Forest Succession and Biomass Accumulation
of 70 Year-Old Experimental Plots in
BLACK ROCK FOREST, NY
Salima Jones
June 2002
ENV MEASUREMENTS
Prof. Peter Bower
Contributions made by Environmental Measurements Class Spring 2002:
Jennifer Stamatelos, Sally Reynolds, Stephanie Daddi, Grace Kim, and Chris Duerkes
TABLE OF CONTENTS
PAGE #
2 ABSTRACT
3 INTRODUCTION
3 What is BRF?
5 Purpose
7 Experimental Plots
8 METHODS AND MATERIALS
8 Biomass Equations and DBH
10 Red Oak
11 Chestnut Oak
12 RESULTS
12 Stem Survival Rates on the Experimental Plots
13 Species Composition
15 Red Oak
18 Chestnut Oak
18 DISCUSSION
APPENDICES
BIBLIOGRAPHY
Forest Succession and Biomass Accumulation of 70 Year-Old Experimental Plots in Black Rock Forest, NY
Abstract
Managers of Black Rock Forest, in southeast New York, have been collecting Diameter-at-Breast-Height (DBH) data since 1931, on two experimental plots. This data, along with records of species composition and environmental changes reveal rates of tree growth, survival, and succession of this deciduous forest. Initially, the purpose of the research was to observe ways to improve accumulation in stem growth of marketable trees within the forest. Using allometric biomass equations, the DBH data allowed the students of the Barnard College Environmental Science Department to analyze and compare the biomass accumulation and carbon sequestration of a pair of experimental plots. The results show the biomass equations accurately predict the stem biomass based on its DBH. The number of stems on the experimental plots has decreased though biomass continues to accumulate demonstrating a trend toward fewer, larger trees.
Introduction
What is BRF?
Black Rock Forest (BRF) is a 3700 acre (1530 ha) oak-dominated, aggrading,
Eastern deciduous forest preserve located in the Hudson Highlands of Cornwall, New York as shown in MAP 1. This area is situated on the west bank of the Hudson River, 50 miles (80 km) north of New York City. The steep-sided valleys run northeast to southwest. Elevations range from 110 to 450 meters above sea level. (Schuster, 2002) View MAP 3 and MAP 4 for a more detailed layout of BRF.
The last glacial age, occurring about 14,000 years ago, left the Highlands with a thin layer of rock strewn soil supporting this forest. (Maher, 1996) "The soils are predominately brown forest solid with bedrock or glacial till parent material at depths ranging from 25cm to 1m soil is acidic and low in nutrients."(Schuster, 2002) The average annual precipitation is 1.2 m. Seasonal temperature changes average -2.7 degrees Celsius in January to 23.4 degrees in July. (Schuster, 2002)
Ernest Stillman established BRF in 1928 as a facility of forest management research. The forest, managed by Harvard University from 1949 through 1989, is composed of diverse habitats ranging from young and mature forests, stream, ponds and wetlands. Since 1989, the Black Rock Forest Consortium, a group of educational and research institutions, use the preserve as a field station, promotes scientific research within the forest and manages its ecosystem. Information on Black Rock Forest can be found at http://www.blackrockforest.org/
BRF before 1928 was subject to extremely variable and rapid land use changes as is illustrated in the timeline of IMAGE 1. During the 19th century, the mountain residents of the Highlands developed a "diversified economy based on agriculture, lumbering, dairying, fruit growing, then tourism." (Maher, 1996) Given its thin black soils and steep topography, Black Rock was poor farming land and never extensively cultivated. "The good black soils are generally limited to the valley bottoms and coves. ' Only 7.5% or 270 acres has been cleared for, [mostly subsistence] farming throughout its history. The most intense farming regions within BRF are between the mountains and its flat areas.” (Maher, 1996)
Black Rock Forest residents would cut trees for home use and market, particularly as fuel. The wood was used to heat homes and power the Industrial Revolution until the impetus of coal followed by gas and electricity overpowered its practical use. Approximately 50% of the total land within Black Rock has been cleared for lumbering purposes. (Maher, 1996) All and all, BRF has been clear-cut at least two times in its history. By 1928, the poor agricultural and logging market, the repeated clear-cutting and frequent fires resulted in the regeneration of hardwoods in the forest. At the turn of the twentieth century, Gifford Pinchot, the first American trained as a professional forester, influenced Ernest Stillman with his "wise use" conservation ethic. The country's [timber] resources should be used efficiently to promote "the greatest good of the greatest number for the longest time." The inception of BRF began as an experimental forest to improve timber production. (Maher, 1996)
Purpose
As a member of Professor Bower’s Environmental Measurements class at Barnard College, the research objective at BRF was to collect the 2002 DBH data for the two experimental plots, namely 5a4c (the control plot), and 5a4 (the treatment plot). The
plots are located on either side of Aleck Meadow Road, just west of the Upper Reservoir in BRF.
