Kanzler, M.

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Universidade Técnica de Lisboa

Microclimate effects of short rotation tree-strips in Germany

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3rd European Agroforestry Conference  Montpellier, 23-25 May 2016 Tree-crop competition and facilitation (oral)  321  MICROCLIMATE EFFECTS OF SHORT ROTATION TREE-STRIPS IN GERMANY  Michael Kanzler1 1, Jaconette Mirck1  * Correspondence author: kanzlmic@b-tu.de  1 Department of Soil Protection and Recultivation Brandenburg University of Technology Konrad-Wachsmann-Allee 6, D-03046 Cottbus, Germany  Introduction Multifunctional land use systems, such as agroforestry, are able to deliver several ecological services to agriculture in addition to the concurrent production of woody biomass and arablecrops. For example, trees in agroforestry systems can provide shelter for wildlife and supply additional nutrients to adjacent arable fields through leaf litter inputs and fine root turnover. In addition, tree-strips have the ability to improve the groundwater quality underneath the tree-strip itself and possibly underneath adjacent fields. Unlike these commonly measured ecosystem services the microclimate conditions in temperate agroforestry systems are still a comparatively new study area (Kanzler  et al. 2014). This might be due to the complexity of the microclimate, which depends on various parameters such as the plant height, the planting density, and the orientation of the tree-strips. The objective of this study was to investigate the potential influence of tree-strips on microclimate using high resolution data loggers.  Materials and methods Investigations were carried out at an agroforestry research site situated in Germany about 150 km southeast of Berlin (Figure 1). The study area is characterized by an average annual precipitation of 560 mm and a mean annual temperature of 9.3 C (1951 2003, meteorological station Cottbus). The site is mainly level and part of a largely tree-less landscape on the former  crop production for several decades and was first used for agroforestry in 2010.   Figure 1: Location of the study area in Germany The tree-strips of the alley cropping system are oriented in a north south direction and are composed of black locust (Robinia pseudoacacia L.) and the poplar Populus maximowiczii x Populus nigra) in different 160 m long pure blocks. The crop alley widths have been adapted to multiples of the standard widths of  agricultural machinery (Table 1).3rd European Agroforestry Conference  Montpellier, 23-25 May 2016 Tree-crop competition and facilitation (oral)  322  Table 1: Characteristics of study site near the town Forst (in South East Germany).  The alleys were cultivated with sugar beet (Beta vulgaris var. altissima) during the measurement period. Prior to starting microclimate measurements the tree-strips had been harvested in winter 2014/15. They started to resprout at the end of April 2015, and by the end of the measurement period the poplar trees had achieved an average height of 2.8 m.   Shortly after the tree harvest in February 2015, 52 Hobo Pro V2 data loggers with built -in temperature and relative humidity sensors were installed 30 cm above the soil surface within alleys of 3 different widths and at different distances from the tree-rows (Figure 2). Air temperature and relative humidity were recorded on a ten minute basis. Additionally, several weather stations and anemometers (A100R, Vector Instruments) were installed to collect climate data like wind speed, global radiation and precipitation at different distances from the tree-strip. All climate data were recorded over a period of 5 months from May to September 2015.   Figure 2: Positions of the Hobo data loggers (H), anemometers (A) and weather stations (WS) on different crop alleys within the study area.    Feature research siteTotal area of alley cropping  field (ha) 40Overall tree-stripe area  (ha) 5Elevation (m) 70Slope FlatLandscape Intensively used agricultural landscapeSoil type (WBR classification) Gleyic FluvisolDominant soil texture (0-30 cm depth; Sandy loamUSDA classification)Establishment of alley 2010cropping (year)Tree species/clone Black locust, poplar MaxTree densitiy (poplars ha-1) 8,715Planting layout Double rowNumber of double rows per tree-strip 4Plant spacing (m)Within row 0.90Within double row 0.75Between double rows 1.80Width of hedgerows including 0.80 m 10.00buffer stripes along both edges (m)Rotation period (years) 5Width of crop alleys (m) 24, 48, 963rd European Agroforestry Conference  Montpellier, 23-25 May 2016 Tree-crop competition and facilitation (oral)  323 Results and discussion In May 2015 no obvious difference in air temperature among the plots was observed, but from the beginning of June the impact of the growing tree-strips on temperature became clearer (Figure 3a and b). Compared to the open field, the maximum air temperature from 1st of July to  tree-strips, presumably due to shadingthe 24 m wide crop alley, which is a potential effect of the reduced wind velocity (compare Fig. 3c). In addition, the lowest air temperature was detected in the 24 m wide crop alley, which was -lower than the tree-strip. Taking into account the whole measurement period, the minimum relative humidity in the poplar tree-strip was 4% higher than on the open field, while the difference between the open field and the centre of the 24m crop alley was 1% (Figure 3c). Compared to the open field the wind velocity in the center of the 24 m wide crop alley has been reduced by up to 17 % (Figure 3d.)     a.)       b.)        c.) 3rd European Agroforestry Conference  Montpellier, 23-25 May 2016 Tree-crop competition and facilitation (oral)  324  Figure 3: Daily a.) maximum, b.) minimum of air temperature, c.) minimum relative humidity and d.) average wind velocity for the centre of the 24 m wide crop alley, the poplar tree-strip and the adjacent open field (n=4 for 3a,b and c). In addition, the wind speed has been reduced by almost 67 % within the poplar tree-strips. The highest reduction effect of more than 32 % has been detected on the leeward side, at a distance of 3 m from the tree-strips. Despite the fact that the tree-strips had been harvested in February initial results indicated an early effect on microclimate conditions within the alley cropping system. References: , C.; Kanzler, M. & Freese, D. (2014). Impact of black locust hedgerows on wind velocity and wind erosion in Eastern Germany. Book of abstracts of the 2nd European Agroforestry Conference: integrating science & policy to promote agroforestry practice held from 04. 06. June 2014 in Cottbus, Germany 267 268. Kanzler , C.; Mirck, J.& Freeseeines Agroforstsystems. Multifunktionale Agrarlandschaften    d.) 

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Microclimate effects of short rotation tree-strips in Germany

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