Changes In Vegetation Conditions Research Articles

Vegetation information for improved natural resource management in Australia

Up-to-date, reliable information on the type, extent and condition of vegetation is increasingly required at a range of scales for a range of policy, regulation and management purposes. This paper describes the development of national level vegetation information frameworks for mapping vegetation across Australia. Vegetation mapping and monitoring in Australia have historically been the responsibility of state governments. In the late 1980s, the Australian and State and Territory governments developed the National Forest Inventory to facilitate the collection and availability of contemporary, valid and standardised forest data to assist in the planning and management for the conservation and use of Australia's forests. The National Vegetation Information System framework ( ESCAVI, 2003) expanded this concept for compiling vegetation structure and floristic information for entire landscapes. The National Vegetation Information System framework has recently been used to integrate data from a range of sources to provide a whole-of-landscape view of vegetation, including native, non-native and non-vegetation land covers. Map compilation approaches to vegetation assessment provide only one form of information required for policy, regulation or management decisions. Compiling and updating such snapshots of Australia's vegetation cover provide little, if any, information on the condition of the vegetation. Differences between repeated snapshots through time using this approach are often the result of differences in classification approaches or mapping technologies rather than actual changes in the structure and/or floristics of the vegetation. It is argued that efficient assessment of change in vegetation condition requires repeated measurements of condition indicators at the same sites over time. We present a continental forest monitoring framework design concept to address this concern. Issues that need to be addressed relating to monitoring framework data and map-based information are also discussed in the context of adaptive management for improved natural resource management.

Assessment of NDVI Composites Using Merged NOAA-14 and NOAA-15 AVHRR Data

The Advanced Very High Resolution Radiometer (AVHRR) data acquired by the National Oceanic and Atmospheric Administration's (NOAA) satellites provide daily observations of the Earth's surface. While NOAA-14 data from ascending orbits are operationally used for global vegetation monitoring; NOAA-15 data from descending orbits could provide additional daily coverage. The normalized difference vegetation index (NDVI), derived from the solar reflective data, is linked to vegetation condition and plant biomass production on land surfaces. Because a single AVHRR scene is seldom completely cloud-free, maximum value compositing (MVC) of multi-date NDVI data is widely used to minimize cloud contamination. While ten-day composites from NOAA-14 AVHRR data may not be cloud-free; critical short-term changes in vegetation condition may be lost in composites created over longer time periods. AVHRR data of Texas obtained from NOAA-15 (morning satellite) and NOAA-14 (afternoon satellite) were used in our study on the potential benefits of merged morning and afternoon NDVI data sets for crop monitoring. A strong correlation was observed between NOAA-14 and NOAA-15 NDVI data derived from top-of-atmosphere (TOA) reflectance.

Radiometric analysis of SPOT-VEGETATION images for burnt area detection in Northern Australia

Radiometric analysis of SPOT-VEGETATION (VGT) images acquired over Australia was carried out as a basis for the development of an algorithm to map burnt areas in woodland savannas. We analysed the variability of daily ground reflectance and its relationship with illumination and viewing geometry. Finding that the geometrical effects can be parameterised by the phase angle (angle between the illumination and the viewing directions) and the viewing zenith angle (VZA), we fit a simple linear model to the observations. The results show that about 60–70% of the variability in the daily reflectance is caused by geometrical effects. The residual 30–40% of the variability is probably due to changes in vegetation condition, such as senescence, and residual atmospheric contamination. We tested temporal compositing as a practical method of reducing the variability in the reflectance whilst retaining the burnt area signal. We inspected the radiometric and geometrical effects of four different compositing criteria and showed that minimum near infrared (NIR) is the most appropriate for burnt area mapping over the study area. In order to analyse the sensitivity of the VGT spectral bands and derived indices to changes induced by fire, we extracted burnt area spectral signatures for different vegetation types. The persistence of the burnt signal, as observed with each band and index, was analysed. Among the bands, NIR is shown to be the most sensitive to fire occurrence. There is a clear drop in the reflectance immediately after the fire and it remains very low during subsequent weeks. On the other hand, the burnt signal in the short-wave infrared (SWIR) band is showed to be strongly dependent on the vegetation cover type and on the age of the burnt area. Among the indices, the Global Environment Monitoring Index (GEMI) is identified as the most suitable for detecting changes induced by fire on the vegetation cover.

