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Work Package 2b “Nelder” plots

This trial is designed as a pilot to provide data on planting density and mixture composition of broadleaf crop species and shelter species to inform the direction of future research. The trial is designed for the medium- to long-term. Nelder plots (Nelder, 1962) have been used successfully for many years for the investigation of planting spacing effects. A Nelder design was first used in Ireland in 1966 when two trials were established using Scots pine and Sitka spruce (Gallagher, 1980). A modified Nelder design (see Goelz, 1995) will be used to simultaneously investigate the effects of density and species composition (see Figure 1).

WP2c will establish three quarter-circle Nelder fans incorporating broadleaf crop species and shelter species decided from information gained during WP2b.

Site selection is very important for Nelder fans. The site must be uniform to allow data analysis. A Nelder fan contains no blocking and therefore can not mitigate site variation effects.

One of two approaches could be taken with WP2b: Either one crop/shelter species combination can be investigated and replicated three times, thereby providing greater strength to any inferences made from the data analyses, or; three crop/shelter species combinations can be investigated but with no replication, thereby weakening the inferences made from the data analysis but facilitating the investigation of more combinations. The decision of which approach to take will be informed by WP2a and available budgetary and site constraints.

Figure 1.
A Nelder's (1962) design for studying the effects of stand density is superimposed with a gradient of species composition. Shading indicates species. This systematic design allows exploring the effects of density and species composition simultaneously (from Goelz 1995).

The Nelder trial was established in the 2010-11 planting season. Three fans were planted at Teagasc Kinsealy Research Centre, Dublin 17, with ash (Fraxinus excelsior) and sycamore (Acer pseudoplatanus). Each fan is similar to that illustrated by Figure 2. Spokes 1 and 13 are buffers. The first and last arcs are also buffers. The planting densities used range from 667 stems/ha to 25,267 stems/ha. This is equivalent square spacings of 3.87 m to 0.63 m respectively (see Table 2).

Table 2. Planting density and equivalent spacings being investigated by the Nelder trial.
Spoke positionDistance from centre on spoke (m)Plant area (m2)Density per haEquivalent spacing (m)

0

5.00

 

 

 

1

5.75

0.40

25,267

0.63

2

6.61

0.52

19,106

0.72

3

7.60

0.69

14,447

0.83

4

8.75

0.92

10,924

0.96

5

10.06

1.21

8,260

1.10

6

11.57

1.60

6,246

1.27

7

13.30

2.12

4,723

1.46

8

15.30

2.80

3,571

1.67

9

17.59

3.70

2,700

1.92

10

20.23

4.90

2,042

2.21

11

23.26

6.48

1,544

2.55

12

26.75

8.57

1,167

2.93

13

30.76

11.33

883

3.37

14

35.38

14.98

667

3.87

15

40.69

 

 

 

Figure 2. Nelder fan layout planted during 2010-11 planting season

Figure 3. Nelder fan 1 in May 2012. The sycamore can clearly be seen whilst the ash are less prominent.