Silvicultural Landscapes Research Articles

Trophic niche overlap among Neotropical carnivores in a silvicultural landscape

Abstract To enable long-term coexistence, species need to differentiate at least one of the three main dimensions of the ecological niche (temporal, spatial, or trophic dimension). Here, we investigated whether mammalian predators (Chrysocyon brachyurus, Cerdocyon thous, Lycalopex vetulus, and Puma concolor) follow the prediction of trophic niche partitioning, which is expected when partitioning of food resources represents an important mechanism for coexistence. We predicted low niche overlap in general and low between P. concolor and the other species. We analyzed 207 fecal samples collected at a landscape composed of forest remnants immersed in Eucalyptus plantations. Food items (animals and plants) were identified using exoskeletons, feathers, scales, teeth, hair, and seeds. We calculated the frequency and percentage of occurrence of food items, niche breadth, and niche overlap between pairs of species. Prey size was similar among all predators, consuming mainly small-sized prey (<1 kg). However, niche breadth was larger for smaller carnivores compared to larger ones. No species pair showed significantly lower niche overlap than expected by chance. Our study provided detailed information on trophic resource use of sympatric carnivores, showing that trophic niche partitioning seems not to be crucial for the coexistence of carnivores in the study area.

Diversity of small mammals on the early second commercial cycle of Eucalyptus plantations in southeast Brazil

In this study we surveyed small mammals on a silvicultural landscape during the early second 7-year commercial cycle of Eucalyptus plantations in southeast Brazil. To do so we used the same method (pitfall traps) and part of the same sampling units used by a previous study during the early first commercial cycle. Our results suggest that Eucalyptus plantations are used as habitat by part of the original assemblage of small mammals along their commercial cycles. Four new species were detected on the second cycle but three were only detected on the first. In both cycles Eucalyptus plantations presented smaller abundance of small mammals than native vegetation and abandoned pastures around. Oligoryzomys nigripes (a species from the Atlantic forest) replaces O. flavescens and Calomys tener (species from Cerrado) from the first to the second commercial cycle. Species richness of the landscape matrix tend to remain lower than the native vegetation and abandoned pastures on the early second commercial cycle. Similarly to the first cycle, the species that use Eucalyptus plantations are not affected by the distance to the border of the conservation areas (i.e., native vegetation and abandoned pastures). The land sharing approach of the silvicultural sector in Brazil apparently prevented a higher small mammal species local extinction in relation to a former matrix of pastures. This provides a relevant conservation value to local silvicultural landscapes due to the role of small mammals in local trophic network.

Temporal dynamics of small mammals in Eucalyptus plantations in Southeast Brazil

The presence of small terrestrial mammals along the commercial cycle of Eucalyptus plantations indicates that silvicultural landscapes can be considered as their habitat. In the present study we evaluated the temporal variation of small terrestrial mammals for more than 10 generations during the first commercial cycle of Eucalyptus in Southeast Brazil. During this period we carried out forty-four monthly campaigns, totaling 10,560 bucket.nights in pitfall traps. Thirteen species (four marsupials and nine rodents) were collected in the Eucalyptus plantations, seven of which (Akodon montensis, Calomys tener, Cryptonanus agricolai, Gracilinanus microtarsus, Necromys lasiurus, Oligoryzomys flavescens, and Oligoryzomys nigripes) persisted for the entire study period. In general, they have an explosive population growth during the first two years of collection followed by a decline in all environments, and an apparent regrowth trend in the fourth year for some species with a trend in dominant species from Cerrado to forest dwellers. Marsupials exhibited a similar trend, but slower and later. The spatio-temporal patterns of variation detected in this study strongly suggest that for most of the remaining species of small rodents and marsupials, silvicultural landscapes have distinct habitats including the Eucalyptus plantations. This means that they should be evaluated in terms of its habitat quality not only its permeability. The perception of the Eucalyptus plantations as habitat should stimulate the development of wildlife-friendly management techniques, which improve their carrying capacity, food web complexity and biological diversity without compromising their primeval mission of biological production.

