An assessment of rainfall modification in mountainous ecosystems dominated by Fagus sylvatica L. and Picea abies (L.) Karst. (Western Balkans,Bulgaria) by multivariate analyses

Bulk precipitation, throughfall, and stemflow samples were collected in Petrohan site (Western Balkan, Bulgaria), operating in the framework of the Long-Term Ecological Research network, during a 6-year period (1995–2000). This mountain area is characterized by the presence of beech and spruce forests (Fagus sylvatica L. and Picea abies (L.) Karst.) and is utilized for drinking water supply. All samples were analyzed for pH and major inorganic anions (Cl^?, NO₃ ^?, and SO₄ ^2?) and cations (Ca²⁺, K⁺, Mg²⁺, Na⁺, and NH₄ ⁺). Results show that bulk precipitation in this region is mainly acidic (pH = 5.1), and the dominant neutralization components in the rainwater are Ca²⁺ and NH₄ ⁺. As for Ca²⁺, K⁺, Mg²⁺, Cl^?, and SO₄ ^2?, they are not originated by marine source. Cluster analysis and principal component analysis were used for investigating the possible sources contributing to the chemical composition of the bulk precipitation and its possible modifications during the passing through beech and spruce stands. Results highlight that local and long-range transport-related anthropogenic sources and natural sources contribute to the anion and cation content of the bulk precipitation. The enrichment of the solution through the foliage made up of dry depositions is significant in both stands, but canopy leaching processes are much greater in the spruce forest, especially for Ca²⁺. As for the stemflow, it follows the same pattern as the throughfall, but N uptake and a strong K⁺ and Mg²⁺ leaching are observed mainly in the spruce stand.     

Physiological mechanisms of resistance to cold stress associated with 10 elite apple rootstocks

A study was conducted in attempting to identify the cold-resistant apple rootstocks and to establish a comprehensive evaluation system. In this study, 10 elite apple dwarfing rootstocks(GM256, JM7, M26, M7, SC1, SH1, SH38, SH6, M9, and T337) were employed for the experiment and the following parameters were investigated under different low temperature stress conditions(0, –15, –20, –25, –30, and –35°C): the changes of the relative electrical conductivity(REC), anthocyanin content, protein content, soluble sugar content, soluble starch content, proline content, malondialdehyde(MDA) content, superoxide dismutase(SOD) activity, and peroxidase(POD) activity of the dormant branches. The inflection temperature that could represent the plant tissue semi-lethal temperature(LT_(50)) was obtained by the measurements of REC. The LT_(50) was used to evaluate eight other indices. The results showed that there was no significant correlation between LT_(50) and POD activity as well as between the soluble sugar, protein and proline contents at 0 and –15°C. Soluble starch content at 0 and –15°C and anthocyanin content at –15–(–30)°C were significantly but negatively correlated to the LT50 and the MDA content at 0–(–20)°C was significantly positively correlated to the LT_(50). Statistical analysis based on principal component analysis and LT50 showed that cold resistant apple rootstocks in the decreasing order from high to low as GM256, SH6, SH38, SH1, SC1, M26, M7, JM7, T337, and M9.