Seasonally Dry Tropical Forests Research Articles

Chronic human disturbance affects plant trait distribution in a seasonally dry tropical forest

The effects of human disturbance on biodiversity can be mediated by environmental conditions, such as water availability, climate and nutrients. In general, disturbed, dry or nutrient-depleted soils areas tend to have lower taxonomic diversity. However, little is known about how these environmental conditions affect functional composition and intraspecific variability in tropical dry forests. We studied a seasonally dry tropical forest (SDTF) under chronic anthropogenic disturbance (CAD) along rainfall and soil nutrient gradients to understand how these factors influence the taxonomic and functional composition. Specifically we evaluated two aspects of CAD, wood extraction and livestock pressure (goat and cattle grazing), along soil fertility and rainfall gradients on shrub and tree traits, considering species turnover and intraspecific variability. In addition, we also tested how the traits of eight populations of the most frequent species are affected by wood extraction, livestock pressure, rainfall and soil fertility. In general, although CAD and environmental gradients affected each trait of the most widespread species differently, the most abundant species also had a greater variation of traits. Considering species turnover, wood extraction is associated with species with a smaller leaf area and lower investment in leaf mass, probably due to the indirect effects of this disturbance type on the vegetation, i.e. the removal of branches and woody debris clears the vegetation, favouring species that minimize water loss. Livestock pressure, on the other hand, affected intraspecific variation: the herbivory caused by goats and cattle promoted individuals which invest more in wood density and leaf mass. In this case, the change of functional composition observed is a direct effect of the disturbance, such as the decrease of palatable plant abundance by goat and cattle herbivory. In synthesis, CAD, rainfall and soil fertility can affect trait distribution at community and species levels, which can have significant implications for the ecosystem functioning of SDTF under increasing levels of disturbance, climate change and soil nutrient depletion.

Plant cover and hydrological response in a seasonally dry tropical forest (SDTF)

The scarcity of information on the processes of rainfall-flow limits understanding of the hydrology of dry regions of the world. In order to minimise the problem, this study was developed to investigate the influence of the characteristics of rainfall events and plant cover on the effective precipitation (Pe) in a seasonally dry tropical forest (SDTF) in the Northeast of Brazil. The study was carried out in two paired watersheds, one with SDTF under regeneration for 35 years (CR35) and the other under thinned SDTF for 5 years (TC). A historical series of five years (2009-2013) was analysed, with a total of 203 rainfall events, where only those rainfall events that generated a Pe > 1.0 mm were considered. CR35 had a greater number of Pe events (47) than TC (35). Rainfall depth and intensity were the factors that best explained the effective precipitation under both types of vegetation cover. The influence of herbaceous vegetation on the reduction of surface runoff was demonstrated by the smaller runoff depth and the greater potential for soil water storage in the watershed under thinned Caatinga. This fact leads to the conclusion that the technique of thinning is suitable management for Caatinga vegetation, and is capable of promoting the retention of soil water.

Estimating synchronous demographic changes across populations using hABC and its application for a herpetological community from northeastern Brazil.

Many studies propose that Quaternary climatic cycles contracted and/or expanded the ranges of species and biomes. Strong expansion-contraction dynamics of biomes presume concerted demographic changes of associated fauna. The analysis of temporal concordance of demographic changes can be used to test the influence of Quaternary climate on diversification processes. Hierarchical approximate Bayesian computation (hABC) is a powerful and flexible approach that models genetic data from multiple species, and can be used to estimate the temporal concordance of demographic processes. Using available single-locus data, we can now perform large-scale analyses, both in terms of number of species and geographic scope. Here, we first compared the power of four alternative hABC models for a collection of single-locus data. We found that the model incorporating an a priori hypothesis about the timing of simultaneous demographic change had the best performance. Second, we applied the hABC models to a data set of seven squamate and four amphibian species occurring in the Seasonally Dry Tropical Forests (Caatinga) in northeastern Brazil, which, according to paleoclimatic evidence, experienced an increase in aridity during the Pleistocene. If this increase was important for the diversification of associated xeric-adapted species, simultaneous population expansions should be evident at the community level. We found a strong signal of synchronous population expansion in the Late Pleistocene, supporting the increase of the Caatinga during this time. This expansion likely enhanced the formation of communities adapted to high aridity and seasonality and caused regional extirpation of taxa adapted to wet forest.

