Young needles are especially discolored, although their bases often remain green, and the transition between colors is gradual (INGESTAD 1959 MAYER-KRAPOLL 1964). When the deficiency is severe, the needle tips turn reddish-brown, brown, or purplish-brown, and eventually senesce. In coniferous trees, potassium deficiency results in an initial yellowish-green and later yellow discoloration of needle tips (BAULE and FRICKER 1973). Symptoms of phosphorus deficiency are observed when concentrations on a needle dry mass basis are below 0.08-0.1% (SWAN 1972 Hartmann etal. The roots of spruce seedlings lacking phosphorus are long and thin (INGESTAD 1959). Later on they slowly senesce but are not shed, thus contrasting with the remaining younger, healthy needles (BAULE and FRICKER 1973). Older needles change color more quickly and to a greater degree than younger needles. In older trees, needles are grey or bluish-grey, and later they turn purple, purplish-brown, or even red (BAULE and FRICKER1973). Old needles are dark green, often with a purplish hue. Young needles of seedlings growing under conditions of phosphorus deficiency are short and yellow, especially at tips (INGESTAD 1959). Clear symptoms of nitrogen deficiency are observed when its concentration on a needle dry mass basis falls below 1% (Fiedler etal. Root growth is comparatively more vigorous however, the roots may grow long and thin (INGESTAD 1959 Baule and FRICKER 1973). Summer shoots do not develop and the growth period is often shortened (Baule and Fricker 1973 Fiedler et al. The shoots are short and poorly branched. Chlorosis arising from nitrogen deficiency is typically observed throughout the tree crown in all needle age classes and often appears evenly distributed over the entire forest stand (Hartmann et al. Mature needles may appear small and yellowish-green in color (Baule and FRICKER1973 FIEDLER et al. The young needles, especially the tips appear light yellow (INGESTAD 1959). Spruce seedlings growing under conditions of nitrogen deficiency exhibit poor development and slower growth (FOBER and GIERTYCH 1968 Swan 1972 FIEDLER etal. Symptoms of deficiency and toxicity 7.2.2.1. 1988), and the measurement of electrical resistance in the cambium zone (Huttl et al. 1971), measurement of organic acid concentrations in needles (CLEMENT 1977), chlorophyll fluorescence (BAILLON etal. Other reported methods for evaluating the response of spruce trees to fertilization include: needle color assessment on the youngest shoots (LUUKKANEN et al. These methods include visual evaluation of plants, chemical analysis of the soil, needles, and whole seedlings, as well as growth (HUNGER and NEBE 1964 LEAF 1970 WITT 1987). (1987) found that needle analysis frequently provides more information on the nutritional status of trees than does routine soil analyses.Įmploying multiple methods at the same time should increase the accuracy of the assessment of the nutritional needs of trees. FIEDLER and NEBE (1963) as well as HUNGER and FIEDLER (1965) observed a negative correlation between tree height and the C:N ratio in the humus horizon. EVERS (1967a, b, 1972) suggests that soil nutrient status depends on the ratios among elements in the soil. The nutrient requirements of trees may also be based on soil analyses. 1991) as well as whole plants, especially small seedlings (Kral 1961 FOBER and GIERTYCH 1968, 1970a FOBER 1974). Roots, wood, or bark are also sampled for chemical analyses (INGESTAD 1959 OVINGTON 1959 FORNES et al. 1970), preferably from the same sector of the tree crown (JUNG and RIEHLE1966), and separately for each needle age class cohort or from the youngest age class (LINDER 1995). In spruce, needles sampled for this purpose should be collected be tween mid-August and mid-September (Touzet et al. The nutritional status of trees is most frequently assessed on the basis of the elemental analysis of leaves (MATERNA 1960 KRAL 1963 FIEDLER et al. Methods in evaluating mineral requirements
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