A framework for deriving measures of chronic anthropogenic disturbance: Surrogate, direct, single and multi-metric indices in Brazilian Caatinga

Arnán, Xavier; Leal, Inara R.; Tabarelli, Marcelo; Andrade, J. F.; Barros, Maria Fabíola; Câmara, Talita; Jamelli, Davi; Knoechelmann, Clarissa Mendes; Menezes, Tatiane Almeida de; Menezes, Artur G.S.; Oliveira, Fernanda M. P.; Paula, Alexandre Souza de; Pereira, Silvia; Rito, Kátia F.; Sfair, Júlia Caram; Siqueira, Felipe F. S.; Souza, Danielle G.; Specht, Maria Joana; Vieira, Ligia A.F.; Arcoverde, Gabriela B.; Andersen, Alan N.

doi:10.1016/j.ecolind.2018.07.001

Cited by 74 publications

(85 citation statements)

References 41 publications

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“…The overall disturbance index varies from 0 (zero values for all component metrics) to 100 (maximum values of all component disturbance metrics) (for more details on chronic disturbance index see Arnan et al . ).…”

Section: Methodsmentioning

confidence: 97%

Human disturbance promotes herbivory by leaf‐cutting ants in the Caatinga dry forest

et al. 2018

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Anthropogenic disturbances are known to modify plant–animal interactions such as those involving the leaf‐cutting ants, the most voracious and proliferating herbivore across human‐modified landscapes in the Neotropics. Here, we evaluate the effect of chronic anthropogenic disturbance (e.g., firewood collection, livestock grazing) and vegetation seasonality on foraging area, foliage availability in the foraging area, leaf consumption and herbivory rate of the leaf‐cutting ant Atta opaciceps in the semiarid Caatinga, a mosaic of dry forest and scrub vegetation in northeast Brazil. Contrary to our initial expectation, the foraging area was not affected by either disturbance intensity or the interaction between season and disturbance intensity. However, leaf consumption and herbivory rate were higher in more disturbed areas. We also found a strong effect of seasonality, with higher leaf consumption and herbivory rate in the dry season. Our results suggest that the foraging ecology of leaf‐cutting ants is modulated by human disturbance and seasonality as these two drivers affect the spectrum and the amount of resources available for these ants in the Caatinga. Despite the low productivity of Caatinga vegetation, the annual rates of biomass consumption by A. opaciceps are similar to those reported from other leaf‐cutting ants in rain forests and savannas. This is made possible by maintaining high foraging activity even in the peak of the dry season and taking benefit from any resource available, including low‐quality items. Such compensation highlights the adaptive capacity of LCA to persist or even proliferate in human‐modified landscapes from dry to rain forests.

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Section: Methodsmentioning

confidence: 97%

Human disturbance promotes herbivory by leaf‐cutting ants in the Caatinga dry forest

et al. 2018

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“…To estimate intensity across a gradient of human‐induced disturbance, we adopted a multimetric disturbance index (sensu Arnan et al, ), which was computed from the integration of three different indices for the main types of CAD affecting the Caatinga dry forest: people pressure , livestock pressure , and wood extraction . The indices were computed using the formula originally proposed by Legendre and Legendre () to get an overall level of land‐use intensity.

I = \frac{\sum_{i = 1}^{n} false(y_{i} - y_{min} false) / false(y_{max} - y_{min} false)}{n} \times 100

where I is the disturbance intensity index, yi is the observed value for a given disturbance metric in plot i , ymin is the minimum observed value for the disturbance metric considering all plots, ymax is the maximum observed value for the disturbance metric considering all plots, and n is the number of individual disturbance metrics included in the index.…”

Section: Methodsmentioning

confidence: 99%

Functional organization of woody plant assemblages along precipitation and human disturbance gradients in a seasonally dry tropical forest

et al. 2019

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Chronic anthropogenic disturbances (CAD) and rainfall are important drivers of plant community assembly, but little is known about the role played by inter‐ and intraspecific trait variation as communities respond to these pervasive forces. Here, we examined the hypothesis that lower precipitation and higher CAD reduce both intra‐ and interspecific trait variation in Caatinga dry forests. We sampled woody plants across 15 plots along precipitation and CAD gradients and measured resource‐use traits. The effects of precipitation and CAD on RaoQ functional diversity were decomposed into species turnover and intraspecific variability. We used “T‐statistics” to assess the trait sorting from the regional pool to local communities (i.e., external filtering), and within‐community forces leading to low trait overlap (i.e., internal filtering) at individual and species levels. Intraspecific variability explained at least one‐third of the total trait variation and 46% of variation in multitrait diversity across communities. Increasing disturbance reduced multitrait diversity, while precipitation affected some particular traits, such as wood density. Overall, precipitation determined species sorting across communities, while disturbance relaxed internal filters, leading to higher trait overlap within communities due to higher intraspecific variability. Our results suggest that the woody Caatinga flora contains a substantial amount of both inter‐ and intraspecific trait variation. This variation is not randomly distributed within and across communities, but varies according to rainfall conditions and disturbance intensity. These findings reinforce the emerging idea that human disturbances can reorganize plant communities at multiple scales and highlight trait variability as a key biological asset for the resilience of dry forests.