The Use of Landsat Derived Multi‐temporal NDVI to Assess the Impact of the Construction of the Central Pilbara Railway on Vegetation Conditions, Karijini National Park, Western Australia

The Central Pilbara Railway (CPR) was constructed in 1992 by Hamersley Iron Pty Ltd to provide a transport link between Marandoo and the proposed Yandicoogina Mine in the Central Pilbara, Western Australia. The 400 km line connects to the port of Dampier to the huge iron ore resources in the central Pilbara and a section of nearly 100 km of the railway passes through the Karijini National Park. The main area of interest in this study is within this strip and in particular the section 500 metres either side of the railway centreline between Marandoo and the eastern boundary of the park near Juna Downs. This study uses multi‐temporal satellite data to determine the prior status and the impact on vegetation condition from the construction and operation of the CPR. This method was tested using one kilometre subdivisions along and 100 metre segments away from the line within a 500 metre zone around the CPR. It was found that change in vegetation condition is significantly greater closer to the railway centreline than farther away. The significant decrease in vegetation condition occurs only in the 0 to 100m segment, but not beyond and the vegetation decrease may be considered an inevitable result of the CPR. It appears that wild‐fires have the greatest impact on vegetation condition in this region and the impact of the CPR is minimal by comparison.

Burrow Abandonment by Gopher Tortoises in Slash Pine Plantations of the Conecuh National Forest

We investigated burrow dynamics and factors associated with abandonment of burrows hy gopher tortoises (Copherus polyphemus) in mature slash pine (Pinus elliottii) plantations of the Conecuh National Forest (CNF) in southcentral Alabama. Our objectives were to determine how frequently gopher tortoises abandoned burrows in pine plantations, if burrow abandonment was associated with changes in vegetation conditions, and how rapidly these changes occurred. Burrow survey data collected over 5 years indicated gopher tortoises abandoned burrows at an average rate of 22%/year. We believe burrow abandonment occurred frequently in pine plantations, primarily in association with a change in overstory structure that shaded active burrows. Abandoned gopher tortoise burrows had greater total basal area (P = 0.012), hardwood basal area (P = 0.016), and tree density (P = 0.003) than did active burrows. There was a significant positive correlation between age of active gopher tortoise burrows and canopy closure (total basal area: r 2 = 0.19, P = 0.007; pine basal area: r 2 = 0.20, P = 0.004; tree density: r 2 = 0.14, P = 0.018). We estimated that overstory conditions at newly active burrows changed to those observed at abandoned burrows in only 5-7 years. Increases in total basal area to 70 m 2 /ha and tree density to 1,400 trees/ha were associated with burrow abandonment. Active burrows had greater total plant cover (P = 0.009) and grass cover (P = 0.016) than did abandoned burrows. However, we found no correlation between age of active burrows and structure and composition of ground cover vegetation (r 2 values ranged from 0.00 to 0.07; P-values ranged from 0.096 to 0.987). Stand thinning to a basal area of 30 m 2 /ha and prescribed growing-season burns should improve habitat quality, thereby increasing burrow fidelity of gopher tortoises.

An analysis of the 1984 locust plague in Australia using multitemporal landsat multispectral data and a simulation model of locust development

An analysis of the 1984 locust ( Chortoicetes terminifera (Walker)) plague in Australia was undertaken to determine its source region using a simulation model of locust development and whether using appropriately enhanced satellite data, the individual areas that were suitable for locust breeding could be detected within this region. The origin of the 1984 plague was found to be in the Channel Country of south west Queensland, and satellite data indicated that there were localised areas suitable for locust breeding at the appropriate time other than those detected by ground survey. It is concluded that it isfeasible to use satellite data on an operational basis to detect areas suitable for locust breeding by monitoring changes in vegetation condition. Using the locust simulation model, the course of breeding and possible plague development can then be forecast, and ground surveys directed to the areas of interest at the approximate time.