Molecular data and distribution dynamics indicate a recent and incomplete separation of manakins species of the genus Antilophia (Aves: Pipridae) in response to Holocene climate change

To determine a hypothetical scenario that accounts for the diversification of the two species of the genus Antilophia, we conducted multilocus molecular comparisons and species distribution modeling for the two taxa, which have distinct male plumage coloration patterns and allopatric geographic distributions, despite the high degree of genetic similarity indicated by recent studies. Three mitochondrial and three nuclear fragments were analyzed. The results indicate clear differences in the genetic diversity of the two species, but with ample sharing of haplotypes in all the markers analyzed, reflecting the absence of reciprocal monophyly, presumably due to the relatively recent and still incomplete separation of the two species. The paleoclimatic distribution models, together with the observed genetic profile indicate a recent process of divergence by geographic isolation in the ancestral populations of the two species. This scenario coincides with the recent climatic events of the South American dry diagonal, which involves the gallery forests of the Cerrado biome and the cloud forest enclaves of the seasonal tropical dry forest of the Caatinga between the late Pleistocene and the mid Holocene.

Janet I. Sprent.

Janet I. Sprent.

Biological Invasion Influences the Outcome of Plant-Soil Feedback in the Invasive Plant Species from the Brazilian Semi-arid.

Plant-soil feedback is recognized as the mutual interaction between plants and soil microorganisms, but its role on the biological invasion of the Brazilian tropical seasonal dry forest by invasive plants still remains unclear. Here, we analyzed and compared the arbuscular mycorrhizal fungi (AMF) communities and soil characteristics from the root zone of invasive and native plants, and tested how these AMF communities affect the development of four invasive plant species (Cryptostegia madagascariensis, Parkinsonia aculeata, Prosopis juliflora, and Sesbania virgata). Our field sampling revealed that AMF diversity and frequency of the Order Diversisporales were positively correlated with the root zone of the native plants, whereas AMF dominance and frequency of the Order Glomerales were positively correlated with the root zone of invasive plants. We grew the invasive plants in soil inoculated with AMF species from the root zone of invasive (I changed) and native (I unaltered) plant species. We also performed a third treatment with sterilized soil inoculum (control). We examined the effects of these three AMF inoculums on plant dry biomass, root colonization, plant phosphorous concentration, and plant responsiveness to mycorrhizas. We found that I unaltered and I changed promoted the growth of all invasive plants and led to a higher plant dry biomass, mycorrhizal colonization, and P uptake than control, but I changed showed better results on these variables than I unaltered. For plant responsiveness to mycorrhizas and fungal inoculum effect on plant P concentration, we found positive feedback between changed-AMF community (I changed) and three of the studied invasive plants: C. madagascariensis, P. aculeata, and S. virgata.

Corticolous myxomycetes assemblages in a seasonally dry tropical forest in Brazil

Corticolous myxomycetes are a distinct ecological group consisting of species typically associated with the outer bark surface of living trees. The current study aimed to characterize the community structure of corticolous myxomycetes and their associated trees, analyzing the influence of geographic distance, bark pH, and tree diameter on myxomycete assemblages in a Neotropical Seasonal Dry Tropical Forest (SDTF) in Brazil. The myxomycete community composition significantly varied with the increase of the geographic distance between the studied plots, and tree bark pH was able to explain the species composition exclusively recorded in one of the three transects.

The role of climate and environmental variables in structuring bird assemblages in the Seasonally Dry Tropical Forests (SDTFs).

Understanding the processes that influence species diversity is still a challenge in ecological studies. However, there are two main theories to discuss this topic, the niche theory and the neutral theory. Our objective was to understand the importance of environmental and spatial processes in structuring bird communities within the hydrological seasons in dry forest areas in northeastern Brazil. The study was conducted in two National Parks, the Serra da Capivara and Serra das Confusões National Parks, where 36 areas were sampled in different seasons (dry, dry/rainy transition, rainy, rainy/dry transition), in 2012 and 2013. We found with our results that bird species richness is higher in the rainy season and lower during the dry season, indicating a strong influence of seasonality, a pattern also found for environmental heterogeneity. Richness was explained by local environmental factors, while species composition was explained by environmental and spatial factors. The environmental factors were more important in explaining variations in composition. Climate change predictions have currently pointed out frequent drought events and a rise in global temperature by 2050, which would lead to changes in species behavior and to increasing desertification in some regions, including the Caatinga. In addition, the high deforestation rates and the low level of representativeness of the Caatinga in the conservation units negatively affects bird communities. This scenario has demonstrated how climatic factors affect individuals, and, therefore, should be the starting point for conservation initiatives to be developed in xeric environments.

