Display omitted
•Amazon old-growth forest is seriously threatened due to land-use change.•Secondary forests re-growing represent an important reservoir of biodiversity.•Intensification of shifting ...cultivation reduces recovery of diversity and structure.•Agroforestry is an alternative to mitigate impacts by shifting cultivation.
Shifting cultivation is a traditional land-use system to ensure livelihood in the Northern Amazon. Here, we evaluated how intensification of shifting cultivation (SC) affects secondary forest recovery in the northern Amazon forest. To measure intensity of shifting cultivation, we used the number of previous SC cycles. We selected three study sites containing second-growth forest (SG) with different stand ages (5 and 10 years) after one, three or six SC cycles. Furthermore, we selected old-growth forest (OG) in each study site. In each selected SG and OG, three plots of 20 × 50 m were established, totalizing 63 plots in the study area. In each plot, all trees, palms and lianas with diameter at breast height ≥ 5 cm were tagged and identified to species level. We analyzed the effects of SC intensification and soil fertility on woody species richness, species composition and basal area using mixed effect models. Species richness and basal area, lower in SG than in OG, increased with regeneration time after abandonment, but reduced with intensification of SC. Community dissimilarities (Bray-Curtis distances) between OG and SG increased with the number of shifting cultivation cycles. Soil fertility differed between SG with different regeneration stages and reduced with number of SC cycles. We found that soil fertility and management intensity, i.e., number of previous SC cycles, explained pattern observed in richness, species composition and basal area equally good. Due to nutrient exports with crops and increasing nutrient leaching, soil fertility is expected to reduce with SC intensity. Therefore, our data indicate that intensification of SC reduces recovery of species richness, composition and basal area of SGs following productive periods. Thus, the intensification of SC reduces the resilience of SGs, turning this ancient form of land-use unsustainable. Environmental sustainability of SC may be achieved by extending fallow periods, limiting the maximum yield. To attend growing demands of indigenous and non-indigenous communities, we propose other alternatives of land-use such as permanent agroforestry systems.
Canga is the Brazilian term for the savanna-like vegetation harboring several endemic species on iron-rich rocky outcrops, usually considered for mining activities. Parkia platycephala Benth. and ...Stryphnodendron pulcherrimum (Willd.) Hochr. naturally occur in the cangas of Serra dos Carajás (eastern Amazonia, Brazil) and the surrounding forest, indicating high phenotypic plasticity. The morphological and physiological mechanisms of the plants' establishment in the canga environment are well studied, but the molecular adaptative responses are still unknown. To understand these adaptative responses, we aimed to identify molecular mechanisms that allow the establishment of these plants in the canga environment.
Plants were grown in canga and forest substrates collected in the Carajás Mineral Province. RNA was extracted from pooled leaf tissue, and RNA-seq paired-end reads were assembled into representative transcriptomes for P. platycephala and S. pulcherrimum containing 31,728 and 31,311 primary transcripts, respectively. We identified both species-specific and core molecular responses in plants grown in the canga substrate using differential expression analyses. In the species-specific analysis, we identified 1,112 and 838 differentially expressed genes for P. platycephala and S. pulcherrimum, respectively. Enrichment analyses showed that unique biological processes and metabolic pathways were affected for each species. Comparative differential expression analysis was based on shared single-copy orthologs. The overall pattern of ortholog expression was species-specific. Even so, we identified almost 300 altered genes between plants in canga and forest substrates with conserved responses in the two species. The genes were functionally associated with the response to light stimulus and the circadian rhythm pathway.
Plants possess species-specific adaptative responses to cope with the substrates. Our results also suggest that plants adapted to both canga and forest environments can adjust the circadian rhythm in a substrate-dependent manner. The circadian clock gene modulation might be a central mechanism regulating the plants' development in the canga substrate in the studied legume species. The mechanism may be shared as a common mechanism to abiotic stress compensation in other native species.
