Fire and cyclone damage to woody vegetation on the north coast of the Northern Territory,Australia     

D.M.J.S. Bowman  W.J. Panton 《The Australian geographer》1994,25(1):32-35

Tree stem (>2 m tall) mortality was assessed following a late dry‐season wildfire across a seasonally flooded elevation gradient at Workshop Jungle, near Darwin, in the Northern Territory of Australia. For all species combined, dead stems had significantly smaller diameter at breast height (dbh) than living stems. Assessment of tree‐stem damage following a tropical cyclone at Cobourg Peninsula, NT, revealed that damaged stems had significantly greater dbh than undamaged stems for all tree species sampled across a boundary between monsoon rainforest and savanna. A greater proportion of stems were damaged by the cyclone than by the fire (28 per cent as against 18 per cent), although there were considerable between‐community differences in the proportion of damaged stems at the two sites. The fire caused little impact (<10 per cent) on total basal area of three different forest communities on the elevation gradient at Workshop Jungle. The cyclone was found to cause >50 per cent damage to total basal area of three different communities on Cobourg Peninsula. It is suggested that the combination of a cyclone followed by an intense fire in storm debris could potentially destroy a monsoon rainforest through its impact on all tree‐size classes. This may explain why some monsoon rainforests rapidly contracted following Cyclone Tracy that destroyed the city of Darwin on Christmas Day, 1974.  相似文献   

Changes in post world war ii distribution and status of monsoon rainforests in the Darwin area     

William J. Panton 《The Australian geographer》1993,24(2):50-59

Monsoon rainforests in the Darwin area occur as isolated patches ranging in size from 2 to 112 ha. Aerial photographic records over a 45 year period indicate a 60 per cent reduction in the cover of pre‐1945 rainforest. Urban development, cyclone damage, weed invasion and wildfire were identified as the major causes of this contraction. Urban development contributed 40 per cent of the total rainforest loss during this period. Rainforests occurring on dry substrates have been most affected by urban development. Cyclonic storm damage and indirect human affects such as weed invasion and anthropogenic fires continue to disturb the remaining rainforest patches. Although the largest expanses of rainforest presently occur within parks and reserves, providing adequate protection from further urban encroachment, smaller remnants occurring on vacant crown land are vulnerable to changes in land use. As well as the introduction of appropriate legislation, the control of fire and weeds should be given the highest priority by land managers to ensure the stability and long‐term maintenance of this remnant vegetation.  相似文献   

Short-term and seasonal variation in metabolic balance in Liverpool Bay     

Anouska Panton  Claire Mahaffey  Naomi Greenwood  Joanne Hopkins  David Montagnes  Jonathan Sharples 《Ocean Dynamics》2012,62(2):295-306

Regions of freshwater influence (ROFIs) are dynamic areas within the coastal seas that experience cycles of stability driven by density gradients and the spring-neap tidal cycle. As a result, pulses of biological production may occur on a more frequent timescale than the classic seasonal cycle. Net community production (NCP) rates and chlorophyll a concentration are presented from a site within the ROFI of Liverpool Bay and compared to similar measurements made at a site outside the ROFI during 2009. The influence of water column stability on biological production in the ROFI was also investigated using high-frequency observations from a Cefas Smartbuoy. Both sites were autotrophic from spring to autumn before becoming heterotrophic over winter. NCP at the inshore site was estimated to range from 30.8 to 50.4 gC m⁻² year⁻¹. A linear relationship detected between chlorophyll a and NCP from both sites was used to estimate metabolic balance over 1 year at the ROFI site using high-resolution chlorophyll a concentrations from the Smartbuoy but was found to poorly replicate NCP rates compared to those derived from dissolved oxygen fluxes. There was no clear biological response to periods of stratification within the ROFI, and it is proposed that changes in light attenuation in the Liverpool Bay ROFI, driven not only by stratification but also by fluctuations in riverine sediment load, most likely play an important role in controlling phytoplankton growth in this region.  相似文献   

Assessing the spatial and temporal variability of dissolved organic matter in Liverpool Bay using excitation–emission matrix fluorescence and parallel factor analysis     

Youhei?YamashitaEmail author  Anouska?Panton  Claire?Mahaffey  Rudolf?Jaffé 《Ocean Dynamics》2011,61(5):569-579

The spatial and diurnal tidal variability of dissolved organic carbon (DOC) concentrations and the composition of dissolved organic matter (DOM), as evaluated by high-temperature catalytic oxidation and excitation–emission matrix combined with parallel factor analysis (EEM–PARAFAC), respectively, were determined in Liverpool Bay. EEM–PARAFAC modeling resulted in six fluorescent components characterized as terrestrial humic-like (two), microbial humic-like (two), and protein-like (two). The spatial distributions of DOC and the four humic-like components were negatively correlated with salinity in the high-salinity waters observed in this study (30.41–33.75), suggesting that terrestrial DOM was conservatively distributed. The spatial patterns of protein-like components were largely different from those of DOC, humic-like components, and chlorophyll a, suggesting that these distributions were the combined result of production and degradation in the bay in addition to river inputs. These findings suggest that the DOM dynamics in Liverpool Bay are strongly controlled by river-dominated allochthonous DOM inputs with some less significant contributions of autochthonous DOM within the bay. In addition, the temporal variations of DOM associated with the diurnal tidal cycles were determined at one inshore (31.34–32.24 salinity) and one offshore (33.64–33.75 salinity) station in the bay. Negative linear relationships between salinity and DOM characteristics, i.e., DOC, humic-like, and protein-like components, were observed at the inshore station. In contrast, no relationship was observed at the offshore station, suggesting that the export of DOM through rivers and possibly tidal flats have a noticeable influence on DOM concentration and composition up to a relatively elevated salinity of around 33 in Liverpool Bay.  相似文献