Structural root growth of young Veronese poplars on erodible slopes in the southern North Island,New Zealand |
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Authors: | I R McIvor G B Douglas S E Hurst Z Hussain A G Foote |
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Institution: | (1) HortResearch, Private Bag 11 030, Palmerston North, New Zealand;(2) AgResearch, Private Bag 11 008, Palmerston North, New Zealand;(3) Massey University, Private Bag 11 222, Palmerston North, New Zealand |
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Abstract: | In New Zealand poplars are commonly planted on moist, unstable pastoral hill country to prevent or reduce soil erosion, thereby
maintaining hillslope integrity and pasture production. Mechanical reinforcement by poplar root systems aids slope stabilisation.
Root mass and distribution were determined for three Populus deltoides × nigra ‘Veronese’ trees aged 5, 7 and 9.5 year planted as 3 m poles at 8 m × 8 m spacing on a hillslope near Palmerston North in
the southern North Island. Most of the structural roots (≥2 mm diameter) were distributed in the top 40 cm of soil. Vertical
roots penetrated to about 1.0 m, being the depth of the soil above a fragipan. Total structural root dry masses (excluding
root crown) were 0.57, 7.8 and 17.90 kg for the trees aged 5, 7 and 9.5 year, respectively. Total structural root length was
79.4 m for the 5 year tree and 663.5 m for the 9.5 year tree. Surrounding trees were estimated to increase root mass density
to 3 times and root length density to 4–5 times the contribution of the single tree at 9.5 year. The study indicated that
root development of wide-spaced poplar trees on hillslopes was minimal in the first 5 years but then increased rapidly. These
results suggest that poplar trees established from poles may take at least 5 years to develop a structural root network that
will effectively bind soil. |
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Keywords: | Hill country Silvopastoral Soil conservation Soil stability Root development |
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