Small Celastraceae and Polygonaceae twigs from the Upper Cenozoic (Ituzaingó Formation) of the La Plata Basin, Argentina

Two new wood types from the Late Cenozoic of the Ituzaingó Formation, La Plata Basin, Northeast Argentina add to our knowledge of South American Cenozoic plants. The materials were preserved by siliceous cellular permineralization, and they were prepared for microscopic examination by surface polishing and in thin sections. The anatomy of these new species was described. The relationship and comparison with the nearest living relatives (NLRs) are discussed. Maytenoxylon perforatum Franco gen. and sp. nov. is described as the first fossil wood referable to Celastraceae from South America. This new fossil species is related to extant Maytenus Molina. The other fossil twig, Ruprechtioxylon breae Franco sp. nov., has features of the Polygonaceae family and particularly resembles the extant specie Ruprechtia laxiflora Meisn. The occurrence of these fossil woods in south-eastern South America suggests that a relatively warm and dry to seasonally dry climate prevailed over this region of Gondwana during the Upper Cenozoic. It also provides new evidence for the hypothesis of the more wide distribution of Seasonally Dry Tropical Forest (SDTF) during the Upper Cenozoic.

The roles of rainfall, soil properties, and species traits in flowering phenology along a savanna-seasonally dry tropical forest gradient

We investigated flowering phenology in a semiarid macroclimate along an environmental gradient encompassing neotropical savanna, transition, and seasonally dry tropical forest (SDTF) areas in the Chapada Diamantina Mountains, northeastern Brazil. We expected to find divergence in flowering patterns between the plant communities studied that would be explained by distinct functional traits selected by differences in rainfall volumes and soil properties. Bud and flower productions were monitored in 809 individuals between January 2010 and March 2012. The savanna exhibited a continuous flowering pattern, while the transition and SDTF areas showed seasonal flowering associated with rainfall. Environmental variables and plant traits (wood densities, water potentials, and water storage capacities) were related to the observed flowering strategies of woody species. The high diversity of functional groups in the savanna was determined by higher plant water potentials that were related to low wood densities and the availability of soil water. The role of rainfall, especially the rainfall volumes during the dry season, is critical in defining different flowering patterns at the community level. The physical properties of the soil selected the presence of species with distinct water-use strategies (low wood density species in savanna areas, and high wood density species in the transition zone and forest), which in turn affected their flowering.

Reproductive phenology of useful Seasonally Dry Tropical Forest trees: Guiding patterns for seed collection and plant propagation in nurseries

The propagation in nurseries of native plant species potentially useful for agroforestry, silvopastoral and restoration programs is hindered by an inadequate supply of high quality seed. Limitations in our knowledge on the phenological patterns of native species result in the lack of efficient collecting protocols. Here we analyze the reproductive phenology of 14 native tree species from Seasonally Dry Tropical Forest (SDTF) that are widely used in reforestation and restoration programs. We conducted monthly observations during five years through a community-based monitoring program in two conservation areas within the Zicuirán-Infiernillo Biosphere Reserve (West Mexico) to assess the flowering and fruiting phenology of 149 marked trees (7–20 trees per species). For each species we described the phenophase intensity, duration, seasonality, synchrony and frequency. We related the intensity of reproductive phenology to climatic variables (photoperiod, precipitation and temperature). We identified three main phenological strategies of SDTF species that differ in timing and climatic triggers: (1) flowering and fruiting exclusively in the rainy season; (2) flowering in the rainy season and fruiting in the dry season; and (3) flowering and fruiting exclusively in the dry season. For each phenological strategy we make recommendations of optimal collecting seeds schedules. The community-based monitoring program, which involves the participation of local social actors, guaranteed the success of long-term phenological monitoring. Our study provides valuable information on both the inter-annual and inter-specific variation of the phenological patterns of tree species of forestry interest, and demonstrates that qualitative descriptions of population-level phenological attributes is an essential input to develop adaptive management programs.

Will seasonally dry tropical forests be sensitive or resistant to future changes in rainfall regimes?

