Soils as Driver and Victim of Climate Change in Egypt
121
some previous studies presented different or opposite effect of SOM on soil CO 2
flux under different conditions [40].
In a recent study [41], data from long-term experiments were conducted to study
the effect of crop waste (CW) incorporation on SOM and GHG emissions in Europe
[41]. They concluded that the CW incorporation had increased SOC by 7%. In
contrast, in some instances, CO 2 emissions were 6-times and N 2 O emissions 12times higher after CW incorporation. As the experiment proceeded, response ratio
(RR) for SOC concentration increased. For N 2 O emissions, RR was significantly
higher in experiments with a duration period of <5 years compared with 11–20 years.
3.2 Soil Temperature and Moisture
The Intergovernmental Panel on Climate Change [4] has found that the extrapolated
warming trend over the 50 years from 1956 to 2005 (0.13 °C [0.10–0.16 °C] per
decade) is nearly double that for the 100 years from 1906 to 2005. This temperature
rise is widespread all over the world and is higher over land and at higher latitudes.
Soil temperature is considered as sensitive climate indicator and driver at the same
time. Scientists regarded soil temperature data in the research on climate change [42].
Close relationships were recorded between soil temperatures and global warming.
The changes in the temperatures of soils over the last 100 years for three locations
in Ireland was studied [43]. They showed an increasing attitude of 0.04–0.25 °C per
decade. Higher attitude (0.43–0.66 °C/decade) in the mean temperatures of surface
soil (0–40 cm) in Tibet, China, during 1961–2005 was found, especially in spring
[44]. They also concluded that such positive trend with soil temperatures was stronger
than that for air temperature. In a study on loamy soils of Faisalabad region, India
[45], an increasing difference (T) was found between soil and air temperatures as it
reached +9.8 °C in summer and +6.9 °C in winter. Also, It was concluded from data
of 30 climate stations across Canada during 1958–2008 that stronger trend with time
in soil temperature was found at about 66% of the investigated sites at all depths below
5 cm [46]. A warming attitude of 0.26–0.30 °C per decade was consistently recorded
in spring (March–April–May) at all the investigated depths between 1958 and 2008.
Air temperatures (T min or T max ) had a consistent effect on soil temperatures, showing a
strong positive correlation which was less in winter when compared to other seasons.
Furthermore, it was stated that the average air, minimum or maximum air temperature
and average soil temperature, respectively, had significant exponential regression
relationship during the whole measuring period of CO 2 gas emission [47].
On the other side, both soil temperature and moisture have strong interactive effects on soil GHG emissions. Laboratory incubations, field observations,
and meta-analyses have documented changing GHG fluxes with rising temperature [48, 49]. Rates of CO 2 emission increased exponentially with increasing temperature from −1 to +16 °C during the wet season of forest soils
in both Norway and Germany [50]. It is apparent that soil temperature was
the dominant factor for soil carbon dioxide emissions when matric potential
121
some previous studies presented different or opposite effect of SOM on soil CO 2
flux under different conditions [40].
In a recent study [41], data from long-term experiments were conducted to study
the effect of crop waste (CW) incorporation on SOM and GHG emissions in Europe
[41]. They concluded that the CW incorporation had increased SOC by 7%. In
contrast, in some instances, CO 2 emissions were 6-times and N 2 O emissions 12times higher after CW incorporation. As the experiment proceeded, response ratio
(RR) for SOC concentration increased. For N 2 O emissions, RR was significantly
higher in experiments with a duration period of <5 years compared with 11–20 years.
3.2 Soil Temperature and Moisture
The Intergovernmental Panel on Climate Change [4] has found that the extrapolated
warming trend over the 50 years from 1956 to 2005 (0.13 °C [0.10–0.16 °C] per
decade) is nearly double that for the 100 years from 1906 to 2005. This temperature
rise is widespread all over the world and is higher over land and at higher latitudes.
Soil temperature is considered as sensitive climate indicator and driver at the same
time. Scientists regarded soil temperature data in the research on climate change [42].
Close relationships were recorded between soil temperatures and global warming.
The changes in the temperatures of soils over the last 100 years for three locations
in Ireland was studied [43]. They showed an increasing attitude of 0.04–0.25 °C per
decade. Higher attitude (0.43–0.66 °C/decade) in the mean temperatures of surface
soil (0–40 cm) in Tibet, China, during 1961–2005 was found, especially in spring
[44]. They also concluded that such positive trend with soil temperatures was stronger
than that for air temperature. In a study on loamy soils of Faisalabad region, India
[45], an increasing difference (T) was found between soil and air temperatures as it
reached +9.8 °C in summer and +6.9 °C in winter. Also, It was concluded from data
of 30 climate stations across Canada during 1958–2008 that stronger trend with time
in soil temperature was found at about 66% of the investigated sites at all depths below
5 cm [46]. A warming attitude of 0.26–0.30 °C per decade was consistently recorded
in spring (March–April–May) at all the investigated depths between 1958 and 2008.
Air temperatures (T min or T max ) had a consistent effect on soil temperatures, showing a
strong positive correlation which was less in winter when compared to other seasons.
Furthermore, it was stated that the average air, minimum or maximum air temperature
and average soil temperature, respectively, had significant exponential regression
relationship during the whole measuring period of CO 2 gas emission [47].
On the other side, both soil temperature and moisture have strong interactive effects on soil GHG emissions. Laboratory incubations, field observations,
and meta-analyses have documented changing GHG fluxes with rising temperature [48, 49]. Rates of CO 2 emission increased exponentially with increasing temperature from −1 to +16 °C during the wet season of forest soils
in both Norway and Germany [50]. It is apparent that soil temperature was
the dominant factor for soil carbon dioxide emissions when matric potential