Forest Blocks (forest + block)

Distribution by Scientific Domains

Selected Abstracts

Influences of restock age and habitat patchiness on Tree Pipits Anthus trivialis breeding in Breckland pine plantations

IBIS, Issue 2007
The British Tree Pipit Anthus trivialis population has shown a marked decline in recent decades, together with a range contraction that has been most apparent in central and southeast England. In East Anglia, the species is now largely restricted to heathland and, in particular, the conifer plantations established on light soils in these areas. Here I evaluate how Tree Pipits are influenced by the age of pine restock and the patchiness of habitat in Thetford Forest in the Breckland area of Norfolk and Suffolk, eastern England. Both the probability of occurrence and the densities of territory-holding Tree Pipits varied according to the age of coupes of restock , densities peaking in restock 1,6 years old , and were also significantly higher in coupes (a stand comprising one or more forest subcompartments planted in the same year, usually with the same tree crop) in the largest, most central forest block than in smaller, isolated blocks peripheral to this. Within coupes, the distribution and thus densities of Tree Pipits were limited by the availability of songposts. Few songflights finished on the ground or in flight and displaying birds only perched on restock once trees were at least 3 years old (0.8 m high) , thus, territories were only established away from bordering or retained mature trees once restock had reached this age. Pairing success was reduced among males with territories of less than 1 ha, as found in the highest densities in restock, but was unrelated to the proportion of songflights that individuals finished on perches. Thus, although the availability of songposts limited the distribution of the species, it did not appear to affect individual breeding success. The study highlights the importance of pine plantations for the species in lowland England, but also the benefits of large blocks of habitat and targeted forest management, for instance, the retention of mature trees in coupes of restock for Pipits to use as songposts. [source]

Nestedness in fragmented landscapes: birds of the box-ironbark forests of south-eastern Australia

ECOGRAPHY, Issue 6 2002
Ralph Mac Nally
Nestedness in biota as a function of species richness , biota of depauperate assemblages being non-random subsets of richer biotas , has been widely documented in recent years (see Wright et al. 1998, Oecologia 113: 1,20). Ordering sites by richness maximizes nestedness indices; however, ordering by other criteria such as area or isolation may be more ecologically interpretable. We surveyed birds in true fragments (35 in all), and in "reference areas" in large extant forest blocks (30 locations), of the same range of areas (10, 20, 40, 80 ha). The avifauna was divided into "bush birds", species dependent on forest and woodland, and "open country" species. We looked at nestedness in four data sets: "bush birds" in fragments and reference areas, and "all birds" in fragments and in reference areas. All data sets were significantly nested. Ordering by area in all cases was not significantly less nested than ordering by richness. Ordering by area in fragments was significantly greater than in reference areas, but the differences in standardized nestedness indices were small (<15%). We identified those birds that had distributions among fragments that conformed strongly with area, those that were more randomly distributed and some species that were more likely to occupy the smallest fragments. Among the latter was a hyperaggressive, invasive, colonial native species (noisy miner Manorina melanocephala). A suite of small, insectivorous birds were more likely to strongly conform with expected distributions in relation to area, which was consistent with observations of their vulnerability to the effects of the noisy miner in smaller fragments. [source]

Are local patterns of anthropoid primate diversity related to patterns of diversity at a larger scale?

M. J. Lawes
Abstract Aims, (1) To determine the relationship between local and regional anthropoid primate species richness. (2) To establish the spatial and temporal scale at which the ultimate processes influencing patterns of primate species coexistence operate. Location Continental landmasses of Africa, South America and Asia (India to China, and all islands as far south as New Guinea). Methods, The local,regional species richness relationship for anthropoid primates is estimated by regressing local richness against regional richness (independent variable). Local richness is estimated in small, replicate local assemblages sampled in regions that vary in total species richness. A strong linear relationship is taken as evidence that local assemblages are unsaturated and local richness results from proportional sampling of the regional pool. An asymptotic curvilinear relationship is interpreted to reflect saturated communities, where strong biotic interactions limit local richness and local processes structure the species assemblage. As a further test of the assumption of local assemblage saturation, we looked for density compensation in high-density local primate assemblages. Results, The local,regional species richness relationship was linear for Africa and South America, and the slope of the relationship did not differ between the two continents. For Asia, curvilinearity best described the relationship between local and regional richness. Asian primate assemblages appear to be saturated and this is confirmed by density compensation among Asian primates. However, density compensation was also observed among African primates. The apparent assemblage saturation in Asia is not a species,area phenomenon related to the small size of the isolated islands and their forest blocks, since similar low local species richness occurs in large forests on mainland and/or peninsular Asia. Main conclusions In Africa and South America local primate assemblage composition appears to reflect the influence of biogeographic processes operating on regional spatial scales and historical time scales. In Asia the composition of primate assemblages are by-and-large subject to ecological constraint operating over a relatively small spatial and temporal scale. The possible local influence of the El Niņo Southern Oscillations on the evolution and selection of life-history characteristics among Asian primates, and in determining local patterns of primate species coexistence, warrants closer inspection. [source]

Birds on edge: avian assemblages along forest-agricultural boundaries of central Victoria, Australia

Monica J. Campi
Habitat clearance generally produces fragmented landscapes. A major consequence is the creation of large amounts of new ,edge habitat', often of a kind not previously existing, such as abrupt forest- agricultural land interfaces. Much work from around the world suggests that proliferation of edge habitat seriously affects birds reliant on large forest blocks to persist, and the intrusion of edge specialists into areas they did not previously occupy. These processes often generate avifaunal gradients in which assemblages change from the interior to the edge. This effect is explored in the largest remnant block of box-ironbark forest of central Victoria, Australia (about 30,000 ha). Eight radially oriented survey lines were established around the periphery of the block. Along each survey line, five transects with long axes oriented parallel to the edge were positioned with midlines at 40 m, 160 m, 280 m and 400 m into the forest, and one transect 80 m into the agricultural land, yielding a total of 40 transects. Six identical transects were located deep within the forest (> 2 km). There was little evidence of a change in the avifauna from interior to edge, although mean richness was depressed in the edge habitats compared with forest interior transects. These results were essentially the same for ,all species' or ,forest dependent' species. Thus, there is little evidence for marked edge effects on the avifauna of these large forest blocks, although work in intermediate sized remnants (100-1000 ha) is needed to identify thresholds at which edge effects begin to be manifested. [source]