Birds in the matrix: the role of agriculture in avian conservation in the Taita Hills,Kenya

Agricultural conversion of tropical forests is a major driver of biodiversity loss. Slowing rates of deforestation is a conservation priority, but it is also useful to consider how species diversity is retained across the agricultural matrix. Here, we assess how bird diversity varies in relation to land use in the Taita Hills, Kenya. We used point counts to survey birds along a land‐use gradient that included primary forest, secondary vegetation, agroforest, timber plantation and cropland. We found that the agricultural matrix supports an abundant and diverse bird community with high levels of species turnover, but that forest specialists are confined predominantly to primary forest, with the matrix dominated by forest visitors. Ordination analyses showed that representation of forest specialists decreases with distance from primary forest. With the exception of forest generalists, bird abundance and diversity are lowest in timber plantations. Contrary to expectation, we found feeding guilds at similar abundances in all land‐use types. We conclude that whilst the agricultural matrix, and agroforest in particular, makes a strong contribution to observed bird diversity at the landscape scale, intact primary forest is essential for maintaining this diversity, especially amongst species of conservation concern.     

Water inputs across a tropical montane landscape in Veracruz,Mexico: synergistic effects of land cover,rain and fog seasonality,and interannual precipitation variability

Land‐cover change can alter the spatiotemporal distribution of water inputs to mountain ecosystems, an important control on land‐surface and land‐atmosphere hydrologic fluxes. In eastern Mexico, we examined the influence of three widespread land‐cover types, montane cloud forest, coffee agroforestry, and cleared areas, on total and net water inputs to soil. Stand structural characteristics, as well as rain, fog, stemflow, and throughfall (water that falls through the canopy) water fluxes were measured across 11 sites during wet and dry seasons from 2005 to 2008. Land‐cover type had a significant effect on annual and seasonal net throughfall (NTF <0=canopy water retention plus canopy evaporation; NTF >0=fog water deposition). Forest canopies retained and/or lost to evaporation (i.e. NTF<0) five‐ to 11‐fold more water than coffee agroforests. Moreover, stemflow was fourfold higher under coffee shade than forest trees. Precipitation seasonality and phenological patterns determined the magnitude of these land‐cover differences, as well as their implications for the hydrologic cycle. Significant negative relationships were found between NTF and tree leaf area index (R²=0.38, P<0.002), NTF and stand basal area (R²=0.664, P<0.002), and stemflow and epiphyte loading (R²=0.414, P<0.001). These findings indicate that leaf and epiphyte surface area reductions associated with forest conversion decrease canopy water retention/evaporation, thereby increasing throughfall and stemflow inputs to soil. Interannual precipitation variability also altered patterns of water redistribution across this landscape. Storms and hurricanes resulted in little difference in forest‐coffee wet season NTF, while El Niño Southern Oscillation was associated with a twofold increase in dry season rain and fog throughfall water deposition. In montane headwater regions, changes in water delivery to canopies and soils may affect infiltration, runoff, and evapotranspiration, with implications for provisioning (e.g. water supply) and regulating (e.g. flood mitigation) ecosystem services.     

Development of a multimetric plant-based index of biotic integrity for assessing the ecological state of forested,urban and agricultural natural wetlands of Jimma Highlands,Ethiopia

Wetlands are vital natural resources thereby providing ecological and socio-economic benefits to the people. However, anthropogenic activities have seriously changed the ecological conditions of wetlands worldwide, especially in developing nations like Ethiopia. Predominantly, the absence of biomonitoring tool greatly hampers the protection and management of wetlands. Therefore, the objective of this research is to develop a plant-based index of biological integrity for facilitating the management of wetlands. Accordingly, 122 plant species belonging to 37 families were collected and identified from forested, urban and agricultural wetland types and included in the analysis of the plant metrics. Initially, we reviewed and screened 35 potential metrics. Then, we selected four core metrics (% cover of native species, sensitive plant species richness, tolerant plant species richness and% of shrub species richness) using the decrease or increase responses to human disturbances, Mann-Whitney U test and redundant metric test. A trisect-quartile range system using box plots of the reference or impaired sites of wetlands was established to provide values for each core metrics. Then after, we combined the core metrics to develop the plant-based index of biological integrity. Finally, we validated the index by comparing the index response to different wetland types. Additionally, the index was validated based on the measured environmental variables that characterize the human disturbance gradient of wetlands. We found that the plant-based index is robust to discriminate the reference wetlands from impaired wetlands and can also be used as an effective tool for evaluating the long term natural wetland conditions of the Eastern African wetlands in the future.     

