Disturbances that create gaps can shape the structure and function of forests. However, such disturbance regimes in Asian tropical montane rainforests remain largely unquantified. Least studied are typhoon disturbance...Disturbances that create gaps can shape the structure and function of forests. However, such disturbance regimes in Asian tropical montane rainforests remain largely unquantified. Least studied are typhoon disturbances that are attributable to climate change. We investigated gap characteristics in terms of size, age, and gap-maker to quantify the gap disturbance regimes in an intact old-growth tropical montane rainforest on Hainan Island, China. The intensity of typhoons has increased since 1949, and typhoon winds blow mostly (45.5%) from the northeast corner of Hainan Island, resulting in a higher frequency of gaps in the northeast. A total of 221 gap-makers (trees that fell to create canopy gaps) and 53 gaps were observed in a 3.16 ha old-growth rainforest. Most canopy gaps (85%) were < 200 m(2). The average size of canopy gaps was smaller in the rainforest than in other tropical forests, while the average size of expanded gaps was similar to those in other tropical forests. The maximum age of gaps was 23.5 years indicating that gaps had more rapid turnover than other parts of tropical forests. The frequency distribution of gap-makers followed a lognormal distribution with a distinctive peak at three gap-makers, which was different from the inverse J-shaped curve typical of other tropical forests. Gaps were recorded mainly on slopes between 20A degrees and 35A degrees and wood density of gap-makers was between 0.6 and 0.7 g cm(-3). Our results suggest that small-scale disturbance was the dominant agent of gap formation in this old-growth rainforest that is subject to increasing typhoon disturbances.展开更多
The present study is an attempt to investigate the impact of climate changes on quantitative and qualitative growth of oak trees in central Zagros region. After we selected the study region, 35 discs were taken from t...The present study is an attempt to investigate the impact of climate changes on quantitative and qualitative growth of oak trees in central Zagros region. After we selected the study region, 35 discs were taken from trees felled in each height class (e.g. 1400 - 1600, 1600 - 1800, 1800 - 2000 m above the sea level). We used climate index spi. For the data analysis, we employed SPSS software and inferential statistics tests of Kolmogroff Smirnov and the one-way ANOVA. During the recent 15 years, rainfall has shown a decreasing trend and amount of haze and frequency of occurring haze has been increased. The ANOVA results indicated that diameter growth of trees in three height classes revealed a significant difference. The average annual diameter growth in the first, second and third classes were 1.8 mm, 2.5 mm, and 2.2 mm, respectively. Additionally, the results indicated that hillsides and slope aspect has a statistically meaningful effect on the size of canopy area, basal area and number per hectare. Several different studies have reported that during the recent 15 years, qualitative and quantitative growth of central Zagros oak trees strongly correlate with climate parameters in the three habitats.展开更多
Growth of commercial forestry is highly dependent on the availability of fast-growing planting materials. Consequently, the efficient utilization of fastgrowing plantations can greatly impact productivity. The objecti...Growth of commercial forestry is highly dependent on the availability of fast-growing planting materials. Consequently, the efficient utilization of fastgrowing plantations can greatly impact productivity. The objectives of this study were to evaluate variations in the growth potential of two clones and to estimate the average stem radial growth advantage of a fast-growing clone using data obtained from Sappi landholdings in eastern South Africa and a mixed modelling approach that permits the incorporation of covariance structure into the statistical model. During the first 2 years of growth, the stem radius of nine trees each of two clones was measured using dendrometer attached to the tree. A second-degree fractional polynomial model was chosen to show the functional relationship between stem radius and tree age. Growth of the two hybrid clones differed significantly. The Eucalyptus grandis×Eucalyptus urophylla clone grew faster than the E. grandis×camaldulensis clone, indicating better genetic potential for rapid growth and yield. This study can be considered as starting point to further compare the potential for rapid growth of several hybrid clones using the longitudinal data modelling approach.展开更多
基金supported by the Ministry of Science and Technology(2012BAD22B01 and 2006BAD03A04)special funds of Research Institute of Tropical Forestry,Chinese Academy of Forestry(RITFYWZX2012-02CAFYBB2014QA010)
文摘Disturbances that create gaps can shape the structure and function of forests. However, such disturbance regimes in Asian tropical montane rainforests remain largely unquantified. Least studied are typhoon disturbances that are attributable to climate change. We investigated gap characteristics in terms of size, age, and gap-maker to quantify the gap disturbance regimes in an intact old-growth tropical montane rainforest on Hainan Island, China. The intensity of typhoons has increased since 1949, and typhoon winds blow mostly (45.5%) from the northeast corner of Hainan Island, resulting in a higher frequency of gaps in the northeast. A total of 221 gap-makers (trees that fell to create canopy gaps) and 53 gaps were observed in a 3.16 ha old-growth rainforest. Most canopy gaps (85%) were < 200 m(2). The average size of canopy gaps was smaller in the rainforest than in other tropical forests, while the average size of expanded gaps was similar to those in other tropical forests. The maximum age of gaps was 23.5 years indicating that gaps had more rapid turnover than other parts of tropical forests. The frequency distribution of gap-makers followed a lognormal distribution with a distinctive peak at three gap-makers, which was different from the inverse J-shaped curve typical of other tropical forests. Gaps were recorded mainly on slopes between 20A degrees and 35A degrees and wood density of gap-makers was between 0.6 and 0.7 g cm(-3). Our results suggest that small-scale disturbance was the dominant agent of gap formation in this old-growth rainforest that is subject to increasing typhoon disturbances.
文摘The present study is an attempt to investigate the impact of climate changes on quantitative and qualitative growth of oak trees in central Zagros region. After we selected the study region, 35 discs were taken from trees felled in each height class (e.g. 1400 - 1600, 1600 - 1800, 1800 - 2000 m above the sea level). We used climate index spi. For the data analysis, we employed SPSS software and inferential statistics tests of Kolmogroff Smirnov and the one-way ANOVA. During the recent 15 years, rainfall has shown a decreasing trend and amount of haze and frequency of occurring haze has been increased. The ANOVA results indicated that diameter growth of trees in three height classes revealed a significant difference. The average annual diameter growth in the first, second and third classes were 1.8 mm, 2.5 mm, and 2.2 mm, respectively. Additionally, the results indicated that hillsides and slope aspect has a statistically meaningful effect on the size of canopy area, basal area and number per hectare. Several different studies have reported that during the recent 15 years, qualitative and quantitative growth of central Zagros oak trees strongly correlate with climate parameters in the three habitats.
文摘Growth of commercial forestry is highly dependent on the availability of fast-growing planting materials. Consequently, the efficient utilization of fastgrowing plantations can greatly impact productivity. The objectives of this study were to evaluate variations in the growth potential of two clones and to estimate the average stem radial growth advantage of a fast-growing clone using data obtained from Sappi landholdings in eastern South Africa and a mixed modelling approach that permits the incorporation of covariance structure into the statistical model. During the first 2 years of growth, the stem radius of nine trees each of two clones was measured using dendrometer attached to the tree. A second-degree fractional polynomial model was chosen to show the functional relationship between stem radius and tree age. Growth of the two hybrid clones differed significantly. The Eucalyptus grandis×Eucalyptus urophylla clone grew faster than the E. grandis×camaldulensis clone, indicating better genetic potential for rapid growth and yield. This study can be considered as starting point to further compare the potential for rapid growth of several hybrid clones using the longitudinal data modelling approach.
