الفقد الكتلي والتغير في تركيز المغذيات خلال تحلل أوراق أشجار الصنوبر الحلبي النامية في ترب الجبل الأخضر

Abstract

The aims of the present study were to determine Mass loss (ML%) and the changes patterns of Holocellulose (cellulose , hemicelluloses) , Lignin (Non- hydrolysable Residues; NHR), water and Ethanol- Solubles as well as the dynamics of N, P, Na , K , Ca , Mg , Mn , SO4, NO3. The concentration of N in Lignin C:N , Lignin:N and C:P were also determined .The influence of site properties on these parameters (Responses) were evaluated. To achieve these aims , the litter bag technique, which is a wellknown tool for the study of litter decomposition, was applied using bags of 10X10 cm dimentions and with 1mm diameter. The required numbers of the bags were fixed on the bottom of each Aleppo pine (Pinus halepensis Mill.) stands grown in three sites located at 410, 630, and 860m. a. s. l. of the Jabal Alakhdar eco- region, Libya by using a split design system in Four plots. The experiments started in 1.10.2006 and conducted for 18, 10 and 7 months the latter 2 plots Located at 860 m. a. s. l. The data obtained were statistically assessed using ANOVA, Correlation and Regression analysis. The ML (%) values were ca 25, after 7 months of decomposition with significant differences (P.0.05); after 10 months, these values increased to 31% in the stands located at 410 and 630 m. a. s. l. and both were significantly differed with (P.0.05) compared to the stands located at 860 m. a. s. l (ML of ca 20%) . ML Values reached 60% and 43% after 18 months in stands located at 410 and 630 m. a. s. l. respectively and were significantly differed (P.0.05); the water- and ethanol-solubles were significantly differed and decreased from ca 14% and 25% to ca 10% and 18% after 18 months of incubation (decomposition). However, the lignin (NHR) increased from 32 to 38% at both sites, whereas the holocelluloses increased from 27% to 33 and 29% respectively. The total concentration of carbon decreased from 48 to 46 % in both sites and this means that the loss of carbon did not exceed 2% after one and half year of decomposition and consequently the emission of CO2 was low under such pine forest systems. On the other hand, the total N increased up to 1.1 % confirming the fact of the chemical combination of nitrogen (as NH3) to the aromatic rings exposed during the biodegradation of lignin. Total phosphorus decreased from 0.23 to 0.1 and 0.07% in sites located respectively at 410 and 630 m. a. s. l. and no changes of total potassium were observed in both sites. Negative and positive r values between some responses were observed (P.0.05) and some values of R2 above ca 60 % were also noticed. Finally, it is of highly importance to wisely expand the area of Aleppo pine plantations in the bared localities spread in this eco-region. This is for increasing the contribution of such pin forest systems of carbon dioxide capturing and retarding its emission to the atmosphere of our green and fragile planet to reduce the tragedy of the global warming phenomenon.