Brazil Eucalyptus 

Potential Productivity

 (BEPP)

This is a cooperative research project of 2 universities (University of Sao Paulo ESALQ and Colorado State University) 6 forest companies (VCP, International Paper, Veracel, Bahia Sul Cellulose, Copener Florestal, and Aracruz), and the Rocky Mountain Research Station of the USDA Forest Service.

Eucalyptus plantations in Brazil are among the most productive ecosystems in the world, covering millions of hectares and typically producing more than 40 m³/ha/yr of wood.  The world-record rates of production are sustained by intensive silviculture, including genetic selection of superior trees, clonal propagation, intensive site preparation, and fertilization.  

The BEPP group has developed several projects to describe and test factors that determine the growth of Eucalyptus plantations.

BEPP Project #1:  Eucalyptus Production across a Geographic Gradient:

As part of his PhD thesis at Colorado State University, Jose Luis Stape from USP/ESALQ collaborated with Copener Florestal to examine patterns in production ecology along a geographic gradient from high-rainfall locations near the coast, to low-rainfall locations inland.  They examined the role of changing rates of resource supply across this gradient, as well as the rate of resource use and efficiency of resource use.  The efficiency of resource use increased substantially for all resources (light, water, nitrogen) in response to increases in water availability.  The influence of "water" was evident in both the availability of water in the soil (from rainfall), and the humidity of the atmosphere.  A manuscript is available:  Eucalyptus production and the supply, use and efficiency of use of water, light and nitrogen across a geographic gradient in Brazil.  A concept-oriented manuscript on resource use efficiency is also available:  Thinking about efficiency of resource use in forests.

BEPP Project #2:  Response of a Eucalyptus Plantation to Irrigation and Intensive Fertilization

Jose Stape and Copener also used experimental manipulations of resource supply to examine the role of resource supplies in the potential productivity of Eucalyptus stands.  Replicated plots with Eucalyptus hybrid clones were irrigated and intensively fertilized, and the entire C budget was estimated for 2 years (one unusually wet with no drought, and the other a normal year with a seasonal drought).    The stand was 3 yr old when the experiment was established, and the treatments of irrigation and fertilization will continue through age 6 yr.  The results from BEPP Project #1 and #2 are being used to parameterize an empirical model of forest growth, and the 3-PG ecophysiology model of forest growth.  At age 5 years (after 2 yr of treatment):

A manuscript of the 3-PG modeling:  Testing the 3-PG process-based model to simulate Eucalyptus growth with an objective approach to the soil fertility rating parameter.

BEPP Project #3:  The Individual Tree/Stand Structure Hypothesis

These results led to a new hypothesis.  If the use of resources (light, water, nutrients) remains high in older forests, but production declines, then the production per unit of resource used must decline.  We hypothesized that this decline in efficiency might result from the increasing variation in sizes of trees within stands.  Dominant trees would continue to increase their rates of resource use -- and would sustain a high rate of production per unit of resource used.  Suppressed trees would gradually acquire less light, water, and nutrients as they lose to dominant trees, but their suppressed condition would drive down their efficiency of using resources even faster.

Our first test of this hypothesis involved comparing the efficiency of dominant (largest 25%) trees and suppressed trees (the other 75%) in a plantation in Hawaii.  As predicted, the dominant trees used 40-50% of the entire stand's resources, but contributed 60% of the entire stands growth; the dominant trees were twice as efficient in producing wood per unit of resource used:  (for the full paper:  http://www.cnr.colostate.edu/~dan/papers/Ecosystems_5_2002.pdf) 

Clonal plantations are much more uniform in structure (left side of photo) than seedling-origin stands (right side of photo), and we're using this uniformity to examine a single-tree/stand-structure hypothesis for age-related declines in stand growth.

Each company has installed a replicated experiment where the same clonal material is planted on Day 0 (uniform stand) or over a period of 80 day (heterogeneous stand), as well as an additional treatment using trees derived from seeds.  The experiments also include irrigation and fertilization treatments to prevent any change in the supply of water or nutrients over time from confounding the age-related patterns.  The Individual Tree/Stand Structure hypothesis predicts that little (if any) growth decline will be seen in the uniform clonal plots, whereas the heterogeneous clonal plots and seedling plots will show the classic decline in stem growth.

Stand structure at 24 months for the International Paper site (uniform on left; staggered on right):

Between 18 and 24 months of age, the uniform clone treatment and staggered-planting-time clone treatment at VCP were equally productive, accumulating aboveground biomass at a rate of 33 Mg/ha annually. The scheme for developing uniform and heterogeneous stand structures by varying planting times worked well (figure above).  These trends are consistent with expectations for the period of maximum growth -- the individual tree/stand structure hypothesis predicts the growth of the heterogeneous stand will begin to decline in the next year or two, while the uniform stand will sustain the high rate of production.
 

Project Collaborators:

   Second Annual Meeting of BEPP -- at Aracruz site (24 months, January 2003)

2nd Annual Meeting

Aracruz Celulose S.A.

16-17 January 2003