Considering the nonstationarity and information redundancy of living tree stem moisture signals in time domain, an approach of MP decomposition and reconstruction of living tree stem moisture signals based on Gabor atoms was presented. The experimental results showed that living tree stem moisture signals can be represented sparsely by Gabor atom library. The front of atoms reflected the main features of signal and the back of atoms reflected the subtle features of signal. The more the number of atoms was, the more the sparse signal can better represent the features of original time-domain signal. Compared with the original signal in time domain, the sparse signal had many advantages. Firstly, the length of sparse signal was reduced significantly. Secondly, the sparse signal can avoid information redundancy. So the approach of representing signal sparsely can achieve the purpose of data compression and save physical space to store a large amount of data. Under the condition of Gabor atom library being redundant, original time-domain signal can be constructed with high quality from the sparse signal. And reconstructive errors at the main feature points were larger than it at the subtle feature points.