The differential influences of human‐induced disturbances on tree regeneration community: a landscape approach

Abstract

Abstract. Understanding the processes shaping biological communities under interacting disturbances is a core challenge in ecology. Although the impacts of human-induced disturbances on forest ecosystems have been extensively studied, less attention has been paid to understanding how tree regeneration at the community level responds to such disturbances. Moreover, these previous studies have not considered how these effects change according to major social and environmental factors that can influence forest use at a landscape scale. In this study, we investigate the effects of cattle grazing and selective logging on the composition of tree regeneration communities in relation to forest successional stage and land tenure regime in Chilean temperate forests, a global biodiversity hotspot. We recorded seedlings, saplings and basal area of stumps of tree species (as a surrogate for selective logging), and number of cattle dung pats (as a surrogate for cattle pressure) in 129 25 3 20 m plots in small (,200 ha) and large properties in different successional stages (old-growth, intermediate, secondary forests). The regeneration of the ten more abundant species as predicted by human disturbance, land tenure, forest successional stage, and number of parent trees was modelled using generalised linear models. Predictions for each individual model were made under different scenarios of human disturbance. The predicted regeneration results were assembled and subjected to ordination analyses and permutation multivariate analyses of variance to determine differences in regeneration composition under each scenario. In most cases, best-fit models contained at least one of the explanatory variables accounting for human disturbance. The effects of selective logging on tree regeneration varied depending on land tenure regime, but cattle grazing always exhibited a negative effect. Our results revealed that cattle have a more negative effect on forest regeneration than selective logging, especially in old-growth forests and small properties. Our analytical approach contributes to the understanding of the differential influence of human-induced disturbances on the tree regeneration community at a landscape scale. It can inform conservation policies and actions, which should focus on addressing the main disturbance factors and on developing strategies to conserve the most sensitive species to such disturbances.

Tree Component Demography in an Upper Montane Mixed Ombrophilous Forest Under Chronic Anthropogenic Disturbances

“…Results obtained here thus reinforce the idea that chronic anthropic disturbances potentially influence both species richness -as once noted by Lôbo et al (2011) -, which favors the process of biological homogenization, and the successional trajectory of forests, by either limiting or slowing down the process of ecological succession (Clark and Covey, 2012;Zamorano-Elgueta et al, 2014;ArroyoRodríguez et al, 2015). In long term, a floristically more homogeneous forest is thus expected, consisting mainly of functional groups (light-demanding climax) and species (e.g.…”

“…Some authors have observed these patterns in forest remnants subject to cattle presence and selective logging in Minas Gerais, Brazil (Machado and Oliveira Filho, 2010); in a transition forest between the Brazilian Cerrado and the Amazon, suggesting the influence of a strong drought as a determining factor (Mews et al, 2011); and in alluvial forest remnants subject to anthropic disturbances, after a heavy flood in the south of Minas Gerais, Brazil (Silva et al, 2011). Moreover, studies carried out in transformed landscapes have shown that disturbances caused by selective logging without planning and/or cattle grazing have negatively influenced richness by favoring pioneer species rather than late ones and therefore either slowing the process of succession down or limiting it (Clark and Covey, 2012;Zamorano-Elgueta et al, 2014;Arroyo Rodríguez et al, 2015). However, the ecological value of cultural landscapes traditionally managed by rural populations should not be ignored due to the fact that many tree species are able to remain in such places (Mello and Peroni, 2015) and that these areas can perform more ecosystem functions than those exclusively used for agrosilvopastoral purposes.…”

<b>Indicators of land use by cattle: associations among methods and role of environmental factors

“…The expansion of livestock production areas and the resulting occupation of natural and semi-natural areas have raised local concerns about the conservation of these ecosystems (Carvalho & Batello, 2009;Zamorano-Elgueta et al, 2014), even though the impact of livestock on those environments has been shown to be complex.…”

“…For example, it is usually expected that cattle presence in natural areas increases the risk of soil erosion, water pollution and loss of biodiversity (Carvalho & Batello, 2009;Hirata et al, 2009;Zamorano-Elgueta et al, 2014). However, livestock grazing may also have positive effects on natural and semi-natural grasslands, being beneficial for plant species richness (Putfarken, Dengler, Lehmann Härdtle, 2008) and reducing the risk of wildfires (Davies, Boyd, Bates, & Hulet, 2015).…”

La silvicultura como herramienta para la restauración de bosques templados

“…a bosques nativos o mixtos (cuadro 1). Es importante señalar que en todos los casos anteriores, nada funcionará, si el agente de degradación no es eliminado del sistema, como sucede por ejemplo con el ganado dentro del bosque (Zamorano et al 2014). En resumen, en las cuatro situaciones señaladas se requerirá de modo fundamental aplicar múltiples estrategias y técnicas silviculturales para restaurar los bosques nativos.…”