A species introduction experiment including several tropical pines and eucalypts was established in 1966/1967 in the Tchianga research station in Angolan Highlands. Despite 27 years of political conflict （1975-2002）...A species introduction experiment including several tropical pines and eucalypts was established in 1966/1967 in the Tchianga research station in Angolan Highlands. Despite 27 years of political conflict （1975-2002） and lack of management, the research experiment has remained relatively well conserved. We measured the best conserved plots that were 41 years old in 2007 to obtain information on the growth of different pine species. We calculated stand characteristics including basal area, dominant height, mean diameter, and stand volume for Pinus patula Schiede ex Schiltdl. Et Cham., Pinus pseudostrobus Lindl., Pinus kesiya Royle ex Gordon, Pinus devoniana Lindl., Pinus chiapensis （Martinez） Andresen, Pinus elliottii Engelm., Pinus greggii Engelm. Ex Parl., Pinus montezumae Lamb. and Pinus oocarpa Schiede ex Schltdl. The growing stock volume at 41 years was the highest in P. pseudostrobus, 1,325 m3^· ha^-1, followed by P. kesiya with 1,200 m^3· ha^-1. The widely planted P. patula had growing stock volume of 892 m^3· ha-^1. P. oocarpa and P. pseudostrobus had the highest stand basal area, over 80 m^2·ha^-1. Using increment core analyses we studied the temporal development of stand characteristics. Analysis of the mean annual increment （MAI） showed that rotation lengths of 20-30 years would maximize wood production. With these rotation lengths, the MAI of P. pseudostrobus would be 35 m^3· ha^-1. Other productive species were P. kesiya, P. ooearpa and P. chiapensis. P. patula had a maximum MAI of 20 m^3· ha^-1. P. greggii had the lowest mean annual volume production, only about 13 m^3· ha^-1.展开更多
Although fire is one of the most important disturbing factors of forest in Mexico, little it is known on the effects of fire on the particular Mexican forest ecosystems. This is remarked for the fact that the effects ...Although fire is one of the most important disturbing factors of forest in Mexico, little it is known on the effects of fire on the particular Mexican forest ecosystems. This is remarked for the fact that the effects of fires on vegetation vary among different types of forests. This lack of knowledge has constrained the use of fire, as a silvicultural tool. Therefore, the purpose of this project was to evaluate the effects of fire on regeneration, under burns. This work was carried out in a pine forest stand at Tapalpa Saw in Jalisco State, Mexico, dominated by Pinus michoacana and Pinus oocarpa. The study evaluated the effects of two techniques of prescribed burning: 1) backing, and 2) head fire. The sample plots were burned on 25 and 26 March 1991, before the rain season. One month before and 2 years after burning several measurements were made in order to evaluate the effect of fire on regeneration. Due to the limitations to work with “real” replicates (for treatments an control), original sample units (20 × 30 m) were divided into 5 × 5 m smaller sample units, which were considered as pseudoreplicants. Therefore, such analysis did not avoid introducing systematic error (bias) and minimize random error. Nevertheless, the variability within the pseudoreplicants was considerable in order to assume certain significance of the resulting estimations. Therefore, despite that this was a nonreplicated study;the results suggest strong ecological evidence that prescribed fire enhance natural regeneration of Pinus michoacana and Pinus oocarpa. In general, it is concluded that prescribed burning could be a valuable forest management tool in regions with similar conditions to the study area, in order to improve regeneration. However, further research is needed before prescribed fires can be applied with confidence in many Mexican forest conditions.展开更多
文摘A species introduction experiment including several tropical pines and eucalypts was established in 1966/1967 in the Tchianga research station in Angolan Highlands. Despite 27 years of political conflict （1975-2002） and lack of management, the research experiment has remained relatively well conserved. We measured the best conserved plots that were 41 years old in 2007 to obtain information on the growth of different pine species. We calculated stand characteristics including basal area, dominant height, mean diameter, and stand volume for Pinus patula Schiede ex Schiltdl. Et Cham., Pinus pseudostrobus Lindl., Pinus kesiya Royle ex Gordon, Pinus devoniana Lindl., Pinus chiapensis （Martinez） Andresen, Pinus elliottii Engelm., Pinus greggii Engelm. Ex Parl., Pinus montezumae Lamb. and Pinus oocarpa Schiede ex Schltdl. The growing stock volume at 41 years was the highest in P. pseudostrobus, 1,325 m3^· ha^-1, followed by P. kesiya with 1,200 m^3· ha^-1. The widely planted P. patula had growing stock volume of 892 m^3· ha-^1. P. oocarpa and P. pseudostrobus had the highest stand basal area, over 80 m^2·ha^-1. Using increment core analyses we studied the temporal development of stand characteristics. Analysis of the mean annual increment （MAI） showed that rotation lengths of 20-30 years would maximize wood production. With these rotation lengths, the MAI of P. pseudostrobus would be 35 m^3· ha^-1. Other productive species were P. kesiya, P. ooearpa and P. chiapensis. P. patula had a maximum MAI of 20 m^3· ha^-1. P. greggii had the lowest mean annual volume production, only about 13 m^3· ha^-1.
文摘Although fire is one of the most important disturbing factors of forest in Mexico, little it is known on the effects of fire on the particular Mexican forest ecosystems. This is remarked for the fact that the effects of fires on vegetation vary among different types of forests. This lack of knowledge has constrained the use of fire, as a silvicultural tool. Therefore, the purpose of this project was to evaluate the effects of fire on regeneration, under burns. This work was carried out in a pine forest stand at Tapalpa Saw in Jalisco State, Mexico, dominated by Pinus michoacana and Pinus oocarpa. The study evaluated the effects of two techniques of prescribed burning: 1) backing, and 2) head fire. The sample plots were burned on 25 and 26 March 1991, before the rain season. One month before and 2 years after burning several measurements were made in order to evaluate the effect of fire on regeneration. Due to the limitations to work with “real” replicates (for treatments an control), original sample units (20 × 30 m) were divided into 5 × 5 m smaller sample units, which were considered as pseudoreplicants. Therefore, such analysis did not avoid introducing systematic error (bias) and minimize random error. Nevertheless, the variability within the pseudoreplicants was considerable in order to assume certain significance of the resulting estimations. Therefore, despite that this was a nonreplicated study;the results suggest strong ecological evidence that prescribed fire enhance natural regeneration of Pinus michoacana and Pinus oocarpa. In general, it is concluded that prescribed burning could be a valuable forest management tool in regions with similar conditions to the study area, in order to improve regeneration. However, further research is needed before prescribed fires can be applied with confidence in many Mexican forest conditions.
