Geog350 Huxtable

Title A Study of the Leaves Lifespan in a Malaysia Rainforest
Author Ken Huxtable American River College, Geography 350 Data Acquisition in GIS; Spring 2007
Abstract Most of all Malaysia is made up of rainforest. These rainforests thrive of growth due to the tropical climate with year-round mild temperatures, high humidity, and large amount of precipitation. This study compares the leaf dynamics between the upper and lower portions of the trees in a small closed stand in a Malaysian rainforest. During an almost 4 year time period, the leave groupings, or cohorts, the leaf increase rate, leaf production rate, and the leaf loss rates where all carefully examined on the seventeen different tree species relative to their height and the leaves height. The results showed that leaf cohorts and the life spans of the leaves were lower in the upper crowns and the leaf production and loss rates were greater in the upper crowns. In analyzing the overall growing conditions, the leaves in the upper crowns increased for most of the tree species sampled.
Introduction In the tropical rainforest the environment is dependent on the vertical structures that create factors such as light level, CO2, concentration and humidity. The leaf demography in the upper and lower parts of the crown was compared and its relation to the height of the leaf was studied. The study was performed in a Malaysian rain forest over a 3.7 year period. The several trees that were sampled were of various shade-tolerant species, including three species in which multiple individuals were sampled and analyzed. This study found that the leaf production rate and leaf loss rate was faster in the upper crowns of the trees. As the height increased there was a faster rate of leaf loss and shorter life spans in the leaves, even though the leaf production was not affected. The life span and specific leaf area varied between the species, and decreased when the height was increased.
Background There are two parts of Malaysia: West Malaysia, also called Peninsular Malaysia, and East Malaysia. West Malaysia borders Thailand to the north and Singapore to the south separated by the Johore Strait. The South China Sea is to the east, while the Strait of Malacca and the Andaman Sea are to the west. East Malaysia is bordered by the South China Sea and the Sulu Sea to the north, by the Celebes Sea to the east, and by Kalimantan to the south and west. Both West and East Malaysia are made up of coastal plains and steep, narrow mountains.
The mountain range of West Malaysia is called the Main Range, or Banjaran Titiwangsa, and runs from the Thailand border south to Negeri Sembilan. The total Area in Malaysia is about 329,750 square km with about 328,550 square km being the area of land. There is about 4,675 km of coastline to both West and East Malaysia by the South China Sea, the Sulu Sea, and the Celebes Sea.
High temperatures and high humidity contribute to the tropical, rainy climate. The reason for these conditions is due to the location of Malaysia being so close to the equator. The average temperature in January is 26.5° C (79°F) and very close to the same in July. The annual rainfall is about 2,392 mm (94.2"), which makes the cultivation of rice crops the countries most practiced agricultural product and good conditions for the countries rainforest, which covers almost three-fourths of the country (Malaysia - Climate and Weather).
Methods The hypothesis of this study is whether the leaves have a longer life span in the upper or in the lower crown of the tree species in a rain forest. The study site was at Pasoh Forest Reserve, Peninsular Malaysia. This is a lowland area dominated by Dipterocaraceae with the main canopy ranging between 20 – 30 meters in height. The studies were on the leaf dynamics of trees of various heights. The leaf dynamics were compared in the upper and lower parts of the crowns of trees and in relation to the leaves' height. The actual site studied was a triangular plot with an area of 1087 square meters. Three towers, built in 1992, 31 meters above the ground with 20-meter sections linking them to each other were used as a walkway system above the canopy. Inside the plot, the diameter was measured at breast height on all of the trees greater than 5 cm in d.b.h. and the climbing of the towers was used to determine the different estimated overall upper and lower leaf heights. These estimates were than recorded on a data sheet. Seventeen trees, which included sixteen shade-tolerant species, were selected adjacent to the canopy walkway and measurements of leaf demography were taken across the canopy and the understorey layers. Sample leaves were tagged in September 1995 from the upper and lower part of the crown of the tree. All branches with sample leaves attached were sketched and the number of leaves and their position was recorded. Monthly checks where performed for missing and new growth leaves from October 1995 to May 1999.
Results The main results of this study were that the relative photosynthetic photon flux density was higher in the upper crown than the lower crown in 14 out of 16 trees that were tested. The rate of leaf production and loss were larger in the upper crown, which indicates that the leaves die off and grow back faster in the upper crown than in the lower crown. The main “take-home” message is that the leaf production and leaf loss was greater in the upper crowns than in the lower crowns for most of the trees tested. Also, the median life span and leaf cohorts were lower in the upper crowns. The turnover rate was faster in the sun leaves than the shade leaves within the crown and the leaf number increased in the upper crowns for most of the trees that had not grown to their maximum height.
These diagrams show the differences of the amount of cohorts (a), the leaf increase rate (b), leaf production rate (c), and leaf loss rate (d) relative to their height. The circles represent the upper and lower crowns, while the squares are used to represent the trees that have reached their maximum height (b-d). The lines are connected showing the beginning (Open Circles) and end (Closed Circles) of the samples that were tested.
Analysis The leaf demography had diversified in the crowns of the various tree species sampled. The life span of the leaf varied between the species that were sampled. In the upper crowns of most of the trees sampled the leaf production and loss rates were higher than in the lower crowns. The results also showed the number of leaf cohorts and the median leaf life span was lower in the upper crowns. The study showed that the turnover rate was faster in the sun leaves than the shade leaves within the crown (Maillette 1982). The number of leaves in the upper crowns increased for most of the trees that have not grown to their maximum height. There was a relation between the rates of the leaf loss and the height of the tree species sampled.
Conclusions I learned from reading about this subject that the leaf turnover is greater in the upper crowns than the lower crowns in a rain forest. The life span of the leaf was longer in the lower crowns than the upper crowns and that more leaves fall from the upper crowns than the lower crowns of the trees.
References Levinson David and Karen Christensen, Editors, 2002, Encyclopedia of Modern Asia Volume 4, p. 1-21 Maillette, L. (1982), Needle demography and growth dynamics of Corsican Pine. Canadian Journal of Botany, 60, p 105-116. Noriyuki Osada, Hiroshi Takeda, Akio Furukawa, and Muhamad Awang; “Leaf Dynamics and Maintenance of Tree Crowns in a Malaysian Rain Forest Stand”; Journal of Ecology (2001); Volume 89; pp. 774 – 782.