Determination the Effect of Altitude Gradient on Quantitative Characteristics of Forest Stands (Case Study: District-3 of Sangdeh Forests)

Estimating the biomass and carbon content of trees and the other crops is important, in particular in context of global warming and climate change resilience and the determination of biomass in order to influence the climate and management of natural resources is essential. In forest areas with high altitudinal gradients, values of the quantitative characteristics of forest stands usually change. The purpose of this study was to determine the effect of altitudinal gradient on quantitative forest characteristics including number per hectare, basal area, standing volume, biomass and carbon storage in District-3 of Sangdeh Forests.

The area was initially divided into three altitudinal levels, with a range of 1600-1400, 1600-1800 and 1800-2000 m altitude sea level 50 circular sample plots were randomly assigned to each level, resulting in a total sampled area of 10 ares (0.1ha) to cover each level. In each plot, species type, height and diameter at breast height were recorded for all trees with DBH > 7.5 cm. Then, the density of all species was determined by sampling followed by further analysis in laboratory. Then, the biomass was calculated in the sample plots based on the FAO global model.

The results showed that altitude gradient from the bottom up, the number of trees per ha of 477, 384 and 372, the basal area of 25.58, 29.49 and 30.84 m2, respectively. Also the volume per ha were estimated to be of 314.25, 393.98 and 424.75 silve, respectively. The results this research showed the amount of AGB for all three altitudinal levels based on gradient increase is 406.68, 478.26 and 522.30 t ha-1, and carbon stock of 203/34, 239/12, and 261/15 ton per hectare, respectively, that shows an upward trend as the a.s.l. increases. The analysis of variance indicated a significant difference between the altitude and the characteristics (P < 0.05). In addition, Spearman correlation showed that there was a significant correlation between altitude and tree characteristics, basal area, standing volume, aboveground biomass per ha (p<0.01).

Conclusively, the results of this research in the study area show that changes in altitude from the sea level have caused changes in some of the quantitative characteristics and thus the elevation gradient has been effective on the distribution of AGB, so that with increasing a.s.l, the amount of AGB has also increased and AGB has the highest correlation with the altitude from the sea level.