scholarly journals Interactive effects of grazing and drought on desert rangelands of Tunisia

Biologija ◽  
2016 ◽  
Vol 62 (2) ◽  
Author(s):  
Mouldi Gamoun ◽  
Bouajila Essifi ◽  
Chris Dickens ◽  
Belgacem Hanchi
Keyword(s):  
Species Richness ◽  
Vegetation Change ◽  
Interactive Effects ◽  
Climatic Variations ◽  
Heavy Grazing ◽  
Desert Rangelands ◽  
Desert Areas ◽  
Desert Regions ◽  
Arid Rangelands ◽  
Restoration Failure

Arid rangelands worldwide regularly confront drought and overgrazing. Land degradation is mostly apparent in desert rangelands, where drought events are important and grazing influences and intrinsic vegetation change act intermittently. The objectives of this study were to determine the effects of grazing and drought stress on diversity, species richness and primary production in desert rangeland of southern Tunisia. This assessment was conducted in March 2008 (wet year) and March 2009 (dry year) both on grazed and ungrazed sites. Diversity, species richness and biomass production exhibited bigger variation between years than among sites within two years. Although protection from grazing could slightly increase rangeland production in favorable years, the additive effects of heavy grazing and drought could result in restoration failure. This study suggests that climatic variations, particularly droughts, control major trends in plant species composition, diversity and biomass. Under grazing, plants of desert regions are able to respond very rapidly to small drought. The latter is the most debilitating risk in desert areas.

scholarly journals Vegetation change at high elevation: scale dependence and interactive effects on Niwot Ridge

2015 ◽  
Vol 8 (5-6) ◽  
pp. 713-725 ◽  
Author(s):  
Katharine N. Suding ◽  
Emily C. Farrer ◽  
Andrew J. King ◽  
Lara Kueppers ◽  
Marko J. Spasojevic
Keyword(s):  
Vegetation Change ◽  
High Elevation ◽  
Scale Dependence ◽  
Interactive Effects ◽  
Niwot Ridge

Effects of Vegetation Change on Ant Communities of Arid Rangelands

1981 ◽  
Vol 10 (6) ◽  
pp. 893-897 ◽  
Author(s):  
Wendy A. Wisdom ◽  
Walter G. Whitford
Keyword(s):  
Vegetation Change ◽  
Ant Communities ◽  
Arid Rangelands

Vegetation change in an urban grassy woodland 1974 - 2000

2004 ◽  
Vol 52 (5) ◽  
pp. 597 ◽  
Author(s):  
J. B. Kirkpatrick
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Exotic Species ◽  
Native Species ◽  
Vegetation Change ◽  
Structural Changes ◽  
Linear Models ◽  
Tree Cover ◽  
Native Plant ◽  
Native Species Richness

Few temporal studies document vegetation change in Australian temperate grassy woodlands. Floristic and structural data were collected from 68 randomly located sites in the Queens Domain, an urban grassy woodland remnant, in 1974, 1984, 1994 and 2000 and a search made for rare species. Species of conservation significance were concentrated at highly disturbed sites, whereas vegetation types of conservation significance decreased in area as a result of increases in the numbers of Allocasuarina verticillata, which caused a change in many unmown areas from Eucalyptus viminalis grassy woodland to E. viminalis–A. verticillata woodland/forest or A. verticillata open/closed forest. Structural changes were associated with changes in species composition and an increase in native-species richness. Increases in tree cover occurred where fires were most frequent, possibly as a result of the lack of mammalian herbivores. The frequencies of herbs and annual grasses were strongly affected by precipitation in the month of sampling. Half of the species that showed a consistent rise or fall through time were woody plants, approximately twice the number expected. In the dataset as a whole, species-richness variables were largely explained by varying combinations of variables related to moisture availability, altitude and the incidence of mowing. The strongest influences on species composition were the same, although slope and time since the last fire also contributed to multiple regression and generalised linear models. Compositional stability was positively related to native-species richness, whereas high levels of exotic-species richness occurred at both low and high levels of native-species richness. The maintenance of native-plant biodiversity on the Domain requires such counterintuitive measures as the maintenance of exotic trees and the control of native trees, demonstrating the contingencies of conservation management in fragmented vegetation that consists of a mixture of native and exotic species.

