Levels Of Forest Disturbance Research Articles

Assessing tropical lowland forest disturbance using plant morphological and ecological attributes

Secondary forests now play a vital role in the conservation of tree species diversity in Southeast Asia because of the continuing fragmentation and decreasing extent of undisturbed forests in this region. To be able to determine the structural and compositional integrity of secondary forests, a ground based rapid assessment method was developed. For this purpose species from the genera Macaranga and Mallotus (Euphorbiaceae) were classified into early and late successional species based on morphological characters that were found to correlate with the light establishment preferences of these species. These characters were wood density (found to be significantly negatively correlated with light establishment preference), seed size (also significantly negatively correlated with light establishment preference), and leaf shape (the leaf length/width ratio was significantly negatively correlated with light establishment preference). Based on this species classification, number of pioneers and non-pioneers could be determined in 71 plots of 0.3 ha, covering 11 common forest disturbance types in Southeast Asia. Three main patterns were detected with this methodology: (1) pioneer and non-pioneer densities were significantly correlated with the forest disturbance level; (2) pioneer densities decreased with time since disturbance; (3) pioneer densities increased with repeated disturbance. A sample size test indicated that forest disturbance in general, and the differences between the major disturbance types could be significantly determined with a minimum of five plots of 0.3 ha. An interactive version of the developed forest disturbance methodology is available at http://www.nationaalherbarium.nl/MacMalBorneo/index.htm.

Forest moth taxa as indicators of lepidopteran richness and habitat disturbance: a preliminary assessment

The conservation of hyperdiverse taxa such as arthropods may prove frustrating for land managers who lack the taxonomic expertise to perform species-level identifications. Therefore, interest has turned towards selecting indicator taxa that can be monitored as surrogates for detecting changes in entire communities. In this study, we examined whether several moth families or subfamilies were significant indicators of lepidopteran species richness and habitat disturbance in Eastern deciduous forests of North America. We screened moth families to identify assemblages that are easily sampled and primarily comprised of species that can be identified by non-experts. Using existing field data collected over 3 years, we tested four taxa that met our initial requirements with regard to their performance as an indicator of total observed lepidopteran species richness and levels of forest disturbance. We determined that the Arctiidae and Notodontidae hold promise as potential indicator taxa in Eastern deciduous forests. The Arctiidae functioned best as an indicator of moth species richness, while the Notodontidae performed best as a coarse-scale disturbance indicator. Additional research will be required, however, before species within either family have practical significance as tools for assessing forest condition.

Same Forest, Different Countries

SUMMARY In the Gran Sabana of Venezuela and the North Rupununi Savannah of Guyana, protected areas have been established primarily for purposes of conservation. However, both Canaima National Park in Venezuela and the Iwokrama International Centre for Rainforest Conservation and Development in Guyana are multiple use areas where a variety of resource use occurs and/or is planned. Shifting cultivation by the indigenous population is currently both the most common use of the forest and the use of longest duration in both areas. Surveys were conducted of paired primary and secondary forests in order to test the hypothesis that traditional, dispersed shifting cultivation with long fallows and no post-cultivation disturbance is sustainable, resulting in the eventual re-establishment of diverse secondary forests. Interviews and observations of agricultural practices and surveys of agricultural fields were conducted to determine the contemporary forest use practices and the extent to which traditional practices have changed. Results indicate that even dispersed, long fallow shifting cultivation requires careful management and several disturbance-free decades before diversity levels in secondary forests approach those in old growth. Further, that the process of integration and cultural “development” has destabilized this traditionally sustainable system in some areas. A central assumption of the paper is that with an understanding of the impacts of shifting cultivation and of the conditions under which it is sustainable, informed decisions about protected area management can be made. The data provide valuable and hitherto missing information on the levels of forest disturbance that can be sustained in the two protected areas while still meeting conservation goals.

Structure of a bat assemblage (Mammalia, Chiroptera) in Serra do Caraça Reserve, South-east Brazil

The Serra do Caraca Reserve is situated in the southern portion of the Espinhaco Mountain Range, and contains areas of campos de altitude, cerrado and atlantic forest. This study had as its objective the registering of the bats species that occur in the reserve. The data collection was carried out in one year through monthly samplings, using mist nets set on trails, and also through hand capture. A total of 246 individuals were collected (0.72 bats/net-hour), distributed across 15 species, belonging to the families Phyllostomidae (83.0%; nine species), Vespertilionidae (12.5%; three species) and Molossidae (4.5%; three species). The most abundant species were Sturnira lilium (E. Geoffroy, 1810) (n = 121, 60.5%), Myotis nigricans (Schinz, 1821) (n = 21, 10.5%) and Platyrrhinus lineatus (E. Geoffroy, 1810) (n = 10, 5.0%), and less represented were Lasiurus blossevilli (Lesson y Garnot, 1826) (n = 2, 1.0%), Eumops perotis (Schinz, 1821) (n = 2, 1.0%) e Vampyressa pusilla (Wagner, 1843) (n = 1, 0.5%). The richness of species found and the non-occurrence of phyllostomines in the reserve could be indicative of some level of forest disturbance.

