Land Forest Research Articles

Potential and limits of NOAA-AVHRR temporal composite data for phenology and water stress monitoring of temperate forest ecosystems

We focussed on the potential and limits of NOAA-AVHRR 5-day composite data for monitoring the phenology and the fluxes of temperate forests at regional scale. The spatio-temporal variability ofkm2 Normalised Difference Vegetation Index (NDVI) was large, and primary varied with the deciduous/ coniferous mixture. It could provide the phenological cycle of deciduous ecosystems. For the large coniferous Landes forest, it characterised the different ecotypes, and was sensitive to land use (age of the pine stands) and understorey vegetation. Relationships between NDVI, TS and rainfall confirmed the ability of km2 thermal infrared data to infer the water status of this forest.

NOAA/AVHRR Bidirectional Reflectance: Modeling and Application for the Monitoring of a Temperate Forest

In this article, bidirectional effects on NOAA/AVHRR short wavelength data were analyzed for the regional monitoring of the temperate pine ( Pinus pinaster) Landes forest. Because of differences in soil hydrologic characteristics, the forest is described by five ecotypes, which determine the understorey type and the potential for pine growth. Bidirectional visible and near-infrared reflectances were analyzed from a daily NOAA-11 archive through years 1990–1994 using the bidirectional reflectance function model of Rahman. Rahman’s model fits 72% of AVHRR visible reflectance, and 93% of AVHRR near-infrared reflectance. A typical example shows that 1) in the principal plane, the ratio of hot spot to forward scatter reflectance is 2.9 and 2.1 for visible and near-infrared, respectively, 2) bidirectional effects become negligible across the principal plane, and 3) NDVI shows a shape opposite to that of reflectances. After normalization, the seasonal dynamics of AVHRR reflectances were related to the phenological cycle of pine trees and understorey vegetation. Visible reflectance drops earlier on coastal than on inland sites, due to an advance in the onset of pine growth. Near-infrared reflectance increases in summer for annual understorey, and remains steady for evergreen understorey. Differences in the seasonal dynamics of NDVI consequently characterize each Landes ecotype. From the modeled reflectances, we estimated the seasonal dynamics of visible and near-infrared albedo. We calculated the solar albedo by a combination of the last two. The visible albedo displays a seasonal dynamic similar to that of normalized visible reflectance. The solar albedo was found constant and around 12.7% on each ecotype. In both cases, albedo strongly increases with solar zenith angle, consistent with ground measurements. These results clearly show the usefulness of coarse spatial resolution satellite data for the regional monitoring and modeling of temperate coniferous ecosystems.

Relating germination dynamics of Melampsora pinitorqua teliospores to temperature and rainfall during overwintering

SummaryThe influence of overwintering conditions on the dynamics of Melampsora pinitorqua teliospore germination in spring was assessed in the Landes forest (south‐western France), over 3 years. January accumulated temperature was the variable most strongly linked to the date of optimum germinability (JDOG), in a negative direction. A linear regression using accumulated degree‐days and number of rainy days in January accounted for nearly 70% of overall variation in JDOG. Accumulated temperature from October 1 and January 1 to the date of optimum germinability showed lower coefficients of variation than JDOG. The best predictions of JDOG in an independent data set were obtained by using the accumulated temperature from January 1 to the date of optimum germinability or a linear regression based on accumulated temperature in January. The mean square root error of prediction was approximately 5 days. The ecological significance of the temperature‐dependent model is discussed in relation to the synchronization of rust and pine phenologies.