Seasonally dry tropical forests (SDTF) are located in regions with alternating wet and dry seasons, with dry seasons that last several months or more. By the end of the 21st century, climate models predict substantial changes in rainfall regimes across these regions, but little is known about how individuals, species, and communities in SDTF will cope with the hotter, drier conditions predicted by climate models. In this review, we explore different rainfall scenarios that may result in ecological drought in SDTF through the lens of two alternative hypotheses: 1) these forests will be sensitive to drought because they are already limited by water and close to climatic thresholds, or 2) they will be resistant/resilient to intra- and inter-annual changes in rainfall because they are adapted to predictable, seasonal drought. In our review of literature that spans microbial to ecosystem processes, a majority of the available studies suggests that increasing frequency and intensity of droughts in SDTF will likely alter species distributions and ecosystem processes. Though we conclude that SDTF will be sensitive to altered rainfall regimes, many gaps in the literature remain. Future research should focus on geographically comparative studies and well-replicated drought experiments that can provide empirical evidence to improve simulation models used to forecast SDTF responses to future climate change at coarser spatial and temporal scales.

Arbuscular mycorrhizal fungal community assembly in the Brazilian tropical seasonal dry forest

IntroductionHere, we compare the arbuscular mycorrhizal fungal (AMF) community composition in soils from the root zone of the exotic invasive species Prosopis juliflora (EXO soils) and soils from the root zone of the native species Mimosa tenuiflora (NAT soils) from five locations in the Brazilian tropical seasonal dry forest, Paraíba, Brazil, using morphological analyses.ResultsAMF community composition in EXO and NAT soils were dissimilar. Available phosphorus, diversity index, spore abundance, and species richness were the main factors differing between the EXO and NAT soils. In general, the most dominant order present in the soils were Glomerales (44.8%) and Gigasporales (41.4%). The most abundant AMF genus in all studied soils was Funneliformis.ConclusionsDifferences in AMF community composition were associated with (1) differences in the dominant plant species (P. juliflora vs. M. tenuiflora) and (2) changes in soil chemical factors (soil, pH, total organic carbon, total nitrogen, and available P) in EXO soils. These results contribute to a deeper view of the AMF communities in exotic soils and open new perspectives for ecological processes involving AMF species and exotic plant species in the Brazilian tropical seasonal dry forest.

Temporal changes in tree community structure and richness in a seasonally dry tropical forest in Minas Gerais, southeastern Brazil

Seasonally Dry Tropical Forests (SDTF) are gaining recognition as a habitat of global conservation significance. However, these forests often occur on rich soils, and are therefore prone to disturbance by agricultural activities. Across their range, many SDTFs are in various stages of regeneration, although little is known about their regeneration dynamics and temporal change in general. To fill this knowledge gap, we studied the changes in species diversity and community structure of an SDTF tree community with a history of past selective logging located in northern Minas Gerais, Brazil. We hypothesized an increase in species diversity and biomass-related parameters, along with a reduction in stem density for the community after five years of regeneration. In 2005, we measured all trees (diameter >= 3.18 cm at 1.3 m) within twenty 20 x 20 m (400 m(2)) plots in the patch, and we remeasured the trees in 2010. Between the two censuses, we found no significant changes in species richness and diversity, suggesting that species accumulation had leveled out. However, we found significant gains in tree basal area and recruitment, suggesting continual regeneration. Diameter class distributions of the five most abundant tree species showed similar patterns. We conclude that past disturbances can have ongoing effects on SDTF vegetation, although inter-annual variations may also play a regulatory role on community dynamics.

Temporal vegetation changes in a seasonally dry tropical forest enclave in an ecotonal region between savanna and semiarid zones of Brazil

