Planting stock quality, root growth capacity, and field performance of three boreal conifers.
1980; Springer Science+Business Media; Volume: 10; Issue: 1 Linguagem: Inglês
ISSN
1179-5395
Autores Tópico(s)Forest Biomass Utilization and Management
ResumoThe influence of provenance and length of storage on growth (RGC) was determined in 2 + 0 jack pine (Pinus banksiana (Lamb.), 3 + 0 black spruce (Picea mariana (Mill.) B.S.P.), and 3 + 0 white spruce (P. glauca (Moench) Voss.). All plants were random samples of spring-lifted production-run planting stock raised by the Ontario Ministry of Natural Resources and used in Canadian Forestry Service stand establishment trials in 1972 and 1973. Except for some freshand field-stored stock used in the first two RGC tests in 1972, all stock was cold stored, then withdrawn as required after specified storage periods of up to 5 months. The number of roots that elongated in solution culture during the 21-day tests were counted on a total of 3594 trees. RGC differed greatly between the two test environments, but common to both were: a rapid decline with increasing length of storage; marked differences between species in the order jack pine > black spruce > white spruce; and substantial differences between provenances, the more northerly provenances showing higher RGC. The field significance of these results is examined in terms of survival and growth up to the fourth growing season after outplanting. Several correlations were significant, but relationships were generally obscured by great within-treatment variability. INTRODUCTION The tree whose system produces new growth within a few days after outplanting will probably survive and grow as well as site conditions permit, but if growth is delayed, outplant growth will be reduced. Without growth, mortality is certain. Field performance in relation to growth is central to the question of planting stock quality and its prediction (Sutton, 1979). Part A of this three-part paper is an account of tests of growth (RGC) (Stone and Jenkinson, 1970; Burdett, 1979) on sub-samples of planting stock used in plantation establishment trials in Ontario in 1972 and 1973. In Part B, first-year through fourth-year field performance data from sequential extended planting season outplantings are discussed. In Part C, correlations between RGC and field performance are examined. N.Z. J . For . Sci. 10(1): 54-71 (1980). No. 1 Sutton — Root Growth Capacity and Field Performance 55 PART A: ROOT GROWTH CAPACITY (RGC) The physiological state of a tree is intimately dependent on plant growth regulators as well as on nutrition, internal water status, and carbohydrate reserves. This physiological state affects the ability of a tree to augment its system after outplanting. Attempts to estimate this ability in planting stock have been based on the amount of growth made during a specified period in a standard environment. Such an estimate has been variously termed root-regenerating potential or RRP (cf. Stone, 1955; Stone et al, 1962), root-regenerating capacity (cf. Krugman and Stone, 1966), and root growth capacity or RGC (cf. Stone and Jenkinson, 1970; Burdett, 1979)The latter term (RGC) avoids using the word regenerating in a sense at variance with its morphogenetic meaning. Thus RGC cannot be determined directly. In spite of some recent contrary indications relating to fresh (not cold-stored) Southern pine stock (cf. Blair and Cech, 1974), the seemingly capricious correlation between planting stock morphology and quality has long been the bane of the regeneration forester. Wakeley (1948) summed up the situation very well: Grades applied to nursery stock can be useful only so far as they distinguish seedlings with a high for survival and growth after planting from those with a low capacity. . . . In the middle 1930s . . . evidence developed that . . . morphological grades coincided less well with true grades than had at first appeared, and were therefore resulting in the use of many seedlings foredoomed to die and the rejection of many seedlings able to survive. Wakeley dealt with the Southern pines, but he noted that a similar situation may occur in other regions. Materials and Methods In 1972 and 1973, production-run 2 + 0 jack pine (Pinus banksianaLamb.), 3 + 0 black spruce (Picea mariana (Mill.) B.S.P.), and 3 + 0 white spruce (Picea glauca (Moench) Voss) planting stock was obtained from the Ontario Ministry of Natural Resources Swastika nursery (48°0.1'N, 80°22'W) for stand establishment studies in the boreal forest of Ontario. The studies included plantings both during the regular (spring) planting season and through an extended (summer through autumn) planting season. In both years, the stock used had been spring-lifted, graded, bundled, and bagged during