High-Resolution Simulation of Surface and Turbulent Fluxes during HAPEX-MOBILHY

The newly developed nonhydrostatic model MESO-NH, in which the surface scheme Interactions Soil–Biosphere–Atmosphere has been incorporated, is used in this study to assess the impact of increasing the horizontal resolution from 10 km to 1 km on the simulation of surface and turbulent fluxes for the 16 June 1986 case of HAPEX-MOBILHY, a field experiment that took place in southwestern France. Except for a slight deterioration over the cultivated areas surrounding the Landes forest (caused by an inconsistency between the soil texture fields at 10 and 1 km), the simulation of the surface fluxes of sensible and latent heat is generally improved by the increase of horizontal resolution. The contrast of the sensible heat fluxes between the Landes forest and the surrounding cultures is well captured in both 10-km and 1-km runs, but the spatial variability of these fluxes is better represented in the high-resolution results. An oasis-type effect over the larger clearings of the Landes forest is even produced by the model, as was observed. For the 1-km simulation, the comparison of the turbulent fluxes against observations has to include both the grid-scale fluxes resulting from resolved larger eddies within the well-mixed layer, as well as subgrid-scale (i.e., parameterized) fluxes. (At 10-km resolution, all turbulent fluxes are parameterized.) The greater contributions of the grid-scale component are found over the forest, where the larger eddies are more vigorous due to stronger sensible heat fluxes at the surface. For sensible and latent heat fluxes, the grid-scale component is particularly important in the middle of the mixed layer, whereas for turbulent kinetic energy this component is greater near the bottom and top of the mixed layer. In general, the increase of horizontal resolution does not improve significantly the simulation of the turbulent fluxes. Thus, the use of such an intermediate horizontal resolution (i.e., 1 km), lying between that typically used in large-eddy simulation models (<200 m) and that of mesoscale models (>few kilometers), is questionable, even though this resolution is probably optimal for simulating surface fluxes, since it is roughly the same as the resolution of the soil and vegetation databases.

Mapping and monitoring prawn farming areas through remote sensing techniques

Coastal ecosystem is complex, sensitive and is subject to the influences of nature as well as human interferences. In recent years the prawn farming has increased significantly in the coastal areas of Andhra Pradesh, India, due to great demand in the export market at the coast of agricultural areas and mangrove forests which are essential for the coastal ecological balance. Hence, a study was carried out with the objective of mapping and monitoring the area under prawn farming and mangroves using multitemporal remotely sensed data along Krishna delta of Guntur and Krishna districts of Andhra Pradesh. Remotely sensed data from Landsat‐MSS pertaining to 1973, 1985 and 1990 years and Indian Remote Sensing Satellite‐1A (IRS‐1A) of 1992 are used for the study. The methodology adopted is digital analysis of multitemporal data. The study revealed that during 1985 to 1992 period the area under prawn farming increased significantly. Initially prawn cultivation started on a smaller scale on saline waste lands along the coast. Later due to commercialization of prawn culture, its cultivation has been extended into agricultural lands and mangrove forest.

The relative merits of surface layer and bulk similarity formulations for surface shear stress

Application of the bulk similarity formulation to the atmospheric boundary layer (ABL) requires the adoption of an external wind velocity and temperature scale. Recent versions of this approach have made use of the average wind speed and average temperature over the outer region or mixed layer of the ABL. The method is applied herein with wind profile data measured over the Landes forest in southwestern France to estimate the regional surface shear stress under unstable conditions. It is found that these estimates can be as reliable as those obtainable with Monin‐Obukhov similarity of the atmospheric surface layer.

Polarimetric observation of forest cover in radar remote sensing

In this paper, and from the received waves, we investigate a number of Polarimetric radar techniques to characterize the polarization response of forest cover, using the example of the Landes Forest. Magnitude, as well as phase difference and amplitude ratios between the Polarimetrie channels, which are closely related to the texture of the scene, offer reliable means for data characterization and discrimination purposes. The statistical properties of high resolution Polarimetrie sar are investigated, using the K distribution to model the received amplitude of each area selected. This distribution is derived with a parameter, a, which is closely related to the heterogeneity of the ground cover, and thus provides a good tool for discriminating among different regions. From the Stokes matrix, the co- and crosspola-rized signatures are constructed, for both clear cut and full-grown tree regions, in order to identify the predominant scattering mechanisms contributing to total measured backscatter.