Diversity and distribution patterns of medium to large mammals in a silvicultural landscape in south-eastern Brazil

Abstract: Agricultural landscapes cover approximately 35% of Brazil and are the second greatest threat to biodiversity worldwide. In Brazil, seven millions hectars of land is covered with Eucalyptus plantations, which is considered to have low conservation value. However, studies have shown that heterogeneous silvicultural landscapes, made up of Eucalyptus matrices and patches dedicated to conservation, are able to support a considerable diversity of wild mammals. This study aims to assess the diversity and distribution patterns of medium-to-large-sized mammals in a silvicultural landscape in Angatuba, Sao Paulo, Brazil. Nineteen species were detected by camera traps within the study area. Diversity indices did not vary among habitat types (i.e., native vegetation, abandoned pasture and Eucalyptus plantations), suggesting that the species use the landscape as a whole. A relatively diverse range of predator species was found in the area, suggesting that future monitoring programs should focus on predator-prey relationships. A low diversity of frugivores was detected, indicating that management actions should be taken to facilitate their local recovery. Our results stress the fundamental importance of the conservation areas (Permanent Preservation Areas and Legal Reserve) in silvicultural landscapes, as these areas help maintain complexity of the landscape structure.

Ticks (Acari: Ixodidae) identified from prey-predator interactions via faecal analysis of Brazilian wild carnivores.

Between July 2008 and May 2010, we conducted a trophic study on 12 Brazilian wild carnivore species through their faecal analysis in a silvicultural landscape at Angatuba municipality, southern São Paulo state. Predator faeces was identified by morphology, predator hair, and surrounding tracks; prey remnants within faeces were used for morphological identification of the prey. Among the recovered ectoparasites, there were 89 specimens of six tick species in 21 (4.0%) out of 523 analysed samples. Ticks were identified to species level, based on external morphological characters, as following: adults of Amblyomma ovale and Amblyomma sculptum; nymphs of Amblyomma brasiliense, Amblyomma calcaratum, Amblyomma dubitatum, A. ovale, and Ixodes schulzei; and larvae of Amblyomma sp. and Ixodes sp. Generally, the recovered immature ticks were associated with consumed prey (small birds or small mammals), whereas adults were associated with the predator itself, ingested during its self-grooming. Our data show that faeces is an additional information source on ticks in Brazil and which may provide information on ectoparasite-predator-prey interactions.

Neotropical small mammals’ diversity in the early cycle of commercial Eucalyptus plantations

Studies carried out in Brazil revealed that Eucalyptus plantations shelter numerous species of small-size non-flying mammals. However, their distribution pattern inside the Eucalyptus plantations remains unknown. This study aimed at the identification of possible influence of distances from the remaining native revegetation areas and riparian systems, on spatial distribution and abundance of small-size mammals in Eucalyptus plantations. This study was carried at Eucalyptus stands recently planted (0–3 years) at the municipality of Angatuba, Sao Paulo state, Brazil between August 2007 and July 2009. The survey was carried out using pitfall traps at 14 sampling units inside Eucalyptus plantations 60–1130 m away from the borders. With a sampling effort of 2,449 bucket night, the experiment captured 680 individuals belonging to 12 species of small-size mammals (rodents and marsupials). The colonization process of Eucalyptus plantations was apparently initiated by generalist species from open Cerrado. In the present study, we did not find any clear correlation between specific richness and abundance of individuals and the distance from native revegetation areas or closer riparian systems. The study suggests that Eucalyptus plantations are permeable matrices to, at least, more generalist species present in the silvicultural landscapes (i.e. composed by an Eucalyptus plantation as the matrix and native vegetation patches). However, further studies must prioritize analyzing the influence of agricultural/sivilcultural practices (e.g., plantation structure and harvest frequency) on habitat quality and carrying capacity of agricultural/silvicultural landscape matrices, as well as implementing long-term monitoring programs to assess the impact of complete production cycles (some years) and along cycles of Eucalyptus plantations (some decades), on rodents population’s diversity and dynamics patterns.

