Needle mass, fine root and stem wood production in response to silvicultural treatment, tree size and competitive status in radiata pine stands

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Abstract

The effect of silvicultural regime, tree size and competitive status on needle mass, root fine production and allocation of carbon to stem wood was analyzed. Three stands with different agroforestry treatments were compared with one managed traditionally. Data were obtained through destructive sampling of 36 trees and analyzed by ANOVA and regression analysis. The analysis allowed us to conclude that foliage mass was not affected by the silvicultural treatment, tree size or competitive status. Fine root biomass showed an inverse relationship with fertilization. Growth efficiency was not affected by the management treatment, tree size, or intraspecific competition. The greater stem wood allocation recorded in the agroforestry treatment than in the forestry regime, is interpreted as a response to two different types of competition. Competition for light appears to induce growth in height and diameter as a function of local environment conditions. Competition for nutrients appears to reduce allocation to fine roots and increase allocation to stem wood.

Introduction

Tree growth is a function of: (i) the amount of leaf area present to absorb light and its display throughout the year; (ii) the potential carbon fixation rate per unit leaf area and (iii) the extent to which photosynthesis is limited by site resources. These factors affect the photosynthetic processes, as well as respiration, determining carbon resources available for growth of stem wood and other organs (Dewar et al., 1994). However, the detailed processes that explain allocation of growth are still not fully understood and different theories exist (Waring and Running, 1998). One theory suggests that allocation of carbohydrates is based on a priority for survival that first must provide for the maintenance of living tissue. Thereafter, the ranking in priority for long-lived perennials is toward: (i) the production of photosynthetic tissue (buds, foliage); (ii) the activity and growth of fine roots; (iii) reproductive organs (flowers and seeds); (iv) extension of branches, stem and large diameter roots (Waring, 1987, Oliver and Larson, 1996). The last priority, in theory, if carbohydrates are available, is to diameter growth and production of defensive compounds (Waring and Schlesinger, 1985, Oliver and Larson, 1996). Based on the low priority of carbon allocation to stem wood, a growth efficiency index (GEI) has been proposed as a measure of tree vigor. This is defined as the annual growth of stem wood per unit of leaf area (Waring et al., 1980), which integrates the photosynthetic efficiency of the canopy and partitioning of resources to aboveground organs (Vose and Allen, 1988). This index is sensitive to changes in competition (Perry, 1985), cultural practices, such as irrigation or fertilization (Linder and Axelsson, 1982), and tree resistance to native diseases and insects (Mitchell et al., 1983).

Biomass allocation has also been interpreted by the pipe model theory, originally developed by Shinozaki et al. (1964). This theory considers a tree a conductive tube system linking foliage with roots, with the evolutionary advantage to favor dominance while meeting requirements for mechanical support. This theory is based on the concept that the water conducting sapwood area should be proportional to the amount of foliage in a tree’s crown (Margolis et al., 1995). Using this model, along with the functional balance theory, Valentine (1985) and Mäkelä (1986) demonstrated that a higher proportion of stem growth occurs in suppressed trees than in dominant trees. Therefore allocation patterns in trees are reflected in stem growth, with rapid increment in young trees, moderate growth by mature trees, and decreasing growth with advanced age (Mäkelä, 1990). For this observed pattern in stem growth, the pipe model theory serves well with its underlying assumption of stability in the ratio of foliage area to sapwood area (Makela, 1990, Bartelink, 1998). However, this model is inadequate to explain growth allocation, because its parameters are complex functions that reflect local environmental conditions as well as genetic properties of a species (Rennols, 1994).

In this study, we determine empirically how growth is affected by silvicultural treatment, and the extent that, tree size, and competition among trees and pasture grasses, affect growth efficiency and the fraction of photosynthate allocated to stems in plantations of Pinus radiata D. Don, in a semiarid region of Chile.