Estimation of subpixel vegetation density of natural regions using satellite multispectral imagery

A procedure is presented for estimating the subpixel fractional canopy density of natural or undisturbed semivegetated regions on a pixel-by-pixel basis using one satellite multispectral image and a physical modeling approach. The method involves applying a model of the bulk, nondimensional plant geometry combined with a simple model of canopy reflectance and transmittance to the red and near-infrared reflectance space of the atmospherically corrected satellite image. Shadow effects are parameterized assuming Poisson-distributed and geometrically similar plant canopies. The method is applied to the estimation of fractional cover and leaf area index, using Landsat thematic mapper imagery, of two physiologically different plant communities. The first is the Landes Forest, a coniferous region in south central France, during the June 1986 HAPEX-Mobilhy Experiment. The second is the semiarid Walnut Gulch basin of southeast Arizona that contains predominantly shrubs and grasses, during the June 1990 MONSOON Experiment. The procedure offers a physically based alternative to empirical vegetation indices for estimating regionally variable canopy densities of natural, homogeneous systems with little or no ground truth.

Chiefs, Boundaries, and Sacred Woodlands: Early Nationalism and the Defeat of Colonial Conservationism in the Gold Coast and Nigeria, 1870-1916

he main aim of this essay is to make a tentative assessment of some of the attempts made by the British colonial authorities to introduce forest conservation programs into Anglophone West Africa, and to sketch out the nature of some of the more elitist indigenous responses to those attempts. In the course of the essay we also aim to characterize the changing emphases and fashions of conservationism in West Africa and make some brief comparative remarks about contemporary developments in other parts of the British Empire. The story of colonial conservation in West Africa was inextricably bound up with the developing tension between two entirely different agendas of power, one indigenous and the other governmental, within which the state attempted to assert its own notions of environmental control and land-use planning, reflecting both international changes in conservation thinking as well as an empirical and institutional learning process on the part of the local colonial apparatus. Simultaneously the indigenous populations, or at least their leaders, learnt increasingly to adjust to the weaknesses of the colonial state as specifically manifested in an environmental policy, seeking eventually to manipulate the agendas and mechanisms of colonial conservation to their advantage, often with some success. This essay, then, sets out quite deliberately to question the assumption engendered in some quarters that colonial conservation was, throughout the imperial context, a vigorous and militarized instrument of colonial oppression.2 Certainly, in British West Africa this was far from the case. On the contrary, the evidence indicates that, in the context of Western economic penetration, the general pattern of land use change and forest survival was dictated far less by the colonial state than by indigenous political interest groups in close alliance with the interests of metropolitan capital. This analysis actually corresponds with existing and highly insightful research by economic anthropologists.3 To a greater extent than in other parts of the colonial world, conservation in West Africa was affected by the distinctive conditions of indirect rule and local autonomy. Far from succeeding in establishing an environmental hegemony, the conservation propagandists of the colonial state found themselves, from the out-

An assessment of canopy chemistry with AVIRIS—a case study in the Landes Forest, South-west France

Abstract The capability of airborne (AVIRIS) and laboratory spectrometry was investigated for assessing the chemical composition of foliar elements of a pine forest (The Landes, SW France). Simultaneously with AVIRIS acquisition, an atmospheric profile was carried out, and the forest vegetation was sampled for chemical analyses and laboratory spectral measurements. Predictive relations between concentrations of nitrogen (r=97 per cent), lignin (r = 89 per cent) and cellulose ( = 83 per cent) and reflectances of pre-treated pine needles were determined through stepwise regression analyses. A methodology was designed to assess their extrapolation to remotely acquired spectrometric data: (1) geometric and atmospheric corrections, (2) registration within a biophysical data base (e.g. LAI, biomass), and (3) comparative statistical analysis of laboratory and airborne spectrometric information. The application of laboratory derived relationships led to relatively large correlations for nitrogen (74 per cent) and...

