Data on and methodology for measurements of microclimate and matter dynamics in transition zones between forest and adjacent arable land

Ecosystems are often defined by visually perceived boundaries, while for many properties sharp boundaries are difficult to draw. Boundaries between terrestrial ecosystems have often been described with much emphasis on edge effects, which is the impact of the presence of one ecosystem on an adjacent ecosystem. At the boundary of forested and agricultural ecosystems, measurements of environmental variables exist almost only for the forested area, describing the extent of a transition zone and the rates of exchange of matter, energy and information from the zero line (edge) into the forest. The opposite direction has been nearly neglected so far. Microclimatic variables differ in magnitude in the transition zone between arable land and forest. They affect habitat properties, biotic activity, carbon and nitrogen stocks, as well as turn-over rates under the different input of organic matter. ‡,§ ‡,§ ‡


Context
In ecosystem ecology, the focus is most often on single ecotopes like forest ecosystems or agro-ecosystems.The edge effects are rarely accounted for.However, ecosystems are open and complex systems.They exchange matter, energy and information at their boundaries.The transition zones usually have steep environmental gradients and often have proved to be hotspots for biodiversity (Ries et al. 2004).Especially for microclimate, carbon and nitrogen stocks, numerous have been found having siginificant effects on biogeochemical and biphysical processes (Schmidt et al. 2017).
Following the logic of a single ecosystem, most experiments and samples were conducted in only one ecosystem.We conducted measurements in transects across boundaries of forest to arable land to explicitly overcome these constraints as well as boundaries of scientific fields.These measurements were conducted for more than one year comprising two growing seasons and one season of leaf fall.The purpose of these measurements was to gain insight into magnitude and extent of environmental gradients in the transition zone as a base for subsequent modelling studies.This data paper is meant to a) explain the measurement design and methodology in detail, b) make all measured data openly accessible for re-use and c) make the editing of raw data transparent.

Measurement site
The measurement sites are located in north-east Germany in the federal state of Brandenburg.Two sites were selected according to 1) the homogeneity of tree species composition within the forest stands, 2) the size of the ecosystem patches (fragment), 3) the cardinal direction of their zero line (edge), 4) the age and management of the forest, 5) the homogeneity of the surrounding landscape, 6) the management of the agricultural land, 7) the distance to Müncheberg, Germany and 8) the willingness of farmers, forest managers and land owners to cooperate.According to this framework, the following specific criteria were set and evaluated using geographic information systems (GIS) to prepare the selection: 1.
continental, temperate forest with coniferous trees (comprise ca.75% in the region) resulting in pine (Pinus sylvestris L.) and larch (Larix decidua) (it was not possible to find sites with the same main species composition that fit all other criteria at the same time), 2.
>10 ha total area of the forest patch and more than 500 m of forested area perpendicular to the zero line (edge) of the forest, 3.
one east-facing and one west-facing edge to avoid too strong effects of the cardinal directions north and south, 4.
managed, planted forest with an age of trees between 40 and 60 years, 5.
a minimum of additional wind-breaking landscape elements and flat terrain within 500 m of the measurement sites, 6.
agricultural land cropped for more than 10 years prior to the study, 7.
less than 50 km distance to Müncheberg to remain operable, 8.
approval to conduct all measurements from June 2016 to September 2017.
We identified an east-facing (the arable land is east of the forest) site in Ihlow, Germany (52°37'23.8"N,14°03'40.4"E)and a west-facing site in Elisenhof, Germany (52°29'37.1"N,14°11'03.4"E).Both sites are located in the cold temperate area with summers colder than 22°C on average and 4 months where the temperature is above 10°C (Dfb; Peel et al. 2007).See Fig. 3 for an examplary picture of a forest edge.Besides the main tree species composition, the edge was characterised by grassland as well as scattered shrubs (bird cherry (Prunus padus) at the east facing site) and deciduous trees (birch (Betula pendula) at the west-facing site).The zero line is the abrupt change in ploughed arable land to the unmanaged forest soil.

Microclimate
The microclimate was measured in 105 m long transects with five weather stations -one at the zero line (edge), two in the arable land (see Fig. 4 for the setting) and two in the forest (Fig. 1, Fig. 2).The measured variables were air and soil temperature as well as moisture, wind speed and direction, air pressure, precipitation and solar radiation.The microclimatic data are given separately for the west-facing site (Suppl.material 1) and the east-facing site (Suppl.material 2).
The measurements started on 15 June 2016 and ended on 17 July 2017.The distances were chosen based on a previous literature analysis (Schmidt et al. 2017).Cross-sectional scheme of the measurement design for both sites.The height for litterfall and biomass sampling is not scaled.Setting of weather stations in the arable land at the east-facing site.View towards south.Picture taken in autumn.
Data on and methodology for measurements of microclimate and matter dynamics ...
The following sensors were used (see Table 1.
Information on the device name, accuracy, resolution and range of the sensors of the weather stations as well as the measurement height or depth and direction.

Biomass of crops
In 2016, at four plots of 1 m each and at 0 m, 7.5 m, 15 m, 30 m distance from the zero line, the aboveground biomass was harvested manually (Figs 1, 2, 5) approximately one week before the harvest by the farmers (12 July).In 2016, at the east-facing site, peas were grown and at west-facing site oil-seed rape.In 2017, another biomass harvest was conducted with the same design.On 3 July, approximately 10 days before the official date, winter barley was harvested at the east-facing site and winter wheat at the west-facing site.
After chopping the plants, they were oven-dried for 48 h at 65°C and the dry mass was weighed thereafter (Suppl.material 3).Data on and methodology for measurements of microclimate and matter dynamics ...

