Questions
What was the main trigger of treeline ecotone advance – rising temperature or agricultural land abandonment? Were the triggering factors of tree expansion homogeneous or did they differ between upper and lower parts of the treeline ecotone?
Location
Sudetes Mts., Central Europe (50° N, 15‐17° E).
Methods
Data were gathered from the treeline ecotone formed by Picea abies at elevations ranging from 1250 to 1490 m. The study area experienced a 1 °C temperature increase over the last 100 yr and termination of cattle grazing and grass mowing in the first half of the 20th century. At 38 plots situated at lower (‘timberline’) and middle or upper (‘treeline’ and ‘outpost treeline’) parts of the treeline ecotone, the age structure of all seed origin P. abies was determined. Changes in tree cover and number of trees over the last 60–70 yr were assessed from aerial imagery. The history of agricultural land use for each plot was compiled. Finally, changes in tree establishment were modelled using climatic variables and land‐use intensity.
Results
We found that tree establishment at treeline had occurred with a 30–40‐yr lag after the main establishment peak at timberline. Whereas all treeline plots showed gradual increases in tree cover, timberline tree cover first increased, with some plots then undergoing thinning. Enhanced tree establishment was dependent mainly upon agricultural land abandonment. The effect of land‐use changes was more important in the lower than in the upper part of the treeline ecotone. Increasing summer temperatures had a negative influence on seedling establishment in the last few decades.
Conclusions
Treeline ecotone densification was attributable to agricultural land abandonment across the entire treeline ecotone with the most important effect at timberline. More recently, seedling establishment has been limited by the effects of drought and/or absence of suitable microsites. We documented that one or two establishment pulses over 120 yr, together with enhanced growth since the 1980s, were able to trigger treeline ecotone advance.
Abstract:The landscape of the Czech Republic currently faces droughts that are caused by several factors. One of the reasons for drought is landscape development and land cover changes. Changes in water and wetland areas and streams were studied by comparing old military maps and the present state. Water and wetland areas in fertile lowlands significantly decreased over time; the landscape was continuously dried out with the aim of increasing agricultural and woody production. While water and wetland areas occupied nearly one-third of the study area (Nové Dvory and Žehušice micro-regions in Central Bohemia) at the end of the 18 th century, the present share of these areas is only 3.5%. There was a decrease of approximately 10% in each period, and nearly all of these areas disappeared by the end of the 19 th century. Water and wetland areas were changed primarily to arable land. The length of streams decreased by the end of the 19 th century. Drainage and irrigation channels were built during the 20 th century, and although they are only periodic or episodic streams, these channels increased the total length of streams.Key words: streams, still waters, wetlands, land use changes, drought, central Europe Abstrakt: Krajina České republiky v současnosti čelí nebezpečí sucha, které je způsobeno mnoha faktory. Mezi ně patří změny krajiny a krajinného pokryvu. V článku jsou sledovány změny vodních a mokřadních ploch a délky vodních toků na podkladě starých vojenských mapování a současného stavu. Vodní a mokřadní plochy v nížinách zásadně ubyly a krajina byla vysušována s cílem zvýšit zemědělskou a lesnickou produkci. Zatímco na konci 18. století vodní a mokřadní plochy zaujímaly skoro třetinu sledovaného území Novodvorska a Žehušicka ve středních Čechách, v současnosti je to jen 3,5 %. V každé ze sledovaných period ubylo přibližně 10 % jejich rozlohy, významný úbytek těchto ploch v krajině tak nastal již v 19. století. Vodní a mokřadní plochy byly změněny převážně na ornou půdu. Délka vodních toků poklesla zejména v průběhu 19. století. Současná data ukazují nárůst jejich délky, který je ale způsoben budováním zavodňovacích a odvodňovacích kanálů, jejichž délka je také započítána do celkové délky vodních toků, byť nejsou celoročně protékány vodou.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.