Using biomass equations, DAGBIK and biomass accumulation over time in BRF was calculated and analyzed. Comparing the data between the plots projected the stability of a thinned or natural forest, and improved rates of biomass accumulation. Additionally, the accuracy of these equations was tested. On March 1, 2002, the Environmental Measurements class visited BRF with the purpose of cutting down a red oak, measuring its wet and eventually its wet weight, as well as calculating its other dimensions and compare its manually measured biomass to the calculated biomass observed from applied the red oak equation. In October of 2000, a dead chestnut oak was cut down for the same purpose.
Experimental plots
The two plots, 5a4c and 5a4, are respectively a control and treatment plot whose growth has been monitored, and data collected since 1931 and every few years since. "In 1930, an inventory of trees of 'cordwood size,' roughly greater than 10cm [3.9 in] in diameter-at-breast-height (DBH), was made of BRF. [A second inventory was taken in 1985.] The forest was subdivided into 150 stands based on species composition and average tree density selected on the basis of its intermediate forest elevation and typical forest characteristics. The plots are part of a pair of four long-term experimental plots of roughly the same size. The surface area of 5a4c is .0406 hectares, and 5a4 is .041 hectares.
The treatment plots, treated once in 1931, were thinned of "dead, diseased, and dying trees including species considered less economically desirable."(Schuster, 2002) This thinning amounted to the removal of about 1/3 of the basal area of the treatment plots or about 50% of its biomass. Plot 5a4 was thinned of particularly more stems than the other treatment plots, almost 60% compared to 5a4c. (Schuster, 2002) The treatment was also applied to thirty acres surrounding the hillside of plot 5a4. The number of trees and the species composition of plots 5a4 and 5a4c were monitored and compared over time. The purpose of this experiment was to answer the question, “ Will ‘thinning’ enhance the growth of ‘marketable’ trees?” Growth of the trees, which will be referred to as stems interchangeably, is determined by measurements of DBH or diameter-at-breast height. Since this initial forest management experiment, the two plots have been used for a series of other research projects since it is rare to find plots “untouched” for such a along period of time and with available data.
Methods And Materials
Biomass Equations and DBH
The DBH or diameter-at-breast height is the diameter of a tree measured at a height of 1.37 meters, which is approximately the breast height of a person. The materials needed for this field project include: a field book, a clipboard, diameter measuring tape in inches, plastic ribbon, a listing of DBH measurements taken of plots 5a4c and 5a4 since 1931, a pencil, and the “Biomass Equations for Major Tree Species of the Northeast” compiled by Louise M.Tritton and James W. Hornbeck:
Species: Equation
*red oak 11.0417-(0.5258*DBH*25.4)+(0.0076788* (DBH^2)*(25.4^2))
*sugar maple 5.248-(0.3661* DBH *25.4)+(0.007605*(DBH^2)*(25.4^2))
+white oak (((10^((LOG(DBH *2.54)*2.1666)+2.3058)))+
((10^((LOG(DBH *2.54)*1.738)+1.5849))))/1000
-chestnut oak (1.5509*(DBH^2.7276))/2.205
-black birch (1.6542*(DBH^2.6606))/2.205
*red maple 6.1147-(0.3598*DBH*25.4)+(0.006344*(DBH^2)*(25.4^2))
-black cherry (1.8082*(DBH^2.6174))/2.205
*black oak red oak equation
*gray birch 9.3701-(0.4489*DBH *25.4)+(0.007496*(DBH^2)*(25.4^2))
-hickories (2.034*(DBH^2.6349))/2.205
*beech 5.3373-(0.3257*DBH*25.4)+(0.007173*(DBH^2)*(25.4^2))
+scarlet oak ((10^((LOG(DBH *2.54)*2.3948)+2.19))+
((10^((LOG(DBH *2.54)*1.6436)+1.8565))))/1000
-hemlock (1.3449*(DBH^2.45))/2.205
*general h: bg, mw 5.5247-(0.3352*DBH *25.4)+(0.006551*(DBH^2)*(25.4^2))
black gum, moosewood (striped maple)
*general s 4.5966-(0.2364*DBH *25.4)+(0.00411*(DBH^2)*(25.4^2))
dogwood
*Monteith, D,B, 1979. "Whole tree weight tables for NY". AFRI Research Report 40, Univ. of Syracuse, NY 40p.
+Whittaker and Woodwell. 1968 "Dimension and production relations of trees and shrubs in the Brookhaven Forest", NY. Journal of Ecology. 56:1-25
-Brennerman, B.B., Frederick, Gardner, Schoenhofen an Marsh. 1978. "Biomass of species and stands of West Virginia Hardwoods". pgs.159-178 in P.E. Pope ed., Proceedings Central Hardwoods Forest Conference II. Purdue Univ., West Lafayette, In.
