemical soil properties registered in bulk soil were very similar in all the experimental treatments. In these eleven year old mixed plantations, it seems that the black locust still has no significant effects on those soil properties
Low C/N ratios and organic matter contents were found by Fonseca et al (2002) in one young stand of black locust in the Northeast of Portugal when compared to other species (Cupressus lusitanica Miller and several land shrubs)

Summary

Introduction

In Portugal, the forestation of set aside agricultural lands (EU reg. 2080/92) brought new challenges to agroforestry land use increasing the possibility of production of valuable broadleaves tree species. 2080/92) brought new challenges to agroforestry land use increasing the possibility of production of valuable broadleaves tree species. Wild cherry (Prunus avium L.) is one of these promising species for high quality wood production. There is an increasing interest in the wood of this species which can attain high prices in the markets. In Portugal, until the nineties the wild cherry was practically ignored in afforestations. The oldest stands, mostly pure, are about sixteen years old and many of them are experiencing a high rate of mortality, gum pockets and low vigour. These problems are not generally observed in the situation where cherry grows naturally in mixtures under similar site conditions. We think the stand environment, the cultural practices and the genetic factors are major issues both for vigour of the species and quality of the timber

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