normal operations. Then, except for the first batch of stock used fresh or after 4 weeks of field storage in 1972, the stock was immediately put into cold storage at the nursery. In both years, batches of 2000 trees per species were withdrawn from storage every 2 weeks through the growing season. Alternate batches were randomly subsampled by the bundle to provide a grand total of 3594 trees for RGC testing. Samples of both provenances (Ontario Ministry of Natural Resources seed zones 3E and 4E) used in the conventional spring planting experiments (to be reported elsewhere) were taken as soon as the stock reached the planting site, and were removed within 24 hours to the Great Lakes Forest Research Centre where RGC and moisture contents were determined. In 1972, this planting stock fortuitously remained heeled in at the planting site for more than a month and thus could be resampled and tested, together with 4E stock newly taken from cold storage, in the second RGC test. Thereafter in 1972 throughout the extended planting season studies, only the 4E provenance was used. In 1973, 3E and 4E stock were compared in the first test; only 4E stock was used thereafter. 56 New Zealand Journal of Forestry Science Vol. 10 For RGC determination, the trees were washed clean and examined (in vain) for the presence of freshly elongated roots, then grown in 0.1 strength Arnon and Hoagland's nutrient solution (Hewitt, 1966), both in a laboratory growth tank (T) and in an EY15 Plant Growth Cabinet (Controlled Environment Ltd) (C). The solution, changed weekly, was circulated continuously and aerated to maintain full atmospheric partial pressure of oxygen. The total volumes circulating in the tank and chamber were 200 / and 230/, respectively. The temperature of the nutrient solution was held constant at 21 ± 1 °C The ambient temperatures were 21-27°C (T) and 21°C (C). An 18-hour photoperiod was provided with fluorescent and incandescent lamps which at plant height gave approximately 21000 lux (T) and 32 000 lux (C), respectively. The trees were removed after 21 days, and as soon as possible all fresh white roots were counted, short roots and long roots (sensu Sutton, 1969) separately. Trees were held in cool storage until counts could be made: this presented few difficulties in 1973, but in 1972 lengthy delays resulted in deterioration of samples and introduced some imprecision with consequent loss of information. Orthogonality, i.e., statistically independent equally replicated treatments, was not possible because of resource limitations. Morphological and Nutritional Characteristics of the RGC Stock Morphologically, within species, the stock did not differ significantly between RGC tests. The mean heights of the stock tested in 1972 were 17.6 cm, 25.2 cm, and 20.8 cm for jack pine, black spruce, and white spruce, respectively. The comparable values for the 1973 stock were 15.0 cm, 26.3 cm, and 16.2 cm. With the exception of jack pine, top weight, mean top and dry weights were significantly (P.01) greater in 1972 stock of all three species than in 1973 stock. For jack pine, black spruce, and white spruce, respectively, shoot dry weights (g) averaged 3.54, 3.01, and 3.03 in 1972 and 2.15, 2.96, and 2.53 in 1973; and dry weights (g) averaged 0.68, 0.85, and 0.88 in 1972, and 0.44, 0.74, and 0.57 in 1973. Variations between batches within seasons were not significant. Weights varied more than did heights, coefficients of variation averaging 57% in 1972 and 49% in 1973 for top weight and 6 5 % in 1972 and 56% in 1973 for weight, approximately double the variation in top height. Some differences in macronutrient concentration were statistically significant (Table 1), but consistent trends were not detected. RESULTS A N D DISCUSSION There were great differences between the two test situations in the number of roots showing new growth (Tables 2, 3). Although made as similar as was practical, the two environments differed in important respects, notably in light intensity and ambient relative humidity, which were higher in the growth chamber than in the growth tank. Obviously, test conditions would have to be highly standardised in all significant factors before absolute values from one test could be directly compared with those from another. For both spruces in the first RGC test in 1972 and again in 1973, complexity is further indicated by significantly higher numbers of newly elongated short roots in the growth tank than in the growth chamber. For all three species in both years the reverse No. 1 Sutton — Root Growth Capacity and Field Performance 57 TABLE 1—Macronutrient concentrations in foliage of concomitant samples at the beginning of specified RGC tests Year Test N P K Ca Mg
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