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“…Livestock pressure and wood extraction were directly measured in the field through assessments of goat trail length, goat dung frequency, cattle dung frequency, live wood extraction (stem cuts) and coarse woody debris extraction (litter) within each plot (Arnan et al 2018a). Nontimber products were estimated via three variables related to the accessibility and influence of human activities in each plot: proximity to the nearest house, proximity to the nearest road and number of people living in each house that engage in the practices described above (Arnan et al 2018a). These three indirect disturbance indicators were integrated into a single metric -people pressure -by means of PCA analysis (Arnan et al 2018a).…”

Section: Characterization Of Disturbance and Rainfall Gradientsmentioning

confidence: 99%

“…These three indirect disturbance indicators were integrated into a single metric -people pressure -by means of PCA analysis (Arnan et al 2018a). For more details on the characterization of disturbance and calculation of the global multimetric index, Arnan et al (2018a). The compound index ranged from 2 to 58 (from the lowest to the highest level of disturbance) among the plots.…”

Section: Characterization Of Disturbance and Rainfall Gradientsmentioning

confidence: 99%

“…Caatinga is a typical seasonally dry tropical forest that supports a high density of EFN-bearing plants (Melo et al 2010, Leal et al 2017. However, the Caatinga is continuously degraded by human activities such as wood extraction, overgrazing by livestock (cattle and goats) and collection of non-timber forest products (Albuquerque et al 2007, Ramos and Albuquerque 2012, Ribeiro et al 2015, Arnan et al 2018a). However, the Caatinga is continuously degraded by human activities such as wood extraction, overgrazing by livestock (cattle and goats) and collection of non-timber forest products (Albuquerque et al 2007, Ramos and Albuquerque 2012, Ribeiro et al 2015, Arnan et al 2018a).…”

Section: Introductionmentioning

confidence: 99%

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Anthropogenic disturbance and rainfall variation threaten the stability of plant–ant interactions in the Brazilian Caatinga

et al. 2019

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Climate change is projected to exacerbate the effects of anthropogenic disturbance, with negative impacts on ecosystem stability and functioning. We evaluate the additive and combined effects of chronic anthropogenic disturbance (CAD) and rainfall variation on the temporal stability of mutualistic EFN-bearing plant-ant networks in a Caatinga dry forest. We evaluated whether changes in the stability of these interactions are driven by changes in the stability of the communities of partners involved and/or in ant behavior. We sampled EFN-bearing plant-ant networks in sixteen 20 × 20 m plots distributed across CAD and rainfall gradients. The stability of EFN-bearing plant and attendant-ant communities were measured as the inverse of temporal differences in their community structure and composition. We also computed the stability of EFN-bearing plant-ant networks by measuring the inverse of temporal differences in network specialization metrics. We found that, in general, the structure and composition of plant and ant interacting communities were similarly stable along both environmental gradients. Only CAD and its interaction with rainfall affected the temporal stability of EFN-bearing plant diversity, which declined as CAD increased, with a more pronounced relationship in wetter areas. However, variation in levels of CAD and, to a lesser extent, rainfall greatly modulated the stability of EFN-bearing plantant network specialization. CAD reduced the stability of network generality (specialization at the ant level), an effect that was much stronger in wetter areas. Meanwhile, the stability in network vulnerability (specialization at the plant level) decreased with the increase of CAD and the decrease of rainfall levels. Finally, there was a trend of decreasing stability in specialization of the overall network with increasing CAD. Our results suggest that changes in the structure of interaction networks are mainly driven by a switch in ant behavior rather than by changes in the structure and composition of plant and ant communities between years.

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A framework for deriving measures of chronic anthropogenic disturbance: Surrogate, direct, single and multi-metric indices in Brazilian Caatinga

Cited by 74 publications

References 41 publications

Human disturbance promotes herbivory by leaf‐cutting ants in the Caatinga dry forest

Human disturbance promotes herbivory by leaf‐cutting ants in the Caatinga dry forest

Functional organization of woody plant assemblages along precipitation and human disturbance gradients in a seasonally dry tropical forest

Anthropogenic disturbance and rainfall variation threaten the stability of plant–ant interactions in the Brazilian Caatinga

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