The Most Immediate and Easily Observed Impacts of Climate Change

The Buda Arboretum is one of Hungary\u27s most outstanding collection gardens, located on the southern slope of Gellért Hill, on an area of 7.5 hectares. Although the history of the arboretum and the institution dates back nearly 150 years, the composition of the plants has been constantly evolving and changing, adapting to the increasingly extreme climate change. The climatic condition and maintenance of the garden mimic urban conditions, making it a good test site for studies in addition to its collection and educational role. Plants are very sensitive to changes, whether phenological, physiological, or morphological. In our research, we have studied the different phenological phases of all taxa, their development, and adaptation to the living conditions of the arboretum, which is illustrated in this paper by the example of the genus maple. The maple is one of the most common genus in urban areas, several species are native, and several Hungarian and foreign cultivars have been tested in the recent past, in stressed urban conditions, selection work in nurseries has resulted in almost all cases in the use of horticultural cultivars instead of basic species. According to our analyses, the Buda Arboretum has a total of 33 maple taxa, 63 planted specimens, most of which showed severe leaf drying and slight dehydration during the summer drought months. Among the native taxa, with the exception of field maple (Acer campestre), most maples, such as the Norway maple (Acer platanoides) and the sycamore maple (Acer pseudoplatanus) are less tolerant of polluted and dry environments. Their phenological and physiological responses to environmental changes (sprouting, dehydration, defoliation, etc.) can be used as a predictor of their urban climate tolerance. The selection of suitable taxa for urban tolerance is based on the longest possible healthy canopy. This is why the selection of suitable species for future replanting and new tree plantations is an increasingly complex task. According to our phenological and climatological studies over the last years, the most acclimatized maple taxa were the Montpellier maple (Acer monspessulanum), the Amur maple (Acer tataricum subsp. ginnala), which can be proposed for planting in the 21st century or can be a starting point for future breeding processes, thus providing a variety of plant application (linear element such as greenway planting, alleés, hedge, or in groups or solitary specimens) in urban public spaces, with a wide range of forms and colors