The Response of Soil Processes to Climate Change: Results from Manipulation Studies of Shrublands Across an Environmental Gradient

Abstract

Predicted changes in climate may affect key soil processes such as respiration and net nitrogen (N) mineralization and thus key ecosystem functions such as carbon (C) storage and nutrient availability. To identify the sensitivity of shrubland soils to predicted climate changes, we have carried out experimental manipulations involving ecosystem warming and prolonged summer drought in ericaceous shrublands across a European climate gradient. We used retractable covers to create artificial nighttime warming and prolonged summer drought to 20-m 2 experimental plots. Combining the data from across the environmental gradient with the results from the manipulation experiments provides evidence for strong climate controls on soil respiration, net N mineralization and nitrification, and litter decomposition. Trends of 0%-19% increases of soil respiration in response to warming and decreases of 3%-29% in response to drought were observed. Across the environmental gradient and below soil temperatures of 20°C at a depth of 5-10 cm, a mean Q 10 of 4.1 in respiration rates was observed although this varied from 2.4 to 7.0 between sites. Highest Q 10 values were observed in Spain and the UK and were therefore not correlated with soil temperature. A trend of increased accumulated surface litter mass loss was observed with experimental warming (2%-22%) but there was no consistent response to experimental drought. In contrast to soil respiration and decomposition, variability in net N mineralization was best explained by soil moisture rather than temperature. When water was neither limiting or in excess, a Q 10 of 1.5 was observed for net N mineralization rates. These data suggest that key soil processes will be differentially affected by predicted changes in rainfall pattern and temperature and the net effect on ecosystem functioning will be difficult to predict without a greater understanding of the controls underlying the sensitivity of soils to climate variables.

Regulation of microbial carbon, nitrogen, and phosphorus transformations by temperature and moisture during decomposition of Calluna vulgaris litter

“…The percentage remaining of litter initial mass after 206 days ranged from 94.9% at 5°C and 50% moisture to 71.5% at 20°C and 200% moisture. Emmett et al (2004) reported data from litterbag experiments with C. vulgaris litter in a dry heathland in Denmark, in a wet heathland in Wales, and in the Oldebroekse heide in The Netherlands where we sampled the litter for this experiment. They found a remaining amount of initial mass after 200 days of 73, 82, and 80%, respectively.…”

“…Emmett et al (2004) manipulated temperature and moisture with a nonintrusive field experiment. They induced 2 months summer droughts and increased temperature with 0.5-2.0°C on other experimental plots.…”

Effect of temperature and precipitation on nitrate leaching from organic cereal cropping systems in Denmark

“…For instance, Patil et al (2012), using the FASSET model to evaluate the sensitivity of winter wheat yield and soil N losses to stepwise changes in mean and variance of climatic variables in Denmark, showed an increase in mineral N leaching from winter wheat with increasing temperature, in particular for sandy loam soil at temperature increases above 2 • C. They also found higher simulated soil mineral N concentrations after crop harvest in summer and, therefore, higher risk of NO 3 N leaching during autumn and winter, which was ascribed to less N uptake by the crop and increased mineral N in soil profiles. The increased soil mineral N could be mostly attributed to climatic factors, in particular temperature that enhances mineralization processes through effects on soil microbial activity (Leirós et al, 1999;Emmett et al, 2004;Patil et al, 2010). In a synthesis of results from 32 studies on attempting to predict the influence of climate changes on terrestrial ecosystems, temperature increase of 2.4 • C was found to increase soil respiration by 20%, whereas net N mineralization rates increased by 46% (Rustad et al, 2001).…”

A review of the impact of climate change on future nitrate concentrations in groundwater of the UK

“…Soil moisture appears to be the primary variable affecting soil enzyme activity (Sardans et al, 2008). N mineralisation and nitrification are related to temperature and indirectly to rainfall (Emmett et al, 2004). The overall effects depend on how changes affect soil moisture during the summer season (Leirós et al, 1999), on the countering effects of growth enhancement from increased carbon inputs and increased nitrate uptake by vegetation (Ineson et al, 1998a;Ineson et al, 1998b).…”