Mitigating the Stress of Drought on Soil Respiration by Selective Thinning: Contrasting Effects of Drought on Soil Respiration of Two Oak Species in a Mediterranean Forest

Abstract

Abstract:Drought has been shown to reduce soil respiration (SR) in previous studies. Meanwhile, studies of the effect of forest management on SR yielded contrasting results. However, little is known about the combined effect of drought and forest management on SR. To investigate if the drought stress on SR can be mitigated by thinning, we implemented plots of selective thinning and 15% reduced rainfall in a mixed forest consisting of the evergreen Quercus ilex and deciduous Quercus cerrioides; we measured SR seasonally from 2004 to 2007. Our results showed a clear soil moisture threshold of 9%; above this value, SR was strongly dependent on soil temperature, with Q 10 of 3.0-3.8. Below this threshold, the relationship between SR and soil temperature weakened. We observed contrasting responses of SR of target oak species to drought and thinning. Reduced rainfall had a strong negative impact on SR of Q. cerrioides, whereas the effect on SR for Q. ilex was marginal or even positive. Meanwhile, selective thinning increased SR of Q. cerrioides, but reduced that of Q. ilex. Overall, our results showed that the negative effect of drought on SR can be offset through selective thinning, but the effect is attenuated with time.

Thinning around old oaks in spruce production forests: current practices show no positive effect on oak growth rates and need fine tuning

“…(1) thinning increases oak growth rates, the increase being indicative of improved light conditions and decreased competition for soil nutrient resources with spruce trees, as suggested by common oak response to thinning (Barrio Anta and varez Gonzalez 2005; Stefancik 2012); (2) the effect of thinning depends on the age, size and crown conditions of the focal trees; (3) sensitivity of oaks to summer drought increases as the thinning intensity increases (Chang et al 2016;Stojanovic et al 2017).…”

Thinning decreased soil respiration differently in two dryland Mediterranean forests with contrasted soil temperature and humidity regimes

“…Soil heterotrophic activity concentrates in a shallow layer, where water content quickly changes, which explains the response of heterotrophic respiration to water content. Autotrophic soil respiration depends on water root uptake from deeper layers (Chang et al 2016;Puertes et al 2019), which is why it is less sensitive to surface soil water content variations. The effect of humidity on the Rs rate may be attributed to heterotrophic microbial respiration, which is very sensitive to surface soil humidity.…”

“…Other authors observed no effect of thinning on soil respiration (Campbell et al 2009). Chang et al (2016) indicated that Rs response to thinning was species-dependent with Rs responding less to thinning in deep-rooted species. The general review by Zhang et al (2018) reported an initial increase in Rs after light or moderate thinning intensity in broadleaved or mixed forests.…”

God save the queen! How and why the dominant evergreen species of the Mediterranean Basin is declining?

“…2021 ). One of the most common practices of adaptive silviculture is selective thinning, which consists of reduction of stem density ( Chang et al . 2016 ) to improve forest health and productivity by increasing the solar radiation reaching soil, soil organic matter, water and nutrient availability for the remaining trees ( Tang et al .…”