Effects of forest management on soil N cycling in beech forests stocking on calcareous soils

Abstract

The effects of forest management (thinning) on gross and net N conversion, the balance of inorganic N production and consumption, inorganic N concentrations and on soil microbial biomass in the Ah layer were studied in situ during eight intensive field measuring campaigns in the years 2002-2004 at three beech (Fagus sylvatica L.) forest sites. At all sites adjacent thinning plots (''T'') and untreated control plots (''C'') were established. Since the sites are characterized either by cool-moist microclimate (NE site and NW site) or by warm-dry microclimate (SW site) and thinning took place in the year 1999 at the NE and SW sites and in the year 2003 at the NW site the experimental design allowed to evaluate (1) short-term effects (years 1-2) of thinning at the NW site and (2) medium-term effects (years 4-6) of thinning under different microclimate at the SW and NE site. Microbial biomass N was consistently higher at the thinning plots of all sites during most of the field campaigns and was overall significantly higher at the SWT and NWT plots as compared to the corresponding untreated control plots. The size of the microbial biomass N pool was found to correlate positively with both gross ammonification and gross nitrification as well as with extractable soil NO 3 -concentrations. At the SW site neither gross ammonification, gross nitrification, gross ammonium (NH 4 + ) immobilization and gross nitrate (NO 3 -) immobilization nor net ammonification, net nitrification and extractable NH 4 + and NO 3 -contents were significantly different between control and thinning plot. At the NET plot lower gross ammonification and gross NH 4 + immobilization in conjunction with constant nitrification rates coincided with higher net nitrification and significantly higher extractable NO 3 -concentrations. Thus, the medium-term effects of thinning varied with different microclimate. The most striking thinning effects were found at the newly thinned NW site, where gross ammonification and gross NH 4 + immobilization were dramatically higher immediately after thinning. However, they subsequently tended to decrease in favor of gross nitrification, which was significantly higher at the NWT plot as compared to the NWC plot during all field campaigns after thinning except for April 2004. This increase in gross nitrification at the NWT plot (1.73 mg N kg -1 sdw day -1 versus 0.48 mg N kg -1 sdw day -1 at the NWC plot) coincided with significantly higher extractable NO 3 -concentrations (4.59 mg N kg -1 sdw at the NWT plot versus Ó Springer Science+Business Media B.V. 2006 0.96 mg N kg -1 sdw at the NWC plot). Pronounced differences in relative N retention (the ratio of gross NH 4 + immobilization + gross NO 3 -immobilization to gross ammonification + gross nitrification) were found across the six research plots investigated and could be positively correlated to the soil C/N ratio (R = 0.94; p = 0.005).In sum, the results obtained in this study show that (1) thinning can lead to a shift in the balance of microbial inorganic N production ...

Effect of thinning on the amount of mineral nitrogen

“…The effect of thinning the European beech stands was similar to that found by Dannenmann et al (2006) in calcareous soils. Despite the fact that the stands grew on a different soil type and were younger (45 years old) than the stands studied by Dannenmann et al (2006), which were 70 to 80 years old, our results corresponded both in terms of the seasonal dynamics and the effect of the thinning on the European beech stands.…”

“…Despite the fact that the stands grew on a different soil type and were younger (45 years old) than the stands studied by Dannenmann et al (2006), which were 70 to 80 years old, our results corresponded both in terms of the seasonal dynamics and the effect of the thinning on the European beech stands. The highest NO 3 -concentration in the Březina forest stands was measured in October.…”

N<sub>2</sub>O, NO, N<sub>2</sub> and CO<sub>2</sub> emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

“…Total organic carbon (TOC) and total chemically bound nitrogen (TNb) were measured using a TOC analyzer (DIMATOC 2000, Dimatec Analysentechnik GmbH, Essen, Germany) and a coupled chemoluminescence detector, respectively. See Dannenmann et al (2006) The cores were first exposed to 20 • C temperature for preincubation before the air-dried samples were wetted to the desired soil moisture levels of 25 % WFPS (M25), 50 % WFPS (M50) and 75 % WFPS (M75). To avoid a bias of follow-up measurements, all three soil moisture levels were analyzed with independent cores.…”

Seasonality of soil microbial nitrogen turnover in continental steppe soils of Inner Mongolia

“…Nevertheless, studies on gross N turnover are available for a range of terrestrial ecosystems (Booth et al 2005), though the temporal resolution of these studies is strongly limited. The few available studies examining the temporal variability of gross N turnover in soils (e.g., Dannenmann et al 2006, Rosenkranz et al 2010 show that rates may markedly fluctuate across seasons. Hence, the available studies on gross N turnover in general neither allow for understanding seasonal dynamics or for calculating annual rates of gross N turnover.…”