Woody plant encroachment drives habitat loss for a relict population of a large mammalian herbivore in South America

Conservation programs alter herbivore stocking rates and find and protect the remaining areas that have not been plowed or converted to crops. Restoration is an ‘Acid Test’ for ecology. If we fully understand how grassland systems function and assemble after disturbance, then it should be easy to restore them after they have been degraded or destroyed. Alternatively, the idea that restorations will not be equivalent to remnants has been termed the ‘Humpty Dumpty’ hypothesis—once lost, it cannot be put back together again. Community assembly may follow rules, and if these rules are uncovered, then we may be able to accurately predict final species composition after assembly. Priority effects are sometimes found depending on species arrival orders, and they can result in alternate states. Woody plant encroachment is the increase in density and biomass of woody plants, and it is strongly affecting grassland C and water cycles.

Download Full-text

Differential effects of nutrient addition and woody plant encroachment on grassland soil, litter and plant dynamics across a precipitation gradient

Pedobiologia ◽

10.1016/j.pedobi.2021.150726 ◽

2021 ◽

Vol 85-86 ◽

pp. 150726

Author(s):

Tiffany Pillay ◽

David Ward ◽

Admore Mureva ◽

Michael Cramer

Keyword(s):

Woody Plant ◽

Nutrient Addition ◽

Precipitation Gradient ◽

Woody Plant Encroachment ◽

Grassland Soil ◽

Differential Effects ◽

Plant Dynamics

Download Full-text

Lowland tapir distribution and habitat loss in South America

10.7287/peerj.preprints.1579v1 ◽

2015 ◽

Author(s):

Jose Luis Passos Cordeiro ◽

José MV Fragoso ◽

Danielle Crawshaw ◽

Luiz Flamarion B Oliveira

Keyword(s):

South America ◽

Protected Areas ◽

Habitat Loss ◽

Habitat Suitability ◽

Distribution Patterns ◽

Distribution Models ◽

Potential Habitat ◽

Geographical Regions ◽

Suitability Maps ◽

Complex Relationships

The development of species distribution models (SDMs) can help conservation efforts by generating potential distributions and identifying areas of high environmental suitability for protection. Our study presents a rigorously derived distribution and habitat map for lowland tapir in South America. We also describe the potential habitat suitability of various geographical regions and habitat loss, inside and outside of protected areas network. Two different SDM approaches, MAXENT and ENFA, produced relative different Habitat Suitability Maps for the lowland tapir. While MAXENT was efficient at identifying areas as suitable or unsuitable, it was less efficient (when compared to the results by ENFA) at identifying the gradient of habitat suitability. MAXENT is a more multifaceted technique that establishes more complex relationships between dependent and independent variables. Our results demonstrate that for at least one species, the lowland tapir, the use of a simple consensual approach (average of ENFA and MAXENT models outputs) better reflected its current distribution patterns. The Brazilian ecoregions have the highest habitat loss for the tapir. Cerrado and Atlantic Forest account for nearly half (48.19%) of the total area lost. The Amazon region contains the largest area under protection, and the most extensive remaining habitat for the tapir, but also showed high levels of habitat loss outside protected areas, which increases the importance of support for proper management.

Download Full-text

Structural, physiognomic and aboveground biomass variation in savanna-forest transition zones on three continents. How different are co-occurring savanna and forest formations?

Biogeosciences Discussions ◽

10.5194/bgd-11-4591-2014 ◽

2014 ◽

Vol 11 (3) ◽

pp. 4591-4636 ◽

Cited By ~ 8

Author(s):

E. M. Veenendaal ◽

M. Torello-Raventos ◽

T. R. Feldpausch ◽

T. F. Domingues ◽

F. Gerard ◽

...

Keyword(s):

South America ◽

Woody Plant ◽

Canopy Cover ◽

Woody Vegetation ◽

Canopy Closure ◽

Forest Transition ◽

Vegetation Types ◽

Forest Species ◽

Stable States ◽

Transition Zones

Abstract. Through interpretations of remote sensing data and/or theoretical propositions, the idea that forest and savanna represent "alternative stable states" is gaining increasing acceptance. Filling an observational gap, we present detailed stratified floristic and structural analyses for forest and savanna stands mostly located within zones of transition (where both vegetation types occur in close proximity) in Africa, South America and Australia. Woody plant leaf area index variation was related in a similar way to tree canopy cover for both savanna and forest with substantial overlap between the two vegetation types. As total woody plant canopy cover increased, so did the contribution of middle and lower strata of woody vegetation to this total. Herbaceous layer cover also declined as woody cover increased. This pattern of understorey grasses and herbs being progressively replaced by shrubs as canopy closure occurs was found for both savanna and forests and on all continents. Thus, once subordinate woody canopy layers are taken into account, a less marked transition in woody plant cover across the savanna-forest species discontinuum is observed compared to that implied when trees of a basal diameter > 0.1m are considered in isolation. This is especially the case for shrub-dominated savannas and in taller savannas approaching canopy closure. An increased contribution of forest species to the total subordinate cover is also observed as savanna stand canopy closure occurs. Despite similarities in canopy cover characteristics, woody vegetation in Africa and Australia attained greater heights and stored a greater concentration of above ground biomass than in South America. Up to three times as much aboveground biomass is stored in forests compared to savannas under equivalent climatic conditions. Savanna/forest transition zones were also found to typically occur at higher precipitation regimes for South America than for Africa. Nevertheless, coexistence was found to be confined to a well-defined edaphic/climate envelope consistent across all three continents with both soil and climate playing a role as the key determinants of the relative location of forest and savanna. Taken together these observations do not lend support the notion of alternate stable states mediated through fire-feedbacks as the prime force shaping the distribution of the two dominant vegetation types of the tropical lands.

Download Full-text