References of "Bazgir, Masoud"
     in
Bookmark and Share    
See detailNutrient fluxes and soil microbial processes
Bazgir, Masoud ULg

Doctoral thesis (2011)

Because of previous intense forest use and over exploitation in the past centuries, the plantation of coniferous stands, especially Norway spruce (Picea abies L. KARST.) with high production potentials ... [more ▼]

Because of previous intense forest use and over exploitation in the past centuries, the plantation of coniferous stands, especially Norway spruce (Picea abies L. KARST.) with high production potentials has been a common European afforestation strategy. However, the characteristics of Norway spruce such as susceptibility to windfall, forest dieback, drought, as well as soil acidification have caused negative ecological impacts in many sites. Conversion of conifers into deciduous or mixed stands has been suggested by some foresters, in order to improve the stability, ecology and biodiversity of forest ecosystems. Such changes in forest management require specific information on the impact of tree species on nutrient cycling, soil properties and microbial activities. In this study, six broadleaved species were growing at the same site with similar condition in terms of soil type, land use history and climate. Thus, the potential effects on biogeochemical cycling could be attributed to tree species. In this thesis, I focused on the effect of broadleaved species (conversion scenario) contrasting in terms of ecological characteristics (pioneer species versus main forestry species) and physiological characteristics (N2-fixing tree species (alder) versus non N2-fixing species) and Norway spruce (no conversion scenario) on (a) soil chemical properties (b) soil microbial activities and microbial biomass (c) nutrient input fluxes from throughfall and litterfall (d) foliar nutrient status. This investigation was carried out in south-eastern Belgium at a site converted in 1998 to a mixed deciduous stand, after two spruce generations. Plantations of common alder (Alnus glutinosa (L.) GAERTN.), european beech (Fagus sylvatica L.), pedunculate oak (Quercus robur L.), silver birch (Betula pendula ROTH.), goat willow (Salix caprea L.) and rowan (Sorbus aucuparia L.) were located in 4 fenced plots within a 81 ha catchment. Soil chemical properties (soil organic matter, pH, cation exchange capacity, base saturation, exchangeable cations), soil microbial activities (net N mineralization, potential nitrification, basal respiration) and microbial biomass (microbial biomass C and N) were measured under broadleaves and spruce. Soil chemistry of this highly acid soil was improved, 11 years after conversion, through an increase in base saturation and the exchangeable Mg2+ pool under rowan, as well as an increase in the exchangeable Ca2+ pool under alder, oak and rowan. Exchangeable acidity due to H+ in the forest floor also decreased under broadleaves. Nitrification was increased under the N2 fixing alder and decreased under young spruce. The C:N ratio of cold water-extractable soil organic matter fractions revealed to be a good indicator of potential nitrification rates within this site and across species, with a threshold of a C:N ratio of 10 above which soils did not nitrify. Throughfall and litterfall under the tree species were investigated by installing 63 throughfall collectors and 63 litter traps within 3 fenced plots (broadleaves) and across the catchment (young spruce). We measured the quantity of litterfall (foliar, twigs, reproductive parts and total), the quality of foliar litterfall (macro and micro-elements and C/N ratio) and calculated the potential nutrient return to the forest floor though foliar litterfall. For throughfall, we analyzed macro and micro-element concentrations and throughfall fluxes. Foliar nutrient status was determined by chemical analyses of fresh leaves and spruce needles of 3 age classes. The throughfall deposition of Ca2+, Mg2 and K+ was significantly higher under rowan and birch. NO3--N throughfall fluxes were significantly higher under young spruce compared to broadleaves. We observed the lowest total litterfall quantity produced by oak, while the highest litterfall quantity observed under rowan. Foliar litterfall of rowan showed significantly higher potential nutrient fluxes of Ca, Mg and K compared to other species, which corresponds to fresh foliage concentrations. The foliar litterfall was a main source of Ca, while for K throughfall was the main source of nutrient return to the forest floor in the study area. In spruce needles, Ca and Mg concentrations were at deficiency level and K concentrations at critical level, according to threshold values. Our results demonstrated that the plantation of pioneer species, especially rowan, may enhance the base cations in the forest floor on nutrient poor, acid soils through higher input in litterfall and throughfall. [less ▲]

Detailed reference viewed: 35 (6 ULg)
Full Text
See detailElement fluxes, forest floor characteristics and microbial activities under deciduous tree species after conversion of a Norway spruce (Picea abies (L.) Karst.) stand
Bazgir, Masoud ULg; Guillaume, Patricia ULg; Carnol, Monique ULg

Poster (2011, March)

Forest management is currently confronted with major questions, such as how to adapt plantation forests to a changing world. This questioning is not only essential with regard to forest health and ... [more ▼]

Forest management is currently confronted with major questions, such as how to adapt plantation forests to a changing world. This questioning is not only essential with regard to forest health and productivity, but also within the frame of climate mitigation. As Norway spruce monocultures (Picea abies) have been planted in Europe beyond their assumed natural range, are subjected to forest decline and have negative impacts on ecological conditions, conversion into mixed stands has been suggested. Tree species can influence nutrient inputs, soil microbial activity, soil chemistry and nutrient cycling in forest ecosystems. These tree species effects on biogeochemical cycles may vary according to soil type, site characteristics and land use history. The objective of the present study was to quantify element fluxes in throughfall and seepage water, forest floor exchangeable element pools and nitrogen transformations, 12 years after conversion from Picea abies monocultures to a mixed forest stand. Measurements were performed under young and mature Picea abies, Alnus glutinosa (L.) Gaertn., Quercus robur L. and Sorbus aucuparia L. Thus trees have grown on the same site, sharing identical initial soil conditions and site history, so that potential effects on microbial processes and soil properties can be imputed to tree species. Results showed that conversion had a short term impact on nutrient budgets and nutrient cycling in the upper soil layer; in particular on input fluxes of acidifying cations, soil base saturation, net N mineralization and nitrification. [less ▲]

Detailed reference viewed: 52 (3 ULg)