For a graph G, let D denote an orientation of G having minimum diameter. Define f（G） =diamD. In this paper, we concentrate on exploring the minimum diameter of Km ∨ Kn（m ≥ 1, n ≥ 1）. Some special cases are know...For a graph G, let D denote an orientation of G having minimum diameter. Define f（G） =diamD. In this paper, we concentrate on exploring the minimum diameter of Km ∨ Kn（m ≥ 1, n ≥ 1）. Some special cases are known： f（Km ∨ Kn） = ∞, 2, 3, where m = landn ≥ 1, m = 2 or m ≥ 4 andn = 1, m=3 and n = 1, respectively. So we only consider the case when m ≥ 2 and n ≥ 2. The following results are obtained. （1） f（Km ∨ Kn） = 3, where m = 2, 3, n ≥ 2 and m = n = 4. （2） f（Km ∨ Kn） = 2, m where m ≥ 5 andmisodd, 2 ≤ n ≤ （m[m/2]）-m. （3） f（Km ∨ Kn） = 2, whereto ≥ 4 and m≡ 0（rood4）, 2 ≤ n ≤ （m m/2）-（m/2＋1）. （4） ]（Km ∨ Kn） = 2, where m ≥ 6 and m ≡ 2（mod4）, 2 ≤ n ≤ （m m/2）-m/2. （5）/（Km ∨ Kn） = 3, where m ≥ 4, n 〉 （m[m/2]）.展开更多
This study of the impact of heart rot of <i><span style="font-family:Verdana;">Pericopsis elata</span></i><span style="font-family:Verdana;"> on logging yield was cond...This study of the impact of heart rot of <i><span style="font-family:Verdana;">Pericopsis elata</span></i><span style="font-family:Verdana;"> on logging yield was conducted in Libongo, in three logging concessions of the </span><i><span style="font-family:Verdana;">Société d'Exploitation Forestière et Agricole du Cameroun</span></i><span style="font-family:Verdana;"> (SEFAC). An inventory of 92 </span><i><span style="font-family:Verdana;">P. elata</span></i><span style="font-family:Verdana;"> stumps in four Annual Cutting Areas (AACs) divided among three Forest Management Units (FMUs) distinguished by Minimum Operating Diameter </span><span style="font-family:Verdana;">(MOD) revealed that 22 stumps were rotten. Decay was visible on stumps wit</span><span style="font-family:Verdana;">h a diameter of more than 100 cm with a frequency of occurrence of 23.91%, a percentage of abandonment of 55.20% and a yield of 44.79%. The most important economic loss was revealed on 9 abandoned whole logs that cumu</span><span><span style="font-family:Verdana;">lated a volume of 145.547 m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">. The correlation between the diameter of the</span></span><span style="font-family:Verdana;"> stumps and that of the decay gives a coefficient or correlation rate r = 0.31. The MOD for </span><i><span style="font-family:Verdana;">P. elata</span></i><span style="font-family:Verdana;"> could be 80 cm and covers the biological risk class. The results indicate that </span><i><span style="font-family:Verdana;">P. elata</span></i><span style="font-family:Verdana;"> shows an increasing gradient of decay rate with increasing tree diameter, resulting in a loss of material for larger diameter trees, and consequently a decrease in material yield at processing.</span>展开更多
Forest degradation and biomass damage resulting from logging is currently difficult to evaluate with satellite images, but contributes substantially to carbon emissions in the tropics. To address this situation, we mo...Forest degradation and biomass damage resulting from logging is currently difficult to evaluate with satellite images, but contributes substantially to carbon emissions in the tropics. To address this situation, we modelled how changes in the minimum felling diameter affect stem density, basal area and the related carbon biomass at the end of the felling cycle （30 years） in a semi-deciduous natural forest in Cameroon. With new MFDs estimates, at 7% logging damage rate, we found that the stem density of initially harvestable trees reduces from 12.3 （50.4 MgC·ha^-1） to 6.7 （32.5 MgC·ha^-1） trees per ha and the number of initial residual trees increases from 80 （18.9MgC·ha^-1） to 85.7 （36.8 MgC·ha^-1） trees per ha. This corresponds to an avoided damage estimated at 17.9 MgC·ha^-1. We also found that increasing mortality and damage intensity also increases the damage on carbon biomass estimated to be 8.9 MgC·ha^-1 at 10% or to be 17.4 MgC.hal at 15% logging damage. Overall, our study shows that proper determination of MFD of logged species taking into consideration their capacity of reconstitution and the Reduced Impact Logging can avoid the loss of up to 35 MgC·ha^-1.展开更多
