Báo cáo lâm nghiệp: "Dynamics of light interception, leaf area and biomass production in the establishment year in Populus clones"

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Nội dung Text: Báo cáo lâm nghiệp: "Dynamics of light interception, leaf area and biomass production in the establishment year in Populus clones"

Dynamics of light interception, leaf area and biomass production Populus clones in in the establishment year J.G. Isebrands 1 G.E. Scarascia-Mugnozza 1 T.M. 1 Hinckley and R.F. Stettler R.F. 1tettler 1 Resources, University of Washington, Seattle, WA 98195, U.S.A., College of Forest 2 University of Tuscia, 01100 Viterbo, Italy, and Institute of Forest Biology, 3 Sciences Laboratory, USDA-Forest Service, Rhinelander, WI 54501,U.S.A. Forestry each of the parental species, P. trichocarpa (1- Introduction 12) and P. deltoides (111-5). Growing conditions were near optimal with periodic fertilization and irrigation. Monthly biomass and leaf area mea- Biomass production in agricultural crops is surements were collected from whole-tree directly related to the radiant energy inter- harvests of 4-6 trees per clone. Light intercep- ception by foliage (Monteith, 1981). Linder tion was recorded with a quantum sensor locat- ed above the canopy and a quantum line (1985) demonstrated that a linear relation- sensor on the ground, below the canopy, ship between solar radiation capture and connected to integrators. The location of the biomass production also exists for forest line sensor was randomly changed every week stands. However, variability in canopy among permanent growth plots of the 4 clones. architecture among plant genotypes could strongly influence the efficiency of conver- sion of solar energy into biomass produc- tion. In this study, we characterized this Results relationship between light interception and biomass growth on 4 very different Popu- Light interception of the clones increased lus clones during the establishment year. throughout the growing season until a maximum value of 95% (clone 11-11) was reached at the end of September 1985 (Fig. 1Highest light interception for the Materials and Methods clone III-5 (P. deltoides) was only 75%, the lowest value for the study clones; maxi- In February 1985, a 1 x 1 m plantation was mum interception for the other 2 clones established in Puyallup, WA, U.S.A., with was intermediate (85%). At the end of the unrooted, 25 cm hardwood cuttings of 4 poplar season (mid-November), the 2 parental clones, including 2 hybrids P. trichocarpa x P. clones and hybrid 44-136 had already deltoides (11-11 and 44-136) and a clone of
shed all their leaves; however, light inter- In contrast to the differences in total LAI, the 2 hybrid c!lones had quite similar LAI ception was still around 45%, apparently values for leaves on the main stem. because of the absorption of radiation by stem and branches. At that time, hybrid Ranking of clones for biomass produc- clone 11-11 still retained part of its foliage tion during the establishment year was and light absorption was around 75%. similar to that of light interception and LAI; the average tree of hybrid clone 11- a clone was directly Light absorption by 11 produced a total biomass of 1 kg of dry leaf area (Fig. 2); again related to its total hybrid 11-11 had the maximum leaf area weight, while only 0.4 kg were produced index (LAI) (2.9), followed by hybrid 44- by P. deltoidt clone 111-5. The linear S 1 2 parental clones, P. tri- 136 (1.5) and the regression of cumulative biomass on chocarpa (1.2) and P. deltoides (1.0). cumulative intercepted radiation of the 4 clones had an R2 0.87, with a conver- of Large differences existed among poplar genotypes in crown structure; in clones sion efficiency of 0.55 g-MJ- (Fig. 3). This 1 11-11 and 1-12, almost 50% of the total parameter showed large variability among clones with the highest value occurring in leaf area consisted of leaves on branches, clone 11-11 (0.8 g-MJ- and the lowest in whereas in the other 2 clones, 44-136 and ) 1 111-5, this proportion was only 15% (Fig. 2). 111-5 (0.4 g ). 1 MJ- ’. )
Discussion and Conclusion biomass production gave a high R2 value, although a curvilinear function might be more appropriate. This indicates that the Total biomass production by P. trichocar- efficiency of energy conversion into bio- pa x P. deltoides hybrid clone 11-11 was mass changes throughout the growing 2.5 times that by the parental clone III-5 season and for a given plant material. (P. deltoides), although it should be noted that the latter is not native to the Pacific Another significant source of variation Northwest. The significant relationship in the conversion efficiency is the geno- between biomass growth and leaf area or type, even within the same species or the radiation interception has also been same genus. The 2 hybrid clones (11-11 observed by Zavitkovski et al. (1976) on and 44-136) used in this experiment Populus and by Linder (1985) on Euca- showed the highest conversion efficien- lyptus, although for this latter genus only cies, compared to the parental clones. indirect estimations of light interception Even though their total leaf area indices at were used. In the present study, the linear the end of the growing season were quite regression between light interception and different, their leaf the main stem areas on
almost the same; these leaves are References were far the most efficient for light conver- by sion into biomass, as shown by lsebrands lsebrands J.G., Nelson N.D., Dickmann D.I. & Michael D.A. (1983) Yield physiology of short et al. (1983). rotation intensive cultured poplars. In: Inten- Crown architecture, that is the combina- sive Plantation C:ulture: 12 Years Research. tion of total leaf area, leaf area distribution (Hansen E., ed.), USDA For. Serv. Gen. Tech. within crowns, leaf and branch morpholo- Pap. NC-91. pp. 77-93 gy and orientation, seems to play a major Linder S. (1985) F’otential and actual production in Australian forest stands. In: Research for role, since it influences not only the inter- Forest Management (Landsberg J.J. & Parsons ception of solar radiation but also its W., eds.), CSIRO, Melbourne, pp. 11-35 conversion into biomass. Monteith J.L. (19131) Does light limit crop pro- duction? In: Physiological Processes Limiting Plant Productivity. (Johnson C.B., ed.), Butter- worths, London, plo. 23-38 Acknowledgments Zavitkovski J., isebrands J.G. & Dawson D.H. (1976) Productivity and utilization potential of short-rotation Populus in the Lake States. In: Research performed under subcontract no. 19X-43382C with Oak Ridge National Laborato- Proc. Symp. on eastern Cottonwood and Re- lated Species. (Thielges B.A. & Land S.B. Jr., ry under Martin Marietta Energy Systems, Inc. contract DE-AC05-840R21400 with the U.S. eds.), Louisiana State University, Baton Rouge, Department of Energy. pp. 392-401