Is light competition between trees and crops a limiting factor for agroforestry systems at high latitudes?

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Is light competition between trees and crops a limiting

factor for agroforestry systems at high latitudes?

Quentin Molto, Christian Dupraz

To cite this version:

Quentin Molto, Christian Dupraz. Is light competition between trees and crops a limiting factor for agroforestry systems at high latitudes?. 2. European Agroforestry Conference, Jun 2014, Cottbus, Germany. 278 p., 2014, Second european agroforestry conference. �hal-02738628�

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Wolferschwenda in Thuringia on the edge of a field, slightly sloping towards the Bennebach stream. The experiment compares three management options for the buffer strip: arable, grassland, and SRC (willow). Two main objectives of the project are (i) simulation of potential soil input by erosion on the study site under different crops and (ii) investigation of the retention capacity of SRC, grassland, and cropland. Intensive soil measurements carried out from 2012 until present show initial trends that SRC may be a more effective nutrient buffer than grassland. More detailed results are expected from irrigation experiments in spring 2014.

Is light competition between trees and crops a limiting factor for

agroforestry systems at high latitudes?

Molto Q1_{, Dupraz C}1

Corresponding author: [email protected]

1

INRA, UMR-System, 2, Place Viala, 34060 Montpellier Cedex, France

While agroforestry systems are more attractive in Southern Europe, some northern latitude farmers are reluctant to adopt such systems. They fear that tree-crop competition for light would be too high due to lower sun elevations. However, how latitude is influencing light competition between trees and crops is not intuitive. We used a simulation model to explore how factors dependent on latitude (day duration, sun elevation, nebulosity and total irradiation), impacted on light competition between crop and agroforestry trees.

Our virtual experiment design combined 3 factors: latitude (30; 40; 50; 60°N), tree line spacing (13m; 35m) and tree line orientation (North-South; East-West). We used the sAFe-light model that is included in the Hi-sAFe model (Talbot et al 2012) to simulate a deciduous tree species. Competition for light was assessed for the duration of the crop life and at 4 key days of the year (equinoxes and solstices). The comparison between different latitudes is made explained further by comparing agroforestry plots with trees of similar sizes but different ages. Tree to tree and tree to crop competition for light is documented.

A key result is that the relative light irradiance on the crop is not dependent on latitude. Trees do not shade more crops at higher latitudes. However, lower incoming irradiation at high latitudes may result in very low absolute levels of irradiation on the crop during some stages of the crop cycle. We therefore suggest rules for designing agroforestry systems that differ depending on the

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latitude. However, the shade tolerance and phenology of the local crops and trees still have to be taken into account.

The state of alley cropping systems for bioenergy

Jacobson M [email protected]

Pennsylvania State University, Dept. of Ecosystem Science and Management 309 Forest Resources Building University Park, PA 16802, USA

In any country, the main challenge is how do to make bioenergy economically competitive at a commercial scale. Complementary integrated cropping systems, such as agroforestry, are suggested as ways to provide multiple benefits, including energy feedstocks, simultaneously across the landscape. Can agroforestry systems provide feasible supplies of bioenergy feedstocks? How can energy crops be integrated in agroforestry systems? Understanding the types of agroforestry systems, and their design for energy crop production, is crucial to sustainable land use. Riparian buffers, windbreaks and alley cropping have been touted as possible systems for commercial bioenergy production. Will enough biomass be available continuously in these systems, and not compromise environmental benefits? This paper examines the literature and assesses the state of research and practice of intercropping for bioenergy. Few studies were found that explicitly intercrop energy crops. The case studies all show potential for intercropping energy crops in agroforestry systems, especially potential environmental benefits and farm diversification. Issues include scaling up production, economic tradeoffs, long term impacts, and alternative energy prices.

Ecologically sound sites for the establishment and cultivation of

short rotation coppice (SRC) and SRC-strips

Jennemann L1_{*, Hennemann-Kreikenbohm}2

Corresponding author: [email protected]

1

bosch & partner GmbH, Germany

2

NABU, Berlin, Germany

This research project develops possibilities for the ecologically compatible cultivation of short rotation coppice (SRC) in a manner which avoids conflicts but rather promotes synergies with conservation. The project draws up criteria for the selection of an ecologically compatible site for