Spatial variability of throughfall water and chemistry and forest floor water content in a Douglas fir forest stand

Abstract

This study focuses on spatial variability of throughfall water and chemistry and forest floor water content within a Douglas fir (Pseudotsuga menziesii, Franco L.) forest plot. Spatial patterns of water and chemistry (NH 4 + , NO 3 -, SO 4 2-, Cl -, Mg 2+ , Ca 2+ , Na + and K + ) were compared and tested for stability over time. The spatial coefficient of variation (CV) was between 18 and 26% for amounts of throughfall water and ions, and 17% for forest floor water content. Concentrations and amounts of all ions were correlated significantly. Ion concentrations were negatively correlated with throughfall water amounts, but, except for NH 4 + , there was no such relation between throughfall water and ion amounts. Spatial patterns of throughfall water fluxes and forest floor water contents were consistent over time; patterns of ion fluxes were somewhat less stable. Because of the spatial variability of forest floor thickness and drainage, it was not possible to relate patterns in throughfall water directly to patterns in water content. The spatial variability of throughfall nitrogen and forest floor water contents can cause significant variability in NO 3 -production within the plot studied.

Inter-crown versus under-crown area: contribution of local configuration of trees to variation in topsoil morphology, pH and moisture in Abies alba Mill. forests

“…This influence could result from reduced water input due to interception in the crowns, the buffering of mineral soil from large amounts of summer rainfall by organic layers (Leuschner 2002) or water extraction by tree roots (Schume et al 2003). In fact, a positive correlation between interception rates and stand density has been documented repeatedly (Raat et al 2002). For instance, Olszewski (1984) and Kozłowski (2003) found that the highest through fall in conifer and mixed stands occurred under crown edges and the lowest near the stem, with average differences amounting to over 100% of direct precipitation.…”

Seasonal variations of throughfall chemistry in pure and mixed stands of Oriental beech (Fagus orientalis Lipsky) in Hyrcanian forests (Iran)

“…Rainwater is thereby influenced by three main processes (Chiwa et al 2004): (1) the washing of deposits accumulated on the canopy between precipitation events, (2) the leaching of material from internal plant tissues and (3) the uptake by foliage of solutes. Tree species with different foliage properties exhibit different patterns of throughfall water and ion fluxes (Beier et al 1993;Hansen 1995;Raat et al 2002;Whelan et al 1998). Furthermore, as dry deposition is also a function of foliage properties (Lovett 1994), it may cause species-related differences (Hojjati et al 2009;Rothe et al 2002).…”

Nitrogen turnover in fresh Douglas fir litter directly after additions of moisture and inorganic nitrogen

“…Amounts of NH 4 + and/or NO 3 -added (Table 2) were calculated from the amounts of nitrogen added to the forest floor during a rain event (2.7 kg-N ha -1 ; Hansen et al 1994;Raat et al 2002), the molar ratio of NH 4 + :NO 3 -in throughfall (2.7:1; Draaijers et al 1998) and the total dry mass of the forest floor (3.2 kg m -2 ; Wessel and Tietema 1995). In this calculation we assumed that throughfall was distributed evenly over the top half of the forest floor.…”

“…In an earlier study (Raat et al 2002), it was shown that during a rain event not only the forest floor is rewetted, but that simultaneously a large pulse of inorganic-N is added via throughfall. Recorded N pulses were as high as 2.7 kg-N ha -1 , equaling about 6.5% of the yearly atmospheric N deposition.…”