Nitrogen supply rate in Scots pine (Pinus sylvestris L.) forests of contrasting slope aspect

Abstract

We studied Nitrogen (N) transformations in Pinus sylvestris forest stands in the foothills of the SE Pre-Pyrenees (NE Spain). Plots were selected in two contrasting aspects (two plots per aspect) and N supply rate was measured by the resin-core incubation technique once every three months. N leaching through litter layers (L and F horizons) was evaluated by 5 zero-tension lysimeters in each plot. NH +-N, NO 3 -N and soluble organic-N were determined in all solutions. N supply rate showed a clear seasonal pattern. Ammonification and nitrification were segregated in space and in time. While ammonification showed a peak in spring, nitrification was higher in summer. There was evidence suggesting that nitrification occurs mostly in A1 horizon. Nitrification rates differed significantly among plots. N supply rate was 12.7-23.5 kg N.ha-~ -yr-l but it did not differ between aspects or plots. Inorganic-N leached through litter layers was 14-17 kg N.ha -1.yr -1, and represented a high proportion of N supply rate. Organic-N leached through litter layers (27.8-37.0 kg N.ha-1.yr-1 ) was higher than leached inorganic-N. However, in most cases organic-N did not represent a high proportion of changes in soluble organic-N pools in H and A1 horizons (about 240 kg N.ha-l.yr-1). This large decrease in soluble organic-N was much greater than the increase in inorganic-N. The possible fate of these large amounts of organic-N is discussed.

Seasonal Dynamics of N, P, and K in an Organic and Inorganic Fertilized Willow Biomass System

“…The negative correlations between NO 3 − and NH 4 + supply and bioavailability support the existence of this condition in the soil. Similar observation was made by Casals et al [17] who reported that mineral N uptake followed a seasonal pattern that matched N supply rate.…”

“…Soil chemical analyses were done at the Ag Analytical Lab of Penn State University. Total N was determined by combustion method [17]. Available P, K, Ca, and Mg were determined via inductively coupled plasma (ICP) following Mehlich 3 extraction.…”

Linkages between the soil organic matter fractions and the microbial metabolic functional diversity within a broad-leaved Korean pine forest

“…The previous studies and the results of this study indicated that changes in the soil microbial community, activity and functional diversity may be regulated by C and N availability through labile SOM pools. Litterfall, root turnover and exudation were interpreted as providing significant contributions to the DOC production in the forest soil, as it consisted mainly of simple sugars and non humic-bound polysaccharides [52,53]. Presumably, the highly heterogeneous nature of aboveground vegetation composition [30], belowground root biomass [31] and rhizosphere resources such as root exudation [16] in forest ecosystems should induce high variability of DOC in the forest soils as was observed in this study Fig.…”

Influence of Mediterranean shrub species on soil chemical properties in typical Mediterranean environment

“…Whereas, in the late spring, when the temperature increases, the nitrification processes predominates, increasing notably the N-NO 3 2 levels, especially under the legume shrubs (Ulex parviflorus), where a great increase is observed (Figure 3). Casals et al (19) in Mediterranean forest ecosystems dominated by Pinus sylvestris demonstrate that the availability of N increased during the growing season, first by increasing ammonification processes and second, in summer, by increasing nitrification.…”