Domingos Lopes

Accuracy of remote sensing data versus other sources of information for estimating net primary production in Eucalyptus globulus Labill. and Pinus pinaster Ait. ecosystems in Portugal

Net primary production (NPP) quantifies vegetation growth. It reflects the impact of biotic and abiotic factors over an ecosystem and is an important ecological variable for monitoring the impact of human activity on ecosystems. Though conceptually simple, NPP can be very difficult to measure accurately. In this paper, different temporal and spatial NPP products are compared, improving our understanding of the accuracy of these methods for measuring NPP in small forested areas of Eucalyptus globulus Labill. and Pinus pinaster Ait. stands. The Moderate-Resolution Imaging Spectroradiometer (MODIS) NPP products were compared with NPP values obtained from FOREST-BGC (a well-known ecophysiological model) and field measurements. The paper also examines the possibility of estimating the leaf area index (LAI), a key FOREST-BGC input, using remote sensing techniques. The results indicate that the most accurate estimates were achieved using the FOREST-BGC model, which is normally applied at the stand level. Since LAI can be estimated from remotely sensed data, this ecophysiological model may now be regarded as suitable for use at the regional and global scales. The results also showed that, although average NPP values are similar to field measurements, MODIS NPP products are inefficient for identifying extreme NPP values.

Data fusion for high spatial resolution LAI estimation

Leaf Area Index (LAI) is a critical variable for forest management. It is difficult to obtain accurate LAI estimations of high spatial resolution over large areas. Local estimations can be obtained from in situ field measurements. Extrapolation of local measurements is prone to error. Remote sensing LAI estimation products, such as the one provided by MODIS are of very low resolution and subject to criticism in recent validation works. Forest management requires increasingly high resolution estimations of LAI. We propose a data fusion process for high spatial resolution estimation of the LAI over a large area, combining several heterogeneous information sources: field sampled data, elevation data and remote sensing data. The process makes use of spatial interpolation techniques. We follow a hybrid validation approach that combines the conventional prediction error measures with a spatial validation based on image segmentation. We obtain encouraging results of this information fusion process on data from a forest area in the north of Portugal.

Evaluation of the Climate Change Impact on the Productivity of Portuguese Pine Ecosystems Using the Forest-BGC Model

The growth, survival and geographical distribution of plants are determined by climate, particularly temperature and precipitation. The actual tendency indicates a global climate change with direct negative impact on terrestrial ecosystems. Estimation of net primary production (NPP) allows a prediction of the impact of climate change on ecosystems. Studies on climate and dynamic modelling of stand development are being carried by the scientific community all over the world in order to assess the effects of global climate change. There is the question if that spatial scale of analysis is not overlooking local or regional information that can be important for smaller communities. The object of this study is to identify if the local scale is appropriate to analyse the impact of the climate change on the productivity of the local forest ecosystems. The Forest-BGC model was used to estimate the NPP in pine (Pinus pinaster Aiton) pure and mixed forest based on climate evolution scenarios derived from the analysis of past available climate series and its evolutionary trends for the Tras-os-Montes region, north of Portugal, which has three distinct climatic zones. We concluded that for the study areas temperature is the key variable influencing NPP under climate change scenarios.

Alvão-Marão: Preserving Important Natural Resources in a Mountain Range

The Alvao-Marao cordillera links the Natura 2000 Network and includes the mountains of Alvao and Marao. These are part of a system of mountains with a north-south orientation, namely Larouco, Alvao, Marao and Meadas. The Alvao-Marao mountain range is bordered to the west by the Tâmega River and to the east by the Corgo River. Its importance has increased since it was integrated into the Natura 2000 Network, although the Portuguese government had previously noted the importance of Alvao-Marao in terms of biodiversity, as will be reported later.