Can agroforest woodlots work as stepping stones for birds in the Atlantic forest region?

In fragmented landscapes, agroforest woodlots can potentially act as stepping stones facilitating movement between forest fragments. We assessed the influence of agroforest woodlots on bird distribution and diversity in the Atlantic forest region (SE Brazil), and also tested which categories of species can use different types of connection elements, and whether this use is influenced by the distance to large forest patches. We studied two fragmented landscapes, with and without stepping stones linking large fragments, and one forested landscape. Using a point count, a bird survey was undertaken in the fragmented landscapes in five different elements: large remnants (>400 ha), agroforest woodlots (0.4–1.1 ha), small patches (0.5–7 ha), riparian corridor, and pasture areas (the main matrix). Generalist and open-area species were commonly observed in the agroforest system or other connection elements, whereas only a few forest species were present in these connections. For the latter species, the distance of woodlots to large patches was essential to determine their richness and abundance. Based on our results and data from literature, we suggest that there is an optimal relationship between the permeability of the matrix and the efficiency of stepping stones, which occurs at intermediate degrees of matrix resistance, and is species-dependent. Because the presence of agroforest system favors a higher richness of generalist species, they appeared to be more advantageous for conservation than the monoculture system; for this reason, they should be considered as a management alternative, particularly when the matrix permeability requirement is met.     

Native and introduced land snail species as ecological indicators in different land use types in Java

We investigated the effects of different land use types and environmental parameters on the number and abundance of native and introduced land snail species in East Java. 2919 specimens were sampled and assigned to 55 species of which 8 are introduced. Whereas species richness was highest in primary forest, the highest number of introduced species was found in agroforest. The snail assemblages in different habitat types differ much clearer in composition than in total species richness. Plantations and agroforest are dominated by introduced pulmonates with regard to number of individuals, while primary forest is dominated by native prosobranchs. The habitat requirements of the introduced pulmonates differ from those of the native species. In the study area, the abundance of native as well as introduced pulmonate species increased with increasing human impact. However, the abundance of introduced pulmonate species decreased with increasing density of the canopy cover, whereas the abundance of native pulmonate species increased with increasing canopy cover. The abundance of native prosobranch land snails also tends to increase with increasing canopy cover and with the availability of deadwood, but decreased with increasing human impact. Improving the canopy cover and retaining deadwood in plantations and agroforests might help to control the populations of introduced species or even prevent their establishment in these habitats. Land snails are good indicators for the long-term stability of natural habitats, because several species are restricted to undisturbed natural habitats and because of their low dispersal abilities. However, complete inventories of land snail species are costly. Therefore we propose two indices that can be scored with much less effort, namely the percentage of prosobranch individuals and the percentage of individuals of introduced species. Both indices are significantly correlated with the number of native species. Dense plantations and agroforests bordering primary forests may protect the latter from introduced species and help to conserve the native fauna by reducing desiccation and buffering the human impact on the primary forests.     

农林复合生态系统与低层大气间的通量研究

根据近年在黄淮海平原大面积农林复合区的观测资料,采用简单的一维模型,讨论了此类复合系统与低层大气之间的热量、动量和水汽通量,比较了不同的结构林网形成的通量差异。结果表明,由于林冠层的摩擦作用,农林复合生态系统上空风速随高度增大较快,动量输送总是向下的。在层结稳定的夜间,其数值较大,而在湍流比较活跃的正午前后,由于垂直风切变减弱,动量输送也相应减小。夜间农林作物冠层的辐射冷却加强,近地层逆温梯度增大,加之作物冠层内部因辐射冷却而造成水汽凝结,冠层上部水汽大于冠层内部,此时热通量和水汽通量均向下。这一现象在白天日出后开始逆转,日出后,地面升温加快,并逐渐形成超绝热梯度,致使热量通量向上。此时农林作物蒸腾加剧,冠层高度范围内水汽含量增大,造成水汽向上输送。文中还讨论了一维模式的缺点,指出了进一步研究生态系统与大气相互作用的重要性.     

Shade cacao plantations (<Emphasis Type="Italic">Theobroma cacao</Emphasis>) and bat conservation in southern Bahia,Brazil

Nearly 40% of the remaining Atlantic Forest in southern Bahia state, Brazil, is a rustic agroforest of cacao (Theobroma cacao). These traditional shade plantations, locally known as ‘cabrucas’, are habitats for forest dwelling species. Here we investigated the potential role of this traditional crop as a support for bat assemblages in southern Bahia, establishing the extent to which the bat community structure found in this agricultural system is influenced by the proximity of forest tracts. We compared the bat community attributes (richness, diversity and dominance) and species-level response (capture frequency) between native forest tracts and shade cacao plantations located in two distinct landscapes, which varied in total amount of forest (patch sizes and total forested area) and in their proximity to forest tracts. The cabrucas contiguous to forest tracts showed a rich and abundant bat community, with samples showing capture rates, species richness, diversity and evenness significantly higher than those reported for forest tracts. This situation changes, however, when shade plantations are located at some distance from forest tracts ( > 1000 m). Bat communities in these isolated cabrucas are less diverse than those found in forests and nearby cabrucas, but in both cases, species usually associated with pristine habitats were found. These findings suggest that cabrucas per se are not forest surrogates, and their potential to harbor forest dwelling bat species is closely linked with the existence of nearby forest tracts that may act as a source for species populations. Therefore, the entire landscape should be considered for management, taking into account that maintenance of cabrucas together with the preservation and restoration of forest patches is probably direly needed if one wishes to conserve the bat diversity in southern Bahia for the long term.     

The role of traditional forest gardens in the conservation of tree species in West Kalimantan, Indonesia

We compared forest gardens, or tembawang, in twoareas in West Kalimantan, Indonesia, to patches of primary forest in terms ofsuccessional stage, mode of dispersal and characteristics of human use ofnon-planted tree species. This information was acquired for 144 tree speciesinventoried in six tembawang forest gardens and two intactnatural forest patches, through interviews at the site and a survey of theliterature. In particular older tembawang were found tohave practically the same proportions of species of different successionalstages and modes of dispersal as natural forests, thus emphasising the potentialof tembawang in conserving tree species. Non-planted treespecies of tembawang and natural forests also havepractically indistinguishable spectra of human uses, indicating that themanagement of these tembawang does not significantlydiscriminate between species with certain uses. However, we also identified twoaspects that should be taken into account in considering the conservation roleof tembawang. The floras of the two study areas showedsignificant regional differentiation, implying that efficient conservation inWest Kalimantan needs to have a rather dense network. We also found that latesuccessional species and animal-dispersed species oftembawang were more commonly geographically widespread thanspecies of the same ecological characteristics found in natural forests. Thus,even if tembawang are similar to natural forests in termsof numbers of species with different ecological characteristics, the compositionof non-planted tree species in tembawang is not a randomsample from natural forest, but overrepresents species that are easily dispersedand/or established.