Proportion Of Plant Cover Research Articles

Management strategies, silvopastoral practices and socioecological drivers in traditional livestock systems in tropical dry forests: An integrated analysis

Understanding traditional livestock management is essential in the design of more sustainable systems, given the forest loss associated to the growing demand for meat. In Latin America, where extensive livestock production is increasing, along with tropical dry forest (TDF) transformation, the role of small holders is critical for designing more sustainable management practices. This study is an integrated socioecological analysis of traditional livestock systems in a region with TDF in Mexico. The objectives were to: a) characterise the historical development and current state of livestock systems and silvopastoral practices, b) define the management strategies and their impacts on forests, and c) identify the regional and local socioecological drivers that influence decision-making processes in livestock and forest management. In-depth interviews were carried out to 32 cattle farmers and analysed using a qualitative-interpretative approach which included multivariate and narrative analyses. Three historical stages (colonization, promotion of livestock and forest conservation) had a strong impact in the development and current state of livestock systems. Access to natural and economic resources and proportion of plant cover (grassland/forest) were essential in defining four groups of management strategies. The main regional drivers favouring or restricting production include climate, native vegetation, markets and public policies; at the local scale, socioecological factors, such as water availability, native vegetation, economic assets, local knowledge and their interactions determine heterogeneity in management strategies, decision-making processes and their impacts on forests. Adaptive management of livestock and forests in a context of limited economic resources has allowed the conservation of forest areas and the use of silvopastoral practices with local tree species. The integrated socio-ecological approach and the use of mixed methods allowed a better understanding of drivers and their interrelationships, the local knowledge, objectives and perceptions of farmers in the decision-making processes regarding livestock and forest management. Perspectives of farmers on resource use can contribute to the design of more effective and inclusive policies for sustainable livestock systems in the dry tropics.

Forest fragmentation alters microhabitat availability for Neotropical terrestrial insectivorous birds

Many insectivorous birds of the tropical rainforest understory, particularly terrestrial species, are prone to local extinctions in fragmented forests. We evaluated the hypothesis that vegetation structural changes in rainforest fragments reduce the availability of microhabitats used by terrestrial insectivores. Near Manaus, Brazil, we compared the vegetation in forest fragments to the vegetation in a continuous forest site where nine species of terrestrial insectivores were observed foraging. Our focal species included those that are extinction prone in fragments (Myrmornis torquata [Wing-banded Antbird], Grallaria varia [Variegated Antbird], Hylopezus macularius [Spotted Antpitta]), a fragmentation-tolerant species (Myrmothera campanisona [Thrush-like Antpitta]), and species that have and intermediate response (Myrmeciza ferruginea [Ferruginous-backed Antbird], Formicarius colma [Rufous-capped Anttrush], Formicarius analis [Black-faced Antthrush], Conopophaga aurita [Chestnut-belted Gnateater], and Corythopis torquata [Ringed Antpipit]). To quantify vegetation, we measured sixteen habitat variables in 8-m radius plots where birds were observed foraging as well as random points in continuous forest and forest fragments of 1-, 10-, and 100-ha. Four principal components were produced from a principal component analysis and we selected a variable (leaf litter depth, plant cover 3–10m, density of plants 1–2m, and plant cover >20m) from each principal component for our fragment vs continuous forest comparisons. Using Markov chain Monte Carlo (MCMC) simulation, we estimated the probabilities that the density of plants 1–2m, proportion of plant cover 3–10m, and leaf litter depth increased with decreasing fragment area and also exceeded the values associated with fragmentation-sensitive species. We also tested the prediction that plant cover >20m decreased in forest fragments and that those sites became more open than typical sites used by our focal species. Our predictions were strongly supported: decreasing fragment size was correlated with increasing density of tall plants, increasing mid-story vegetation cover, decreased canopy cover, and increasing leaf litter depth. Even if our focal species are able to disperse to small forest fragments, our results suggest that they may not find enough appropriate habitat.

The Composition of Landbird Faunas of Islands Round South-Western Australia: Is There Evidence for Competitive Exclusion?

Three species of passerine bird, Zosterops lateralis (Latham), Lichenostomus virescens (Vieillot) and Sericornis frontalis (Vigors & Horsfield), have a widespread occurrence on islands round south-western Australia. The problem examined was whether the distribution patterns of the three species on these islands support hypotheses involving random colonization/persistence, unavailable suitable habitat, or competitive exclusion. The distribution pattern found was non-random. Evidence from the distri- bution of birds on sixty islands of different area and isolation suggested that Zosterops is the superior competitor on islands with area less than 10ha, but that Lichenostomus is superior to Zosterops on islands of area 10-100ha. Zosterops is also well represented on the more remote islands, whereas Licheno- stomus is not. Evidence from the availability of habitat and proportion of plant cover on twenty islands studied in detail suggested that Zosterops excludes Lichenostomus from islands as the proportion of cover available at 1.5 m above ground increases, and that Lichenostomus excludes Zosterops from islands on which both the area of suitable habitat is less than about 30 ha and the propor- tion of cover at 1.5 m above ground is very low. Sericornis was absent from all islands with area of suitable habitat less than about 60ha, irrespective of the amount of cover at 1.5 m above ground. However, it could not be established if this resulted from exclusion by Zosterops or Lichenostomus. Dispersal ability of these three species may be ranked as follows: Zosterops > Lichenostomus > Sericornis. The minimum habitat requirements seem to be: Zosterops, small area of relatively tall vegetation; Lichenostomus, small area of low vegetation; Sericornis, large area of low vegetation.