Influence of Solar Energy and Tree Crown Closure on Species Richness of Herbage in the South of Forest-Steppe
P. A. SHARY1, L. S. SHARAYA2, L. V. SIDYAKINA2, S. V. SAKSONOV2
1Institute of Physicochemical and Biological Problems in Soil Science, RAS, 142290, Pushchino, Institutskaya str., 2
2Institute of Volga Basin Ecology, RAS, 445003, Toliatti, Komzinа str., 10
Keywords: пространственная изменчивость, освещенность склонов, множественная регрессия, предсказательное моделирование, Spatial variability, slope insolation, multiple regression, predictive modeling
Abstract
Perpendicularity of solar rays incidence on land surface, termed slope insolation, is calculated as non-linear function of slope steepness and exposure. This variable better describes light and thermal regime of slopes. We demonstrate that grass cover insolation can be evaluated from slope insolation and tree crown closure. It was found for a terrain at the southern boundary of the forest-steppe that species richness and green mass of herbage were closely related to topography and insolation (R2 = 0.77 and 0.83, respectively), and crown closure - to topography and slope insolation from the south (R2 = 0.85). Soil moisture was in general negatively related to slope insolation. A critical level of crown closure (15 %) was determined, the limiting factor for herbaceous plants was soil moisture below this level, and light was above it. Grass cover insolation close to its average value (400 W/m2) differentiated phytocoenotic characteristics onto areas of increased and diminished values.
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