**Pastor et al., 1984, "Biomass Production Using Generalized Allometric Regressions for Northeast Tree Species" Forest Ecology Management, 7:265-274. (except White Oak and Chestnut Oak: Whittaker et al., 1974)
The tree species abbreviations presented in TABLE 2 are used frequently through out this text. Please observe carefully.
The biomass equations of TABLE 1 are allometric equations that have been revised for the purpose of measuring DBH in inches by Dr. William Schuster, the BRF Director. Excel is used to organize and calculate our data.
Allometric equations are equations created by measuring an easily measurable aspect of an “object” and correlating that aspect to parts of an object that are not as easy to measure. The equations correlate the easily measurable DBH of a tree and correlate it to the dry above ground biomass of a tree. This method of calculation is difficult because controls have to be set. Each species of tree requires a different equation considering species growth rates and regional variations in growth rates given climate, soil and other geographical conditions.
The equations are species and region specific and determine the dry above ground biomass in kilograms (DAGBIK) of each individual tree and, by sum, of each plot. This DBH data, collected March 8, 2002 represent conditions of the 2001 growing season. Data taken after May represent the conditions at the end of the season for that year. (Schuster, 2002) This information was added to data collected every five years upon average since 1931, and each year after 1994. Approximately 50% of deciduous forest biomass is stored carbon.
Two groups of participants measured the DBH of the live trees present on either
plot 5a4c and 5a4. By referring to the DBH listing, we were able to determine if a tree had previously died, though some had noticeably past on. Biomass for unplotted and dead trees is not included in our data set. Using our diameter measuring tape, the DBH of each tree was measured and remeasured by another participant for group accuracy.
A plastic ribbon was then tied around each tree to mark it as having been measured. Our measurements were then recorded in field books and transferred to the DBH listing as data for the 2002, though it is correctly considered a 2001 addition.
The dimensions of the experimental plot are fairly square, as illustrated in IMAGE 4. The area was calculated using the following equation: Ö(s(s-a)(s-b)(s-c)), where s= (1/2)(a+b+c).
Red Oak
The red oak tree, used to test the accuracy of the biomass equations, required additional field and lab materials that include: a transponder, clinometer, DBH measuring tape, chainsaw, spring scale, a tractor, heavy rope, permanent marker, Mettler lab scale and a large oven. The RED OAK SLIDESHOW relives this field experience.
Three methods were used to measure the height of the tree. The transponder, clinometer, and measuring tape were used separately to tell us the height of the red oak tree. A transponder is a digital tool that bounces soundwaves to calculate distance. A clinometer is a projector-like mechanical tool projects height at an angle from a specific distance. The transponder and clinometer methods use trigonometry to determine height of the red oak. In a right triangle, knowing the length of the base of the triangle and the adjacent angle, the length of the side opposite that angle (the tangent) can be calculated. The distance and angle of the tree from where the measurements were taken are approximately 135.5 m and 30.3 degrees.
To observe wet weight of this red oak, the trunk was cut into, roughly, two-foot thick boles. The branches were trimmed and weighed in separate bundles. 13 two-inch thick boles were also trimmed to be dried and remeasured for future comparisons. The 2-inch thick bole #11 was cut into four similar sized pieces, reweighed using the Mettler scale in the lab, and baked in an oven at a fairly consistent temperature of 115 degrees Celsius over a period of 60 days. This temperature is preferred over a higher temperature to maximize the amount of water evaporated and limit the evaporation of other volatile materials that exist in the bole, as well as prevent the burning of the wood.
Chestnut Oak
The materials used to measure the chestnut oak were the same as for the red oak except for the use of chalk. The DBH of the chestnut oak tree was measured before it was cut into four-foot long boles. The rope was used to bundle the branches. Using chalk, the bundles and boles were numbered. The spring scale, attached to a bulldozer, was used to measure the field weight. The truck transported the chestnut oak pieces to a shed for drying. The chestnut oak wet weight was measured manually at the time it was felled. The dry weight, measured a year later, was then compared to the DAGBIK calculated from the chestnut oak equation.
RESULTS
Stem Survival Rates on the Experimental Plots
The area of the experimental plots was last clear-cut in 1905; the oldest trees are about 95 years old. Pollen assemblages taken from a sediment core of Sphagnum Pond reveal oak trees have been abundant in this area for over 10,000 years. (Maenzer-Gmelch, 1996) Over the past seventy years, the number of stems (trees) on plots 5a4c and 5a4 has decreased about 75% each.
Using the long-term DBH data, organized in TABLE 13a for 5a4c, and TABLE 14a for 5a4, the following survival statistics were determined.