Noël Lust

Earthworm biomass and species diversity in windthrow sites of a temperate lowland forest

Summary In temperate forests, disturbance by uprooting of trees is a key process in maintaining species richness and diversity. Nevertheless, very little is known about the changing role and abundance of earthworm communities in different windthrow microsites. The aim of the study was to find (i) whether single-tree uprooting causes significant changes in earthworm biomass and species composition and (ii) which changes in chemical and physical soil properties can be related to it. Twelve single-tree gap sites in an Ulmo-Fraxinetum aceretosum were selected, six sites locally dominated by beech ( Fagus sylvatica ) and six by poplar ( Populus x euramericana ). At each site, 7 microsites were sampled for soil chemical and soil physical properties: undisturbed soil beneath closed canopy, undisturbed soil beneath the gap in the canopy layer, the outer side of the pit, the inner side of the pit, the soil fallen from the mound into and away from the pit, and the mound itself. At six sites also earthworms were collected. The impact of microsite on earthworm biomass and species diversity was more important than the impact of tree species. A significant decrease in earthworm biomass and species number was detected from closed canopy over gaps to zones with soil disturbance and finally to windthrow mounds which never contained earthworms. The most pronounced reaction was the negative impact of uprooting on endogeic biomass. Epigeic biomass or species number of any ecological group changed more moderately. Six years after uprooting, microsites with direct soil disturbance were still adverse for earthworms though some – epigeic – species could profit from the absence of competitive species. It is concluded that in temperate lowland forests, the early uprooting phases induce changes in earthworm communities due to changes in soil physical parameters and food availability.

Comparison of nitrate leaching under Silver birch (Betula pendula) and Corsican pine (Pinus nigra ssp laricio) in Flanders (Belgium)

In a forest in Flanders (Belgium), situated in a region of intensive livestock production, comparable stands of Corsican pine and silver birch were studied for (1) NH4+ and NO3- concentrations in throughfall water and soil solution and (2) depositions and leaching of NH4+ and NO3- to groundwater. In each stand, throughfall collectors and porous cup lysimeters at three depths (0.1m, 0.5m and 1m) were installed in three replicated sets. Throughfall concentrations of ammonium and nitrate were significantly different for both species as well as soil solution concentrations of nitrate at all depths. Under pine, nitrate concentrations of the soil solution at 1m depth clearly exceeded the Belgian critical level for drinking water (50 mg.1-1). Under birch, this level was only sporadically exceeded. During the sampling period, the depositions of NH4+-N and NO3--N reached respectively 21.6 kg/ha and 6.3 kg/ha under birch and 81.3 and 15.2 kg/ha under Corsican pine. Nitrate-N leaching under silver birch amounted 25.4 kg/ha whereas 56.4 kg/ha was measured under Corsican pine.

Experiences with participatory approaches in the forestry field in Flanders

Participationxa0 into the forestry decision making is in Flanders not to be considered as axa0 real newxa0xa0xa0 fact. A number of important forestry topics can be mentioned; wherebyxa0 participation played axa0xa0xa0 role: (1) forest legislation and forest policy; (2) management plans; (3)xa0 National Forest Plan; (4)xa0xa0xa0 criteria for sustainable forestry; (5) the Spatial Structure Plan Flanders;xa0 (6) establishment ofxa0xa0xa0 urban forests.xa0xa0xa0 The Forest administration, the Flemish Supreme Forestry Council, forestxa0 owners, forestxa0xa0xa0 associations and scientific institutes are well known internal actors,xa0 whereas the agriculturalxa0xa0xa0 sector and the nature conservation sector are the most salient externalxa0 actors.xa0xa0xa0 However, a distinction must be made between participation and externalxa0 pressure. Realxa0xa0xa0 participation supposes that it is institutionalized and that it isxa0 considered as a normal fact. Today,xa0xa0xa0 the pressure behind the screen is very great and the real decision makingxa0 obviously occursxa0xa0xa0 there. At least the impression exists that external actors such as thexa0 economic sector, the naturexa0xa0xa0 sector and the agricultural sector, which are often not directly involvedxa0 in the forest decisionxa0xa0xa0 making, pIesently ore determine many forest policy topics than the forestryxa0 sector itself.xa0xa0xa0 Besides, participation is not a priori a basis of success.