This dataset contains information from a tree census on the plots of the interdisciplinary research training group 'RTG2300: Enrichment of European beech forests with conifers'. The tree cesus was carried out during winter 2017/2018 using a Field-Map system (software Version 5x; IFER - Monitoring and Mapping Solutions, Ltd.; Prague; Czech Republic). All living and dead trees with a diameter greater or equal than 7.0 cm were recorded in the 0.25 ha plots (https://doi.pangaea.de/10.1594/PANGAEA.923125) and in a ten meter buffer zone surrounding the plot border. Tree coordinates relative to the plot center were recorded with a laser range finder with an integrated electronic compass (TruPulse Laser 360 R, Laser Technology Inc, Centennial, USA). Tree diameters were measured with a diameter tape preferentially at 1.3 m height. If a diameter measurement at 1.3 m was not possible, the alternative height of the diameter measurement was recorded. Tree species, tree vitality (dead or alive) and tree condition ('normal', 'snag', 'hung_up', 'sloping', 'thrown', 'stump') of each tree and heights of snags were recorded.
This dataset provides information about the fine root biomass inventory conducted in April 2018 in plots of the interdisciplinary research training group 'RTG2300: Enrichment of European beech forests with conifers. The aim of this study was to examine how enrichment of beech forests with conifer species impacts fine root biomass and other root traits across variable site conditions. The study was carried out in Northern Germany (federal state of Lower Saxony, Germany) and comprised four stand clusters so-called 'quintets'. Each quintet contained five neighboring forest stands: three monospecific stands of European beech (Fagus sylvatica; Be), Norway spruce (Picea abies; Sp), or Douglas- fir (Pseudotsuga menziesii, Dg), and two mixed stands, one composed of European beech and Norway spruce, and one composed of European beech and Douglas-fir. In each of twenty stands, plots of 0.25 ha in size were established. The quintets were clustered according to their geographical location into two regions, "south" and "north", with two quintets in each region. The southern plots are located in higher altitudes with lower mean annual temperatures and a higher annual precipitation. Growing conditions on the northern plots are less favorable than on the southern sites, in particular with respect to precipitation. For fine root sampling, we used a systematic regular sampling grid design with a 10x10m grid established across each study plot. A total of ten grid cells were systematically selected from total 25 grid cells. At each selected cell, one root core was taken. Sampling was carried out from the end of March to mid-April 2018. We used a soil corer of 8 cm diameter to extract soil from the organic layer and mineral soil (0-60 cm). The organic layer which varied by depth was sampled as a whole, while the mineral soil was divided into twelve subsamples, each of 5 cm depth. In total, 200 soil cores with 2147 samples were collected and stored in plastic bags at 4 °C until further processing in the laboratory (maximum storage time four months). Living fine roots and dead roots (necromass) were expressed as fine root dry mass per soil volume (g m-3) and as dry matter per square meter of ground area (g m-2) per soil depth. Specific fine root surface area (SRA, cm2 g-1), and specific fine root length (SRL, m g-1) were calculated from fine root area and fine root length divided by dry fine root biomass. Root area index (RAI, root surface area per ground area, m2 m-2) was estimated by multiplying specific fine root surface area by the fine root biomass in a horizon
Climate change will substantially alter native forest ecosystem dynamics. Increased storm frequencies and severities and longer summer droughts are major threats for the provision of ecosystem goods and services (EG&S) from forests. To adapt forests stands to climate change, two silvicultural measures have been proposed: (i) the promotion of mixed stands and (ii) the integration of exotic tree species that are expected to be adapted to future climatic conditions (in particular from areas with a drier and warmer climate). Non-native tree species as well as mixed stands may be better suited for the expected future climate due to a higher resistance and resilience against disturbances. The combination of mixed stands that consist of native and non-native tree species, may present a suitable compromise between the desired effects on growth and vitality of forests and potential undesired effects on the composition of native species associations and ecosystem processes such as nutrient cycling. Despite high potential benefits of mixed stands, planted forests around the globe are mainly monocultures. To foster the provision of EG&S, more knowledge about the mechanistic functioning of mixtures as well as trade-offs between the provision of different EG&S from mixed and pure stands is necessary. Interdisciplinary research projects are necessary that address effects of mixtures consisting of native and non-native tree species on the composition of various taxonomic groups, ecosystem processes and their consequences for the provision of EG&S. The interdisciplinary research training group 'RTG2300: Enrichment of European beech forests with conifers' addresses this knowledge gap by studying the mechanistic and supplying ecosystem functioning of forest stands of native European beech (Fagus sylvatica L.), Norway spruce (Picea abies L. KARST) and non-native Douglas-fir (Pseudotsuga menziesii MIRB. FRANCO) in Northern Germany. The stand types in this project include pure stands of all three species and mixed beech/spruce and beech/Douglas-fir stands. Each stand type is represented at eight locations resulting in a total of forty study plots. Twenty out of the forty research plots of 0.25 ha size are located in the southern part of the study area in the Solling and Harz mountain ranges, whereas the other twenty plots were selected in the northern part of the study area in the North German plain. The southern plots are located at higher altitudes with lower mean annual temperatures and a higher annual precipitation than those in the north. The stands on the northern plots have less favorable growing conditions than those on the southern plots, in particular due to less precipitation. Here, we provide basic datasets that were collected by the RTG2300. This includes data about location, topography and climate of the research plots, data of the tree inventories and data about the density and spatial structure of the stands that were derived from the tree inventory data.
