Research NoteVolume–biomass functions reveal the effect of browsing on three Moroccan dwarf shrubs

We studied the effects of browsing on the plant architecture and volume-biomass relationships of three dominant dwarf shrubs – Artemisia herba-alba, A. mesatlantica and Teucrium mideltense – in a sagebrush steppe in the Central High Atlas Mountains, southern Morocco. For this purpose, we developed power-law volume-biomass functions based on nonlinear regressions for each of these species, under both browsed and unbrowsed conditions. These functions were then applied to individual-based annual monitoring data from inside and outside a browsing exclosure to calculate standing biomass for each of the years from 2004 to 2009. The biomass of the three species was well predicted by the allometric functions, and different functions for the browsed and unbrowsed conditions reflected changes in plant architecture. Browsing had a significant negative impact on biomass for A. herba-alba but not for A. mesatlantica, whereas its effects on T. mideltense were inconsistent between years. The fact that the latter two species hardly benefited from browsing exclusion might be because of increased competition from the more dominant A. herba-alba. During the study period, the standing biomass increased whether or not there was browsing, which might be because of the recovery of the shrubs after a preceding severe drought. Further studies are needed in order to investigate the generality of the findings.Keywords: allometric function, Atlas Mountains, nonlinear regression, permanent plot, plant architecture, standing biomassAfrican Journal of Range & Forage Science 2012, 29(1): 31–3

Transhumance, livestock mobility and mutual benefits between crop and livestock production

Grazing-based livestock production, named pastoralism, is classified into nomadism, transhumance and agro-pastoralism. Transhumance is characterised by the seasonal and recurring movement of livestock whereby seasonal grazing areas and routes for livestock movement are fixed. All grazing based livestock production systems including transhumance are constrained globally for a variety of reasons. The major threats to the system are globalisation, nationalisation or privatisation of rangelands, national parks and community forestry policies restricting free grazing and shortage of labour. The collapse or decline of such social-ecological systems (SESs), which have existed for over 1000s years, often induces adverse impacts on societies and ecosystems. Here we review the literature on transhumance, and discuss reasons for transhumance, and the associated advantages and disadvantages of livestock movement in transhumance. Our review also focuses on how the integration of crop and livestock production in transhumance derives mutual benefits. The review indicates that the seasonal movement of livestock is an ecological necessity in areas with harsh climates and low pasture production. Transhumance is also a herders’ adaptive management to adjust to variable grazing resources and environmental conditions. The disadvantages of seasonal movement of livestock such as greater herding labour required and expenditure of more energy for livestock, are far outweighed by the ecological advantages. Some of these are: to minimise grazing competition and to protect rangeland pastures from being overgrazed. Our review also indicates that the integration of crop and livestock production derives mutual benefits and contributes for their enhanced sustainability