The effect of treeshelter height on the early growth of sessile oak (Quercus petraea (Matt.) Liebl.)

Sessile oak 1+1 transplants were grown for 4 years in a weed-freeenvironment at 1 x 1 m spacing on a fertile sheltered site.Four experiment treatments were imposed: control with no treeshelterand treeshelters of heights 0.6 m, 1.2 m and 1.8 m. Treatmentshad no significant effect on tree survival. Taller sheltersproduced taller, lower diameter trees of increasingly low dryroot weight. The root:shoot ratio was 0.675 in control treesbut declined to 0.291 in 1.8-m shelters. Trees from 0.6-rn and1.2-m shelters (mean heights 152 m and 206 m respectively) supportedthemselves unaided after removal of the stake and treeshelter.The trees from 1.8-m shelters of mean height 234 cm at age fourcollapsed completely when support was removed.     

Treatment of Severely Checked Sitka Spruce Trees with Injected Nutrients

Matched pairs of nutrient deficient Sitka spruce (Picea sitchensis(Bong.) Carr.) of mean height 3.0 m on a drained acid infertiledeep peat were injected in early summer by infusion with anaqueous solution of 40, 20, 66 and 0.2 g l^–1 N, P, K,Mg respectively, pH 7.2 and high conductivity. Three growingseasons later there were no responses in injected trees in treeheight increment, foliage nutrient levels of N, P, K, Ca, needlecolour, needle weight or crown density. Foliage Mg levels wereraised significantly. The injection procedure caused severetissue damage around the Infusion point and 84 per cent of thetrees had stain in stem cross sections 50 cm above the treatmentlocation.     

The Effect of Intercropping Populus 'RAP' with Beans

Dwarf French beans and broad beans were grown at 0.25 m x 0.25m for 2 years with a without cuttings of Populus ‘RAP’at spacings of 2.0 m x 0.5 m and 3.0 m x 0.5 m. The presenceof beans lead to a greater height and diameter growth and greatertotal dry matter production per hectare of the Populus at bothspacings after 2 years. Bean yield was reduced at the end ofthe second year by the presence of Populus; there was no effectat the end of the first year.     

Growth of Young Sitka Spruce (Picea sitchensis (Bong.) Carr.) and the Effect of Simulated Browsing, Staking and Treeshelters

Sitka spruce (Picea sitchensis (Bong.) Carr.) 1 + 1 transplantswere grown at 1 x 1 m for 3 years with 100 per cent chemicalweed control on a very fertile site. Treatments were control,firm staking, staked with 15 cm diameter netting with simulatedbrowsing, staked with simulated browsing to 15 cm diameter crown,1.2 m treeshelter, 1.2 treeshelter with holes and no browsing.No leaders were browsed. Trees were assessed for annual heightgrowth, stem diameter at 0.5 m and 1.0 m, total above and belowground biomass, root:shoot ratio, root plate diameter, rootdepth and root volume. No 3-year heights were significantlydifferent but third-year increments were; the greatest finalheight was in the control at 200.7 cm. All other tree parametershad significant treatment differences demonstrating the needto select carefully the criteria of success in experiments.Treatments which restricted the horizontal development of thecanopy either physically or by simulated browsing seriouslyreduced stem diameter and root development. The controls hada root:shoot ratio of 0.418; treeshelter treatments had thesmallest root:shoot ratio of 0.238; staked trees were 0.379while staked browsed trees had the highest value at 0.447. Acceptanceof browsing or use of shelters or guards to protect trees frombrowsing may seriously reduce growth.     

Wind Measurements in a Pine Forest During a Destructive Gale

Anemometer readings were recorded during a gale which blew downsome of the trees in an even-aged 16 m stand of Pinus sylvestrison sandy soil at Thetford forest. Gusts at the top of the canopyattained 17•5 m/sec. Wind profiles agreed well with thetheoretical logarithmic profile above the canopy and the exponentialprofile below. During the gale the zero plane displacement androughness length values were similar to those at lower windspeeds. It is therefore possible to estimate wind profiles andthe forces to which a tree in the crop is subjected from measurementsof wind speed at a single point within or above the forest.The wind speeds which blew trees down were much lower than thosepredicted as necessary from ‘tree pulling’ studiesin the same forest. This discrepancy suggests that any considerationof windthrow must take into account the effects of tree vibrationon the deterioration in the strength of the root-soil complex.     

Toxicity of Five Granular Herbicides to Sitka Spruce and Lodgepole Pine

Experimental plots in young plantations of Sitka spruce andlodgepole pine were over-dosed with five granular herbicidesto ascertain the margin of crop safety involved in the use ofpropyzamide, chlorthiamid, dichlobenil, dichlobenil/dalaponmix and atrazine. It is concluded that if the five herbicidesare applied according to the standard rates and dates used inthe experiments, tree damage will be kept to an acceptable minimum.Better shoot growth resulted from herbicide treatment than fromhand weeding particularly where atrazine was used.