The identification of visual symptoms can be a useful and cost-effective way of identifying nutrient deficiencies in forest trees. The visual symptoms associated with some nutrient deficiencies (e.g., top dieback, needle tip browning) are typically distinctive enough to enable reliable deficiency diagnosis. Unfortunately, not all deficiencies exhibit distinctive symptoms. For example, yellowing of lodgepole pine foliage (i.e., chlorosis) in the B.C. interior is most often associated with lack of nitrogen, but it can also be caused by deficiencies of sulphur, potassium, magnesium and iron. Yellowing can also be caused by non-nutritional factors such as wet and/or dry soil conditions, insects, disease, or herbicides. However, visual symptoms caused by nutritional limitations are generally rather evenly dispersed throughout the stand, while symptoms caused by non-nutritional factors are typically observed on individual trees or small groups of trees.
Nutrient deficiencies severe enough to impair tree growth are not always severe enough to cause observable symptoms. Therefore, the absence of visual deficiency symptoms does not preclude the existence of nutrient deficiencies, or the possibility of inducing a deficiency following N fertilization. Also, the existence of multiple nutrient deficiencies can be difficult to diagnose, since the symptoms of one deficiency (e.g., N) may mask (or alter) the symptoms of another (e.g., S).
Visual symptoms should be considered a useful initial indication of nutritional disorders. Nutrient deficiencies inferred by visual observation may be confirmed by means of foliar nutrient analysis.
The crowns of N deficient trees are characteristically pale green to yellowish green, with abnormally short needles. Yellowing is typically most evident in older foliage with chlorosis and shortening of needles becoming more pronounced with the severity of deficiency. Nitrogen deficient trees usually show the symptoms over the whole live crown and not on certain specific areas (e.g., K or Mg deficiency). The crowns of N deficient trees are characteristically thin.
Nitrogen deficiencies in lodgepole pine are widespread and serious throughout the B.C. interior, likely attributable to repeated fire disturbance and soils with thin surface organic layers.
Characteristic features of P deficiency are abnormally short needles and premature shedding of foliage. The overall effect is narrow, "thin" crowns. Usually there is no marked discoloration but the needles are a dull green colour. In young trees, needles on the ends of branches may be yellow-tipped and older foliage may be purplish in colour.
Visual symptoms of P deficiency in lodgepole pine are not well documented in the B.C. interior.
The most characteristic symptom of K deficiency is yellowing of foliage, especially needle tips. Both current year's foliage and older foliage may be affected. In extreme cases, the entire needle may be a bright canary yellow with reddish brown or dark brown tips. In younger trees, the whole crown may be affected but in older trees yellowing may be more pronounced in the lower crown. Magnesium deficiency causes a similar needle tip chlorosis, but the chlorosis generally tends to be a more golden colour and Mg deficiency symptoms may be more pronounced in older foliage.
Visual symptoms of K deficiency in lodgepole pine are not well documented in the B.C. interior. Some deficiency symptoms have been observed following repeated N fertilization.
The most characteristic symptom of Mg deficiency is yellowing of needle tips, often most noticeable in previous year's foliage. Symptoms are typically very regular on all needles of the same age on a branch. Potassium deficiency causes similar needle tip yellowing, but the chlorosis generally tends to be a paler, less golden colour and may be more noticeable on current year's foliage. In cases of acute Mg deficiency, growth may be stunted and the needle-tip chlorosis may also be present on current year's growth.
Visual symptoms of Mg deficiency in lodgepole pine are not well documented in the B.C. interior. Some deficiency symptoms have been observed following repeated N fertilization.
The most characteristic symptom of S deiciency is a general yellowing of foliage, most commonly associated with current year's foliage.
Sulphur deficiencies in lodgepole pine are well documented in the central and north-central interior of B.C. Sulphur deficiency symptoms are probably usually masked by moderate to severe nitrogen deficiencies. However, where N deficiencies have been alleviated by N fertilization, foliage yellowing is indicative of S deficiency.
Characteristic symptoms of Cu deficiency are the twisting of terminal and lateral shoots, often followed by defoliation and/or shoot, tip or bud dieback. Other symptoms include heavy branching, bushy growth, and rosetting of terminal shoots.
Visual symptoms of Cu deficiency in lodgepole pine are not well documented in the B.C. interior. There is some evidence that repeated N fertilization has induced Cu deficiencies on coarse-textured glacial outwash soils.
The most characteristic symptom of Zn deficiency is stunted growth, producing a rosette of buds around the terminal. Needles are short and chlorotic, sometimes with bronzed needle tips.
Visual symptoms of Zn deficiency in lodgepole pine are not well documented in the B.C. interior.
The most common and noticeable symptom of Fe deficiency is uniformly pale green or yellowish-green needles, especially on current year's foliage. As with other micronutrient deficiencies, retarded leader growth, shoot dieback and bud disorders may occur in severe cases.
Iron deficiency symptoms in lodgepole pine are not well documented in the B.C. interior. Deficiency symptoms may be masked by general foliage chlorosis caused by N deficiency. Iron deficiencies are most likely to occur on calcareous soils in the B.C. interior.
The most characteristic external symptoms of B deficiency are shoot, shoot tip, or bud dieback of the leader and/or lateral branches. The shoot of the main leader is generally affected first, followed by the shoots on the ends of the upper branches. Repeated disturbances result in multi-leadered, bushy crowns. New growth appears normal, and it is not until midsummer or later when leading shoots show clearly recognizable symptoms. Damage may be sudden, rapid and extensive.
In the B.C. interior, low foliar B levels and acute B deficiency symptoms are most commonly associated with morrainal soils derived from igneous rocks and subject to periods of soil moisture deficit during the growing season. Visual symptoms have also been observed on coarse-textured glacial outwash soils with low organic matter, where high rainfall may deplete soil-available B. On both these soil types, acute B deficiency symptoms have been induced by N fertilization.
Ballard, T.M. and R.E. Carter. 1986. Evaluating forest stand nutrient status. B.C. Min. Forests, Victoria. Land Manage. Report No. 20.
Binns, W.O., G.J. Mayhead, and J.M. MacKenzie. 1980. Nutrient deficiencies of conifers in British forests: an illustrated guide. Forestry Commission Leaflet 76.
Kolari K.K. 1983. Growth disturbances of forest trees. Proceedings of international workshop, Jyvaskyla, Finland, October 10-13, 1982. Comm. Inst. For. Fenn. 116.
Morrison, I.K. 1974. Mineral nutrition of conifers with special reference to nutrient status interpretation: a review of literature. Dept. of Environ., Can. For. Serv., Ottawa. Publication No. 1343.
Stone, E.L. 1968. Microelement nutrition of forest trees: a review. In: Forest fertilization – theory and practice. G.W. Bengtson (editor). Tennessee Valley Authority, Muscle Shoals, Alabama. pp. 132-175.
Stone, E.L. 1990. Boron deficiency and excess in forest trees: a review. For. Ecol. Manage. 37:49-75.
Stone, E.L. and G.M. Will. 1965. Boron deficiency in Pinus radiata and Pinus pinaster. For. Sci. 11:425-433.
Turvey, N.D. and B.R. Grant. 1990. Copper deficiency in coniferous trees. For. Ecol. Manage. 37:95-122.
Walker, R.B. and S.P. Gessel. 1991. Mineral deficiencies of coastal northwest conifers. University of Washington, Institute of Forest Resources, Seattle. Contrib. No. 70.
Will, G. 1985. Nutrient deficiencies and fertiliser use in New Zealand exotic forests. Forest Research Institute, Rotorua, New Zealand. FRI Bulletin No. 97.