scholarly journals Vegetation change in variable rangeland environments: the relative contribution of drought and soil type in arid rangelands

2013 ◽  
Vol 32 (1) ◽  
Author(s):  
Mouldi Gamoun
Keyword(s):  
Soil Type ◽  
Vegetation Change ◽  
Rainfall Variability ◽  
Grazing Pressure ◽  
Ecosystem Structure ◽  
Functional Responses ◽  
Relative Contribution ◽  
Arid Rangelands ◽  
And Function ◽  
Ecosystem Structure And Function

AbstractThe response of a plant community to protection from grazing, as a function of year and soil type, was studied in the arid rangelands of southern Tunisia between 2007 and 2009. The vegetation of rangelands is often altered under grazing pressure, but unfortunately, removing the grazing pressure often does not reverse the changes in the way the succession model predicts. Rainfall variability is a key driver of ecosystem structure and function in arid rangelands, and this arid area of North Africa is characterized by low and erratic rainfall and is prone to drought conditions which normally occur every two to three years.Steppes are likely to exhibit strong and rapid structural and functional responses to these altered rainfall patterns. Although drought affects vegetation cover more in loamy soil than in all other soils, it affects diversity on all soils; particularly limestone and loam soils

scholarly journals Climate modifies response of non-native and native species richness to nutrient enrichment

2016 ◽  
Vol 371 (1694) ◽  
pp. 20150273 ◽  
Author(s):  
Habacuc Flores-Moreno ◽  
Peter B. Reich ◽  
Eric M. Lind ◽  
Lauren L. Sullivan ◽  
Eric W. Seabloom ◽  
...  
Keyword(s):  
Species Richness ◽  
Nutrient Enrichment ◽  
Time Scale ◽  
Native Species ◽  
Niche Partitioning ◽  
Climatic Conditions ◽  
Nutrient Addition ◽  
Interactive Effects ◽  
Native Plant ◽  
Native Species Richness

Ecosystem eutrophication often increases domination by non-natives and causes displacement of native taxa. However, variation in environmental conditions may affect the outcome of interactions between native and non-native taxa in environments where nutrient supply is elevated. We examined the interactive effects of eutrophication, climate variability and climate average conditions on the success of native and non-native plant species using experimental nutrient manipulations replicated at 32 grassland sites on four continents. We hypothesized that effects of nutrient addition would be greatest where climate was stable and benign, owing to reduced niche partitioning. We found that the abundance of non-native species increased with nutrient addition independent of climate; however, nutrient addition increased non-native species richness and decreased native species richness, with these effects dampened in warmer or wetter sites. Eutrophication also altered the time scale in which grassland invasion responded to climate, decreasing the importance of long-term climate and increasing that of annual climate. Thus, climatic conditions mediate the responses of native and non-native flora to nutrient enrichment. Our results suggest that the negative effect of nutrient addition on native abundance is decoupled from its effect on richness, and reduces the time scale of the links between climate and compositional change.

scholarly journals ENSO and IOD teleconnections for African ecosystems: evidence of destructive interference between climate oscillations

2011 ◽  
Vol 8 (1) ◽  
pp. 27-40 ◽  
Author(s):  
C. A. Williams ◽  
N. P. Hanan
Keyword(s):  
El Niño ◽  
Land Surface ◽  
Vegetation Change ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Interactive Effects ◽  
Surface Model ◽  
Destructive Interference ◽  
Climate Oscillations