Tropical forests store large amounts of carbon and high biodiversity, but are being degraded at alarming rates. The emerging global Forest and Landscape Restoration (FLR) agenda seeks to limit global ...climate change by removing carbon dioxide from the atmosphere through the growth of trees. In doing so, it may also protect biodiversity as a free cobenefit, which is vital given the massive shortfall in funding for biodiversity conservation. We investigated whether natural forest regeneration on abandoned pastureland offers such cobenefits, focusing for the first time on the recovery of taxonomic diversity (TD), phylogenetic diversity (PD) and functional diversity (FD) of trees, including the recovery of threatened and endemic species richness, within isolated secondary forest (SF) fragments. We focused on the globally threatened Brazilian Atlantic Forest, where commitments have been made to restore 1 million hectares under FLR. Three decades after land abandonment, regenerating forests had recovered ~20% (72 Mg/ha) of the above‐ground carbon stocks of a primary forest (PF), with cattle pasture containing just 3% of stocks relative to PFs. Over this period, SF recovered ~76% of TD, 84% of PD and 96% of FD found within PFs. In addition, SFs had on average recovered 65% of threatened and ~30% of endemic species richness of primary Atlantic forest. Finally, we find positive relationships between carbon stock and tree diversity recovery. Our results emphasize that SF fragments offer cobenefits under FLR and other carbon‐based payments for ecosystem service schemes (e.g. carbon enhancements under REDD+). They also indicate that even isolated patches of SF could help to mitigate climate change and the biodiversity extinction crisis by recovering species of high conservation concern and improving landscape connectivity.
We investigated whether natural forest regeneration on abandoned pastureland offers such cobenefits, focusing for the first time on the recovery of taxonomic, phylogenetic diversity and functional diversity of trees, including the recovery of threatened and endemic species, within isolated secondary forest (SF) fragments. Our results emphasize that SF fragments offer cobenefits under FLR and other carbon‐based payments for ecosystem service schemes (e.g. carbon enhancements under REDD+). They also indicate that even isolated patches of SF could help to mitigate climate change and the biodiversity extinction crisis by recovering species of high conservation concern and improving landscape connectivity improving landscape connectivity.
Altitude and environmental variables such as edaphic properties are considered determinants of species distribution and community composition in mountain ecosystems. Here, we aimed to outline the ...effects of distinct mountain peaks, altitude and soil properties on community composition, species density, phylogenetic structure and diversity of angiosperm
páramo
communities from the Serra do Brigadeiro State Park, Minas Gerais, southeastern Brazil. For that, we identified all angiosperm species found in 300 plots (1 m × 1 m) from three mountain peaks, measured soil depth and analyzed soil fertility and texture in each plot. To reduce the number of soil variables and species composition, we computed principal coordinates based on soil properties and principal coordinates based on species-plot matrix for each plot. Furthermore, we computed the standard effect sizes of the mean phylogenetic pairwise distance and the mean nearest phylogenetic taxon distance for each plot to investigate differences in the degree of relatedness among coexisting species. We compared differences in response variables between peaks and modelled them in function of altitude and principle components of soil properties using mixed effect models. Species density and phylogenetic diversity differed between peaks, but, contrary to the previous findings, no relationships between species richness or phylogenetic diversity and altitude or soil properties were found, indicating that further investigations are necessary to understand the altitude-biodiversity relationship in Brazilian
páramo
vegetation. Community composition differed between peaks and depended on altitude, soil properties and interactions between them, indicating that upward shifting of bioclimatic conditions due to climate changes may alter communities of this ecosystem. Phylogenetic structure differed between peaks and was influenced by altitude and soil properties. As phylogenetic clustering increased with altitude, eventual upward movements of species in Brazilian
páramo
vegetation due to climate change may alter community composition and the degree of relatedness among coexisting species, increasing the risk of species from higher altitudes to disappear. Therefore, conservation priorities arise for higher landscape portions, where these high altitude species may find refuges.
