| Pinus massoniana is an important tree species that occures at early stage of secondary forest succession after disturbance and is widely used for plantations in subtropical China. The data of national forest inventory in 2009 showed that total stand area of Pinus massoniana forests in China reached 1.20×109hm2 and stock volume was 5.88×1010m3. Hence, P. massoniana plays vital roles in wood and non-wood production, ecosystem services including carbon (C) sequestration at regional scale. Stand biomass of different age classes estimated from sampling plots and volume conversion function were used to determine total stand biomass of P. massioniana forest in Hunan Province, based on the data of forest inventory during the period from 1983 to 2009. Stand area distribution of 5 age classes was analyzed for P. massioniana forests in Hunan as estimated. The main results showed as follows:(1) Stand biomass of P. massoniana forest were averaged to 13.75t·hm-2 for young age class,34.83t·hm-2 for middle age class,54.83t·hm-2 for nearly mature age class, and 91.22t·hm-2 for mature age class. These data indicated that P. massoniana forest had great growth potential before they were mature.(2) Total biomass of P. massioniana forest during the period from 1983 to 2009 estimated by the method of biomass expansion factor (BEF) in Hunan Province were 38.55×106t (1983-1987),51.19×106t (1990-1995),44.06×106t (1996-1999),69.50 × 106t (2000-2004), and 35.58 X 106t (2005-2009), respectively. In general, total forest biomass in those 5 ages decreased from 1983-1987 (38.55×106t) to 2005-2009 (35.58× 106t), and it also decreasing from (1996-1999) to (2005-2009), negative growth rates were 13.92% and 48.80%, though, it decreased from 1990-1995 to 2004-2009, growth rates were 32.78% and57.73% respectively, and then reached the highest in 2004. Total biomass of P. massioniana forests in 1983-2009 estimate by method of allometric equations (AE) in Hunan Province were 43.43×106t (1983-1987); 45.36×106t (1990-1995); 72.51×106t (1996-1999); 90.61×106t (2000-2004); 54.56×106t (2005-2009)respectively, it increased from 43.43×106t at the age of 1983-1987 to 90.61 × 106t at the age of 2005-2009, growth rate was 52.06%, total biomass until the age of 2005-2009 began to decrease, from 90.61 × 106t decreased to54.56 × 106t, negative growth rate was 36.78%。(3) There were different of the change of P. massoniana biomass estimated by two methods, so we took the average value of those two methods to analyze biomass change trend of P. massoniana in different ages. Total biomass of P. massoniana forest in Hunan province increased from 40.87 ×106 to 80.06×106 t in past 25 years, and it increasing in 1983-2004 from 1.31×106t to 22.26×106t, mainly due to the increasing area and biomass of nearly mature and mature forests. Large variations in total biomass were found for 14 cities at prefecture level during the inventory period in past 25 years. In general, total forest biomass in each city increased from 1983 to 1985, through decreasing from 1995 to 1999, and then reached the highest in 2004. In 2009, a decrease was found for each city.(4) The regression analysis indicated that the percentage of forest area of stand age classes affected total biomass of P. massoniana forests and the percentage of mature and over-mature stand had greater effects relative to other stand age classes. The changes in percentage of forest area of age classes significantly affected the changes in total forest biomass. Therefore, adjustment of stand age structure and old forest protection could improve total forest biomass at regional scale.The biomass in Hunan Province increased first and then decreased with time changed from 1987 to 2004 and to 2009, although the area of young age class forests decreased and total area of 5 age classes of P. massioniana forests increased in 2009 compared with that in 1987, Therefore, P. massioniana forests in Hunan had a great potential to increase biomass in future if sustainable forest management would be carried out. |
PDF Full Text Request