Energy And Nutrient Characteristics Of The Dominant Plant Species In Ziwuling Forest Of The Loess Plateau

Caloric value and nutrient contents of dominant plant species and dominant companion species of six natural secondary forests plant communities was studied. The six communities are Hippophae rhamnoides community, Populus davidiana community, Betula platyphylla community, Pinus tabulaeformis community, Pinus tabulaeformisf.shekannesis community and Quercus liaotungensis community, respectively. The results are as followed:The mean gross caloric values of the dominant plants in the six communities were 18.97,19.19,19.23,19.80,19.74 and 18.09 kJ?g-1, and the ash free caloric value were 19.59,20.62,19.82,20.54,20.17 and 18.37 kJ?g-1, respectively. No matter gross caloric value or ash free caloric value, the mean caloric value of the Quercus liaotungensis was the lowest. The caloric value of the dominant plant species was increasing with the community succession, and this indicated that the trend of the energy utilization efficiency of the dominant plant species was increasing first and then decreasing as the community succession progressing. The caloric value varied significantly in the different parts of the six dominant plant species. Foliage is the most active organ of the plant, and its gross caloric value and ash free caloric value of foliage were significantly higher than the other organs (P< 0.05).The gross caloric values of the aboveground and underground parts of the species varied within different communities. The ash free caloric values of the aboveground and underground parts of the species tended to decline in different communities that experienced different succesional stages. The aboveground part of Carex lanceolata had the highest ash free caloric value in Sophora viciifolia community and the lowest ash free caloric value in Hippophae rhamnoides community. The underground part of Carex lanceolata had the highest ash free caloric value in Sophora viciifolia community and the lowest ash free caloric value in Quercus liaotungensis community. Generally speaking, the aboveground part of Carex lanceolata had a remarkably higher caloric value than the underground part of the species did. The caloric values of Carex lanceolata greatly varied in the communities going through their early successional stages (Sophora viciifolia, Hippophae rhamnoides, Populus davidiana and Betula platyphylla communities) and less greatly in the communities experiencing their later successional stages (Pinus tabulaeformis and Quercus liaotungensis communities).The organic matter of groundlitter was lower than litter fall and fresh stumpage in different communities. The caloric value of the groundlitter was lower than that of the litter fall and fresh stumpage in each community. The total N content of groundlitter in Hippophae rhamnoides communities was higher than in other communities. The ash content of groundlitter was also higher than litter fall and fresh stumpage. The groundlitter had higher energy returning velocity, energy content of different communities was higher than litter fall and fresh stumpage.The decomposition rates of the groundlitter of Pinus tabulaeformisf.shekannesis community, Pinus tabulaeformis and Quercus liaotungensis community which in the later succession stage were all higher than that of the communities which were in the early successional stage. Both the mean gross caloric value and the ash free caloric value of Pinus tabulaeformisf.shekannesis were relative high, which suggested that it had high energy utilization efficiency. We could deduce that the Pinus tabulaeformisf.shekannesis community may be in the middle or in the later succession stage through higher energy utilization and the result of the cluster analysis of caloric value and nutrient contents.