Diversity and composition of Arctiidae moth ensembles along a successional gradient in the Ecuadorian Andes

Andean montane rain forests are among the most species‐rich terrestrial habitats. Little is known about their insect communities and how these respond to anthropogenic habitat alteration. We investigated exceptionally speciose ensembles of nocturnal tiger moths (Arctiidae) at 15 anthropogenically disturbed sites, which together depict a gradient of forest recovery and six closed‐forest understorey sites in southern Ecuador. At weak light traps we sampled 9211 arctiids, representing 287 species. Arctiid abundance and diversity were highest at advanced succession sites, where secondary scrub or young forest had re‐established, followed by early succession sites, and were lowest, but still high, in mature forest understorey. The proportion of rare species showed the reverse pattern. We ordinated moth samples by non‐metric multidimensional scaling using the chord‐normalized expected species shared index (CNESS) index at various levels of the sample size parameter m. A distinct segregation of arctiid ensembles at succession sites from those in mature forest consistently emerged only at high m‐values. Segregation between ensembles of early vs. late succession stages was also clear at high m values only, and was rather weak. Rare species were responsible for much of the faunal difference along the succession gradient, whereas many common arctiid species occurred in all sites. Matrix correlation tests as well as exploration of relationships between ordination axes and environmental variables revealed the degree of habitat openness, and to a lesser extent, elevation, as best predictors of faunal dissimilarity. Faunal differences were not related to geographical distances between sampling sites. Our results suggest that many of the more common tiger moths of Neotropical montane forests have a substantial recolonization potential at the small spatial scale of our study and accordingly occur also in landscape mosaics surrounding nature reserves. These species contribute to the unexpectedly high diversity of arctiid ensembles at disturbed sites, whereas the proportion of rare species declines outside mature forest.     

Bird richness and composition along an agricultural gradient in New Guinea: The influence of land use,habitat heterogeneity and proximity to intact forest

Abstract We examined variation in bird species richness, abundance and guild composition along an agricultural gradient in New Guinea, and looked for any additive influence of habitat heterogeneity on these variables. The study was based on a grid of survey plots, six plots wide and 24 plots long with the long axis running from a settlement 2.4 km through active and abandoned agricultural plots towards a large area of forest. Each circular survey plot (25 m radius) was assigned to a broad habitat type, ten habitat measures taken, and birds counted for 1 h in each plot. Principal component analysis (PCA) habitat axis 1 described an axis of decreasing forest alteration (larger trees, greater tree densities, fuller canopy) that was positively correlated with distance from the settlement. Bird richness and abundance were highest at intermediate disturbance levels (plots with mid‐range axis 1 scores). Proportions of insectivores and frugivores increased with decreasing forest alteration, while proportions of nectarivores decreased. We calculated three measures of habitat heterogeneity by comparing each plot's PCA score to those of eight neighbouring plots (50–110 m away). These measures reflected how different the plot was to its neighbours, how variable the habitat was around the plot, and the degree to which the plot bordered less disturbed forest. We related these measures to plot bird variable scores independently, and to residuals following regressions of bird scores against PCA scores. Heterogeneity measures had no significant influence on abundance or richness measures, but there were greater proportions of frugivores in plots showing a given degree of habitat alteration if they bordered more pristine habitat. While we readily identified differences in bird communities along the agricultural gradient, the influences of habitat heterogeneity were not striking for birds at this fine scale.     

