Impacts of Climate Change on Microbial Activity in Agricultural …
109
Sodic, saline and saline-sodic soils are the three main types of salt-affected soils
dominant in the Nile delta especially in the middle and north delta soils which suffer from its location close to the Mediterranean coast and saline waterlogging [75].
These saline conditions led to an increase in the diversity and community of indigenous microorganisms especially bacteria that can be modified in their structure and
physiological activity under these conditions. These bacterial groups can maintain
osmotic equilibrium between the cytoplasm and the surrounding medium excluding
sodium ions from inside the cell. Additionally, they can synthesis specific compatible
organic osmolytes like proline, glycine and glutamine that accumulate the inorganic
solutes (Na
+ , K
+ and Mg
2+ ) [76]. Soil salinity in Egypt is one the common outstanding serious problems affecting crop production in cultivated and non-cultivated soils.
Therefore, the influence of soil salinity on soil microbial populations and enzyme
activities, especially in saline regions of Egypt has received more attention. For
example, soil samples (0–15 and 15–30 cm) were collected from salt-affected soils
at three different regions, the Suez Canal, Sinai peninsula and Al-Salhia regions, by
the researcher Ragab [77]. He found that the total counts of bacteria, nitrifying bacteria and cellulose decomposers are negatively correlated with total soluble salts and
positively correlated with organic carbon in surface layers, but nitrogen-fixing bacteria (Azotobacter and Clostridium) are not correlated with soluble salts or organic
carbon. On the other hand, halophilic bacteria were positively correlated with total
soluble salts and organic carbon in the soil layers. That is, the Egyptian microbiologist should be increasing the researches about behavior and physiology salt tolerant
bacteria in saline soils to pursue the application of these bacteria as biofertilizers in
saline environments.
4 Conclusions
Climate change has an impact on Egyptian soil microbial community and activities
both directly or indirectly. The fluctuation of temperature and elevated CO 2 are the
most climatic changes in Egypt that positively, negatively and neutrally affect soil
microbial activity, community and enzyme activities. Additionally, predominant of
saline soils in some regions in Egypt is a vital factor to the effect on soil microorganism populations and activities. However, most of researchers or studies focused on
climate change impacts as a single factor or by separate the different climate change
components (altered temperature and moisture or elevated CO 2 ) and manipulating
their responses on soil microbial activity independently. Indeed, the future studies
should be focused on multiple, and simultaneously interacting climate change factors such as temperature will interact with changes in moisture that both impact
on the overall and relative rate of enzyme production by soil microorganisms. The
behavior and response of plant growth promoting microorganisms to climate change
are very variedly and complicated, especially in saline habitats. Therefore, further
studies should be working on the activity of aerobic and anaerobic soil microbes and
enzyme activities in Egyptian saline agricultural soils.
109
Sodic, saline and saline-sodic soils are the three main types of salt-affected soils
dominant in the Nile delta especially in the middle and north delta soils which suffer from its location close to the Mediterranean coast and saline waterlogging [75].
These saline conditions led to an increase in the diversity and community of indigenous microorganisms especially bacteria that can be modified in their structure and
physiological activity under these conditions. These bacterial groups can maintain
osmotic equilibrium between the cytoplasm and the surrounding medium excluding
sodium ions from inside the cell. Additionally, they can synthesis specific compatible
organic osmolytes like proline, glycine and glutamine that accumulate the inorganic
solutes (Na
+ , K
+ and Mg
2+ ) [76]. Soil salinity in Egypt is one the common outstanding serious problems affecting crop production in cultivated and non-cultivated soils.
Therefore, the influence of soil salinity on soil microbial populations and enzyme
activities, especially in saline regions of Egypt has received more attention. For
example, soil samples (0–15 and 15–30 cm) were collected from salt-affected soils
at three different regions, the Suez Canal, Sinai peninsula and Al-Salhia regions, by
the researcher Ragab [77]. He found that the total counts of bacteria, nitrifying bacteria and cellulose decomposers are negatively correlated with total soluble salts and
positively correlated with organic carbon in surface layers, but nitrogen-fixing bacteria (Azotobacter and Clostridium) are not correlated with soluble salts or organic
carbon. On the other hand, halophilic bacteria were positively correlated with total
soluble salts and organic carbon in the soil layers. That is, the Egyptian microbiologist should be increasing the researches about behavior and physiology salt tolerant
bacteria in saline soils to pursue the application of these bacteria as biofertilizers in
saline environments.
4 Conclusions
Climate change has an impact on Egyptian soil microbial community and activities
both directly or indirectly. The fluctuation of temperature and elevated CO 2 are the
most climatic changes in Egypt that positively, negatively and neutrally affect soil
microbial activity, community and enzyme activities. Additionally, predominant of
saline soils in some regions in Egypt is a vital factor to the effect on soil microorganism populations and activities. However, most of researchers or studies focused on
climate change impacts as a single factor or by separate the different climate change
components (altered temperature and moisture or elevated CO 2 ) and manipulating
their responses on soil microbial activity independently. Indeed, the future studies
should be focused on multiple, and simultaneously interacting climate change factors such as temperature will interact with changes in moisture that both impact
on the overall and relative rate of enzyme production by soil microorganisms. The
behavior and response of plant growth promoting microorganisms to climate change
are very variedly and complicated, especially in saline habitats. Therefore, further
studies should be working on the activity of aerobic and anaerobic soil microbes and
enzyme activities in Egyptian saline agricultural soils.