Previous Land Use Alters the Effect of Climate Change and Facilitation on Expanding Woodlands of Spanish Juniper

Abstract

In Mediterranean-continental regions, changes in land use are leading to the expansion of valuable habitats like endemic Juniperus thurifera woodlands, but the impact of reduced rainfall, due to climate change, on this expansion remains uncertain. We assessed the early performance of J. thurifera in different global change scenarios with and without facilitation. Saplings were transplanted in three ecosystems types with different previous land use (woodlands, former agricultural fields, and former livestock pastures), microhabitats (open vs. understory of adult trees) and were subjected to two watering regimens. We characterized the abiotic environment and measured survival, growth and two ecophysiological parameters. Former livestock pastures were the least favorable ecosystem, where the nursing effect was greatest. Former agricultural fields had the highest survival, but were more sensitive than woodlands to water scarcity. Reduced rainfall decreased photochemical efficiency, particularly in the least favorable scenarios, but did not affect survival. Water use efficiency enhanced growth under the canopy, but not in the open, whereas photochemical efficiency enhanced growth and survival more in the open. Facilitation was critical for effective recruitment in the harshest scenarios: former livestock pastures and reduced rainfall. Comparison with previous studies suggests that establishment depends on infrequent wet episodes. In Mediterranean ecosystems, changes in land use and climate change are leading to woodland expansion due to the modulating effect of facilitation of the oncoming adverse drier conditions. Nevertheless, the positive effect of facilitation and the negative impact of aridity on tree recruitment are strongly influenced by previous land-use history.

Soil Respiration and Organic Carbon Dynamics with Grassland Conversions to Woodlands in Temperate China

“…Shifts in vegetation types may profoundly affect the dynamics of soil respiration and SOC by influencing soil microclimate and the production and transfer of aboveground photosynthate to belowground [23], [24], [25], [26], [27]. However, the direction of changes in the soil respiration and the consequent changes in organic carbon storage in soil within adjacent grass-woody vegetative transition is still controversial [28], [29], [30].…”

Spanish juniper gain expansion opportunities by counting on a functionally diverse dispersal assemblage community

“…Nowadays, the species is clearly benefitting from its diverse dispersal assemblage, given the spectacular transformation of old fields into NCA (Gimeno et al. ). The maintenance of diverse dispersal assemblages has been recently related to ecosystem resilience (Garcia and Martinez ), especially in cases where different dispersers provide a similar service to their interacting plant species.…”

Regional variation in stand structure and development in forests of Oregon, Washington, and inland Northern California

“…A mesofilter conservation approach aimed at conserving specific elements in managed forests (Hunter 2005) could enhance structural diversity and habitat function in managed forests. Other moderate biomass structural classes with lower density of live trees pertain to conservation issues v www.esajournals.org in drier forests where savannahs and woodlands around the world have gone through recent rapid structural change from either mortality (Allen and Breshears 1998, Williams et al 2010, Vila-Cabrera et al 2011 or expansion (Weltzin and McPherson 1999, Archer 2010, Gimeno et al 2012 with important consequences for ecosystem function (Sala and Maestre 2014) and biodiversity (Ratajczak et al 2012). Our results indicate that western juniper has experienced very little recent change related to mortality, but some woodland types with big trees and high densities of snags in the ponderosa pine, Douglas-fir, and grand fir/white fir vegetation zones are evidence of recent episodes of mortality that have affected anywhere from ;8-11 % of these vegetation zones.…”