基金the National Natural Science Foundation of China(10671095)
文摘For a graph G, let D denote an orientation of G having minimum diameter. Define f（G） =diamD. In this paper, we concentrate on exploring the minimum diameter of Km ∨ Kn（m ≥ 1, n ≥ 1）. Some special cases are known： f（Km ∨ Kn） = ∞, 2, 3, where m = landn ≥ 1, m = 2 or m ≥ 4 andn = 1, m=3 and n = 1, respectively. So we only consider the case when m ≥ 2 and n ≥ 2. The following results are obtained. （1） f（Km ∨ Kn） = 3, where m = 2, 3, n ≥ 2 and m = n = 4. （2） f（Km ∨ Kn） = 2, m where m ≥ 5 andmisodd, 2 ≤ n ≤ （m[m/2]）-m. （3） f（Km ∨ Kn） = 2, whereto ≥ 4 and m≡ 0（rood4）, 2 ≤ n ≤ （m m/2）-（m/2＋1）. （4） ]（Km ∨ Kn） = 2, where m ≥ 6 and m ≡ 2（mod4）, 2 ≤ n ≤ （m m/2）-m/2. （5）/（Km ∨ Kn） = 3, where m ≥ 4, n 〉 （m[m/2]）.
文摘This study of the impact of heart rot of <i><span style="font-family:Verdana;">Pericopsis elata</span></i><span style="font-family:Verdana;"> on logging yield was conducted in Libongo, in three logging concessions of the </span><i><span style="font-family:Verdana;">Société d'Exploitation Forestière et Agricole du Cameroun</span></i><span style="font-family:Verdana;"> (SEFAC). An inventory of 92 </span><i><span style="font-family:Verdana;">P. elata</span></i><span style="font-family:Verdana;"> stumps in four Annual Cutting Areas (AACs) divided among three Forest Management Units (FMUs) distinguished by Minimum Operating Diameter </span><span style="font-family:Verdana;">(MOD) revealed that 22 stumps were rotten. Decay was visible on stumps wit</span><span style="font-family:Verdana;">h a diameter of more than 100 cm with a frequency of occurrence of 23.91%, a percentage of abandonment of 55.20% and a yield of 44.79%. The most important economic loss was revealed on 9 abandoned whole logs that cumu</span><span><span style="font-family:Verdana;">lated a volume of 145.547 m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">. The correlation between the diameter of the</span></span><span style="font-family:Verdana;"> stumps and that of the decay gives a coefficient or correlation rate r = 0.31. The MOD for </span><i><span style="font-family:Verdana;">P. elata</span></i><span style="font-family:Verdana;"> could be 80 cm and covers the biological risk class. The results indicate that </span><i><span style="font-family:Verdana;">P. elata</span></i><span style="font-family:Verdana;"> shows an increasing gradient of decay rate with increasing tree diameter, resulting in a loss of material for larger diameter trees, and consequently a decrease in material yield at processing.</span>
文摘Forest degradation and biomass damage resulting from logging is currently difficult to evaluate with satellite images, but contributes substantially to carbon emissions in the tropics. To address this situation, we modelled how changes in the minimum felling diameter affect stem density, basal area and the related carbon biomass at the end of the felling cycle （30 years） in a semi-deciduous natural forest in Cameroon. With new MFDs estimates, at 7% logging damage rate, we found that the stem density of initially harvestable trees reduces from 12.3 （50.4 MgC·ha^-1） to 6.7 （32.5 MgC·ha^-1） trees per ha and the number of initial residual trees increases from 80 （18.9MgC·ha^-1） to 85.7 （36.8 MgC·ha^-1） trees per ha. This corresponds to an avoided damage estimated at 17.9 MgC·ha^-1. We also found that increasing mortality and damage intensity also increases the damage on carbon biomass estimated to be 8.9 MgC·ha^-1 at 10% or to be 17.4 MgC.hal at 15% logging damage. Overall, our study shows that proper determination of MFD of logged species taking into consideration their capacity of reconstitution and the Reduced Impact Logging can avoid the loss of up to 35 MgC·ha^-1.
