碩士 / 國立臺灣師範大學 / 生命科學系 / 106 / Leaf area index (LAI) is an important ecological parameter. Leaf area affects various important ecological processes, such as primary productivity, energy flow, and water cycle. Therefore, measuring LAI and its dynamics help our understanding of the features, structure, function, recovery, and resistance of ecosystems.
Direct and indirect methods are widely used to measure LAI. Direct methods are accurate but are time consuming and spatially limited. With some inherent assumptions, indirect methods estimate LAI through light transmittance or gap fractions and can be operated at broad scales. However, the deviation from the assumptions varies among tree species or ecosystems. Thus, it is important to test the validity of indirect methods.
Numerous studies have tested the validity of plant canopy analyzer (PCA) and hemispherical photography in estimating LAI. However, most of the studies were conducted in temperate region, which has very different forest composition from those in the subtropics. Thus, it remains unclear if the results of these studies can be directly applied to subtropical Taiwan.
This study use direct method - litter trap to estimate the LAI and compare it to the estimates made by PCA and hemispherical photography and thereby test their accuracy. How the two types of equipment perform at different leaf area levels area are also important in the applications. Thus we measure leaf area index in four different forests from March to July, the growing season, in Taiwan to examine the viability of the two types of equipment by checking the trend of increase in leaf area estimated by PCA and hemispherical photography.
The result shows that in areas with high leaf area such as low and mid altitude forest in Taiwan, both types of equipment tend to underestimate LAI. However, compare to hemispherical photography, PCA is more accurate and can better capture the temporal changes in LAI. In contrast, in areas with low leaf area, the performance of hemispherical photography is better, although it overestimated LAI.
In addition to the patterns described above, the performance of PCA and hemispherical photography is although affected by weather, the location of positioning of the equipment and the personal bias of analyzers. Researchers should be aware of the limitation of both types of equipment in their application.
| Identifer | oai:union.ndltd.org:TW/106NTNU5112014 |
| Creators | Hou, Yan-Yu, 侯彥宇 |
| Contributors | Lin, Teng-Chiu, 林登秋 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 58 |
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