The history of the Black Mountains in North Carolina and the southern Spruce-Fir ecosystem has been fraught with widespread forest decline since the mid 1960’s. Balsam Woolly Adelgid attacks and acidic deposition wer...The history of the Black Mountains in North Carolina and the southern Spruce-Fir ecosystem has been fraught with widespread forest decline since the mid 1960’s. Balsam Woolly Adelgid attacks and acidic deposition were two of the most recognized causes of decline. Uncertainty arose about the future of these forests, and projections were made regarding the endangerment or extinction of the endemic Fraser fir ([Pursh] Poiret). This study analyzed data sets from a permanent plot network in the Black Mountains dating 1985, 2002, and 2012. Indications that the Fraser fir population is stabilizing from a “boom-bust” cycle of population growth and has entered the stem exclusion stage of forest stand development are evident. Fir live stem density increased more than 250% from 1985 to 2002, and then declined 40% by 2012 at the highest elevations in the forest. Overall, fir appeared to be more impacted on western facing slopes than eastern ones. The population of red spruce experienced a steady decrease in live stem counts, but an increase in live basal area through all years, and at all elevation classes (1675 m, 1830 m, and 1980 m), indicating a normal progression through stand development. Red spruce was also most negatively impacted on western facing slopes. Live stem density was significantly higher (P 0.001) than eastern plots, but live basal area was similar between the two aspects. Atmospheric deposition concentrations of the four main acidic molecules at Mt. Mitchell all peaked in 1998, but decreased by 2012. These reductions, occurring shortly after tightened regulations in the 1990 amendments to the Clean Air Act may have potential implications for increased forest resilience.展开更多
As one of the main food bamboo species of the giant panda(Ailuropoda melanoleuca),Fargesia denudata is widely distributed in the understory of spruce-fir forests in the mountainous area of southwestern China.However,t...As one of the main food bamboo species of the giant panda(Ailuropoda melanoleuca),Fargesia denudata is widely distributed in the understory of spruce-fir forests in the mountainous area of southwestern China.However,the driving factors of its biomass and distribution in the forests are still unclear.We conducted a systematic investigation of the tree and shrub layers(including bamboos)of 209 subplots(20 m×20 m)in a Forest Global Earth Observatory plot,the Wanglang Plot(25.2 ha),to explore the effects of abiotic(topographic and soil characteristics)and biotic(tree density,total basal area(TBA),shrub coverage,etc.)factors on the aboveground biomass of F.denudata(bamboo biomass hereafter).Bamboo biomass averaged 1.17 ton/ha,with a large variation from 0 to 4.88 ton/ha(95%confidence interval)among the 209 subplots.Bamboo biomass increased significantly with elevation,slope and mean diameter at breast height of trees,and decreased significantly with tree density,shrub coverage and soil pH.However,bamboo biomass was not significantly correlated with tree TBA,aspect,soil organic matter or total nitrogen content.The random forest model indicated that topographic factors and biotic factors had greater influences on the bamboo biomass than soil characteristics in general.Specifically,topographic factors mainly affected the bamboo biomass by changing tree density and soil characteristics.Our results can provide valuable guidance for the protection of giant pandas and the management of subalpine spruce-fir forests.展开更多
文摘The history of the Black Mountains in North Carolina and the southern Spruce-Fir ecosystem has been fraught with widespread forest decline since the mid 1960’s. Balsam Woolly Adelgid attacks and acidic deposition were two of the most recognized causes of decline. Uncertainty arose about the future of these forests, and projections were made regarding the endangerment or extinction of the endemic Fraser fir ([Pursh] Poiret). This study analyzed data sets from a permanent plot network in the Black Mountains dating 1985, 2002, and 2012. Indications that the Fraser fir population is stabilizing from a “boom-bust” cycle of population growth and has entered the stem exclusion stage of forest stand development are evident. Fir live stem density increased more than 250% from 1985 to 2002, and then declined 40% by 2012 at the highest elevations in the forest. Overall, fir appeared to be more impacted on western facing slopes than eastern ones. The population of red spruce experienced a steady decrease in live stem counts, but an increase in live basal area through all years, and at all elevation classes (1675 m, 1830 m, and 1980 m), indicating a normal progression through stand development. Red spruce was also most negatively impacted on western facing slopes. Live stem density was significantly higher (P 0.001) than eastern plots, but live basal area was similar between the two aspects. Atmospheric deposition concentrations of the four main acidic molecules at Mt. Mitchell all peaked in 1998, but decreased by 2012. These reductions, occurring shortly after tightened regulations in the 1990 amendments to the Clean Air Act may have potential implications for increased forest resilience.
基金supported by the National Natural Science Foundation of China(31988102)the National Key Research and Development Program of China(2017YFC0503906).
文摘As one of the main food bamboo species of the giant panda(Ailuropoda melanoleuca),Fargesia denudata is widely distributed in the understory of spruce-fir forests in the mountainous area of southwestern China.However,the driving factors of its biomass and distribution in the forests are still unclear.We conducted a systematic investigation of the tree and shrub layers(including bamboos)of 209 subplots(20 m×20 m)in a Forest Global Earth Observatory plot,the Wanglang Plot(25.2 ha),to explore the effects of abiotic(topographic and soil characteristics)and biotic(tree density,total basal area(TBA),shrub coverage,etc.)factors on the aboveground biomass of F.denudata(bamboo biomass hereafter).Bamboo biomass averaged 1.17 ton/ha,with a large variation from 0 to 4.88 ton/ha(95%confidence interval)among the 209 subplots.Bamboo biomass increased significantly with elevation,slope and mean diameter at breast height of trees,and decreased significantly with tree density,shrub coverage and soil pH.However,bamboo biomass was not significantly correlated with tree TBA,aspect,soil organic matter or total nitrogen content.The random forest model indicated that topographic factors and biotic factors had greater influences on the bamboo biomass than soil characteristics in general.Specifically,topographic factors mainly affected the bamboo biomass by changing tree density and soil characteristics.Our results can provide valuable guidance for the protection of giant pandas and the management of subalpine spruce-fir forests.