Rapid redistribution of agricultural land alters avian richness,abundance, and functional diversity

The conversion of natural, or seminatural, habitats to agricultural land and changes in agricultural land use are significant drivers of biodiversity loss. Within the context of land‐sharing versus land‐sparing debates, large‐scale commercial agriculture is known to be detrimental to biodiversity, but the effects of small‐scale subsistence farming on biodiversity are disputed. This poses a problem for sustainable land‐use management in the Global South, where approximately 30% of farmland is small‐scale. Following a rapid land redistribution program in Zimbabwe, we evaluated changes in avian biodiversity by examining richness, abundance, and functional diversity. Rapid land redistribution has, in the near term, resulted in increased avian abundance in newly farmed areas containing miombo woodland and open habitat. Conversion of seminatural ranched land to small‐scale farms had a negative impact on larger‐bodied birds, but species richness increased, and birds in some feeding guilds maintained or increased abundance. We found evidence that land‐use change caused a shift in the functional traits of the communities present. However, functional analyses may not have adequately reflected the trait filtering effect of land redistribution on large species. Whether newly farmed landscapes in Zimbabwe can deliver multiple benefits in terms of food production and habitat for biodiversity in the longer term is an open question. When managing agricultural land transitions, relying on taxonomic measures of diversity, or abundance‐weighted measures of function diversity, may obscure important information. If the value of smallholder‐farmed land for birds is to be maintained or improved, it will be essential to ensure that a wide array of habitat types is retained alongside efforts to reduce hunting and persecution of large bird species.     

Changes in tropical forest vegetation along an altitudinal gradient in the Udzungwa Mountains National Park, Tanzania

This study describes changes in woody vegetation in the Mwanihana forest, Udzungwa Mountains National Park, Tanzania, over an altitude range of 470–1700 m. Two methods, fixed‐ and variable‐area plots, are compared to elucidate altitudinal variation in tropical forest structure, diversity and community composition. Six 25 m × 100 m fixed area plots recorded a total of 2143 woody stems of ≥3 cm d.b.h. from 204 species. The 78 variable‐area plots recorded the nearest twenty trees of ≥20 cm d.b.h. to an objectively chosen point, giving a total of 1560 stems in 9.1 ha from 156 species. A linear trend of increasing stem density with altitude was seen for variable‐area plots. Species diversity is highest at high elevations. There was no clear zonation of elevational vegetation types. Restricted range taxa occur at all altitudes sampled. The study also revealed some methodological considerations. Bias in sample size and plot area can be tested by employing two sampling methods. Of the two methods used, fixed area plots are preferred as variable area plots are impractical in tangled understorey. Plot size must be controlled for in order to make reliable observations of diversity. Sampling along a continuous or near‐continuous altitudinal gradient with sufficient replication is also important.     

Shadow conservation and the persistence of sacred church forests in northern Ethiopia

Land‐use change threatens biodiversity and ecosystem function worldwide. These changes have impacts on weather patterns, carbon storage, biodiversity, and other ecosystem services from regional to local scales. Only 8 percent of tropical forests are formally recognized as conservation areas, however globally, there is a network of sites that are protected because they are sacred and as a result act as ‘shadow’ conservation for biodiversity. Unlike other types of protected sites (e.g., national parks), these sites are seats of religious ritual that anchor a community's cultural identity, while also conserving biological diversity and other ecosystem services. We studied the extent and status of sacred forests in northern Ethiopia, which are threatened because of their small size (~5 ha) and isolation, increasing their exposure to edge effects and human pressures. Using historical and modern imagery, we found that over the last 50 yr, sacred forests have increased in area, but decreased in crown closure. We also found that forest ecological status, via ground‐level investigation, had high mean human disturbance (e.g., trails, plantations, exotic planting; 37%); and that forests close to markets (e.g., cities) increased in area due to planting of Eucalyptus (exotic), indicating a potential threat to their persistence and value as shelters of the church.     

