Impacts of Climate Change on Microbial Activity in Agricultural …
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the microbial extracellular enzyme (α-glucosidase, β-glucosidase, β-xylosidase, cellobiohydrolase, and N-acetyl-glucosaminidase) is more sensitive to nitrogen application and change of soil temperature. They also found that nitrogen-decaying enzymes
have lesser sensitive to temperature than carbon-decaying enzymes. This finding can
be attributed to the soil warm led to an increased nitrogen limitation, resulting in
an increase in the production of nitrogen-decaying enzymes by soil microorganisms
when compared to the production of carbon-decaying enzymes [39]. On investigating
such areas, Gao et al. [12] showed that increased microbial biomass C and significantly promoted the activity of enzymatic hydrolysis of lignin and acid phosphatase
as a result of short-term simulated soil warming and the addition of nitrogen fertilizer
in the subtropical province, China.
Several previous studies have demonstrated the direct positive effect of warming climate on the colonization, community and structure of arbuscular mycorrhizal
(AM) fungi [34, 40]. Additionally, soil temperature affects carbon allocation within
arbuscular mycorrhizal networks and carbon transport from plant to fungus. For
example, Hawkes et al. [41] evaluate the influence of soil temperature on the community of different species from AM fungi associated with Plantago lanceolata and
their structure. They postulated that increased soil temperature from 14 to 26 °C
significantly changed the structure and allocation of the AM fungi hyphal networks
and induce a switch from more vesicles (responsible for storage) in cooler soils to
more extensive extraradical hyphal networks (indicating growth) in warmer soils.
Other researchers, for instance, Gavito et al. [42] and Heinemeyer and Fitter [43]
also observed that higher temperature (24–30 °C) leads to promote the root colonization by AM fungi, more extensive extraradical mycelium, and more glucose uptake,
nevertheless the optimum temperature was varied based on species of AM fungus.
According to these authors, these effects were due to faster carbon allocation to the
rhizosphere and increased respiration of the extraradical mycelium as increase soil
temperature. These effects in the biomass of AM fungi are very important as AM
fungi play an essential role in the plant, plant nutrition, community and ecosystem
responses to world change.
Similarly, with AM fungi, soil temperature has a negative or positive effect on
the performance of plant-beneficial bacterial, indicating bacterial genotype-specific
favorite’s temperature conditions [44]. These authors observed the shoot and root
of winter wheat significantly increased when inoculated with Mycobacterium sp.,
Pseudomonas fluorescens and Pantoea agglomerans strains at 16 °C when compared to 26 °C in the loamy sand. On the other hand, Mycobacterium phlei and
Mycoplana bullata performed well under both temperatures. Under Egyptian arid
conditions, high soil temperature has a positive or negative effect on the performance of free-living bacteria and the life of rhizobia. The optimum temperature for
growth in the medium is 28–30 °C, and many are unable to grow at 38 °C. Nevertheless, some strains of rhizobia from the woody legumes are grown well at 40 or
44 °C. Additionally, increased soil temperature leads to form ineffective nodules,
but R. leguminosarum bv. Phaseoli exhibit higher heat tolerance and can form effective nodule with their host legumes [45]. In Egyptian soils, the optimum activity of
nitrogen-fixing Azotobacter and Clostridium occurred when soil temperature raised
103
the microbial extracellular enzyme (α-glucosidase, β-glucosidase, β-xylosidase, cellobiohydrolase, and N-acetyl-glucosaminidase) is more sensitive to nitrogen application and change of soil temperature. They also found that nitrogen-decaying enzymes
have lesser sensitive to temperature than carbon-decaying enzymes. This finding can
be attributed to the soil warm led to an increased nitrogen limitation, resulting in
an increase in the production of nitrogen-decaying enzymes by soil microorganisms
when compared to the production of carbon-decaying enzymes [39]. On investigating
such areas, Gao et al. [12] showed that increased microbial biomass C and significantly promoted the activity of enzymatic hydrolysis of lignin and acid phosphatase
as a result of short-term simulated soil warming and the addition of nitrogen fertilizer
in the subtropical province, China.
Several previous studies have demonstrated the direct positive effect of warming climate on the colonization, community and structure of arbuscular mycorrhizal
(AM) fungi [34, 40]. Additionally, soil temperature affects carbon allocation within
arbuscular mycorrhizal networks and carbon transport from plant to fungus. For
example, Hawkes et al. [41] evaluate the influence of soil temperature on the community of different species from AM fungi associated with Plantago lanceolata and
their structure. They postulated that increased soil temperature from 14 to 26 °C
significantly changed the structure and allocation of the AM fungi hyphal networks
and induce a switch from more vesicles (responsible for storage) in cooler soils to
more extensive extraradical hyphal networks (indicating growth) in warmer soils.
Other researchers, for instance, Gavito et al. [42] and Heinemeyer and Fitter [43]
also observed that higher temperature (24–30 °C) leads to promote the root colonization by AM fungi, more extensive extraradical mycelium, and more glucose uptake,
nevertheless the optimum temperature was varied based on species of AM fungus.
According to these authors, these effects were due to faster carbon allocation to the
rhizosphere and increased respiration of the extraradical mycelium as increase soil
temperature. These effects in the biomass of AM fungi are very important as AM
fungi play an essential role in the plant, plant nutrition, community and ecosystem
responses to world change.
Similarly, with AM fungi, soil temperature has a negative or positive effect on
the performance of plant-beneficial bacterial, indicating bacterial genotype-specific
favorite’s temperature conditions [44]. These authors observed the shoot and root
of winter wheat significantly increased when inoculated with Mycobacterium sp.,
Pseudomonas fluorescens and Pantoea agglomerans strains at 16 °C when compared to 26 °C in the loamy sand. On the other hand, Mycobacterium phlei and
Mycoplana bullata performed well under both temperatures. Under Egyptian arid
conditions, high soil temperature has a positive or negative effect on the performance of free-living bacteria and the life of rhizobia. The optimum temperature for
growth in the medium is 28–30 °C, and many are unable to grow at 38 °C. Nevertheless, some strains of rhizobia from the woody legumes are grown well at 40 or
44 °C. Additionally, increased soil temperature leads to form ineffective nodules,
but R. leguminosarum bv. Phaseoli exhibit higher heat tolerance and can form effective nodule with their host legumes [45]. In Egyptian soils, the optimum activity of
nitrogen-fixing Azotobacter and Clostridium occurred when soil temperature raised