Remote sensing technologies can play a fundamental role in the environmental assessment of open-cast mining and the accurate quantification of mine land rehabilitation efforts. Here, we developed a ...systematic geographic object-based image analysis (GEOBIA) approach to map the amount of revegetated area and quantify the land use changes in open-cast mines in the Carajás region in the eastern Amazon, Brazil. Based on high-resolution satellite images from 2011 to 2015 from different sensors (GeoEye, WorldView-3 and IKONOS), we quantified forests, cangas (natural metalliferous savanna ecosystems), mine land, revegetated areas and water bodies. Based on the GEOBIA approach, threshold values were established to discriminate land cover classes using spectral bands, the normalized difference vegetation index (NDVI), normalized difference water index (NDWI) and a light detection and range sensor (LiDAR) digital terrain model and slope map. The overall accuracy was higher than 90%, and the kappa indices varied between 0.82 and 0.88. During the observation period, the mining complex expanded, which led to the conversion of canga and forest vegetation to mine land. At the same time, the amount of revegetated area increased. Thus, we conclude that our approach is capable of providing consistent information regarding land cover changes in mines, with a special focus on the amount of revegetation necessary to fulfill environmental liabilities.
ABSTRACT The computation of phylogenetic diversity and phylogenetic community structure demands an accurately calibrated, high-resolution phylogeny, which reflects current knowledge regarding ...diversification within the group of interest. Herein we present the angiosperm phylogeny R20160415.new, which is based on the topology proposed by the Angiosperm Phylogeny Group IV, a recently released compilation of angiosperm diversification. R20160415.new is calibratable by different sets of recently published estimates of mean node ages. Its application for the computation of phylogenetic diversity and/or phylogenetic community structure is straightforward and ensures the inclusion of up-to-date information in user specific applications, as long as users are familiar with the pitfalls of such hand-made supertrees.
Impacted areas by iron mining may face challenges in the management of phosphate fertilization and reduced efficiency of rehabilitation practices, thus extending the time required for the ...rehabilitation of these areas. The objective of this study was to evaluate phosphorus (P) lability in soils of native forest and ferriferous canga areas (savanna vegetation above ironstone outcrops covering iron ore deposits) and in iron mine waste piles undergoing rehabilitation. Benches of the analysed waste pile differ in age of rehabilitation: as the initial rehabilitation stage (INI), we consider benches with fewer than 3 years of rehabilitation; the intermediate stage (INT) were benches with up to 5 years of rehabilitation; and the advanced rehabilitation stage (ADV) corresponds to benches with more than 8 years of rehabilitation activities. Organic and inorganic P fractions were analysed in these areas by chemical fractionation and were classified according to the degree of soil lability. The results show that in the canga environment, there was a predominance of inorganic fractions of moderate lability and moderate stability, with a strong dependency of the soil organic matter (SOM) on the P fractions, whereas there was a greater participation of the moderately labile organic fractions in the forest than in the canga. On the other hand, in the rehabilitation areas, there was an increase in the labile organic and inorganic fractions as the rehabilitation process advanced. The distribution of P in areas undergoing rehabilitation indicates that there is a tendency for P levels to resemble those of native environments, such as the forests.