Vegetation cover was visually estimated on the plots of the research project RTG2300 between Mid May and Early June 2020 using the Braun-Blanquet method (Braun-Blanquet 1951). Subplots of 100m² size were established in the southeastern corner of the plots. Cover of all plant species was estimated in discrete steps of 10% (10% to 100% cover) 1 % (1% to 10% cover). Cover estimates between 0.5% and 0.99% were recorded as '+' and cover estimates below 0.5% were recorded with an 'r'. Plant cover in four different layers (tree, shrub, herb and moss) was estimated. Within each layer, cover of all individual plant species and cover of all plants combined ('layer_total') was estimated. Due to overlap of some species, cover of all individual species does not sum up to the layer total. For the moss layer only the layer total was estimated and no identification of individual moss species was done.
Light is an exceptionally important but often limited resource. Light availability determines seedling survival, establishment, and growth. Regardless of species identity, trees growing under high light availability produce more biomass and are generally larger than trees receiving less light. How stressed trees become under the conditions of limited light availability depends on species-specific factors like shade tolerance and plasticity as well as the competitive situation. Additionally, the taller individuals have the advantage to obtain more light since competition for the resource is asymmetric. In competitive environments, the niche complementarity of the coexisting species can reduce the competitive pressure and facilitate higher biomass production (i.e., positive mixing effect). We established a controlled pot experiment to study the effect of light availability and competition type on growth and its allocation, biomass production and allocation, and leaf morphology of European beech (Fagus sylvatica L.), Norway spruce (Picea abies L. Karst), and Douglas fir (Pseudotsuga menziesii Mirb. Franco) seedlings. The study site was located at the Experimental Botanical Garden of the University of Göttingen (51.55684392372871, 9.953489533796636). We planted four seedlings per pot, each pot being either monospecific or mixed (two seedlings per species) and exposed to one of three different light availability levels (10%, 20%, and 50%). We planted in a total of 576 pots – 6 species combinations (monocultures + mixtures) x 3 light treatment levels x 32 replicates. For planting, we used 1-year-old European beech and 2-year-old Norway spruce and Douglas fir seedlings that were not undercut or transplanted. The experiment lasted from April 2018 – November 2019. All seedlings received the same water treatment through an automatic dripping irrigation system. Nutrients were provided using a controlled release fertilizer (Osmocote Exact Hi.End with 12-14 month longevity (ICL SF)).
This dataset provides information about the study design, topography, geographic location and climatic conditions of the research plots of the interdisciplinary research training group 'RTG2300: Enrichment of European beech forests with conifers'. In each of forty forest stands, plots of 0.25 ha in size (called regular measurement plots, RMPs) were established in fall 2017 across the federal state of Lower Saxony, northwest Germany. The plots are grouped in eight so-called 'quintets'. Each quintet comprises five plots representing different forest stand types: three pure plots (European beech (Fagus sylvatica), Douglas-fir (Pseudotsuga menziesii), Norway spruce (Picea abies)) and two beech-conifer mixtures (beech-Douglas-fir and beech-Norway spruce). Four of the eight quintets are located in the southern part of the study area in the Solling and Harz mountain ranges. The other four quintets are located in the northern part of the study area in the North German plain. The southern plots are located in higher altitudes with lower mean annual temperatures and a higher annual precipitation. Growing conditions on the northern plots are less favorable than on the southern sites, in particular with respect to precipitation. On a subset of twenty out of the forty plots, intensive surveys such as root growth measurements, nitrogen retention analyses, or experiments on regeneration dynamics are carried out, besides the regular measurements on all plots. These intensive measurement plots (IMPs) comprise two southern and two northern quintets. Permanent, highly intensive measurements are conducted on special measurement plots (SMPs) that are a subset of 10 out of the 20 IMPs.
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