Intraspecific isotopic niche variation in broad-snouted caiman (Caiman latirostris)

Strategies to minimise intraspecific competition are common in wild animals. For example, individuals may exploit food resources at different levels of the food chain. Analyses of stable isotopes are particularly useful for confirming variations in an intraspecific niche because the chemical composition of animals tends to reflect both the food consumed and the habitats occupied by the species. However, studies using this methodology to investigate neotropical crocodilians are scarce. This study aimed to verify the existence of ontogenetic and sexual niche variation in broad-snouted caiman in a silvicultural landscape in Brazil through the use of carbon and nitrogen stable isotopes. The isotopic ratios of carbon and nitrogen were determined in claw samples collected from 24 juveniles, 8 adults, and 16 hatchlings of C. latirostris. We identified a discrete ontogenetic variation in the isotopic niche and sexual difference only for juveniles. These results may indicate differences in the exploitation resources and a consequent reduction in competition between age classes.

Terrestrial non-volant small mammals in agro-silvicultural landscapes of Southeastern Brazil

The area covered by Eucalyptus plantations is significantly increasing in Brazil for economic reasons. However, the impact of such land use change is still unknown. In this study we evaluated the spatial–temporal distribution and abundance of terrestrial non-volant small mammals on a recently converted landscape whose matrix is formed by Eucalyptus plantations up to 3years of age. From August 2007 to July 2009 we carried out monthly sampling campaigns over a grid of 30 sampling units, formed by pitfall traps covering both the landscape matrix of Eucalyptus plantations (n=18) and legal conservation areas of native vegetation (n=7) and abandoned pastures (n=5). A total of 1640 individuals from 14 species of the orders Didelphimorphia (4 spp.) and Rodentia (10 spp.) were captured. However, only three species of rodents (Olygorysomys flavescens, Oligoryzomys nigripes and Calomy tener) represented 81.8% of the total amount. Eucalyptus plantations had a lower species richness and abundance than the abandoned pasture and the remaining fragments of native vegetation. Although the present species are predominantly generalists, there is clear distinction among environments in terms of their species composition and relative abundance, which also present a pronounced time variation. The assemblage found in this study suggests that silvicultural landscapes still have some conservation value, with species that seem to be resident at the Eucalyptus plantations. Moreover, the presence of the native and abandoned pastures patches imbibed in the Eucalyptus plantation matrix may increase the carrying capacity of such a silvicultural system and these landscapes may play a role in maintaining local biodiversity.

The value of forest strips for understorey birds in an Amazonian plantation landscape

Remnant forest strips are frequently proposed as valuable conservation tools in fragmented tropical landscapes, yet we currently lack evidence to evaluate their potential conservation value for native biota. We examined the potential value for understorey forest birds of 30-year-old riparian and terra firme (unflooded) primary forest strips within a large silvicultural landscape in the north-east Brazilian Amazon, where the matrix is dominated by Eucalyptus plantations. We conducted mist-netting in eight forest strips connected to continuous forest (four of each forest type), with a total of 24 replicate sampling sites located near to (<1 km), far from (2.5–9 km), and within undisturbed forest controls (i.e. 16 samples within the strips, and 8 in controls). Bird communities in both strip types changed with increasing distance along forest remnants into the plantation matrix. Matrix-embedded samples were characterised by a higher representation of birds typical of secondary growth forest but not those typical of the Eucalyptus-dominated matrix. While the long-term viability of the bird populations in these remnants remains unclear, our data demonstrate that forest strips can provide important habitat for many bird species that are otherwise rarely found outside primary forest. Forest strips therefore provide an important tool to enhance biodiversity conservation in plantation landscapes. The relative practical ease with which these areas can be selected and maintained means that the protection of forest strips as part of a wider conservation strategy is likely to have particular appeal to policy makers and landscape managers working in the human-dominated tropics.

