Yes, you better re-wet the sample adding double distilled water equivalent to 50-75% water holding capacity of soil and then incubate the soil for 24-48h at 28 -30 degree Celsius to revive the microbial activity. We find that you will get as good as original activity . The difference may be only 2-5% , which is acceptable.

Interesting work, please have a look...

The effect of storage on microbial activity and bacterial community structure of drained and flooded paddy soil by Wang, J., Chapman, S.J. & Yao, H. J Soils Sediments (2015) 15: 880. doi:10.1007/s11368-014-1053-7

Purpose : Logistics and time demands necessitate soil storage under laboratory conditions after sampling because soil properties cannot always be determined immediately. There have been a number of studies about the effects of storage on biophysical properties; however, there has been little reference to paddy soils, which experience the alternation of wetting and drying phases. Our aims were to determine the impacts of sample storage on microbial activity and community structure in paddy field soil.

Materials and methods: We pre-incubated paddy soil to reach two states: flooded (F) and drained (D). Samples were then stored at −20 and 4 °C or air-dried. After 30 days, one part of the stored soils was used to measure key soil indices and the other part of the soil was incubated for 7 days prior to reassessment. Total phospholipid fatty acid (PLFA) was used to characterize the microbial biomass. MicroResp™ and Illumina next-generation sequencing techniques were adopted to analyze the change of microbial community activity and structure, respectively.

Results and discussion: Results showed that the various storage treatments did not affect the total PLFA in drained and flooded soil except for the flooded soil stored at 4 °C. Basal respiration was unusually increased in the drained soil after storage but recovered after a 7-day re-incubation. In contrast, the impact on flooded soils was minimal. Further, the soil community-level physiological profile (CLPP) was affected by storage, but microbial community structure remained mostly unchanged. Sequencing also showed that α diversity of the flooded paddy soil was higher than that in the drained soil.

Conclusions: The effect of storage on drained paddy soil using these indices was mainly consistent with previous studies on non-flooded cultivated soils, while the effect on flooded soil suggested a different mechanism from that in drained soil. Although the microbial function and community structure were different between drained and flooded paddy soils, the various storage approaches all altered the microbial functional structure to some extent but kept the microbial community structure largely intact.

I tried preserving soil in 4 degrees  for 1 month. I noted an average decrease of approx. 10-15 % BACTERIAL count.  Definitely this will affect the respiration rate and related parameters

Dr. Mugla, as I stated , you have to re-wet the soil as described to brings into original condition. I am sure if your soil is less than two years stored, you may find below 5% difference from the original. We are getting this results in routine in arid soils ( Aridisols).

Dr Tarafdar, It might be a good ESTIMATION by the method of re-wetting and incubate.  The bulk density and Organic matter content will definitely play a vital role in it.

Bulk density may not be that important but definitely organic matter play a major role. I am talking about the soils where organic matter content is always less than 0.5%.

Yes surely for the organic matter.  But the degree of compaction do modify the readings, in case of aerobes... 

Dr. Mungla, our soil is sandy to sandy loam. There, we find, it does not matter much where sand percent is more than 80. But may be you may get compaction effect on clay soil.

In that case.. yes the estimation using re-wetting might be a good estimation.