Drastic impoverishment of the soil seed bank in a tropical dry forest exposed to slash-and-burn agriculture

Bezerra, Jakelyne S.; Arroyo‐Rodríguez, Víctor; Tavares, Jonathan M.; Leal, Adrielle; Leal, Inara R.; Tabarelli, Marcelo

doi:10.1016/j.foreco.2022.120185

Cited by 25 publications

(8 citation statements)

References 67 publications

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“…Considering the socioecological context of the Caatinga, with the prevalence of subsistence farming, we argue that this transition of dry forests naturally dominated by single-stem tree species towards deserts (i.e. bare soils) or vegetation type dominated by multi-stemmed shrubs (here defined as shrubland) is a response by the forest ecosystems to a continuous exposition to conversion into pastures 17 , 52 , slash-and-burn agriculture 53 , shifting cultivation 27 , 54 , coppicing 23 , and browsing by livestock 48 , 55 , as well as the exploitation of forest products. Such an alternative successional trajectory is not exclusively related to tree species replacement by shrub species, but also by the predominance of tree species occurring as multi-stem shrub-sized individuals, as is already occurring with almost all dominant tree species in human-modified Caatinga landscapes 56 – 58 .…”

Section: Discussionmentioning

confidence: 99%

Human disturbance is the major driver of vegetation changes in the Caatinga dry forest region

Araujo,

Canassa,

Machado

et al. 2023

Sci Rep

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Drastic changes in vegetation structure caused by exceeding ecological thresholds have fueled the interest in tropical forest responses to climate and land-use changes. Here, we examine the potential successional trajectories experienced by the largest dry tropical forest region in South America, driven by climate conditions and human disturbance. We built potential distribution models for vertebrate taxa associated with forest or shrub habitats to estimate natural vegetation cover. Distribution patterns were compared to current vegetation across the entire region to identify distinct forest degradation levels. Our results indicate the region has climatic and soil conditions suitable for more forest cover than is currently found, even in some areas with limited precipitation. However, 11.04% of natural cover persists across such an immense region, with only 4.34% consisting of forest cover. Forest degradation is characterized by the dramatic expansion of shrubland (390%), farming, and non-vegetation cover due to changes in land-use, rather than climatic conditions. Although different climate conditions have been the principal drivers for natural forest distribution in the region, the forest seems unable to resist the consequences of land-use changes, particularly in lower precipitation areas. Therefore, land-use change has exceeded the ecological thresholds for the persistence of forests, while climate change may exacerbate vegetation-type transitions.

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Section: Discussionmentioning

confidence: 99%

Human disturbance is the major driver of vegetation changes in the Caatinga dry forest region

Araujo,

Canassa,

Machado

et al. 2023

Sci Rep

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“…fire incidence and plant damage by cattle [62]). The recovery of stem density and biomass also depends on species' resprouting ability and other local factors such as land-use intensity, soil fertility, seed bank, invasive species, weeds, pathogens and herbivores [16,[63][64][65], among others [3,66]. Thus, forest cover appears to play a major role in determining propagule availability and thus the recovery rate of species richness, but disturbance regimes at the stand level are likely more important for stem density and plant biomass, independently of forest cover [67].…”

Section: Discussionmentioning

confidence: 99%

Landscape-scale forest cover drives the predictability of forest regeneration across the Neotropics

et al. 2023

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Abandonment of agricultural lands promotes the global expansion of secondary forests, which are critical for preserving biodiversity and ecosystem functions and services. Such roles largely depend, however, on two essential successional attributes, trajectory and recovery rate, which are expected to depend on landscape-scale forest cover in nonlinear ways. Using a multi-scale approach and a large vegetation dataset (843 plots, 3511 tree species) from 22 secondary forest chronosequences distributed across the Neotropics, we show that successional trajectories of woody plant species richness, stem density and basal area are less predictable in landscapes (4 km radius) with intermediate (40–60%) forest cover than in landscapes with high (greater than 60%) forest cover. This supports theory suggesting that high spatial and environmental heterogeneity in intermediately deforested landscapes can increase the variation of key ecological factors for forest recovery (e.g. seed dispersal and seedling recruitment), increasing the uncertainty of successional trajectories. Regarding the recovery rate, only species richness is positively related to forest cover in relatively small (1 km radius) landscapes. These findings highlight the importance of using a spatially explicit landscape approach in restoration initiatives and suggest that these initiatives can be more effective in more forested landscapes, especially if implemented across spatial extents of 1–4 km radius.

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“…Lastly, seed rain and soil seed bank floras were taxonomically compared to the woody flora (DBH ≥15 cm) from the 20 plots (i.e., local flora) and the landscape level as already mentioned. As intact seeds were not tested for viability, our figures represent the maximum recruitment potential supported by these two mechanisms of forest regeneration (see Trindade et al, 2020) as a substantial proportion of intact seeds can consist of unviable seeds (Bezerra et al, 2022).…”

Section: Seed Rain and Soil Seed Bank Of Woody Speciesmentioning

confidence: 99%

Açaí palm management disturbs seed rain and soil seed bank of an Amazonian estuarine forest

et al. 2023

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The exploitation of non‐timber forest products has been proposed as a sustainable way to exploit tropical forests, but such an opportunity remains to be proved. Here, we examine the impact of intensive açaí palm (Euterpe oleracea) management on the seed rain and soil seed bank in an estuarine forest landscape with a long history of forest management by locals in the Amazon region. Seed rain (100 80 cm2 collectors) and soil seed bank (100 30 cm2 samples) were monitored through a year across 20 forest stands, covering a gradient of açaí stem density (50–3575 açaí stems per ha). Seed rain and bank were dominated by açaí seeds (85.5%–85.8%) and by excluding them, seed rain and bank were low density and species poor, capturing a tiny subset from the local (17.91%–19.40%) and landscape woody flora (11.82%–14.55%). Moreover, autochthonous and vertebrated‐dispersed predominated as well as those from tree species considered useful by locals. Overall, açaí stem density positively affected açaí seed abundance in the seed rain and negatively affected seed pools in the bank in relation to abundance of seeds and vertebrated dispersed, while adult tree species richness and density and accessibility to forest stands were associated with more diversified seed pools. Thereby, forest stands are exposed to different levels of açaí management (high vs. low intensity) supported taxonomically distinct seed pools. Our results suggest that açaí intensification disturbs seed rain and soil seed bank with potential impacts on forest regeneration and the forest integrity standards required to consider açaí fruit production as sustainable according to current legislation.

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Drastic impoverishment of the soil seed bank in a tropical dry forest exposed to slash-and-burn agriculture

Cited by 25 publications

References 67 publications

Human disturbance is the major driver of vegetation changes in the Caatinga dry forest region

Human disturbance is the major driver of vegetation changes in the Caatinga dry forest region

Landscape-scale forest cover drives the predictability of forest regeneration across the Neotropics

Açaí palm management disturbs seed rain and soil seed bank of an Amazonian estuarine forest

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