Abstract. Rainfall and vegetation across Africa are known to resonate with the coupled ocean-atmosphere phenomena of El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). However, the regional-scale implications of sea surface temperature variability for Africa's photosyntheis have received little focused attention, particularly in the case of IOD. Furthermore, studies exploring the interactive effects of ENSO and IOD when coincident are lacking. This analysis uses remotely sensed vegetation change plus a land surface model driven with observed meteorology to investigate how rainfall, vegetation, and photosynthesis across Africa respond to these climate oscillations. In addition to the relatively well-known ENSO forcing, the IOD induces large departures of photosynthesis across much of Africa associated with anomalies in rainfall and vegetation greenness. More importantly, sizeable independent effects can be suppressed or even reversed by destructive interferences during periods of simultaneous ENSO and IOD activity. For example, effects of positive IOD on southeastern Africa tended to dominate those of El Niño during their coincidence spanning 1997–1998, with sign reversal of El Niño's typically strong suppression of photosynthesis in this region. These findings call into question past analyses examining teleconnections to ENSO or IOD in isolation, and indicate the need to consider their simultaneous states when examining influences on hydroclimatic and ecological conditions across Africa.

scholarly journals ENSO and IOD teleconnections for African ecosystems: evidence of destructive interference between climate oscillations

2010 ◽  
Vol 7 (4) ◽  
pp. 6323-6352
Author(s):  
C. A. Williams ◽  
N. P. Hanan
Keyword(s):  
El Niño ◽  
Land Surface ◽  
Vegetation Change ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Interactive Effects ◽  
Surface Model ◽  
Destructive Interference ◽  
Climate Oscillations

Abstract. Rainfall and vegetation across Africa are known to resonate with the coupled ocean-atmosphere phenomena of El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). However, the regional-scale implications of sea surface temperature variability for Africa's carbon sources and sinks have received little focused attention, particularly in the case of IOD. Furthermore, studies exploring the interactive effects of ENSO and IOD when coincident are lacking. This analysis uses remotely sensed vegetation change plus a land surface model driven with observed meteorology to investigate how rainfall, vegetation, and photosynthesis across Africa respond to these climate oscillations. In addition to the relatively well-known ENSO forcing, the IOD induces large departures of photosynthesis across much of Africa associated with anomalies in rainfall and vegetation greenness. More importantly, sizeable independent effects can be suppressed or even reversed by destructive interferences during periods of simultaneous ENSO and IOD activity. For example, effects of positive IOD on southeastern Africa tended to dominate those of El Niño during their coincidence spanning 1997–1998, with sign reversal of El Niño's typically strong suppression of photosynthesis in this region. These findings call into question past analyses examining teleconnections to ENSO or IOD in isolation, and indicate the need to consider their simultaneous states when examining influences on hydroclimatic and ecological conditions across Africa.

scholarly journals Climate Change Affects Vegetation Differently on Siliceous and Calcareous Summits of the European Alps

2021 ◽  
Vol 9 ◽  
Author(s):  
Lena Nicklas ◽  
Janette Walde ◽  
Sonja Wipf ◽  
Andrea Lamprecht ◽  
Martin Mallaun ◽  
...  
Keyword(s):  
Climate Change ◽  
Species Richness ◽  
Vegetation Change ◽  
Vascular Plant ◽  
Plant Cover ◽  
Permanent Plots ◽  
European Alps ◽  
Climate Data ◽  
Elevation Gradients ◽  
Over Time

The alpine life zone is expected to undergo major changes with ongoing climate change. While an increase of plant species richness on mountain summits has generally been found, competitive displacement may result in the long term. Here, we explore how species richness and surface cover types (vascular plants, litter, bare ground, scree and rock) changed over time on different bedrocks on summits of the European Alps. We focus on how species richness and turnover (new and lost species) depended on the density of existing vegetation, namely vascular plant cover. We analyzed permanent plots (1 m × 1 m) in each cardinal direction on 24 summits (24 × 4 × 4), with always four summits distributed along elevation gradients in each of six regions (three siliceous, three calcareous) across the European Alps. Mean summer temperatures derived from downscaled climate data increased synchronously over the past 30 years in all six regions. During the investigated 14 years, vascular plant cover decreased on siliceous bedrock, coupled with an increase in litter, and it marginally increased on higher calcareous summits. Species richness showed a unimodal relationship with vascular plant cover. Richness increased over time on siliceous bedrock but slightly decreased on calcareous bedrock due to losses in plots with high plant cover. Our analyses suggest contrasting and complex processes on siliceous versus calcareous summits in the European Alps. The unimodal richness-cover relationship and species losses at high plant cover suggest competition as a driver for vegetation change on alpine summits.

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