To reduce the net losses of biodiversity and ecosystem services caused by iron ore mining in Brazil, mineland rehabilitation using native plant species is necessary. However, systematic knowledge ...about which plant species are the best candidates for mineland rehabilitation is lacking. Therefore, iron mining companies working on the Urucum Massif reintroduce as many native herb and shrub species as possible to achieve the rehabilitation of savanna vegetation communities. To this end, seeds are collected from nearby native ecosystems, and seedlings are rescued from logged areas or produced in a local nursery. Monitoring is necessary to assess the persistence of the reinstated communities and their similarity to natural reference conditions. Ideally, monitoring efforts should compare the floristic composition of the rehabilitating sites with that of natural reference ecosystems. Here, we compared sites that had undergone two or three years of rehabilitation after iron ore mining on the Urucum Massif, MS, Brazil, with native reference sites. The species composition as well as structural, taxonomic, and phylogenetic diversity indices were compared between the reference and rehabilitating sites. Despite the differences in species composition between the rehabilitating and reference sites, we found more than 50 native species and partial recovery of the vegetation structure in the rehabilitating sites. Furthermore, we detected similar levels of animal‐dispersed plant species at rehabilitating and reference sites. These environmental indicators indicate that trial‐and‐error approaches are indeed able to establish considerable native species diversity during mineland rehabilitation. Furthermore, the partial recovery of the vegetation structure suggests the gradual return of soil functions in the long term, and the presence of zoochorous species is expected to attract seed‐dispersing animals that enable gene flow as well as the arrival of additional plant species. Nevertheless, the high cover values of alien exotic species, which are negatively correlated with the diversity of the reinstated communities, endanger the success of mineland rehabilitation in the Urucum Massif, and effective control methods for invasive populations are required. These efforts should be accompanied by enrichment plantings to maintain the diversity of native plant communities at the rehabilitation sites and ongoing environmental monitoring.
The revegetation of areas impacted by iron mining may be hampered by a series of chemical and physical impediments exhibited by those areas. Physical problems, such as penetration resistance and ...steep slopes, may outweigh the chemical problems, such that both should be considered for soil recovery. This study aimed to evaluate the main soil attributes that are directly related to plant growth on areas affected by iron mining activities discussing possible solutions. For this purpose, chemical and physical attributes including penetration resistance on open pit mines, waste piles and native forest in Carajás Mineral Province were analysed. The results show that the open pits had low to medium levels of P and low levels of organic matter and of the micronutrients B, Zn and Cu. In the waste piles, the chemical parameters were less hindering than in the open pits. Soil penetration resistance in open pits was higher than in the waste piles and the forest; however, there was a reduction of up to 69% in soil resistance in open pits in the rainy season. The principal chemical problems observed in mine pits can be easily corrected, although the inclination of open pit slopes in combination with elevated soil density increase the risks of losses of fertilizers and seeds by runoff. Penetration resistance is the most serious problem for the development of plants in mine pits, although the use of irrigation water can help to maintain tolerable levels of resistance in soil for proper root growth of native species.
Context
Island Biogeography Theory and Habitat Amount Hypothesis postulate species richness and densities to increase with connectivity and habitat amount, while niche theory highlights the ...importance of environmental heterogeneity for species coexistence. Additional ecological niches in heterogeneous landscapes increase species richness and functional and phylogenetic diversity, but larger, less isolated habitats are expected to enlarge species densities by mass effects without effects on functional or phylogenetic diversity.
Objectives
We assessed the relative contribution of habitat amount, isolation and environmental heterogeneity on taxonomic, functional and phylogenetic diversity of the particular
canga
vegetation, i.e., rupestrian savannas associated to banded ironstone outcrops from the Carajás Massif, Eastern Amazon.
Methods
We sampled vegetation at 48 sampling points comprising different physiognomies from 5
canga
patches. Diversity measures were modelled as response variables in linear mixed models, using non-collinear predictors of habitat amount, isolation and environmental heterogeneity.
Results
Diversity and species composition differed among
canga
physiognomies, indicating that environmental filters segregate
canga
plant metacommunity in physiognomy-specific species pools. Landscape roughness, a proxy for heterogeneity on the landscape level, increases species densities and functional richness. Additionally, habitat amount was positively associated with the degree of phylogenetic relatedness and functional diversity in communities.
Conclusions
Our results suggest that configurational landscape heterogeneity increases the number of available ecological niches, while larger habitat amounts select for functionally and phylogenetically convergent species. These different underlying mechanisms need to be considered for management plans and reserve design for
canga
ecosystems, so that functional
canga
portions can be protected.
PDF