The diversity and abundance of ants in relation to forest disturbance and plantation establishment in southern Cameroon

Summary Tropical biodiversity is seriously threatened by deforestation but few studies have quantified its impact. We aimed to measure the impact of forest clearance and different methods of establishing Terminalia ivorensis (Combretaceae) forest plantations on the abundance, richness and composition of ants, the most abundant group of arthropods in tropical forest canopies, in the Mblamayo Forest Reserve in Cameroon. For canopy ants, we quantified the effects of different methods of plantation establishment by sampling two sets of plots subjected to complete clearance, partial mechanical clearance and partial manual clearance relative to uncleared forest reference plots. For leaf‐litter ants, we quantified the impacts of different levels of forest disturbance along a gradient from near primary forest to complete forest clearance. A total of 97 ant species was recorded from the canopy (from approximately 48 500 individuals), at an average of 213 (±45) ants m−2. Jack‐knife estimates of species richness showed that at one site, Bilik, 87% more species occurred in the partial manual clearance plot than the complete clearance plot, with the partial mechanical clearance plot intermediate. At the other site, Ebogo, ant richness did not vary between treatments. Ants were 20 times more abundant in the partial manual clearance plot in Ebogo than the partial manual clearance plot in Bilik, largely due to a numerous Technomyrmex species that might have reduced ant richness on this plot. Cluster analysis of the similarities in ant species composition between plots, calculated by the Morisita index, showed that site and treatment affected species composition. Neither treatment nor site affected the relative number of species in different nesting categories. A total of 111 ant species (from 3650 individuals) was recorded from the leaf litter, at an average of 52 (±4·6) ants m−2. Species numbers were greatest in the two partial clearance plots in Ebogo (52–53 species), lowest in the two complete clearance plots (37), and intermediate and most variable in the three uncleared forest plots (40–52). Cluster analysis showed that species composition was not affected by treatment, while neither treatment nor site affected the relative number of ant species in different feeding categories. Despite some local effects by dominant species, our results support the view that deforestation can reduce arthropod species richness. This study is unique in showing that reforestation methods (using a single tree species) can have a marked effect on arthropod species richness and composition. Specifically, it reveals that ant species richness can be greater in plantations established after partial manual clearance than complete clearance.

Mapping forest‐cover disturbances in Papua New Guinea with AVHRR data

Abstract. Land management and land‐use planning in a forested country such as Papua New Guinea, which is subject to various anthropogenic pressures, requires an accurate mapping of forest‐cover disturbances. The central hypothesis of this study was that remote sensing indicators of forest‐cover conditions can be used to measure and map the impact of long‐term forest‐cover disturbances. This was tested with single year NOAA's Advanced Very‐High Resolution Radiometer sensor (AVHRR) data at 1.1 km resolution. First, an ordinal scale of forest‐cover disturbance was defined from field observations, a set of thematic maps and high spatial resolution satellite sensor data. Secondly, we analysed the relationship between the forest‐cover disturbance scale and several biophysical indicators derived from AVHRR data at two seasons. Thirdly, a statistical analysis identified the optimal combination of biophysical indicators and observation dates to discriminate between the forest disturbance levels defined previously. A forest‐cover disturbance map was then produced over part of Papua New Guinea. Finally, a regionalization of the study area in terms of aggregate degree of disturbance was produced and the spatial patterns of forest disturbances were interpreted for each region in terms of broad processes of forest‐cover change. The overall accuracy of the forest‐cover disturbance map was 79%. Nine regions, homogeneous in regard to the distribution and spatial pattern of disturbance categories, were identified.

The species richness of termites (Isoptera) under differing levels of forest disturbance in the Mbalmayo Forest Reserve, southern Cameroon

ABSTRACTFive forest plots of differing disturbance levels were sampled qualitatively for termites in the Mbalmayo Forest Reserve, southern Cameroon, using 100 m belt transects. Results showed a large reduction in species richness in two severely disturbed plots compared with a Near Primary plot, but little difference in two less disturbed regenerating plots; there is some evidence for a slight increase in species richness in the regenerating plots. Soil-feeders predominate in the primary and regenerating plots, but are greatly reduced in the severely disturbed plots. Wood-feeders appear to be more resilient to disturbance than soil-feeders, although their species richness is low in the most disturbed plots. The Termitinae are the dominant taxonomic group in the Near Primary plot, the Apicotermitinae in the less disturbed regenerating plots and the Macrotermitinae in the clear felled areas. There appears to be no secondary invasion of plots by savanna-associated species, and the small apparent increase in species richness in the less disturbed regenerating plots appears to be due to the influx of forest species usually associated with natural gaps.