Seasonally dry tropical forests (SDTFs) comprise a globally significant biome for biodiversity and conservation. Geographically, Brazilian SDTFs are primarily located within the country’s semiarid region (the Caatinga domain) in north-eastern Brazil. However, poorly studied and disjunct SDTF enclaves can occur within other regions, inside other Brazilian phytogeographical domains of vegetation such as savannas (i.e. the Cerrado domain) in central Brazil. These enclaves provide an opportunity to examine natural and non-anthropogenic edge effects on such vegetation. In 2007 and 2014, we studied a 120-ha SDTF enclave in the municipality of Januária in northern Minas Gerais, Brazil, to understand its (1) floristic composition and soil correlates, and (2) temporal variations in diversity, structure and dynamics. Three sets of 10 400-m2 plots were used to compare the vegetation at 0 m (edge), 100 m (middle) and 200 m (inner) into the forest. The edge plots were compositionally dissimilar from the interior plots because of soil fertility and soil textural gradients. Paradoxically also, the inner plots exhibited less stable vegetation-dynamic patterns than did both the middle and the edge plots, possibly owing to natural temporal fluctuations in vegetation dynamics. Overall, the SDTF enclave exhibited high diversity and structural complexity, likely because of its geographical setting within a matrix of savanna. These results highlight a conservation priority for further studies on such SDTF enclaves throughout their range.

Belowground Carbon and Nitrogen on a Thinned and Un-Thinned Seasonally Dry Tropical Forest

The aim of this study was to quantify the dynamics of herbaceous biomass and fine root productivity, and their relationship to stocks of carbon and nitrogen, in the Vertisols of two adjacent watersheds of a seasonally dry tropical forest (SDTF) under two different types of ground cover. The two watersheds are located in the county of Iguatu in the State of Ceará, Brazil. The control watershed of 2.1 ha, has been under regeneration for 35 years (RC35), while the second watershed (1.1 ha) was subjected to thinning for a period of 5 years (TC5). The sampled variables were herbaceous shoot biomass, fine roots, gravimetric moisture, the isotope δ13C (‰), total soil carbon (TSC) and total nitrogen (TN) in the 0 - 20, 20 - 40 and 40 - 60 cm layers, between April 2013 and March 2014. To quantify herbaceous shoot biomass, samples were taken monthly. For TSC and TN, the campaigns were held every two months. The data underwent analysis of means and were compared by t-test (p 5, there was an increase in the stocks of TSC and TN of 151 and 137% respectively in the 40 - 60 cm layer, in relation to RC35. The implementation of thinning in a SDFT is seen as a management alternative to be considered in sustainability programs in the semi-arid region, contributing to maximising the production of herbaceous forage for feeding large and small ruminants, and for bee pasture, in addition to increasing the stock of carbon in the soil of SDFT and reducing global warming.

Genetic diversity of Enterolobium cyclocarpum in Colombian seasonally dry tropical forest: implications for conservation and restoration

Enterolobium cyclocarpum is a characteristic legume tree species of seasonally dry tropical forests (SDTFs) of Mesoamerica and northern South America typically used in silvopastoral and agroforestry systems. Remaining populations of E. cyclocarpum in Colombia are severely fragmented owing to the highly degraded state of SDTF in the country, posing threats to both their in situ persistence and their usefulness as seed sources for future planting efforts. We genotyped E. cyclocarpum populations at nine sampling sites across a latitudinal gradient of SDTF in Colombia by means of eight nSSR markers to elucidate the species diversity distribution in the country. Our data suggest that a deep divide seems to have existed between Caribbean and Andean populations of E. cyclocarpum in Colombian SDTF that may date back to the last glacial maximum (~21,000 BP), or longer. However, we only found evidence of genetic differentiation between trees from the southern Cauca River valley and populations at more northern locations. All the latter populations showed signs of admixture which may be the result of human-influenced movement of germplasm, particularly after the introduction of cattle by European settlers. Most of the sampled sites showed heterozygosity scores close to Hardy–Weinberg expectations. Only the three southern-most populations displayed significantly positive values of inbreeding coefficient, potentially affecting their in situ maintenance and their use as seed sources. Based on our findings we identify priority areas for the in situ conservation of remaining E. cyclocarpum populations, and propose a strategy for sourcing of appropriate planting material for use in future tree planting efforts.

Symbiosis with AMF and leaf Pi supply increases water deficit tolerance of woody species from seasonal dry tropical forest