Diversity patterns of vascular epiphytes along an elevational gradient in the Andes

Aim To document the elevational pattern of epiphyte species richness at the local scale in the tropical Andes with a consistent methodology. Location The northern Bolivian Andes at 350–4000 m above sea level. Methods We surveyed epiphytic vascular plant assemblages in humid forests in (a) single trees located in (b) 90 subplots of 400 m² each located in (c) 14 plots of 1 ha each. The plots were separated by 100–800 m along the elevational gradient. Results We recorded about 800 epiphyte species in total, with up to 83 species found on a single tree. Species richness peaked at c. 1500 m and declined by c. 65% to 350 m and by c. 99% to 4000 m, while forests on mountain ridges had richness values lowered by c. 30% relative to slope forests at the same elevations. The hump‐shaped richness pattern differed from a null‐model of random species distribution within a bounded domain (the mid‐domain effect) as well as from the pattern of mean annual precipitation by a shift of the diversity peak to lower elevations and by a more pronounced decline of species richness at higher elevations. With the exception of Araceae, which declined almost monotonically, all epiphyte taxa showed hump‐shaped curves, albeit with slightly differing shapes. Orchids and pteridophytes were the most species‐rich epiphytic taxa, but their relative contributions shifted with elevation from a predominance of orchids at low elevations to purely fern‐dominated epiphyte assemblages at 4000 m. Within the pteridophytes, the polygrammoid clade was conspicuously overrepresented in dry or cold environments. Orchids, various small groups (Cyclanthaceae, Ericaceae, Melastomataceae, etc.), and Bromeliaceae (below 1000 m) were mostly restricted to the forest canopy, while Araceae and Pteridophyta were well represented in the forest understorey. Main conclusions Our study confirms the hump‐shaped elevational pattern of vascular epiphyte richness, but the causes of this are still poorly understood. We hypothesize that the decline of richness at high elevations is a result of low temperatures, but the mechanism involved is unknown. The taxon‐specific patterns suggest that some taxa have a phylogenetically determined propensity for survival under extreme conditions (low temperatures, low humidity, and low light levels in the forest interior). The three spatial sampling scales show some different patterns, highlighting the influence of the sampling methodology.     

Contrasting patterns in species richness of birds,butterflies and plants along riparian corridors in an urban landscape

Aim Urbanization is a major driver of global land‐use change, substantially modifying patterns of biodiversity. Managing these impacts has become a conservation priority. The creation and maintenance of greenways, such as river corridors, is frequently promoted as a strategy for mitigating habitat fragmentation in urban areas by bringing semi‐natural habitat cover into city centres. However, there is little evidence to support this assertion. Here, we examine whether riparian zones maintain semi‐natural habitat cover in urban areas and how species richness varies along such zones. Location Sheffield, Northern England. Methods Multiple taxonomic groups (birds, butterflies, plants) were surveyed at 105 sites spanning seven riparian corridors that transect the study system. For all groups, we model the relationships between species richness and environmental variables pertinent to an urban system. To test whether riparian zones can act to maintain semi‐natural habitats within a city, we modelled the proportion of semi‐natural land cover within 250 m grid squares that do, and do not, contain a river. Results Species richness varied markedly in relation to distance from the urban core. Trends differed both between taxonomic groups and between rivers, reflecting the complex patterns of environmental variation associated with cities. This suggests that biodiversity surveys that focus on a single group or transect cannot reliably be used as surrogates even within the same city. Nonetheless, there were common environmental predictors of species richness. Plant, avian and butterfly richness all responded positively to Habitat Diversity and the latter two declined with increases in sealed surface. Main conclusions Multiple transects and taxonomic groups are required to describe species richness responses to urbanization as no single pattern is evident. Although riparian zones are an important component of the mosaic of urban habitats, we find that river corridors do not disproportionately support tree and Natural Surface Cover when compared to non‐riverine urban areas.     