Hunting pressure on chimpanzees and gorillas in the Motaba River area, northeastern Congo

An extensive survey was conducted in the Motaba River Area in north­ eastern Congo. It was based on interviews and line transect surveys. The following results were obtained: (1) Both chimpanzees and gorillas occur throughout this area. (2) The den­ sities of both species decrease from the upper toward the lower streams, and also from in­ land forests to villages. (3) Overall densities are estimated at 0.3 chimpanzees per km2 and 0.2 gorillas per km 2• (4) Hunting of apes for meat occurs in every part of the area. !\lost resident people are willing to eat ape meat, and about half of them have a chance to eat it in a year. (5) Hunting pressures on apes are estimated at 0.020 chimpanzees and 0.010 gorillas per km 2 per year. These results strongly suggest that the survival of both species is seriously threatened by local hunting. The threat is expected to increase with human population growth and with forthcoming forest exploitation in northeastern Congo.

Retrieval of forest biomass from SAR data

Abstract In recent years, there has been an increasing interest in the use of radar data for observations of forest ecosystems. In particular, it was shown that the intensity of SAR images at L band was proportional to the forest aboveground biomass. More recently, the analysis of NASA/ JPL SAR data over the Landes forest “south-west France” revealed strong correlation between P-band backscatter and biomass of pine trees and related characteristics “tree age, height, diameter”. Also, similar relations have been obtained on two different forests “maritime pine at Landes forest, France, and loblolly pine at Duke forest, U.S.A.”. This paper presents a step further in the understanding of the observations. using theoretical modelling applied to calibrated SAR data to explain the radar backscatter from the forest canopy under study. The study is presented at P band, which was found to be an optimal frequency band for forest observations. It was found that the H H return is physically related to both trunk and crown biomass, whereas VV and particularly HV returns are linked to crown biomass. Through allometric equations, relations between radar backscatter intensities and most of the forest characteristics can thus be explained. The validated model has been used in a next step to simulate a diversity of forest and observation conditions. The results have been used for a preliminary assessment of the possibility of inverting SAR data into forest biomass.

The Landes experiment: Monoterpenes emitted from the maritime pine

The emissions of monoterpenes from maritime pine (Pinus pinaster Ait.) were recorded during a measurement campaign in the Landes forest. Analyses were carried out with an automatic sampling device. The emission rates were determined via the enclosure method. Daily cycles of atmospheric concentrations of α and β‐pinene, Δ3‐carene, and limonene were recorded. The concentrations measured for all terpenes were seen to vary within the range of 0.2 to 3.4 ppbV, exhibiting minimum values at daytime and maximum at night. The daily cycles of emission rates exhibit a maximum diurnal value of 237 ng g−1 h−1 and a minimum nocturnal value of 9 ng g−1 h−1. The emission rates recorded for α and β‐pinene were much higher than those corresponding to other monoterpenes. The average values are 70 μg m−2 h−1 for α and β‐pinene and 30 μg m−2 h−1 for other monoterpenes. The emission rates of terpenic compounds were correlated with temperature, light intensity, vapor pressure, and with the product of the relative monoterpene amount within the plant and the corresponding vapor pressure.

Sustainable Development of Forest Lands and Joint Forest Management in India

Sustainable Development of Forest Lands and Joint Forest Management in India

Imputed prices of greenhouse gases and land forests

Modelisation economique du cout de l'effet de serre et de son impact sur la foret. Analyse de l'impact de la taxation sur les emissions de CO 2

Parameterization of Surface Heat Fluxes above Forest with Satellite Thermal Sensing and Boundary-Layer Soundings

