Compound effects of soil moisture extremes, forest fires, and aspects on
soil respiration from Post-fire and Undisturbed Pinus nigra Forests
Abstract
Hydrological extremes and wildfires are increasing in magnitude and
frequency due to climate change impacts; hence, it is essential to
understand the compound effects of these disturbances on the different
components of the global carbon cycle, particularly soil respiration
(Rs). We conducted an experiment in a randomized complete block design
with four replicate blocks to determine the compound effects of soil
moisture extremes, types of forest fires, and aspects on Rs in postfire
and undisturbed black pine (Pinus nigra Arnold) forest ecosystem. We
measured Rs using an automated soil respiration machinery (LI-8100A,
LiCor BioSciences), which also measures soil temperature, air
temperature, and soil moisture simultaneously. The Rs exhibited
significant differences among treatment combinations (p
<.0001), time (p <.0001), and moisture regimes (p
<0.0001) but not with the interaction effects of treatment x
time (p = 0.0058), aspects (p = 0.95410), and types of forest fires (p =
0.0059). The compound effects of soil moisture drought x crown fire x
exposed aspect revealed a significantly lowest Rs (1.21 µmol m-2 s-1)
among treatment combinations. In contrast, the compound effects of
water-saturated soil x types of forest x aspect showed no significant
differences compared to the control. The Rs ranged from 1.21 to 1.81
µmol m-2 s-1 for the soil moisture drought x forest fires x aspects,
1.90 to 2.55 µmol m-2 s-1 for the water-saturated soil x forest fires x
aspects, and 1.83 to 2.38 µmol m-2 s-1 for the control. The Rs exhibited
a positive relationship with the soil temperature (r = 0.59) and the air
temperature (r = 0.63) but negatively correlated with the soil moisture
(r = -0.33). The soil and air temperatures showed a strongly positive
correlation (r = 0.87), suggesting that a near-surface air temperature
provides a good approximation of the soil temperature.