Stem respiration in tropical forests along an elevation gradient in the Amazon and Andes

Autotrophic respiration involves the use of fixed carbon by plants for their own metabolism, resulting in the release of carbon dioxide as a by‐product. Little is known of how autotrophic respiration components vary across environmental gradients, particularly in tropical ecosystems. Here, we present stem CO₂ efflux data measured across an elevation transect spanning ca. 2800 m in the Peruvian Amazon and Andes. Forest plots from five elevations were studied: 194, 210, 1000, 1500, and 3025 m asl Stem CO₂ efflux (R_s) values from each plot were extrapolated to the 1‐ha plot level. Mean R_s per unit stem surface area declined significantly with elevation, from 1.14±0.12 at 210 m elevation to 0.62±0.09 μmol C m⁻² s⁻¹ at 3025 m elevation. When adjusted for changing forest structure with elevation, this is equivalent to 6.45±1.12 Mg C ha⁻¹ yr⁻¹ at 210 m elevation to 2.94±0.19 Mg C ha⁻¹ yr⁻¹ at 3025 m elevation. We attempted to partition stem respiration into growth and maintenance respiration components for each site. Both growth and maintenance respiration rates per unit stem showed similar, moderately significant absolute declines with elevation, but the proportional decline in growth respiration rates was much greater. Stem area index (SAI) showed little trend along the transect, with declining tree stature at higher elevations being offset by an increased number of small trees. This trend in SAI is sensitive to changes in forest stature or size structure. In the context of rapid regional warming over the 21st century, such indirect, ecosystem‐level temperature responses are likely to be as important as the direct effects of temperature on maintenance respiration rates.     

Functional diversity of macromycete communities along an environmental gradient in a Mexican seasonally dry tropical forest

Macromycetes are important for ecosystem functioning due to their role in the nutrient cycling, and their function as pathogens and mutualists. Diversity metrics based on functional traits are robust predictors of ecosystem functionality since they incorporate an evolutionary and ecologic background. We examined diversity patterns of macrofungi using functional trait-based metrics of diversity along an altitudinal gradient in a seasonally dry tropical forest in southern Mexico. Our findings show that: (1) functional diversity varies with elevation, relating more to climatic variables than to vegetation structure; (2) functional diversity indexes exhibited contrasting patterns, so measures reflecting heterogeneity on trait abundance and niche complementarity tend to increase with elevation, whereas the measure of trait evenness decreases; and (3) functional diversity patterns depend on the type of functional trait considered and how they respond to environmental conditions. Our results indicate that functional diversity analyses help understanding of how macrofungal communities respond to environmental variation.     

Species composition,relative abundance and habitat association of small mammals along the altitudinal gradient of Jiren Mountain,Jimma, Ethiopia

To document the species composition, relative abundance and habitat association of small mammals, wet and dry season surveys were conducted along the altitudinal gradient of Jiren Mountain, Jimma area, Ethiopia. Sherman traps were used to capture small mammals from the six habitats: wetland, mixed plantation, open shrub, eucalyptus plantation, montane grassland and coffee plantation. The 393 trap nights, from the six habitat types, yielded 106 individual small mammals of tweleve species. The trapped rodents were Lophuromys flavopunctatus, Stenocephalemys albipes, Desmomys harringtoni, Mus mahomet, Lemniscomys barbarous, L. striatus, Tachyoryctes splendens, Mastomys natalensis and the insectivores Crocidura fumosa and C. turba. Two species of rodents Hystrix cristata and Helioscuirus gambianus were observed. Lophuromys flavopunctatus and S. albipes contributed 83.8% of the total capture. L. flavopunctatus, S. albipes and D. harringtoni were distributed in all habitats and gradients. T. splendens was captured from montane habitat, while the zebra mice were associated with the lower altitude habitats. Lophuromys flavopunctatus and M. natalensis extended their range deep into the coffee plantation habitats. Uncontrolled vegetation exploitation of the mountains for timber production and fire wood collection are the major threats. Conservation of the area to reduce the anthropogenic pressure is essential.     

