Cattle foraging in Mediterranean oak woodlands – Effects of management practices on the woody vegetation
Introduction
Sustainable utilization of woodlands presents a major challenge worldwide. Mediterranean evergreen oak woodlands have been exploited since historical times for foraging by domestic herbivores, mostly goats (Papanastasis, 2009, Perevolotsky and Seligman, 1998). Browsing has shaped an open structure of the woody vegetation, and contributed to its maintenance, resulting in a more heterogeneous landscape with higher biodiversity (Casasus et al., 2007, Henkin, 2011). In recent decades, however, woodlands worldwide, including those around the Mediterranean Basin, are undergoing extensive land-use transition, which causes large-scale changes in the structure and composition of the vegetation (Lopez-Sanchez et al., 2014, Plieninger et al., 2011, Underwood et al., 2009). In the Mediterranean region, these changes are mainly due to decreases in wood-cutting for firewood and charcoal, and to traditional foraging by goats, which have led to a more closed and spatially homogeneous woody-vegetation structure, thus reducing plant diversity and increasing the risk of fire due to accumulation of inflammable material (Bartolome et al., 2011, Carmel and Kadmon, 1999, Henkin, 2011, Perevolotsky and Seligman, 1998). In parallel, the increasing demand for cattle meat in the region has been constrained by the limited availability of herbaceous rangelands for cattle grazing. This current situation has spurred interest in using Mediterranean woodlands for cattle foraging.
In recent years, traditional goat herding which contributed effectively in shaping oak woodlands have been replaced by cattle herds with the aim of increasing beef production (Bashan and Bar-Massada, 2017, Casasus et al., 2007, Henkin, 2011). However, unlike goats which are adapted to browsing in Mediterranean woodlands, the woody vegetation is considered unsuitable for cattle because of its poor nutritional quality, partly caused by its high tannin content (Papachristou et al., 2005, Perevolotsky et al., 1993). Nevertheless, field observations of cattle foraging in oak woodlands showed that, in addition to herbaceous vegetation, the animals consumed tree foliage and young twigs, as well as oak acorns during fall (October–December) (Bartolome et al., 2011, Brosh et al., 2006). Moreover, a detailed study of diet composition and energy balance of beef cattle foraging in Mediterranean woodland, with moderate supplemental feed during the dry season, showed that their performance was comparable with that of cattle grazing in grasslands in the same region (Brosh et al., 2006, Henkin et al., 2005). However, the low accessibility of the closed woody vegetation to cattle, together with poor productivity of the herbaceous understory vegetation and the generally difficult topographic conditions in woodland areas, make their use for cattle more problematic and less attractive. Moreover, the relationships between cattle foraging intensity and the spatial heterogeneity of the woody vegetation have not been assessed quantitatively. A better understanding of the way cattle consume woody vegetation should contribute to more efficient use and management of Mediterranean woodlands.
Domestic herbivores vary in their impact on the vegetation, depending on factors related to: (i) animals' characteristics, such as eating technique, food preferences and body size (Arnold, 1981, Rook and Tallowin, 2003), (ii) vegetation structure and composition, nutritional quality, and anti-herbivory defenses (Marquardt et al., 2009, Marquardt et al., 2010, Provenza, 1995), and (iii) environmental factors, including seasonal conditions and topography (Delcurto et al., 2005, Guevara et al., 1996). These factors have major impacts on the spatial distribution of cattle foraging in the woodland (Schoenbaum et al., 2017) and on the dietary choices of the animals; thus they influence plant growth, sapling establishment, vegetation structure and diversity (Arnold, 1981, Perevolotsky and Seligman, 1998). Livestock can affect woody species by browsing, trampling, fertilizing with excreta, or grazing the herbage and modifying competitive relationships between herbaceous and woody vegetation (McEvoy et al., 2006, Papachristou and Platis, 2011). High foraging intensity, beyond the carrying capacity of the woodland, might damage the woody vegetation, thereby negatively affecting species richness and vegetation composition (Chaideftou et al., 2011, Gill, 1992). Moreover, recruitment failure might threaten the continuity and sustainability of the woodland (Dufour-Dror, 2007, Plieninger et al., 2011, Tyler et al., 2008). Thus, foraging intensity should be adjusted to the availability of tree and shrub species that are of high preference for the cattle, while remaining low enough to allow woodland regeneration, in order to prevent large changes in vegetation composition (Evlagon et al., 2010, Marquardt et al., 2009). Furthermore, appropriate management of the woodland is required to provide other ecological services such as biodiversity conservation, recreation, and landscape diversity, in addition to animal production. Thus, there is an urgent need for better understanding of the impact of cattle foraging on Mediterranean woodlands – which will enable land managers to choose a suitable management strategy for improving cattle performance while minimizing damage to the vegetation; thereby, conflicts between conservation and cattle herding interests should be mitigated.