Undoing the damage: silviculture for ecologists and environmental scientists

Introduction Agrobionomic Principles Economic Measures and Spatial Patterns Temporal Dynamics Use Concepts Niche Transitions and Ecological Services Risk Containment Monoculture Bicultures Three-Plus Polycultures Taungyas Natural Forest Management Agroforests Nature - Silvicultural Interface Community Forestry Silvicultural Landscapes Perspectives

Bird Communities in Silvicultural Fragments of Holly Springs National Forest, Mississippi

I surveyed bird communities during the 1999 and 2000 breeding seasons in oak-pine sawtimber (ST) stands, pine poletimber (PT) stands, high-density pine seed- ling (SS) stands, and recently clearcut areas throughout Holly Springs National Forest (HSNF), in north-central Mississippi. Species richness was 25% greater in forested stands compared to clearcut areas, yet total bird density was 50% greater in clearcut areas. Bird communities ranged from open-habitat assemblages in clearcut areas to forest-obligate assemblages in ST stands. Little overlap of avian community composi- tion was observed between ST stands and clearcut areas. PT and SS stands supported avian communities where most species were observed at intermediate abundance values compared to ST or clearcut areas. Highly fragmented, closed-canopy stands embedded within the silvicultural landscape of HSNF do not support large populations of species traditionally associated with detrimental edge effects on forest-obligate songbirds. Intensively managed PT and SS stands appear to provide suboptimal habitat for forest and grassland species. Land managers in HSNF could maximize regional avian diversity by maintaining a mosaic of large closed-canopy, oak-pine stands, and fire- maintained open areas embedded among other silvicultural stand types.

Demographic Effects of Habitat Selection by Hermit Thrushes Wintering in a Pine Plantation Landscape

Many species of migratory songbirds use silvicultural landscapes during the nonbreeding season. However, variation in habitat quality (i.e., the differential relative fitness value of habitats) resulting from different silvicultural management strategies and different age classes of these habitats is poorly understood. We studied the patterns of winter habitat selection by hermit thrushes (Catharus guttatus) among pine and hardwood habitats within a pine plantation landscape in southeastern Louisiana. We compared arrival patterns, relative abundance, territory size, body condition (mass, fat, and feather regrowth), between-winter site fidelity, and overwinter survivorship among birds in 3 age classes of even-aged loblolly pine (Pinus taeda) plantation and hardwood forest. We considered these demographic and condition measures as proximate estimates of relative fitness, and thus as indicators of habitat quality. Hermit thrushes in pole-stage (13-16 yr old) pine habitat had smaller territories, higher relative abundance, stayed leaner, and regrew feathers faster than birds in the other habitats, which suggests that this is the best habitat for wintering hermit thrushes among those we studied. Among other habitats, hardwood forest appears to be the lowest quality, but some measures (fat, territory size, and overwinter survivorship) indicate that the sapling-stage pine habitat is the lowest quality. Early arriving birds, disproportionately adults, avoid hardwoods, but beyond this we could find no evidence of segregation by age, sex, or body size among habitats. Our findings suggest that relatively small differences in habitat type and within-season changes in habitat quality can have important effects on the overwinter success of hermit thrushes. Pine plantations that differ in age by less than 10 years differentially affect the condition and demographics of wintering hermit thrushes. For conservation strategies to be successful, the dynamic spatial and temporal variation in habitat quality must be incorporated into models of population processes. Although pine plantation managers should consider multiple wildlife species, they also must be aware that individual species may have differential success among suitable habitats.

Ecology and Conservation of a Rare, Old-Growth-Associated Canopy Lichen in a Silvicultural Landscape

Abstract Nephroma occultum Wetm. is a rare, epiphytic lichen associated with old-growth forests of northwestern North America. We describe its distribution, abundance, and habitat within the managed landscape of a southwestern Oregon watershed. Because this species is found mainly in the canopy, we used direct canopy access (tree climbing) in combination with ground (litter) searches for our surveys. We recommend this dual approach when confident determination of presence or absence of a canopy species is needed. Our surveys confirm that N. occultum is a rare old-growth associate within the area of this study, the southernmost extension of its known range. It was both rare across the landscape and uncommon in our primary study site, a 500 yr old stand. It was most often found growing close to the trunk on branches of large Pseudotsuga menziesii, but its distribution was sporadic even within an old-growth stand. The scarcity of very old stands, in combination with the limited ability of this species to dis...