Agricultural intensification in Brazil and its effects on land‐use patterns: an analysis of the 1975–2006 period

Does agricultural intensification reduce the area used for agricultural production in Brazil? Census and other data for time periods 1975–1996 and 1996–2006 were processed and analyzed using Geographic Information System and statistical tools to investigate whether and if so, how, changes in yield and stocking rate coincide with changes in cropland and pasture area. Complementary medium‐resolution data on total farmland area changes were used in a spatially explicit assessment of the land‐use transitions that occurred in Brazil during 1960–2006. The analyses show that in agriculturally consolidated areas (mainly southern and southeastern Brazil), land‐use intensification (both on cropland and pastures) coincided with either contraction of both cropland and pasture areas, or cropland expansion at the expense of pastures, both cases resulting in farmland stability or contraction. In contrast, in agricultural frontier areas (i.e., the deforestation zones in central and northern Brazil), land‐use intensification coincided with expansion of agricultural lands. These observations provide support for the thesis that (i) technological improvements create incentives for expansion in agricultural frontier areas; and (ii) farmers are likely to reduce their managed acreage only if land becomes a scarce resource. The spatially explicit examination of land‐use transitions since 1960 reveals an expansion and gradual movement of the agricultural frontier toward the interior (center‐western Cerrado) of Brazil. It also indicates a possible initiation of a reversed trend in line with the forest transition theory, i.e., agricultural contraction and recurring forests in marginally suitable areas in southeastern Brazil, mainly within the Atlantic Forest biome. The significant reduction in deforestation that has taken place in recent years, despite rising food commodity prices, indicates that policies put in place to curb conversion of native vegetation to agriculture land might be effective. This can improve the prospects for protecting native vegetation by investing in agricultural intensification.     

Biodiversity,dynamics, and impact of chakras on the Ecuadorian Amazon

Aims Deforestation and biodiversity loss are two alarming, closely related problems, and the main factors triggering changes in land use. Indigenous agricultural practices in the western Amazon Basin are known as chakras, and their structure and dynamics are seemingly optimal for forest management. However, the variability in tree species and the degree of forest recovery after abandonment is poorly documented in this agroforestry system (AFS). The goals of this study were: (i) to investigate whether the different AFSs (chakras) preserve similar levels of forest diversity, (ii) to determine the effect of transformation of mature forests (MF) to chakras, in particular, forest alpha and beta diversity levels, and (iii) to investigate whether native tree species recovery leads to the original forest structure following chakra abandonment.     

Post‐Soviet farmland abandonment,forest recovery,and carbon sequestration in western Ukraine

Land use is a critical factor in the global carbon cycle, but land‐use effects on carbon fluxes are poorly understood in many regions. One such region is Eastern Europe and the former Soviet Union, where land‐use intensity decreased substantially after the collapse of socialism, and farmland abandonment and forest expansion have been widespread. Our goal was to examine how land‐use trends affected net carbon fluxes in western Ukraine (57 000 km²) and to assess the region's future carbon sequestration potential. Using satellite‐based forest disturbance and farmland abandonment rates from 1988 to 2007, historic forest resource statistics, and a carbon bookkeeping model, we reconstructed carbon fluxes from land use in the 20th century and assessed potential future carbon fluxes until 2100 for a range of forest expansion and logging scenarios. Our results suggested that the low‐point in forest cover occurred in the 1920s. Forest expansion between 1930 and 1970 turned the region from a carbon source to a sink, despite intensive logging during socialism. The collapse of the Soviet Union created a vast, but currently largely untapped carbon sequestration potential (up to～150 Tg C in our study region). Future forest expansion will likely maintain or even increase the region's current sink strength of 1.48 Tg C yr^?1. This may offer substantial opportunities for offsetting industrial carbon emissions and for rural development in regions with otherwise diminishing income opportunities. Throughout Eastern Europe and the former Soviet Union, millions of hectares of farmland were abandoned after the collapse of socialism; thus similar reforestation opportunities may exist in other parts of this region.