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Please cite this article as: Amat, B., Cortina, J., Zubcoff, J.J.,Community attributes determine facilitation potential in a semi-arid steppe., Perspectives in Plant Ecology, Evolution and Systematics (2014), http://dx.doi.org/10.1016/j.ppees. 2014.10.001 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. interactions. Conversely, the interaction with other co-occurring species has scarcely been addressed, despite the fact that the entire community may affect plant performance. We used woody vegetation patches as models to evaluate community facilitation in semi-arid steppes. 5We characterized biotic and physical attributes of 53 woody patches (patch size, litter accumulation, canopy density, vegetation cover, species number and identity, and phylogenetic distance), and soil fertility (organic C and total N), and evaluated their relative importance for the performance of seedlings of Pistacia lentiscus, a keystone woody species in western Mediterranean steppes. Seedlings were planted underneath the patches, and on 10 their northern and southern edges. Woody patches positively affected seedling survival but not seedling growth. Soil fertility was higher underneath the patches than elsewhere. Physical and biotic attributes of woody patches affected seedling survival, but these effects depended on microsite conditions. The composition of the community of small shrubs and perennial grasses growing underneath the patches controlled seedling performance. An increase in Stipa 15 tenacissima and a decrease in Brachypodium retusum increased the probability of survival.The cover of these species and other small shrubs, litter depth and community phylogenetic distance, were also related to seedling survival. Seedlings planted on the northern edge of the patches were mostly affected by attributes of the biotic community. These traits were of lesser importance in seedlings planted underneath and in the southern edge of patches, suggesting 20 that constraints to seedling establishment differed within the patches. Our study highlights the importance of taking into consideration community attributes over pair-wise interactions when evaluating the outcome of ecological interactions in multi-specific communities, as they

Highlights• Shrub cover has increased in former agricultural lands worldwide.• Colonization rates are explained by the identity of shrub species.• Species idiosyncratic effects are contingent on water availability.• Abiotic attributes, such as aspect or rock cover, played a lesser role. 1 AbstractThe increase in shrub cover and density is a widespread phenomenon in drylands worldwide. Its causes and consequences are complex and strongly idiosyncratic. Detailed knowledge of the rate of shrub colonization, and its abiotic and biotic drivers is crucial to fully understand and manage these areas. We used a set of aerial photographs (1956, 1978, 1985, 1998 and 2009) describing early, gradual and late recruitment, respectively. Differences in shrub patch colonization rate were related to the identity of patch-forming species, but contingent on water availability. Total increases in shrub patch density were larger when patches were dominated by late colonizer species. Overall shrub patch dynamics was mostly related to the identity of patchforming species and climatic conditions, and to a lesser extent physical factors such as aspect and rock cover. Given the sensitivity of patch-forming species to climatic conditions, new challenges for steppe management will emerge over the next decades. Species able to thrive under harsh conditions may increase their dominance at the expense of species adapted to less demanding conditions.

19The impact of woody vegetation patches on soil dissolved organic matter (DOM) in a 20 semi-arid steppe was studied. DOM from forty-two patch and inter-patch soil samples,

17Aims 18 The objective of this paper was to develop a method based on infrared spectroscopy to 19 compare mineral content in soils and apply it to evaluate soil mineralogical variations in 20 pairs of inter-patch and patch soils in a semi-arid area. 21 Methods 22Mixtures of several minerals were analyzed by infrared spectroscopy, the second 23 derivative of the spectra was calculated and the spectra normalized respect to calcite or 24 quartz signals (711cm -1 or 800 cm -1 respectively). The intensities of representative 25 signals of each mineral were related to their concentration in the mixtures. Pairs of 26 patch and inter-patch soils from five different sites were analyzed by this method. 27Elemental analysis and total lime analysis were performed in some soil pairs. 28 Results 29Soils were dominated by calcite and quartz, or by montmorillonite and kaolinite. Inter-30 patch soils were richer in calcite and poorer in quartz or clays than patch soils. Calcite 31 losses in patch soils might be related to soil acidification by CO2 from respiration and/or 32 organic matter. Elemental analysis showed high values of S, Cl, and K in patch soils 33 with respect to inter-patch soils. 34 Conclusions 35The proposed FTIR method was useful to compare soil mineralogy in specific areas. 36Fertile spots by accumulation of water, soluble salts and sediments may favor plant 37 growth in semi-arid regions and these plants may increase the fertility of the spot. 38Changes in soil mineral composition could be used to monitor the biological activity of 39 soil in arid and semi-arid zones 40