Methods of Estimating Forest Biomass: A Review | InTechOpen, Published on: 2017-02-22. Authors: Lei Shi and Shirong Liu

China harbors diversified forest types, from tropical rainforest to boreal coniferous forest, and has implemented large-scale reforestation/afforestation programs over the past several decades. However, little information is available on changes in China’s forest area and the causes. In this study, we used the classified forest distribution thematic map derived from Normalized Difference Vegetation Index (NDVI) datasets and a revised IPAT model to examine China’s forest area change and the possible driving factors from 1982 to 2006. Overall, NDVI-derived forest areas were numerically consistent with those reported in the 3^rd, 4^th, 5^th, and 6^th National Forest Inventories, respectively. Over the past 25 years, China’s forest area was estimated to have an average of 169.18 million hectares with an annual increase of 0.15 million hectares (c.a. a total net increment of 3.60 million hectares), which is equivalent to 0.089% of the relative annual change rate. However, a large difference in the changing rate and direction of forest area at the province level was found; for instance, forest area has declined in 10 provinces, mainly in Northeastern and Southern China, while 21 provinces showed an increase. The changes were most likely attributed to the policy regarding the import and export of timber and affluence (per capita gross domestic product), and both contributed more than 80% of the total contribution of the six factors of the revised IPAT model.

A severe winter storm from January to February 2008 caused considerable damage to the Nanling evergreen broad‐leaved forest. The sprout vigor of each species during postdisaster recovery plays a very important role in the succession trends of disturbed forests. In April 2008, four plots (50 × 30 m) were established in the Shierdushui Nature Reserve of Guangdong Province, China, to examine the damage status by the dominant species and diameters at breast height (DBHs), and the sprout response (indicated by the number of sprouts per stem) of the evergreen broad‐leaved forest to the severe winter storm. In contrast with freezing damage, the percentage of trees killed by mechanical damage from the mass of snow and ice was significantly higher (10% vs. 90%). More than 70% of the total dead trees had DBHs less than 4 cm. The impact of the severe winter storm in the tree layer was much more serious than in the shrub layer. Stem bending killed the highest percentage of trees, accounting for 59.53% of the total number of dead trees. The sprout number per stem differed significantly among damage types. The more severe damage induced a higher sprout number. Without considering the damage extent, significant differences in the sprout response were also found at both the dominant species and family levels. The tree layer exceeded the shrub layer in the mean number of sprouts (35.87 vs. 15.92). A bivariate correlation indicated that the sprout response was positively related to DBH and annual stem radial growth of the mother trees, implying that DBH and the growth rate of plant species most likely control the sprout response to disturbance in the subtropical evergreen broad‐leaved forests in the Nanling Mountains, southern China.