Rainfall partitioning and soil water dynamics along a tree species diversity gradient in a deciduous old-growth forest in Central Germany

摘要: Species diversity effects have been extensively investigated in grassland ecosystems, however, little is known about the influence of tree species diversity on forest water cycle. In this dissertation several hydrological processes including soil dynamics, rainfall partitioning and related ion deposition with along a tree gradient. addition, results were used to model The studies were conducted twelve study plots old-growth deciduous stands Hainich National Park, Germany. Monospecific formed by Fagus sylvatica (beech) mixed consisted variable admixture up eleven broad-leaved deciduous such as Tilia spec., Fraxinus excelsior, Carpinus betulus, Acer pseudoplatanus. first part thesis presents of into throughfall, stemflow, interception demonstrated that several stand characteristics influenced partitioning. major explaining throughfall for different seasons was expressed Shannon index. For example, high-rainfall summer 2007, median per plot between 66% 77% gross precipitation correlated positively the index plots. Stemflow contributed only 2% 6% negatively Interception showed no correlation beech forest These relationships similar summer 2005 autumn 2006, yet (or weak) correlations observed during other periods. Multiple linear regressions supported assumption that combinations characteristics important differences among plots, mean diameter at breast height. Influential stand varied years due to conditions. Differences in small-scale heterogeneity within did not change consistently any characteristic second focuses on dynamics Overall, seasonal patterns water all During a desiccation period top content strongly species At beginning period, extracted at higher rates rich than beech-dominated However, later when atmospheric evaporative demand higher, able further increase extraction. On high diversity, reserves already low extraction reduced. Possible explanations mixed beginning desiccation include specific as maximum use rate some species, enhanced exploitation resources stands (complementarity effect), additional herb layer, which increased small-scale volumetric within any third ion deposition processes, i.e. interception canopy exchange, Precipitation (throughfall plus stemflow) ions Na+, Cl-, K+, Ca2+, Mg2+, PO43-, SO42-, H+, Mn2+, Al3+, Fe2+, NH4+, NO3- Norg measured nine Interception exchange calculated budget model. except SO42- decreased increasing whereas leaching Cl- PO43- increased increasing diversity. Stand Mg2+ and Mn2+ H+ Possible reasons are status leaves, physiology, soil characteristics. conclusion, nutrient input monospecific acid was highest forth part thesis, observations first two combined modelling framework Expert-N simulate fluxes two study combines models physiological plant-soil system. Water simulated considering rainfall interception, evaporation, flow, drainage, root uptake. Observations plots provided reliable data parameterisation calibration uptake realistically described. applied stand-level thus able stands. calculated sensitive composition forest. results this demonstrate partitioning, extraction, ions differed gradient certain Both selection effects complementarity played role. These provide information management forests Central Europe meet public demands well ensure vitality under changing climatic