Thus, the main goal of our present study was to provide essential information on the responses of woody vegetation to cattle foraging in Mediterranean oak woodlands, and on the factors affecting spatial patterns of woodland utilization. Mediterranean oak woodlands are characterized by a complex multilayered structure and consist of a mosaic of various vegetation types, ranging from dense woodland to garrigue formations with low tree densities (Papanastasis, 2009). Cattle that forage in these vegetation formations spend much of their time in woody ranges that provide both food and shade, particularly during the dry season in summer and early fall, when the woody vegetation provides most of the available forage (Schoenbaum et al., 2017). Therefore, in the present study we focused on the impact of cattle foraging on the woody components of both the dense and the open woodland formations. Specific objectives were: 1) to quantify changes in the structure, composition, and regeneration potential of different types of woody vegetation, in response to two animal population densities; 2) to assess the main factors affecting the way cattle utilize the woody vegetation; and 3) to assess the suitability of foraging management for improving both the use and conservation of Mediterranean woodlands.
Section snippets
Study area
The research was conducted during 2007–2011 at the Hatal Experimental Farm in Western Galilee, Israel (long. 35°15′, lat. 33°01′), described in detail by Henkin et al. (2005). The site is 400–500 m a.s.l. and comprises moderate to steep slopes of up to 40°. Limestone and dolomite rocks form 15–40% of the surface cover; they are interspersed with pockets of terra rossa soil, up to 40 cm in depth. The climate is typically Mediterranean, with mild winters and hot, dry summers. The long-term
Vegetation structure prior to the onset of cattle foraging
Variations in cover and surface contour of the woody vegetation among the transects showed clear differences in vegetation structure between the dense and open woodland types at the commencement of the experiment, before the cattle were introduced into the paddocks (Figs. 1a and 2a). However, no significant differences in vegetation structure were found between the paddocks allocated for high and moderate cattle density treatments (P < 0.05). At the start of the experiment the dense woodland
Vegetation characteristics of dense and open oak woodland
In Western Galilee, the dense oak woodland, with its closed canopy is characterized by higher abundance of shade-tolerant species, such as L. nobilis and R. aculeatus, whereas heliophilic species as S. spinosum, C. villosa and Cistus species thrived in the open woodland and particularly in the garrigue. Climbers, such as Smilax aspera L., Asparagus aphillus L., and Rubia tenuifolia Dum.-Urville, which are tolerant of shade and browsing, are more common in the dense woodland. This spatial
Conclusions and management implication
The present quantitative analysis of changes in woodland vegetation has shown that four consecutive seasons of animal population densities of 0.33 and 0.55 cow⋅ha−1 resulted in relatively high biomass removal, especially under high animal density. However these foraging densities had no large negative effects on woody species richness or regeneration potential from saplings, compared with the initial state of the woodland vegetation, which previously had been subjected to sparse, sporadic
Acknowledgements
The authors thank the herd owners, Yigal and Chaim Haike, for their exceptional cooperation in conducting this study. The study was funded by grants from the Israel Rangeland Advisory Board, Northern R&D, and the Jewish National Fund.
Conflict of interest
The authors declare that they have no conflict of interest.
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