Section snippets

Study site and experimental design

An agroforestry experiment was established by Corporación Nacional Forestal, in Tanumé, community of Pichilemu, VI Region, Chile (34°9′S–34°15′S latitude; 72°53′W–72°59′W longitude). Soils of this area are classified as Alfisol, suborder Xeralfs, typical of a subhumid temperate climate, with six months of drought. The annual average precipitation at the study site is ∼700 mm, with a minimum average temperature of 8.6 °C in July and a maximum average temperature of 15.4 °C in January, based on data

Needle and root fine production and stem wood growth

Total biomass per tree in the agroforestry treatment (T3) was 2.2–2.5 times larger than in the pure forestry treatment. Although no significant difference was observed in aboveground biomass among the different treatments, fine root mass was significantly lower in T3 than in other treatments.

We used ANCOVA models only after adjusting for Dbh as a co-variable to determine whether there were significant differences of the biomass components among treatments. The ANCOVA indicated that needle mass

Needle production, fine root and stem growth

Foliage mass and leaf area could both be predicted accurately from measurement of Dbh. Allometric relations constructed between Dbh and needle production showed a particularly high correlation (Fig. 1a). Similar high correlations between Dbh and foliage mass have been reported for other species (e.g. St. Clair, 1993, Bartelink, 1996, Naidu et al., 1998). Dbh represents the culmination of all previous growth at that height, while crown biomass, and especially the biomass of needles, is

Conclusions

Needle mass was not affected by the silvicultural treatments included in this study. However, tree stem and total biomass were significantly larger in the agroforestry than in the forestry treatments. This we attribute to a shift in allocation away from fine roots to stem wood in response to fertilization. Growth efficiency was not affected by the silvicultural treatment, tree size, nor competition. The greater allocation to stem wood observed in the agroforestry treatments is attributed to two

Acknowledgements

We would like to thank Corporación Nacional Forestal (CONAF) and Ministerio de Planificación (MIDEPLAN) for its financial support. Mr. César Cabrera, Forest Engineer of CONAF, and field workers of Centro Experimental Forestal Tanumé. Professor R.H. Waring made substantial editorial improvements in earlier drafts of the manuscript for which I am most appreciative.

References (43)

  • Assmann, E., 1970. The Principles of Forest Yield Study. Pergamon Press, New York, 506...
  • E Axelsson et al.

    Changes in carbon allocation patterns in spruce and pine trees following irrigation and fertilization

    Tree Physiol.

    (1986)
  • H.H Bartelink

    A model of dry matter partitioning in trees

    Tree Physiol.

    (1998)
  • P.N Beets et al.

    Carbon partitioning in Pinus radiata stands in relation to foliage nitrogen status

    Tree Physiol.

    (1996)
  • M.G.R Cannel et al.

    Carbon allocation in trees

    Adv. Ecol. Res.

    (1994)
  • R.C Dewar et al.

    Environmental influences on carbon allocation in pines

    Ecol. Bull.

    (1994)
  • Husch, B., Miller, C., Beers, T., 1982. Forest Mensuration. Krieger Publishing, New York, 402...
  • Kellomäki, S., Oker-Blom, P., Kuuluvainen, T., 1985. The effect of crown and canopy structure on light interception and...
  • Linder, S., Axelsson, B., 1982. Changes in carbon uptake and allocation patterns as a result of irrigation and...
  • A Mäkelä

    Adaptation of light interception computations to stand growth model

    Silva Carelica

    (1990)
  • Margolis, H., Orem, R., Whitehead, D., Kauffmann, M.R., 1995. Leaf area dynamics of conifer forest. In: Smith, W.K.,...
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      Increasing radial increments are common after disturbances that increases light availability (Goudiaby et al., 2012; Myer, 1963). The relationship between light availability and main trunk GE in this study is congruent with evidence that main trunk GE increases with light availability due to a reduction in competition (Berrill and O’Hara, 2007; Gilmore and Seymour, 1996; Mainwaring and Maguire, 2004; O’Hara et al., 2001; Seymour and Kenefic, 2002; but see Rodrı́guez et al., 2003). Although direct measurements of openness or exposed crown area may not be practical in many situations, our results highlight DDCV as a promising metric to account for variation in tree-level light availability using ground-based measurements.

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