جستجوی مقالات مرتبط با کلیدواژه "سرو نقره ای" در نشریات گروه "جنگلداری"

Above ground and below ground biomass are important components of terrestrial ecosystem carbon stocks. Today, estimation of these components has crucial importance. For estimating aboveground and belowground woody plant biomass, Biomass Expansion Factors (BEF) and Root-Shoot Ratio (R) are the most applicable ratios. In this research, we assessed these ratios for estimation of above and belowground biomass of four tree species in Mobarake Steel Complex plantations. These four species comprise of two conifer and two broadleaves (eldar pine, arizona cypress, mulberry, black locust). For the aims of this study, 15 trees of each species were cut down and fresh biomass was measured in the field. Subsamples of fallen trees were taken and dry mass were measured at laboratory. Then, BEF and R were calculated. Using paired t test, actual and estimated above and belowground biomass were compared and result showed no significant difference. So, using these ratios is reliable for converting measured standing tree variables to biomass. Also, root-to-shoot ratio for Eldar Pine, Arizona Cypress, Mulberry, Black Locust was 1:4.5, 1:6.7, 1:3.7 and 1:3.5, respectively.

Considering the global warming and climate change topics, biomass estimation of trees has great importance in theory and application. Measurement of biomass is a costly and time consuming operation And to reduce these difficulties, a large numbers of sampling methods were innovated. One of these methods is the “subsampling”. In this research, accuracy of this sampling method for estimating biomass of total and different tree components of two planted coniferous species; Eldar pine (Pinus eldarica) and Arizona cypress (Cupressus arizonica) were examined in Mobarake Steel factory. Five sample trees from each species were felled down and each component of trees were separated and weighted. Therefore, actual biomass of different tree components was obtained. To test subsampling method, tree crown was divided to three parts, upper, lower and medial part and from each part, a number of branches were selected randomly and base diameter of every branch was recorded. Using nonlinear regression analysis, models of estimating biomass were obtained. The results showed that, all models were significant at 99.9% confidence level. The minimum and maximum coefficients of determination (r2) of these models were 0.8 and 0.92 for pine and 0.91 and 0.96 for arizona cypress respectively. The least and the most relative bias for pine belongs to estimation of total biomass (0.7%) and main branches (15.1%) and for arizona cypress belongs to estimation of main branches (4.9%) and small branches (29.4%). Based on the results, subsampling method is an appropriate method for estimating trees crown biomass.

Considering the climate change and global warming topics, importance of tree biomass and its measurement is increasing. Direct biomass measurement, especially for root section, is very costly, time consuming and difficult to implement. Usually, in such cases biomass can be estimated, using allometric equation. The aim of this research was to establish equations for estimating carbon content at above and below ground and whole tree biomass for four species, including Mulberry (Morus alba), Black Locust (Robinia pseudoacacia), Eldar Pine (Pinus eldarica) and Arizona cypress (Cupressus arizonica) planted around Mobarakeh Steel complex. For this purpose, 15 trees for each species (totally 60 trees) with appropriate diameter and height distribution, selected randomly and fell down and cut to different segments. Then the different components were separated and total fresh weight was measured at the field. Also roots of 20 trees fully excavated and after fresh weight measurement, some samples for dry weight determination were taken. Dry weight and carbon content of each sample were measured at laboratory. Allometric relationships between independent variables and carbon storage of different components and whole tree were established by nonlinear regression analysis. Overall, 96 models were derived for the four species and only eight of them were not statistically significant. The results showed that for Pine and Cypress, DBH (Diameter at Breast Height) and for Mulberry diameter at 0.3 m established models with highest coefficient of determination at all cases. For Black Locust, there was not special variable which can establish model with high coefficient of determination in all cases. For estimating the whole above- and below ground carbon storage of different organs, tree height had the highest coefficient of determination. Generally, concerning the both above and below ground biomass, modeling allometric relationships resulted in higher coefficient of determination of modeling for coniferous rather than for broadleaved species.

The main aim of the present research was to measure interception (I) by individual trees of Pinus eldarica and Cupressus arizonica that extensively planted in afforestation projects of the arid zone in Iran. The selected trees were located inside a forest plantation in a dry area at Semnan province, where mean annual precipitation and air temperature are 127 mm and 16˚C, respectively. The gross rainfall (GR) was measured by the mean of three hand-made gauges placed in an open area neighboring to the chosen trees. Five individual trees were selected for measurements of throughfall (TF). Eight TF collectors were positioned beneath the tree canopies in the four main directions to average into TF mean per species. I was calculated as the difference between GR and TF for each tree and I was finally averaged into the means of P. eldarica and C. arizonica. Measurements were made on a rainfall event basis during 2009 summer season, from March to October. The cumulative GR depth of 12 events was 37.9 mm; I (P. eldarica): 17.2 mm, and I (C. arizonica): 12.3 mm. On the event scale average ratios of I:GR were 68% (1.4 mm per event) and 55% (1 mm per event) for P.eldarica and C.arizonica, respectively. Strong positive correlations were observed between I and GR (P.eldarica, R2=0.94; C.arizonica, R2=0.87). Our measurements suggested that intercepted GR or I:GR ratio by the canopies, and loss through evaporation decreased, as the size of rainfall events increased. The results showed that interception is a significant component of the seasonal water balance in the afforestation of the arid zone of Iran.