Patterns of forest biomass and litterfall at different scales in Taiwan
Date Issued
2015
Date
2015
Author(s)
Wang, Hsueh-Ching
Abstract
Forest ecosystem is the major carbon pool in terrestrial biosphere, and understanding dynamics of forest carbon stock and flux is important for carbon budget. This dissertation used remotely sensed imagery to evaluate the pattern of biomass and litterfall in subtropical/tropical forests. The dynamic global vegetation model was also included to model typhoon-induced defoliation and carbon cycle under scenarios of typhoon intensity and frequency. Firstly, this dissertation extracts canopy areas from a high spatial resolution QuickBird image to assess the patterns of carbon stock across topographical gradients and the edge effect in a Chilan montane cloud forest. Mean ( s.d.) carbon per individual was 138 118 kgC with an estimated site carbon density of 119.3 MgC ha-1 in a false cypress (Chamaecyparis obtusa var. formosana, CHFO) cloud forest. The negative trends of temperature and solar radiation along the elevation gradient were observed, and slope played a crucial role in varying CHFO canopy area. The findings suggest that topographical heterogeneity may alter the spatial patterns of nutrients and bioclimate that influence the structure of the vegetation. Secondly, time-series MODIS LST- (land surface temperature) and PV-derived (photosynthetically active vegetation cover) metrics were used to derive litterfall. The mean annual litterfall was 5.1 ± 1.2 Mg ha-1 yr-1 in Taiwan montane forests. The temporal dynamics of the litterfall revealed that typhoons and consecutive drought events might be important for temporal variability of litterfall. The elevation gradient and aspects were critical to dominate spatial patterns of litterfall. Thirdly, a wind built-in function with wind speed, temperature and precipitation variables was developed in a dynamic global vegetation model Hybrid v4.2 to simulate typhoon-induced leaf litter in the Fushan experimental forest. The modeled and observed leaf litter was significant correlation (r2 = 0.33, p < 0.001) with moderate underestimation (15.6%). The leaf litter, leaf area index (LAI), total biomass, gross primary production (GPP) and net primary production (NPP) were higher in non-typhoon environment than in typhoon-affected environment. The raises of typhoon intensity and frequency would increase leaf litter and soil respiration resulting in the decreases of LAI, biomass, GPP and NPP. If the substantial defoliation from more intense or frequent typhoon might affect regional carbon budget at long-term time scale. Overall, using satellite images and a dynamic global vegetation model to monitor spatial and temporal patterns of living biomass, litterfall and carbon flux may facilitate monitoring and predicting of carbon budget and perturbations in forest ecosystems.
Subjects
carbon cycle
biomass
litterfall
defoliation
remote sensing
model
typhoon
disturbance
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-104-D99228002-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):451c21a2cf886cb66442b522460f9c4b