Abstract Satellite-derived surface temperature measurements can be used in conjunction with temperature and wind soundings in the boundary layer to determine the surface sensible heat flux from forests at the regional scale. The underlying formulation is derived on the basis of similarity principles applied to the unstable turbulent boundary layer in which the scalar roughness for sensible heat is determined by calibration. This is illustrated herein with data acquired during the HAPEX–MOBILHY (Hydrologic Atmospheric Pilot Experiment-Modelisation du Bilan Hydrique), which was conducted in the spring and summer of 1986 over a 100-km × 100-km square in southwestern France. The northwest third of the area is covered by the Landes forest. The surface temperatures for a 25-km × 25-km area in this forested region were determined from the NOAA-9 Advanced Very High Resolution Radiometer (AVHRR) channels 4 and 5. Atmospheric collections were applied with LOWTRAN-7 and measured atmospheric profiles, as well as with...

Analysis of atmospheric ozone measurements over a pine forest

Vertical and horizontal profiles of ozone concentration have been measured within the atmospheric boundary layer over the pine forest located in the southwest of France (Landes Forest). Evidence for an ozone depletion in lower layers is obtained from the analysis of vertical profiles recorded at the end of the night. In terms of deposition at the upper canopy level, this corresponds to a disappearance rate ranging between 0.2 and 0.5 cm s −1. The horizontal profiles obtained at midday reveal that ozone vanishes at a rate of the order of 5 × 10 −5 ppb m −1 when air mass moving in the advection direction passes over the forested area. These results are consistent with those obtained by numeric simulation in the case of low emission rates of nitrogen oxides. On the basis of these measurements, the expression of the ozone budget within the atmospheric boundary layer is discussed and compared with the data obtained from the simulation study.

Remote sensing application to study the coastal shrimp farming area in Bangladesh

Abstract Data from black and white aerial photographs (1974–75), Infrared colour (IRC) aerial photographs (1983–84), Landsat Multispectral Scanner (MSS) of 1984 and Landsat Thematic Mapper (TM) of 1987–88 are used to locate and measure the existing coastal shrimp fanning areas of selected sites and finally to find out the sequential changes in time perspective in order to explain spatial changes for better planning and scientific management. The shrimp farming and mangrove forest areas are identified and located by remote sensing techniques. The Landsat (MSS & TM) data are used to delineate the surface feature of the coastal area. Infrared colour (IRC) aerial photographs provided most revealing information. Sequential aerial photographs provided information on change in time and places. This study reveals that the shrimp farming areas are expanding through destruction of the mangrove forest of Chokoria Sundarban and agricultural land of Rampai and Paikgachha area. For scientific development of the coastal...

The golden-backed uacari on the upper Rio Negro, Brazil

The golden-backed uacari Cacajao melanocephalus ouakary is one of South America's least-known monkeys. Listed as Vulnerable by the IUCN, it lives in remote areas of north-western Amazonia, as yet relatively unaffected by ecologically disruptive economic and technological activities. It inhabits swamp forests on black-water rivers during the main fruiting season and may move to dry land forests at other times of the year. The authors' survey showed that the animal was still common in the vicinity of subsistence communities, but is subject to heavy hunting pressure. Although the political situation in the area and the region's remoteness make it difficult to implement conservation plans, the authors propose a possible basis for a conservation plan for the golden-backed uacari and its habitat.

Community forestry and its implications for Northern Ontario

Community forestry is becoming an increasingly important policy issue for provincial governments in Canada. Many single-industry communities in the northern parts of the provinces, surrounded as they are by forests, are looking to forest resources for possible economic diversification and stability. At the same time as there is increasing interest, there is little understanding about what community forestry could and should be for communities surrounded by Crown land forests. This paper looks at some definitions and dimensions of community forestry, as well as reviewing briefly some experiences with it. We examine various ways in which community forestry might be different from provincial government forestry and industrial forestry, and reflect on whether community forestry could lead to improvements in forest management. We conclude with some thoughts on potential future directions for community forestry in Ontario. Key words: community forestry. Crown land forests, single-industry communities, land tenure, local involvement, economic stability, Northern Ontario