Litterfall
Litterfall was measured with buckets (see Fig.

Soil sampling and analyses
The soil was sampled at two depths -20±3 cm and 40±3 cm -along the transects (Figs 1, 2).The samples were sieved at 2 mm, air dried and analysed (n=3) for total soil carbon content and total soil nitrogen content (see Suppl.material 6).All samples were carbonatefree as tested in the field using hypochloric acid (see also pH in Suppl.material 6).Soil types were determined in the field according to WRB (FAO 2014; Table 2) using a soil drill (1 m length).

Data editing
The microclimatic data from all ten weather stations were merged (see Suppl.material 7 for the R script).Moreover, the original header contained non-unicode symbols which had to be transformed.Data had to be rearranged as two weather stations were mixed up after ploughing and had to be replaced to their original positions.Further, data was cut according to the official starting and end points of the experiment and pauses due to 1 Table 2.
Soil classification according to WRB (FAO 2014) with soil textural classes for two different depth (20 ±3 cm and 40±3 cm) in a transect from forest (negative distances) to arable land (positive distances) and its zero line (edge; 0) at an east-facing site (E) and a west-facing site (W) in northeast Germany.This Cambisol was deeply eroded which cut off the cambic horizon and mixed it due to ploughing.
We deleted two outliers for precipitation (error in measurements shortly after installation and the measurement date was wrong) and one for relative humidity (relative humidity of 4.8 not possible) from the whole data set.
The data logger (EM-50G) used the time zone of the plugged device.Due to that and the switch of standard time during the year, we had to unify the time to Central European Time (CET) manually.; SoilTempXX is the soil temperature given in °C; RelHumXX is the relative humidity given as dimensionless number; AirTempXX is the air temperature in °C; AirPressXX is the barometric air pressure given in kPa; SolarRadXX is the solar radiation given in W m ; WindAvgXX is the average wind speed given in m s ; WindMaxXX is the maximum wind speed given in m s ; WindDirXX is the direction of the wind given in °; PrecXX is the precipitation given in mm; DistXX is the distance to the zero line (edge), positive values are in the arable land, negative values are in the forest, zero is the edge.For more details see "Microclimate".The data was edited according to "Data converting".Timezone: Central European Time (CET).

Suppl. material 3: Data on drymass of crops
Authors: Martin Schmidt, Gunnar Lischeid, Claas Nendel Data type: .CSV -Comma-separated values Brief description: Explanation of header and data: Dist is the distance from the zero line (edge) into the arable land in m, 0 is the zero line; Crop refers to the species (see "Biomass of crops" for more details); DryMass is given in g per m .

Suppl. material 4: Data on tree height and diameter
Authors: Martin Schmidt, Gunnar Lischeid, Claas Nendel Data type: .CSV -Comma-separated values Brief description: Explanation of header and data: Site is either west-facing or east-facing site (see "Measurement site"); Dist is the distance from the zero line (edge) to the forest interior in m, 0 is the zero line; Tree number refers to a unique tree (number) in the plot (letter); Perimeter is measured at 1.30 m from the ground and is given in cm; BHD is derived from the perimeter and given in cm; Height is the measured height of the trees in m.Data on and methodology for measurements of microclimate and matter dynamics ...

Figure 2 .
Figure 2.Topview on to the measurement design for east-facing site.The west-facing site is mirrored.The width is only scaled to the forest inventory plots.The symbols for weather stations, litterfall and biomass sampling are offset.

Figure 3 .
Figure 3. Examplary picture of the forest edge at the west-facing site.View towards north.

2Figure 5 .
Figure 5. Delayed flowering of rape in the transition zone to the forest at the west-facing site.View towards south.Picture taken in summer.

Figure 6 .
Figure 6.Setting of weather stations in the forest (zero line, -35 m and -70 m) with rain gauges.

Figure 7 .
Figure 7. Setting of litter fall traps at the zero line (edge).

Figure 8 .
Figure 8.Design for tree inventory with the dots as examplary trees, the arrows as walking direction during measurements and the circles as the range of counting the trees with 5 m range in A and 7 m range in B.

Site Distance to edge [m] Soil Soil type in 20 cm Soil type in 40 cm
SoilTempXX is the soil temperature given in °C; RelHumXX is the relative humidity given as dimensionless number; AirTempXX is the air temperature in °C; AirPressXX is the barometric air pressure given in kPa; SolarRadXX is the solar radiation given in W m ; WindAvgXX is the average wind speed given in m s ; WindMaxXX is the maximum wind speed given in m s ; WindDirXX is the direction of the wind given in °; PrecXX is the precipitation given in mm; DistXX is the distance to the zero line (edge), positive values are in the arable land, negative values are in the forest, zero is the edge.For more details see "Microclimate".The data was edited according to "Data converting".Timezone: Central European Time (CET).Measured values are indicated in the header by the variable (e.g."SoilMoist") followed by the distance to the zero line (e.g. 30, indicated by XX in the description below).Date.Time is given as YYYY-MM-DD HH:MM:SS; SoilMoistXX is the soil moisture given in cm cm cm ;