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1.

Root trenching: a useful tool to estimate autotrophic soil respiration? A case study in an Austrian mountain forest

Eugenio Díaz-Pinés Andreas Schindlbacher Michael Pfeffer Robert Jandl Sophie Zechmeister-Boltenstern Agustín Rubio 《European Journal of Forest Research》2010,129(1):101-109

We conducted a trenching experiment in a mountain forest in order to assess the contribution of the autotrophic respiration to total soil respiration and evaluate trenching as a technique to achieve it. We hypothesised that the trenching experiment would alter both microbial biomass and microbial community structure and that fine roots (less than 2 mm diameter) would be decomposed within one growing season. Soil CO₂ efflux was measured roughly biweekly over two growing seasons. Root presence and morphology parameters, as well as the soil microbial community were measured prior to trenching, 5 and 15 months after trenching. The trenched plots emitted about 20 and 30% less CO₂ than the control plots in the first and second growing season, respectively. Roots died in trenched plots, but root decay was slow. After 5 and 15 months, fine root biomass was decreased by 9% (not statistically different) and 30%, (statistically different) respectively. When we corrected for the additional trenched-plot CO₂ efflux due to fine root decomposition, the autotrophic soil respiration rose to ~26% of the total soil respiration for the first growing season, and to ~44% for the second growing season. Soil microbial biomass and community structure was not altered by the end of the second growing season. We conclude that trenching can give accurate estimates of the autotrophic and heterotrophic components of soil respiration, if methodological side effects are accounted for, only. 相似文献

2.

Effects of aspect and altitude on carbon cycling processes in a temperate mountain forest catchment

Kobler Johannes Zehetgruber Bernhard Dirnböck Thomas Jandl Robert Mirtl Michael Schindlbacher Andreas 《Landscape Ecology》2019,34(2):325-340

Context

Varying altitudes and aspects within small distances are typically found in mountainous areas. Such a complex topography complicates the accurate quantification of forest C dynamics at larger scales.

Objectives

We determined the effects of altitude and aspect on forest C cycling in a typical, mountainous catchment in the Northern Limestone Alps.

Methods

Forest C pools and fluxes were measured along two altitudinal gradients (650–900 m a.s.l.) at south-west (SW) and north-east (NE) facing slopes. Net ecosystem production (NEP) was estimated using a biometric approach combining field measurements of aboveground biomass and soil CO₂ efflux (SR) with allometric functions, root:shoot ratios and empirical SR modeling.

Results

NEP was higher at the SW facing slope (6.60?±?3.01 t C ha^?1 year^?1), when compared to the NE facing slope (4.36?±?2.61 t C ha^?1 year^?1). SR was higher at the SW facing slope too, balancing out any difference in NEP between aspects (NE: 1.30?±?3.23 t C ha^?1 year^?1, SW: 1.65?±?3.34 t C ha^?1 year^?1). Soil organic C stocks significantly decreased with altitude. Forest NPP and NEP did not show clear altitudinal trends within the catchment.

Conclusions

Under current climate conditions, altitude and aspect adversely affect C sequestering and releasing processes, resulting in a relatively uniform forest NEP in the catchment. Hence, including detailed climatic and soil conditions, which are driven by altitude and aspect, will unlikely improve forest NEP estimates at the scale of the studied catchment. In a future climate, however, shifts in temperature and precipitation may disproportionally affect forest C cycling at the southward slopes through increased water limitation.

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3.

Experimental warming effects on the microbial community of a temperate mountain forest soil

Schindlbacher A Rodler A Kuffner M Kitzler B Sessitsch A Zechmeister-Boltenstern S 《Soil biology & biochemistry》2011,43(7):1417-1425

Soil microbial communities mediate the decomposition of soil organic matter (SOM). The amount of carbon (C) that is respired leaves the soil as CO₂ (soil respiration) and causes one of the greatest fluxes in the global carbon cycle. How soil microbial communities will respond to global warming, however, is not well understood. To elucidate the effect of warming on the microbial community we analyzed soil from the soil warming experiment Achenkirch, Austria. Soil of a mature spruce forest was warmed by 4 °C during snow-free seasons since 2004. Repeated soil sampling from control and warmed plots took place from 2008 until 2010. We monitored microbial biomass C and nitrogen (N). Microbial community composition was assessed by phospholipid fatty acid analysis (PLFA) and by quantitative real time polymerase chain reaction (qPCR) of ribosomal RNA genes. Microbial metabolic activity was estimated by soil respiration to biomass ratios and RNA to DNA ratios. Soil warming did not affect microbial biomass, nor did warming affect the abundances of most microbial groups. Warming significantly enhanced microbial metabolic activity in terms of soil respiration per amount of microbial biomass C. Microbial stress biomarkers were elevated in warmed plots. In summary, the 4 °C increase in soil temperature during the snow-free season had no influence on microbial community composition and biomass but strongly increased microbial metabolic activity and hence reduced carbon use efficiency. 相似文献

4.

Effects of stand patchiness due to windthrow and bark beetle abatement measures on soil CO2 efflux and net ecosystem productivity of a managed temperate mountain forest

Johannes Kobler Robert Jandl Thomas Dirnböck Michael Mirtl Andreas Schindlbacher 《European Journal of Forest Research》2015,134(4):683-692

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5.

Future management options for cembran pine forests close to the alpine timberline

Nathalia Jandl Robert Jandl Andreas Schindlbacher 《Annals of Forest Science》2018,75(3):81

Key message

High-elevation forests in the Alps protect infrastructure and human lives against natural hazards such as rockfall, flooding, and avalanches. Routinely performed silvicultural interventions maintain the required stand structure but are not commercially viable in remote forests due to high operational costs. Financial subsidies for the management of high-elevation protection forests are an efficient strategy to ensure sustainable forest cover.

Context

Presently, many high-elevation forests in the Alps are managed in order to ensure the provision of ecosystem services with emphasis on the minimization of natural hazards.

Aims

We studied the possible economic performance of a high-elevation protection forest from an owner’s perspective. We investigated whether the increase in productivity due to climate change and a favorable market for the dominating cembran pine (Pinus cembra L.) are sufficient for profitable timber production in protection forests.

Methods

We simulated the standing timber stock and the soil carbon pool for a 100-year period with climate-sensitive models and compared harvesting costs with expected revenues. Our scenarios included different climates, intensities of timber extractions, parameters of the timber market, and the availability of government subsidies.

Results

Overall, the productivity of forests increases by approximately 15% until the end of the century. In a zero-management scenario, the forest accumulates carbon both in the aboveground biomass and the soil. In the case of an extensive management with moderate timber extractions every 50 years, the carbon stocks decline both in biomass and soil. A more intensive management scenario with extractions every 30 years leads to substantial losses of the soil and biomass carbon pools. In addition, the stand structure changes and the protective function of the forest is not sustainably ensured. Timber production can be economically successful only with high selling prices of cembran pine timber and the availability of governmental subsidies for forest management. The admixed European larch (Larix decidua Mill.) contributes only marginally to the economic success. The main challenge are harvesting costs. The costs of timber extraction by a long-distance cableway logging system exceed the value of the harvested timber.

Conclusion

The intensification of forest management cannot be recommended from the perspective of timber production, sustainable forest management, and protection against natural hazards. Our simulation experiment shows that the extraction of timber at decadal intervals depletes the carbon stock that is insufficiently replenished from aboveground and belowground litterfall. Leaving the forest unmanaged does not impose a particular threat to stand stability and is under the encountered situation, a justified strategy.

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