In seasonal dry tropical forests, plants are subjected to severe water deficit, and the arbuscular mycorrhizal fungi (AMF) or inorganic phosphorus supply (Pi) can mitigate the effects of water deficit. This study aimed to assess the physiological performance of Poincianella pyramidalis subjected to water deficit in combination with arbuscular mycorrhizal fungi (AMF) and leaf inorganic phosphorus (Pi) supply. The experiment was conducted in a factorial arrangement of 2 water levels (+H2O and −H2O), 2 AMF levels (+AMF and −AMF) and 2Pi levels (+Pi and −Pi). Leaf primary metabolism, dry shoot biomass and leaf mineral nutrients were evaluated. Inoculated AMF plants under well-watered and drought conditions had higher photosynthesis and higher shoot biomass. Under drought, AMF, Pi or AMF+Pi plants showed metabolic improvements in photosynthesis, leaf biochemistry and higher biomass compared to the plants under water deficit without AMF or Pi. After rehydration, those plants submitted to drought with AMF, Pi or AMF+Pi showed a faster recovery of photosynthesis compared to treatment under water deficit without AMF or Pi. However, plants under the drought condition with AMF showed a higher net photosynthesis rate. These findings suggest that AMF, Pi or AMF+Pi increase the drought tolerance in P. pyramidalis, and AMF associations under well-watered conditions increase shoot biomass and, under drought, promoted faster recovery of photosynthesis.

Revealing areas of high nature conservation importance in a seasonally dry tropical forest in Brazil: Combination of modelled plant diversity hot spots and threat patterns

The Caatinga biome has been identified as one of the important wilderness areas on earth. However, less than 1% of the region is under strictly legal protection although Seasonally Dry Tropical Forests (SDTFs) are globally highly endangered. There is an urgent need to increase the understanding of diversity pattern and threaten status of Caatinga plant species to preserve the unique biodiversity and protect endangered species. Species distribution modelling (SDM) can support strategic decisions in nature conservation for poorly researched tropical regions. This study provides the first highly representative, spatially explicit overview of plant diversity and threat status for the entire Caatinga, a semi-arid area in Northeast Brazil. For this purpose, we developed (a) a stacked species distribution modelling (S-SDM) approach to predict quantitatively floristic species richness and patterns of threatened plant species and (b) a combined approach of diversity hot spots and hubs of threatened species to derive conservation importance units (CIU) to contribute to improved nature reserve management. We applied the modelling technique MaxEnt to establish predictive distribution models with 22 uncorrelated predictors including climate, topography, solar radiation and soil information at a high spatial resolution of 30 arc-seconds (approx. 1km). Spatial patterns of species richness and threat status were derived by stacking 1062 plant species and 27 endangered species, respectively. These outputs were compared to two levels of protected areas (Brazilian and international standards) and intensive human land use patterns to define a set of recommendations for conservation management. Our complementary S-SDM approach showed that our predicted CIUs covered an area of 24% across the entire biome, whereas only 7% of the Caatinga is currently protected based on the Brazilian standards. We found that apart from an excellent overlap of 38% between CIUs and the current protected areas, a substantial proportion of CIUs (89%) was predicted outside the existing reserve network. Moreover, our findings enable targeted surveys to be done in order to enhance conservation efforts and ensure the efficient use of available resources in this poorly studied tropical region. Future upcoming local and regional studies could focus on a multi-taxonomic approach including e.g. insects, reptiles or mammals as a holistic perspective towards biodiversity conservation.

Vegetation structure determines insect herbivore diversity in seasonally dry tropical forests

Vegetation structure can often determine insect herbivore fauna in forests, but this mechanism has been demonstrated in seasonally dry tropical forests (SDTFs) only at small spatial scales. In this study we evaluated the effects of the geographical location of SDTFs and vegetation structure on insect herbivore communities (leaf-chewing and sap-sucking guilds) in three Brazilian ecoregions (Cerrado, Cerrado/Caatinga transition, and Caatinga). We tested the following predictions: (1) insect herbivore species composition, richness, abundance and beta diversity differ among forests in different ecoregions; (2) insect richness, abundance and beta diversity are positively related to tree richness and density; (3) spatial turnover of species is the primary mechanism that generates herbivorous insect β-diversity in different ecoregions, and is positively influenced by tree richness. The composition, richness, and abundance of herbivorous insects differed over SDFs along the gradient of Cerrado and Caatinga. Both herbivore guilds responded positively to tree richness. Tree density only determined the richness and abundance of sap-sucking herbivores. Insect β-diversity was similar among Cerrado and transition areas, but lower in Caatinga itself; β-diversity was also positively affected by tree richness. Species turnover, as opposed to nestedness, was the main mechanism generating β-diversity, but itself was not related to tree richness. We demonstrate in this study the importance of landscape diversity and availability of local resources for herbivorous insect communities, and we emphasize the importance of SDTF conservation in different ecoregions as a result of species turnover.