Studies on Plant Community Complexity in Fenced Region of Ningxia, Northern China

Biocomplexity theory is becoming increasingly important in understanding natural vegetation dynamics and interrelation among all components of ecosystems. A study was conducted under this concept in order to investigate the impacts of different fencing periods and measures on plant community complexity in desert grasslands of Yanchi County of Ningxia Hui Autonomous Region. The study was carried out by using a quadrat method and based on the average length of the Huffman code to describe total complexity L(S), Rényi entropy H(S) as disorder-based complexity, and the difference D (S) = L(S)-H(S) as structural complexity. The relationship was also studied between three kinds of complexity index and the number of species, Importance value of dominant species. The results showed that enclosure increases disorder-based complexity index and structural complexity index, which makes total complexity index to increase. Therefore, fencing is an effective measure for vegetation restoration and rehabilitation while long-term fencing is not conducive to vegetation restoration. In this study disorder-based complexity index is higher than structural complexity index, which means that disorder-based complexity index has great effects on total complexity index. The relationship between L(S ) and H(S) is very close whereas the correlation between H(S) and D(S) is negative. There is significant relationship between the number of species and the three kinds of complexity index. The importance value of dominant species is not significantly correlated with structural complexity, which has significant negative correlation with the other indices.