After his youth in the Erzgebirge mountains, Klaus Bellmann studied agronomy at the Humboldt University in Berlin, with particular interests in plant production and the systematic evaluation of experimental studies. His Ph.D. thesis was defended in 1960, at the Faculty of Agriculture, Rostock University, focusing on the water balance and growth of genetically modified clover, based on his own experimental work. From there, Bellmann moved to the developing field of quantitative genetics, resulting in ground-breaking theoretical and modelling studies of maize, published in 1969 as his habilitation thesis. He soon joined the newly founded Zentralinstitut für Kybernetik und Informationsprozesse (ZKI) in Berlin, where he became head of the Department of Systems Analysis and Simulation. The goal was to use the most recent developments in numerical computing to develop mechanistic models of dynamic processes in ecological systems – particularly on the molecular and genetic level. In 1983 Bellmann published an edited volume on “Molecular Genetic Information Systems”.
Besides systems analysis and modelling, Bellmann retained his interest in statistics and biometrics, i.a., in his role as editor-in-chief of the Biometrical Journal (1966-1990) but also as lecturer in biomathematics and quantitative genetics in Berlin (Humboldt University), Halle and Greifswald.
A key result of work initiated by Bellmann at the ZKI was an advanced modelling and simulation environment for ecological purposes (SONCHES), derivatives of which are still developed and used in several institutes including PIK. The goal was to make large amounts of simulations straightforward, and to ensure appropriate analysis of uncertainties in the results. Based on his holistic system-analytical view he increasingly focused his research on the design of decision support systems also beyond agriculture, e.g. for forests affected by atmospheric pollution (System PEMU).
During his later career, Bellmann developed particular skills as a coordinator and moderator of interdisciplinary research groups and networks. Important partners for this work were the Institute for Soil Fertility Research in Müncheberg, the Institute for Forest Sciences (Institut für Forstwissenschaften) in Eberswalde and the Institute for Plant Breeding in Quedlinburg. Thanks to this experience, Bellmann could later play an important role during the establishment of the Zentrum für Agrarlandschaftsforschung (ZALF) in Müncheberg.
Immediately after the opening of the Berlin wall in 1989, Bellmann made extensive use of the new opportunities for international scientific exchange. He joined the newly established Institute for Ecosystem Research, leading its Department of Systems Ecology. In 1992, this group became one of the foundations of the Potsdam Institute for Climate Impact Research and the PIK Department of Global Change and Natural Systems, which Bellmann co-led (with Wolfgang Cramer) until his retirement in 1994. After retirement, Bellmann continued to work as an advisor for major research projects, at PIK but also at the Technical University in Cottbus (BTU).
PIK owes Klaus Bellmann a substantial part of its theoretical foundation, which continues to live and grow through the work of several senior scientists who were trained by him – or who extensively collaborated with him during part of their career. Bellmann taught us all how best to utilize sparse point-based observations for drawing conclusions applicable to large regions, and despite his critical mind, he had learned to sometimes be rather “brave” in these efforts. His true motto, however, was one of modesty (quoting Friedrich von Schiller):
And if you cannot be a Whole yourself,
become a serving member of a Whole.
In this sense, Klaus Bellmann taught us all an important lesson: our scientific effort towards dealing with anthropogenic global change is crucially important, but it is wise to start from a perspective of humbleness as human beings.
Klaus Bellmann is mourned by a large family, and we particularly extend our condolences to his wife, his children and grandchildren. All of Bellmann's colleagues remember him fondly as a man with a strong belief in human values – each of us remains grateful for the path we could walk with him together.
